RESPONSE OF SULPHUR CREEK ROCK GLACIER, WYOMING TO CLIMATE CHANGE DURING THE PAST 124 YEARS

Sulfur Creek Rock Glacier (SCRG) is the largest (2.5 km long) of several debris-covered glaciers in the northern Absaroka Mountains, Wyoming. At present a small, dirty glacier hugs the cirque headwall and a large depression with exposures of striated bedrock separates it from the still flowing down-valley debris-covered portion of the glacier.

In 1893 during the Hague Survey (USGS Folio 52) of the area east of Yellowstone Park T. A. Jaggar, Jr. took several photographs of what he called Sunlight Glacier. At that time, the cirque was occupied by a bulging glacier that was continuous down valley to the debris-covered glacier. Two photos show the steep front of the rock glacier where it had advanced into the forest. As of 1996 when we visited SCRG the front had advanced about 15 m in 103 years, or about 15 cm/yr. While the relatively clean part of the glacier at the head has thinned and separated from the lower glacier due to climate warming, the debris-covered part is insulated from the climate message and still is advancing.

Movement will likely continue for decades. Measurements on nearby Galena Creek Rock Glacier indicate that a debris mantle of about 1.0-1.5 m thick reduces the ablation rate of underlying ice to ~5 to 15 cm/yr.

Next year, 2018, will be 125 years since Jaggar’s photos were taken. They should be repeated.