Circulation of the Weddell Gyre Inferred from Long-term Observations

• Main Authors: Reeve, Krissy, Kanzow, Torsten, Rohardt, Gerd, Boebel, Olaf, Strass, Volker, Gerdes, Rüdiger
• Format: Conference Object
• Language: unknown
• Published: 2018
• Subjects: Antarc*; Antarctic; Antarctic Peninsula; Ice Shelf; Ice Shelves; Sea ice; Weddell Sea
• Online Access: https://epic.awi.de/id/eprint/49524/; https://www.polar2018.org/uploads/2/4/6/0/24605948/polar2018_abstractproceedings.pdf; https://hdl.handle.net/10013/epic.aa78b47b-5292-49cb-ac6a-ad50b9aa74e5

The Weddell Gyre plays a fundamental role in the climate system by advecting heat poleward to the Antarctic ice shelves and by regulating the density of water masses that feed the lowest limb of the global overturning circulation. Profile and trajectory data between 2002 and 2016 from a fleet of Argo floats between 50 and 2000 m are exploited in order to produce a full gyre scale view of the Weddell Gyre's circulation. The data exhibit a gradual cooling of the Warm Deep Water (WDW) as it circulates cyclonically around the gyre. A double-cell structure of the Weddell Gyre is revealed, with a stronger eastern core that intensifies with depth, and a weaker western core that remains invariant with depth. The deep outflow of Weddell Sea Deep and Bottom Water (WSDW, WSBW) at the western boundary of the gyre, formed from WDW by complex modification processes involving sea ice formation, and basal ice shelf melting, is not covered by the float observations. Using mooring array-based observations near the tip of the Antarctic Peninsula between 1989 and 1998, and between 2005 and 2014, a cooling of the WSBW plume is revealed over the observational period. This is in striking contrast to the WSDW in the interior Weddell Sea which has been undergoing a decadal warming. While the cause of the cooling of the WSBW plume is currently unclear, the mooring-based velocity observations indicate that the volume transport of the WSBW plume of 2.5 Sv has been stable over time.