Estimating the thickness of ridged sea ice from ship observationsin the Ross Sea

[摘要] Ship-based observations of sea ice thickness using the Antarctic Sea Ice Processes and Climate(ASPeCt) protocol provide information on ice thickness distribution at relatively low cost. This protocoluses a simple formula to calculate the mass of ice in ridges based on surface observations. We present twonew formulae and compare these with results from the “Original” formula using data obtained in the RossSea in autumn and winter. The new “r-star” formula uses a more realistic ratio of sail and keel areas totransform dimensions of sails to estimates of mean keel areas. As a result, estimates of “equivalentthickness” (i.e. mean thickness of ice in ridged areas) increased by over 200%. The new “Probability”formula goes one step further, by incorporating the probability that a sail is associated with a keelunderwater, and the probability that keels may be found under level surfaces. This resulted in estimates ofequivalent thickness comparable with the Original formula. Estimates of equivalent thickness at one or twodegree latitude resolution are sufficiently accurate for validating sea ice models. Although ridges are smallfeatures in the Ross Sea, we have shown that they constitute a significant fraction of the total ice mass.

[学科分类] 自然科学（综合）