Atmospheric and Surface Processes, and Feedback Mechanisms Determining Arctic Amplification: A Review of First Results and Prospects of the (AC)3 Project

Abstract

Mechanisms behind the phenomenon of Arctic amplification are widely discussed. To contribute to this debate, the (AC)3 project has been established in 2016 (http://www.ac3-tr.de/). It comprises modeling and data analysis efforts as well as observational elements. The project has assembled a wealth of ground-based, airborne, ship-borne, and satellite data of physical, chemical, and meteorological properties of the Arctic atmosphere, cryosphere, and upper ocean that are available for the Arctic climate research community. Short-term changes and indications of long-term trends in Arctic climate parameters have been detected using existing and new data. For example, a distinct atmospheric moistening, an increase of regional storm activities, an amplified winter warming in the Svalbard and North Pole regions, and a decrease of sea ice thickness in the Fram Strait and of snow depth on sea ice have been identified. A positive trend of tropospheric bromine monoxide (BrO) column densities during polar spring was verified. Local marine/biogenic sources for cloud condensation nuclei and ice nucleating particles were found. Atmospheric/ocean and radiative transfer models were advanced by applying new parameterizations of surface albedo, cloud droplet activation, convective plumes and related processes over leads, and turbulent transfer coefficients for stable surface layers. Four modes of the surface radiative energy budget were explored and reproduced by simulations. To advance the future synthesis of the results, cross cutting activities are being developed aiming to answer key questions in four focus areas: lapse rate feedback, surface processes, Arctic mixed-phase clouds, and air mass transport and transformation.

Marine Cold‐Air Outbreak Snowfall in the North Atlantic: A CloudSat Perspective

“…This window contains the region where the field campaign COMBLE recently studied upstream meteorological conditions during MCAO events between Svalbard and Scandinavia (Geerts et al, 2022). For several decades, field campaigns have used aircraft measurements to study MCAOs in the Fram Strait and Norwegian Sea (Brümmer, 1992(Brümmer, , 1996Wendisch et al, 2019Wendisch et al, , 2022.…”

Evaluating Causal Arctic‐Midlatitude Teleconnections in CMIP6

“…Different mechanisms have been suggested to contribute to the amplified Arctic warming, such as changes in the snow-and ice-albedo feedback (Serreze & Barry, 2011), lapse rate feedback (Pithan & Mauritsen, 2014), cloud cover and water vapor feedback (Graversen & Wang, 2009), an increase of atmospheric CO 2 (Previdi et al, 2020), or poleward heat and moisture transport (Sang et al, 2022) and ocean heat uptake (Previdi et al, 2021). The overviews of major Arctic climate feedbacks are, for example, provided by Goosse et al (2018), Previdi et al (2021), Vavrus (2018), and Wendisch et al (2022).…”

MOSAiC-ACA and AFLUX - Arctic airborne campaigns characterizing the exit area of MOSAiC

“…The German DFG project -TRR 172, "ArctiC Amplification: Climate Relevant Atmospheric and SurfaCe Processes, and Feedback Mechanisms (AC) 3 " 13,14 , a joint research initiative of the Universities Leipzig, Cologne, and Bremen and of the research institutes TROPOS (Leipzig) and Alfred Wegener Institute (AWI Bremerhaven and Potsdam), is investigating the processes and feedback mechanisms related to Arctic amplification by model studies and observations. To bridge the gap between localized ground based observations with a high temporal resolution and satellite borne observations providing a good areal coverage, but poor resolution in time and space, airborne measurements are well suited to study atmospheric processes especially close to the sea ice edge, Platform and campaign set up.…”