Evaluation of snow depth retrievals from ICESat-2 using airborne laser-scanning data

The unprecedented precision of the altimetry satellite ICESat-2 and the increasing availability of high-resolution elevation datasets open new opportunities to measure snow depth in mountains, a critical variable for ecosystems and water resources monitoring. We retrieved snow depth over the upper Tuolumne basin (California, USA) for three years by differencing ICESat-2 ATL06 snow-on elevations and various snow-off elevation sources, including ATL06 and external digital elevation models. Snow depth derived from ATL06 data only (snow-on and snow-off) provided a poor temporal and spatial coverage, limiting its utility. However, using airborne lidar or satellite photogrammetry elevation models as snow-off elevation source yielded an accuracy of ~0.2 m (bias), a precision of ~0.5 m for low slopes and ~1.2 m for steeper areas, compared to eight reference airborne lidar snow depth maps. The snow depth derived from ICESat-2 ATL06 will help address the challenge of measuring the snow depth in unmonitored mountainous areas.</p

bessoh2/icesat2_sr: 1.1.1

&lt;p&gt;Status at the time of publication.&lt;/p&gt

Impacts of the sediment-laden Elwha River plume on light attenuation in the water column and kelp habitat

River dam removals are a form of sediment supply to the sub-tidal areas near river mouths. Suspended sediment in the sub-tidal water column can attenuate light, decreasing the amount of light available to seabed photosynthesizers, but not much is known about the effects of sediment plume light attenuation on kelp growth. During a recent dam removal project on the Elwha River, kelp densities in the sub-tidal region declined. In this study we evaluate trends in kelp growth since dam removal on the Elwha River began, using dive surveys from 2010 to 2013, and relate these trends to long-term river turbidity and light intensity data obtained during a 3-day study period in April 2014. The results suggest that the river plume attenuates light and has been at least partially responsible for decreases in kelp densities, but that this is not the sole determining factor in kelp growth. Another factor hypothesized to influence kelp growth is a difference in substrate size on either side of the river mouth

bessoh2/icesat2_sr: v1.0.0

This is the repository status at the time of publication

Impacts of the sediment-laden Elwha River plume on light attenuation in the water column and kelp habitat

River dam removals are a form of sediment supply to the sub-tidal areas near river mouths. Suspended sediment in the sub-tidal water column can attenuate light, decreasing the amount of light available to seabed photosynthesizers, but not much is known about the effects of sediment plume light attenuation on kelp growth. During a recent dam removal project on the Elwha River, kelp densities in the sub-tidal region declined. In this study we evaluate trends in kelp growth since dam removal on the Elwha River began, using dive surveys from 2010 to 2013, and relate these trends to long-term river turbidity and light intensity data obtained during a 3-day study period in April 2014. The results suggest that the river plume attenuates light and has been at least partially responsible for decreases in kelp densities, but that this is not the sole determining factor in kelp growth. Another factor hypothesized to influence kelp growth is a difference in substrate size on either side of the river mouth

A New Snow Depth Measurement Technique using ICESat-2 SlideRule in the Western U.S.

Thesis (Master's)--University of Washington, 2022Snow depth is highly variable across watersheds, yet most snow depth data in the Western U.S. come from sparse point measurements. The water resources community is in need of more spatially representative snow depth data for improved basin-wide snow depth estimates. The NASA ICESat-2 mission is a polar-orbiting laser altimetry satellite launched in October 2018 with the primary goal of measuring ice sheet mass changes at the poles. Previous studies have shown that standard ICESat-2 data products have the potential to provide snow depth measurements of varying accuracy depending on factors such as surface slope and canopy cover. In this study we show that snow depth measurements can be improved using a new on-demand data processing and customization tool named ICESat-2 SlideRule, through which user-specified processing parameters can be used to produce a custom data product optimized for specific scientific aims outside the original goals of the mission. When combined with snow-off Digital Terrain Models (DTMs) from airborne lidar observations, snow-on ICESat-2 SlideRule observations have the potential to provide a new snow depth dataset across the Western US and the globe. Here we investigate the accuracy of ICESat-2 SlideRule snow depths compared to reference in situ snow telemetry and aerial lidar snow depth observations at two locations with varying terrain characteristics: the upper Tuolumne River watershed, CA and the Methow Valley, WA. We observe strong agreement between the ICESat-2 SlideRule and reference snow depth measurements at both sites, with median residuals of about 0.2 m and 0.4 m in the upper Tuolumne River watershed and the Methow Valley, respectively. Basin-wide aggregation is found to be a better method for ICESat-2 SlideRule calculations than is individual point comparison. Differences in accuracy between sites are attributed to differences in terrain characteristics and the spatial distribution of these characteristics. The ICESat-2 SlideRule data used in this study produced more accurate snow depth results than those found by previous studies using standard ICESat-2 data products in mid-latitude mountainous regions. Therefore, we strongly recommend the use of SlideRule to process ICESat-2 data in such regions and conclude that these data can provide valuable snow depth measurements for areas where high-resolution DTMs are available