Jun 10, 2011

Declining summer snowfall in the Arctic: causes, impacts and feedbacks

by
James A. Screen, Ian Simmonds
,
Climate Dynamics
  • Explores recent changes in the Arctic hydrological cycle using in situ observations and an improved atmospheric reanalysis data set, ERA-Interim
  • Documents a pronounced decline in summer snowfall over the Arctic Ocean and Canadian Archipelago
  • Diagnoses the snowfall decline as being almost entirely caused by changes in precipitation form (snow turning to rain) with very little influence of decreases in total precipitation
  • States the proportion of precipitation falling as snow has decreased as a result of lower-atmospheric warming
  • Finds that, statistically, over 99% of the summer snowfall decline is linked to Arctic warming over the past two decades
  • Derives an estimate for the amount of snow-covered ice based on the reanalysis snowfall data over the ice-covered Arctic Ocean
  • Estimates that the area of snow-covered ice, and the proportion of sea ice covered by snow, have decreased significantly
  • Performs a series of sensitivity experiments in which inter-annual changes in snow-covered ice are either unaccounted for, or are parameterized
  • In the parameterized case, the loss of snow-on-ice results in a substantial decrease in the surface albedo over the Arctic Ocean, that is of comparable magnitude to the decrease in albedo due to the decline in sea ice cover
  • Finds, accordingly, that the solar input to the Arctic Ocean is increased, causing additional surface ice melt
  • Concludes that the decline in summer snowfall has likely contributed to the thinning of sea ice over recent decades
  • The results presented provide support for the existence of a positive feedback in association with warming-induced reductions in summer snowfall