What is it about?
This paper describes glacier mass balance and thinning and potential impacts to domestic water supplies used by Anchorage, Alaska. We used glacier surface elevations from 1957, 2010, and 2015 and surface mass balance measurements from 2008-2015 to understand how this glacier is responding to changes in climate. Most of the volume loss is in the upper elevations of the glacier, coincident with areas where the glacier is still gaining mass on an annual basis. As the surface continues to lower this will have a feedback on the mass balance by decreasing the accumulation in the form of winter snowfall and increasing the summer melt. This will ultimately require at least 6 km of retreat on this ~10 km long glacier just to come into equilibrium with the 2008-2015 climate. Further climate change would reduce that size even further.
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Why is it important?
Eklutna Glacier mass loss has important consequences for runoff to a downstream reservoir that is used—in its entirety—to provide municipal water and hydropower for the city of Anchorage. The runoff from mass loss alone averaged 7 ± 1% of total inflow to the reservoir from 2010–2015, and in 2013 and 2015 reached ~13%. Over the short term (a few tens of years), thinning in the upper reaches of the glacier may increase the runoff due to volume change, although the finite volume of the glacier will limit this contribution over longer time periods.
Perspectives
Traditionally mass-continuity has been used as a glacier-wide constraint to calibrate a mass balance time-series derived from direct surface measurements of accumulation and ablation. In this paper we evaluate mass-continuity as a function of glacier surface elevation, much like many ice-sheet models. This has several advantages. First, it allows us to maximally use high resolution surface elevation data sets with sparse direct measurements of surface mass balance. Second, it is the most direct measure of a glacier's response to climate change, and it allows us to calculate the minimum change in hypsometry required for the glacier to be in equilibrium with the present climate.
Louis C Sass
U.S. Geological Survey
Read the Original
This page is a summary of: Geometry, mass balance and thinning at Eklutna Glacier, Alaska: an altitude-mass-balance feedback with implications for water resources, Journal of Glaciology, January 2017, Cambridge University Press,
DOI: 10.1017/jog.2016.146.
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