Extreme Moisture Transport into the Arctic and Its Effect on Sea-Ice Concentration

Over recent decades the Arctic has warmed approximately twice as fast as the rest of the Northern Hemisphere. At the same time, Arctic sea-ice concentration has decreased rapidly, especially in September when sea ice in the Arctic reaches its lowest extent of the year. Interannual variability in the minimum sea ice extent is enormous, especially over the past decade that includes several years of record minimum coverage interspersed with other less extreme years. Satellite observations of sea ice concentrations go back to 1979.

This vast interannual variability is mostly driven by extratropical atmospheric dynamical processes both directly and indirectly, and modulated by slower ocean processes. Wind represents an important forcing of sea ice distribution that qualifies as direct forcing. Thermodynamical consequences of extratropical dynamical variability such as changes to the radiative surface fluxes due to increased moisture in the Arctic can in turn lead to important feedback processes that can quickly amplify the change. A recent study indicates that in years when there is a low Arctic sea-ice minimum in September there is an increase in moisture transport into the Arctic in the preceding spring. The increase in moisture leads to increased greenhouse effect that is thought to play an important role in initiating the melt in spring that will become an extensive area of melt in September.

In this presentation we will examine interannual variability of extreme moisture transport (also known as atmospheric rivers) into the Arctic and relate it to sea-ice concentration variability at different lags.