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Moored Observations of Transport and Variability of Halmahera Sea Currents
March 26,2020

Published in Journal of Physical Oceanography, February 2020

The ocean currents in the Halmahera Sea are studied using a subsurface mooring deployed in the Jailolo Strait from November 2015 to October 2017. The sub-tidal currents of the mooring measurements are characterized by a two-layer system, with the current variability below about 200 m in opposite phases to that in the upper layer. The mean along-strait velocity (ASV) is towards the Indonesian Seas in the whole water column, producing an estimated mean transport of 2.44 Sv ± 0.42 Sv (1 Sv = 106 m3s-1). The errors of the transport calculation based on the single mooring measurements are estimated to be less than 15% using simulations of high-resolution ocean models. A weak current is observed to flow northward during 2017 at the bottom of the strait. The ASV variability is found to be dominated by an annual cycle both in the upper and lower layers. The total transport, however, is dominated by semi-annual variability due to the cancelation of the annual transports in the upper and lower layers. The variability of the transport is suggested to be driven by the pressure difference between the Pacific and the Indonesian seas, as evidenced by the agreement between the satellite pressure gradient and the two-layer transports. The transport of the Jailolo Strait during the 2015-2016 super El Niño is found nearly the same as that during the 2016 La Niña, suggesting that the interannual variability of the transport are much smaller than the seasonal cycle.

Fig. 120-day low passed daily NCEP zonal and meridional winds (a), along-strait velocity (ASV) of the 2-year mooring measurements (b), and mean ASV profiles (c) in the Jailolo Strait of the Halmahera Sea. One standard deviation of the 2-year daily ASV is shown in dashed black curves.

This study is supported by NSFC (41421005, 41720104008, 91858204, and 41876025), CAS (XDA11010205), QMSNL (2018SDKJ0104-02), and the Shandong Provincial projects (U1606402).

Li X., Yuan D.*, Wang Z., Li Y., Corvianawatie C., Surinati D., Sandra A., Bayhaqi A., Avianto P., Kusmanto E., Dirhamsyah, Arifin Z. Moored observations of transport and variability of Halmahera Sea currents, Journal of Physical Oceanography, 2020, 50, 471-488. DOI: 10.1175/JPO-D-19-0109.1.

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