Ocean-to-Ice Heat Flux and Diminished Arctic Sea Ice Cover (Invited)
Abstract
Ocean-to-Ice Heat Flux and the Decline of the Arctic Sea Ice Cover Heat transport from the ocean to the base of the sea ice plays a significant role in the enthalpy balance of the Arctic Ocean sea ice cover. In this presentation, we touch on two aspects of heat storage and transport in the upper Arctic Ocean: (1) the role of ocean-to-ice heat flux supported by vertical transport of heat stored below the mixed layer and (2) the vertical structure of temperature and vertical heat fluxes within the mixed layer. Inflows to the Arctic Ocean from the North Atlantic and North Pacific, carrying significant quantities of heat, circulate below the mixed layer within the Arctic. An overview analysis of ocean-to-ice heat flux estimates based on older observations (AIDJEX and SHEBA) and newer observations from autonomous systems deployed as part of the Arctic Observing Network is conducted to examine the possible contribution of these heat sources to sea ice melt. We emphasize wintertime heat fluxes, to exclude the large affects of incoming solar radiation, finding that wintertime fluxes are typically small (winter-averaged values less than 1 W/m^2), except close to bathymetric features such as the Chukchi Borderlands and the Yermak Plateau. The results indicate that vertical fluxes supported by heat below the mixed layer have a small affect on the enthalpy budget of the sea ice cover, at least in the areas where the drifting-ice-based measurements have been made. Observations from Autonomous Ocean Flux Buoys, including eddy-correlation flux measurements and a high-resolution thermistor chain, are providing detailed views of heat storage and transport within the mixed layer. The vertical structure of temperature and heat flux varies with nearby open water fraction. The vertical structure of low ice concentration conditions is more similar to that of strong entrainment than to high ice concentration conditions. Our interpretation of this observation is that large areas of leads, melt ponds, and thin ice lead to strongly heterogeneous input of solar radiation to the ocean. As ice floes move over areas that were recently heated, mixed layer vertical structure similar to entrainment conditions is produced. The observation highlights the need to better understand lateral transport and mixing processes below sea ice.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.C53B..06S
- Keywords:
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- 0764 CRYOSPHERE / Energy balance;
- 4568 OCEANOGRAPHY: PHYSICAL / Turbulence;
- diffusion;
- and mixing processes;
- 4572 OCEANOGRAPHY: PHYSICAL / Upper ocean and mixed layer processes