Home · Committee · Themes · Links · Documents · Progress
Precipitation Simulation for Dronning Maud Land
Ulrike Wacker
Alfred Wegener Institut für Polar- u. Meeresforschung, Postfach 12 01 61, 27515 Bremerhaven
The high resolution operational weather forecast model 'Lokal-Modell' (LM) of the German Weather Service has been implemented for Antarctica to investigate origin and amount of precipitation in DML for selected weather events. Case studies show that the horizontal precipitation variability certainly reflects the synoptic and topographic forcing, On the plateau, where these forcings become weak, we do not find, however, a monotonous inland decrease in precipitation.
Polarstern cruise ANT-XXIII/2, 20. 11. 2005 - 12. 01. 2006
Volker Strass
Alfred Wegener Institut für Polar- u. Meeresforschung, Postfach 12 01 61, 27515 Bremerhaven
A major part of the marine research was dedicated to the Lazarev Sea Krill Study, LAKRIS, a German contribution to the international initiatives SO-GLOBEC (Southern Ocean - Global Ocean Ecosystems Dynamics), CCAMLR (Convention on the Conservation of Antarctic Marine Living Resources) and CeDAMar (Census of the Biodiversity of the Abyssal Marine Life). LAKRIS in particular is aimed at identifying relationships between the physical environment and the abundance of zooplankton. Special emphasis is put on the possible role of the Weddell Gyre circulation in closing the life cycle of krill. The data base for this study is collected by shipboard observations to map spatial distributions and by moored instruments to reveal temporal variations. Shipboard measurements have been made at a regular grid of hydrographic stations as well as from the moving ship using the vessel-mounted ADCP (Acoustical Doppler Current Profiler) and the thermosalinograph. The new data set will also allow for an improved assessment of the role of the topographic structure of Maud Rise on the vernal opening of the sea ice cover.
Evaluation Ice Station Polarstern (ISPOL)
Michael Schroeder
Alfred Wegener Institut für Polar- u. Meeresforschung, Postfach 12 01 61, 27515 Bremerhaven
The Ice Station POLarstern drift experiment revealed that low atmospheric and oceanic energy fluxes in combination with complex ice dynamics maintain a perennial sea ice cover in the western Weddell Sea. Despite its compactness, this ice is home for high amounts of algal standing stocks, which play a significant role in the carbon dynamics of the ice covered ocean and provide the food for krill prior to ice decay. This pack also covers an ocean in which deep and bottom water is formed, but with a higher spatial and temporal variability than previously assumed.
Compared to ISW-1, the winter water layer (upper 200 meters) was thicker and fresher, thus increasing the stability of the water column, and the bottom water cooled by 0.5ºC. Therefore, the ISPOL results significantly contribute to our understanding of the role of sea ice in the climate and ecosystems.
Decadal variations in the Weddell Sea
Eberhard Fahrbach
Alfred Wegener Institut für Polar- u. Meeresforschung, Postfach 12 01 61, 27515 Bremerhaven
The oceanographic measurements in the Weddell Sea indicate that the bottom water temperature increased steadily during the last decades. This is in contrast to the Warm Deep Water which enters from the Antarctic Circumpolar Current and after an earlier warming is cooling since 1996. The measurements indicate that climate related fluctuations from the upper layers reach the Antarctic deep sea and can affect the properties of the water which feeds the global thermohaline circulation.
CO2 uptake in the Southern Ocean
Mario Hoppema
Alfred Wegener Institut für Polar- u. Meeresforschung, Postfach 12 01 61, 27515 Bremerhaven
During FS Polarstern cruise ANT-XXII/3 in 2005, CO2 system parameters have been measured on two repeat sections through the Weddell Sea. A start has been made with the prime meridian repeat section Total CO2 (TCO2) data and auxiliary parameters for deriving anthropogenic CO2. The applied method is the extended Multiple Linear Regression (eMLR) method, which appears to need specific adjustments for the Southern Ocean. First results find significant quantities of anthropogenic CO2 in the Weddell Sea Bottom Water.
Southern Ocean observation system
Olaf Boebel
Alfred Wegener Institut für Polar- u. Meeresforschung, Postfach 12 01 61, 27515 Bremerhaven
In the framework of the Southern Ocean Observation System 29 ice compatible floats have been deployed within the southern part of the Antarctic Circumpolar Current (ACC) and the Weddell Gyre. Currently, 22 floats still provide profile data from this region. Some floats are equipped iStore, which allows interim storage and delayed transmission of data. Hence, temperature and salinity profiles are obtained under sea ice. Time series of ocean bottom pressure, sea surface height and heat content are collected by Pressure sensor equipped Inverted Echo Sounders (PIES). Currently, three instruments are moored in the ACC. The data of two PIES recovered in 2005 is used for integrating estimates of geostrophic transport variability and for ground-truth validation of GRACE satellite gravity field measurements.
Tracers in the Southern Ocean
Monika Rhein
Universität Bremen, Institut für Umweltphysik - Abt. Ozeanographie Postfach 330440 D-28334 Bremen
In 2004/2005 we participated in the Ice Station POLarstern (ISPOL, Polarstern cruise ANT-XXII/2) close to the Larsen Ice Shelf in the western Weddell Sea. First estimates from our Helium isotope and neon measurements yield fractions of 10 to 40% ISW in the Weddell Sea Bottom Water, most likely origin from the Larsen Ice Shelf. The highest Helium values (dissolved into the water from melted glacial ice) could be observed slightly above the bottom layer and are generally not related to the temperature minimum directly at the bottom. This indicates also the presence of an underlying bottom water type formed by interaction of High Salinity Shelf Water with the adjacent water or water that was temporarily exposed to the sea surface (i.e. Ice Shelf Water formed close to the ice shelf edge, where it could lose oversaturated gases to the atmosphere).