Physical oceanography from 120 CTDs, 79 water bottles stations, and 30 helicopter-borne CTDs during POLARSTERN cruise ANT-XXII/2 (ISPOL)


The Ice Station POLarstern (ISPOL) cruise revisited the western Weddell Sea in late 2004 and obtained a comprehensive set of conductivity-temperature-depth (CTD) data. This study describes the thermohaline structure and diapycnal mixing environment observed in 2004 and compares them with conditions observed more than a decade earlier. Hydrographic conditions on the central western Weddell Sea continental slope, off Larsen C Ice Shelf, in late winter/early spring of 2004/2005 can be described as a well-stratified environment with upper layers evidencing relict structures from intense winter near-surface vertical fluxes, an intermediate depth temperature maximum, and a cold near-bottom layer marked by patchy property distributions. A well-developed surface mixed layer, isolated from the underlying Warm Deep Water (WDW) by a pronounced pycnocline and characterized by lack of warming and by minimal sea-ice basal melting, supports the assumption that upper ocean winter conditions persisted during most of the ISPOL experiment. Much of the western Weddell Sea water column has remained essentially unchanged since 1992; however, significant differences were observed in two of the regional water masses. The first, Modified Weddell Deep Water (MWDW), comprises the permanent pycnocline and was less saline than a decade earlier, whereas Weddell Sea Bottom Water (WSBW) was horizontally patchier and colder. Near-bottom temperatures observed in 2004 were the coldest on record for the western Weddell Sea over the continental slope. Minimum temperatures were ~0.4 and ~0.3 °C colder than during 1992-1993, respectively. The 2004 near-bottom temperature/salinity characteristics revealed the presence of two different WSBW types, whereby a warm, fresh layer overlays a colder, saltier layer (both formed in the western Weddell Sea). The deeper layer may have formed locally as high salinity shelf water (HSSW) that flowed intermittently down the continental slope, which is consistent with the observed horizontal patchiness. The latter can be associated with the near-bottom variability found in Powell Basin with consequences for the deep water outflow from the Weddell Sea.

Supplement to: Absy, Joao Marcelo; Schröder, Michael; Muench, Robin D; Hellmer, Hartmut H (2008): Early summer thermohaline characteristics and mixing in the western Weddell Sea. Deep Sea Research Part II: Topical Studies in Oceanography, 55(8-9), 1117-1131

Related Identifier
Metadata Access
Creator Absy, Joao Marcelo; Schröder, Michael; Muench, Robin D; Hellmer, Hartmut H (ORCID: 0000-0002-9357-9853)
Publisher PANGAEA
Publication Year 2008
Rights Creative Commons Attribution 3.0 Unported;
OpenAccess true
Language English
Resource Type Supplementary Publication Series of Datasets; Collection
Format application/zip
Size 3 datasets
Discipline Earth System Research
Spatial Coverage (-57.471W, -68.269S, -36.302E, -59.871N); Weddell Sea; Scotia Sea, southwest Atlantic
Temporal Coverage Begin 2004-11-20T00:10:00Z
Temporal Coverage End 2005-01-07T11:40:00Z