CHACHA

CHACHA aims to assess the extent to which Arctic change, particularly sea ice loss and increased fossil fuel extraction in the New Arctic, modifies multiphase halogen, nitrogen, and sulfur chemistry, in turn affecting aerosols, clouds, and the fate of Arctic pollution. It is critical to understand these interactions between changing anthropogenic and natural emissions to evaluate and predict the impacts of environmental change and development on the Arctic and atmospheric composition. To pursue this research theme, we propose a focused airborne study of interactions between reactive gases, particles, and clouds, combined with modeling of chemical and physical processes in the vicinity of oil and gas extraction activities and sea ice leads. These studies are centered on three CHACHA testable operational hypotheses:

Hypothesis 1: Open sea ice leads are the largest source of early spring aerosol mass to the Arctic boundary layer, affecting aerosol and cloud chemical composition, ozone, and other gases.

Hypothesis 2: Oil and gas extraction activities contribute to gas emissions that significantly modify natural halogen chemistry, impacting multiphase halogen recycling and activation, as well as the fate of NOx and ozone.

Hypothesis 3: Atmospheric oxidative processing of sulfur, nitrogen and other chemical species differs between clear-sky conditions, and those impacted by in-cloud chemical processing.

The approach for this project is to utilize the Wyoming King Air aircraft and the Purdue University ALAR aircraft to study how changes in development, sea ice, and warming in the Arctic are changing atmospheric composition and chemistry. More specifically, our aim is to quantify trace gases, aerosols, and cloud particles above and downwind of sea ice leads and the Prudhoe Bay oilfields in Alaska, to evaluate the effects of natural and anthropogenic emissions on halogen chemistry and aerosol and cloud composition.

Intellectual Merit

While the atmospheric science community has made great strides in the past thirty years in developing an improved understanding of the role of halogen chemistry in ozone and mercury depletion events in polar regions, the majority of the observations have been conducted at the ground under conditions of consolidated sea ice and a clean Arctic, with little knowledge of the roles of surface state, turbulence, aerosols and clouds.

The proposed CHACHA aircraft-based observations, combined with numerical modeling, will significantly improve our understanding of atmospheric composition and cloud interactions in the New Arctic, while providing new information on the 3D composition of the Arctic lower tropospheric gas, aerosol and cloud phases. In so doing, CHACHA will address the overarching project objective: “CHACHA aims to assess the extent to which Arctic change, particularly sea ice loss and increased fossil fuel extraction in the New Arctic, modifies multiphase halogen, nitrogen, and sulfur chemistry, in turn affecting aerosols, clouds, and the fate of Arctic pollution.”

The team will directly address fundamental questions about Arctic atmospheric turbulence, the vertical propagation of halogen chemistry above various surfaces, and multiphase halogen reactions involving aerosols and cloud droplets, as impacted by the changing sea ice. Given increasing development within the Arctic, the team will also investigate the roles of combustion emissions on trace gas, aerosol and cloud composition, and interactions with halogen chemistry. Overall, the results of this project will lead to critical improvements in our ability to simulate the changing Arctic atmospheric composition.