Impact of Winter Storms in a Thinner Arctic Sea-ice Regime

Speaker: 
Polona Itkin
Affiliation: 
Norwegian Polar Institute
Seminar Date: 
5. June 2018 - 10:00 - 11:00
Location: 
Lecture room, Ground Floor, NERSC

The integrative effects of increased winter storm activity in the Arctic's Atlantic sector were studied using a collection of field observations and analyses. In early 2015, during the six-month N-ICE2015 expedition in the pack ice north of Svalbard, we observed a chain of events in the atmosphere-ice-ocean system that was triggered by several powerful winter storms. Our unique, interdisciplinary observations show that these winter storms entail significant effects that last much longer than the short-lived storm events themselves. The rapid warm and moist air advection associated with the storms contributed to a deep snow-pack and ice surface warming that inhibited thermodynamic sea-ice growth. Instead, the heavy snow-load promoted flooding and formation of snow-ice. The strong winds deformed the sea ice, opening up leads, increased air-to-sea CO2 fluxes by a factor of 20 and increased the concentration of sea-salt aerosols. The storms also enhanced ocean mixing, with ocean-to-ice heat fluxes that were 17 times larger than background values when warm Atlantic Water was near the surface. This resulted in mid-winter bottom-ice melt rates of 5-25 cm/day. In spring, the aggregate effect of winter storms promoted algal growth at the flooded snow-ice interface, produced ice algal hotspots in pressure ridges, and the light transmission through leads set off an extensive under-ice phytoplankton bloom.