Research to continue on Arctic amplification and its global impacts

Leipzig/Köln/Bremen, 24.11.2023

Collaborative Research Centre / Transregio 172 “Arctic Amplification (AC)³” renewed again



The Collaborative Research Centre “Arctic Amplification: Climate Relevant Atmospheric and Surface Processes and Feedback Mechanism (AC)³” is to enter its third funding phase. This was announced today (24 November 2023) by the German Research Foundation (DFG). From January 2024, the research network, which also includes the Universities of Bremen and Cologne, the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and the Leibniz Institute for Tropospheric Research (TROPOS), will continue its ground-breaking work for another four years. The overall aim is to make fundamental and significant advances in our understanding of Arctic amplification and improve the reliability of models used to predict the dramatic warming of the Arctic.


“Over the past 25 years, we have observed a drastic increase in near-surface air temperatures in the Arctic, which is two to three times more pronounced than global warming,” says Professor Manfred Wendisch from Leipzig University, spokesperson for the Collaborative Research Centre. This phenomenon, which the interdisciplinary network has been studying and trying to understand for eight years using various scientific methods, is known as Arctic amplification. Professor Susanne Crewell, deputy spokesperson from the University of Cologne, explains: “In recent years, we have been able to quantify seasonal differences and better understand the interaction of various feedback mechanisms that are thought to be the cause of Arctic amplification.” Dr Gunnar Spreen, deputy spokesperson from the University of Bremen, adds: “This is connected to a dramatic decrease in sea ice. In summer, we only have about half of the ice that we had 40 to 50 years ago. The (AC)³ is investigating which interactions between the atmosphere and ocean play a role here.”


What the researchers have found out so far

The scientists have used existing and new data to identify short-term changes and indications in Arctic climate variables. “The Arctic atmosphere has become significantly wetter. Storm activity has also increased regionally,” summarises Manfred Wendisch. In addition, winter warming has intensified in the regions around Svalbard and the North Pole, which has led to a decrease in the thickness of sea ice in the Fram Strait and snow depth on the ice.


The research aircraft HALO and the polar aircraft Polar 5 and 6 in conjunction with the icebreaker Polarstern have been used on expeditions to the Arctic. The latter were part of the MOSAiC expedition led by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). The Collaborative Research Centre (AC)³ was the main German university contribution to MOSAiC.


Future priorities and projects

The Collaborative Research Centre / Transregio 172 “Arctic Amplification (AC)³” will answer three central questions in its third phase:

•          What are the main causes and to what extent do these contribute to Artic amplification?

•          How do changes in the transport of air masses impact the weather and climate in the Arctic and mid-latitudes?

•          What trends can be identified that are caused by Arctic amplification and how will they develop in a future, warmer climate?

To better link their results in the future, the researchers are developing cross-cutting themes to answer key questions in four key areas: the vertical temperature gradient, surface processes, Arctic mixed-phase clouds, and transport and transformation of air masses.

The main objective of the third phase of the Collaborative Research Centre (AC)³ is to bring together the numerous observational and modelling results from the previous phases in order to make fundamental and significant advances in our understanding of Arctic amplification. In the coming years, the interdisciplinary network’s research questions will continue to provide the basis for ground-breaking insights into arctic climate change. These will also contribute to addressing the challenges of climate change on a global scale.

The hygroscopicity of aerosol particles is an important factor in the effect of aerosol particles on the climate and thus also for forecasting changes to the climate using global climate models. "The capacity to hold water depends on the composition of aerosol particles, which can vary considerably in the atmosphere. However, in our study we were able to show that simplified assumptions can be made for the consideration of hygroscopicity in climate models," explains Mira Pöhlker. She is in charge of the "Atmospheric Microphysics" department at TROPOS and is a professor at the University of Leipzig. According to the aerosol and cloud researcher, this is the first study to use measurement results from across the world to show that a simple linear formula can be used without creating huge uncertainty in climate models.


TROPOS contribution to (AC)³

In the third phase, TROPOS will extend the coverage of Arctic cloud cover and its climate effects from the MOSAiC expedition to the entire Arctic and supplement detailed measurements of the Arctic boundary layer as a key climatic region. Aerosol climate models will be used to investigate the effects of anthropogenic and natural aerosols on the warming of the Arctic climate, with a particular focus on changing aerosol patterns and their significance for air mass transport and the energy balance. A further contribution will investigate the changes in Arctic cloud cover caused by cold air outbreaks using high-resolution aircraft observations and long-term satellite data. Overall, with its focus on aerosols, aerosol-cloud interactions and the radiation balance, TROPOS contributes to the understanding of changes in the Arctic and the connections with the global climate system.






Media contacts:

Prof. Dr. Manfred Wendisch,
Speaker of the Collaborative Research Center SFB/TRR 172 "Arctic Amplification (AC)³" and University Professor for Atmospheric Radiation, Leipzig University,
Phone +49-341-97-32850,

Prof. Dr. Andreas Macke,
Director, Leibniz Institute for Tropospheric Research (TROPOS),
Phone +49 341 2717-7060,


Media Team, Office for University Communications, Leipzig University,
Phone +49-341-97-35025,

Tilo Arnhold, Public Relations, Leibniz Institute for Tropospheric Research (TROPOS), Leipzig,
Phone +49-341-2717-7189,



Further information and links:


DFG Collaborative Research Centre / Transregio 172 “Arctic Amplification: Climate Relevant Atmospheric and Surface Processes and Feedback Mechanisms (AC)³”



Dramatic warming in the Arctic – HALO-(AC)3 field campaign investigates a worrying phenomenon (Press relation, 18.03.2022)

Unique view into the "new Arctic": International MOSAiC expedition successfully completed (Press release, 12.10.2020)

MOSAiC Expedition 2019 – 2020

Substantial funding for DFG Transregional Collaborative Research Centre on "Arctic Climate Change" (Press release, 20.11.2015)



The Leibniz Institute for Tropospheric Research (TROPOS) is a member of the Leibniz Association, which connects 97 independent research institutions that range in focus from the natural, engineering and environmental sciences via economics, spatial and social sciences to the humanities. Leibniz Institutes address issues of social, economic and ecological relevance. They conduct knowledge-driven and applied basic research, maintain scientific infrastructure and provide research-based services.

The Leibniz Association identifies focus areas for knowledge transfer to policy-makers, academia, business and the public. Leibniz institutions collaborate intensively with universities – in the form of “Leibniz ScienceCampi” (thematic partnerships between university and non-university research institutes), for example – as well as with industry and other partners at home and abroad.

They are subject to an independent evaluation procedure that is unparalleled in its transparency. Due to the importance of the institutions for the country as a whole, they are funded jointly by the Federation and the Länder, employing some 20,500 individuals, including 11,500 researchers.

The entire budget of all the institutes is approximately 2 billion euros. They are financed jointly by the Federal Government and the Länder. The basic funding of the Leibniz Institute for Tropospheric Research (TROPOS) is therefore financed by the Federal Ministry of Education and Research (BMBF) and the Saxon State Ministry of Science and the Arts (SMWK). The Institute is co-financed with tax revenues on the basis of the budget approved by the Saxon State Parliament.


The tethered balloon from TROPOS and Leipzig University in use on the ice floe during the MOSAiC expedition 2020. Photo: Christian Pilz, TROPOS

The tethered balloon from TROPOS and Leipzig University in use on the ice floe during the MOSAiC expedition 2020. Photo: Lianna Nixon, University of Colorado / AWI

Lidar of the OCEANET container during the polar night at MOSAiC. Photo: Ronny Engelmann, TROPOS

The research icebreaker Polarstern during MOSAiC in the Arctic. Photo: Hannes Griesche, TROPOS