In addition to warming temperatures, topography plays a role in the rapid flow speeds at Columbia Glacier. For several years, the glacier was pinched into a gap. To push through this narrow gap, ice upstream had to speed up, and this faster flow kept pace with calving (the breaking off of icebergs). During the 2007–08 winter, the terminus finally backed up through the gap and the ice slowed down. The calving speed stayed high, though, and the retreat rate accelerated. During the eleven-month period between June 2008 and May 2009, the glacier terminus retreated farther than it had during the previous two years. In all, between June 2006 and May 2009 Columbia Glacier receded almost two miles (about three kilometers), a distance equal to 250 school buses end to end. The retreat was dramatic enough that EIS had to move the camera to keep the glacier terminus in range.

Next: AK-06, Mendenhall (West), Alaska