Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice
The CryoSat-2 radar altimeter and ICESat-2 laser altimeter can provide complimentary measurements of the freeboard and thickness of Arctic sea ice. However, both sensors face significant challenges for accurately measuring the ice freeboard when the sea ice is melting in summer months. Here, we used...
Main Authors: | , |
---|---|
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Copernicus Publications
2023
|
Subjects: | |
Online Access: | https://doi.org/10.5194/egusphere-2023-31 https://noa.gwlb.de/receive/cop_mods_00064520 https://egusphere.copernicus.org/preprints/egusphere-2023-31/egusphere-2023-31.pdf |
id |
ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00064520 |
---|---|
record_format |
openpolar |
spelling |
ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00064520 2023-05-15T15:00:41+02:00 Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice Dawson, Geoffrey Landy, Jack 2023-01 electronic https://doi.org/10.5194/egusphere-2023-31 https://noa.gwlb.de/receive/cop_mods_00064520 https://egusphere.copernicus.org/preprints/egusphere-2023-31/egusphere-2023-31.pdf eng eng Copernicus Publications https://doi.org/10.5194/egusphere-2023-31 https://noa.gwlb.de/receive/cop_mods_00064520 https://egusphere.copernicus.org/preprints/egusphere-2023-31/egusphere-2023-31.pdf https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/restrictedAccess CC-BY article Verlagsveröffentlichung article Text doc-type:article 2023 ftnonlinearchiv https://doi.org/10.5194/egusphere-2023-31 2023-01-23T00:13:29Z The CryoSat-2 radar altimeter and ICESat-2 laser altimeter can provide complimentary measurements of the freeboard and thickness of Arctic sea ice. However, both sensors face significant challenges for accurately measuring the ice freeboard when the sea ice is melting in summer months. Here, we used crossover points between CryoSat-2 and ICESat-2 to compare elevation retrievals over summer sea ice between 2018–2021. We focused on the electromagnetic (EM) bias documented in CryoSat-2 measurements, associated with surface melt ponds over summer sea ice which cause the radar altimeter to underestimate elevation. The laser altimeter of ICESat-2 is not susceptible to this bias, but has other biases associated with melt ponds. So, we compared the elevation difference and reflectance statistics between the two satellites. We found that CryoSat-2 underestimated elevation compared to ICESat-2 by a median difference of 2.4 cm and by a median absolute deviation of 5.3 cm, while the differences between individual ICESat-2 beams and CryoSat-2 ranged between 1–3.5 cm. Spatial and temporal patterns of the bias were compared to surface roughness information derived from the ICESat-2 elevation data, the ICESat-2 photon rate (surface reflectivity), the CryoSat-2 backscatter and melt pond fraction derived from Seintnel-3 OLCI data. We found good agreement between theoretical predictions of the CryoSat-2 EM melt pond bias and our new observations; however, at typical roughness <0.1 m the experimentally measured bias was larger (5–10 cm) compared to biases resulting from the theoretical simulations (0–5 cm). This intercomparison will be valuable for interpreting and improving the summer sea ice freeboard retrievals from both altimeters. Article in Journal/Newspaper Arctic Sea ice Niedersächsisches Online-Archiv NOA Arctic |
institution |
Open Polar |
collection |
Niedersächsisches Online-Archiv NOA |
op_collection_id |
ftnonlinearchiv |
language |
English |
topic |
article Verlagsveröffentlichung |
spellingShingle |
article Verlagsveröffentlichung Dawson, Geoffrey Landy, Jack Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice |
topic_facet |
article Verlagsveröffentlichung |
description |
The CryoSat-2 radar altimeter and ICESat-2 laser altimeter can provide complimentary measurements of the freeboard and thickness of Arctic sea ice. However, both sensors face significant challenges for accurately measuring the ice freeboard when the sea ice is melting in summer months. Here, we used crossover points between CryoSat-2 and ICESat-2 to compare elevation retrievals over summer sea ice between 2018–2021. We focused on the electromagnetic (EM) bias documented in CryoSat-2 measurements, associated with surface melt ponds over summer sea ice which cause the radar altimeter to underestimate elevation. The laser altimeter of ICESat-2 is not susceptible to this bias, but has other biases associated with melt ponds. So, we compared the elevation difference and reflectance statistics between the two satellites. We found that CryoSat-2 underestimated elevation compared to ICESat-2 by a median difference of 2.4 cm and by a median absolute deviation of 5.3 cm, while the differences between individual ICESat-2 beams and CryoSat-2 ranged between 1–3.5 cm. Spatial and temporal patterns of the bias were compared to surface roughness information derived from the ICESat-2 elevation data, the ICESat-2 photon rate (surface reflectivity), the CryoSat-2 backscatter and melt pond fraction derived from Seintnel-3 OLCI data. We found good agreement between theoretical predictions of the CryoSat-2 EM melt pond bias and our new observations; however, at typical roughness <0.1 m the experimentally measured bias was larger (5–10 cm) compared to biases resulting from the theoretical simulations (0–5 cm). This intercomparison will be valuable for interpreting and improving the summer sea ice freeboard retrievals from both altimeters. |
format |
Article in Journal/Newspaper |
author |
Dawson, Geoffrey Landy, Jack |
author_facet |
Dawson, Geoffrey Landy, Jack |
author_sort |
Dawson, Geoffrey |
title |
Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice |
title_short |
Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice |
title_full |
Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice |
title_fullStr |
Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice |
title_full_unstemmed |
Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice |
title_sort |
comparing elevation and backscatter retrievals from cryosat-2 and icesat-2 over arctic summer sea ice |
publisher |
Copernicus Publications |
publishDate |
2023 |
url |
https://doi.org/10.5194/egusphere-2023-31 https://noa.gwlb.de/receive/cop_mods_00064520 https://egusphere.copernicus.org/preprints/egusphere-2023-31/egusphere-2023-31.pdf |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic Sea ice |
genre_facet |
Arctic Sea ice |
op_relation |
https://doi.org/10.5194/egusphere-2023-31 https://noa.gwlb.de/receive/cop_mods_00064520 https://egusphere.copernicus.org/preprints/egusphere-2023-31/egusphere-2023-31.pdf |
op_rights |
https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/restrictedAccess |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.5194/egusphere-2023-31 |
_version_ |
1766332767431294976 |