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Sea Ice
WHAT IS ALREADY HAPPENING
  • The extent and thickness of Arctic sea ice continues to decrease, especially in summer months (May to September) and the area of thick, multiyear ice is in significant decline. 
     
  • September Arctic sea ice extent, taken as the annual minimum, has reduced by an average of 13% per decade compared to the 1981–2010 mean.
     
  • At least half of Arctic sea ice loss since the mid-20th Century can be directly attributed to anthropogenic warming of surface air temperature. Direct ocean warming, inflows of warm water and a reduced albedo effect, are also important factors. 
     
  • A change from permanent to seasonal ice cover has the potential to affect atmospheric circulation, with possible links to seasonal UK climate (e.g. cold winters).  
     
CONFIDENCE LEVEL
MEDIUM

Medium evidence, high agreement

The international scientific community continues to make significant progress in understanding the Arctic system (e.g. from autonomous robotic platforms, ship-based observations, and satellite sensors, and longer time series) and the rapid changes occurring, but more accurate pan-Arctic snow and sea-ice thickness data throughout the year is needed.

What could happen in the future?
  • Under a high-emission scenario, it is very likely that the Arctic will become seasonally ice-free before 2050. 
     
  • Changes in the timing of sea ice formation and melt is likely to cause a mismatch in demand for food and habitat for marine species, with potential impacts on Arctic fisheries. 
     
CONFIDENCE LEVEL
MEDIUM

Medium evidence, high agreement

Climate model physics and level of agreement among ensembles has improved, yet the ‘absolute’ accuracy of climate model projections is difficult to measure owing to internal variability and emission scenario uncertainty. The downward trend in sea ice extent is expected to continue.

Key Challenges and Emerging Issues
  • Assessing risks associated with Arctic Shipping (e.g., increased radiative forcing from non-CO2 sources; contaminant spills; waves/floes/icing spray damage to ships). 
     
  • Assessing climate change impacts on coastal erosion and permafrost decay (e.g., increased erosion releasing organic carbon to nearshore and rapid permafrost thawing discharging carbon).
     
  • Identifying potential impacts from changes in sea ice and the ocean on Arctic marine ecosystem services (fisheries/industries/beneficial use for indigenous people).