The lower air layers play a crucial role in climate change in the Arctic. In order to close the gap between ground measurements and aircraft data, scientists are currently carrying out measurements with a tethered balloon on Svalbard. It collects data up to a kilometer in height that is intended to improve and refine the existing climate models. In addition, these measurements provide valuable information about the interactions between the Arctic Ocean and the atmosphere.
The Arctic is a hotspot of climate change: almost nowhere is global warming as noticeable as beyond the Arctic Circle. Mean temperatures have increased several degrees more than the global average, while the decline in Arctic sea ice is changing local and regional weather conditions. So far, however, climate models can only partially understand which mechanisms are driving this disproportionately strong warming in the Arctic.
From the Polarstern to Spitsbergen
The MOSAiC expedition already collected valuable data on climate processes in the central Arctic last year. For a year, the German research icebreaker Polarstern, together with its measuring station on the neighboring ice floe, drifted through the Arctic sea with transpolar drift. This enabled the researchers to obtain data on the atmosphere, ice and ocean in the middle of polar winter for the first time. Even during this drift, a helium-filled tethered balloon from the Leibniz Institute for Tropospheric Research (TROPOS) and the University of Leipzig was used. The twelve meter long and 90 cubic meter large balloon collected data on the air layer over the melting ice floe in 33 ascents.
Now this balloon system is also being used at the polar research station AWIPEV in Ny-Ålesund on Spitsbergen. The first part of the measurement campaign will continue to investigate the conditions in arctic autumn at the transition to polar night until mid-November 2021. The second part will take a close look at the transition to the melting period in arctic spring from mid-March to mid-May 2022. This enables the scientists to study the interactions between the sea, the atmosphere and the ice as the seasons change. The balloon, which can be hauled in on a long rope, has measuring devices on board that measure turbulence, radiation, clouds and aerosols as well as take particles and cloud water samples.
Crucial layers of air
The exciting thing about it: The helium balloon made it possible to take measurements at a height of up to 1000 meters. Although these lower layers of air are particularly important for climate processes, they are difficult to capture from the ground or from airplanes. “The cloudy Arctic boundary layer is characterized by a complex vertical stratification, which often decouples from the surface. Clouds have a strong influence on the exchange of heat between the ground and higher air layers and have considerable effects on the energy balance, ”explains Holger Siebert from TROPOS, who heads the balloon campaign. Current models often cannot describe these complex processes through the clouds realistically enough.
In order to be able to collect even more precise data, the second part of the balloon measurements on Spitzbergen will be carried out parallel to the HALO- (AC) ³ aircraft campaign. For the first time, the German research aircraft HALO, Polar 5 and Polar 6 will fly together with the balloon in the Arctic and examine the atmosphere in parallel at different altitudes. You should observe the warm air transport into the Arctic and its effects in detail. “We simply cannot fly as deep and as slowly as we want with the airplanes, and certainly not in the narrow fjord off Ny-Ålesund. Our balloon measurements have to cover this altitude range, which is extremely important in the Arctic for all exchange processes between the ground and the Arctic atmosphere, ”explains André Ehrlich from the University of Leipzig.
The combined measurement campaign not only offers opportunities for new insights into the investigation of clouds and their energy balance, atmospheric chemistry is also hoping to gain new insights into the feedback between biological activity and climate: “We are interested in the interactions between the ocean and the atmosphere – especially in the polar regions that are severely affected by climate change, ”explains Sebastian Zeppenfeld from TROPOS. In previous measurement campaigns, he and his colleagues had found initial indications that there are bacteria in the air that eat up substances that are blown up from the sea. “We now want to get to the bottom of this on Svalbard by measuring the sugars in aerosols, cloud water and surface film and also cultivating the bacteria,” says Zeppenfeld.
Source: Leibniz Institute for Tropospheric Research e. V.