The cryosphere

                        

Since the mid-1980s, Arctic surface air temperatures have warmed at least twice as fast as the global average. This has potentially large implications not only for Arctic ecosystems, but also for the global climate through various feedbacks such as thawing permafrost releasing methane into the atmosphere.

The 2020 Arctic sea-ice extent minimum after the summer melt was 3.74 million km2, marking only the second time on record that it shrank to less than 4 million km2.  Record low sea-ice extents were observed in the months of July and October. Record high temperatures north of the Arctic Circle in Siberia triggered an acceleration of sea-ice melt in the East Siberian and Laptev Seas, which saw a prolonged marine heatwave. The sea-ice retreat during the summer 2020 in the Laptev Sea was the earliest observed in the satellite era.

The Greenland ice sheet continued to lose mass. Although the surface mass balance was close to the long-term average, the loss of ice due to iceberg calving was at the high end of the 40-year satellite record. In total, approximately 152 Gt of ice were lost from the Greenland ice sheet between September 2019 and August 2020.

The Antarctic sea-ice extent remained close to the long-term average. However, the Antarctic ice sheet has exhibited a strong mass loss trend since the late 1990s. This trend accelerated around 2005, and currently, Antarctica loses approximately 175 to 225 Gt per year, due to the increasing flow rates of major glaciers in West Antarctica and the Antarctic Peninsula.

A loss of 200 Gt of ice per year corresponds to about twice the annual discharge of the river Rhine in Europe.