A dynamically consistent analysis of circulation and transports in the southwestern Weddell Sea
An inverse model is applied for the analysis of hydrographic and current meter data collected on the repeat WOCE section SR4 in the Weddell Sea in 1989–1992. The section crosses the Weddell Sea cyclonic gyre from Kapp Norvegia to the northern end of the Antarctic Peninsula. The concepts of geost...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
1998-08-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/16/1024/1998/angeo-16-1024-1998.pdf |
| _version_ | 1818517310815600640 |
|---|---|
| author | M. Yaremchuk M. Yaremchuk D. Nechaev D. Nechaev J. Schroter E. Fahrbach |
| author_facet | M. Yaremchuk M. Yaremchuk D. Nechaev D. Nechaev J. Schroter E. Fahrbach |
| author_sort | M. Yaremchuk |
| collection | DOAJ |
| description | An inverse model is applied for the analysis
of hydrographic and current meter data collected on the repeat WOCE section SR4
in the Weddell Sea in 1989–1992. The section crosses the Weddell Sea cyclonic
gyre from Kapp Norvegia to the northern end of the Antarctic Peninsula. The
concepts of geostrophy, conservation of planetary vorticity and hydrostatics are
combined with advective balances of active and passive properties to provide a
dynamically consistent circulation pattern. Our variational assimilation scheme
allows the calculation of three-dimensional velocities in the section plane.
Current speeds are small except along the coasts where they reach up to 12 cm/s.
We diagnose a gyre transport of 34 Sverdrup which is associated with a poleward
heat transport of 28×10<sup>12</sup> W corresponding to an average heat flux of
15 Wm<sup>–2</sup> in the Weddell Sea south of the transect. This exceeds the
estimated local flux on the transect of 2 Wm<sup>–2</sup>. As the transect is
located mostly in the open ocean, we conclude that the shelf areas contribute
significantly to the ocean-atmosphere exchange and are consequently key areas
for the contribution of the Weddell Sea to global ocean ventilation. Conversion
of water masses occuring south of the section transform 6.6±1.1 Sv of the
inflowing warm deep water into approximately equal amounts of Weddell Sea deep
water and Weddell Sea bottom water. The volume transport of surface water equals
in the in- and outflow. This means that almost all newly formed surface water is
involved in the deep and bottom water formation. Comparison with the results
obtained by pure velocity interpolation combined with a hydrographic data subset
indicates major differences in the derived salt transports and the water mass
conversion of the surface water. The differences can be explained by deviations
in the structure of the upper ocean currents to which shelf areas contribute
significantly. Additionally a rigorous variance analysis is performed. When only
hydrographic data are used for the inversion both the gyre transport and the
poleward heat transport are substantially lower. They amount to less than 40% of
our best estimate while the standard deviations of both quantities are 6.5 Sv
and 37×10<sup>12</sup> W, respectively. With the help of long-term current
meter measurements these errors can be reduced to 2 Sv and 8×10<sup>12</sup> W.
Our result underlines the importance of velocity data or equivalent information
that helps to estimate the absolute velocities.<br><br><b>Key words.</b> Oceanography: General (Arctic and antarctic
oceanography) · Oceanography: Physical (General circulation; Hydrography)</p> |
| first_indexed | 2024-12-11T00:54:33Z |
| format | Article |
| id | doaj.art-5d57aafa7ac04236b16087ffb6c8ff04 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-11T00:54:33Z |
| publishDate | 1998-08-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-5d57aafa7ac04236b16087ffb6c8ff042022-12-22T01:26:32ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05761998-08-01161024103810.1007/s00585-998-1024-7A dynamically consistent analysis of circulation and transports in the southwestern Weddell SeaM. Yaremchuk0M. Yaremchuk1D. Nechaev2D. Nechaev3J. Schroter4E. Fahrbach5Shirshov Institute of Oceanography, Krasikova 23, 117218 Moscow, RussiaAlfred-Wegener-Institute for Polar and Marine Research, Am Handelshafen 12, D-27570 Bremerhaven, GermanyShirshov Institute of Oceanography, Krasikova 23, 117218 Moscow, RussiaAlfred-Wegener-Institute for Polar and Marine Research, Am Handelshafen 12, D-27570 Bremerhaven, GermanyAlfred-Wegener-Institute for Polar and Marine Research, Am Handelshafen 12, D-27570 Bremerhaven, GermanyAlfred-Wegener-Institute for Polar and Marine Research, Am Handelshafen 12, D-27570 Bremerhaven, GermanyAn inverse model is applied for the analysis of hydrographic and current meter data collected on the repeat WOCE section SR4 in the Weddell Sea in 1989–1992. The section crosses the Weddell Sea cyclonic gyre from Kapp Norvegia to the northern end of the Antarctic Peninsula. The concepts of geostrophy, conservation of planetary vorticity and hydrostatics are combined with advective balances of active and passive properties to provide a dynamically consistent circulation pattern. Our variational assimilation scheme allows the calculation of three-dimensional velocities in the section plane. Current speeds are small except along the coasts where they reach up to 12 cm/s. We diagnose a gyre transport of 34 Sverdrup which is associated with a poleward heat transport of 28×10<sup>12</sup> W corresponding to an average heat flux of 15 Wm<sup>–2</sup> in the Weddell Sea south of the transect. This exceeds the estimated local flux on the transect of 2 Wm<sup>–2</sup>. As the transect is located mostly in the open ocean, we conclude that the shelf areas contribute significantly to the ocean-atmosphere exchange and are consequently key areas for the contribution of the Weddell Sea to global ocean ventilation. Conversion of water masses occuring south of the section transform 6.6±1.1 Sv of the inflowing warm deep water into approximately equal amounts of Weddell Sea deep water and Weddell Sea bottom water. The volume transport of surface water equals in the in- and outflow. This means that almost all newly formed surface water is involved in the deep and bottom water formation. Comparison with the results obtained by pure velocity interpolation combined with a hydrographic data subset indicates major differences in the derived salt transports and the water mass conversion of the surface water. The differences can be explained by deviations in the structure of the upper ocean currents to which shelf areas contribute significantly. Additionally a rigorous variance analysis is performed. When only hydrographic data are used for the inversion both the gyre transport and the poleward heat transport are substantially lower. They amount to less than 40% of our best estimate while the standard deviations of both quantities are 6.5 Sv and 37×10<sup>12</sup> W, respectively. With the help of long-term current meter measurements these errors can be reduced to 2 Sv and 8×10<sup>12</sup> W. Our result underlines the importance of velocity data or equivalent information that helps to estimate the absolute velocities.<br><br><b>Key words.</b> Oceanography: General (Arctic and antarctic oceanography) · Oceanography: Physical (General circulation; Hydrography)</p>https://www.ann-geophys.net/16/1024/1998/angeo-16-1024-1998.pdf |
| spellingShingle | M. Yaremchuk M. Yaremchuk D. Nechaev D. Nechaev J. Schroter E. Fahrbach A dynamically consistent analysis of circulation and transports in the southwestern Weddell Sea Annales Geophysicae |
| title | A dynamically consistent analysis of circulation and transports in the southwestern Weddell Sea |
| title_full | A dynamically consistent analysis of circulation and transports in the southwestern Weddell Sea |
| title_fullStr | A dynamically consistent analysis of circulation and transports in the southwestern Weddell Sea |
| title_full_unstemmed | A dynamically consistent analysis of circulation and transports in the southwestern Weddell Sea |
| title_short | A dynamically consistent analysis of circulation and transports in the southwestern Weddell Sea |
| title_sort | dynamically consistent analysis of circulation and transports in the southwestern weddell sea |
| url | https://www.ann-geophys.net/16/1024/1998/angeo-16-1024-1998.pdf |
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