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Glacier-specific elevation changes in parts of western Alaska


Le Bris, Raymond; Paul, Frank (2015). Glacier-specific elevation changes in parts of western Alaska. Annals of Glaciology, 56(70):184-192.

Abstract

The meltwater from glaciers in Alaska contributes strongly to global sea-level rise, but accurate determination is challenging as only two comparatively small glaciers have long-term measurements of annual mass balance (Gulkana and Wolverine). Simple upscaling of their values to the entire region is error-prone as their representativeness is unknown and might be biased. Alternatively, differencing digital elevation models (DEMs) from two epochs provides overall volume changes for a longer period of time that can be converted to mass changes using appropriate density assumptions. Here we combine outlines from two glacier inventories to determine glacier-specific elevation changes over a 50 year period for 3180 glaciers in western Alaska using DEM differencing. This allows us to determine the representativeness of the land-terminating Gulkana and Wolverine Glaciers for the entire region and to exclude calving glaciers (marine and lacustrine) from the sample. Mean changes for all land-terminating, lake-terminating and tidewater glaciers are –0.23 ± 0.44, –0.63 ± 0.40 and –0.64 ± 0.66ma⁻¹, respectively, and –0.7 and –0.6ma⁻¹ for the two mass-balance or benchmark glaciers. Thus fortuitously their changes better represent calving glaciers and the overall mean (–0.63 ± 1.14ma⁻¹) than the change of land-terminating glaciers, i.e. they are not representative for their own type. Different methods of considering potential DEM artefacts provide variable mean changes but the same general result.

Abstract

The meltwater from glaciers in Alaska contributes strongly to global sea-level rise, but accurate determination is challenging as only two comparatively small glaciers have long-term measurements of annual mass balance (Gulkana and Wolverine). Simple upscaling of their values to the entire region is error-prone as their representativeness is unknown and might be biased. Alternatively, differencing digital elevation models (DEMs) from two epochs provides overall volume changes for a longer period of time that can be converted to mass changes using appropriate density assumptions. Here we combine outlines from two glacier inventories to determine glacier-specific elevation changes over a 50 year period for 3180 glaciers in western Alaska using DEM differencing. This allows us to determine the representativeness of the land-terminating Gulkana and Wolverine Glaciers for the entire region and to exclude calving glaciers (marine and lacustrine) from the sample. Mean changes for all land-terminating, lake-terminating and tidewater glaciers are –0.23 ± 0.44, –0.63 ± 0.40 and –0.64 ± 0.66ma⁻¹, respectively, and –0.7 and –0.6ma⁻¹ for the two mass-balance or benchmark glaciers. Thus fortuitously their changes better represent calving glaciers and the overall mean (–0.63 ± 1.14ma⁻¹) than the change of land-terminating glaciers, i.e. they are not representative for their own type. Different methods of considering potential DEM artefacts provide variable mean changes but the same general result.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Geography
Dewey Decimal Classification:910 Geography & travel
Language:English
Date:2015
Deposited On:21 Jan 2016 12:49
Last Modified:28 Apr 2017 02:46
Publisher:International Glaciological Society
ISSN:0260-3055
Publisher DOI:https://doi.org/10.3189/2015AoG70A227

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