Research aircraft Polar 5 finishes Arctic expedition

The Arctic campaign PAM-ARCMIP (Pan-Arctic Measurements and Arctic Climate Model Intercomparison Project) ended yesterday in Ottawa with the participation of the research aircraft Polar 5. The campaign which lasted four weeks yielded unique measurement data on sea ice thickness, trace gases, aerosols and meteorological parameters thanks to the great range of the aircraft and modern measurement equipment. 'We were out and about in mainly unchartered territory. Our most northerly position was 88 40' N. Flight operations of this kind require a high degree of proficiency and a lot of experience,' reports Dr Andreas Herber, physicist and in charge of the research aircrafts belonging to the Alfred Wegener Institute. The weather was mostly ideal for measurement purposes. Air temperatures below -30 C however posed a frequent challenge for the scientific equipment. 20 researchers and engineers from six different research institutes from Germany, Italy (CNR-ISAC Bologna), Canada (Environment Canada, University of Alberta, York City) and the USA (NOAA-ESRL Boulder) were participating, and they will evaluate the data in the coming months.

The flight of Polar 5, belonging to the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association, led from Longyearbyen on Spitsbergen via Greenland and northern Canada up to Barrow in Alaska. Polar 5 landed also as the first aircraft ever on ice of two metres thickness at the position 87 40' N/117 00' W on the Russian ice floe drift station NP-36. The whole campaign was a success thanks to the close international collaboration and the extraordinary support at the research stations like Alert and Eureka.

A focal point of the campaign was on Arctic aerosols. An image of the aerosol distribution in the Arctic was produced by means of multiple vertical and horizontal profiles in low-level flight altitude (60 metres) and in normal flight altitude (3.000 metres). Aerosols belong, together with water droplets and ice crystals, to the climate relevant trace substances. They rank among the greatest uncertainty factors regarding the evaluation of future climate change. The measurements above the Arctic Ocean make the quantification of aerosol pollution of the Arctic clean air and its allocation to Asiatic, North American and European source regions possible. They are a realistic foundation for the much needed improvement of model computations for this inaccessible and for climate research essential region of the earth.

Another focal point of the campaign were large-scale measurements of ice thickness in the inner Arctic, which were conducted in close collaboration of the Alfred Wegener Institute together with the University of Alberta. An ice-thickness sensor, the so-called EM-Bird, was put into operation under a plane for the first time ever. To conduct the measurements, Polar 5 dragged the sensor which was attached to a steel cable of eighty metres length in a height of twenty metres over the ice cover. Multiple flights northwards from various stations showed an ice thickness between 2.5 (two years old ice in the vicinity of the North Pole) and 4 metres (perennial ice in Canadian offshore regions). All in all, the ice was somewhat thicker than during the last years in the same regions, which leads to the conclusion that Arctic ice cover recovers temporarily. The researchers found the thickest ice with a thickness of 15 metres along the northern coast of Ellesmere Island.

Another highlight of the campaign were atmospheric probes in the central Arctic and measurements of low level ozone and mercury concentrations over large areas of the sea ice-covered Arctic Ocean. The meteorological probes were conducted by means of drop sondes. They yielded shallow boundary layers in conjunction with pronounced temperature inversions and wind jets in the lowest 300 metres. These conditions probably favoured the near surface ozone concentration over the sea ice as measured by the team from Environment Canada, caused by a reaction with bromine oxide (BrO). The combination of all trace gas measurements by means of atmospheric probes will allow a better understanding of the processes of near surface ozone depletion in the Arctic.

This logistically demanding campaign with residence in four different riparian Arctic states was only possible due to the close international collaboration between all partners involved.