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Arctic sea surface height variability and change from satellite radar altimetry and GRACE, 2003-2014

Arctic sea surface height variability and change from satellite radar altimetry and GRACE, 2003-2014
Arctic sea surface height variability and change from satellite radar altimetry and GRACE, 2003-2014
Arctic sea surface height (SSH) is poorly observed by radar altimeters due to the poor coverage of the polar oceans provided by conventional altimeter missions and because large areas are perpetually covered by sea ice, requiring specialized data processing. We utilize SSH estimates from both the ice-covered and ice-free ocean to present monthly estimates of Arctic Dynamic Ocean Topography (DOT) from radar altimetry south of 81.5°N and combine this with GRACE ocean mass to estimate steric height. Our SSH and steric height estimates show good agreement with tide gauge records and geopotential height derived from Ice-Tethered Profilers. The large seasonal cycle of Arctic SSH (amplitude ?5 cm) is dominated by seasonal steric height variation associated with seasonal freshwater fluxes, and peaks in October–November. Overall, the annual mean steric height increased by 2.2?±?1.4 cm between 2003 and 2012 before falling to circa 2003 levels between 2012 and 2014 due to large reductions on the Siberian shelf seas. The total secular change in SSH between 2003 and 2014 is then dominated by a 2.1?±?0.7 cm increase in ocean mass. We estimate that by 2010, the Beaufort Gyre had accumulated 4600 km3 of freshwater relative to the 2003–2006 mean. Doming of Arctic DOT in the Beaufort Sea is revealed by Empirical Orthogonal Function analysis to be concurrent with regional reductions in the Siberian Arctic. We estimate that the Siberian shelf seas lost ?180 km3 of freshwater between 2003 and 2014, associated with an increase in annual mean salinity of 0.15 psu yr?1. Finally, ocean storage flux estimates from altimetry agree well with high-resolution model results, demonstrating the potential for altimetry to elucidate the Arctic hydrological cycle.
Arctic Ocean, sea surface height, freshwater, radar altimetry, variability, CryoSat-2
4303-4322
Armitage, Thomas W.K.
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Bacon, Sheldon
1e7aa6e3-4fb4-4230-8ba7-90837304a9a7
Ridout, Andy L.
5ee88710-4e33-42f6-9a24-4c7987e65869
Thomas, Sam F.
0c873bbc-b3af-4cfa-9c03-52c348292d54
Aksenov, Yevgeny
1d277047-06f6-4893-8bcf-c2817a9c848e
Wingham, Duncan J.
d9737804-ee0f-4350-8dd8-c6414dbb096b
Armitage, Thomas W.K.
01077d1d-f425-403d-a240-922ad32202b9
Bacon, Sheldon
1e7aa6e3-4fb4-4230-8ba7-90837304a9a7
Ridout, Andy L.
5ee88710-4e33-42f6-9a24-4c7987e65869
Thomas, Sam F.
0c873bbc-b3af-4cfa-9c03-52c348292d54
Aksenov, Yevgeny
1d277047-06f6-4893-8bcf-c2817a9c848e
Wingham, Duncan J.
d9737804-ee0f-4350-8dd8-c6414dbb096b

Armitage, Thomas W.K., Bacon, Sheldon, Ridout, Andy L., Thomas, Sam F., Aksenov, Yevgeny and Wingham, Duncan J. (2016) Arctic sea surface height variability and change from satellite radar altimetry and GRACE, 2003-2014. Journal of Geophysical Research: Oceans, 121 (6), 4303-4322. (doi:10.1002/2015JC011579).

Record type: Article

Abstract

Arctic sea surface height (SSH) is poorly observed by radar altimeters due to the poor coverage of the polar oceans provided by conventional altimeter missions and because large areas are perpetually covered by sea ice, requiring specialized data processing. We utilize SSH estimates from both the ice-covered and ice-free ocean to present monthly estimates of Arctic Dynamic Ocean Topography (DOT) from radar altimetry south of 81.5°N and combine this with GRACE ocean mass to estimate steric height. Our SSH and steric height estimates show good agreement with tide gauge records and geopotential height derived from Ice-Tethered Profilers. The large seasonal cycle of Arctic SSH (amplitude ?5 cm) is dominated by seasonal steric height variation associated with seasonal freshwater fluxes, and peaks in October–November. Overall, the annual mean steric height increased by 2.2?±?1.4 cm between 2003 and 2012 before falling to circa 2003 levels between 2012 and 2014 due to large reductions on the Siberian shelf seas. The total secular change in SSH between 2003 and 2014 is then dominated by a 2.1?±?0.7 cm increase in ocean mass. We estimate that by 2010, the Beaufort Gyre had accumulated 4600 km3 of freshwater relative to the 2003–2006 mean. Doming of Arctic DOT in the Beaufort Sea is revealed by Empirical Orthogonal Function analysis to be concurrent with regional reductions in the Siberian Arctic. We estimate that the Siberian shelf seas lost ?180 km3 of freshwater between 2003 and 2014, associated with an increase in annual mean salinity of 0.15 psu yr?1. Finally, ocean storage flux estimates from altimetry agree well with high-resolution model results, demonstrating the potential for altimetry to elucidate the Arctic hydrological cycle.

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Accepted/In Press date: 24 May 2016
e-pub ahead of print date: 24 June 2016
Published date: June 2016
Keywords: Arctic Ocean, sea surface height, freshwater, radar altimetry, variability, CryoSat-2
Organisations: Marine Systems Modelling, Marine Physics and Ocean Climate

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Local EPrints ID: 401159
URI: https://eprints.soton.ac.uk/id/eprint/401159
PURE UUID: 07783393-ddfa-483f-9b08-0c46c61c5596

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Date deposited: 05 Oct 2016 10:56
Last modified: 09 Jan 2018 17:49

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Contributors

Author: Thomas W.K. Armitage
Author: Sheldon Bacon
Author: Andy L. Ridout
Author: Sam F. Thomas
Author: Yevgeny Aksenov
Author: Duncan J. Wingham

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