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The Irminger Gyre: Circulation, convection, and interannual variability

The Irminger Gyre: Circulation, convection, and interannual variability
The Irminger Gyre: Circulation, convection, and interannual variability
In this study 36 hydrographic transects occupied between 1991 and 2007 in the vicinity of the WOCE A1E/AR7E section are used to investigate various aspects of the Irminger Gyre, a narrow cyclonic recirculation in the southwest Irminger Sea. Vertical sections of absolute geostrophic velocity were constructed using satellite and shipboard velocity measurements, and analyzed in conjunction with the hydrographic data and meteorological fields. The Irminger Gyre is a weakly baroclinic feature with a mean transport of 6.8±1.9 Sv (View the MathML source). At mid-depth it contains water with the same properties as Labrador Sea Water (LSW). During the 17-year study period large changes occurred in the gyre and also within the boundary flow encircling the Irminger Sea. The gyre intensified and became more stratified, while the upper-layer circulation of the boundary current system weakened. The latter is consistent with the overall decline of the North Atlantic subpolar gyre reported earlier. However, the decline of the upper-ocean boundary currents was accompanied by an intensification of the circulation at deeper levels. The deep component of both the northward-flowing boundary current (the Irminger Current) and the southward-flowing boundary current (the Deep Western Boundary Current) strengthened. The increase in transport of the deep Irminger Current is due to the emergence of a second deep limb of the current, presumably due to a shift in pathways of the branches of the subpolar gyre. Using a volumetric water mass analysis it is argued that LSW was formed locally within the Irminger Gyre via deep convection in the early 1990s. In contrast, LSW appeared outside of the gyre in the eastern part of the Irminger Sea with a time lag of 2–3 years, consistent with transit from the Labrador Sea. Thus, our analysis clarifies the relative contributions of locally-versus remotely-formed LSW in the Irminger Sea.
Irminger Sea, Labrador Sea Water, Deep Western Boundary Current, Irminger Current, North Atlantic, Deep convection
0967-0637
590-614
Våge, Kjetil
212fd63d-261e-4d95-aae5-d8745b3c3517
Pickart, Robert S.
b6de3ebc-eed2-478d-a367-69798bf3f504
Sarafanov, Artem
a2036f5b-f2f9-4ba3-9cb3-84973df34aa3
Knutsen, Øyvind
e1823d03-abcb-4d24-8c44-42a0b73f3fc5
Mercier, Herlé
7239215f-8123-4d0e-a7ed-29949a209400
Lherminier, Pascale
b238fb9a-f320-4594-ab4d-493d773c301d
van Aken, Hendrik M.
cbf4d87c-0b39-4fae-a66f-8ab9702f7442
Meincke, Jens
d0fa10fc-df83-47e4-bb35-5e95d271bcbe
Quadfasel, Detlef
6a4c24d8-5ad4-4f49-a48e-b573659a1e29
Bacon, Sheldon
1e7aa6e3-4fb4-4230-8ba7-90837304a9a7
Våge, Kjetil
212fd63d-261e-4d95-aae5-d8745b3c3517
Pickart, Robert S.
b6de3ebc-eed2-478d-a367-69798bf3f504
Sarafanov, Artem
a2036f5b-f2f9-4ba3-9cb3-84973df34aa3
Knutsen, Øyvind
e1823d03-abcb-4d24-8c44-42a0b73f3fc5
Mercier, Herlé
7239215f-8123-4d0e-a7ed-29949a209400
Lherminier, Pascale
b238fb9a-f320-4594-ab4d-493d773c301d
van Aken, Hendrik M.
cbf4d87c-0b39-4fae-a66f-8ab9702f7442
Meincke, Jens
d0fa10fc-df83-47e4-bb35-5e95d271bcbe
Quadfasel, Detlef
6a4c24d8-5ad4-4f49-a48e-b573659a1e29
Bacon, Sheldon
1e7aa6e3-4fb4-4230-8ba7-90837304a9a7

Våge, Kjetil, Pickart, Robert S., Sarafanov, Artem, Knutsen, Øyvind, Mercier, Herlé, Lherminier, Pascale, van Aken, Hendrik M., Meincke, Jens, Quadfasel, Detlef and Bacon, Sheldon (2011) The Irminger Gyre: Circulation, convection, and interannual variability. Deep Sea Research Part I: Oceanographic Research Papers, 58 (5), 590-614. (doi:10.1016/j.dsr.2011.03.001).

Record type: Article

Abstract

In this study 36 hydrographic transects occupied between 1991 and 2007 in the vicinity of the WOCE A1E/AR7E section are used to investigate various aspects of the Irminger Gyre, a narrow cyclonic recirculation in the southwest Irminger Sea. Vertical sections of absolute geostrophic velocity were constructed using satellite and shipboard velocity measurements, and analyzed in conjunction with the hydrographic data and meteorological fields. The Irminger Gyre is a weakly baroclinic feature with a mean transport of 6.8±1.9 Sv (View the MathML source). At mid-depth it contains water with the same properties as Labrador Sea Water (LSW). During the 17-year study period large changes occurred in the gyre and also within the boundary flow encircling the Irminger Sea. The gyre intensified and became more stratified, while the upper-layer circulation of the boundary current system weakened. The latter is consistent with the overall decline of the North Atlantic subpolar gyre reported earlier. However, the decline of the upper-ocean boundary currents was accompanied by an intensification of the circulation at deeper levels. The deep component of both the northward-flowing boundary current (the Irminger Current) and the southward-flowing boundary current (the Deep Western Boundary Current) strengthened. The increase in transport of the deep Irminger Current is due to the emergence of a second deep limb of the current, presumably due to a shift in pathways of the branches of the subpolar gyre. Using a volumetric water mass analysis it is argued that LSW was formed locally within the Irminger Gyre via deep convection in the early 1990s. In contrast, LSW appeared outside of the gyre in the eastern part of the Irminger Sea with a time lag of 2–3 years, consistent with transit from the Labrador Sea. Thus, our analysis clarifies the relative contributions of locally-versus remotely-formed LSW in the Irminger Sea.

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More information

Published date: May 2011
Keywords: Irminger Sea, Labrador Sea Water, Deep Western Boundary Current, Irminger Current, North Atlantic, Deep convection
Organisations: Marine Physics and Ocean Climate

Identifiers

Local EPrints ID: 187393
URI: http://eprints.soton.ac.uk/id/eprint/187393
ISSN: 0967-0637
PURE UUID: 0d84046a-37f8-4489-8d76-4a689072e672

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Date deposited: 16 May 2011 16:11
Last modified: 14 Mar 2024 03:25

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Contributors

Author: Kjetil Våge
Author: Robert S. Pickart
Author: Artem Sarafanov
Author: Øyvind Knutsen
Author: Herlé Mercier
Author: Pascale Lherminier
Author: Hendrik M. van Aken
Author: Jens Meincke
Author: Detlef Quadfasel
Author: Sheldon Bacon

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