[M-IS15] Global Antarctic Science: connecting the chain of changing huge ice sheets and global environments

[MIS15-03] Argo floats unveil the Southern Ocean warming

*Hatsumi Nishikawa¹, Kazuya Kusahara¹, Maki Noguchi Aita¹, Naomi Harada² (1.Japan Agency for Marine-Earth Science and Technology, 2.The University of Tokyo)

The Southern Ocean plays a crucial role in the global climate system. It connects the three major ocean basins, experiences the most extensive seasonal variation in sea ice, and serves as a key formation site for intermediate and bottom waters.These characteristics make it a critical region for understanding global carbon cycling. Since the 2000s, the deployment of Argo floats across the world's oceans has dramatically advanced our understanding of oceanography. Although the number of Argo floats in the Southern Ocean remains lower than in other oceanic regions, the accumulated data has now reached a level where interannual variability can be analyzed. Here, we examine Argo float data from the Southern Ocean to investigate recent upper-ocean temperature changes. Our detailed analysis reveals that warming in the subpolar ocean is evident from the surface to subsurface layers, with the strongest signal observed at the surface. This subpolar ocean warming coincides with the recent decline in Antarctic sea ice, suggesting that it may have contributed to the observed sea-ice loss. With the increasing availability of biogeochemical (BGC) float data from the SOCCOM (Southern Ocean Carbon and Climate Observations and Modeling) project in the Antarctic region, we aim to further explore the impact of ocean warming on marine ecosystems.