Picture: Three masted ship amid the ice. Credit: Torsten Dederichs (Unsplash).
The Amundsen Sea Low (ASL) is the deepest climatological low-pressure system on the planet and is located offshore of western Antarctica. The ASL affects air and ocean temperature, precipitation, sea‐ice, and ice shelves in the West Antarctica region.
Given the importance of the ASL for changes in the West Antarctic region, including its impacts on the West Antarctic Ice Sheet, it has been a major focus of studies for meteorologists, oceanographers and glaciologists over the past couple of decades. Despite dozens of research articles on the past and projected future changes in the ASL and their impacts on the west Antarctic climate system, we still don’t have a good understanding of why it exists.
In this study, researchers combine techniques from climate modelling and aircraft aerodynamics software to uncover mechanisms responsible for generating this climatological low pressure near Antarctica.
Several different theories have been proposed in the past 30 years to explain the mechanisms behind the generation of the ASL. While some earlier studies proposed an important role of the shape and/or the height (mountains) of the Antarctic continent, more recent studies have suggested an important role played by the tropics and /or the mid-latitude cyclones in generating the climatological ASL.
In this study, researchers tested all these previously proposed hypotheses with some creative atmospheric model simulations by changing the height of Antarctica (or even making it flat at sea level) and by rotating only Antarctica by 100 degrees westward while keeping all the other features at the same place. Given a number of processes impacting the ASL at the same time, these innovative approaches were required to separate out the roles played by different processes in generating the ASL.
Researchers found the ASL is generated by the local processes occurring close to Antarctica with little to no role played by the tropics. They found the ASL is solely generated by the flow separation because of the interaction of the westerly winds with the high orography of the Victoria land. A non-rotating barotropic fluid flow simulation was also carried out using an aircraft aerodynamics fluid flow simulator (ANSYS Fluent) to confirm this hypothesis.
The authors also noted that while the tropics do not play an important role in generating the ASL, changes in the tropics from natural variability or because of climate change can generate strong changes in the ASL and therefore over West Antarctica.
- Paper: Goyal, R., Jucker, M., Sen Gupta, A., & England, M. H. (2021). Generation of the Amundsen Sea Low by Antarctic orography. Geophysical Research Letters, 48, e2020GL091487. https://doi.org/10.1029/2020GL091487