Estimating Supraglacial Lake Depth with Landsat 8

Abstract:

Supraglacial lakes play a significant role in glacial hydrological systems – for example, transporting water to the glacier bed in Greenland or leading to ice shelf fracture and disintegration in Antarctica. To investigate these important processes, multispectral remote sensing provides multiple methods for estimating supraglacial lake depth – either through single-band or band-ratio methods, both empirical and physically-based. Landsat 8 is the newest satellite in the Landsat series. With new bands, higher dynamic range, and higher radiometric resolution, the Operational Land Imager (OLI) aboard Landsat 8 has a lot of potential.

This study uses in situ reflectance spectra and depth measurements to investigate the ability of Landsat 8 to estimate lake depths using multiple methods, as well as quantify improvements over Landsat 7’s ETM+. Similar to other sensors, single-band depth estimates worked well with OLI’s green band (Band 3, 530-590 nm; r = 0.78, RMSE = 0.78 m). The narrower range of OLI’s panchromatic band (Band 8, 500-680 nm) results in good theoretical performance, as well (r = 0.84, RMSE = 0.63 m). Band-ratio methods perform best when taking advantage of OLI’s new “coastal aerosol” band (Band 1, 430-450 nm), paired with either green (r = 0.92, RMSE = 0.38 m) or panchromatic (r = 0.95, RMSE = 0.32 m).

Promising methods are applied to Landsat 8 OLI imagery of case study areas in Greenland allowing calculation of regional volume estimates using 2013 and 2014 summer-season imagery. Lake depth estimates from band ratio methods are consistent with single-band depth estimates in actual Landsat 8 imagery. Altimetry from NASA’s Operation IceBridge and high resolution WorldView2 DEMs are used to validate lake depth estimates. Optimal methods for supraglacial lake depth estimation with Landsat 8 will be discussed.