Frozen in the Arctic sea ice, scientists from 20 nations spent one year on board the German research icebreaker Polarstern to investigate the epicentre of climate change. The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), coordinated by the Alfred Wegener Institute, is one of the largest polar expeditions of all time. The mobile ACTRIS platform OCEANET-Atmosphere, developed and maintained by the Leibniz Institute for Tropospheric Research (TROPOS), has been operated at the foredeck of Polarstern next to the ARM [1] mobile facility (AMF). Throughout the ice drift, the two platforms continuously explored the vertical aerosol and cloud distribution using a PollyXT lidar, two cloud radars, four microwave radiometers, and many other instruments. On 24 February 2020, the drift took Polarstern to 88°36’ N, just 156 kilometres from the North Pole. Never before has a ship ventured so far north during the Arctic winter. After the first ice floe had drifted from the central Arctic further south and melted, Polarstern went back to the ice area to study the freezing processes at the end of the summer and crossed the North Pole on 19 August 2020.
The OCEANET-Atmosphere container is supervised by a science team from TROPOS. During each leg, one scientist ensured that the instruments acquire high-quality data and that the data streams are operational. Ronny Engelmann set up the instruments in September 2019 and experienced how the days became shorter and shorter until the polar night. His colleague Hannes Griesche replaced him shortly before Christmas and experienced the coldest and darkest months in the Arctic when temperatures dropped below -30 °C. Shortly before the sun rose again in March, he was replaced by Martin Radenz. Julian Hofer took over in the Arctic summer and had to watch the ice floe camp thawing until it finally had to be cleared by the expedition team. On the last leg of the journey, Dietrich Althausen obtained how the ice forms again in the Arctic autumn and completed the measurements at the end of September 2020. The one-year expedition enabled the mobile ACTRIS station to collect a valuable dataset on the state of the atmosphere in all Arctic seasons.
Links:
https://mosaic-expedition.org/
https://follow.mosaic-expedition.org/
https://www.tropos.de/en/current-issues/campaigns/blogs-and-reports/mosaic-2919-2020
[1] ARM is the Atmospheric Radiation Measurement program of the U.S. Department of Energy
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