An examination of relationships among the energy balance, surface properties and climate over snow covered sea ice during the spring season.

摘要

In this thesis, the form of the springtime energy balance, its linkage to snow and sea ice thermodynamics, and the environmental forcing on the melt process of sea ice in the Canadian Arctic Archipelago are examined. I address the following questions: (1) How much energy is available to the surface snow cover and when? (2) Where does this energy come from and what are the major energy sinks to the system? (3) How do characteristics of the surface (sea ice and snow) and the atmosphere influence these relations?; Answers to these questions are necessary so that parameterizations of the energy balance may be developed and properly interpreted for the improvement of climate models. The multiple-year nature of this study permits an examination of energy interactions in a fully coupled surface-atmospheric system, and for the first time, under widely varying springtime atmospheric and surface conditions.; The available energy to the surface is strongly linked to processes within the snow volume (heat conduction and ice production), but not to net radiation in the early spring. In contrast, most of the energy available to the system is attributable to the radiation balance in the late spring. Sublimation at the snow surface is the dominant heat loss mechanism while the snow is cold, but the snow volume consumes a larger proportion of the surface's available energy when the snow warms. The presence of salt within the snow is particularly effective at decoupling the snow surface energy balance from oceanic heating.; The nature of the difference in the energy balance between first-year and multi-year sea ice types depends on the characteristics of the ice types being compared. A thick multi-year sea ice floe is shown to be an environment of lower albedo, higher net radiation, larger melt rates and enhanced turbulent heat loss relative to nearby first-year sea ice. Failure to consider the difference in sea ice properties can cause errors in the prediction of complete in-situ sea ice melt by up to 12 days.; Two negative feedback processes between the surface and atmosphere, and involving the turbulent heat fluxes, are extremely effective at moderating the heating of the snow surface by the atmosphere throughout the spring season. Conductive heat flow into the snow from below tends to warm a cooling snow volume under cooling atmospheric conditions. The surface albedo positive feedback is isolated to periods of clear sky and rising air temperature; however, under such circumstances, the outgoing long-wave flux negative feedback is observed, and acts to offset surface heating.; The net effect of clouds is to warm the snow surface throughout the diurnal cycle in the early spring, and during hours outside of the daytime period during the late spring. The environmental conditions associated with cloud cover promote a more rapid ripening of the snow, but clear skies facilitate a rapid removal of the snow after the onset of melt. Precipitation often accompanies overcast conditions and, in the late spring, it can act to delay melt by maintaining a high surface albedo if the precipitation is solid, or accelerate melt by reducing the surface albedo, as is the case for rain.; These findings show that the net response of the sea ice zone, in the presence of a warming atmosphere, will depend heavily on the patterns of environmental change associated with warming. (Abstract shortened by UMI.)