A long-term shift in flow regimes over the Antarctic Peninsula

Surface warming in the polar regions has important consequences for the stability of the lowest layers of the atmosphere and for atmospheric vertical movement. Here, using ERA5 reanalysis data and in-situ measurements, we quantify the evolving static stability of the lowest 1km of the Antarctic atmosphere and show that the Brunt-Väisälä frequency, a measure of atmospheric stability, has been steadily decreasing since the 1950s. Using satellite observations, reanalysis and targeted climate simulations, we find that this reduced stability has prompted a shift in prevailing flow regimes over the Antarctic Peninsula by altering regional wind flow and enhancing the generation of orographic gravity waves. Increased gravity wave forcing from the Antarctic Peninsula can have important implications for global-scale circulations, polar vortex strength, ozone depletion and mid-latitude weather.