Arctic and Baltic sea ice

Indicator Assessment
Prod-ID: IND-98-en
Also known as: CLIM 010 , CSI 053
Created 05 Nov 2019 Published 04 Dec 2019 Last modified 04 Dec 2019
6 min read
The extent and volume of Arctic sea ice is declining rapidly. Over the period 1979–2019, the Arctic has lost, on average, 82 000 km 2 per year by the end of summer and 42 000 km 2 of sea ice per year in winter. Arctic summer sea ice in each of the last 13 years (2007–2019) was lower than in any previous year (1979–2006). Arctic winter sea ice in 2018 and 2017 were the lowest on record. The Arctic sea ice is also getting younger and thinner. 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. 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. 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. Baltic Sea ice, in particular the extent of the maximal cover, is projected to continue to shrink.

Key messages

  • The extent and volume of Arctic sea ice is declining rapidly. Over the period 1979–2019, the Arctic has lost, on average, 82 000 km2 per year by the end of summer and 42 000 km2 of sea ice per year in winter.
  • Arctic summer sea ice in each of the last 13 years (2007–2019) was lower than in any previous year (1979–2006). Arctic winter sea ice in 2018 and 2017 were the lowest on record. The Arctic sea ice is also getting younger and thinner.
  • 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.
  • 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.
  • 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.
  • Baltic Sea ice, in particular the extent of the maximal cover, is projected to continue to shrink.

What are the trends in sea ice extent in the Arctic and in the Baltic Sea?

Arctic sea ice extent

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Maximum extent of ice cover in the Baltic Sea

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Projected changes in sea ice extent in the northern hemisphere in September

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Past trends

In the period 1979-2019, the sea ice extent in the Arctic decreased by 42 000 km2 per year in winter (measured in March) and by 82 000 km2 per year in summer (measured in September) (Fig. 1). The decrease in sea ice during the summer corresponds to a more than 10 % decrease per decade. This decline is unprecedented in the past 1 000 years based on historical reconstructions and paleoclimate evidence [i]. The extent of summer sea ice cover in each of the last 13 years (2007-2019) 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 that recorded in the period 1981-2010. The winter sea ice extents recorded in March 2018 and March 2017 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. The annual mean ice thickness across the central Arctic decreased by 65 % between 1975 and 2012 [ii]. The percentage of ice that is at least 5 years old declined from 30 % to 2 % between 1979 and 2018 [iii].

The loss of Arctic sea ice is driven by a combination of warmer ocean waters and a warmer atmosphere, including the 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, which corresponds to a radiative force 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 autumn refreeze [vi].

Information on sea ice extent in the Baltic Sea goes back to 1720. There has been a decreasing trend in maximum sea ice extent most of the time since about 1800 (Fig. 2). The decrease in sea ice extent appears to have accelerated since the 1980s, but large interannual variability makes it difficult to makes it difficult to demonstrate that this is statistically significant [vii]. The number of 'mild ice winters', defined as having a maximum ice cover of less than 130 000 km2, however, increased from 7 in the period 1950-1979 to 16 in the 30-year period 1990-2019. In contrast, the number of 'severe ice winters', defined as having a maximum ice cover of at least 270 000 km2, decreased from six to one during the same periods.

Antarctic sea ice extent showed an increasing trend from 1979 to 2014, but this trend has reversed recently. The years 2016 to 2018 were all far below the average [viii].

Projections

Improving the ability to track the observed rapid summertime melting of Arctic sea ice through modelling has been challenging. Observations fall within the model range in recent modelling studies, but most models underestimate the 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 the middle of the century (Fig. 3) [x]. For a scenario with warming of 1.5 °C by the end of the century (relative to pre-industrial levels), the chance of an ice-free sea is approximately 1 %, whereas this rises substantially to 10-35 % under a scenario of 2 °C warming [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 maximum ice cover and ice thickness will continue to shrink significantly throughout 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 in the Arctic are projected by the end of the century [xiii].

Further information

An animation from the National Oceanic and Atmospheric Administration (NOAA) shows the decline in Arctic sea ice from 1984 to 2019: https://youtu.be/oTaRhCrzkEk


[i] Halfar, J. et al., 2013, ‘Arctic sea-ice decline archived by multicentury annual-resolution record from crustose coralline algal proxy’, Proceedings of the National Academy of Sciences of the United States of America 110(49), pp. 19737-19741, https://doi.org/10.1073/pnas.1313775110; Walsh, J. E. et al., 2017, ‘A database for depicting Arctic sea ice variations back to 1850’, Geographical Review 107(1), pp. 89-107, https://doi.org/10.1111/j.1931-0846.2016.12195.x.

[ii] Lindsay, R. and Schweiger, A., 2015, ‘Arctic sea ice thickness loss determined using subsurface, aircraft, and satellite observations’, The Cryosphere 9(1), pp. 269-283, https://doi.org/10.5194/tc-9-269-2015.

[iii] Meredith, M. et al., 2019, ‘Chapter 3: polar regions’, in: IPCC Special Report on the ocean and cryosphere in a changing climate, H.-O. Pörtner, H. -O. et al. (eds), Cambridge University Press, Cambridge, UK, https://www.ipcc.ch/srocc/download-report/.

[iv] Swart, N. C. et al., 2015, ‘Influence of internal variability on Arctic sea-ice trends’, Nature Climate Change 5(2), pp. 86-89, https://doi.org/10.1038/nclimate2483; AMAP, 2017, Snow, water, ice and permafrost in the Arctic (SWIPA) 2017, Arctic Monitoring and Assessment Programme, Oslo, Norway, https://www.amap.no/documents/doc/snow-water-ice-and-permafrost-in-the-arctic-swipa-2017/1610.

[v] Pistone, K., Eisenman, I. and Ramanathan, V., 2014, ‘Observational determination of albedo decrease caused by vanishing Arctic sea ice’, Proceedings of the National Academy of Sciences of the United States of America 111(9), pp. 3322–3326, https://doi.org/10.1073/pnas.1318201111.

[vi] Stammerjohn, S. et al., 2012, ‘Regions of rapid sea ice change: an inter-hemispheric seasonal comparison’, Geophysical Research Letters 39, L06501, https://doi.org/10.1029/2012GL050874.

[vii] Haapala, J. J. et al., 2015, ‘Recent change — sea ice’, in: Second assessment of climate change for the Baltic Sea basin, the BACC II Author Team (ed.), Springer International Publishing, Cham, Switzerland, pp. 145-153, http://link.springer.com/10.1007/978-3-319-16006-1_8.

[viii] Comiso, J. C. et al., 2017, ‘Positive trend in the Antarctic sea ice cover and associated changes in surface temperature’, Journal of Climate 30, pp. 2251-2267, https://doi.org/10.1175/jcli-d-16-0408.1; Ludescher, J., Yuan, N. and Bunde, A., 2019, ‘Detecting the statistical significance of the trends in the Antarctic Sea ice extent: an indication for a turning point’, Climate Dynamics 53(1-2), pp. 237-244, https://doi.org/10.1007/s00382-018-4579-3.

[ix] Notz, D. and Stroeve, J., 2016, ‘Observed Arctic sea-ice loss directly follows anthropogenic CO2 emission’, Science 354(6313), pp. 747-750, https://doi.org/10.1126/science.aag2345; Rosenblum, E. and Eisenman, I., 2017, ‘Sea ice trends in climate models only accurate in runs with biased global warming’, Journal of Climate 30(16). pp. 6265-6278, https://doi.org/10.1175/JCLI-D-16-0455.1.

[x] Jahn, A. et al., 2016, ‘How predictable is the timing of a summer ice-free Arctic?’, Geophysical Research Letters 43(17), pp. 9113-9120, https://doi.org/10.1002/2016GL070067; Sigmond, M., Fyfe, J. C. and Swart, N. C., 2018, ‘Ice-free Arctic projections under the Paris Agreement’, Nature Climate Change 8(5), pp. 404-408, https://doi.org/10.1038/s41558-018-0124-y.

[xi] Jahn, A., 2018, ‘Reduced probability of ice-free summers for 1.5 °C compared to 2 °C warming’, Nature Climate Change 8(5), pp. 409-413, https://doi.org/10.1038/s41558-018-0127-8; Sigmond, M., Fyfe, J. C. and Swart, N. C., 2018, ‘Ice-free Arctic projections under the Paris Agreement’, Nature Climate Change 8(5), pp. 404-408, https://doi.org/10.1038/s41558-018-0124-y; Meredith, M. et al., 2019, ‘Chapter 3: polar regions’, in: IPCC Special Report on the ocean and cryosphere in a changing climate, H.-O. Pörtner, H. -O. et al. (eds), Cambridge University Press, Cambridge, UK, https://www.ipcc.ch/srocc/download-report/.

[xii] Hezel, P. J., Fichefet, T. and Massonnet, F., 2014, ‘Modeled Arctic sea ice evolution through 2300 in CMIP5 extended RCPs’, The Cryosphere 8(4), pp. 1195-1204, https://doi.org/10.5194/tc-8-1195-2014.

[xiii] Luomaranta, A. et al., ‘Multimodel estimates of the changes in the Baltic Sea ice cover during the present century’, Tellus A: Dynamic Meterology and Oceanography 66(22617), https://doi.org/10.3402/tellusa.v66.22617.

Indicator specification and metadata

Indicator definition

This indicator measures:

  • trends in Arctic sea ice extent in March and September;
  • the maximum extent of ice cover in the Baltic Sea;
  • projected changes in sea ice extent in the northern hemisphere in September.

Units

  • Area (km²)

Policy context and targets

Context description

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', which will be achieved by bridging knowledge gaps and further developing the European climate adaptation platform (Climate-ADAPT) as the ‘one-stop shop’ for climate adaptation information in Europe. Climate-ADAPT was 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.

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 European Commission also supports adaptation in cities through the Covenant of Mayors for Climate & Energy initiative.

In November 2018, the European Commission 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), an evaluation of the EU strategy on adaptation to climate change (SWD(2018) 461) and a document entitled Adaptation preparedness scoreboard Country fiches (SWD(2018) 460).

The evaluation found that the EU adaptation strategy has been used 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 in which more work needs to be done to prepare vulnerable regions and sectors.

In November 2013, the European Parliament and the Council of the European Union adopted the EU 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.

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: Adaptation in EU policy sectors
    Overview of EU sector policies in which mainstreaming of adaptation to climate change is ongoing or explored
  • Climate-ADAPT: Country profiles
    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.
  • 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 Eumetstat Satellite Application Facility on Ocean and Sea Ice (OSI SAF) reanalysis project, in which consistent time series of daily, gridded data on sea ice concentrations are made from passive microwave sensor (scanning multichannel microwave radiometer (SMMR) and special sensor microwave/imager (SSM/I)) data. Monthly aggregated sea ice products are provided by the Eumetstat OSI SAF (http://osisaf.met.no). The same data are also available from 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 the period 1945-1995 and information collected by Professor Jurva for the winters of the period 1720-1940. The latter originated from various sources, including observations made at lighthouses, old newspapers, records on travel on ice, scientific articles and air temperature data from Stockholm and Helsinki.

Projections of the extent of northern hemisphere sea ice were derived from the fifth phase of the World Climate Research Programme's Coupled Model Intercomparison Project (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 are available from CMIP5, which has provided climate change projections for the Intergovernmental Panel on Climate Change's (IPCC's) fifth assessment report (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

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

, ,

Dates

Frequency of updates

Updates are scheduled once per year

EEA Contact Info

Hans-Martin Füssel
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