Difference between revisions of "Sea level rise"

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[[File:6m Sea Level Rise.jpg|thumb|600px|Map of the Earth with a six-meter sea level rise represented in red]].
[[File:6m Sea Level Rise.jpg|thumb|300px|Map of the Earth with a six-meter sea level rise represented in red]].
In the United States significant amounts of residential and commercial property lie in the path of predictable sea level rise, particularly in Boston and south Florida. Estimates of the amount of sea level rise by the turn of the 22nd Century range between 2 and 6 feet.
Sea level is the most concrete and undeniable consequence of [[global warming]]. In the United States significant amounts of residential and commercial property lie in the path of predictable sea level rise, particularly in Boston and south Florida. Estimates of the amount of sea level rise by the turn of the 22nd Century range between 2 and 6 feet. The major cause of uncertainty in future projections is doubt about the amount of water which will result from melting of ice sheets.<ref>[https://www.pnas.org/content/early/2019/05/14/1817205116 "Ice sheet contributions to future sea-level rise from structured expert judgment"]</ref> In other parts of the word there are large densely-populated [[delta]]s which will be profoundly affected. Globally, dramatic effects have occurred in [[Venice]] and can be expected on the coast of [[Bangladesh]]
'''[[Sea level]] rise''' refers to an increase in the volume of water in the world’s oceans, resulting in an increase in global [[mean sea level]].  Sea level rise is usually attributed to [[global climate change]] by [[thermal expansion]] of the water in the oceans and by melting of [[Ice sheet]]s and  [[glacier]]s on land.   Melting of floating [[ice shelf|ice shelves]] or [[icebergs]] at sea raises sea levels only slightly.
'''[[Sea level]] rise''' refers to an increase in the volume of water in the world’s oceans, resulting in an increase in global mean sea level.  Sea level rise is usually attributed to [[global climate change]] by [[thermal expansion]] of the water in the oceans and by melting of [[Ice sheet]]s and  [[glacier]]s on land. Melting of floating [[ice shelf|ice shelves]] or [[icebergs]] at sea raises sea levels only slightly.
Sea level rise at specific locations may be more or less than the global average. Local factors might include [[tectonic]] effects, [[subsidence]] of the land, tides, currents, storms, etc.<ref name=wg2-4-4-9>
Sea level rise at specific locations may be more or less than the global average. Local factors might include [[tectonic]] effects, [[subsidence]] of the land, tides, currents, storms, etc. Sea level rise is expected to continue for centuries. Because of the slow [[climate inertia|inertia]], long response time for parts of the climate system, it has been estimated that we are already committed to a sea-level rise of approximately 2.3 |ft for each degree [[Celsius]] of temperature rise within the next 2,000 years.<ref>http://www.pnas.org/content/110/34/13745.abstract</ref> IPCC Summary for Policymakers, AR5, 2014, indicated that the global mean sea level rise will continue during the 21st century, very likely at a faster rate than observed from 1971 to 2010.<ref>http://ar5-syr.ipcc.ch/topic_summary.php</ref> Projected rates and amounts vary.  A January 2017 NOAA report suggests a range of GMSL rise of 0.3 – 2.5 m possible during the 21st century.<ref>https://tidesandcurrents.noaa.gov/publications/techrpt83_Global_and_Regional_SLR_Scenarios_for_the_US_final.pdf</ref>
| author= Fischlin
| chapter=Section 4.4.9: Oceans and shallow seas – Impacts
| chapter-url=http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch4s4-4-9.html
| title=Chapter 4: Ecosystems, their Properties, Goods and Services
| url=http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch4.html
| page=[http://www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-chapter4.pdf#page=24 234]
| editor={{Harvnb|IPCC AR4 WG2|2007}}
Sea level rise is expected to continue for centuries. Because of the slow [[climate inertia|inertia]], long response time for parts of the climate system, it has been estimated that we are already committed to a sea-level rise of approximately {{convert|2.3|m|ft}} for each degree [[Celsius]] of temperature rise within the next 2,000 years.<ref>{{cite journal|url=http://www.pnas.org/content/110/34/13745.abstract?sid=26fd1d37-7276-46e2-9192-0931e6ebf6ab|title=The multimillennial sea-level commitment of global warming|authors=Anders Levermann, Peter U. Clark, Ben Marzeion, Glenn A. Milne, David Pollard, Valentina Radic, and Alexander Robinson|date=13 June 2013|journal=PNAS|doi=10.1073/pnas.1219414110|volume=110|pages=13745–13750|pmid=23858443|pmc=3752235}}</ref> IPCC Summary for Policymakers, AR5, 2014, indicated that the global mean sea level rise will continue during the 21st century, very likely at a faster rate than observed from 1971 to 2010.<ref>{{cite report
| date        = 2014
| title      = Climate Change 2014 Synthesis Report Fifth Assessment Report, AR5
| url        = http://ar5-syr.ipcc.ch/topic_summary.php
| publisher  = Intergovernmental Panel on Climate Change
| access-date =
}}</ref> Projected rates and amounts vary.  A January 2017 NOAA report suggests a range of GMSL rise of 0.3 – 2.5 m possible during the 21st century.<ref>{{cite report
| date        = January 2017
| url        =https://tidesandcurrents.noaa.gov/publications/techrpt83_Global_and_Regional_SLR_Scenarios_for_the_US_final.pdf
| publisher  = National Oceanic and Atmospheric Administration
| edition    = NOAA Technical Report NOS CO-OPS 083
| chapter    =
| section    =
| access-date = 25 January 2017
Sea level rises [[Effects of climate change on humans|can considerably influence human populations]] in coastal and island regions and natural environments like [[marine ecosystem]]s.<ref name=wg1-5-5-1>
Sea level rises [[Effects of climate change on humans|can considerably influence human populations]] in coastal and island regions and natural environments like [[marine ecosystem]]s.<ref name=wg1-5-5-1>http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch5s5-5.html#5-5-1</ref>
| editor={{Harvnb|IPCC AR4 WG1|2007}}
| year=2007
| isbn=978-0-521-88009-1
| chapter=Section 5.5.1: Introductory Remarks
| chapter-url=http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch5s5-5.html#5-5-1
| at=
  | title=Chapter 5: Observations: Ocean Climate Change and Sea Level
  | url=http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch5.html
  | author=Bindoff, N.L., J. Willebrand, V. Artale, A, Cazenave, J. Gregory, S. Gulev, K. Hanawa, C. Le Quéré, S. Levitus, Y. Nojiri, C.K. Shum, L.D. Talley and A. Unnikrishnan
  | quote=
  | accessdate=25 January 2017
  | page=
  | separator=
[[File:Ocean Heat Content (2012).png|thumbnail|250px|right|Ocean heat content (OHC), [http://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/ NOAA] 2012]]
{{See also|Sea level#Sea level change}}
There are two main mechanisms that contribute to observed sea level rise:<ref>
IPCC, [http://www.ipcc.ch/publications_and_data/ar4/wg1/en/faq-5-1.html FAQ 5.1: Is Sea Level Rising?], in {{Harvnb|IPCC AR4 WG1|2007}}.
</ref> (1) [[thermal expansion]]: because of the increase in [[ocean heat content]] (ocean water expands as it warms);<ref>
Albritton ''et al.'', [http://www.grida.no/climate/ipcc_tar/wg1/013.htm#b4 Technical Summary, Box 2: What causes sea level to change?], in {{Harvnb|IPCC TAR WG1|2001}}.
</ref> and (2) the melting of major stores of land ice like [[ice sheet]]s and [[glacier]]s.
On the timescale of centuries to millennia, the melting of ice sheets could result in even higher sea level rise. Partial [[deglaciation]] of the [[Greenland ice sheet]], and possibly the [[West Antarctic ice sheet]], could contribute {{convert|4|to|6|m|ft|abbr=on}} or more to sea level rise.<ref>IPCC, [http://www.ipcc.ch/publications_and_data/ar4/wg2/en/spm.html Summary for Policymakers],  [http://www.ipcc.ch/publications_and_data/ar4/wg2/en/spmsspm-c-15-magnitudes-of.html Section C. Current knowledge about future impacts – Magnitudes of impact] in {{Harvnb|IPCC AR4 WG2|2007}}.</ref>
== Past changes in sea level ==
[[File:Phanerozoic Sea Level.png|thumb|250px|Comparison of two [[Sea-level curve|sea level reconstructions]] during the last 500 Ma. The scale of change during the last glacial/interglacial transition is indicated with a black bar. Note that over most of geologic history, long-term average sea level has been significantly higher than today.]]
Various factors affect the volume or mass of the ocean, leading to long-term changes in [[eustatic sea level]]. The two primary influences are temperature (because the density of water depends on temperature), and the mass of water locked up on land and sea as fresh water in rivers, lakes, glaciers and [[polar ice cap]]s. Over much longer [[geological timescale]]s, changes in the shape of oceanic basins and in land–sea distribution affect sea level. Since the [[Last Glacial Maximum]] about 20,000 years ago, sea level has risen by more than 125 m, with rates varying from tenths of a mm/yr to 10+mm/year, as a result of melting of major ice sheets.<ref name=VGorn2007>{{cite web|last1=Gornitz|first1=Vivien|title=Sea Level Rise, After the Ice Melted and Today|url=http://www.giss.nasa.gov/research/briefs/gornitz_09/|website=Goddard Institute for Space Studies|accessdate=10 September 2015|date=January 2007}}</ref>
During deglaciation between about 19,000 and 8,000 calendar years ago, sea level rose at extremely high rates as the result of the rapid melting of the British-Irish Sea, Fennoscandian, [[Laurentide ice sheet|Laurentide]], [[Barents–Kara Ice Sheet|Barents-Kara]], [[Patagonian Ice Sheet|Patagonian]], Innuitian [[ice sheet]]s and parts of the [[Antarctic ice sheet]]. At the onset of deglaciation about 19,000 calendar years ago, a brief, at most 500-year long, glacio-eustatic event may have contributed as much as 10 m to sea level with an average rate of about 20&nbsp;mm/yr. During the rest of the early Holocene, the rate of sea level rise varied from a low of about 6.0 - 9.9 &nbsp;mm/yr to as high as 30 - 60 &nbsp;mm/yr during brief periods of accelerated sea level rise.<ref name="Cronin2012a">Cronin, T. M. (2012) ''Invited review: Rapid sea-level rise.'' Quaternary Science Reviews. 56:11-30.</ref><ref name="Blanchon2011a">Blanchon, P. (2011a) ''Meltwater Pulses.'' In: Hopley, D. (Ed), ''Encyclopedia of Modern Coral Reefs: Structure, form and process.'' Springer-Verlag Earth Science Series, p. 683-690. ISBN 978-90-481-2638-5</ref>
Solid geological evidence, based largely upon analysis of deep cores of [[coral reef]]s, exists only for 3 major periods of accelerated sea level rise, called ''meltwater pulses'', during the last deglaciation. They are [[Meltwater pulse 1A]] between circa 14,600 and 14,300 calendar years ago; [[Meltwater pulse 1B]] between circa 11,400 and 11,100 calendar years ago; and Meltwater pulse 1C between 8,200 and 7,600 calendar years ago. Meltwater pulse 1A was a 13.5 m rise over about 290 years centered at 14,200 calendar years ago and Meltwater pulse 1B was a 7.5 m rise over about 160 years centered at 11,000 years calendar years ago. In sharp contrast, the period between 14,300 and 11,100 calendar years ago, which includes the [[Younger Dryas]] interval, was an interval of reduced sea level rise at about 6.0 - 9.9 &nbsp;mm/yr. Meltwater pulse 1C was centered at 8,000 calendar years and produced a rise of 6.5 m in less than 140 years.<ref name="Blanchon2011a"/><ref name="Blanchon2011b">Blanchon, P. (2011b) ''Backstepping.'' In: Hopley, D. (Ed), ''Encyclopedia of Modern Coral Reefs: Structure, form and process.'' Springer-Verlag Earth Science Series, p. 77-84. ISBN 978-90-481-2638-5</ref><ref name="BlanchonOthers1995a">Blanchon, P., and Shaw, J. (1995) ''Reef drowning during the last deglaciation: evidence for catastrophic sea-level rise and icesheet collapse.'' Geology, 23:4–8.</ref> Such rapid rates of sea level rising during [[meltwater]] events clearly implicate major ice-loss events related to ice sheet collapse. The primary source may have been meltwater from the Antarctic ice sheet. Other studies suggest a Northern Hemisphere source for the meltwater in the Laurentide ice sheet.<ref name="BlanchonOthers1995a"/>
Recently, it has become widely accepted that late Holocene, 3,000 calendar years ago to present, sea level was nearly stable prior to an acceleration of rate of rise that is variously dated between 1850 and 1900 AD. Late Holocene rates of sea level rise have been estimated using evidence from archaeological sites and late Holocene tidal marsh sediments, combined with tide gauge and satellite records and geophysical modeling. For example, this research included studies of Roman wells in [[Caesarea]] and of Roman ''[[piscina]]e'' in Italy. These methods in combination suggest a mean eustatic component of 0.07 &nbsp;mm/yr for the last 2000 years.<ref name="Cronin2012a"/>
Since 1880, as the Industrial Revolution took center stage, the ocean began to rise briskly, climbing a total of {{convert|210|mm|in|abbr=on}} through 2009 causing extensive erosion worldwide and costing billions.<ref>{{cite news|url=https://www.nytimes.com/2016/02/23/science/sea-level-rise-global-warming-climate-change.html|title=Seas Are Rising at Fastest Rate in Last 28 Centuries|last=GILLIS|first= JUSTIN |newspaper=[[New York Times]]|date=22 February 2016|accessdate=29 February 2016}}</ref>
Sea level rose by 6&nbsp;cm during the 19th century and 19&nbsp;cm in the 20th century.<ref>{{cite journal|last=Jevrejeva|first=Svetlana|author2=J. C. Moore |author3=A. Grinsted |author4=P. L. Woodworth |title=Recent global sea level acceleration started over 200 years ago?|journal=Geophysical Research Letters|date=April 2008|volume=35|issue=8|doi=10.1029/2008GL033611|bibcode = 2008GeoRL..35.8715J }}</ref> Evidence for this includes geological observations, the longest instrumental records and the observed rate of 20th century sea level rise. For example, geological observations indicate that during the last 2,000 years, sea level change was small, with an average rate of only 0.0–0.2&nbsp;mm per year. This compares to an average rate of 1.7 ± 0.5&nbsp;mm per year for the 20th century.<ref>Bindoff ''et al.'',
[http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch5.html Chapter 5: Observations: Oceanic Climate Change and Sea Level], [http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch5s5-es.html Executive summary], in {{Harvnb|IPCC AR4 WG1|2007}}.</ref>
Baart et al. (2012) show that it is important to account for the effect of the 18.6-year lunar nodal cycle before acceleration in sea level rise should be concluded.<ref>{{cite web|url=http://jcronline.org/doi/abs/10.2112/JCOASTRES-D-11-00169.1/|title=The effect of the 18.6-year lunar nodal cycle on regional sea-level rise estimates|date=September 20, 2011|author1=BAART, F. |author2=VAN GELDER, P.H.A.J.M. |author3=DE RONDE, J. |author4=VAN KONINGSVELD, M., |author5=WOUTERS, B.  |lastauthoramp=yes }}</ref> Based on [[tide gauge]] data, the rate of global average sea level rise during the 20th century lies in the range 0.8 to 3.3&nbsp;mm/yr, with an average rate of 1.8&nbsp;mm/yr.<ref name="AnisimovOthers2001a">Anisimov ''et al.'', [http://www.grida.no/publications/other/ipcc%5Ftar/?src=/climate/ipcc_tar/wg1/408.htm Chapter 11: Changes in Sea Level],
[http://www.grida.no/climate/ipcc_tar/wg1/422.htm#tab119 Table 11.9], in {{Harvnb|IPCC TAR WG1|2001}}.</ref>
A two degrees Celsius of warming would warm the Earth above [[Eemian]] levels, move conditions closer to the [[Pliocene]] climate, a time when sea level was in the range of 25 meters higher than today.<ref>{{cite web|url=http://www.giss.nasa.gov/research/news/20111208/|title=Paleoclimate Record Points Toward Potential Rapid Climate Changes|date=8 December 2011|author=NASA}}</ref> However, one study argues that sea level during the Pliocene might have only risen by 9 to 13.5 meters, due to more resilient ice sheets.<ref>{{cite web|url=http://news.stanford.edu/news/2015/september/sea-level-rise-090315.html|title=Ice sheets may be more resilient than thought, say Stanford scientists|publisher=Stanford University|year=2015}}</ref>
Warren Cornwall, in: 'Ghosts of Ocean Past', published in an 'Science' monographic issue, 13 November 2015: 'Sea changes', pgs 752-755, presented a chart showing the current warming respect to preindustrial era of 1&nbsp;°C, that goes along with the current {{CO2}} in atmosphere of 400 ppm. With the same 400 ppm {{CO2}}, 3 million years ago, with an increased average temperature of 2 to 3&nbsp;°C above our preindustrial levels, Sea level was between 6 meters and a not defined enough upper range. The issue may be not if sea level will rise, but how much, and at what rate.
== Projections ==
[[File:Projected change in global sea level rise if atmospheric carbon dioxide concentrations were to either quadruple or double (NOAA GFDL).png|thumb|350px|alt=Refer to caption and image description|This graph shows the minimum projected change in global sea level rise if [[atmospheric carbon dioxide]] (CO<sub>2</sub>) concentrations were to either quadruple or double.
<ref name="gfdl thermal expansion projections">
| agency=[[National Oceanic and Atmospheric Administration|NOAA]]
| source={{citation
| author=NOAA GFDL
| url=http://www.gfdl.noaa.gov/climate-impact-of-quadrupling-co2
| title=Geophysical Fluid Dynamics Laboratory - Climate Impact of Quadrupling CO<sub>2</sub>
| publisher=NOAA GFDL
| location=Princeton, NJ, USA
}}</ref> The projection is based on several multi-century integrations of a [[Geophysical Fluid Dynamics Laboratory|GFDL]] [[global climate model|global coupled ocean-atmosphere model]]. These projections are the expected changes due to [[thermal expansion]] of sea water alone, and do not include the effect of melted continental [[ice sheet]]s. With the effect of ice sheets included the total rise will be larger, by an uncertain but possibly substantial factor.<ref name="gfdl thermal expansion projections"/> Image credit: [[National Oceanic and Atmospheric Administration|NOAA]] GFDL.]]
{{See also|Global climate model#Projections of future climate change|l1=Projections of future climate change|Future sea level}}
=== 21st century ===
The 2007 [[IPCC Fourth Assessment Report|Fourth Assessment Report]] (IPCC 4) projected century-end sea levels using the [[Special Report on Emissions Scenarios]] (SRES). SRES developed emissions scenarios to project climate-change impacts.<ref>{{cite book
| year=2009
| pages=22–24
| title=Global Climate Change Impacts in the United States
| editor=Karl, TR
| publisher=Cambridge University Press
| location = 32 Avenue of the Americas, New York, NY 10013-2473, USA
| isbn=978-0-521-14407-0
| url=http://www.globalchange.gov/publications/reports/scientific-assessments/us-impacts/
| accessdate=2011-04-28|display-editors=etal}}
The projections based on these scenarios are not predictions,<ref>IPCC AR4, [http://www.ipcc.ch/publications_and_data/ar4/wg1/en/annexessglossary-p-z.html Glossary P-Z: "Projection"], in {{Harvnb|IPCC AR4 WG1|2007}}.</ref> but reflect plausible estimates of future social and [[economic development]] (e.g., [[economic growth]], [[population projection|population level]]).<ref>Morita ''et al.'', [http://www.grida.no/climate/ipcc_tar/wg3/068.htm Chap. 2: Greenhouse Gas Emission Mitigation Scenarios and Implications], [http://www.grida.no/climate/ipcc_tar/wg3/071.htm#221 Section 2.2.1: Introduction to Scenarios], in {{Harvnb|IPCC TAR WG3|2001}}.</ref>
The six SRES "marker" scenarios projected sea level to rise by {{convert|18|to|59|cm}}.<ref name="syr_3-2-1">
IPCC, [http://www.ipcc.ch/publications_and_data/ar4/syr/en/mains3.html Topic 3], [http://www.ipcc.ch/publications_and_data/ar4/syr/en/mains3-2-1.html Section 3.2.1: 21st century global changes], [http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr.pdf p. 45], in {{Harvnb|IPCC AR4 SYR|2007}}.</ref> Their projections were for the time period 2090–99, with the increase in level relative to average sea level over the 1980–99 period. This estimate did not include all of the possible contributions of ice sheets.
[[James Hansen|Hansen]] (2007), assumed an ice sheet contribution of 1&nbsp;cm for the decade 2005–15, with a potential ten year doubling time for sea-level rise, based on a nonlinear ice sheet response, which would yield 5 m this century.<ref name=Hansen2007>{{cite journal|url=http://iopscience.iop.org/1748-9326/2/2/024002|title=Scientific reticence and sea level rise|author=J E Hansen|year=2007|journal=Environmental Research Letters|publisher=IOPScience|doi=10.1088/1748-9326/2/2/024002|volume=2|pages=024002}}</ref>
Research from 2008 observed rapid declines in ice-mass balance from both Greenland and Antarctica, and concluded that sea-level rise by 2100 is likely to be at least twice as large as that presented by IPCC AR4, with an upper limit of about two meters.<ref name="Copenhagen Diagnosis">
{{cite journal
| author=Allison
| display-authors=etal
| title=The Copenhagen Diagnosis, 2009: Updating the World on the Latest Climate Science
| year=2009
| url=http://www.copenhagendiagnosis.com/read/default.html
| ref=harv}}</ref>
Projections assessed by the [[US National Research Council]] (2010)<ref name=nrcpro/> suggest possible sea level rise over the 21st century of between {{convert|56|and|200|cm|in|abbr=on}}. The NRC describes the IPCC projections as "conservative".<ref name=nrcpro>{{cite book
| year=2010
| pages=243–250
| chapter=7 Sea Level Rise and the Coastal Environment
| title=Advancing the Science of Climate Change
| publisher=The National Academies Press
| location=Washington, D.C.
| author=America's Climate Choices: Panel on Advancing the Science of Climate Change, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, NATIONAL RESEARCH COUNCIL OF THE NATIONAL ACADEMIES
| url=http://books.nap.edu/openbook.php?record_id=12782&page=243
| isbn=978-0-309-14588-6
| accessdate=2011-06-17
| quote = (From pg 250) Even if sea-level rise were to remain in the conservative range projected by the IPCC (0.6–1.9 feet [0.18–0.59 m])—not considering potentially much larger increases due to rapid decay of the Greenland or West Antarctic ice sheets—tens of millions of people worldwide would become vulnerable to flooding due to sea-level rise over the next 50 years (Nicholls, 2004; Nicholls and Tol, 2006). This is especially true in densely populated, low-lying areas with limited ability to erect or establish protective measures. In the United States, the high end of the conservative IPCC estimate would result in the loss of a large portion of the nation's remaining coastal wetlands. The impact on the east and Gulf coasts of the United States of 3.3 feet (1 m) of sea-level rise, which is well within the range of more recent projections for the 21st century (e.g., Pfeffer et al., 2008; Vermeer and Rahmstorf, 2009), is shown in pink in [http://books.nap.edu/openbook.php?record_id=12782&page=251#p2001c3c59960251001 Figure 7.7]. Also shown, in red, is the effect of 19.8 feet (6 m) of sea-level rise, which could occur over the next several centuries if warming were to continue unabated.
In 2011, [[Eric Rignot|Rignot]] and others projected a rise of {{convert|32|cm}} by 2050. Their projection included increased contributions from the Antarctic and Greenland ice sheets. Use of two completely different approaches reinforced the Rignot projection.<ref>{{cite journal
| author = Rignot E.
|author2=I. Velicogna |author3=M. R. van den Broeke |author4=A. Monaghan |author5=J. Lenaerts
| title = Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise
| journal = Geophysical Research Letters
| volume = 38
| doi = 10.1029/2011GL046583
| quote = Considerable disparity remains between these estimates due to the inherent uncertainties of each method, the lack of detailed comparison between independent estimates, and the effect of temporal modulations in ice sheet surface mass balance. Here, we present a consistent record of mass balance for the Greenland and Antarctic ice sheets over the past two decades, validated by the comparison of two independent techniques over the past eight years: one differencing perimeter loss from net accumulation, and one using a dense time series of timevariable gravity. We find excellent agreement between the two techniques for absolute mass loss and acceleration of mass loss.
| bibcode=2011GeoRL..3805503R
| year = 2011
| issue = 5
| ref = harv}}
</ref><ref name="Romm10Mar2011">{{cite web |url=http://thinkprogress.org/romm/2011/03/10/207664/jpl-greenland-antarctica-ice-sheet-mass-loss-accelerating-sea-level-rise-1-foot-by-2050/ |title=JPL bombshell: Polar ice sheet mass loss is speeding up, on pace for 1 foot sea level rise by 2050 |author=[[Joseph J. Romm|Romm, Joe]] |date=10 Mar 2011 |work=Climate Progress |publisher=Center for American Progress Action Fund |accessdate=16 April 2012}}</ref>
In its [[Fifth Assessment Report]] (2013), The IPCC found that recent observations of global average sea level rise at a rate of 3.2 [2.8 to 3.6] mm per year is consistent with the sum of contributions from observed thermal ocean expansion due to rising temperatures (1.1 [0.8 to 1.4] mm per year), glacier melt (0.76 [0.39 to 1.13] mm per year), Greenland ice sheet melt  (0.33 [0.25 to 0.41] mm per year),  Antarctic ice sheet melt (0.27 [0.16 to 0.38] mm per year), and changes to land water storage (0.38 [0.26 to 0.49] mm per year). The report had also concluded that if emissions continue to keep up with the worst case IPCC scenarios,  global average sea level could rise by nearly 1m by 2100 (0.52−0.98 m from a 1986-2005 baseline). If emissions follow the lowest emissions scenario, then global average sea level is projected to rise by between 0.28−0.6 m by 2100 (compared to a 1986−2005 baseline).<ref>{{cite web|last1=Churchs|first1=John|last2=Clark|first2=Peter|title=Chapter 13: Sea Level Change - Final Draft Underlying Scientific-Technical Assessment|url=http://www.climatechange2013.org/images/uploads/WGIAR5_WGI-12Doc2b_FinalDraft_Chapter13.pdf|website=climatechange2013.org |publisher=IPCC Working Group I|accessdate=January 21, 2015}}</ref>
The Third [[National Climate Assessment]] (NCA), released May 6, 2014, projected a sea level rise of 1 to 4 feet (30–120&nbsp;cm) by 2100. Decision makers who are particularly susceptible to risk may wish to use a wider range of scenarios from 8 inches to 6.6 feet (20–200&nbsp;cm) by 2100.<ref name="Sea Level Rise Key Message">{{cite web|title=Sea Level Rise Key Message Third National Climate Assessment|url=http://nca2014.globalchange.gov/report/our-changing-climate/sea-level-rise|website=National Climate Assessment|accessdate=25 June 2014}}</ref>
A 2015 study by sea level rise experts concluded that based on [[MIS 5e]] data, sea level rise could rise faster in the coming decades, with a doubling time of 10, 20 or 40 years. The study abstract explains: ''We argue that ice sheets in contact with the ocean are vulnerable to non-linear disintegration in response to ocean warming, and we posit that ice sheet mass loss can be approximated by a doubling time up to sea level rise of at least several meters. Doubling times of 10, 20 or 40 years yield sea level rise of several meters in 50, 100 or 200 years. Paleoclimate data reveal that subsurface ocean warming causes ice shelf melt and ice sheet discharge.''
''Our climate model exposes amplifying feedbacks in the Southern Ocean that slow Antarctic bottom water formation and increase ocean temperature near ice shelf grounding lines, while cooling the surface ocean and increasing sea ice cover and water column stability. Ocean surface cooling, in the North Atlantic as well as the Southern Ocean, increases tropospheric horizontal temperature gradients, eddy kinetic energy and baroclinicity, which drive more powerful storms.''<ref>{{cite journal|title=Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2◦C global warming is highly dangerous|url=http://www.atmos-chem-phys-discuss.net/15/20059/2015/acpd-15-20059-2015.pdf |author=J. Hansen |author2=M. Sato |author3=P. Hearty |author4=R. Ruedy |author5=M. Kelley |author6=V. Masson-Delmotte |author7=G. Russell |author8=G. Tselioudis |author9=J. Cao |author10=E. Rignot |author11=I. Velicogna |author12=E. Kandiano |author13=K. von Schuckmann |author14=P. Kharecha |author15=A. N. Legrande |author16=M. Bauer |author17=K.-W. Lo |year=2015|journal=Atmospheric Chemistry and Physics (ACP)|doi=10.5194/acpd-15-20059-2015|volume=15|pages=20059–20179}}</ref> However, Greg Holland from the [[National Center for Atmospheric Research]], who reviewed the James (Jim) Hanson study, noted “''There is no doubt that the sea level rise, within the IPCC, is a very conservative number, so the truth lies somewhere between IPCC and Jim.''”<ref>{{cite web|url=http://www.washingtonpost.com/news/energy-environment/wp/2015/07/23/controversial-sea-level-rise-paper-is-now-published-online/|title=James Hansen’s controversial sea level rise paper has now been published online|year=2015|publisher=Washington Post}}</ref>
=== After 2100 ===
{{further|Long-term effects of global warming}}
There is a widespread consensus that substantial long-term sea-level rise will continue for centuries to come even if the temperature stabilizes.<ref name=nrccon>{{cite book
| year=2010
| page=245
| chapter=7 Sea Level Rise and the Coastal Environment
| title=Advancing the Science of Climate Change
| publisher=[http://www.nap.edu/ The National Academies Press]
| location=Washington, D.C.
| author=America's Climate Choices: Panel on Advancing the Science of Climate Change, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, NATIONAL RESEARCH COUNCIL OF THE NATIONAL ACADEMIES
| url=http://books.nap.edu/openbook.php?record_id=12782&page=245
| isbn=978-0-309-14588-6
| accessdate=2011-06-17}}
</ref> IPCC AR4 estimated that at least a partial deglaciation of the [[Greenland ice sheet]], and possibly the [[West Antarctic ice sheet]], would occur given a global average temperature increase of 1–4&nbsp;°C <!-- Do not simply put {convert} to °F here as it is not 1–4 °C above 0°C but 1–4 °C change from average --> (relative to temperatures over the years 1990–2000).<ref>IPCC AR4, [http://www.ipcc.ch/publications_and_data/ar4/wg2/en/spm.html Summary for Policymakers],
[http://www.ipcc.ch/publications_and_data/ar4/wg2/en/spmsspm-c-15-magnitudes-of.html Section C. Current knowledge about future impacts – Magnitudes of impact] in {{Harvnb|IPCC AR4 WG2|2007}}
</ref> This estimate was given about a 50% chance of being correct.<ref>IPCC AR4, [http://www.ipcc.ch/publications_and_data/ar4/wg2/en/spmsspm-e.html Summary for Policymakers, Endbox 2. Communication of Uncertainty], in {{Harvnb|IPCC AR4 WG2|2007}}</ref> The estimated timescale was centuries to millennia, and would contribute {{convert|4|to|6|m}} or more to sea levels over this period.
Rising sea levels will cause flooding and will have the ability to wipe out entire cities. In a study published by Nature, the entire state of [[Delaware]] could be completely wiped out by 2500.<ref>{{Cite web|url=https://www.washingtonpost.com/news/capital-weather-gang/wp/2016/03/30/what-6-feet-of-sea-level-rise-looks-like-for-our-vulnerable-coastal-cities/|title=Scientists say Antarctic melting could double sea level rise. Here’s what that looks like.|last=|first=|date=|website=|publisher=|access-date=}}</ref>
{{See also|Ice-sheet dynamics|Ice-sheet model|Climate model}}
There is the possibility of a rapid change in glaciers, ice sheets, and hence sea level.<ref>{{cite book
| year=2008
| title=U.S. Climate Change Science Program: Synthesis and Assessment Report 3.4: Abrupt Climate Change: Summary and Findings
| page=2
| format=PDF
| url=http://downloads.climatescience.gov/sap/sap3-4/sap3-4-brochure.pdf
| publisher=US Geological Survey
| location = Reston, VA
| accessdate=2010-08-20}}
</ref> Predictions of such a change are highly uncertain due to a lack of scientific understanding. Modeling of the processes associated with a rapid ice-sheet and glacier change could potentially increase future projections of sea-level rise.
Hansen (2007), concluded that [[paleoclimatology|paleoclimate]] ice sheet models generally do not include physics of [[ice stream]]s, effects of [[premelting|surface melt]] descending through [[crevasse]]s and lubricating [[basal flow]], or realistic interactions with the ocean. The calibration of projected modelling for future sea-level rise is generally done with a linear projection of future sea level. Thus, does not include potential nonlinear collapse of an ice sheet.<ref name=Hansen2007 />
[[File:Corp2400 - Flickr - NOAA Photo Library.jpg|thumb|250px|Close-up of [[Ross Ice Shelf]], the largest ice shelf of Antarctica, about the size of France and up to several hundred metres thick.]]
{{See also|Ice shelf}}
Each year about 8&nbsp;mm of [[Precipitation#Measurement|precipitation (liquid equivalent)]] falls on the [[Antarctic ice sheet|ice sheets in Antarctica]] and [[Greenland ice sheet|Greenland]], mostly as snow, which accumulates and over time forms glacial ice.  Much of this precipitation began as water vapor evaporated from the ocean surface. To a first approximation, the same amount of water appeared to return to the ocean in [[iceberg]]s and from ice melting at the edges. Scientists previously had estimated which is greater, ice going in or coming out, called the [[Glacier mass balance|mass balance]], important because a nonzero balance causes changes in global sea level. High-precision [[gravimetry]] from [[Gravity Recovery and Climate Experiment|satellites]] determined that Greenland was losing more than 200 billion tons of ice per year, in accord with loss estimates from ground measurement.<ref>[http://www.skepticalscience.com/greenland-cooling-gaining-ice-intermediate.htm Skeptical Science: Is Greenland gaining or losing ice?]</ref> The rate of ice loss was accelerating,<ref>[http://www.sciencenews.org/view/generic/id/346332/description/Sea_level_rise_overflowing_estimates ''Sea level rise overflowing estimates; Feedback mechanisms are speeding up ice melt''] November 8, 2012 [[Science News]]</ref> having grown from 137 gigatons in 2002–2003.<ref>{{Cite journal | last1 = Velicogna | first1 = I. | doi = 10.1029/2009GL040222 | title = Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE | journal = Geophysical Research Letters | volume = 36 | issue = 19 | year = 2009 | pmid =  | pmc = |bibcode = 2009GeoRL..3619503V }}</ref>
* The total global ice mass lost from Greenland, Antarctica and Earth's glaciers and ice caps during 2003–2010 was about 4.3 trillion tons (1,000 cubic miles), adding about 12&nbsp;mm (0.5&nbsp;in) to global sea level, enough ice to cover an area comparable to the United States 50&nbsp;cm (1.5&nbsp;ft) deep.<ref>{{cite web|title=NASA Mission Takes Stock of Earth's Melting Land Ice|url=http://www.nasa.gov/topics/earth/features/grace20120208.html|work=NASA/JPL-Caltech/University of Colorado|publisher=NASA|accessdate=25 April 2013|date=February 2012}}</ref>
* The melting of small glaciers on the margins of [[Greenland]] and the [[Antarctic Peninsula]] would increase sea level around 0.5 meter.  At the extreme potential, according to the [[IPCC Third Assessment Report|Third Assessment Report]] of the [[International Panel on Climate Change]], the ice contained within the [[Greenland ice sheet]] entirely melted increases sea level by 7.2 meters (24 feet).  The ice contained within the [[Antarctic ice sheet]] entirely melted would produce 61.1 meters (200 feet) of sea-level change, both totaling a sea-level rise of 68.3 meters (224 feet).<ref>Anisimov ''et al.'',
[http://www.grida.no/publications/other/ipcc%5Ftar/?src=/climate/ipcc_tar/wg1/412.htm Section Models of thermal expansion],
[http://www.grida.no/publications/other/ipcc%5Ftar/?src=/climate/ipcc_tar/wg1/412.htm#tab113 Table 1.3], in {{Harvnb|IPCC TAR WG1|2001}}.</ref>
It is estimated that Antarctica, if fully melted, would contribute more than 60 metres of sea level rise, and Greenland would contribute more than 7 metres. Small glaciers and ice caps on the margins of Greenland and the Antarctic Peninsula might contribute about 0.5 metres. While the latter figure is much smaller than for Antarctica or Greenland it could occur relatively quickly (within the coming century) whereas melting of Greenland would be slow (perhaps 1,500 years to fully deglaciate at the fastest likely rate) and Antarctica even slower.<ref>Anisimov ''et al.'', [http://www.grida.no/publications/other/ipcc%5Ftar/?src=/climate/ipcc_tar/wg1/408.htm Chapter 11. Changes in Sea Level],
[http://www.grida.no/publications/other/ipcc%5Ftar/?src=/climate/ipcc_tar/wg1/412.htm Section Models of thermal expansion],
[http://www.grida.no/publications/other/ipcc%5Ftar/?src=/climate/ipcc_tar/wg1/412.htm#tab113 Table 1.3], in {{Harvnb|IPCC TAR WG1|2001}}.</ref> However, this calculation does not account for the possibility that as meltwater flows under and lubricates the larger ice sheets, they could begin to move much more rapidly towards the sea.<ref>{{cite journal| url = http://www.sciencemag.org/cgi/content/abstract/297/5579/218 | title=Surface Melt-Induced Acceleration of Greenland Ice-Sheet Flow | author=Zwally H.J. | journal = Science | volume = 297 | pages = 218–222 | doi = 10.1126/science.1072708 | year= 2002 | pmid = 12052902| issue = 5579 | bibcode=2002Sci...297..218Z| display-authors = 1| last2 = Abdalati| first2 = W| last3 = Herring| first3 = T| last4 = Larson| first4 = K| last5 = Saba| first5 = J| last6 = Steffen| first6 = K| ref = harv}}</ref><ref>{{cite web | url = http://www.gsfc.nasa.gov/topstory/20020606greenland.html | title=Greenland Ice Sheet flows faster during summer melting | date = 2006-06-02 | publisher = Goddard Space Flight Center (press release) }}</ref>
In 2002, Rignot and Thomas found that the West Antarctic and Greenland ice sheets were losing mass, while the East Antarctic ice sheet was probably in balance (although they could not determine the sign of the mass balance for The East Antarctic ice sheet).<ref>{{cite journal| last=Rignot |author2=Thomas, RH | journal=Science| volume=297| pages=1502–1506| year= 2002 |  pmid=12202817 | doi = 10.1126/science.1073888 | title=Mass Balance of Polar Ice Sheets| first1=E| issue=5586|bibcode = 2002Sci...297.1502R| ref=harv }}</ref> Kwok and Comiso (''J. Climate'', v15, 487–501, 2002) also discovered that temperature and pressure anomalies around West Antarctica and on the other side of the Antarctic Peninsula correlate with recent [[El Niño|Southern Oscillation]] events.
In 2005 it was reported that during 1992–2003, East Antarctica thickened at an average rate of about 18&nbsp;mm/yr while West Antarctica showed an overall thinning of 9&nbsp;mm/yr. associated with increased precipitation. A gain of this magnitude is enough to slow sea-level rise by 0.12 ± 0.02&nbsp;mm/yr.<ref>{{cite journal| last=Davis| journal=Science|date=24 June 2005| doi=10.1126/science.1110662| pages= 1898–1901| pmid=15905362| volume=308| issue= 5730| title=Snowfall-Driven Growth in East Antarctic Ice Sheet Mitigates Recent Sea-Level Rise| first=Curt H. |author2=Yonghong Li |author3=Joseph R. McConnell |author4=Markus M. Frey |author5=Edward Hanna |bibcode = 2005Sci...308.1898D| ref=harv }}</ref>
[[Image:Antarctic shelf ice hg.png|thumb|250px|Processes around an Antarctic ice shelf]]
{{See also|Antarctica#Ice mass and global sea level}}
On the Antarctic continent itself, the large volume of ice present stores around 70% of the world's fresh water.<ref name="howstuffworks">{{cite web|url=http://science.howstuffworks.com/question473.htm|title=How Stuff Works: polar ice caps|publisher=howstuffworks.com|accessdate=2006-02-12}}</ref> This ice sheet is constantly gaining ice from snowfall and losing ice through outflow to the sea.
Sheperd et al. 2012, found that different satellite methods were in good agreement and combining methods leads to more certainty with East Antarctica, West Antarctica, and the Antarctic Peninsula changing in mass by +14 ± 43, –65 ± 26, and –20 ± 14 gigatonnes per year.<ref>[http://www.sciencemag.org/content/338/6111/1183 Sheperd et al 2012 A Reconciled Estimate of Ice-Sheet Mass Balance]</ref>
====East Antarctic ice sheet (EAIS)====
{{Main article|East Antarctic Ice Sheet}}
East Antarctica is a cold region with a ground-base above sea level and occupies most of the continent. This area is dominated by small accumulations of snowfall which becomes ice and thus eventually seaward glacial flows. The mass balance of the East Antarctic Ice Sheet as a whole over the period 1980-2004 is thought to be slightly positive (lowering sea level) or near to balance, with a large degree of uncertainty.<ref name="ShepherdWingham2007" /><ref name="RignotBamber2008" /> However, increased ice outflow has been suggested in some regions.<ref name="RignotBamber2008" /><ref name="ChenWilson2008">{{cite journal| doi = 10.1016/j.epsl.2007.10.057| last1 = Chen | first1 = J. L.| last2 = Wilson | first2 = C. R.| last3 = Tapley | first3 = B. D.| last4 = Blankenship | first4 = D.| last5 = Young | first5 = D.| year = 2008| title = Antarctic regional ice loss rates from GRACE| journal = Earth and Planetary Science Letters| volume = 266| issue = 1–2| pages = 140–148| pmid = | pmc = |bibcode = 2008E&PSL.266..140C }}</ref>
====West Antarctic ice sheet (WAIS)====
{{Main article|West Antarctic Ice Sheet}}
West Antarctica is currently experiencing a net outflow of glacial ice, which will increase global sea level over time. A review of the scientific studies looking at data from 1992 to 2006 suggested a net loss of around 50 gigatons of ice per year was a reasonable estimate (around 0.14&nbsp;mm of yearly sea-level rise),<ref name="ShepherdWingham2007">{{cite journal| doi = 10.1126/science.1136776| last1 = Shepherd | first1 = A.| last2 = Wingham | first2 = D.| title = Recent Sea-Level Contributions of the Antarctic and Greenland Ice Sheets| journal = [[Science (journal)|Science]]| volume = 315| issue = 5818| pages = 1529–1532| year = 2007| pmid = 17363663| pmc = }}</ref> although significant acceleration of outflow glaciers in the [[Amundsen Sea Embayment]] could have more than doubled this figure for the year 2006.<ref name="RignotBamber2008">{{cite journal| doi = 10.1038/ngeo102| last1 = Rignot | first1 = E.| last2 = Bamber | first2 = J. L.| last3 = Van Den Broeke | first3 = M. R.| last4 = Davis | first4 = C.| last5 = Li | first5 = Y.| last6 = Van De Berg | first6 = W. J.| last7 = Van Meijgaard | first7 = E.| year = 2008| title = Recent Antarctic ice mass loss from radar interferometry and regional climate modelling| journal = [[Nature Geoscience]]| volume = 1| issue = 2| pages = 106–110| pmid = | url=http://www.researchgate.net/publication/232802727_Recent_Antarctic_ice_mass_loss_from_radar_interferometry_and_regional_climate_modelling|bibcode = 2008NatGe...1..106R }}</ref>
Thomas et al. found evidence of an accelerated contribution to sea level rise from West Antarctica.<ref>{{cite journal| last=Thomas| year= 2004| journal=Science| volume=306| pages= 255–258 | pmid=15388895 | doi = 10.1126/science.1099650 | title=Accelerated Sea-Level Rise from West Antarctica| first1=R| issue=5694|bibcode = 2004Sci...306..255T| ref=harv |display-authors=etal}}</ref> The data showed that the Amundsen Sea sector of the [[West Antarctic Ice Sheet]] was discharging 250 cubic kilometres of ice every year, which was 60% more than precipitation accumulation in the [[drainage basin|catchment]] areas. This alone was sufficient to raise sea level at 0.24&nbsp;mm/yr. Further, thinning rates for the glaciers studied in 2002–03 had increased over the values measured in the early 1990s. The [[bedrock]] underlying the glaciers was found to be hundreds of metres deeper than previously known, indicating exit routes for ice from further inland in the Byrd Subpolar Basin. Thus the West Antarctic ice sheet may not be as stable as has been supposed.
A 2009 study found that the rapid collapse of West Antarctic Ice Sheet would raise sea level by {{convert|3.3|m|ft}}.<ref name="Bamber2009">
{{cite journal |author1=Bamber J.L. |author2=Riva R.E.M. |author3=Vermeersen B.L.A. |author4=LeBroq A.M. |title=Reassessment of the potential sea-level rise from a collapse of the West Antarctic Ice Sheet |journal=[[Science (journal)|Science]] |volume=324 |pages=901–3 |year=2009 | doi =10.1126/science.1169335 |pmid=19443778 |issue=5929|bibcode = 2009Sci...324..901B }}</ref>
{{Main article|Retreat of glaciers since 1850|Glacier mass balance}}
Observational and modelling studies of [[Retreat of glaciers since 1850|mass loss from glaciers and ice caps]] indicate a contribution to sea-level rise of 0.2–0.4&nbsp;mm/yr, averaged over the 20th century.<ref>[Changes in sea level | page 3 | https://en.wikipedia.org/wiki/Sea_level_rise]</ref>
The results from Dyurgerov show a sharp increase in the contribution of mountain and subpolar glaciers to sea-level rise since 1996 (0.5&nbsp;mm/yr) to 1998 (2&nbsp;mm/yr) with an average of about 0.35&nbsp;mm/yr since 1960.<ref>Dyurgerov, Mark. 2002. Glacier Mass Balance and Regime: Data of Measurements and Analysis. INSTAAR Occasional Paper No. 55, ed. M. Meier and R. Armstrong. Boulder, CO: Institute of Arctic and Alpine Research, University of Colorado.
Distributed by National Snow and Ice Data Center, Boulder, CO. A shorter discussion is at [http://nsidc.org/sotc/sea_level.html]</ref> Of interest also is Arendt et al., who estimate the contribution of Alaskan glaciers of 0.14±0.04&nbsp;mm/yr between the mid-1950s to the mid-1990s, increasing to 0.27&nbsp;mm/yr in the middle and late 1990s.<ref>{{cite journal| last=Arendt| journal=Science| volume=297| pages=382–386|date=July 2002 | title=Rapid Wastage of Alaska Glaciers and Their Contribution to Rising Sea Level | pmid=12130781 | doi = 10.1126/science.1072497| first1=AA| issue=5580 |bibcode = 2002Sci...297..382A| ref=harv |display-authors=etal}}</ref>
=== Greenland ===
[[File:Greenland ssi 2007.jpg|thumb|250px|[[Greenland]] 2007 melt anomaly, measured as the difference between the number of days on which melting occurred in 2007 compared to the average annual melting days from 1988–2006<ref>[http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=1784 Earth Observatory (2009) Melting Anomalies in Greenland in 2007]</ref>]]
{{Main article|Greenland ice sheet}}
In 2004 Rignot et al. estimated a contribution of 0.04 ± 0.01&nbsp;mm/yr to sea level rise from South East Greenland.<ref name="Rignot 2004"/> In the same year, Krabill ''et al.'' estimate a net contribution from [[Greenland]] to be at least 0.13&nbsp;mm/yr in the 1990s.<ref>{{cite journal| last=Krabill| journal=Science| volume= 289| issue= 5478| pages= 428–430|date=21 July 2000 | pmid=10903198 | doi = 10.1126/science.289.5478.428 | title=Greenland Ice Sheet: High-Elevation Balance and Peripheral Thinning| first1=W|bibcode = 2000Sci...289..428K| ref=harv |display-authors=etal}}</ref> Joughin ''et al.'' have measured a doubling of the speed of [[Jakobshavn Isbræ]] between 1997 and 2003.<ref>{{cite journal| last=Joughin| journal=[[Nature (journal)|Nature]]| volume= 432| pages=608–610|date=December 2004 |  pmid=15577906 | doi = 10.1038/nature03130 | title=Large fluctuations in speed on Greenland's Jakobshavn Isbræ glacier| first1=I| issue=7017|bibcode = 2004Natur.432..608J| ref=harv |display-authors=etal}}</ref> This is Greenland's largest outlet glacier; it drains 6.5% of the ice sheet, and is thought to be responsible for increasing the rate of sea-level rise by about 0.06 millimetres per year, or roughly 4% of the 20th-century rate of sea-level increase.<ref>[http://www.spaceref.com/news/viewpr.html?pid=15611 Report shows movement of glacier has doubled speed | SpaceRef – Your Space Reference<!-- Bot generated title -->]</ref> In 2004, Rignot ''et al.'' estimated a contribution of 0.04±0.01&nbsp;mm/yr to sea-level rise from southeast Greenland.<ref name="Rignot 2004">{{cite journal| last=Rignot| journal=Geophysical Research Letters| year=2004| volume=31| pages=L10401 | title=Rapid ice discharge from southeast Greenland glaciers| doi = 10.1029/2004GL019474| first1=E.| bibcode=2004GeoRL..3110401R| issue=10| ref=harv|display-authors=etal}}</ref>
Rignot and Kanagaratnam produced a comprehensive study and map of the [[outlet glacier]]s and basins of Greenland.<ref>{{cite journal| last=Rignot |author2=Kanagaratnam, P| url=http://www.sciencemag.org/cgi/content/abstract/311/5763/986?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=luckman&searchid=1140284328766_4322&FIRSTINDEX=0&journalcode=sci | journal=Science| volume= 311| pages= 986–90| year= 2006 | title = Changes in the Velocity Structure of the Greenland Ice Sheet | doi = 10.1126/science.1121381 | pmid = 16484490| first1=E| issue=5763 |bibcode = 2006Sci...311..986R| ref=harv }}</ref> They found widespread glacial acceleration below 66 N in 1996 which spread to 70 N by 2005; and that the ice sheet loss rate in that decade increased from 90 to 200 cubic km/yr; this corresponds to an extra 0.25–0.55&nbsp;mm/yr of sea level rise.
In July 2005 it was reported that the [[Kangerlussuaq Glacier]], on Greenland's east coast, was moving towards the sea three times faster than a decade earlier. Kangerdlugssuaq is around 1,000 m thick, 7.2&nbsp;km (4.5 [[Statute mile|miles]]) wide, and drains about 4% of the ice from the Greenland ice sheet.<ref>{{cite news| url=http://news.independent.co.uk/world/environment/article301493.ece | work=[[The Independent]] | location=London | title=Melting Greenland glacier may hasten rise in sea level | first=Steve | last=Connor | date=2005-07-25 | accessdate=2010-04-30}}</ref> Measurements of Kangerdlugssuaq in 1988 and 1996 showed it moving at between 5 and 6&nbsp;km/yr (3.1–3.7 miles/yr), while in 2005 that speed had increased to 14&nbsp;km/yr (8.7 miles/yr).
According to the 2004 [[Arctic Climate Impact Assessment]], climate models project that local warming in Greenland will exceed 3&nbsp;°C during this century. Also, [[ice-sheet model]]s project that such a warming would initiate the long-term melting of the ice sheet, leading to a complete melting of the Greenland ice sheet over several millennia, resulting in a global sea level rise of about seven metres.<ref>http://umcca.um.edu.my/glex2308/micellaneous/The%20Role%20Sea%20Ice%20in%20Dangerous%20Climate%20Change.pdf</ref>
== Subsidence and effective sea level rise ==
Many ports, urban conglomerations, and agricultural regions are built on river deltas, where [[subsidence]] contributes to a substantial increase in ''effective'' sea level rise.  This is caused by both unsustainable extraction of groundwater (in some place also by extraction of oil and gas), and by levees and other flood management practices that prevent accumulation of sediments to compensate for the natural settling of deltaic soils.<ref>{{Harvnb |Bucx|Marchand|Makaske|van de Guchte|2010|p=88}};{{Harvnb|Tessler|Vörösmarty|Grossberg|Gladkova|2015|p=638}}</ref> In many deltas this results in subsidence ranging from several millimeters per year up to possibly 25 centimeters per year in parts of the Ciliwung delta ([[Jakarta]]).<ref>{{Harvnb |Bucx|Marchand|Makaske|van de Guchte|2010|p=81}}</ref> Total anthropogenic-caused subsidence in the [[Rhine-Meuse-Scheldt delta]] (Netherlands) is estimated at 3 to 4 meters, over nine meters in the [[Sacramento-San Joaquin River Delta]], and over ten feet in urban areas of the [[Mississippi River Delta]] ([[New Orleans]]).<ref>{{Harvnb |Bucx|Marchand|Makaske|van de Guchte|2010|pp=81, 88,90}}</ref>
== Effects ==
[[File:Major cities threatened by sea level rise.png|thumb|right|605x605px|Map of major cities of the world most vulnerable to sea level rise]]
[[File:TPSeaLevelRise1.gif|thumb|right|400px|Schematic animation of sea level rise in [[Taipei]], [[Taiwan]] and surrounding regions, in meters]]
[[File:TWSeaLevelRise1.gif|thumb|right|400px|Schematic animation of sea level rise in Taiwan and surrounding regions, in meters]]
{{further|Regional effects of global warming}}
The IPCC TAR WGII report (''Impacts, Adaptation Vulnerability'') notes that current and future climate change would be expected to have a number of impacts, particularly on [[coast]]al systems.<ref>{{Harvnb|IPCC TAR WG1|2001}}.{{page needed|date=October 2011}}</ref> Such impacts may include increased [[coastal erosion]], higher [[storm surge|storm-surge]] flooding, inhibition of [[primary production]] processes, more extensive coastal inundation, changes in surface [[water quality]] and groundwater characteristics, increased loss of property and coastal habitats, increased flood risk and potential loss of life, loss of non-monetary cultural resources and values, impacts on agriculture and [[aquaculture]] through decline in soil and water quality, and loss of tourism, recreation, and transportation functions.
There is an implication that many of these impacts will be detrimental—especially for the three-quarters of the world's poor who depend on agriculture systems.<ref>"Climate Shocks: Risk and Vulnerability in an Unequal World." Human Development report 2007/2008. hdr.undp.org/media/hdr_20072008_summary_english.pdf</ref> The report does, however, note that owing to the great diversity of coastal environments; regional and local differences in projected relative sea level and climate changes; and differences in the resilience and adaptive capacity of [[ecosystem]]s, sectors, and countries, the impacts will be highly variable in time and space.
The IPCC report of 2007 estimated that accelerated melting of the Himalayan ice caps and the resulting rise in sea levels would likely increase the severity of flooding in the short term during the rainy season and greatly magnify the impact of tidal storm surges during the cyclone season. A sea-level rise of just 400&nbsp;mm in the Bay of Bengal would put 11 percent of the Bangladesh's coastal land underwater, creating 7–10 million [[climate refugee]]s.
Sea level rise could also displace many shore-based populations: for example it is estimated that a sea level rise of just 200&nbsp;mm could make 740,000 people in Nigeria homeless.<ref>{{cite web | title=Nigeria in the Dilemma of Climate Change | author=Klaus Paehler | url=http://www.kas.de/proj/home/pub/33/2/dokument_id-11468/index.html |accessdate=2008-11-04}}</ref>
Future sea-level rise, like the recent rise, is not expected to be globally uniform. Some regions show a sea-level rise substantially more than the global average (in many cases of more than twice the average), and others a sea level fall.<ref>[http://www.grida.no/climate/ipcc_tar/wg1/432.htm ??], in {{Harvnb|IPCC TAR WG1|2001}}.{{verify source|date=September 2011}}</ref> However, models disagree as to the likely pattern of sea level change.<ref>[http://www.grida.no/climate/ipcc_tar/wg1/fig11-13.htm Fig. 11?],  in {{Harvnb|IPCC TAR WG1|2001}}.{{verify source|date=September 2011}}</ref>
=== Island nations ===
{{further|Alliance of Small Island States|Small Island Developing States}}
IPCC assessments suggest that deltas and small island states are particularly vulnerable to sea-level rise caused by both thermal expansion and increased ocean water.  Sea level changes have not yet been conclusively proven to have directly resulted in environmental, humanitarian, or economic losses to small island states, but the IPCC and other bodies have found this a serious risk scenario in coming decades.<ref>[http://rs.resalliance.org/2006/06/02/future-oceans-warming-up-rising-high-turning-sour/ The Future Oceans – Warming Up, Rising High, Turning Sour<!-- Bot generated title -->]</ref>
[[Maldives]], [[Tuvalu]], and other low-lying countries are among the areas that are at the highest level of risk. The UN's environmental panel has warned that, at current rates, sea level would be high enough to make the Maldives uninhabitable by 2100.<ref>{{cite web | author= Megan Angelo | title=Honey, I Sunk the Maldives: Environmental changes could wipe out some of the world's most well-known travel destinations | url=http://travel.yahoo.com/p-interests-27384279;_ylc=X3oDMTFxcWIyczFpBF9TAzI3MTYxNDkEX3MDMjcxOTQ4MQRzZWMDZnAtdG9kYXltb2QEc2xrA21hbGRpdmVzLTQtMjgtMDk- | date=1 May 2009}}</ref><ref>{{cite web | author= Kristina Stefanova | title=Climate refugees in Pacific flee rising sea  | url= http://www.washingtontimes.com/news/2009/apr/19/rising-sea-levels-in-pacific-create-wave-of-migran/ | date=19 April 2009}}</ref>
Many media reports have focused on the island nations of the Pacific, notably the Polynesian islands of [[Tuvalu]], which based on more severe flooding events in recent years, were thought to be "sinking" due to sea level rise.<ref>{{cite news| last=Levine| first= Mark|date=December 2002| title=Tuvalu Toodle-oo| publisher= Outside Magazine| url=http://www.outsideonline.com/adventure-travel/australia-pacific/Tuvalu-Toodle-oo.html| accessdate=2005-12-19}}</ref>  A scientific review in 2000 reported that based on [[University of Hawaii]] gauge data, Tuvalu had experienced a negligible increase in sea level of 0.07&nbsp;mm a year over the past two decades, and that the [[El Niño Southern Oscillation]] (ENSO) had been a larger factor in Tuvalu's higher tides in recent years.<ref name="autogenerated1">{{cite journal| last=Patel| first= Samir S.| date=April 5, 2006| title=A Sinking Feeling| journal=Nature| url=http://www.nature.com/nature/journal/v440/n7085/full/440734a.html| accessdate=2007-11-15|doi=10.1038/440734a| volume=440| pages=734–736}}</ref>  A subsequent study by John Hunter from the University of Tasmania, however, adjusted for ENSO effects and the movement of the gauge (which was thought to be sinking).  Hunter concluded that Tuvalu had been experiencing sea-level rise of about 1.2&nbsp;mm per year.<ref name="autogenerated1" /><ref>{{cite news| last=Hunter| first=J.A.| date=August 12, 2002| title=A Note on Relative Sea Level Rise at Funafuti, Tuvalu| url=http://staff.acecrc.org.au/~johunter/tuvalu.pdf|format=PDF}}</ref>  The recent more frequent flooding in Tuvalu may also be due to an erosional loss of land during and following the actions of 1997 cyclones Gavin, Hina, and Keli.<ref>{{cite news| last=Field| first= Michael J.|date=December 2001| title=Sea Levels Are Rising| publisher=Pacific Magazine| url=http://www.pacificislands.cc/pm122001/pmdefault.php?urlarticleid=0009| accessdate=2005-12-19 |archiveurl = https://web.archive.org/web/20051218040610/http://www.pacificislands.cc/pm122001/pmdefault.php?urlarticleid=0009|archivedate = 2005-12-18}}</ref>
A study conducted on the Jaluit Atoll, Marshall Islands demonstrated that significant geomorphologic events such as storms (i.e. Typhoon Ophelia in 1958) tend to have larger impacts on reef islands than the smaller-scale effects of sea level rise. These effects include the immediate erosion and subsequent regrowth process that may vary in length from decades to centuries, even resulting in land areas larger than pre-storm values. With an expected rise in the frequency and intensity of storms, they may become more significant in determining island shape and size than sea level rise.<ref>{{Cite journal|last=Ford|first=Murray R.|last2=Kench|first2=Paul S.|title=Spatiotemporal variability of typhoon impacts and relaxation intervals on Jaluit Atoll, Marshall Islands|url=http://www.crossref.org/iPage?doi=10.1130%2FG37402.1|journal=Geology|volume=44|issue=2|pages=159–162|doi=10.1130/g37402.1}}</ref>
In 2016 it was reported that five of the [[Solomon Islands]] had disappeared due to the combined effects of sea level rise and stronger trade winds that were pushing water into the Western Pacific.<ref>{{Cite web|url=https://www.newscientist.com/article/2087356-five-pacific-islands-vanish-from-sight-as-sea-levels-rise/?utm_source=NSNS&utm_medium=ILC&utm_campaign=webpush&cmpid=ILC%25257CNSNS%25257C2016-GLOBAL-webpush-SOLOMONS|title=Five Pacific islands vanish from sight as sea levels rise|last=Klein|first=Alice|website=New Scientist|language=en-US|access-date=2016-05-09}}</ref>
Besides the issues that flooding brings, such as soil salinisation, the island states themselves would also become dissolved over time, as the islands become uninhabitable or completely submerged by the sea. Once this happens, all rights on the surrounding area (sea) are removed. This area can be huge as rights extend to a radius of 224 nautical miles (414&nbsp;km) around the entire island state. Any resources, such as fossil oil, minerals and metals, within this area can be freely dug up by anyone and sold without needing to pay any commission to the (now dissolved) island state.<ref>{{cite book|trans_title=Sea borders and rising sea levels: international law considerations about the effects of rising sea levels on borders at sea: speech, pronounced with the acceptance of the post of professor in international law at the University of Utrecht on 13 April 1989 |title=Zeegrenzen en zeespiegelrijzing : volkenrechtelijke beschouwingen over de effecten van het stijgen van de zeespiegel op grenzen in zee : rede, uitgesproken bij de aanvaarding van het ambt van hoogleraar in het volkenrecht aan de Rijksuniversiteit te Utrecht op donderdag 13 april 1989 |author=Alfred Henry Adriaan Soons |year=1989 |publisher=Kluwers |language=Dutch |isbn=978-90-268-1925-4 }}</ref>
Options that have been proposed to assist island nations to [[Adaptation to global warming|adapt]] to rising sea level include abandoning islands, building dikes, and building upwards.<ref>{{cite web | title=Policy Implications of Sea Level Rise: The Case of the Maldives | work=Proceedings of the Small Island States Conference on Sea Level Rise.  November 14–18, 1989. [[Malé]], [[Republic of Maldives]].  Edited by Hussein Shihab | url=http://papers.risingsea.net/Maldives/Small_Island_States_3.html| accessdate=2007-01-12 }}</ref>
{{further|C40 Cities Climate Leadership Group}}
A study in the April, 2007 issue of ''Environment and Urbanization'' reports that 634 million people live in coastal areas within {{convert|30|ft|m}} of sea level. The study also reported that about two thirds of the world's cities with over five million people are located in these low-lying coastal areas. Future sea level rise could lead to potentially catastrophic difficulties for shore-based communities in the next centuries: for example, many major cities such as [[Venice]], [[London]], [[New Orleans]], and [[New York City]] already need storm-surge defenses, and would need more if the sea level rose, though they also face issues such as [[subsidence]].<ref>{{cite web|last=Jacobson|first=Rebecca|title=Engineers Consider Barriers to Protect New York From Another Sandy|url=http://www.pbs.org/newshour/rundown/2012/11/engineers-draw-barriers-to-protect-new-york-from-another-sandy.html|publisher=PBS|accessdate=26 November 2012}}</ref><ref>[http://www.grida.no/climate/ipcc_tar/wg1/index.htm ??], in {{Harvnb|IPCC TAR WG1|2001}}.{{verify source|date=September 2011}}</ref> However, modest increases in sea level are likely to be offset when cities adapt by constructing sea walls or through relocating.<ref>{{cite web|url=http://www.yaleclimateconnections.org/2013/10/ipccs-new-estimates-for-increased-sea-level-rise/|title=IPCC’s New Estimates for Increased Sea-Level Rise|year=2013|publisher=Yale}}</ref>
Re-insurance company [[Swiss Re]] estimates an economic loss for southeast [[Florida]] in 2030, of $33 billion from climate-related damages.<ref>{{cite web|url=https://news.yahoo.com/sea-rise-threatens-florida-coast-no-statewide-plan-151756531.html|title=Sea rise threatens Florida coast, but no statewide plan|date=10 May 2015|publisher=Yahoo}}</ref><ref>{{cite web|url=http://www.miamidade.gov/planning/library/presentations/2014-02-11-swiss-re-climate-change.pdf|format=pdf|title=Climate Change and resilience building: a reinsurer's perspective|publisher=Miamidade.gov|year=2014}}</ref> [[Miami]] has been listed as "the number-one most vulnerable city worldwide" in terms of potential damage to property from storm-related flooding and sea-level rise.<ref name=RS62013>{{cite news|title=Goodbye, Miami|url=http://www.rollingstone.com/politics/news/why-the-city-of-miami-is-doomed-to-drown-20130620|accessdate=June 21, 2013|newspaper=Rolling Stone|date=June 20, 2013|author=Jeff Goodell|quote=The Organization for Economic Co-operation and Development lists Miami as the number-one most vulnerable city worldwide in terms of property damage, with more than $416 billion in assets at risk to storm-related flooding and sea-level rise.}}</ref>
Coastal and Polar habitats are facing drastic changes as consequence of rising sea levels. Loss of ice in the Arctic may force local species to migrate in search of a new home. If seawater continues to approach inland, problems related to contaminated soils and flooded wetlands may occur. Also, fish, birds, and coastal plants could lose parts of their habitat.<ref>[http://ocean.nationalgeographic.com/ocean/critical-issues-sea-level-rise/ "Sea Level Rise" National Geographic.]</ref> In 2016 it was reported that the [[Bramble Cay melomys]], which lived on a [[Great Barrier Reef]] island, had probably become extinct because of sea level rises.<ref>{{Cite web|url=http://www.australiangeographic.com.au/news/2016/06/extinct-bramble-cay-melomys|title=Extinct: Bramble Cay melomys|last=Smith|first=Lauren|date=2016-06-15|website=Australian Geographic|access-date=2016-06-17}}</ref>
===Extreme sea level rise events===
Downturn of [[Atlantic meridional overturning circulation]] (AMOC), has been tied to extreme regional sea level rise (1-in-850 year event). Between 2009–2010, coastal sea levels north of New York City increased by 128&nbsp;mm within two years. This jump is unprecedented in the [[tide gauge]] records, which have collected data for a couple of centuries.<ref>{{cite news|url=http://www.usclivar.org/research-highlights/extreme-sea-level-rise-event-linked-amoc-downturn|title=Extreme sea level rise event linked to AMOC downturn|date=March 25, 2015|publisher=CLIVAR|author1=Jianjun Yin  |author2=Stephen Griffies |lastauthoramp=yes }}</ref><ref>{{cite journal|url=http://www.nature.com/ncomms/2015/150224/ncomms7346/full/ncomms7346.html|title=An extreme event of sea-level rise along the Northeast coast of North America in 2009–2010|journal=Nature Communications|date=24 February 2015|authors=Paul B. Goddard, Jianjun Yin, Stephen M. Griffies & Shaoqing Zhang|doi=10.1038/ncomms7346|volume=6|pages=6346|pmid=25710720}}</ref>
== Sea level measurement ==
[[Image:TOPEX-JasonSeries2008.jpg|250px|thumb|right|Jason-1 continues the same sea surface measurements begun by TOPEX/Poseidon. It will be followed by the Ocean Surface Topography Mission on Jason-2 and by a planned future Jason-3]]
[[File:NOAA sea level trend 1993 2010.png|250px|thumb|right|1993–2012 Sea level trends from [[satellite altimetry]]]]
In 1992 the [[TOPEX/Poseidon]] satellite was launched to record the change in sea level.<ref>{{cite web | url = http://sealevel.jpl.nasa.gov/missions/topex/ | title = Ocean Surface Topography from Space | publisher = NASA/JPL}}</ref> Current rates of sea level rise from [[satellite altimetry]] have been estimated in the range of 2.9–3.4 ± 0.4–0.6&nbsp;mm per year for 1993–2010.<ref name="Nerem_2010">
{{cite journal
  | doi=10.1080/01490419.2010.491031
  | title=Estimating Mean Sea Level Change from the TOPEX and Jason Altimeter Missions
  | year=2010
  | author=Nerem
  | journal=Marine Geodesy
  | volume=33
  | pages=435–446
  | author2=R. S.''
  | display-authors=2
  | last3=Choe
  | first3=C.
  | last4=Mitchum
  | first4=G. T.
  | ref=harv}}
</ref><ref name="sealevel_cu">
{{cite web
| date=2011-07-19
| author=CUSLRG
| url = http://sealevel.colorado.edu/content/global-mean-sea-level-time-series-seasonal-signals-removed
| title = 2011_rel2: Global Mean Sea Level Time Series (seasonal signals removed)
| publisher = CU Sea Level Research Group (CUSLRG). Colorado Center for Astrodynamics Research at the University of Colorado at Boulder
| accessdate = 2011-02-10}}
</ref><ref name="sealevel_aviso">
{{cite web
| author=CNES/CLS
| year=2011
| url = http://www.aviso.oceanobs.com/en/news/ocean-indicators/mean-sea-level/index.html
| title = AVISO Global Mean Sea Level Estimate
| publisher = ''[[Centre National d'Etudes Spatiales]]''/''Collecte Localisation Satellites'' (CNES/CLS): Archiving, Validation and Interpretation of Satellite Oceanographic data (AVISO)
| accessdate = 2011-07-29}}
</ref><ref name="sealevel_csiro">{{cite web
| author=White, N.
| date=2011-07-29
| url = http://www.cmar.csiro.au/sealevel/sl_hist_last_15.html
| title = CSIRO Global Mean Sea Level Estimate
| publisher = Commonwealth Scientific and Industrial Research Organisation (CSIRO) / Wealth from Oceans National Research Flagship and the Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC)
| accessdate = 2011-07-29}}
</ref><ref name="sealevel_noaa">
{{cite web
| author=LSA
| date=2011-03-16
| url = http://www.star.nesdis.noaa.gov/sod/lsa/SeaLevelRise/LSA_SLR_timeseries_global.php
| title = Laboratory for Satellite Altimetry / Sea level rise
| publisher = [[National Oceanic and Atmospheric Administration|NOAA]]: National Environmental Satellite, Data, and Information Service (NESDIS), Satellite Oceanography and Climatology Division, Laboratory for Satellite Altimetry (LSA)
| accessdate = 2011-07-29}}</ref><ref name="sealevel_noaa"/> This exceeds those from tide gauges. It is unclear whether this represents an increase over the last decades; variability; true differences between satellites and tide gauges; or problems with satellite [[calibration]].<ref name="grida_a">{{cite web|url=http://www.grida.no/climate/ipcc_tar/wg1/426.htm|author=IPCC AR3|title=Mean sea level change from satellite altimeter observations}}</ref> Due to calibration errors of the first satellite – Topex/Poseidon, sea levels have been slightly overestimated until 2015, which resulted in masking of ongoing sea level rise acceleration.<ref>{{cite web|url=http://www.newscientist.com/article/dn27497-apparent-slowing-of-sea-level-rise-is-artefact-of-satellite-data.html#.VVE7uPmqpBc|title=Apparent slowing of sea level rise is artefact of satellite data|date=11 May 2015|author=Michael Le Page}}</ref>
===Tide gauge===
The longest running sea-level measurements, NAP or [[Amsterdam Ordnance Datum]] established in 1675, are recorded in [[Amsterdam]], [[the Netherlands]]. About 25 percent of the Netherlands lies beneath sea level, while more than 50 percent of this nation's area would be inundated by temporary floods if it did not have an extensive levee system, see [[Flood control in the Netherlands]].<ref>{{cite web|url=http://www.psmsl.org/data/longrecords/|title=Other Long Records not in the PSMSL Data Set|accessdate=11 May 2015|publisher=PSMSL}}</ref>
In [[Australia]], data collected by the [[Commonwealth Scientific and Industrial Research Organisation]] (CSIRO) show the current global mean sea level trend to be 3.2&nbsp;mm/yr.,<ref>{{cite web|title=Historical Sea Level Changes|url=http://www.cmar.csiro.au/sealevel/sl_hist_last_15.html|publisher=CSIRO|accessdate=25 April 2013}}</ref> a doubling of the rate of the total increase of about 210mm that was measured from 1880 to 2009, which reflected an average annual rise over the entire 129-year period of about 1.6&nbsp;mm/year.<ref>{{cite web|last=Neil|first=White|title=Historical Sea Level Changes|url=http://www.cmar.csiro.au/sealevel/sl_hist_few_hundred.html|publisher=CSIRO|accessdate=25 April 2013}}</ref>
Australian record collection has a long time horizon, including measurements by an amateur meteorologist beginning in 1837 and measurements taken from a sea-level benchmark struck on a small cliff on the Isle of the Dead<ref>{{cite journal|last=Hunter|first=John|author2=R. Coleman |author3=D. Pugh |title=The Sea Level at Port Arthur, Tasmania, from 1841 to the Present|journal=Geophysical Research Letters|date=April 2003|volume=30|issue=7|doi=10.1029/2002GL016813|bibcode = 2003GeoRL..30.1401H }}</ref> near the Port Arthur convict settlement on 1 July 1841.  These records, when compared with data recorded by modern tide gauges, reinforce the recent comparisons of the historic sea level rise of about 1.6&nbsp;mm/year, with the sharp acceleration in recent decades.<ref>{{cite press release
|title=Landmark study confirms rising Australian sea level
|publisher=CSIRO Marine and Atmospheric Research
|accessdate=2012-07-19 }}</ref>
Continuing extensive sea level data collection by Australia's [[Commonwealth Scientific and Industrial Research Organisation|(CSIRO)]] is summarized in its finding of mean sea level trend to be 3.2&nbsp;mm/yr.  As of 2003 the National Tidal Centre of the Bureau of Meteorology managed 32 tide gauges covering the entire Australian coastline, with some measurements available starting in 1880.<ref>{{cite web
|title=Australian Mean Sea Level Survey
|author=National Tidal Centre
|publisher=Australian Government [[Bureau of Meteorology]]
|accessdate=2010-12-18 }}</ref>
====United States====
[[File:U. S. Sea Level Trends 1900-2003.gif|thumb|250px|US sea-level trends 1900–2003]]
Tide gauges in the United States reveal considerable variation because some land areas are rising and some are sinking. For example, over the past 100 years, the rate of sea level rise varied from about an increase of {{convert|0.36|in|mm}} per year along the Louisiana Coast (due to land sinking), to a drop of a few inches per decade in parts of Alaska (due to [[post-glacial rebound]]). The rate of sea level rise increased during the 1993–2003 period compared with the longer-term average (1961–2003), although it is unclear whether the faster rate reflected a short-term variation or an increase in the long-term trend.<ref>{{cite web | title=Sea Level Changes| url=http://www.epa.gov/climatechange/science/recentslc.html | publisher=[[United States Environmental Protection Agency]] | accessdate=Jan 5, 2012}}</ref>
One study showed no acceleration in sea level rise in US tide gauge records during the 20th century.<ref>{{Cite journal | last1 = Houston | first1 = J. R. | last2 = Dean | first2 = R. G. | doi = 10.2112/JCOASTRES-D-10-00157.1 | title = Sea-Level Acceleration Based on U.S. Tide Gauges and Extensions of Previous Global-Gauge Analyses | url=http://www.jcronline.org/doi/pdf/10.2112/JCOASTRES-D-10-00157.1| journal = Journal of Coastal Research | volume = 27 | pages = 409–417 | year = 2011 | pmid =  | pmc = }}</ref> However, another study found that the rate of rise for the US Atlantic coast during the 20th century was far higher than during the previous two thousand years.<ref>{{Cite journal | last1 = Kemp | first1 = A. C. | last2 = Horton | first2 = B. P. | last3 = Donnelly | first3 = J. P. | last4 = Mann | first4 = M. E. | authorlink4=Michael E. Mann| last5 = Vermeer | first5 = M. | last6 = Rahmstorf | first6 = S.| authorlink6=Stefan Rahmstorf| doi = 10.1073/pnas.1015619108 | title = Climate related sea-level variations over the past two millennia | journal = Proceedings of the National Academy of Sciences | url=http://www.pnas.org/content/108/27/11017.full.pdf| volume = 108 | issue = 27 | pages = 11017–11022 | year = 2011 | pmid =  21690367| pmc = 3131350| ref=harv}}</ref>
{{further|Adaptation to global warming}}
In 2008, the Dutch ''Delta Commission'' ([[:nl:Deltacommissie (2007)|Deltacommissie]]), advised in a report that the Netherlands would need a massive new building program to strengthen the country's water defenses against the anticipated [[effects of global warming]] for the next 190 years. This commission was created in September 2007, after the damage caused by [[Hurricane Katrina]] prompted reflection and preparations. Those included drawing up worst-case plans for evacuations. The plan included more than €100 billion (US$144 bn), in new spending through the year 2100 to take measures, such as broadening coastal [[dunes]] and strengthening sea and river [[Dyke (construction)|dikes]]. The commission said the country must plan for a rise in the North Sea up to {{convert|1.3|m}} by 2100, rather than the previously projected {{convert|0.80|m}}, and plan for a 2–4 metre (6.5–13 feet) rise by 2200.<ref>[https://www.nytimes.com/2008/09/03/news/03iht-03dutch.15877468.html "Dutch draw up drastic measures to defend coast against rising seas"]</ref>
The [[New York City Panel on Climate Change]] (NPCC), is an effort to prepare the New York City area for climate change.
[[Miami Beach]] is spending $500 million in the next years to address sea-level rise. Actions include a pump drainage system, and to raise roadways and sidewalks.<ref>{{cite web|url=http://www.homelandsecuritynewswire.com/dr20150406-500-million-5year-plan-to-help-miami-beach-withstand-sealevel-rise|title=$500 million, 5-year plan to help Miami Beach withstand sea-level rise|date=6 April 2015}}</ref>
== See also ==
{{Portal|Global warming|Energy|Renewable energy|Sustainable development|Environment}}
*[[Carbon cycle]]
*[[Coastal development hazards|Coastal development]]
*[[Coastal sediment supply]]
*[[Cold blob (North Atlantic)]]
*[[Effects of global warming on oceans]]
*[[Effects of climate change on island nations]]
*[[Islands First]]
*[[Marine transgression]]
*[[Standard sea level]]
== Notes ==
== References ==
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|editor1=Metz, B. |editor2=Davidson, O. |editor3=Swart, R. |editor4=Pan, J. |publisher = Cambridge University Press
|url = http://www.grida.no/publications/other/ipcc%5Ftar/?src=/climate/ipcc_tar/wg3/index.htm
|isbn = 0-521-80769-7
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== Further reading ==
*[https://www.nytimes.com/2018/02/23/climate/mapping-future-climate-risk.html "What Land Will Be Underwater in 20 Years? Figuring It Out Could Be Lucrative"]
<references group="note"/>
*{{cite web|title=Sea Level Rise Key Message|url=http://nca2014.globalchange.gov/report/our-changing-climate/sea-level-rise|website=Third National Climate Assessment|accessdate=25 June 2014}}
* {{cite journal |author1=Byravan, S. |author2=Rajan, S. C. | title=The ethical implications of sea-level rise due to climate change | journal=Ethics and International Affairs | volume=24 | year=2010 | pages=239–60 | doi=10.1111/j.1747-7093.2010.00266.x | issue=3 | ref=harv}}
* {{cite journal | author=[[Anny Cazenave|Cazenave, A.]]; Nerem, R. S. | title=Present-day sea level change: Observations and causes | journal=Rev. Geophys | volume=42 | year=2004 | pages=RG3001 | doi = 10.1029/2003RG000139 | bibcode=2004RvGeo..42.3001C | issue=3 | ref=harv}}
* {{cite book |author1=Emery, K.O. |author2=D. G. Aubrey  |lastauthoramp=yes | title=Sea levels, land levels, and tide gauges | location=New York | publisher=Springer-Verlag | year=1991 | isbn=0-387-97449-0}}
* {{cite web | title=Sea Level Variations of the United States 1854–1999 | work=NOAA Technical Report NOS CO-OPS 36 | url=http://co-ops.nos.noaa.gov/publications/techrpt36doc.pdf | accessdate=20 February 2005|format=PDF}}
* {{cite journal | author=Clark, P. U., Mitrovica, J. X., Milne, G. A. & Tamisiea | title=Sea-Level Fingerprinting as a Direct Test for the Source of Global Meltwater Pulse 1A | journal=Science | volume=295 | year=2002 | pages=2438–2441 | pmid=11896236 | issue=5564 | doi=10.1126/science.1069017|bibcode = 2002Sci...296..553B | ref=harv }}
* {{cite journal | author=Eelco J. Rohling, Robert Marsh, Neil C. Wells, Mark Siddall and Neil R. Edwards | title=Similar meltwater contributions to glacial sea level changes from Antarctic and northern ice sheets | journal=Nature | volume=430 | issue=August 26 | year=2004 | pages=1016–1021 |doi=10.1038/nature02859 | pmid=15329718|bibcode = 2004Natur.430.1016R | ref=harv }}
* {{cite journal | author=[[Walter Munk]] | title=Twentieth century sea level: An enigma | journal=Proceedings of the National Academy of Sciences| volume=99 | issue=10 | year=2002 | pages=6550–6555 | ref=harv | doi=10.1073/pnas.092704599 | pmid=12011419 | pmc=124440}}
* {{cite journal | author=Menefee, Samuel Pyeatt | title=Half Seas Over: The Impact of Sea Level Rise on International Law and Policy | journal=U.C.L.A. Journal of Environmental Law & Policy | volume=9 | issue= | year=1991 | pages=175–218 | ref=harv}}
* {{cite journal |author1=Laury Miller  |author2=Bruce C. Douglas  |lastauthoramp=yes | title=Mass and volume contributions to twentieth-century global sea level rise | journal=Nature | volume=428 | year=2004 | pages=406–409 | doi=10.1038/nature02309 | pmid=15042085 | issue=6981|bibcode = 2004Natur.428..406M | ref=harv }}
* {{cite journal |author1=Bruce C. Douglas  |author2=W. Richard Peltier  |lastauthoramp=yes | title=The Puzzle of Global Sea-Level Rise | url=http://www.aip.org/pt/vol-55/iss-3/p35.html | accessdate=24 March 2005 | journal=[[Physics Today]] | volume=55 | issue=3 | year=2002 | pages=35–41 | doi=10.1063/1.1472392  |archiveurl = http://web.archive.org/web/20050213165850/http://www.aip.org/pt/vol-55/iss-3/p35.html <!-- Bot retrieved archive --> |archivedate = 13 February 2005|bibcode = 2002PhT....55c..35D | ref=harv }}
* {{cite journal|author=B. C. Douglas|journal=J. Geophys. Res.| volume=7| issue=c8| page=12699| year=1992| title=Global sea level acceleration| doi=10.1029/92JC01133| bibcode=1992JGR....9712699D|ref=harv}}
* {{cite book |author=Warrick, R. A., C. L. Provost, M. F. Meier, J. Oerlemans, and P. L. Woodworth |chapter=Changes in sea level |editor=Houghton, John Theodore |title=Climate Change 1995: The Science of Climate Change |publisher=Cambridge University Press |location=Cambridge, UK |year=1996 |pages=359–405 |isbn=0-521-56436-0 }}
* {{cite journal|author1=R. Kwok |author2=J. C. Comiso |journal=Journal of Climate| volume=15| issue=5| pages=487–501| year=2002| title=Southern Ocean Climate and Sea Ice Anomalies Associated with the Southern Oscillation| url = http://rkwok.jpl.nasa.gov/publications/Kwok.2002c.JCL.pdf | doi=10.1175/1520-0442(2002)015<0487:SOCASI>2.0.CO;2|format=PDF|bibcode = 2002JCli...15..487K|issn=1520-0442|ref=harv }}
*  Colorado Center for Astrodynamics Research, "[http://sealevel.colorado.edu/ Mean Sea Level]"  Accessed December 19, 2005
* Fahnestock, Mark (December 4, 2004), "[http://www.spaceref.com/news/viewpr.html?pid=15611 Report shows movement of glacier has doubled speed]", [[University of New Hampshire]] press release.  Accessed December 19, 2005
*{{cite journal |author1 =Leuliette, E.W. |author2 =R.S. Nerem |author3 =G.T. Mitchum |title=Calibration of TOPEX/Poseidon and Jason Altimeter Data to Construct a Continuous Record of Mean Sea Level Change |journal=Marine Geodesy |volume=27 |issue=1–2 |year=2004 |ref=harv |doi=10.1080/01490410490465193 |pages=79–94}}
* National Snow and Ice Data Center (March 14, 2005), "[http://nsidc.org/sotc/sea_level.html Is Global Sea Level Rising?]".  Accessed December 19, 2005
* {{cite web | title=IPCC again | author=INQUA commission on Sea Level Changes and Coastal Evolution | url=http://www.pog.su.se/sea/HP-14.+IPCC-3.pdf  | accessdate=2004-07-25 |format=PDF |archiveurl = http://webarchive.loc.gov/all/20050416173758/http%3A//www%2Epog%2Esu%2Ese/sea/HP%2D14%2E%2520IPCC%2D3%2Epdf |archivedate = April 16, 2005 }}
* {{cite news | title=Independent Online Edition | url=http://news.independent.co.uk/world/environment/article301493.ece | accessdate=2005-12-19 | work=The Independent | location=London | first=Steve | last=Connor | date=2005-07-25}}
* {{cite web | title=Address by his Excellency Mr. Maumoon Abdul Gahoom, President of the Republic of Maldives, at thenineteenth special session of the United Nations General Assembly for the purpose of an overall review and appraisal of theimplementation of agenda 21 – June 24, 1997 | author=[[Maumoon Abdul Gayoom]] | url=http://www.un.int/maldives/ungass.htm | accessdate=2006-01-06 }}
* Pilkey, Orrin and Robert Young, ''The Rising Sea,'' Shearwater, July 2009 ISBN 978-1-59726-191-3
*{{cite journal|last=Douglas|first=Bruce C.|title=Global sea level change: Determination and interpretation|journal=[[Reviews of Geophysics]] |year=1995|volume=33|pages=1425–1432|doi=10.1029/95RG00355|bibcode = 1995RvGeo..33.1425D }}
== External links ==
{{Wikibooks|Historical Geology|Sea level variations}}
*[http://nca2014.globalchange.gov/report/our-changing-climate/sea-level-rise Third National Climate Assessment Sea Level Rise Key Message]
*{{cite web|url=http://sealevel.colorado.edu/|title=University of Colorado at Boulder Sea Level Change}}
*[http://www.csc.noaa.gov/digitalcoast/publications/slcScenarios Incorporating Sea Level Change Scenarios at the Local Level] Outlines eight steps a community can take to develop site-appropriate scenarios
*[http://www.sciencenews.org/view/generic/id/341723/title/East_Coast_faces_faster_sea_level_rise ''East Coast faces faster sea level rise; Cities from North Carolina to Massachusetts see waters rising more rapidly''] July 28, 2012; Vol.182 #2 (p.&nbsp;17) [[Science News]]
*[http://www.cmar.csiro.au/sealevel Sea Level Rise:Understanding the past – Improving projections for the future]
*[http://papers.ssrn.com/sol3/papers.cfm?abstract_id=950329 Providing new homes for climate exiles] Sujatha Byravan and Sudhir Chella Rajan, 2006
*[http://stephenschneider.stanford.edu/Publications/PDF_Papers/MornerEtAl2004.pdf New perspectives for the future of the Maldives] Nils-Axel Mörner, Michael Tooley, Göran Possnert, 2004
*{{cite web | title=Physical Agents of Land Loss: Relative Sea Level | work=An Overview of Coastal Land Loss: With Emphasis on the Southeastern United States |publisher=[[US Geological Survey]] | url=http://pubs.usgs.gov/of/2003/of03-337/global.html | accessdate=14 February 2005}}
*[http://www.gloss-sealevel.org/ The Global Sea Level Observing System (GLOSS)]
*[http://www.surgewatch.org/ Surgewatch, database for UK flood events]
* [http://harvardmagazine.com/2010/05/gravity-of-glacial-melt ''The Gravity of Glacial Melt. Jerry Mitrovica explains the uneven rise in sea levels as glaciers melt''] from ''Harvard Magazine''
;Maps that show a rise in sea levels:
*[http://www.csc.noaa.gov/slr Sea Level Rise and Coastal Flooding Impacts (NOAA)]
*{{cite web |url=http://tidesandcurrents.noaa.gov/sltrends/sltrends.shtml |title=Sea Level Trends (NOAA) |author=<!--Staff writer(s); no by-line.--> |date= |website=tidesandcurrents.noaa.gov |publisher=[[National Oceanic and Atmospheric Administration]] |access-date= |quote=}}
*{{YouTube|baGrtqyWSRM|Earth Under Water - Worldwide Flooding&#124;Sea Level Rise (SLR)}}
*{{YouTube|R_pb1G2wIoA|Six degrees could change the world}} – National Geographic film based on the 2007 book ''[[Six Degrees: Our Future on a Hotter Planet]]''
*{{YouTube|kDQDaXrYHFI|HD Earth Under Water - Full Documentary}} – [[Discovery Channel]]
{{physical oceanography|expanded=other}}
{{Global warming}}
{{DEFAULTSORT:Sea Level Rise}}
{{DEFAULTSORT:Sea Level Rise}}
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[[Category:Effects of global warming]]
[[Category:Effects of global warming]]
[[Category:Climate change]]
[[Category:Climate change]]

Latest revision as of 04:26, 13 January 2020

Map of the Earth with a six-meter sea level rise represented in red

Sea level is the most concrete and undeniable consequence of global warming. In the United States significant amounts of residential and commercial property lie in the path of predictable sea level rise, particularly in Boston and south Florida. Estimates of the amount of sea level rise by the turn of the 22nd Century range between 2 and 6 feet. The major cause of uncertainty in future projections is doubt about the amount of water which will result from melting of ice sheets.[1] In other parts of the word there are large densely-populated deltas which will be profoundly affected. Globally, dramatic effects have occurred in Venice and can be expected on the coast of Bangladesh


Sea level rise refers to an increase in the volume of water in the world’s oceans, resulting in an increase in global mean sea level. Sea level rise is usually attributed to global climate change by thermal expansion of the water in the oceans and by melting of Ice sheets and glaciers on land. Melting of floating ice shelves or icebergs at sea raises sea levels only slightly.

Sea level rise at specific locations may be more or less than the global average. Local factors might include tectonic effects, subsidence of the land, tides, currents, storms, etc. Sea level rise is expected to continue for centuries. Because of the slow inertia, long response time for parts of the climate system, it has been estimated that we are already committed to a sea-level rise of approximately 2.3 |ft for each degree Celsius of temperature rise within the next 2,000 years.[2] IPCC Summary for Policymakers, AR5, 2014, indicated that the global mean sea level rise will continue during the 21st century, very likely at a faster rate than observed from 1971 to 2010.[3] Projected rates and amounts vary. A January 2017 NOAA report suggests a range of GMSL rise of 0.3 – 2.5 m possible during the 21st century.[4]

Sea level rises can considerably influence human populations in coastal and island regions and natural environments like marine ecosystems.[5]