doi:10.1016/j.dsr2.2007.01.014
Published by Elsevier Ltd.
Circulation and heat fluxes during the austral fall in George VI Sound, Antarctic Peninsula
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Ryan D. Dorlanda and Meng Zhou
, a, 
aDepartment of Environmental, Earth and Ocean Sciences, University of Massachusetts, Boston, 100 Morrissey Boulevard, Boston, MA 02125, USA
Accepted 1 November 2007.
Available online 23 December 2007.
Abstract
A mesoscale survey was conducted in northern George VI Sound as part of the United States Southern Ocean Global Ocean Ecosystems Dynamics program in austral fall 2001 to examine the circulation and heat fluxes. The absolute dynamic height field is determined from a combination of measured currents detided using model-predicted tidal currents, streamfunction fitting, and the thermal wind equation based on hydrographic measurements. The results have revealed surface coastal currents of 0.2 m s−1 intruding into northern George VI Sound from Marguerite Bay (MB) and mesoscale eddies formed within the deep trough. Both Antarctic surface waters and modified circumpolar deep water were transported into the sound along the eastern side of the sound while ice shelf influenced waters exited to MB along the western side. Analysis indicates that predominant southward winds during the season were responsible for driving the basin-wide circulation in the sound. Both convergence of horizontal heat transports and vertical upwelling heat fluxes were significant to the contribution or delay of local ice formation in George VI Sound, which is critical for the austral winter ecosystem.
Keywords: Southern Ocean; Mesoscale; Jets; Eddies; Upwelling; Heat fluxes
Fig. 1. (A) Map of the Antarctic Peninsula (AP) and Marguerite Bay (MB). Contours represent the 500 and 2500 m isobaths. Interrupted lines indicate ice shelf edges. Abbreviations: (SB) continental shelf break, (MT) Marguerite Trough, (WS) location of collapsed Wordie Ice Shelf, (CJ) Cape Jeremy, (AI) Alexander Island, and the (RE) Ronne Entrance. The circle and C9 indicate the location of a CTD profile included in Fig. 2, and the solid black box indicates the survey area. (B) The enlarged survey area including NGVI, cruise tracks and CTD station locations. Colors represent the isobaths. Black thin lines represent the ship tracks, black dots indicate CTD stations occupied between May 14 and 16, 2001, and blue thick lines labeled A–D indicate four transects shown in Fig. 6, Fig. 7, Fig. 8 and Fig. 9.
Fig. 2. Potential temperature and salinity for CTD casts in NGVI and an off-shore CTD cast at Station C9 indicated in Fig. 1 (gray line). Background dotted lines are constant contours of σθ. The horizontal dashed line represents the freezing temperature at the surface.
Fig. 3. (A) The 15-min ensemble ADCP current measurements at 102 m. (B) Tidal currents along the ship tracks. (C) Detided ADCP currents at 102 m.
Fig. 4. (A) Streamfunction contours in m2 s−1 determined from the least-squares fit to the detided current measurements at 102 m. (B) Sea-surface anomalies in cm.
Fig. 5. Potential temperature anomalies (A, D, G), salinity anomalies (B, E, H), and σθ anomalies (C, F, I) with absolute geostrophic currents at 34, 102, and 300 m. Values located in the lower left corners of individual panels are the spatial means at each depth.
Fig. 6. Transect line A. (A) Potential temperature (°C), (B) salinity, (C) σθ , and (D) velocity perpendicular to the transect line. Positive values indicate eastward flow. Distances are in km measured from the south to the north. Black solid contours in A represent the horizontal heat flux in W m−2.
Fig. 7. Transect line B. (A) Potential temperature (°C), (B) salinity, (C) σθ, and (D) velocity perpendicular to the transect line. Positive values indicate northward flow out of the sound. Distances are in km measured from the west of the transect line to the east.
Fig. 8. Transect line C. (A) Potential temperature (°C), (B) salinity, (C) σθ, and (D) velocity perpendicular to the transect line. Positive values indicate northward flow out of the sound. Distances are in km measured from the west of the transect line to the east.
Fig. 9. Transect line D. (A) Potential temperature (°C), (B) salinity, (C) σθ, and (D) velocity perpendicular to the transect line. Positive values indicate northward flow out of the sound. Distances are in km measured from the west of the transect line to the east.
Fig. 10. (A–B) Depth mean current and depth mean magnitude of current deviation in the longitudinal direction. (C–D) Depth mean current and depth mean magnitude of current deviation in the latitudinal direction The units for currents and deviations are in m s−1.
Fig. 11. In situ wind field in 15′×15′ bins during the survey period.
Fig. 12. Vertical velocity in m day−1 at 102 m. Positive values represent areas of upwelling and negative values areas of downwelling.
Fig. 13. (A) Upwelling heat fluxed in W m−2 at 102 m. Solid contours represent positive (upwards) fluxes and dashed contours represent negative (downward) fluxes. (B) Convergence of horizontal heat transports between 102 m and the surface in W m−2.
Corresponding author. Tel.: +1 617 287 7419; fax: +1 617 287 7474.
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