Characterizing ICESat-2 Snow Depths Over the Boreal Forests and Tundra
of Alaska in Support of the SnowEx 2023 Campaign
Abstract
Recent studies show that the Ice, Clouds, and Land Elevation Satellite-2
(ICESat-2) can achieve decimeter-level accuracy over forested and
mountainous sites in the western United States, as well as over the
glaciers of Alaska. However, there has yet to be an assessment on
ICESat-2 snow depths over the boreal forests and tundra of Alaska, both
of which are significant reservoirs of snow during the winter season. We
present two case studies of retrieving snow depth using ICESat-2 over
Alaska. We focus on two field sites used by the NASA SnowEx 2022/2023
campaigns: Farmer’s Loop/Creamer’s Field near Fairbanks, AK (forest) and
Upper Kuparuk/Toolik on the Arctic North Slope (tundra). When validated
against airborne lidar flown by the University of Alaska, Fairbanks
(UAF), we find median biases of -6.3 to +2.1 cm among three ICESat-2
data products in the tundra region. Biases over the the boreal forest
are somewhat higher at 7.5-13 cm. Utilizing the open source tool
SlideRule, we observe little change in results when filtering by the
ICESat-2 signal photon confidence scheme or by the vegetation filter.
However, uncertainties in snow depth decrease with coarser
Sliderule-derived snow depths. The number of signal photons (i.e.,
signal strength) has an influence on retrievals, with a large number of
photons per ICESat-2 return providing more accurate snow depths. The
initial results are promising, and we expect to expand this effort to
other ICESat-2 overpasses over the SnowEx field sites.