Trends and variability in polar sea ice, global atmospheric circulations, and baroclinicity

• Published in: Annals of the New York Academy of Sciences
• Main Authors: Simmonds, Ian, Li, Muyuan
• Other Authors: Australian Research Council, National Natural Science Foundation of China
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2021
• Subjects: Antarctic; Arctic; The Antarctic; Antarc*; Sea ice
• Online Access: http://dx.doi.org/10.1111/nyas.14673; https://onlinelibrary.wiley.com/doi/pdf/10.1111/nyas.14673; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/nyas.14673; https://nyaspubs.onlinelibrary.wiley.com/doi/am-pdf/10.1111/nyas.14673; https://nyaspubs.onlinelibrary.wiley.com/doi/pdf/10.1111/nyas.14673

Abstract We analyze the polar sea ice distribution and the global sea level pressure (SLP) and baroclinicity distributions over the “satellite” period of 1979–2020. In the Arctic, there are statistically significant sea ice extent (SIE) decreases in all calendar months, and the annual mean has lost 2.22 million km 2 over the four decades. The Antarctic SIE, in marked contrast, increased up to 2014, then commenced a remarkable retreat (the annual mean ice extent decreased by 2.03 million km 2 in the 3 years to 2017), and subsequently increased to near its long‐term average value in 2020. The shifts in seasonal‐mean SLP patterns are consistent with a warming planet. At the synoptic scale, we diagnose the changes in the baroclinicity, the mechanism by which cyclones, fronts, and other weather systems are generated. Through a novel presentation, we give an overview of the relative roles of changes in the vertical shear and static stability in influencing the global trends in baroclinicity. In both the Arctic and Antarctic regions, baroclinicity is shown to have increased in each season (with the sole exception of the Arctic in summer). This increase, coupled with midlatitude decreases in baroclinicity, results in poleward shifts of the storm tracks.