Abstract
AbstractDirect observations during intense warm‐air advection over the East Siberian Sea reveal a period of rapid sea‐ice melt. A semistationary, high‐pressure system north of the Bering Strait forced northward advection of warm, moist air from the continent. Air‐mass transformation over melting sea ice formed a strong, surface‐based temperature inversion in which dense fog formed. This induced a positive net longwave radiation at the surface while reducing net solar radiation only marginally; the inversion also resulted in downward turbulent heat flux. The sum of these processes enhanced the surface energy flux by an average of ~15 W m−2 for a week. Satellite images before and after the episode show sea‐ice concentrations decreasing from > 90% to ~50% over a large area affected by the air‐mass transformation. We argue that this rapid melt was triggered by the increased heat flux from the atmosphere due to the warm‐air advection.
Highlights
The most pronounced and robust observation of Arctic climate-change is the reduction in area and thickness of perennial sea ice [Holland and Bitz, 2003; Serreze and Barry, 2011]
In this paper we report on a warm-air advection episode in early August 2014, observed during the Arctic Clouds in Summer Experiment (ACSE) in the East Siberian Sea, at a time of rapid ice melt
Previous studies highlighted the importance of episodic meridional transport of warm and moist air over the Arctic, for the onset of seasonal melt [Persson, 2012; Woods et al, 2013] and for the near-zero peak in the winter bimodal net-radiation probability distribution [Morrison et al, 2012]
Summary
The most pronounced and robust observation of Arctic climate-change is the reduction in area and thickness of perennial sea ice [Holland and Bitz, 2003; Serreze and Barry, 2011]. Arctic sea-ice cover displays a declining trend over the entire satellite record [Serreze et al, 2007]. While this trend occurred for all seasons, with an average area reduction of ~4% per decade, the most pronounced reduction has been in summer, about 12% per decade [e.g., Intergovernmental Panel on Climate Change (IPCC), 2013]. Prediction of sea ice is a growing area of research [Day et al, 2014; Kapsch et al, 2014; see the “Sea Ice Outlook,” http://www.arcus.org/sipn/sea-ice-outlook], as is the potential for navigation of northern sea routes and exploitation of marine natural resources
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