Autonomous Observations of the Heat and Mass Balance of Arctic Sea Ice

Abstract:

For the past decade the Arctic Observing Network included autonomous measurements of the mass balance of Arctic sea ice. A system of Ice Mass Balance (IMB) buoys measured time series of snow accumulation and ablation; ice growth and surface and bottom melt; and vertical profiles of air, snow, ice, and ocean temperature. The mass balance is the great integrator of heat and can be used to derive estimates of both the surface heat budget and ocean heat flux. Large spatial and interannual variations in surface and bottom melting are evident in the data record. For example, over the western Arctic the observed total summer surface melting ranges from as little as 0.05 m to over 0.75 m. Bottom melting exhibits an even more extreme range varying from 0.1 to 2.2 m. IMBs in the Beaufort Sea and Central Arctic during the summer of 2013 are selected for more detailed analysis, calculating the time series of net surface energy budget and of the ocean heat flux. Ice temperature profiles are used to determine internal melting of the ice. Results from these buoys are integrated with high resolution satellite imagery to examine the heat and mass balance on the aggregate scale. Incident solar radiation is obtained from reanalysis products and used to calculate solar heat input to leads and to the upper ocean. Floe perimeter, ice motion, and lead heat content are combined to estimate the amount of lateral melting. From this integrated analysis, summer ice losses due to surface, bottom, lateral, and internal melting are computed on the aggregate scale and compared regionally.