The Pathways and Impacts of Indonesian Throughflow Heat Flux on the Eastern Tropical Indian Ocean
Abstract
A plume of low salinity water near 12°S, derived from the Indonesian Throughflow (ITF), spreads across the Indian Ocean within the South Equatorial Current (SEC), affecting regional heat and freshwater inventory. We examine the impact of the heat flux anomaly (HFa) within the primary pathway of the ITF, Makassar Strait, on the heat content (HCa) in the Eastern Tropical Indian Ocean (ETIO). Variability in the depth integrated volume transport, surface to 740 m, accounts for 57% of HFa variance. In addition, the ratio between the warm upper layer (0-300 m) and the cool lower layer (300-740 m) transport is variable and greatly affects the HFa. The importance of the vertical profile of transport is evident as the depth dependent velocity explains 97% of HFa variance. Changes within the temperature profile play a lesser role, explaining 38%. The mean upper layer temperature is 19.2 ± 6.1 ºC and the mean lower layer temperature is 7.7 ± 1.2 ºC. We determine the impact of Makassar HFa variability on the Indian Ocean through comparison with ETIO HCa computed from gridded Argo data. When lagged 30 months behind, ETIO HCa is well correlated (R=0.83) with Makassar HFa. Although generally following a similar pattern, a notable discrepancy between the two time series is present with a positive heat flux anomaly during 2010-12 in the Makassar absent from the ETIO box 2012-14. One explanation for this difference could be a divergent route for ITF waters once they exit into the Indian Ocean. A potential alternate pathway is investigated using 3 boxes within the region, an ITF box in the Timor Sea, the same ETIO box, and a Leeuwin Current box. The addition of normalized Leeuwin box HCa and ETIO box HCa results in an HCa time series that follows the same pattern as ITF box HCa. It is likely that the route of ITF waters within the eastern Indian Ocean is not constant and may vary between the zonal SEC pathway and a more southward Leeuwin pathway along the western margins of Australia.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMOS34A..07G
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 4522 ENSO;
- OCEANOGRAPHY: PHYSICALDE: 4532 General circulation;
- OCEANOGRAPHY: PHYSICALDE: 4576 Western boundary currents;
- OCEANOGRAPHY: PHYSICAL