COMPARISON OF GLACIER SURFACE VELOCITY FIELDS EXTRACTED FROM HIGH-RESOLUTION SATELLITE IMAGERY WITH GPS-DERIVED POINT VELOCITIES ON THE KENNICOTT GLACIER, WRANGELL MOUNTAINS, ALASKA

Historically, glacier surface velocities have been difficult to constrain. However, the recent development of high-resolution satellite imagery and high-precision GPS have led to a boom in the extraction of ice surface velocities. These data are vital to our understanding of glacier dynamics, glacier erosion, and the response of glaciers to climate change. Our work focuses on the 387 km² Kennicott Glacier in southeastern Alaska, which was a favorite field area for Austin Post’s long-time scientific companion Ed LaChapelle. Their book, Glacier Ice, inspired many of us to explore and observe glaciers using aerial and remotely sensed data.

We extract surface velocity fields for the lower 15 km of the Kennicott Glacier by processing high-resolution (~0.5 m pixel) QuickBird and WorldView imagery using COSI-Corr (Co-registration of Optically Sensed Images and Correlation) software. We use biweekly imagery from the 2013 melt season to calculate two-week average velocities and examine the seasonal evolution of glacier motion over a ~70 km² portion of the ablation zone. We use less frequent imagery dating back to 2004 to calculate annually averaged glacier velocity fields. These velocities are compared with GPS-determined point displacement histories from May 2012 through September 2013 in the same reach, and are interpreted in light of radar constraints on ice thickness. Because the GPS data are primarily available through the melt season, the satellite-derived velocity fields allow us to evaluate the importance of winter versus melt season velocities on this temperate valley glacier. In addition, we examine (1) icefall velocity; (2) supraglacial stream evolution; (3) the locations of inputs to the englacial hydrologic system; and (4) proglacial lake expansion.