BromoPole

This project aims at improving our understanding of the mechanisms of polar bromine explosion and ozone depletion events in the polar troposphere. We study their impact on the larger scale through global chemistry climate model simulations and to test a new hypothesis, whether accumulated deposition from the gas phase plays an role as source of bromine in surface snow. To this end, a snow sampling campaign has been conducted in Ny-Ålesund (Spitsbergen) in Spring 2024 to suplement exiting, regular measurements to be anaylized for bromine.

Tropospheric ozone is after carbon dioxid and methane the most important greenhouse gas and affects air quality with implications for health and eco systems. During spring-time in the polar regions of both hemispheres tropospheric ozone depletion events (ODEs) with near complete removal of boundary layer ozone are frequently observed. These ozone depletion events are caused by so-called bromine explosion events, that can be observed as strongly enhanced tropospheric bromine monoxide (BrO) columns. There is still no generally accepted comprehensive mechanism, and consequently most chemistry climate models (or modelling studies) do not include mechanisms of polar tropospheric bromine chemistry.

We use the ECHAM/MESSy Atmospheric Chemistry (EMAC) model in this project and elaborate on previous work that included a bromine release mechanism from and recycling on ice and snow in the Arctics. We compare our model predictions with observations from ozone monitoring sites, the snow samples taken at Ny-Ålesund (Spitsbergen), BrO vertical column densities from TROPOMI satellite, and data collected during the MOSAiC campaign. A participation in an international model intercomparision on Arctic ozone and bromine is also underway.