Aircraft and Ship-Based Measurements of Ice Nuclei from the Arctic Campaign ICE-ACCACIA

Low level, stratus clouds are ever-present in the arctic region. These clouds play an important role in the arctic climate system but our current understanding of their formation and persistence is very poor.

The majority of clouds in this region are categorized as mixed phase clouds, or those containing both supercooled water droplets and ice crystals. Ice crystal formation is typically observed when cloud droplets contain particles known as ice nuclei (IN) that act as surfaces for ice crystal formation and growth. At lower latitudes, IN are typically composed of mineral dusts, soot or even bacteria, but the composition, concentration and sources of IN in the pristine arctic environment remains a mystery.

During the March 2013 arctic campaign ICE-ACCAICA, hydrophobic filters were used to collect aerosol on board the FAAM BAe-146 research aircraft. During the ship-based portion of the same campaign, further filters were collected in July 2013 aboard the RRS James Clark Ross icebreaker. Filter samples were transported back to University of Leeds for laboratory analysis using a modified Filter Drop Freezing (FDF) technique.

IN activity per volume of air is reported as a function of temperature and normalized using particle surface area for comparison to other studies. SEM/EDX analysis was used to determine size-distribution and elemental composition of ambient aerosol particles collected in tandem with filters for ice nucleation experiments.

We present results from immersion mode ice nucleation experiments performed using both aircraft and ship-based filter sets. IN efficiency and concentrations are reported at sea level, for below cloud and above cloud flight tracks as well as over sea ice versus open water.