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Scientific Results

by Webmaster Legos last modified Aug 27, 2020 10:43 AM

 

Highlights

  • Construction of gridded temperature sections and SSS data for each transect, as well as climatological monthly mean data and annual summer mean DJFM data of the surface salinity and upper ocean temperature near 140°E at high-resolution over the seasonal heating cycle (Oct to Mar). Distributed via SEDOO: XBT website https://doi.org/10.6096/11, TSG website: http://sss.sedoo.fr/. Used extensively for ocean model validation.

 

  • Characterisation of the seasonal mixed layer property variations in relation to the surface ocean heat and freshwater budgets.  (link to science result 1).

 

  • Document the long-term temperature changes within different water-masses across our section over 25-years, and how the trend compares to the interannual variability (Auger et al., 2020). (link to science result 2). Three regions stand out as having strong change that is radically different from the interannual variability :

o (A) warming of the deep-reaching subantarctic waters (0.29±0.09 °C/dec) in the northern part of our section;
o (B) cooling of the near-surface subpolar waters close to Antarctica that extends down to 200 m depth (-0.07±0.04°C/dec), in a region of long-term cooling in SST
o (C) significant warming of the subsurface subpolar Circumpolar deep waters (0.04±0.01°C/dec), associated with a large shallowing (39±11 m/dec).

  • Subsurface Winter Water layer temperatures undergo large interannual variations that overwhelm any long-term trend, and lagrangian tracking show they are correlated (r=0.68) with the SST of the previous winter located further upstream in the subpolar Australian-Antarctic basin (120-145°E; 57-61°S). (link to science result 3).

 

  • The underway SSS data reveals the seasonal and interannual variations in the surface salinity, the critical variable for ocean stability in the Southern Ocean . (link to science result 4). In particular :

o Seasonal freshening of the surface Antarctic waters over the summer sea-ice melting cycle
o Interannual SSS variations in the north of the section are linked to input of Subtropical waters from the Tasman Sea, and cold eddies from the SAF
o Biannual SSS variations in the Antarctic Zone are linked to upstream sea-ice coverage and melt in the preceding spring
o Surface salinity and the freshwater budget close to Antarctica vary mainly in relation to seasonal sea-ice cover and melt, and not E-P, and were largely impacted by the Mertz glacier calving in 2011. 

List of 4 science results and others

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