Variations of ice bed coupling beneath and beyond ice streams: The force balance

Abstract

A geometrical force balance that links stresses to ice bed coupling along a flow band of an ice sheet was developed in 1988 for longitudinal tension in ice streams and published 4 years later. It remains a work in progress. Now gravitational forces balanced by forces producing tensile, compressive, basal shear, and side shear stresses are all linked to ice bed coupling by the floating fraction of ice that produces the concave surface of ice streams. These lead inexorably to a simple formula showing how varies along these flow bands where surface and bed topography are known: = hO/hI with hO being ice thickness hI at x = 0 for x horizontal and positive upslope from grounded ice margins. This captures the basic fact in glaciology: the height of ice depends on how strongly ice couples to the bed. It shows how far a high convex ice sheet ( = 0) has gone in collapsing into a low flat ice shelf ( = 1). Here captures ice bed coupling under an ice stream and ho captures ice bed coupling beyond ice streams. Copyright 2009 by the American Geophysical Union.