Lower Curtis Glacier Annual Survey 1984-2012

The Lower Curtis Glacier is an avalanche fed cirque glacier on Mount Shuksan in the North Cascades of Washington. It is a south facing and low elevation glacier for the range. This is an unusual combination that is supported by the heavy accumulation via avalanching from the upper slopes of Mount Shuksan. The glacier displays a magnificent set of annual layers in its terminus tongue. The terminus tongue is a spectacular wall of seracs that quickly rises 55 m above the bedrock. There are typically 50 layers visible indicating that this most of the ice in the glacier is 50 years of less in age. The glacier advanced from 1950-1985 and has retreated 155 meters from 1987-2009 in the glacier center and 135 meters on average across the front. A longitudinal profile up the middle of the glacier indicates that it thinned 30 meters from 1908-1984 and 15 m from 1984-2012. Because of its heavy accumulation via avalanching the glacier moves rapidly and is quite crevassed at the terminus. Each year we survey the terminus location, measure the mass balance and survey the glacier surface elevation on a cross profile. The video is from footage taken in 2011 and 2012. The annual terminus photographs are from near Lake Ann, the 2003-2012 sequence represents the digital camera era. This coming summer will be our 30 consecutive summer on the glacier and we will see if it is the seventh consecutive summer of wet weather when we are there.

The Lower Curtis Glacier on Mount Shuksan advanced from 1950-1975 and has retreated 150 meters from 1987-2009. A longitudinal profile up the middle of the glacier indicates that it thinned 30 meters from 1908-1984 and 10 m from 1984-2008. Compare the 1908 image taken by Asahel Curtis (glacier named for him) in 1908 and our annual glacier shot in 2003. The thinning has been as large in the accumulation zone as at the terminus, indicating no point to which this glacier can retreat and achieve equilibrium with the present climate. However, the glacier is quite thick, and will take 50-100 years to melt away. This glacier is oriented to the south and fed by avalanches from the Upper Curtis Glacier and the southwestern flank of Mt. Shuksan. This allows it to survive in a deep cirque at just 5600 feet. Because of its heavy accumulation via avalanching the glacier moves rapidly and is quite crevassed at the terminus. Image below is a 2009 sideview, note the annual dark layers in the ice. The number of crevasses in the nearly flat main basin of the glacier has diminished as the glacier has thinned and slowed over the last 20 years. The glacier lost nearly all of its snowcover in several recent years 2005, 2006 and 2009. In one month we will back on this glacier investigating its mass balance and terminus position. It is a key glacier this year, as the winter was quite warm yet wet, spring was not. Thus, snowpack was much below average below 5000 feet and likely above average above 7000 feet, where the transition will be is the key. In the google earth images below Lower Curtis Glacier is in the left center. The terminus is exposed bare glacier ice and is heavily crevassed. Typically the terminus loses its snowcover in mid-June. Below the terminus there are frequent ice and rock falls, so it is best not to go below the terminus. For our measurements we need to, but we always finish by 9 am. .