Abstract. Snow on Antarctic sea ice plays a complex and highly variable role in air-sea-ice interaction processes and the Earth's climate system. Using data collected mostly during the past 10 years, this paper reviews the following topics: snow thickness and snow type and their geographical and seasonal variations; snow grain size, density, and salinity; frequency of occurrence of slush; thermal conductivity, snow surface temperature, and temperature gradients within snow; and the effect of snow thickness on albedo. Major findings include large regional and seasonal differences in snow properties and thicknesses; the consequences of thicker snow and thinner ice in the Antarctic relative to the Arctic (e.g., the importance of flooding and snow-ice formation); the potential impact of increasing snowfall resulting from global climate change; lower observed values of snow thermal conductivity than those typically used in models; periodic large-scale melt in winter; and the contrast in summer melt processes between the Arctic and the Antarctic. Both climate modeling and remote sensing would benefit by taking account of the differences between the two polar regions. INTRODUCTIONAt maximum extent each year (September-October), sea ice covers a vast area of the Southern Ocean (---19 million km2), attaining latitudes as far north as ---55øS [Gloersen et al., 1992]. In so doing, it profoundly alters the exchange of energy and mass between ocean and atmosphere and forms an integral part of the global climate system. These effects are significantly amplified by the presence of an insulative snow cover which is itself highly variable in thickness and properties. Persistently strong winds redistribute the snow, and its properties [Gordon and Huber, 1990] on snow distribution and properties have only been conducted in the past 5-10 years. These studies are beginning to establish the full significance of snow on Antarctic sea ice as a key component of the global climate system. In this paper we review the major findings. Section 2 is a summary of snow data from five Antarctic sectors (designated by Gloersen et al. [1992]), namely, the Weddell Sea (20øE-60øW), the Indian Ocean (20øE-90øE), the western Pacific Ocean (90øE-160øE), the Ross Sea (160øE-140øW), and the Bellingshausen and Amundsen Seas (140øW-60øW), as shown in Figure 1. The Indian and western Pacific Ocean sectors are collectively referred to as the East Antarctic sector. Section 3 assesses the significance of snow in the air-sea-ice interaction system. New findings have significant implications for modeling (both physical and biological) and remotesensing studies of Antarctic sea ice. Gaps in our current knowledge are identified. Finally, the possible enhanced role of snow under global warming conditions is examined. Throughout, snow is described using the combined morphological and process-oriented classification of snow types of Colbeck et al. [1990] As a result, thickness may not be directly related to either the frequency or duration of snowfall.Mean snow thi...
Over the past 37 years, satellite records show an increase in Antarctic sea ice cover that is most pronounced in the period of sea ice growth. This trend is dominated by increased sea ice coverage in the western Ross Sea, and is mitigated by a strong decrease in the Bellingshausen and Amundsen seas. The trends in sea ice areal coverage are accompanied by related trends in yearly duration. These changes have implications for ecosystems, as well as global and regional climate. In this review, we summarise the research to date on observing these trends, identifying their drivers, and assessing the role of anthropogenic climate change. Whilst the atmosphere is thought to be the primary driver, the ocean is also essential in explaining the seasonality of the trend patterns. Detecting an anthropogenic signal in Antarctic sea ice is particularly challenging for a number of reasons: the expected response is small compared to the very high natural variability of the system; the observational record is relatively short; and the ability of global coupled climate models to faithfully represent the complex Antarctic climate system is in doubt.
Understanding the causes of recent catastrophic ice shelf disintegrations is a crucial step towards improving coupled models of the Antarctic Ice Sheet and predicting its future state and contribution to sea-level rise. An overlooked climate-related causal factor is regional sea ice loss. Here we show that for the disintegration events observed (the collapse of the Larsen A and B and Wilkins ice shelves), the increased seasonal absence of a protective sea ice buffer enabled increased flexure of vulnerable outer ice shelf margins by ocean swells that probably weakened them to the point of calving. This outer-margin calving triggered wider-scale disintegration of ice shelves compromised by multiple factors in preceding years, with key prerequisites being extensive flooding and outer-margin fracturing. Wave-induced flexure is particularly effective in outermost ice shelf regions thinned by bottom crevassing. Our analysis of satellite and ocean-wave data and modelling of combined ice shelf, sea ice and wave properties highlights the need for ice sheet models to account for sea ice and ocean waves.
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