Arctic Air Pollution: New Insights From POLARCAT-I PY

POLARCAT provided a wealth of data on the concentrations and sources of short-lived climate pollutants (aerosols, ozone) and their precursors in the Arctic. Given the rapid nature of climate change occurring in the Arctic and the difficulty for climate models to quantitatively reproduce observed changes such as sea ice loss, it is important to improve understanding of the processes leading to climate change in this region, including the role of short-lived climate pollutants such as aerosols and ozone. It has long been known that pollution produced from emissions at mid-latitudes can be transported to the Arctic resulting in a winter/spring aerosol maximum known as Arctic Haze. However, many uncertainties remain about the composition and origin of Arctic pollution throughout the troposphere; for example, many climate-chemistry models fail to reproduce the strong seasonality of aerosol abundance observed at Arctic surface sites, the origin and deposition mechanisms of black carbon (soot) particles that darken the snow and ice surface in the Arctic is poorly understood, and chemical processes controlling the abundance of tropospheric ozone are not well quantified. The International Polar Year (IPY) core project POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, Climate, Chemistry, Aerosols and Transport) had the goal to improve understanding of the origins of pollutants transported to the Arctic, to detail the chemical composition, optical properties, and climate forcing potential of Arctic aerosols, to evaluate the processes governing tropospheric ozone, and quantify the role of boreal forest fires. This article provides a review of the many results now available based on analysis of data collected during the POLARCAT aircraft, ship and ground-based field campaigns in spring and summer 2008. We highlight major findings and discuss areas requiring further investigation.