Driver Region Observed changes Projected changes Marine and sea ice Sea level (relative) ArcticNo consistent trend (increase in northwest America, decrease in northeast America, stable in Greenland and Arctic Russia) (WG1-12)Rise in all polar regions (except areas of substantial land uplift in northeast Canada, the west coast of Greenland) (high confidence); Increase of extreme sea levels in Russian Arctic and northwest America (high confidence) Greenland/Iceland and northeast America (given glacial isostatic adjustment) (medium confidence, WG1-12) AntarcticRise in all polar regions (except areas of substantial land uplift in west Antarctica) (high confidence, WG1-12) Sea surface temperature ArcticIncrease of ~0.5°C per decade during 1982–2017 in ice-free regions in summer (high confidence, SROCC-3)Further increases (high confidence, WG1-12) AntarcticWarmed in northern areas of Southern Ocean but cooled in its southernmost regions since the 1980s (high confidence, SROCC-3)Circumpolar increases (high confidence, WG1-12) Sea ice cover ArcticLoss (particularly of multi-year sea ice) accelerated since 2001 (very likely, WG1-9)Will become sea ice free (< 1 × 106 km2) during summer before 2050, irrespective of global warming level (likely, WG1-9) AntarcticNo significant circumpolar trend from 1979–2018 (very high confidence), but decrease off the Antarctic Peninsula