A High-Resolution GPS Motion Record of Variations in the Rate of Glacial Speed Related to Water Inputs on Yahtse Glacier, South Central Alaska 2009-2011

Abstract:

Yahtse Glacier is a temperate grounded tidewater glacier 64 kilometers long, the largest of four that terminate into Icy Bay, Alaska. In 1990 Yahtse completed the retreat phase of the tidewater glacier cycle and began its re-advance, advancing two kilometers thus far. The three-year study of the dynamics of Yahtse began in June 2009 with the initial deployment of five GPS rovers on tetrahedrons, two permanent GPS rovers that were drilled into the ice and two GPS base stations as well as several seismometers and time lapse cameras. We have acquired a three year long time-series of high-resolution GPS data on several stations deployed along the centerline of Yahtse Glacier and in a central strain diamond formation located several meters from the icefall from 2009 - 2011. The GPS motion record revealed multiple short-duration (on the order of days) speed-up events throughout the spring and summer months superimposed on the seasonal acceleration and deceleration of Yahtse Glacier on all three years of observations. Through an analysis of the GPS motion record along with simultaneously collected weather data we found a relationship between the timing of large water input events and the observed speed-up events. This data enables us to understand how the englacial drainage network is developing seasonally and annually. Only through understanding the drainage system numerically will we be able to develop accurate predictions of the glaciers future rate of advance with respect to the changing climate conditions in south central Alaska.