Arctic and Baltic sea ice

Indicator Assessment
Prod-ID: IND-98-en
Also known as: CLIM 010 , CSI 053
Created 29 Oct 2018 Published 15 Nov 2018 Last modified 15 Nov 2018
6 min read
The extent and volume of Arctic sea ice has declined rapidly since global data became available, especially in summer. Over the period 1979–2018, the Arctic has lost, on average, 89 000 km 2 per year by the end of summer (measured in September) and 46 000 km 2 of sea ice per year in winter (measured in March). In each of the last 12 years (2007–2018), Arctic summer sea ice extent was lower than in any previous year since the introduction of satellites in 1979. Arctic winter sea ice in 2017 and 2018 were the lowest on record. Arctic sea ice is also getting younger and thinner. The fraction of multi-year ice (i.e. ice that has sustained at least one summer) has decreased from 45 % in March 1985 to 21 % in March 2017. The maximum sea ice extent in the Baltic Sea shows a decreasing trend since about 1800. The decrease appears to have accelerated since the 1980s, but the interannual variability is large. Arctic sea ice is projected to continue shrinking and thinning. At current emission rates, a nearly ice-free Arctic Ocean at the end of summer is likely before mid-century. In contrast, emissions scenarios compatible with 1.5 °C global warming are expected to preserve Arctic summer sea ice. Baltic Sea ice, in particular the extent of the maximal cover, is projected to continue to shrink. Changes in the extent of sea ice are an important indicator of global warming. Reduced Arctic sea ice is accelerating global warming through the ice-albedo feedback. Arctic sea ice decline has also been linked to changing climate and weather extremes in Europe and beyond.

Key messages

  • The extent and volume of Arctic sea ice has declined rapidly since global data became available, especially in summer. Over the period 1979–2018, the Arctic has lost, on average, 89 000 km2 per year by the end of summer (measured in September) and 46 000 km2 of sea ice per year in winter (measured in March).
  • In each of the last 12 years (2007–2018), Arctic summer sea ice extent was lower than in any previous year since the introduction of satellites in 1979. Arctic winter sea ice in 2017 and 2018 were the lowest on record.
  • Arctic sea ice is also getting younger and thinner. The fraction of multi-year ice (i.e. ice that has sustained at least one summer) has decreased from 45 % in March 1985 to 21 % in March 2017.
  • The maximum sea ice extent in the Baltic Sea shows a decreasing trend since about 1800. The decrease appears to have accelerated since the 1980s, but the interannual variability is large.
  • Arctic sea ice is projected to continue shrinking and thinning. At current emission rates, a nearly ice-free Arctic Ocean at the end of summer is likely before mid-century. In contrast, emissions scenarios compatible with 1.5 °C global warming are expected to preserve Arctic summer sea ice.
  • Baltic Sea ice, in particular the extent of the maximal cover, is projected to continue to shrink.
  • Changes in the extent of sea ice are an important indicator of global warming. Reduced Arctic sea ice is accelerating global warming through the ice-albedo feedback. Arctic sea ice decline has also been linked to changing climate and weather extremes in Europe and beyond.

What is the trend in the extent of Arctic and Baltic sea ice?

Arctic sea ice extent

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Maximum extent of ice cover in the Baltic Sea

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Projected changes in Northern Hemisphere September sea ice extent

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Past trends

In the period 1979–2018, the sea ice extent in the Arctic decreased by 46 000 km2 per year in winter (measured in March) and by 89 000 km2 per year in summer (measured in September) (Figure 1). The decrease in summer sea ice corresponds to more than 10 % per decade. Based on historical records, this decline is likely unprecedented since at least the 14th century [i]. Summer sea ice cover in each of the last 12 years (2007–2018) was lower than in any previous year since satellite measurements began in 1979. The minimum Arctic sea ice cover in September 2012 broke all previously observed records; it was about half the level of the 1981–2010 period. Winter sea ice extent in March 2017 and March 2018 were the lowest on record.

Arctic sea ice is also getting thinner and younger, as less sea ice survives the summer to grow into thicker multi-year floes. Annual mean ice thickness has decreased by 65 % between 1975 and 2012 [ii]. The percentage of multi-year ice (more than 1 year old) in March has decreased from 45 % in 1985 to 21 % in 2017. Very old ice (more than 4 years old) has virtually disappeared; it decreased from 16 % to 0.9 % over the same period [iii].

Arctic sea ice loss is driven by a combination of warmer ocean waters and a warmer atmosphere, including an earlier onset of summer surface melt [iv]. Changes in Arctic sea ice may trigger complex feedback processes in the climate system. The reduction of sea ice has significantly reduced albedo, corresponding to an additional 6.4 ± 0.9 W/m2 of solar energy input into the Arctic Ocean region between 1979 and 2011. Averaged over the globe, this albedo decrease corresponds to a forcing that is 25 % of that due to the change in CO2 during this period [v]. The increased solar heat uptake by the ocean also delays the autumn refreeze [vi].

Information on sea ice extent in the Baltic Sea goes back to 1720. The maximum sea ice extent has displayed a decreasing trend most of the time since about 1800 (Figure 2). The decrease in sea ice extent appears to have accelerated since the 1980s, but large interannual variability makes it difficult to demonstrate this statistically [vii]. The frequency of mild ice winters, defined as having a maximum ice cover of less than 130 000 km2, has, however, increased from seven in 30 years in the period 1950–1979 to 16 in the period 1989–2018. In contrast, the frequency of severe ice winters, defined as having a maximum ice cover of at least 270 000 km2, has decreased from six to one over the same periods.

Antarctic sea ice extent has slowly increased from 1979 to 2014. This trend, however, has reversed recently, and Antarctic ice extent in the last 3 years (2016–2018) was far below the average [viii].

Projections

Improving the ability to track the observed rapid summer-time melting of Arctic sea ice has been a challenge for modelling. Observations fall within the model range in recent modelling studies, but most models underestimate recent sea ice decline [ix].

All model projections agree that Arctic sea ice will continue to shrink and thin.  At current emission rates, a nearly ice-free Arctic Ocean at the end of summer is likely before mid-century (Figure 3) [x]. The probability of the Arctic Ocean being free of sea ice during summer is substantially higher under a scenario of 2° C warming (relative to pre-industrial levels) compared to a 1.5° C scenario [xi].

Extended simulations suggest that the Arctic could become ice-free year-round before the end of the 22nd century for the highest emissions scenario (RCP8.5). On the other hand, a recovery of Arctic sea ice could become apparent in the 22nd century if stringent policies to reduce global greenhouse gas emissions, and eventually their atmospheric concentrations, are successfully implemented [xii].

Projections of Baltic Sea ice extent under different emissions scenarios suggest that the maximal ice cover and ice thickness will continue to shrink significantly over the 21st century. The best estimate of the decrease in maximum ice extent from a model ensemble is 640 km2/year for a medium emissions scenario (RCP4.5) and 1 090 km2/year for a high emissions scenario (RCP8.5); for the latter scenario, largely ice-free conditions are projected by the end of the century [xiii].

Further information

An animation from NOAA shows the decline in multi-year Arctic sea ice extent from 1987 to 2016: https://youtu.be/c6jX9URzZWg



[i] J. Halfar et al., ‘Arctic Sea-Ice Decline Archived by Multicentury Annual-Resolution Record from Crustose Coralline Algal Proxy’,Proceedings of the National Academy of Sciences 110, no. 49 (2013): 19737–41, https://doi.org/10.1073/pnas.1313775110; John E. Walsh et al., ‘A Database for Depicting Arctic Sea Ice Variations Back to 1850’,Geographical Review 107, no. 1 (2017): 89–107, https://doi.org/10.1111/j.1931-0846.2016.12195.x.

[ii] R. Lindsay and A. Schweiger, ‘Arctic Sea Ice Thickness Loss Determined Using Subsurface, Aircraft, and Satellite Observations’,The Cryosphere 9, no. 1 (2015): 269–83, https://doi.org/10.5194/tc-9-269-2015.

[iii] D Perovich et al., ‘Sea Ice’, Arctic Report Card (National Ocean and Atmosphere Program (NOAA), 2018), https://arctic.noaa.gov/Report-Card/Report-Card-2017/ArtMID/7798/ArticleID/699/Sea-Ice.

[iv] Neil C. Swart et al., ‘Influence of Internal Variability on Arctic Sea-Ice Trends’,Nature Climate Change 5, no. 2 (2015): 86–89, https://doi.org/10.1038/nclimate2483; AMAP, ‘Snow, Water, Ice and Permafrost. Summary for Policy-Makers’ (Oslo: Arctic Monitoring and Assessment Programme (AMAP), 2017), https://www.amap.no/documents/doc/Snow-Water-Ice-and-Permafrost.-Summary-for-Policy-makers/1532.

[v] Kristina Pistone, Ian Eisenman, and V. Ramanathan, ‘Observational Determination of Albedo Decrease Caused by Vanishing Arctic Sea Ice’,Proceedings of the National Academy of Sciences 111, no. 9 (4 March 2014): 3322–26, https://doi.org/10.1073/pnas.1318201111.

[vi] Sharon Stammerjohn et al., ‘Regions of Rapid Sea Ice Change: An Inter-Hemispheric Seasonal Comparison’,Geophysical Research Letters 39 (16 March 2012): L06501, https://doi.org/10.1029/2012GL050874.

[vii] Jari J. Haapala et al., ‘Recent Change — Sea Ice’, inSecond Assessment of Climate Change for the Baltic Sea Basin, ed. The BACC II Author Team (Cham: Springer International Publishing, 2015), 145–53, http://link.springer.com/10.1007/978-3-319-16006-1_8.

[viii] Claire L. Parkinson, ‘Global Sea Ice Coverage from Satellite Data: Annual Cycle and 35-Yr Trends’,Journal of Climate 27, no. 24 (December 2014): 9377–82, https://doi.org/10.1175/JCLI-D-14-00605.1; Josefino C. Comiso et al., ‘Positive Trend in the Antarctic Sea Ice Cover and Associated Changes in Surface Temperature’,Journal of Climate 30 (March 2017): 2251–67, https://doi.org/10.1175/jcli-d-16-0408.1; John Turner et al., ‘Unprecedented Springtime Retreat of Antarctic Sea Ice in 2016: The 2016 Antarctic Sea Ice Retreat’,Geophysical Research Letters 44, no. 13 (16 July 2017): 6868–75, https://doi.org/10.1002/2017GL073656; NSIDC, ‘Arctic Summer 2018: September Extent Ties for Sixth Lowest | Arctic Sea Ice News and Analysis’, 2018, https://nsidc.org/arcticseaicenews/2018/10/september-extent-ties-for-sixth-lowest/.

[ix] Dirk Notz and Julienne Stroeve, ‘Observed Arctic Sea-Ice Loss Directly Follows Anthropogenic CO2 Emission’,Science 354, no. 6313 (11 November 2016): 747–50, https://doi.org/10.1126/science.aag2345; Erica Rosenblum and Ian Eisenman, ‘Sea Ice Trends in Climate Models Only Accurate in Runs with Biased Global Warming’,Journal of Climate 30, no. 16 (August 2017): 6265–78, https://doi.org/10.1175/JCLI-D-16-0455.1.

[x] M. Collins et al., ‘Long-Term Climate Change: Projections, Commitments and Irreversibility’, 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), 1029–1136, http://www.climatechange2013.org/images/report/WG1AR5_Chapter12_FINAL.pdf; Alexandra Jahn et al., ‘How Predictable Is the Timing of a Summer Ice-Free Arctic?’,Geophysical Research Letters 43, no. 17 (16 September 2016): 9113–20, https://doi.org/10.1002/2016GL070067; Michael Sigmond, John C. Fyfe, and Neil C. Swart, ‘Ice-Free Arctic Projections under the Paris Agreement’,Nature Climate Change 8, no. 5 (May 2018): 404–8, https://doi.org/10.1038/s41558-018-0124-y.

[xi] IPCC, ‘Global Warming of 1.5 °C’ (Geneva: Intergovernmental Panel Climate Change, 2018), chap. 3, http://www.ipcc.ch/report/sr15/; Alexandra Jahn, ‘Reduced Probability of Ice-Free Summers for 1.5 °C Compared to 2 °C Warming’,Nature Climate Change 8, no. 5 (May 2018): 409–13, https://doi.org/10.1038/s41558-018-0127-8; Sigmond, Fyfe, and Swart, ‘Ice-Free Arctic Projections under the Paris Agreement’.

[xii] P. J. Hezel, T. Fichefet, and F. Massonnet, ‘Modeled Arctic Sea Ice Evolution through 2300 in CMIP5 Extended RCPs’,The Cryosphere 8, no. 4 (2014): 1195–1204, https://doi.org/10.5194/tc-8-1195-2014.

[xiii] Anna Luomaranta et al., ‘Multimodel Estimates of the Changes in the Baltic Sea Ice Cover during the Present Century’,Tellus A 66, no. 22617 (4 April 2014), https://doi.org/10.3402/tellusa.v66.22617.

Indicator specification and metadata

Indicator definition

  • Trend in Arctic sea ice extent in March and September
  • Maximum extent of ice cover in the Baltic Sea
  • Projected changes in Northern Hemisphere September sea ice extent

Units

  • Area (km²)

Policy context and targets

Context description

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 vulnerable sectors 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 November 2018, the EC published an evaluation of the EU Adaptation Strategy. The evaluation package comprises a Report on the implementation of the EU Strategy on adaptation to climate change (COM(2018)738), the Evaluation of the EU Strategy on adaptation to climate change (SWD(2018)461), and the Adaptation preparedness scoreboard Country fiches (SWD(2018)460).

The evaluation found that the EU Adaptation Strategy has been a reference point to prepare Europe for the climate impacts to come, at all levels. It emphasised that EU policy must seek to create synergies between climate change adaptation, disaster risk reduction efforts and sustainable development to avoid future damage and provide for long-term economic and social welfare in Europe and in partner countries. The evaluation also suggests areas where more work needs to be done to prepare vulnerable regions and sectors.

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.

Targets

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: Country information
    Overview of activities of EEA member countries in preparing, developing and implementing adaptation strategies
  • 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
  • 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.
  • Evaluation of the EU Adaptation Strategy Package
    In November 2018, the EC published an evaluation of the EU Adaptation Strategy. The evaluation package comprises a Report on the implementation of the EU Strategy on adaptation to climate change (COM(2018)738), the Evaluation of the EU Strategy on adaptation to climate change (SWD(2018)461), and the Adaptation preparedness scoreboard Country fiches (SWD(2018)460). The evaluation found that the EU Adaptation Strategy has been a reference point to prepare Europe for the climate impacts to come, at all levels. It emphasized that EU policy must seek to create synergies between climate change adaptation, disaster risk reduction efforts and sustainable development to avoid future damage and provide for long-term economic and social welfare in Europe and in partner countries. The evaluation also suggests areas where more work needs to be done to prepare vulnerable regions and sectors.

Methodology

Methodology for indicator calculation

Input data were available from the EUMETSAT OSI SAF reanalysis project, in which a consistent time series of daily, gridded data for sea ice concentration is made from the passive microwave sensors SMMR and SSM/I data. Monthly aggregated sea ice products are provided by the Copernicus Marine Environment and Monitoring Service (CMEMS).

The annual maximum ice extent in the Baltic Sea was estimated utilising material from the Finnish operational ice service for the winters of 1945-1995 and information collected by Prof. Jurva from the winters of 1720-1940. The latter originated from various sources, including observations at lighthouses, old newspapers, records on travel on ice, scientific articles and air temperature data from Stockholm and Helsinki.

Projections for Northern Hemisphere sea ice extent were derived from the CMIP5 ensemble experiment.

The graphs show the data as delivered; linear trend lines and moving averages were added.

Methodology for gap filling

Not applicable

Methodology references

Uncertainties

Methodology uncertainty

Not applicable

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.

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.

Rationale uncertainty

No uncertainty has been specified

Data sources

Generic metadata

Topics:

information.png Tags:
, , , , , , ,
DPSIR: Impact
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
Indicator codes
  • CLIM 010
  • CSI 053
Temporal coverage:
information.png Geographic coverage:

Geographical areas

, ,

Contacts and ownership

EEA Contact Info

Hans-Martin Füssel

Dates

Frequency of updates

Updates are scheduled every 2 years
Document Actions
European Environment Agency (EEA)
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Denmark
Phone: +45 3336 7100