Intense nutrient removal in the remote area off Larsen Ice Shelf (Weddell Sea)

Abstract

Using Weddell Sea data collected during a cruise with “FS Polarstern” in austral summer 1992/1993, depletions of nutrients and TCO2 in the summer surface layer were calculated. The analogous depletion-like properties for temperature (Heat Storage) and salinity were also computed. The latter properties are useful to describe the physical conditions over the time period pertinent to the depletions. For different areas a strong correlation exists of Heat Storage and nutrient/TCO2 depletions, which is caused by a common factor – the period of light availability. Offshore of the Larsen shelf, an area usually inaccessible due to perennial ice cover, high nutrients/TCO2 depletions are achieved over a short period of time, pointing to a rapidly producing biological system. Primary productivity, calculated from the TCO2 depletion, amounts to about 100 mg C m−2 day−1 for the central Weddell Sea, but 570–1140 mg C m−2 day−1 for the offshore Larsen region. These values agree fairly well with the open-ocean Antarctic and other coastal areas, respectively.