Vertical Motion in the Southern Ocean

• Maya Feinstein, Marine Science, University of Delaware

• Xinfeng Liang, School of Marine Science and Policy, University of Delaware

Vertical motions (upwelling and downwelling) play an essential role in the vertical transport of oceanic properties and materials. While past studies have reported intense upwelling and downwelling in the Southern Ocean, a comprehensive analysis dedicated to these vertical motions in the Southern Ocean remains to be accomplished. Here, we analyze vertical velocity estimates in the Southern Ocean from the ocean synthesis product ECCOv4, focusing on its spatial and temporal variability. We find that intense downwelling and significant temporal variations occur around Antarctica due to deep water formation. Other large temporal variations are observed near bathymetric features (e.g., Campbell Plateau). We also find that near the Drake Passage, the abyssal layer exhibits the fastest upwelling compared to shallower layers, indicating topographic-related upwelling. Additionally, in the upwelling region of 60-65°S, 115-120°E, there is an increasing upwelling speed trend between 2000 and 2005. Meanwhile, a nearby downwelling region at 47-52°S, 115-120°E, shows a decreasing downwelling speed trend during the same period. These results reveal strong interannual variations in oceanic vertical motions in the Southern Ocean. Future work will investigate the possible connections between oceanic vertical motions and interannual variability (e.g., Southern Annular Mode), annual variability (e.g., Antarctic ozone hole), and anthropogenic effects (e.g., climate change).