Papakyriakou, Timothy Nicholas2006-07-282006-07-2819991999http://hdl.handle.net/10012/397In 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 (CAA) are examined. I address the following questions: - How much energy is available to the surface snow cover and when? - Where does this energy come from and what are the major energy sinks to the system? - How do characteristics on 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 major findings of the work are summarized in the following points. 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. Net radiation in the early spring accounts for, on average, only 18% of the total available energy. In contrast, approximately 95% 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. This feature will not be reproduced using a single snow model. The nature of the differences in the energy balance between first-year (FYI) and multi-year sea ice (MYI) types depends on the characteristics of the ice types being compared. A thick multi-year sea ice floe is shown to be an environment o f(i) lower albedo, (ii) higher net radiation, (iii) larger melt rates and (iv) 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. Five feedback mechanisms, which involve the surface energy balance, are observed to operate in a fully coupled system. 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 atmosphere 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. Negative feedbacks involving the turbulent heat fluxes act to counter any differences in the net radiation of snow between the cloud regimes when averaged over the diurnal cycle. Overcast conditions are effective at limiting refreezing within the snow during the early spring, but melt rate is 22% larger under clear skies later in the season. Hence the environmental conditions associated with cloudcover 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 (i) delay melt by maintaining a high surface albedo if the precipitation is solid, or (ii) accelerate melt by reducing the surface albedo, as is the case for rain. The result of variable environmental forcing on snow covered sea ice of the CAA is a lag of up to 20 days in the timing of accelerated snowmelt within this three-year study. 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.application/pdf20753495 bytesapplication/pdfenCopyright: 1999, Papakyriakou, Timothy Nicholas. All rights reserved.Harvested from Collections CanadaDoctoral Thesis