A fifth site is located 8 km north of the crest. In the meantime we use existing accumulation rates from other studies to derive preliminary estimates of ice thickness change. Preliminary results indicate that there is virtually no net thickness change at four of the five sites. Such a result is incompatible with the slow northward migration of the divide suggested by the University of Washington group. Instead, thinning of the northern flank would tend to cause a southward migration of the divide position.
Further analysis suggests that they can.
We have shown in earlier work that accumulation rates can be derived from coffee-can vertical velocities using the principals of Sorges Law. Applying Sorges Law to data from the site at 30 km north provides an accumulation rate that is substantially larger than existing measurements suggest. When this larger accumulation rate is used in the coffee-can calculations, the result is slow ice sheet thickening of the northern flank at 30 km. A better understanding of the situation will be obtained once beta analyses are complete.