Go North at Midnight

The “Polarstern” leaves for winterexperiments in the Arctic

On 28th february at 12 p.m. “Polarstern”, the research vessel of the Alfred-Wegener-Institute (AWI), will set sail again. The 19th Arctic expedition has an unusual mission: In order to study the processes of ice production during the arctic winter, the “Polarstern” is heading for ice-free regions. Most of the arctic ice is formed in these so-called polynyas , even thought they are only a very small part of the total ocean area.

Publically, Polynyas became more well-known a few years ago, when a polynya formed right at the north pole. These ice-free regions may be produced by winds that tear open the ice cover and then push the sheets of ice together. They may also generate in places where warm ocean currents melt the ice cover from below.

Sea ice production and ocean currents
Where the ice cover is closed, it works like an isolatiing layer, seperating water from the atmosphere. In the open areas of the Arctic ocean, processes take place that have an influence on the whole arctic climate system. The “Polarstern” will head for those places where polynyas are and study the interaction between atmosphere, ice and ocean. For this purpose, scientists will measure atmosphere and sea ice, whilst at the same time also measure the thickness of the sea ice surrounding the polynyas.

Vortices in the Greenland Sea
Each Winter, in the Greenland Sea, surface water sinks down to the seabed. This newly formed bottom water plays an important role in the worldwide circulation of ocean currents. This sinking, however, is not a regular process. Vortices have been discovered with diameters of 10 to 20 kilometers. The surface water sinks in the centres of these vortices. Such a Vortice may exist over several years. “Polarstern” will head for such a vortice and measure the physical properties in and surrounding it. Data will be collected along a transect at 75 N, in order to better understand the formation of bottom water in the Greenland Sea.

“Polarstern” in drifting sea ice
To study the atmospheric conditions close above the sea ice itself, “Polarstern” will head into the pack ice, become enclosed in it, and then drift with it for about two weeks. With radio sounding ballons and the automatic weather station on board, atmospheric weather data will be collected. At the same time, scientists will measure the the air properties above the sea ice and temperature profiles in the snow and ice layer. This project will be done in collaboration with the Finnish research vessel“Aranda” and the German research plane“Falcon”. Together with ten automatic buoys and several satellite measurements, a large dataset will be gathered in order to test and improve existing computer models for the interaction between sea ice and atmosphere.

Life in winter
During the Winter months, Arctic creatures have not been very well studied. Many species of zooplankton are known to spend the winter in deep waters. In springtime young growth stages are found in the surface layers of plankton blooms. With the “Polarstern”, scientists will study life communities in the pack ice and in the upper surface layers. They will measure physical properties of the habitat in sea ice and below, and study the existing food supply for example ice algae.

The expedition is divided in two parts. In Longyearbyen, Svalbard, a new scientific team comes on board on 24th april. “Polarstern” will be back in Bremerhaven on 14th of may.

 

Bremerhaven, 26th February 2003