Looking up through the constricted section into the broad, flat, upper basin. White Lice Mountain forms the left (east) side of the constriction, and Peril Peak forms the right (west) side. We think that the constriction acts to govern ice flow out of the over-deepened section up-glacier. As the upper basin is very flat, the total accumulation is very sensitive. Together this results in large fluctuations in surface elevation, which in turn exerts a feedback on the mass balance. My MS in three sentences. Eklutna Glacier, Chugach State Park, Alaska.