The polar regions, notably the Arctic and maritime Antarctic, are experiencing impacts from climate change at magnitudes and rates that are among the highest in the world, and will become profoundly different in the near-term future  under all warming scenarios . In the Arctic, accelerated sea ice loss , increased permafrost thaw and extreme high temperatures have substantially impacted marine, freshwater and terrestrial sociological-ecological systems . Multiple physical, ecological and societal elements of polar regions are approaching a level of change potentially irreversible for hundreds of years, if not millennia . Evidence of borealisation of terrestrial and marine systems is emerging , and cascading impacts are ongoing and widespread yet challenging to quantify fully due to complexity and lags in ecological expression of change. Loss of multi-year sea ice and the occurrence of a seasonally ice-free Arctic Ocean by the middle of this century will result in substantial range contraction, if not the disappearance of several Arctic fish, crab, bird and marine mammal species, including possible extinction of seals and polar bears in certain regions . In the Arctic, permafrost thaw and snowfall decrease lead to profound hydrological changes, an overall greening of the tundra and regional browning of tundra and boreal forests . 
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report