TRACKING ICE RETREAT IN SOUTH CENTRAL ALASKA USING REMOTE SENSING AND GLACIAL GEOLOGY

Glaciers are sensitive to decadal and century-scale warming. Their retreat over the past few hundred years provides a context from which to evaluate ice loss over the last few decades. Along the Gulf of Alaska is one of the largest volumes of land-based ice outside of continental ice sheets and ice loss there has contributed significantly to sea level rise. This study examines tidewater, land-terminating and lake-terminating glaciers from the Kenai Fjords National Park in the south central Alaska and uses LandSat imagery to track ice retreat and advance appended to the record based on glacial moraines. Kenai Fjords National Park is an ideal location for this study as it has multiple types of glaciers and a well documented glacial record.

Retreat from the Little Ice Age Maximum in the 18^th and19^th centuries has generally accelerated over the last hundred years in response to contemporary warming and has been temporarily halted as decadal shifts in the North Pacific have forced minor advances. Initial results show there is a difference in the amount of retreat and advance among the three types of glaciers with tidewater glaciers typically retreating tens of kilometers, whereas land-terminating glaciers have retreated only kilometers over the same interval.

The McCarty tidewater glacier retreated from its 1860 outer moraine more than 24km by 2007. Within this period positive mass balance beginning in the mid 1970s resulted in a short lived period of readvance that persisted through the early 1990s. Similarly, the land terminating Exit Glacier paralleled the readvance pulse following the 1970s shift. Overall, from 1825 to 2006 there is a cumulative retreat of approximately 2 km for Exit Glacier. In contrast, the lake terminating Bear Glacier which had a cumulative retreat of 5km did not advance at this time, likely due to the glacier’s calving into the large proglacial lake. Further investigation will focus on examining the behaviors of additional glaciers from the Kenai Fjords and western Prince William Sound which will lead to a better understanding of glacier behavior in a changing climate.