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Revisiting the Seasonal Cycle of the Timor Throughflow: Impacts of Winds, Waves and Eddies
Author(s) -
PeñaMolino Beatriz,
Sloyan Bernadette M.,
Nikurashin Maxim,
Richet Océane,
Wijffels Susan E.
Publication year - 2022
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1029/2021jc018133
Subject(s) - throughflow , thermocline , eddy , annual cycle , climatology , upwelling , monsoon , kelvin wave , ekman transport , forcing (mathematics) , oceanography , seasonality , geology , environmental science , la niña , atmospheric sciences , geography , meteorology , el niño southern oscillation , turbulence , statistics , mathematics , soil science
The tropical Pacific and Indian Oceans are connected via a complex system of currents known as the Indonesian Throughflow (ITF). More than 30% of the variability in the ITF is linked to the seasonal cycle, influenced by the Monsoon winds. Despite previous efforts, a detailed knowledge of the ITF response to the components of the seasonal forcing is still lacking. Here, we describe the seasonal cycle of the ITF based on new observations of velocity and properties in Timor Passage, satellite altimetry and a high‐resolution regional model. These new observations reveal a complex mean and seasonally varying flow field. The amplitude of the seasonal cycle in volume transport is approximately 6 Sv. The timing of the seasonal cycle, with semi‐annual maxima (minima) in May and December (February and September), is controlled by the flow below 600 m associated with semi‐annual Kelvin waves. The transport of thermocline waters (<300 m) is less variable than the deep flow but larger in magnitude. This top layer is modulated remotely by cycles of divergence in the Banda Sea, and locally through Ekman transport, coastal upwelling, and non‐linearities of the flow. The latter manifests through the formation of eddies that reduce the throughflow during the Southeast Monsoon, when is expected to be maximum. While the reduction in transport associated with the eddies is small, its impact on heat transport is large. These non‐linear dynamics develop over small scales (<10 km), and without high enough resolution, both observations and models will fail to capture them adequately.