Impacts of climate change on Arctic sea ice.

Satellite measurements continue to reveal reductions in the extent and thickness of Arctic sea ice. Research suggests that at least half of the observed decline of ice extent can be linked directly to anthropogenic greenhouse gas emissions and the resulting increase in global mean surface air temperature. As perennial sea ice has been progressively replaced by seasonal ice cover, we have observed changes to the marine ecosystem, ocean properties, atmospheric circulation, and evidence of Arctic links to extreme weather events at lower latitudes. Under the RCP8.5 future emission scenario, it is very likely that we will see a seasonally ice-free Arctic before 2050. Crucially, if we comply with the terms of the Paris Agreement and limit global average temperatures to below 2.0°C above pre-industrial levels, the likelihood of a seasonally ice-free Arctic will be greatly reduced. Furthermore, if we limit warming to only 1.5°C above pre-industrial levels, then there is a high chance that the Arctic will not become ice free in summer. A warmer Arctic will increase coastal erosion, permafrost thawing and marine pollutants. The future of Arctic marine ecosystem and the sustainability of the fishing industry will be more uncertain due to changing ocean circulation, nutrient flow and light availability.