Water Resources Research Act Program

Details for Project ID 2016AK133B

Variable lapse rates and the mass balance of a well-studied glacier in south-central Alaska

Institute: Alaska
Year Established: 2016 Start Date: 2016-03-01 End Date: 2017-02-28
Total Federal Funds: $19,920 Total Non-Federal Funds: $41,671

Principal Investigators: Roman Dial, Jason Geck

Abstract: This proposal seeks funding for student-focused field work to test a hypothesis of coupled glacier-surface atmospheric dynamics on the Eklutna Glacier, near Anchorage, Alaska’s largest city. The Eklutna Glacier’s runoff provides hydropower supplying 10-20% of the electricity and 80-90% of the drinking water for Anchorage. Like nearly all glaciers in the state of Alaska, the Eklutna Glacier is rapidly melting as the result of regional warming. The link between the speed of glacial mass wastage and regional temperature change is made through the general relationship of temperature of still air above a terrestrial surface and the elevation of that surface. The relationship between elevation and temperature is generally considered a negative, linear one, such that the slope of the line between the two – the environmental lapse rate – is both constant and negative. This assumed constant relationship is conveniently and consistently used across four long-term, well-studied glaciers in Alaska that are measured for mass balance, three of which are glaciers that form on the leeward side of coastal mountains. We have found evidence over two non-consecutive seasons that both melt and lapse rate are inverted for more than half the melt season on a leeward-glacier of a coastal mountain range. We hypothesize this is due to an advective inversion as warm, moist air-masses move off the Gulf of Alaska, over the first ridge of high mountains and then descend, warming at the adiabatic lapse rate. This inversion may explain a seemingly anomalous thinning of ice on the Eklutna Glacier, one of the three well-studied, leeward coastal glaciers in Alaska. As part of a near-decade old annual field course on glaciology at Alaska Pacific University (APU), we propose to expand from one meteorological station (WxSta) currently near the Eklutna’s equilibrium line altitude (ELA) to additional temperature measurement locations deployed at existing ablation stake locations. The uppermost site at an accumulation zone ablation stake (ACC) will support a suite of sensors matching the ELA WxSta (temp, RH, wind speed/direction, melt via sonic ranger). Intermediate sites in elevation between the ELA WxSta and ACC WxSta will record temperature within radiation shields elevated 2 m above the snow surface throughout the melt season. By using variable daily lapse rates we will be able to more fully parameterize a fully distributed temperature-index model validated against six measurements of ablation made by APU students participating in applied research.