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Estimating the thickness of ridged sea ice from ship observations in the Ross Sea

Published online by Cambridge University Press:  19 February 2003

TINA TIN ,
MARTIN O. JEFFRIES ,
MIKKO LENSU  and
JUKKA TUHKURI
TINA TIN
Affiliation:
Geophysical Institute, 903 Koyukuk Drive, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
MARTIN O. JEFFRIES
Affiliation:
Geophysical Institute, 903 Koyukuk Drive, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
MIKKO LENSU
Affiliation:
Helsinki University of Technology, Ship Laboratory, PO Box 5300, FIN-02015 HUT, Finland
JUKKA TUHKURI
Affiliation:
Helsinki University of Technology, Laboratory for Mechanics of Materials, PO Box 4100, FIN-02015 HUT, Finland
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Abstract

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 protocol uses a simple formula to calculate the mass of ice in ridges based on surface observations. We present two new formulae and compare these with results from the “Original” formula using data obtained in the Ross Sea in autumn and winter. The new “r-star” formula uses a more realistic ratio of sail and keel areas to transform dimensions of sails to estimates of mean keel areas. As a result, estimates of “equivalent thickness” (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 keel underwater, and the probability that keels may be found under level surfaces. This resulted in estimates of equivalent thickness comparable with the Original formula. Estimates of equivalent thickness at one or two degree latitude resolution are sufficiently accurate for validating sea ice models. Although ridges are small features in the Ross Sea, we have shown that they constitute a significant fraction of the total ice mass.

Keywords

AntarcticaASPeCtpressure ridgessea ice thickness distribution
Type
Research Article
Information
Antarctic Science , Volume 15 , Issue 1 , March 2003 , pp. 47 - 54
Copyright
© Antarctic Science Ltd 2003

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