Abstract
AbstractThe widespread occurrence of snow-ice formation on the pack ice plays a critical role in the mass balance of Antarctic sea ice. The stable isotope composition, ice texture and salinity of eight ice cores, obtained from the Amundsen Sea during the Oden Southern Ocean 2010/11 expedition from late December 2010 to January 2011, were investigated to illustrate the snow-ice growth process and its contribution to sea-ice development. Most previous research has utilized δ18O as an index tracer to determine the percentages of core length that contain meteoric water, i.e. snow ice. However, this standard practice of snow-ice identification might be biased due to normally low-resolution isotopic measurements and mixing/diffusion processes between the snow ice and underlying ice layers. Snow-ice contributions in these ice cores based instead on an updated isotope mixing model are also presented. Depth profiles of ice texture and salinity are described to serve as representations of the structures of these ice cores. Our isotope mixing model produced an average of 15.9% snow-ice contribution for pack ice in the Amundsen Sea, and meteoric water occupying 40% of snow-ice mass for all ice stations. These results are compared to previous investigations of snow-ice occurrence around Antarctica.
Highlights
When the snowpack on sea ice is heavy and thick enough to depress the top surface below sea level, a slush layer or slurry is formed through the mixture of seawater or brine and snow at the base of the snow cover
All ice cores were collected from drifting pack ice, except ice core A12 sampled from fast ice
The depth profiles of stable oxygen isotope, salinity and ice texture of eight sea ice cores are shown in Figure 3, and the data used in this study can be found in Suppleme ntary Material. δ18O values for all sea ice samples vary from 2.3‰ to − 7.3‰
Summary
When the snowpack on sea ice is heavy and thick enough to depress the top surface below sea level, a slush layer or slurry is formed through the mixture of seawater or brine and snow at the base of the snow cover. The snow ice is incorporated into the ice cover after subsequent periods of freezing. In the Antarctic, overall higher snow accumulation on thinner sea ice results in the widespread occurrence of surface flooding and snow-ice formation (Jeffries and others, 1994; Massom and others, 2001). The snow-ice formation is an essential factor for biological productivity within the ice by controlling brine and nutrient flux from seawater to the flooded layer and ice layer below (Ackley and Sullivan, 1994; Fritsen and others, 1994). Lack of knowledge about the snow-ice contribution in Antarctic sea ice could hinder accurate estimates of sea-ice thickness and snow cover depth using remote sensing (Drinkwater and Lytle, 1997; Xie and others, 2013)
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