Estimating the Sea Ice Compressive Strength from Satellite-Derived Sea Ice Drift and NCEP Reanalysis Data

Abstract

Satellite-derived sea ice drift maps and sea level pressure from reanalysis data are used to infer upper and lower bounds on the large-scale compressive strength of Arctic sea ice. To this end, the two datasets are searched for special situations in which the wind forcing and its orientation with respect to the coastline allowed the authors to deduce a mean sea ice compressive strength from simple theory. Many estimates of ice compressive strength were possible for the winter of 1992/93 when the Arctic high was confined to the western Arctic and deep penetration of the Icelandic low produced wind patterns that pushed the ice perpendicular to the coastline in the Beaufort and East Siberian Seas. The winter of 1996/97, on the other hand, was characterized by a well-established Arctic high, producing wind patterns that generally pushed ice along coastlines rather than against them. Results show lower and upper bounds on the sea ice compressive strength parameter of 30 and 40 kN m?2, and 35 and 45 kN m?2, for the winters of 1992/93 and 1996/97, respectively (with a potential bias low of about 10 kN m?2). A tensile strength for sea ice of about 25 kN m?2 is also found in the East Siberian Sea in the first few hundred kilometers from the land, presumably associated with land-fast ice. The proposed mean ice compressive strength estimate is higher than those derived by minimizing the cumulative error between simulated and observed buoy drift trajectories. It is noted that the uncertainties in the estimates derived from models are large (with an unbiased estimate of standard deviation of 8.75 kN m?2). The estimates of yield strength in isotropic compression presented herein are in good agreement with a previous estimate made during the Arctic Ice Dynamic Joint Experiment, and with in situ ice compressive stress measurements made in the Beaufort Sea.