How Do Weakening of the Stratospheric Polar Vortex in the Southern Hemisphere Affect Regional Antarctic Sea Ice Extent?. Issue 11 (5th June 2021)

• Record Type: Journal Article
• Authors: Wang, Shaoyin; Liu, Jiping; Cheng, Xiao; Kerzenmacher, Tobias; Hu, Yongyun; Hui, Fengming; Braesicke, Peter
• Is Part Of: Geophysical research letters. Volume 48:Issue 11(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-06-05
• Subjects: Antarctic sea ice -- stratospheric polar vortex -- Amundsen Sea Low -- stratosphere‐troposphere coupling -- sudden stratospheric warmings; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL092582
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: In the Southern Hemisphere, variability of the stratospheric polar vortex is an important driver of surface climate. In this study, we explore the influence of weakening and strengthening of the polar vortex on regional Antarctic sea ice in observations and model simulations. We propose a two‐stage mechanism that translates stratospheric harbingers to sea ice changes: (a) it starts with polar vortex variability that is highly correlated with the Amundsen Sea Low (ASL); through modulation of the ASL and thus surface winds, (b) weak polar vortex leads to statistically significant decrease of sea ice over the Ross Sea and increase of sea ice around the Antarctic Peninsula, and vice versa. The two‐stage mechanism can be detected in observations and state‐of‐the‐art model simulations, confirming a robust chain of response. This study underlines the importance of stratosphere‐troposphere coupling on the Antarctic sea ice variability and its seasonal predictability. Plain Language Summary: Variability of the stratospheric polar vortex in the Southern Hemisphere has been known to influence the surface through the stratosphere‐troposphere coupling. However, it is still unclear how this coupling process relates to the regional Antarctic sea ice variability. Based on the observations and state‐of‐the‐art model simulations, we demonstrate that the stratosphere‐troposphere coupling is highly correlated with the Amundsen Sea Low. We find that weakening and strengthening of the stratospheric polar vortex are associated with significant sea ice anomalies over the Ross and Weddell Seas. The anomalous sea ice changes over the Weddell Sea can last until early austral winter, indicating that the stratospheric polar vortex has a persisting influence on the evolution of the regional Antarctic sea ice. This study therefore highlights that the stratosphere‐troposphere coupling can exert significant impacts on the regional Antarctic sea ice variability and is an important source of seasonal predictability. Key Points: Variability of the stratospheric polar vortex in the Southern Hemisphere is highly related to the Amundsen Sea Low (ASL) in austral spring Through modulation of the ASL and surface winds, polar vortex is associated with significant sea ice changes over the Weddell and Ross Seas The stratosphere‐troposphere coupling is important for the regional Antarctic sea ice variability and its seasonal predictability