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- Title
A Strong Sub‐Thermocline Intrusion of the North Equatorial Subsurface Current Into the Makassar Strait in 2016–2017.
- Authors
Li, Mingting; Yuan, Dongliang; Gordon, Arnold L.; Gruenburg, Laura K.; Li, Xiang; Li, Rui; Yin, Xueli; Yang, Ya; Corvianatie, Corry; Wei, Jun; Yang, Song
- Abstract
The poorly resolved pathway of the sub‐thermocline waters (>300 m) within the Makassar Strait, the primary inflow path of the Indonesian Throughflow, is investigated using in situ mooring measurements and Argo profiles at the entrance to the Indonesian Seas. We focus on the strong sub‐thermocline intrusion in the summer of 2016, when significant changes of sub‐thermocline transport thrice as large as the interannual standard deviation occurred. Analysis suggests that the intrusion was drawn from the North Equatorial Subsurface Current (NESC) flowing westward below the North Equatorial Countercurrent, which was composed of a mixture of intermediate‐depth waters from both the North and South Pacific. The anomalously strong NESC to the Makassar sub‐thermocline in the summer 2016 is suggested to be in response to the 2015/2016 extreme El Niño event, forced by the trade wind anomalies over the western‐central Pacific Ocean through westward and downward propagating baroclinic Rossby waves. Plain Language Summary: The transfer of waters from the tropical Pacific to the Indian Ocean via the Indonesian Throughflow (ITF), the majority of which flows through the Makassar Strait, plays an important role in global ocean circulation and climate variations. Here, we identify the sources of the sub‐thermocline Makassar Strait waters by comparing their water mass properties in the Makassar Strait with those in the gateway region using ship‐based and Argo Conductivity‐Temperature‐Depth data. Traditional understanding of the ITF source water in the Makassar Strait is that it is drawn from the western boundary currents of the tropical Pacific Ocean. Our finding identifies a new zonal pathway for the equatorial waters entering the ITF in the sub‐thermocline layer (>300 m) in the summer of 2016, following the strong 2015/16 El Nino event. These results are anticipated to be the beginning of more comprehensive investigations of the Pacific‐Indian Ocean sub‐thermocline connection. Key Points: A strong sub‐thermocline intrusion into the Makassar Strait in summer 2016 is drawn from enhanced North Equatorial Subsurface Current (NESC)The sub‐thermocline water in the Makassar Strait is a mixture of intermediate‐depth waters from the North and the South Pacific OceanThe enhancement of the NESC after the extreme 2015/2016 El Niño, is forced by westward and downward propagating baroclinic Rossby waves
- Subjects
INTERNATIONAL Tennis Federation; PACIFIC Ocean currents; STRAITS; SOUTHERN oscillation; CLIMATE change; ROSSBY waves; TRADE winds; OCEAN circulation
- Publication
Geophysical Research Letters, 2021, Vol 48, Issue 8, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2021GL092505