Vertical Turbulent Aerosol Particle Transport above open Water and Ice in the central Arctic during Summertime (APAICA) - Aerosol particle sources and transformation in the Arctic marine boundary layer

• Applicants: Professor Dr. Andreas B. Held; Dr. Birgit Wehner
• Subject Area: Atmospheric Science
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 495992836

The strongest temperature increase due to climate change is currently observed in the Arctic. This fact is based on a very complex chain of processes and feedbacks, in which aerosol particles play an essential role through their influence on radiation balance and cloud formation. In order to assess the impact of changing ice cover, the interactions between ocean as well as ice and the atmosphere also need to be better understood. In general, there is a lack of atmospheric measurements especially in the Arctic Ocean, which are urgently needed to understand the processes but also to predict the expected changes. Exchange processes between ocean/ice and atmosphere are currently poorly understood in these regions. In this project, the RV Polarstern will be used to study vertical exchange processes above water and ice in detail and to localize associated sources of aerosol particles. For this purpose, a series of continuous aerosol measurements on board the ship are planned, including number size distributions, optical parameters (scattering, absorption), the mixing ratio of particles containing black carbon (BC), the concentration of ice nucleating particles (INP), and the chemical composition of aerosol particles. Furthermore, samples of fog water will be collected during fog phases that occur frequently in summer, as well as daily water samples from the ocean throughout the campaign. These samples will be analyzed for the concentration of INP and BC after the measurement campaign. For the first time, BC- concentrations in airborne and water samples will be measured for the using laser incandescence. A novel method for pre-treatment of water samples with high salinity will be applied. By this combination of parallel investigation of components in air and water, transport and exchange processes of these aerosol particles shall be quantified.In the periods with calm movement of the ship or drift with the ice, measurement equipment for the determination of vertical particle fluxes will be employed at the frontal outrigger of the ship. This will be used to acquire time series of the wind vector and particle concentration, which will subsequently be used to determine the vertical turbulent particle flux by the eddy covariance method. Combined with these measurements, the concentration of the INP is recorded in order to be able to assign their origin and sources. Another measuring system, consisting of a one-dimensional wind measurement and a particle counter, is attached to the crane hook below the frontal outrigger and determines the vertical profiles of the particle concentration from which an estimation of the vertical particle flux is also possible. These methods are proven and established, but have never been applied in this way over the Arctic Ocean.

• DFG Programme: Research Grants