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Observations of sea ice albedo and mass balance observations at SHEBA |
CRREL-ERDC, University of Washington, CRREL-ERDC, CRREL-ERDC, University of Washington, University of Alaska, CRREL-ERDC, University of Washington
perovich@crrel.usace.army.milThe overall objective of the SHEBA snow and ice program is to develop a quantitative understanding of the processes that collectively make up the ice albedo feedback mechanism. To achieve this objective, we examined the distribution of shortwave radiation within the ice-ocean system and assessed the effects of this distribution on the mass balance of the ice pack. During the field experiment we made a detailed, year-long set of observations of ice albedo, ice mass balance, and snow properties. Results indicate that changes in albedo are a combination of a gradual evolution due to seasonal transitions and abrupt shifts caused by synoptic weather events. There were five distinct phases in the seasonal evolution of albedo: dry snow, melting snow, pond formation, pond evolution, and fall freezeup. Data from more than 100 ice thickness gauges installed in a wide variety of ice types indicated a net thinning of the ice at every multiyear site. There was a steady increase in thickness through the winter that gradually tapered off in the spring. Maximum surface melting was in June and July, while bottom ablation peaked in August. Combining results from the sites we found an average winter growth of 0.5 m and a summer melt of 1.05 m that consisted of 0.55 m of surface melt and 0.5 m of bottom melt. Snow surveys showed a gradual increase in snow depth during the winter followed by a rapid 2-3 week snow melt period in early June. The maximum snow depth was in May when the mean was 34 cm.
