A method for constructing directional surface wave spectra from ICESat-2 altimetry
Sea ice is important for Earth's energy budget as it influences surface albedo and air–sea fluxes in polar regions. On its margins, waves heavily impact sea ice. Routine and repeat observations of waves in sea ice are currently lacking, and therefore a comprehensive understanding of how waves i...
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ftcopernicus:oai:publications.copernicus.org:tc106059 2024-02-11T10:08:29+01:00 A method for constructing directional surface wave spectra from ICESat-2 altimetry Hell, Momme C. Horvat, Christopher 2024-01-19 application/pdf https://doi.org/10.5194/tc-18-341-2024 https://tc.copernicus.org/articles/18/341/2024/ eng eng doi:10.5194/tc-18-341-2024 https://tc.copernicus.org/articles/18/341/2024/ eISSN: 1994-0424 Text 2024 ftcopernicus https://doi.org/10.5194/tc-18-341-2024 2024-01-22T17:24:14Z Sea ice is important for Earth's energy budget as it influences surface albedo and air–sea fluxes in polar regions. On its margins, waves heavily impact sea ice. Routine and repeat observations of waves in sea ice are currently lacking, and therefore a comprehensive understanding of how waves interact with sea ice and are attenuated by it is elusive. In this paper, we develop methods to separate the two-dimensional (2D) surface wave spectra from sea-ice height observations made by the ICESat-2 (IS2) laser altimeter, a polar-orbiting satellite. A combination of a linear inverse method, called generalized Fourier transform (GFT), to estimate the wave spectra along each beam and a Metropolis–Hastings (MH) algorithm to estimate the dominant wave's incident angle was developed. It allows us to estimate the 2D wave signal and its uncertainty from the high-density, unstructured ATL03 ICESat-2 photon retrievals. The GFT is applied to re-binned photon retrievals on 25 km segments for all six beams and outperforms a discrete Fourier transform (DFT) in accuracy while having fewer constraints on the data structure. The MH algorithm infers wave direction from beam pairs every 25 km using coherent crests of the most energetic waves. Assuming a dominant incident angle, both methods together allow a decomposition into 2D surface wave spectra with the advantage that the residual surface heights can potentially be attributed to other sea-ice properties. The combined GFT–MH method shows promise in routinely isolating waves propagating through sea ice in ICESat-2 data. We demonstrate its ability on a set of example ICESat-2 tracks, suggesting a detailed comparison against in situ data is necessary to understand the quality of retrieved spectra. Text Sea ice Copernicus Publications: E-Journals Hastings ENVELOPE(-154.167,-154.167,-85.567,-85.567) The Cryosphere 18 1 341 361 |
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Open Polar |
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Copernicus Publications: E-Journals |
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ftcopernicus |
language |
English |
description |
Sea ice is important for Earth's energy budget as it influences surface albedo and air–sea fluxes in polar regions. On its margins, waves heavily impact sea ice. Routine and repeat observations of waves in sea ice are currently lacking, and therefore a comprehensive understanding of how waves interact with sea ice and are attenuated by it is elusive. In this paper, we develop methods to separate the two-dimensional (2D) surface wave spectra from sea-ice height observations made by the ICESat-2 (IS2) laser altimeter, a polar-orbiting satellite. A combination of a linear inverse method, called generalized Fourier transform (GFT), to estimate the wave spectra along each beam and a Metropolis–Hastings (MH) algorithm to estimate the dominant wave's incident angle was developed. It allows us to estimate the 2D wave signal and its uncertainty from the high-density, unstructured ATL03 ICESat-2 photon retrievals. The GFT is applied to re-binned photon retrievals on 25 km segments for all six beams and outperforms a discrete Fourier transform (DFT) in accuracy while having fewer constraints on the data structure. The MH algorithm infers wave direction from beam pairs every 25 km using coherent crests of the most energetic waves. Assuming a dominant incident angle, both methods together allow a decomposition into 2D surface wave spectra with the advantage that the residual surface heights can potentially be attributed to other sea-ice properties. The combined GFT–MH method shows promise in routinely isolating waves propagating through sea ice in ICESat-2 data. We demonstrate its ability on a set of example ICESat-2 tracks, suggesting a detailed comparison against in situ data is necessary to understand the quality of retrieved spectra. |
format |
Text |
author |
Hell, Momme C. Horvat, Christopher |
spellingShingle |
Hell, Momme C. Horvat, Christopher A method for constructing directional surface wave spectra from ICESat-2 altimetry |
author_facet |
Hell, Momme C. Horvat, Christopher |
author_sort |
Hell, Momme C. |
title |
A method for constructing directional surface wave spectra from ICESat-2 altimetry |
title_short |
A method for constructing directional surface wave spectra from ICESat-2 altimetry |
title_full |
A method for constructing directional surface wave spectra from ICESat-2 altimetry |
title_fullStr |
A method for constructing directional surface wave spectra from ICESat-2 altimetry |
title_full_unstemmed |
A method for constructing directional surface wave spectra from ICESat-2 altimetry |
title_sort |
method for constructing directional surface wave spectra from icesat-2 altimetry |
publishDate |
2024 |
url |
https://doi.org/10.5194/tc-18-341-2024 https://tc.copernicus.org/articles/18/341/2024/ |
long_lat |
ENVELOPE(-154.167,-154.167,-85.567,-85.567) |
geographic |
Hastings |
geographic_facet |
Hastings |
genre |
Sea ice |
genre_facet |
Sea ice |
op_source |
eISSN: 1994-0424 |
op_relation |
doi:10.5194/tc-18-341-2024 https://tc.copernicus.org/articles/18/341/2024/ |
op_doi |
https://doi.org/10.5194/tc-18-341-2024 |
container_title |
The Cryosphere |
container_volume |
18 |
container_issue |
1 |
container_start_page |
341 |
op_container_end_page |
361 |
_version_ |
1790607837548773376 |