Improving estimates of ice sheet elevation change derived from AltiKa and CryoSat-2 satellite radar altimetry
While satellite Ku-band (13.5 GHz) radar altimetry has been used since the 1990s to track changes in the Greenland and Antarctic ice sheets' shape, the launch of AltiKa in 2013 provided the first opportunity to use data from higher frequency Ka-band (36 GHz) and compare it to contemporaneous Ku...
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ftwhiterose:oai:etheses.whiterose.ac.uk:29184 2023-05-15T13:50:33+02:00 Improving estimates of ice sheet elevation change derived from AltiKa and CryoSat-2 satellite radar altimetry Otosaka, Inès Natsuki 2021-07 https://etheses.whiterose.ac.uk/29184/ unknown Otosaka, Inès Natsuki orcid:0000-0001-9740-3735 (2021) Improving estimates of ice sheet elevation change derived from AltiKa and CryoSat-2 satellite radar altimetry. PhD thesis, University of Leeds. Thesis NonPeerReviewed 2021 ftwhiterose 2023-01-30T21:28:51Z While satellite Ku-band (13.5 GHz) radar altimetry has been used since the 1990s to track changes in the Greenland and Antarctic ice sheets' shape, the launch of AltiKa in 2013 provided the first opportunity to use data from higher frequency Ka-band (36 GHz) and compare it to contemporaneous Ku-band CryoSat-2 data. In this thesis, I develop novel methods and datasets, based on the processing of Ku-band CryoSat-2 and Ka-band AltiKa data, to improve our ability to detect and interpret trends in elevation change from satellite radar altimetry. First, I produced an assessment of higher-frequency Ka-band AltiKa data in West Antarctica. By developing a new slope correction algorithm and applying a least-square model fit to AltiKa surface elevation measurements, I demonstrated that AltiKa detects trends in surface elevation in good agreement with coincident Ku-band CryoSat-2 and airborne laser data within 0.6 ± 2.4 cm/yr and 0.1 ± 0.1 cm/yr, respectively, showing that trends in penetration are minor in this region. Using this new dataset, I showed that surface lowering at Pine Island Glacier has fallen by 9% since the 2000s, while at Thwaites Glacier it has risen by 43%. Next, I examined the impact of surface melting on firn stratigraphy and radar penetration in West Central Greenland by using a combination of airborne radar data, in-situ firn density measurements, and firn densification models. I showed that surface melt strongly affects the degree of radar penetration into the firn, with the largest fluctuations recorded after the extreme melt event of 2012, which caused a 6.2 ± 2.4 m reduction in Ku-band radar penetration. I further assessed different methods to mitigate the effect of fluctuations in radar penetration on surface heights and showed that using threshold retracking algorithms results in surface heights to within 14 cm from coincident airborne laser data. In addition, I showed that over this transect, Ka-band radar penetration is half that of coincident Ku-band data. Finally, I used a decade of ... Thesis Antarc* Antarctic Antarctica glacier Greenland Ice Sheet Pine Island Pine Island Glacier Thwaites Glacier West Antarctica White Rose eTheses Online (Universities Leeds, Sheffield, York) Antarctic Greenland Pine Island Glacier ENVELOPE(-101.000,-101.000,-75.000,-75.000) Thwaites Glacier ENVELOPE(-106.750,-106.750,-75.500,-75.500) West Antarctica |
institution |
Open Polar |
collection |
White Rose eTheses Online (Universities Leeds, Sheffield, York) |
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ftwhiterose |
language |
unknown |
description |
While satellite Ku-band (13.5 GHz) radar altimetry has been used since the 1990s to track changes in the Greenland and Antarctic ice sheets' shape, the launch of AltiKa in 2013 provided the first opportunity to use data from higher frequency Ka-band (36 GHz) and compare it to contemporaneous Ku-band CryoSat-2 data. In this thesis, I develop novel methods and datasets, based on the processing of Ku-band CryoSat-2 and Ka-band AltiKa data, to improve our ability to detect and interpret trends in elevation change from satellite radar altimetry. First, I produced an assessment of higher-frequency Ka-band AltiKa data in West Antarctica. By developing a new slope correction algorithm and applying a least-square model fit to AltiKa surface elevation measurements, I demonstrated that AltiKa detects trends in surface elevation in good agreement with coincident Ku-band CryoSat-2 and airborne laser data within 0.6 ± 2.4 cm/yr and 0.1 ± 0.1 cm/yr, respectively, showing that trends in penetration are minor in this region. Using this new dataset, I showed that surface lowering at Pine Island Glacier has fallen by 9% since the 2000s, while at Thwaites Glacier it has risen by 43%. Next, I examined the impact of surface melting on firn stratigraphy and radar penetration in West Central Greenland by using a combination of airborne radar data, in-situ firn density measurements, and firn densification models. I showed that surface melt strongly affects the degree of radar penetration into the firn, with the largest fluctuations recorded after the extreme melt event of 2012, which caused a 6.2 ± 2.4 m reduction in Ku-band radar penetration. I further assessed different methods to mitigate the effect of fluctuations in radar penetration on surface heights and showed that using threshold retracking algorithms results in surface heights to within 14 cm from coincident airborne laser data. In addition, I showed that over this transect, Ka-band radar penetration is half that of coincident Ku-band data. Finally, I used a decade of ... |
format |
Thesis |
author |
Otosaka, Inès Natsuki |
spellingShingle |
Otosaka, Inès Natsuki Improving estimates of ice sheet elevation change derived from AltiKa and CryoSat-2 satellite radar altimetry |
author_facet |
Otosaka, Inès Natsuki |
author_sort |
Otosaka, Inès Natsuki |
title |
Improving estimates of ice sheet elevation change derived from AltiKa and CryoSat-2 satellite radar altimetry |
title_short |
Improving estimates of ice sheet elevation change derived from AltiKa and CryoSat-2 satellite radar altimetry |
title_full |
Improving estimates of ice sheet elevation change derived from AltiKa and CryoSat-2 satellite radar altimetry |
title_fullStr |
Improving estimates of ice sheet elevation change derived from AltiKa and CryoSat-2 satellite radar altimetry |
title_full_unstemmed |
Improving estimates of ice sheet elevation change derived from AltiKa and CryoSat-2 satellite radar altimetry |
title_sort |
improving estimates of ice sheet elevation change derived from altika and cryosat-2 satellite radar altimetry |
publishDate |
2021 |
url |
https://etheses.whiterose.ac.uk/29184/ |
long_lat |
ENVELOPE(-101.000,-101.000,-75.000,-75.000) ENVELOPE(-106.750,-106.750,-75.500,-75.500) |
geographic |
Antarctic Greenland Pine Island Glacier Thwaites Glacier West Antarctica |
geographic_facet |
Antarctic Greenland Pine Island Glacier Thwaites Glacier West Antarctica |
genre |
Antarc* Antarctic Antarctica glacier Greenland Ice Sheet Pine Island Pine Island Glacier Thwaites Glacier West Antarctica |
genre_facet |
Antarc* Antarctic Antarctica glacier Greenland Ice Sheet Pine Island Pine Island Glacier Thwaites Glacier West Antarctica |
op_relation |
Otosaka, Inès Natsuki orcid:0000-0001-9740-3735 (2021) Improving estimates of ice sheet elevation change derived from AltiKa and CryoSat-2 satellite radar altimetry. PhD thesis, University of Leeds. |
_version_ |
1766253674708860928 |