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 complementary 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...
Published in: | The Cryosphere |
---|---|
Main Authors: | , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Copernicus Publications
2023
|
Subjects: | |
Online Access: | https://hdl.handle.net/10037/31859 https://doi.org/10.5194/tc-17-4165-2023 |
id |
ftunivtroemsoe:oai:munin.uit.no:10037/31859 |
---|---|
record_format |
openpolar |
spelling |
ftunivtroemsoe:oai:munin.uit.no:10037/31859 2023-12-24T10:12:07+01:00 Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice Dawson, Geoffrey J. Landy, Jack Christopher 2023-09-27 https://hdl.handle.net/10037/31859 https://doi.org/10.5194/tc-17-4165-2023 eng eng Copernicus Publications The Cryosphere Dawson, Landy. Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice. The Cryosphere. 2023 FRIDAID 2181446 doi:10.5194/tc-17-4165-2023 1994-0416 1994-0424 https://hdl.handle.net/10037/31859 Attribution 4.0 International (CC BY 4.0) openAccess Copyright 2023 The Author(s) https://creativecommons.org/licenses/by/4.0 Journal article Tidsskriftartikkel Peer reviewed publishedVersion 2023 ftunivtroemsoe https://doi.org/10.5194/tc-17-4165-2023 2023-11-30T00:08:24Z The CryoSat-2 radar altimeter and ICESat-2 laser altimeter can provide complementary 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 CryoSat2 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 CryoSat2 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 ICESat2 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 the melt pond fraction derived from Sentinel-3 Ocean and Land Color Instrument (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 Arctic Sea ice The Cryosphere University of Tromsø: Munin Open Research Archive Arctic The Cryosphere 17 9 4165 4178 |
institution |
Open Polar |
collection |
University of Tromsø: Munin Open Research Archive |
op_collection_id |
ftunivtroemsoe |
language |
English |
description |
The CryoSat-2 radar altimeter and ICESat-2 laser altimeter can provide complementary 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 CryoSat2 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 CryoSat2 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 ICESat2 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 the melt pond fraction derived from Sentinel-3 Ocean and Land Color Instrument (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 J. Landy, Jack Christopher |
spellingShingle |
Dawson, Geoffrey J. Landy, Jack Christopher Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice |
author_facet |
Dawson, Geoffrey J. Landy, Jack Christopher |
author_sort |
Dawson, Geoffrey J. |
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://hdl.handle.net/10037/31859 https://doi.org/10.5194/tc-17-4165-2023 |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic Arctic Sea ice The Cryosphere |
genre_facet |
Arctic Arctic Sea ice The Cryosphere |
op_relation |
The Cryosphere Dawson, Landy. Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice. The Cryosphere. 2023 FRIDAID 2181446 doi:10.5194/tc-17-4165-2023 1994-0416 1994-0424 https://hdl.handle.net/10037/31859 |
op_rights |
Attribution 4.0 International (CC BY 4.0) openAccess Copyright 2023 The Author(s) https://creativecommons.org/licenses/by/4.0 |
op_doi |
https://doi.org/10.5194/tc-17-4165-2023 |
container_title |
The Cryosphere |
container_volume |
17 |
container_issue |
9 |
container_start_page |
4165 |
op_container_end_page |
4178 |
_version_ |
1786172679503478784 |