CAREER: The Role of Ice-Nucleating Particles and Their Feedback on Clouds in Warming Arctic Climate

About This Grant

_____________________________________________________________________________________________________________________________ The Arctic is warming rapidly – faster than the rest of the world. A number of processes have been proposed for this so-called Arctic polar amplification. While sea ice is known to play an important role on reflecting solar radiation and altering the Earth’s surface temperature, the roles of other processes are difficult to quantify. Especially, contributions from atmospheric mechanisms associated with ice-nucleating particles (INP; a few in a million aerosol particles below -20 °C) and ice-involved clouds remain uncertain in the Arctic. This project aims to fill the gap by investigating the sources (natural/manmade), atmospheric abundance/budget, chemical composition and physical properties of INPs in the Atlantic sector of the Arctic. Moreover, the large measurement uncertainties in number concentrations, chemical composition and sources of INPs are problematic for modeling real-life phenomena. This research targets minimizing the measurement uncertainties and addresses this critical deficiency through a series of studies that involve direct collection of ice-nucleating particles and their residuals. To characterize Arctic ice-nucleating particles, a novel portable ice nucleation experiment chamber and a cold stage-supported droplet freezing assay will be used to obtain freezing temperature spectra of airborne particle samples. A new inertial ice particle separation technique will be used to collect ice crystal residuals relevant to the Arctic ice-involved clouds. The subsequent offline microspectroscopic characterization of ice crystal residuals and ambient aerosol particles will reveal the relative importance of aerosol physicochemical properties to particle size in ice nucleation. Ultimately, the measurements of INPs and ice crystal residuals from this research will be parameterized and translated to describe the time-resolved freezing ability of the particles as a function of temperature, their composition, water activity parameters and other physicochemical properties. Finally, an integration of research and education is the most important target of this project. This project will involve two graduate and several undergraduate students in research, curriculum development and outreach, as these are learning experiences that can aid in their professional development. This project will also develop hands-on curricular modules integrated with the proposed research to teach environmental and climate science to the general public, promote college courses and train future scientists. Currently, there is a critical deficiency in Arctic field data regarding the abundance and composition of atmospheric ice-nucleating particles at temperatures above -15 °C. This project will fill this gap by experimentally elucidating abundance and physicochemical properties of ice-nucleating particles. State-of-the-art representations of high-temperature INPs from the Atlantic sector of the Arctic will advance the atmospheric modeling community’s knowledge of the ice nucleation processes and its formulation in the Earth’s energy balance. The project also aims to provide robust and well-characterized INP measurements that will be archived in the publicly available university database. The measurements from this project, in collaboration with the existing transnational Arctic research community, will improve the understanding of the nature of aerosols, and the INP parameterizations representative of the Ny-Ålesund site will dramatically improve the understanding of ice formation processes that are currently very poorly represented in climate models. In addition, this research activity directly aligns with one of the NSF’s 10 priority research areas, “Navigating the New Arctic”. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.