Subthermocline eddies carrying the Indonesian Throughflow water observed in the southeastern tropical Indian Ocean

• Published in: Acta oceanologica Sinica Vol. 42; no. 5; pp. 1 - 13
• Main Authors: Yang, Guangbing, Zheng, Quanan, Xiong, Xuejun
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-05-2023; Springer Nature B.V; First Institute of Oceanography,and Key Laboratory of Marine Science and Numerical Modeling,Ministry of Natural Resources,Qingdao 266061,China; Shandong Key Laboratory of Marine Science and Numerical Modeling,Qingdao 266061,China%Department of Atmospheric and Oceanic Science,University of Maryland,College Park 20742,USA; Laboratory for Regional Oceanography and Numerical Modeling,Pilot National Laboratory for Marine Science and Technology(Qingdao),Qingdao 266237,China
• Subjects: Anomalies; Climatology; Coastal waters; Earth and Environmental Science; Earth Sciences; Ecology; Eddies; Engineering Fluid Dynamics; Environmental Chemistry; Indonesian Throughflow; Marine & Freshwater Sciences; Oceanography; Oceans; Rossby number; Salinity; Salinity effects; Subduction; Vortices; Water; Indian Ocean; southeastern tropical Indian Ocean; subthermocline eddy; submesoscale coherent vortex; Indonesian Throughflow
• ISSN: 0253-505X; 1869-1099
• DOI: 10.1007/s13131-022-2085-2

We observed a subthermocline eddy (STE) with a cold and fresh core during an observation cruise along a transect of 10°S in the southeastern tropical Indian Ocean (SETIO) in December 2017. The vertical scale, speed radius, and maximum swirl velocity of the STE were about 200 m, 55 km, and 0.5 m/s, respectively. The mean Rossby number and Burger number of the STE were then estimated to be about −0.7 and 2.4, indicating the STE was a submesoscale coherent vortex. The STE core water had characteristics of the Indonesian Throughflow (ITF) water and was distinct from that of surrounding areas. By examining Argo float data, another STE was well captured by five successive profiles of the same Argo float. Both STEs showed significant temperature and salinity anomalies at the
σ
0
=26.0–26.5 kg/m
3
surfaces. With the assumption that the low-salinity ITF water parcels could be carried only by surface eddies and the STEs, the Argo profiles, which detected low-salinity ITF water and were located outside a surface eddy, were believed to be inside an STE and were used to analyze the distribution, origin, and generation mechanism of the STE. The results suggested that the STEs carrying ITF water may be generated under topography-current interaction at the eastern coastal waters or under front-induced subduction in the area away from coastal waters. Those STEs may be widely distributed in the SETIO and may play a role in ITF water parcel transport.