Density assumptions for converting geodetic glacier volume change to mass change

Huss, Matthias

doi:10.5194/tc-7-877-2013

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Journal article

Density assumptions for converting geodetic glacier volume change to mass change

Huss, Matthias Department of Geosciences, University of Fribourg, Switzerland

27.05.2013

Published in:

The Cryosphere. - 2013, vol. 7, no. 3, p. 877–887

English The geodetic method is widely used for assessing changes in the mass balance of mountain glaciers. However, comparison of repeated digital elevation models only provides a glacier volume change that must be converted to a change in mass using a density assumption or model. This study investigates the use of a constant factor for the volume-to-mass conversion based on a firn compaction model applied to simplified glacier geometries with idealized climate forcing, and two glaciers with long-term mass balance series. It is shown that the "density" of geodetic volume change is not a constant factor and is systematically smaller than ice density in most cases. This is explained by the accretion/removal of low-density firn layers, and changes in the firn density profile with positive/negative mass balance. Assuming a value of 850 ± 60 kg m⁻³ to convert volume change to mass change is appropriate for a wide range of conditions. For short time intervals (≤3 yr), periods with limited volume change, and/or changing mass balance gradients, the conversion factor can however vary from 0–2000 kg m⁻³ and beyond, which requires caution when interpreting glacier mass changes based on geodetic surveys.

Faculty

Faculté des sciences et de médecine

Department

Département de Géosciences

Language