In September 2020 the Arctic sea ice extent shrunk to the second lowest in the 42-year satellite record, behind September 2012. Meanwhile, October 2020 became the lowest on record.
03 October 2023
25 September 2020
By Christine Traeger-Chatterjee, Hayley Evers-King and Federico Fierli (EUMETSAT), Thomas Lavergne and Steinar Eastwood (OSI SAF) and Ben Loveday (Innoflair)
Paolo Ruti, EUMETSAT Chief Scientist, said: "The Arctic is the sensible thermometer of our planet. In the last decade, the Arctic thermometer readings generally indicate a serious fever. The year 2020 will stand as an additional warning on the effects of climate change in polar regions. EUMETSAT is at the forefront of science and technology in monitoring our planet from space, guaranteeing high-quality data for climate analysis and research.”
The fast-warming of the Arctic has started to transition from a predominantly frozen state into a different climate-influencing weather phenomena outside the Arctic itself.
Paolo Ruti concluded: "What happens in the Arctic does not stay there. The weather in Paris or in Berlin, for example, depends on the Arctic state as well. This is why EUMETSAT data are so important to feed the weather prediction models and to guarantee high-standard information to European decision makers."
This case study shows a snapshot of sea ice conditions seen by OLCI on Sentinel-3 and, most importantly, the 2020 evolution from the OSI SAF long-term data record (1979–present day) on sea ice, relating the current situation to the past 42 years.
The ongoing reduction in sea-ice thickness and sea ice-extent affects terrestrial climate as a whole — from global ocean circulation through sea level, to impacts on atmospheric circulation and, thus, weather patterns. Monitoring these changes in sea ice, and understanding related processes, is crucial for observing, understanding, and predicting climate change and its impacts.
Data from satellites are key sources of information thanks to their global view and multi-decadal time coverage of sea ice conditions. Sea ice is observed using multiple techniques and spectral information, such as microwave and optical, from current earth observation satellites.
Visible optical measurements at high resolution, like those from Sentinel-3 OLCI, allow us to look at sea ice and some of its characteristics. However, there are challenges to using this data, including distinguishing sea ice from clouds. The suite of satellite microwave sensors provide the temporal perspective for long-term estimations of sea ice parameters.
The recent optical instrument on the Sentinel-3 satellites, provides a medium resolution imagery 'snapshot' of ice conditions from the last three years. Figure 1 is an Sentinel-3B OLCI True Colour RGB (optical) image from 25 September 2020 at 13:35 UTC, showing land ice and sea ice instantaneous conditions at the east coast of Greenland. Patches in the sea ice melt can be seen near the shore, while further offshore the influence of ocean currents can be clearly seen, as floating ice reveals swirling eddies.
Using the Special Sensor Microwave Imager and Sounder (SSMIS) on the DMSP satellites, plus the Advanced Microwave Scanning Radiometer (AMSR) on Aqua, and ASCAT on Metop, EUMETSAT's Satellite Application Facility on Ocean and Sea Ice (OSI SAF) provides continuous monitoring on key climatic ice variables, e.g. sea ice edge, sea ice drift and sea ice concentration. For sea ice concentration the OSI SAF provides a unique record of passive microwave satellite data covering the time period from 1979 onwards.
Figure 2 illustrates the change in Arctic sea ice extent in million km² between 1979 and 2020. The 2020 sea ice maximum in March is among the lowest in the time series and shows the lowest mid-summer sea extension on record. The annual minimum at the end of the summer season, in mid September, is the second lowest on record (after 2012, replacing 2007 as the previous second lowest on record). The black and red lines for 2020 represent the interim climate data record, and near-real-time products respectively. These recent years are substantially lower than the median observed between 1981 and 2010 (shown in grey on Figure 2). The OSI SAF provides daily updates on the sea ice situation.
Data shows that October 2020 has now the lowest extent showing a much slower glaciation with respect to the whole record.
Since 1979 (when OSI SAF records started), summer Arctic sea ice extent has lost approximately 2 Mio km². To compare, this is about: (1) the size of Greenland itself, (2) one fifth of the Northern Hemisphere average sea ice area, (3) one tenth of the whole polar circle area.
The animation in Figure 3 shows how the Polar Sea Ice evolved during the 2020 season. The video collected the daily sea ice concentration since 1 January 2020, derived from SSMIS brightness temperatures. Data are expressed in % of ice coverage per grid box (10 x 10km).
OSI SAF Daily updated Sea Ice Extent Trackers
Arctic Sea Ice News & Analysis (National Snow & Ice Data Center)
2020 Arctic Sea Ice Minimum at Second Lowest on Record (NASA)
Sea ice cover for August 2020 (Copernicus Climate Change Service)