The Influence of Ozone Depletion on the Amundsen-Bellingshausen Seas Low

The Amundsen-Bellingshausen Seas Low (ABSL), a semi-permanent low pressure off the coast of West Antarctica, has important monthly and seasonal variations that are not yet fully understood. Since the presence of the ABSL contributes to the marked warming and sea ice loss occurring in the region, it is necessary to further characterize these variations. A recent study suggested that a portion of the ABSL variations, and particularly their impact on the austral autumn sea ice conditions in the Ross, Amundsen, and Bellingshausen Seas, were due to stratospheric polar ozone depletion. With this in mind, this study seeks to determine the sensitivity of the ABSL to ozone depletion and changes in greenhouse gas concentrations using chemistry-climate models (CCM), which more accurately depict the stratosphere where ozone-depleting processes occur. Our analysis is done using CCM data from the Stratospheric Processes and their Role in Climate (SPARC) Chemistry-Climate Model Validation project phase 2 (CCMVal2), focusing on the region of the ABSL [55°-75°S; 180°-60°W]. Temperature, wind, and geopotential height at various pressure levels are examined for the period of 1979-2001. Comparisons are made with two sensitivity runs: one with constant ozone and one with constant greenhouse gas levels. The same variables are also compared to the NNR, ERA-40 and JRA-25 reanalysis datasets for model validation. While there are some intermodel differences, we note that both ozone depletion and changing greenhouse gas levels have an impact on the ABSL, but only during certain months. The forcing is greatest in the stratosphere, and much smaller in amplitude near the troposphere. Results from this study can increase our understanding of how the ABSL might respond to changes in ozone and increasing greenhouse gas concentrations, and therefore the future impact it will have on the climate of the region.