Greenland and Antarctic ice sheets
- The Greenland and Antarctic ice sheets are the largest bodies of ice in the world and play an important role in the global climate system. Both ice sheets have been losing large amounts of ice at an increasing rate since 1992.
- The cumulative ice loss from Greenland from 1992 to 2015 was 3 600 Gt and contributed to global sea level rise by approximately 10 mm; the corresponding figure for Antarctica is 1 500 Gt, which corresponds to approximately a 5 mm global sea level rise since 1992.
- Model projections suggest further declines of the polar ice sheets in the future, but the uncertainties are large. The melting of the polar ice sheets is estimated to contribute up to 50 cm of global sea level rise during the 21st century. Very long-term projections (until the year 3000) suggest potential sea level rise of several metres with continued melting of the ice sheets.
Are the Greenland and Antarctic ice sheets losing mass, and what is the effect on global sea level?
The mass balance of the polar ice sheets is affected by numerous factors, including changes in precipitation patterns over the ice sheets, snowfall, changes in the snowline, summer melting of snow, changes in ice sheet albedo, changes in the extent of supraglacial lakes, submarine melting of the floating ice shelves at the tongue of marine outlet glaciers, and icebergs breaking off of glaciers [i]. The changing balance between ice accumulation, on the one hand, and melting and sublimation of ice and snow, submarine melting and calving, on the other hand, determines the future development of the ice sheets. Both ice sheets have lost significant amounts of ice since 2005 (Figure 1).
Several different methods have been used to monitor the mass balance of the Greenland ice sheet. The overall conclusion of all available studies is that Greenland is losing mass (Figure 1). Average ice loss increased from 34 (uncertainty interval: –6 to 74) billion tonnes per year over the period 1992–2001 to 215 (157 to 274) billion tonnes per year over the period 2002–2011. In 2012, an exceptional loss estimated at more than 500 billion tonnes was recorded. From 1992 to 2012, the contribution to the global sea level has been estimated to have been approximately 8.0 mm (6.6 to 9.4 mm) [ii]. In 2013–2015, the net loss of ice was slower than in 2012, with a total of approximately 280 billion tonnes net loss over the period [iii].
In Greenland, the area subject to summer melt has increased significantly over recent decades [iv]. The increased melting has been attributed to changes in general circulation in summer, creating warmer conditions over Greenland [v]. Ice core data suggest that large-scale melting events such as the one observed in 2012 have occurred once every few hundred years on average, with previous ones in 1889 and in the 12th century. It is not currently possible to tell whether the frequency of these rare extensive melt events has changed [vi]. Another important process that may accelerate the loss of ice from the ice sheets is enhanced submarine melting of glaciers terminating in the sea. Its importance may be greater than previously assumed. The process has been documented for both the Greenland and the Antarctic ice sheets [vii].
East Antarctica had a slightly positive mass balance of +14 (–29 to +57) billion tonnes per year over the period 1992–2011, but, overall, the Antarctic ice sheet has lost on average approximately 70 billion tonnes of ice per year, as West Antarctica and the Antarctic Peninsula have lost 65 (39 to 91) and 20 (6 to 34) billion tonnes per year, respectively. The floating ice shelves have also become thinner [viii]. From 1992 to 2015, the ice loss of the Antarctic ice sheet has contributed approximately 5 mm (2 to 7 mm) to the global sea level [ix]. All in all, the ice sheets have contributed to about one-third of the total sea level rise since the 1990s [x]. A recent study of Antarctica suggests, however, that the snow accumulation has exceeded the mass loss from ice discharge, leading to the equivalent of an annual 0.23 mm sea level depletion between 2003 and 2008 [xi].
All recent studies indicate that the mass loss of the Greenland ice sheet will increase the global sea level, with greater radiative forcing leading to greater sea level rise. Recent studies suggest an upper bound of 16 cm of sea level rise from the Greenland ice sheet during the 21st century for a high emissions scenario and somewhat lower values for lower emissions scenarios [xii]. One recent study estimated that the Greenland ice sheet contribution until the year 3000 will be 1.4, 2.6 and 4.2 m for the emissions scenarios SRES B1, A1B and A2 (with stabilised greenhouse concentrations after 2100), respectively [xiii].
On multi-millennial time scales, the Greenland ice sheet shows threshold behaviour due to different feedback mechanisms. If a temperature above the threshold is maintained for an extended period, the melting of the Greenland ice sheet could self-amplify, which would eventually result in near-complete ice loss (equivalent to a sea level rise of about 7 m). Coupled climate–ice sheet models with a fixed topography (that do not consider the feedback between surface mass balance and the height of the ice sheet) estimate that the global mean surface air temperature threshold above which the Greenland ice will completely melt lies between 2 and 4 °C above pre-industrial levels [xiv]. In contrast, a study modelling the ice sheet dynamically suggests that the threshold could be as low as about 1 °C above pre-industrial levels [xv]. The complete loss of the Greenland ice sheet is not inevitable because it has a long time scale. Complete melting would take tens of millennia if near the threshold and a millennium or more for temperatures a few degrees above the threshold [xvi].
The uncertainties around future ice discharge from Antarctica, and the associated sea level rise, are larger than for Greenland. However, mass loss of the Antarctic ice sheet has a greater impact on the sea level in the Northern Hemisphere than a comparable loss of the Greenland ice sheet, owing to gravitational forces. A comprehensive analysis applying various climate, ocean and ice sheet models estimates that the additional ice loss for the 21st century is 7 cm (90 % range: 0–23 cm) of global sea level equivalent for a low emissions scenario (RCP2.6) and 9 cm (90 % range: 1–37 cm) for a high emissions scenario (RCP8.5) [xvii]. By 2100, the rise of global sea level will be clearly influenced by the development of the Antarctic ice sheet. A recent study suggests that the Antarctic ice sheet has the potential to contribute more than a metre to sea level rise by 2100 and more than 15 metres by 2500, if emissions continue unabated [xviii].
Several studies that were published after the release of the IPCC AR5 suggest that melting of the West Antarctic Ice Sheet (WAIS) has been accelerating recently and that a WAIS collapse is already inevitable and irreversible. There are also indications of instability in some parts of the much larger East Antarctic Ice Sheet. These new results suggest that the global mean sea level contribution from Antarctica alone could be several metres on a time scale of a few centuries to a millennium [xix].
The long-term development of the ice sheets is hugely important in determining the consequences of climate change. Amplifying feedback mechanisms, including slowdown of meridional overturning circulation, may accelerate ice sheet mass loss [xx]. A coupled ice sheet–ice shelf model suggests that, if atmospheric warming exceeds 1.5 to 2 °C above present, the major Antarctic ice shelves would collapse, which would trigger a centennial- to millennial-scale response of the Antarctic ice sheet and cause an unstoppable contribution to sea level rise [xxi]. Although current estimates of sea level rise by 2100 suggest that they will fall in a range of some tens of centimetres [xxii], collapsing ice sheets could, in the long term, result in a faster and greater rise in sea level than currently assumed, underlining the urgency of climate change mitigation [xxiii]. The uncertainties in the long-term projections are significant, however. Assumptions concerning, for example, bedrock uplift and sea surface drop associated with ice sheet retreat have a significant effect on the results with respect to sea level rise [xxiv].
[i] J. E. Box et al., ‘Greenland Ice Sheet Albedo Feedback: Thermodynamics and Atmospheric Drivers’,The Cryosphere 6, no. 4 (elokuu 2012): 821–39, doi:10.5194/tc-6-821-2012; I. M. Howat et al., ‘Brief Communication “Expansion of Meltwater Lakes on the Greenland Ice Sheet”’,The Cryosphere 7, no. 1 (helmikuu 2013): 201–4, doi:10.5194/tc-7-201-2013; Stephen J. Vavrus, ‘Extreme Arctic Cyclones in CMIP5 Historical Simulations’,Geophysical Research Letters 40, no. 23 (joulukuu 2013): 6208–12, doi:10.1002/2013GL058161; Liane G. Benning et al., ‘Biological Impact on Greenland’s Albedo’,Nature Geoscience 7, no. 10 (lokakuu 2014): 691–691, doi:10.1038/ngeo2260.
[ii] Peter U. Clark et al., ‘Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change’,Current Climate Change Reports 1, no. 4 (10 October 2015): 224–46, doi:10.1007/s40641-015-0024-4.
[iii] DMI, GEUS, and DTU Space, ‘Polar Portal. Greenland — Total Mass Change’,Http://Polarportal.dk/En/Groenlands-Indlandsis/Nbsp/Total-Masseaendring/, 2015, http://polarportal.dk/en/groenlands-indlandsis/nbsp/total-masseaendring/.
[iv] X. Fettweis et al., ‘Melting Trends over the Greenland Ice Sheet (1958–2009) from Spaceborne Microwave Data and Regional Climate Models’,The Cryosphere 5, no. 2 (2011): 359–75, doi:10.5194/tc-5-359-2011; D. G. Vaughan et al., ‘Observations: Cryosphere’, inClimate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, ed. T. F. Stocker et al. (Cambridge; New York: Cambridge University Press, 2013), 317–82, http://www.climatechange2013.org/images/report/WG1AR5_Chapter04_FINAL.pdf.
[v] X. Fettweis et al., ‘Brief communication “Important Role of the Mid-Tropospheric Atmospheric Circulation in the Recent Surface Melt Increase over the Greenland Ice Sheet”’,The Cryosphere 7, no. 1 (helmikuu 2013): 241–48, doi:10.5194/tc-7-241-2013.
[vi] S. V. Nghiem et al., ‘The Extreme Melt across the Greenland Ice Sheet in 2012’,Geophysical Research Letters 39, no. 20 (2012): L20502, doi:10.1029/2012GL053611; M. Tedesco et al., ‘Evidence and Analysis of 2012 Greenland Records from Spaceborne Observations, a Regional Climate Model and Reanalysis Data’,The Cryosphere 7, no. 2 (4 April 2013): 615–30, doi:10.5194/tc-7-615-2013.
[vii] B. Wouters et al., ‘Dynamic Thinning of Glaciers on the Southern Antarctic Peninsula’,Science 348, no. 6237 (22 May 2015): 899–903, doi:10.1126/science.aaa5727.
[viii] Fernando S. Paolo, Helen A. Fricker, and Laurie Padman, ‘Volume Loss from Antarctic Ice Shelves Is Accelerating’,Science 348, no. 6232 (17 April 2015): 327–31, doi:10.1126/science.aaa0940.
[ix] Clark et al., ‘Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change’.
[x] Andrew Shepherd et al., ‘A Reconciled Estimate of Ice-Sheet Mass Balance’,Science 338, no. 6111 (30 November 2012): 1183–89, doi:10.1126/science.1228102; V. R. Barletta, L. S. Sørensen, and R. Forsberg, ‘Scatter of Mass Changes Estimates at Basin Scale for Greenland and Antarctica’,The Cryosphere 7, no. 5 (syyskuu 2013): 1411–32, doi:10.5194/tc-7-1411-2013; Vaughan et al., ‘Observations: Cryosphere’; V. Helm, A. Humbert, and H. Miller, ‘Elevation and Elevation Change of Greenland and Antarctica Derived from CryoSat-2’,The Cryosphere 8, no. 4 (20 August 2014): 1539–59, doi:10.5194/tc-8-1539-2014.
[xi] H. Jay Zwally et al., ‘Mass Gains of the Antarctic Ice Sheet Exceed Losses’,Journal of Glaciology 61, no. 230 (15 December 2015): 1019–36, doi:10.3189/2015JoG15J071.
[xii] J. A. Church et al., ‘Sea-Level Change’, inClimate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, ed. T. F. Stocker et al. (Cambridge; New York: Cambridge University Press, 2013), 1137–1216, http://www.climatechange2013.org/images/report/WG1AR5_Chapter13_FINAL.pdf; J. J. Fürst, H. Goelzer, and P. Huybrechts, ‘Ice-Dynamic Projections of the Greenland Ice Sheet in Response to Atmospheric and Oceanic Warming’,The Cryosphere 9, no. 3 (toukokuu 2015): 1039–62, doi:10.5194/tc-9-1039-2015.
[xiii] H. Goelzer et al., ‘Millennial Total Sea-Level Commitments Projected with the Earth System Model of Intermediate Complexity LOVECLIM’,Environmental Research Letters 7, no. 4 (1 December 2012): 045401, doi:10.1088/1748-9326/7/4/045401; Church et al., ‘Sea-Level Change’.
[xiv] J. G. L. Rae et al., ‘Greenland Ice Sheet Surface Mass Balance: Evaluating Simulations and Making Projections with Regional Climate Models’,The Cryosphere 6, no. 6 (9 November 2012): 1275–94, doi:10.5194/tc-6-1275-2012; Church et al., ‘Sea-Level Change’; X. Fettweis et al., ‘Estimating Greenland Ice Sheet Surface Mass Balance Contribution to Future Sea Level Rise Using the Regional Atmospheric Climate Model MAR’,The Cryosphere 7 (2013): 268–489, doi:10.5194/tc-7-469-2013; Miren Vizcaino et al., ‘Coupled Simulations of Greenland Ice Sheet and Climate Change up to A.D. 2300: GRIS and Climate Change up to AD 2300’,Geophysical Research Letters 42, no. 10 (May 2015): 3927–35, doi:10.1002/2014GL061142.
[xv] Alexander Robinson, Reinhard Calov, and Andrey Ganopolski, ‘Multistability and Critical Thresholds of the Greenland Ice Sheet’,Nature Climate Change 2, no. 6 (June 2012): 429–32, doi:10.1038/nclimate1449.
[xvi] Robinson, Calov, and Ganopolski, ‘Multistability and Critical Thresholds of the Greenland Ice Sheet’; Church et al., ‘Sea-Level Change’; Patrick J. Applegate et al., ‘Increasing Temperature Forcing Reduces the Greenland Ice Sheet’s Response Time Scale’,Climate Dynamics 45 (2015): 2001–11, doi:10.1007/s00382-014-2451-7.
[xvii] A. Levermann et al., ‘Projecting Antarctic Ice Discharge Using Response Functions from SeaRISE Ice-Sheet Models’,Earth System Dynamics 5, no. 2 (14 August 2014): 271–93, doi:10.5194/esd-5-271-2014.
[xviii] Robert M. DeConto and David Pollard, ‘Contribution of Antarctica to Past and Future Sea-Level Rise’,Nature 531, no. 7596 (30 March 2016): 591–97, doi:10.1038/nature17145.
[xix] L. Favier et al., ‘Retreat of Pine Island Glacier Controlled by Marine Ice-Sheet Instability’,Nature Climate Change 4, no. 2 (February 2014): 117–21, doi:10.1038/nclimate2094; B. C. Gunter et al., ‘Empirical Estimation of Present-Day Antarctic Glacial Isostatic Adjustment and Ice Mass Change’,The Cryosphere 8, no. 2 (28 April 2014): 743–60, doi:10.5194/tc-8-743-2014; Ian Joughin, Benjamin E. Smith, and Brooke Medley, ‘Marine Ice Sheet Collapse Potentially under Way for the Thwaites Glacier Basin, West Antarctica’,Science 344, no. 6185 (16 May 2014): 735–38, doi:10.1126/science.1249055; Malcolm McMillan et al., ‘Increased Ice Losses from Antarctica Detected by CryoSat-2’,Geophysical Research Letters 41, no. 11 (16 June 2014): 2014GL060111, doi:10.1002/2014GL060111; M. Mengel and A. Levermann, ‘Ice Plug Prevents Irreversible Discharge from East Antarctica’,Nature Climate Change 4, no. 6 (4 May 2014): 451–55, doi:10.1038/nclimate2226; J. Mouginot, E. Rignot, and B. Scheuchl, ‘Sustained Increase in Ice Discharge from the Amundsen Sea Embayment, West Antarctica, from 1973 to 2013’,Geophysical Research Letters 41, no. 5 (16 March 2014): 1576–84, doi:10.1002/2013GL059069; E. Rignot et al., ‘Widespread, Rapid Grounding Line Retreat of Pine Island, Thwaites, Smith, and Kohler Glaciers, West Antarctica, from 1992 to 2011’,Geophysical Research Letters 41, no. 10 (28 May 2014): 3502–9, doi:10.1002/2014GL060140; P. R. Holland et al., ‘Oceanic and Atmospheric Forcing of Larsen C Ice-Shelf Thinning’,The Cryosphere 9, no. 3 (13 May 2015): 1005–24, doi:10.5194/tc-9-1005-2015.
[xx] J. Hansen et al., ‘Ice Melt, Sea Level Rise and Superstorms: Evidence from Paleoclimate Data, Climate Modeling, and Modern Observations That 2 °C Global Warming Is Highly Dangerous’,Atmospheric Chemistry and Physics Discussions 15, no. 14 (23 July 2015): 20059–179, doi:10.5194/acpd-15-20059-2015.
[xxi] N. R. Golledge et al., ‘The Multi-Millennial Antarctic Commitment to Future Sea-Level Rise’,Nature 526, no. 7573 (lokakuu 2015): 421–25, doi:10.1038/nature15706.
[xxii] Clark et al., ‘Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change’.
[xxiii] EASAC, ‘Facing Critical Decisions on Climate Change in 2015’ (Halle (Saale): European Academies’ Scientific Advisory Council, October 2015), http://www.easac.eu/fileadmin/PDF_s/reports_statements/Easac_15_COP21_web.pdf; Golledge et al., ‘The Multi-Millennial Antarctic Commitment to Future Sea-Level Rise’; Hansen et al., ‘Ice Melt, Sea Level Rise and Superstorms’.
[xxiv] Natalya Gomez, David Pollard, and David Holland, ‘Sea-Level Feedback Lowers Projections of Future Antarctic Ice-Sheet Mass Loss’,Nature Communications 6 (10 November 2015): 8798, doi:10.1038/ncomms9798; Hannes Konrad et al., ‘Potential of the Solid-Earth Response for Limiting Long-Term West Antarctic Ice Sheet Retreat in a Warming Climate’,Earth and Planetary Science Letters 432 (December 2015): 254–64, doi:10.1016/j.epsl.2015.10.008.
Indicator specification and metadata
- Cumulative ice mass loss and sea-level equivalent from Greenland
- Gigatonnes (Gt)
Policy context and targets
In April 2013, the European Commission (EC) presented the EU Adaptation Strategy Package. This package consists of the EU Strategy on adaptation to climate change (COM/2013/216 final) and a number of supporting documents. The overall aim of the EU Adaptation Strategy is to contribute to a more climate-resilient Europe.
One of the objectives of the EU Adaptation Strategy is Better informed decision-making, which will be achieved by bridging the knowledge gap and further developing the European climate adaptation platform (Climate-ADAPT) as the ‘one-stop shop’ for adaptation information in Europe. Climate-ADAPT has been developed jointly by the EC and the EEA to share knowledge on (1) observed and projected climate change and its impacts on environmental and social systems and on human health, (2) relevant research, (3) EU, transnational, national and subnational adaptation strategies and plans, and (4) adaptation case studies.
Further objectives include Promoting adaptation in key vulnerablesectors through climate-proofing EU sector policies and Promoting action by Member States. Most EU Member States have already adopted national adaptation strategies and many have also prepared action plans on climate change adaptation. The EC also supports adaptation in cities through the Covenant of Mayors for Climate and Energy initiative.
In September 2016, the EC presented an indicative roadmap for the evaluation of the EU Adaptation Strategy by 2018.
In November 2013, the European Parliament and the European Council adopted the 7th EU Environment Action Programme (7th EAP) to 2020, ‘Living well, within the limits of our planet’. The 7th EAP is intended to help guide EU action on environment and climate change up to and beyond 2020. It highlights that ‘Action to mitigate and adapt to climate change will increase the resilience of the Union’s economy and society, while stimulating innovation and protecting the Union’s natural resources.’ Consequently, several priority objectives of the 7th EAP refer to climate change adaptation.
No targets have been specified.
Related policy documents
7th Environment Action Programme
DECISION No 1386/2013/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 20 November 2013 on a General Union Environment Action Programme to 2020 ‘Living well, within the limits of our planet’. In November 2013, the European Parliament and the European Council adopted the 7 th EU Environment Action Programme to 2020 ‘Living well, within the limits of our planet’. This programme is intended to help guide EU action on the environment and climate change up to and beyond 2020 based on the following vision: ‘In 2050, we live well, within the planet’s ecological limits. Our prosperity and healthy environment stem from an innovative, circular economy where nothing is wasted and where natural resources are managed sustainably, and biodiversity is protected, valued and restored in ways that enhance our society’s resilience. Our low-carbon growth has long been decoupled from resource use, setting the pace for a safe and sustainable global society.’
Climate-ADAPT: Mainstreaming adaptation in EU sector policies
Overview of EU sector policies in which mainstreaming of adaptation to climate change is ongoing or explored
Climate-ADAPT: National adaptation strategies
Overview of activities of EEA member countries in preparing, developing and implementing adaptation strategies
DG CLIMA: Adaptation to climate change
Adaptation means anticipating the adverse effects of climate change and taking appropriate action to prevent or minimise the damage they can cause, or taking advantage of opportunities that may arise. It has been shown that well planned, early adaptation action saves money and lives in the future. This web portal provides information on all adaptation activities of the European Commission.
EU Adaptation Strategy Package
In April 2013, the European Commission adopted an EU strategy on adaptation to climate change, which has been welcomed by the EU Member States. The strategy aims to make Europe more climate-resilient. By taking a coherent approach and providing for improved coordination, it enhances the preparedness and capacity of all governance levels to respond to the impacts of climate change.
Methodology for indicator calculation
For the estimation of the polar ice sheets mass balance, an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment has been used.
Methodology for gap filling
- Shepherd et al. (2012): A reconciled estimate of ice-sheet mass balance. Shepherd, A., Ivins, E. R., A, G., Barletta, V. R., Bentley, M. J., Bettadpur, S., Briggs, K. H., Bromwich, D. H., Forsberg, R., Galin, N., Horwath, M., Jacobs, S., Joughin, I., King, M. A., Lenaerts, J. T. M., Li, J., Ligtenberg, S. R. M., Luckman, A., Luthcke, S. B. et al., 2012, 'A reconciled estimate of ice-sheet mass balance',Science338(6111), 1183–1189 (DOI: 10.1126/science.1228102).
Data sets uncertainty
Data on the cryosphere vary significantly with regard to availability and quality. Snow and ice cover have been monitored globally since satellite measurements started in the 1970s. Improved technology allows for more detailed observations and observations of a higher resolution. Direct historical area-wide data on the Greenland and Antarctic ice sheets cover about 20 years, but reconstructions give a 200 000-year perspective.
Continuous efforts are being made to improve knowledge of the cryosphere. Scenarios for the future development of key components of the cryosphere have recently become available from the CMIP5 project, which has provided climate change projections for the IPCC AR5. Owing to their economic importance, considerable efforts have also been devoted to improving real-time monitoring of snow cover and sea ice.
A reconciled estimate of ice-sheet mass balance (dataset URL is not available)
provided by University of Leeds
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
- CLIM 009
Contacts and ownership
EEA Contact InfoHans-Martin Füssel
EEA Management Plan2016 1.4.1 (note: EEA internal system)
Frequency of updates
For references, please go to http://www.eea.europa.eu/data-and-maps/indicators/greenland-ice-sheet-3/assessment or scan the QR code.
PDF generated on 27 Mar 2017, 06:11 AM