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Indicator Assessment
Cumulative ice mass loss from Greenland and Antarctica
Note: The figure shows the cumulative ice mass loss from the Greenland and Antarctic ice sheets from recent studies, weighted according to the primary satellite data source following the approach of the Ice Sheet Mass Balance Inter-comparison Exercise (The IMBIE team, 2018, doi:10.1038/s41586-018-0179-y; The IMBIE team, 2019, doi:10.1038/s41586-019-1855-2). The shaded uncertainty intervals are estimated from the standard deviation of the individual studies.
Past trends
The mass balance of the polar ice sheets is affected by numerous factors, including changes in precipitation patterns over the ice sheets, 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. 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 [i].
Figure 1 shows that both the Greenland and the Antarctic ice sheet have lost significant amounts of ice at a rapidly increasing rate since the 1990s. Mass losses over the decade 2007-2016 have doubled for the Greenland ice sheet and more than tripled for the Antarctic ice sheet, compared to the previous decade 1997-2006. The ice sheets have contributed about one-third of the total sea level rise since the 1990s [ii].
The Greenland ice sheet has been gaining mass in the 1970s, but experienced mass losses at an increasing rate since the 1980s [iii]. The cumulative ice mass loss from 1992 to 2017 was 3 900 (uncertainty interval: ±350) billion tonnes, corresponding to a contribution to global sea level rise of 10.6 (± 0.9) mm [iv]. The largest loss has been recorded for 2012, and a shorter extreme melt period was observed in July 2019 [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 [vi].
The mass of the East Antarctic ice sheet, covering 85% of the whole Antarctic ice sheet, has remained largely unchanged over the satellite period (since 1992), yet with large interannual variability and large uncertainties. However, the Antarctic ice sheet overall has lost 2 600 (± 560) billion tonnes of ice during 1992-2017, mostly due to thinning and retreat of major outlet glaciers draining the West Antarctic ice sheet and mass losses of the Antarctic Peninsula ice sheet. The floating ice shelves have also become thinner. This corresponds to a contribution of approximately 7.4 (± 1.6) mm to the global sea level rise [vii].
Recently observed processes that may accelerate the loss of ice from the ice sheets include enhanced submarine melting of glaciers terminating in the sea and increased meltwater runoff due to rapidly expanding ice slabs [viii].
Projections
All studies indicate that the Greenland and Antarctic ice sheets will continue to lose mass at an increasing rate during the 21st century, thereby contributing further to global sea level rise. The uncertainties around future ice discharge from Antarctica, and the associated sea level rise, are larger than for Greenland. 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. The sea level rise contribution of the Greenland ice sheet by 2100 is projected to be likely in the range 4-12 cm under a low emissions scenario (RCP2.6) and 8-27 cm under a high emissions scenario (RCP8.5). The corresponding values for the Antarctic ice sheet are 1-11 cm under RCP2.6 and 3-28 cm under RCP8.5 [ix].
If a temperature above a given threshold is maintained for an extended period, the melting of the Greenland ice sheet could self-amplify due to different feedback mechanisms. 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. Complete melting would result in a sea level rise of about 7 m, but it would take tens of millennia if near the threshold and a millennium or more for temperatures a few degrees above the threshold [x]. A continued loss of ice is expected even if global warming would be constrained to less than 2 °C global warming above pre-industrial levels [xi].
Several studies have suggested that the loss of the West Antarctic Ice Sheet is already inevitable and irreversible. However, complete disintegration might be delayed or prevented if the underlying bedrock were to rebound faster than previously assumed. There are also indications of instability in some parts of the much larger East Antarctic Ice Sheet. While the uncertainties are large, the global mean sea level contribution from Antarctica alone could be several metres on a time scale of a few centuries to a millennium, in particular under high emissions scenarios [xii].
[i] M. Meredith et al., ‘Chapter 3: Polar Regions’, in IPCC Special Report on the Ocean and Cryosphere in a Changing Climate, ed. H.-O. Pörtner et al. (Cambridge, UK: Cambridge University Press, 2019), https://www.ipcc.ch/srocc/download-report/.
[ii] Meredith et al., ‘Chapter 3: Polar Regions’.
[iii] Jérémie Mouginot et al., ‘Forty-Six Years of Greenland Ice Sheet Mass Balance from 1972 to 2018’,Proceedings of the National Academy of Sciences, 22 April 2019, 201904242, https://doi.org/10.1073/pnas.1904242116; Michael Bevis et al., ‘Accelerating Changes in Ice Mass within Greenland, and the Ice Sheet’s Sensitivity to Atmospheric Forcing’,Proceedings of the National Academy of Sciences 116, no. 6 (5 February 2019): 1934–39, https://doi.org/10.1073/pnas.1806562116.
[iv] Jonathan L Bamber et al., ‘The Land Ice Contribution to Sea Level during the Satellite Era’,Environmental Research Letters 13, no. 6 (1 June 2018): 063008, https://doi.org/10.1088/1748-9326/aac2f0; Meredith et al., ‘Chapter 3: Polar Regions’; Michael Oppenheimer et al., ‘Chapter 4: Sea Level Rise and Implications for Low Lying Islands, Coasts and Communities’, inIPCC Special Report on the Ocean and Cryosphere in a Changing Climate, ed. H.-O. Pörtner et al. (Cambridge, UK: Cambridge University Press, 2019), https://www.ipcc.ch/srocc/download-report/; The IMBIE Team, ‘Mass Balance of the Greenland Ice Sheet from 1992 to 2018’,Nature, 10 December 2019, https://doi.org/10.1038/s41586-019-1855-2.
[v] NSIDC, ‘Europe’s Warm Air Spikes Greenland Melting to Record Levels’, National Snow & Ice Data Center,Greenland Ice Sheet Today (blog), 6 August 2019, https://nsidc.org/greenland-today/2019/08/europes-warm-air-spikes-greenland-melting-to-record-levels/.
[vi] S. V. Nghiem et al., ‘The Extreme Melt across the Greenland Ice Sheet in 2012’,Geophysical Research Letters 39, no. 20 (2012): L20502, https://doi.org/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, https://doi.org/10.5194/tc-7-615-2013.
[vii] 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, https://doi.org/10.1126/science.aaa0940; The IMBIE team, ‘Mass Balance of the Antarctic Ice Sheet from 1992 to 2017’,Nature 558, no. 7709 (June 2018): 219–22, https://doi.org/10.1038/s41586-018-0179-y; Oppenheimer et al., ‘Chapter 4: Sea Level Rise and Implications for Low Lying Islands, Coasts and Communities’.
[viii] B. Wouters et al., ‘Dynamic Thinning of Glaciers on the Southern Antarctic Peninsula’,Science 348, no. 6237 (22 May 2015): 899–903, https://doi.org/10.1126/science.aaa5727; M. MacFerrin et al., ‘Rapid Expansion of Greenland’s Low-Permeability Ice Slabs’,Nature 573, no. 7774 (September 2019): 403–7, https://doi.org/10.1038/s41586-019-1550-3.
[ix] IPCC,Special Report on the Ocean and Cryosphere in a Changing Climate, ed. H.-O. Pörtner et al. (Cambridge, UK: Cambridge University Press, 2019), https://www.ipcc.ch/srocc/download-report/.
[x] 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, https://doi.org/10.1038/nclimate1449; 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; Patrick J. Applegate et al., ‘Increasing Temperature Forcing Reduces the Greenland Ice Sheet’s Response Time Scale’,Climate Dynamics 45 (2015): 2001–11, https://doi.org/10.1007/s00382-014-2451-7; 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, https://doi.org/10.1002/2014GL061142; Oppenheimer et al., ‘Chapter 4: Sea Level Rise and Implications for Low Lying Islands, Coasts and Communities’.
[xi] Frank Pattyn et al., ‘The Greenland and Antarctic Ice Sheets under 1.5 °C Global Warming’,Nature Climate Change 8, no. 12 (December 2018): 1053–61, https://doi.org/10.1038/s41558-018-0305-8.
[xii] 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 (Mai 2014): 3502–9, https://doi.org/10.1002/2014GL060140; 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, https://doi.org/10.1016/j.epsl.2015.10.008; Peter U. Clark et al., ‘Consequences of Twenty-First-Century Policy for Multi-Millennial Climate and Sea-Level Change’,Nature Climate Change 6, no. 4 (April 2016): 360–69, https://doi.org/10.1038/nclimate2923; 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, https://doi.org/10.1038/nature17145; Valentina R. Barletta et al., ‘Observed Rapid Bedrock Uplift in Amundsen Sea Embayment Promotes Ice-Sheet Stability’,Science 360, no. 6395 (22 June 2018): 1335–39, https://doi.org/10.1126/science.aao1447; J. Kingslake et al., ‘Extensive Retreat and Re-Advance of the West Antarctic Ice Sheet during the Holocene’,Nature 558, no. 7710 (June 2018): 430–34, https://doi.org/10.1038/s41586-018-0208-x.
In April 2013, the European Commission 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 to allow 'Better informed decision-making'. This will be achieved by bridging knowledge gaps and further developing the European climate adaptation platform (Climate-ADAPT) as the ‘first-stop shop’ for adaptation information in Europe. Climate-ADAPT has been developed jointly by the European Commission and the European Environment Agency (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. It was relaunched in early 2019 with a new design and updated content. Further objectives include 'Promoting adaptation in key vulnerable sectors through climate-proofing EU sector policies' and 'Promoting action by Member States'.
In November 2018, the Commission published its evaluation of the 2013 EU adaptation strategy. The evaluation package includes a report from the Commission, a Commission staff working document, adaptation preparedness scoreboard country fiches and reports from the JRC Peseta III project. This evaluation includes recommendations for the further development and implementation of adaptation policies at all levels.
In November 2013, the European Parliament and the Council of the European Union adopted the EU's Seventh 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 the 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.
To estimate the mass balance of the polar ice sheets, 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.
Not applicable.
No methodology references available.
Not applicable.
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 are available from Phase 5 of the World Climate Research Programme Coupled Model Intercomparison Project (CMIP5) and continue to be developed in CMIP6. Owing to their economic importance, considerable efforts have also been devoted to improving real-time monitoring of snow cover and sea ice.
Not applicable.
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/greenland-ice-sheet-4/assessment or scan the QR code.
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