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Arctic Ocean surface geostrophic circulation 2003-2014

Arctic Ocean surface geostrophic circulation 2003-2014
Arctic Ocean surface geostrophic circulation 2003-2014
Abstract. Monitoring the surface circulation of the ice-covered Arctic Ocean is generally limited in space, time or both. We present a new 12-year record of geostrophic currents at monthly resolution in the ice-covered and ice-free Arctic Ocean derived from satellite radar altimetry and characterise their seasonal to decadal variability from 2003 to 2014, a period of rapid environmental change in the Arctic. Geostrophic currents around the Arctic basin increased in the late 2000s, with the largest increases observed in summer. Currents in the southeastern Beaufort Gyre accelerated in late 2007 with higher current speeds sustained until 2011, after which they decreased to speeds representative of the period 2003–2006. The strength of the northwestward current in the southwest Beaufort Gyre more than doubled between 2003 and 2014. This pattern of changing currents is linked to shifting of the gyre circulation to the northwest during the time period. The Beaufort Gyre circulation and Fram Strait current are strongest in winter, modulated by the seasonal strength of the atmospheric circulation. We find high eddy kinetic energy (EKE) congruent with features of the seafloor bathymetry that are greater in winter than summer, and estimates of EKE and eddy diffusivity in the Beaufort Sea are consistent with those predicted from theoretical considerations. The variability of Arctic Ocean geostrophic circulation highlights the interplay between seasonally variable atmospheric forcing and ice conditions, on a backdrop of long-term changes to the Arctic sea ice–ocean system. Studies point to various mechanisms influencing the observed increase in Arctic Ocean surface stress, and hence geostrophic currents, in the 2000s – e.g. decreased ice concentration/thickness, changing atmospheric forcing, changing ice pack morphology; however, more work is needed to refine the representation of atmosphere–ice–ocean coupling in models before we can fully attribute causality to these increases.
1767-1780
Armitage, Thomas W. K.
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Bacon, Sheldon
1e7aa6e3-4fb4-4230-8ba7-90837304a9a7
Ridout, Andy L.
5ee88710-4e33-42f6-9a24-4c7987e65869
Petty, Alek A.
909b9a79-230c-47fd-a656-c24e15a55992
Wolbach, Steven
0d772eb0-9fca-4e31-a637-a7fea6dc977b
Tsamados, Michel
c206a0fe-e2c2-4853-9d71-4d3d9c882af5
Armitage, Thomas W. K., Bacon, Sheldon, Ridout, Andy L., Petty, Alek A., Wolbach, Steven and Tsamados, Michel (2017) Arctic Ocean surface geostrophic circulation 2003-2014 The Cryosphere, 11, (4), pp. 1767-1780. (doi:10.5194/tc-11-1767-2017).

Armitage, Thomas W. K., Bacon, Sheldon, Ridout, Andy L., Petty, Alek A., Wolbach, Steven and Tsamados, Michel (2017) Arctic Ocean surface geostrophic circulation 2003-2014 The Cryosphere, 11, (4), pp. 1767-1780. (doi:10.5194/tc-11-1767-2017).

Record type: Article

Abstract

Abstract. Monitoring the surface circulation of the ice-covered Arctic Ocean is generally limited in space, time or both. We present a new 12-year record of geostrophic currents at monthly resolution in the ice-covered and ice-free Arctic Ocean derived from satellite radar altimetry and characterise their seasonal to decadal variability from 2003 to 2014, a period of rapid environmental change in the Arctic. Geostrophic currents around the Arctic basin increased in the late 2000s, with the largest increases observed in summer. Currents in the southeastern Beaufort Gyre accelerated in late 2007 with higher current speeds sustained until 2011, after which they decreased to speeds representative of the period 2003–2006. The strength of the northwestward current in the southwest Beaufort Gyre more than doubled between 2003 and 2014. This pattern of changing currents is linked to shifting of the gyre circulation to the northwest during the time period. The Beaufort Gyre circulation and Fram Strait current are strongest in winter, modulated by the seasonal strength of the atmospheric circulation. We find high eddy kinetic energy (EKE) congruent with features of the seafloor bathymetry that are greater in winter than summer, and estimates of EKE and eddy diffusivity in the Beaufort Sea are consistent with those predicted from theoretical considerations. The variability of Arctic Ocean geostrophic circulation highlights the interplay between seasonally variable atmospheric forcing and ice conditions, on a backdrop of long-term changes to the Arctic sea ice–ocean system. Studies point to various mechanisms influencing the observed increase in Arctic Ocean surface stress, and hence geostrophic currents, in the 2000s – e.g. decreased ice concentration/thickness, changing atmospheric forcing, changing ice pack morphology; however, more work is needed to refine the representation of atmosphere–ice–ocean coupling in models before we can fully attribute causality to these increases.

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Accepted/In Press date: 26 June 2017
e-pub ahead of print date: 26 July 2017

Identifiers

Local EPrints ID: 413250
URI: http://eprints.soton.ac.uk/id/eprint/413250
PURE UUID: 9c38033d-4ccf-4051-b3ba-ed3d6a3c467b

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Date deposited: 18 Aug 2017 16:31
Last modified: 01 Nov 2017 17:31

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Contributors

Author: Thomas W. K. Armitage
Author: Sheldon Bacon
Author: Andy L. Ridout
Author: Alek A. Petty
Author: Steven Wolbach
Author: Michel Tsamados

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