7 months on a drifting ice floe

From September 2007 to April 2008, the scientific technician Jürgen Graeser from the Potsdam Research Unit was a member of the NP 35 team. For seven months, the 49-year-old has lived and worked together with twenty Russian colleagues on an ice flow the size of three times five kilometres. While Graeser concentrated on measuring the Arctic atmosphere, the Russian scientists performed investigations of the ocean top layer, the characteristics of the sea ice, the snow coverage and the energy balance above the ice surface. Moreover, they recorded atmospherical data concerning temperature, moisture, wind and air pressure by means of earth stations as well as with ascends of radio sensors. In the course of the winter the ice floe drifted 850 kilometres in northwestern direction over the Arctic Ocean. In April Jürgen Graser was picked up from the ice floe by Polar 5, the research aircraft of the Alfred-Wegener-Institute. A specialised pilot, Brian Burchartz from Enterprise Airlines Oshawa, Canada, accomplished the difficult landing and take-off operation on the ice. “I experienced my stay on the ice floe as an incredible enrichment, under personal as well as professional aspects,” Jürgen Graeser said. The Russian colleagues will continue their measurements until the planned evacuation of the station in September 2008.

The exploration of the atmospheric boundary layer

During the drift Jürgen Graeser has explored the atmosphere above the Arctic Ocean. In order to measure the meteorological structure of the Arctic boundary layer and its temporal changes, he regularly sent out a tethered balloon filled with helium. The six sensors fixed on the tether registered data for temperature, air pressure, moisture and wind and sent them to Greaser’s computer. The exchange processes of heat, impulses and moisture between the earth surface and the atmosphere, which are important for the climate, take place in the layer between the ground and an altitude of about 400 metres. For the first time now the local and temporal structure of ground-level temperature inversions was measured during the complete polar night. To evaluate and interpret the data, the scientists in Potsdam performed simulations with a regional climate model of the Arctic. Preliminary comparisons of temperature profiles measured on the ice floe with those from the regional climate model underline the importance of the measurements performed by Jürgen Graeser. Considerable deviations are shown between the observed data and model data in the region between the ground and an altitude of about 400 metres. Subsequent research activities in Potsdam focus on the connection of the Arctic boundary layer with the development and the tracks of low-pressure areas.

The investigation of the atmosphere – ozone

Vertical high-resolution ozone data from the central Arctic are rare. To close this data gap, Jürgen Graeser regularly launched a research balloon equipped with a radiosonde and an ozone sensor. These balloons carry the sensors up to an altitude of about 30 kilometres. In the past winter, the region of the ozone layer in an altitude of about 20 kilometres was exceptionally cold, thus continuing the trend to colder conditions in this altitude that was observed in the past. The cold conditions have fostered considerable destruction of the Arctic ozone layer in the past winter. The unique measurements of NP 35 will significantly contribute to determine precisely how much of the ozone destruction is caused by human activities.