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Indicator Assessment
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 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 Balttic Sea 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., 2014, ‘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.
This indicator measures:
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.
No targets have been specified.
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.
Not applicable.
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.
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.
No uncertainty has been specified
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/arctic-sea-ice-3/assessment-1 or scan the QR code.
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