NIWR at WERC

Mass Balance of Eklutna Glacier

  • Project PI: Roman Dial and Jason Geck
  • Project Student:
  • Keywords: glacier runoff, atmospheric coupling, snowpack, water supply, climate

Alaska’s largest population center, Anchorage, receives 80% of its freshwater and 10–20% of its electricity (hydropower generated) from the glaciated Eklutna basin. As with nearly all glaciers in Alaska, the Eklutna Glacier is rapidly melting as the result of a regional warming trend.

This study aims to improve our understanding of the processes affecting the mass balance (precipitation versus melt) of the Eklutna Glacier. Understanding these driving forces is vital, as this glacier’s runoff serves as an important water resource for the Anchorage area.

Abstract

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

This research aims to further confirm and apply 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 when modeling glacial melt. We have found evidence that the Eklutna Glacier does indeed show non-constant and often inverted lapse rates in its accumulation zone, possibly explaining results of a recent application of the WaSiM model to Eklutna Glacier mass balance. We hypothesize the underestimate of the WaSiM model is due to advective inversions 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 explains both “anomalous” thinning of ice on the Eklutna Glacier noted in a previous study as well as WaSiM’s underestimated prediction of mass wastage. As part of a near-decade old annual field course on glaciology at Alaska Pacific University (APU), we propose to continue monitoring the automated weather station (AWS) currently near the Eklutna’s equilibrium line altitude (ELA) as well as additional temperature and measurement locations deployed at existing ablation stake locations. The proposed research will continue monitoring six accumulation zone sites that match ablation stakes with a suite of sensors matching the ELA AWS (temp, RH, wind speed/direction, melt via sonic ranger). The intermediate sites in elevation between the ELA AWS and ACC AWS will continue to 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 accurately parameterize any and all temperature-index models validated against six measurements of ablation made by APU students participating in applied research.

  • Water and Environmental Research Center (WERC)
  • 437 Duckering
  • 1760 Tanana Loop
  • PO Box 75 5860
  • Fairbanks, AK 99775-5860, USA