Projects
Several projects conducted in Observational Oceanography aim to improve our understanding of decadal variability in subpolar and polar oceans. The understanding of natural fluctuations is the prerequisite to diagnose anthropogenic change in the Arctic and the Antarctic.
In the Arctic fieldwork is focussed in the Greenland Sea, Fram Strait and the Arctic Ocean. The work is part of the MARCOPOLI work packages MAR1 and POL3 and is supported by the EU in the DAMOCLES project and by national funding of the project North Atlantic. Earlier work in this context occurred in the EU projects VEINS and ASOF-N. During the International Polar Year we are partners in the IPY projects iAOOS and DAMOCLES.
In the Greenland Sea it is intended to observe the status of deep convection over decadal time scales and to understand the related processes as large scale subsidence and small scale eddies.
Fram Strait is the only deep pathway between the Arctic Ocean and the global Ocean. Heat and freshwater transports through this strait affect the watermass properties in the Arctic Ocean and the convection in the Nordic Seas. In the last decade the temperature of the northward flowing water of Atlantic origin increased significantly. The observations of the changes will be continued and the relevant processes must be understood. The observations will be a contribution to Arctic ROOS which is presently established and part of OceanSITES.
Mooring array in Fram Strait which is maintained in cooperation with the Norwegian Polar Institute. Starting in 2007 the measurements will be complemented by the use of gliders, acoustic data transmission and a satellite transmitter mounted on a system profiling to the sea surface. .
Time series in the level of the Atlantic water indicate an increase of temperature in the West Spitsbergen Current (WSC). In the East Greenland Current (EGC) the southward velocity increased.
In the Arctic Ocean the sea ice cover in summer decreased significantly during the last decades. The properties of the inflowing waters are subject to significant variations. The effect of the changes in the inflow on the exchanges of between ocean and sea ice and the freshwater budget must be observed and understood.
Since summer 2007, the circulation of fresh water and of the Atlantic Water in the central Arctic is measured by Ice-Tethered Platforms (ITPs) and Ice-Tethered Acoustic Current Meter (ITAC, development by Optimare).
ITAC velocity at 327m (left) and 55m (right) from 15th Sep. until 4th Nov., 2007. Unit vectors are 10cm/s. Vectors are hourly ITAC surface drift (cyan) and two-hourly ocean velocity (black). Two-day averages of ocean velocity (red) are also shown. Note that the ITAC is mounted on the same ice floe as the ITP#12.
θ0 (ºC) around 330m from three ITPs. Also shown is the section of ITP#12 profiles around 87º to 88.5ºN.
In the Antarctic observations are carried out in the Atlantic sector of the Southern Ocean. They are part of the MARCOPOLI programme in the work packages MAR1 and POL2. In the International Polar Year they contribute to the IPY Projects CASO and SASSI.
In the Weddell Sea the observations in the WECCON project, which are a contribution to Southern Ocean CLIVAR, indicated that the properties of the inflowing Circumpolar or Warm Deep Water and of the newly formed Weddell Sea Bottom Water changed significantly during the last decades. The moorings are a contribution to OceanSITES.
Schematic representation of the circulation of the Warm Deep Water and the Weddell Sea Bottom Water in the Atlantic sector of the Southern Ocean and the locations of the measurements in the WECCON project.
On the Greenwich meridian increased the temperature of the Warm Deep Water until the mid-nineties and decreased since. The temperature of the Weddell Sea Bottom Water is still increasing.
To measure the variations of the watermass properties of the Warm Deep Water with sufficient spatial and temporal resolution to be able to conclude on the origin and the effect of the changes a float system is established in the HAFOS-project, which is providing comparable data as the Argo project in the open ocean.
Variations of the properties of Warm Deep Water could also affect other water masses in the Weddell Sea through the Antarctic Coastal Current (ACoC). To account for the influence that the ACoC could have on the properties of Antarctic Deep and Bottom Water, the project ACoCIBoW researches the sources of the variability of the ACoC and its effects on the formation of water masses in the Weddell Sea. ACoCIBoW is a subproject of work package POL2 of MARCOPOLI, and it is also partially financed by the Deutsche Forschungsgemeinschaft (DFG).
The Hybrid Antarctic Float Observation System (HAFOS) which provides oceanic data under the sea ice cover.
The role of the Weddell Sea in the global CO2 cycle is investigated in the context of the EU project CarboOcean. A main goal is to determine the (changing) inventory of anthropogenic CO2. This will be done in a concerted action with other investigators in the Southern Ocean.
Other projects are dedicated to the study of processes, in particular processes that constitute potentially important feedback mechanisms in the climate system and/or physical controls of biological production. Also within POL2 turbulence in the mixed layer and mesoscale dynamics are being investigated and the iron hypothesis, the hypothesis that the supply of iron to the open ocean influences the atmospheric CO2 concentration, is being tested. For a test of the latter, two iron fertilisation experiments, EisenEx- and EIFEX, were conducted in the centre of the Antarctic Circum Polar Current. In another project, LAKRIS, the influences of the ocean circulation and the seasonally varying sea ice cover on the abundance of zooplankton and krill are studied. For the International Polar Year it is planned to carry out a Synoptic Circum-Antarctic Climate-processes and Ecosystem study (SCACE) in international cooperation under the umbrella of ICED-IPY.