Thickness gauge results

At the beginning of SHEBA, while trying to find an ice floe to be the experimental site, we discovered that much of the ice was only 1 m thick. This was more than a meter thinner than expected. During October 1997, we installed more than 100 thickness gauges in a wide variety of ice types including first-year ice, ponded ice, unponded multiyear ice, hummocks, new ridges, and old ridges. Ice thickness for these sites ranged from 0.3 m to 8 m. In some cases there was a thin snow cover, in others a deep snow cover. However, for all of their differences and variety these thickness gauge sites shared a common trait; at every site  there was a net thinning of the ice during the SHEBA year.

The figure on the right shows the change in ice thickness over the year for six sites that represent the range of ice conditions found at SHEBA. There is a steady increase in thickness through the winter that gradual tapers in the spring. This is followed by a steep dropoff in thickness during summer melt and another tapering in late summer and early fall.

Directly below is a plot showing results from about 75 stakes. The amount of winter growth and the net change in thickness for the year are plotted as a function of initial ice thickness. Again, for all cases there was a net thinning of the ice. There was also a weak trend that thicker ice had less winter growth and greater net loss for the year.

On the lower right the total surface and bottom melt is plotted as a function of ice thickness. In most cases there was more surface melt than bottom melt. The average surface melt was 55 cm and the average bottom melt was 50 cm. Peak surface melting was in June and July, while bottom ablation peaked in August. These results are preliminary. Information is also available for individual gauges.

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