Frontiers in Earth Science (Oct 2016)
Stikine Icefield Mass Loss Between 2000 and 2013/2014
Abstract
We calculate thinning rates ( frac dh dt ) at the 5,800kmtextsuperscript 2 Stikine Icefield of southeast Alaska fromstacked digital elevation models (DEMs) acquired between 2000 and2013/2014, and glacier velocities between 1985 and 2014 from featuretracking on optical image pairs. We find a mass change rate of -3.3 pm 1.1 Gt yrtextsuperscript -1 between 2000 and 2014, equivalentto an area-averaged elevation change rate of -0.57 pm 0.18 mw.e. yrtextsuperscript -1 . In 2014, land-terminating glaciers are50% of the Stikine Icefield's glaciated area and contribute -0.9 pm 0.4 Gt yrtextsuperscript -1 of mass change (27% of thetotal), while marine-terminating glaciers are only 30% of the totalglaciated area, but contribute -1.5 pm 0.3 Gtyrtextsuperscript -1 (or 45% of total mass change, with theremaining mass loss from lacustrine-terminating glaciers). Weestimate the frontal ablation flux between 2000 and 2014 at the fourlargest marine-terminating glaciers on the Stikine Icefield (covering90 to 95% of the marine-terminating glaciated area) using our glaciervelocities and maps of fjord bathymetry to estimate terminus cross sections and glacier thicknesses. The combined 2014 frontal ablation flux of these fourglaciers is 1.18 pm 0.14 Gt yrtextsuperscript -1 , which mayaccount for the difference in average mass loss between marine- andland-terminating glaciers on the Stikine Icefield. The Stikine andadjacent Juneau Icefields have very different mass loss contributionsfrom marine-terminating glaciers (45% vs. effectively 0%), but bothhave area-averaged elevation change rates that are less negative thanAlaska-wide estimates, which is surprising for these southernmosticefields in Alaska.
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