Evaluation of satellite methods for estimating supraglacial lake depth in southwest Greenland
Supraglacial lakes form on the Greenland ice sheet in the melt season (May to October) when meltwater collects in surface depressions on the ice. Supraglacial lakes can act as a control on ice dynamics since, given a large enough volume of water and a favourable stress regime, hydrofracture of the l...
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ftcopernicus:oai:publications.copernicus.org:tcd112991 2023-09-05T13:19:50+02:00 Evaluation of satellite methods for estimating supraglacial lake depth in southwest Greenland Melling, Laura Leeson, Amber McMillan, Malcolm Maddalena, Jennifer Bowling, Jade Glen, Emily Sandberg Sørensen, Louise Winstrup, Mai Lørup Arildsen, Rasmus 2023-08-11 application/pdf https://doi.org/10.5194/tc-2023-103 https://tc.copernicus.org/preprints/tc-2023-103/ eng eng doi:10.5194/tc-2023-103 https://tc.copernicus.org/preprints/tc-2023-103/ eISSN: 1994-0424 Text 2023 ftcopernicus https://doi.org/10.5194/tc-2023-103 2023-08-14T16:24:20Z Supraglacial lakes form on the Greenland ice sheet in the melt season (May to October) when meltwater collects in surface depressions on the ice. Supraglacial lakes can act as a control on ice dynamics since, given a large enough volume of water and a favourable stress regime, hydrofracture of the lake can occur which enables water transfer from the ice surface to the bedrock where it can lubricate the base. The depth (and thus volume) of these lakes is typically estimated by applying a adiative transfer equation (RTE) to optical satellite imagery. This method can be used at scale across entire ice sheets but is poorly validated due to a paucity of in-situ depth data. Here we intercompare supraglacial lake depth detection by ArcticDEM digital elevation models, ICESat-2 photon refraction, and the RTE applied to Sentinel-2 images across five lakes in southwest Greenland. We found good agreement between the ArcticDEM and ICESat-2 approaches (Pearson’s r = 0.98) but found that the RTE overestimates lake depth by up to 153 % using the green band (543–578 nm) and underestimates lake depth by up to 63 % using the red band (650–680 nm). Parametric uncertainty in the RTE estimates is substantial and is dominated by uncertainty in estimates of reflectance at the lakebed which are derived empirically. Our analysis indicates that calculating depth with the RTE using literature-derived values for the parameters introduces significant uncertainty in the retrieval of depth information from optical imagery. Uncertainty in lake depth estimates translates into a poor understanding of total lake volume, which could mean that hydrofracture likelihood is under or over-estimated, in turn affecting ice velocity predictions. Further laboratory studies to constrain spectral radiance loss in the water column, and investigation of the potential effects of cryoconite on the estimation of lakebed reflectance could improve the RTE in its current format. However, we also suggest that future work should explore data-driven approaches to ... Text Greenland Ice Sheet Copernicus Publications: E-Journals Greenland |
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Open Polar |
collection |
Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
Supraglacial lakes form on the Greenland ice sheet in the melt season (May to October) when meltwater collects in surface depressions on the ice. Supraglacial lakes can act as a control on ice dynamics since, given a large enough volume of water and a favourable stress regime, hydrofracture of the lake can occur which enables water transfer from the ice surface to the bedrock where it can lubricate the base. The depth (and thus volume) of these lakes is typically estimated by applying a adiative transfer equation (RTE) to optical satellite imagery. This method can be used at scale across entire ice sheets but is poorly validated due to a paucity of in-situ depth data. Here we intercompare supraglacial lake depth detection by ArcticDEM digital elevation models, ICESat-2 photon refraction, and the RTE applied to Sentinel-2 images across five lakes in southwest Greenland. We found good agreement between the ArcticDEM and ICESat-2 approaches (Pearson’s r = 0.98) but found that the RTE overestimates lake depth by up to 153 % using the green band (543–578 nm) and underestimates lake depth by up to 63 % using the red band (650–680 nm). Parametric uncertainty in the RTE estimates is substantial and is dominated by uncertainty in estimates of reflectance at the lakebed which are derived empirically. Our analysis indicates that calculating depth with the RTE using literature-derived values for the parameters introduces significant uncertainty in the retrieval of depth information from optical imagery. Uncertainty in lake depth estimates translates into a poor understanding of total lake volume, which could mean that hydrofracture likelihood is under or over-estimated, in turn affecting ice velocity predictions. Further laboratory studies to constrain spectral radiance loss in the water column, and investigation of the potential effects of cryoconite on the estimation of lakebed reflectance could improve the RTE in its current format. However, we also suggest that future work should explore data-driven approaches to ... |
format |
Text |
author |
Melling, Laura Leeson, Amber McMillan, Malcolm Maddalena, Jennifer Bowling, Jade Glen, Emily Sandberg Sørensen, Louise Winstrup, Mai Lørup Arildsen, Rasmus |
spellingShingle |
Melling, Laura Leeson, Amber McMillan, Malcolm Maddalena, Jennifer Bowling, Jade Glen, Emily Sandberg Sørensen, Louise Winstrup, Mai Lørup Arildsen, Rasmus Evaluation of satellite methods for estimating supraglacial lake depth in southwest Greenland |
author_facet |
Melling, Laura Leeson, Amber McMillan, Malcolm Maddalena, Jennifer Bowling, Jade Glen, Emily Sandberg Sørensen, Louise Winstrup, Mai Lørup Arildsen, Rasmus |
author_sort |
Melling, Laura |
title |
Evaluation of satellite methods for estimating supraglacial lake depth in southwest Greenland |
title_short |
Evaluation of satellite methods for estimating supraglacial lake depth in southwest Greenland |
title_full |
Evaluation of satellite methods for estimating supraglacial lake depth in southwest Greenland |
title_fullStr |
Evaluation of satellite methods for estimating supraglacial lake depth in southwest Greenland |
title_full_unstemmed |
Evaluation of satellite methods for estimating supraglacial lake depth in southwest Greenland |
title_sort |
evaluation of satellite methods for estimating supraglacial lake depth in southwest greenland |
publishDate |
2023 |
url |
https://doi.org/10.5194/tc-2023-103 https://tc.copernicus.org/preprints/tc-2023-103/ |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland Ice Sheet |
genre_facet |
Greenland Ice Sheet |
op_source |
eISSN: 1994-0424 |
op_relation |
doi:10.5194/tc-2023-103 https://tc.copernicus.org/preprints/tc-2023-103/ |
op_doi |
https://doi.org/10.5194/tc-2023-103 |
_version_ |
1776200637198893056 |