Abyssal Circulation in the Philippine Sea

更新时间:2023-05-28

【摘要】The abyssal circulation in the Philippine Sea(PS) is investigated, with outputs from the Simple Ocean Data Assimilation version 2.2.4(SODA224). The deep-water currents in SODA224 are carefully evaluated, with sparse in situ observations in the North Pacific Ocean. In the upper deep layer(2000–3000 m) of the PS, a strong westward current, which originates from the Northeast Pacific Basin and enters the PS through the Yap-Mariana Junction, exists along 11?–14?N. This strong westward current bifurcates into two western boundary currents off the Philippines. The northward-flowing current flows out of the PS around 20?–21?N, whereas the southward-flowing current transports deep water from the northern hemisphere to the southern hemisphere. In the lower deep layer(3000 – 4500 m), the inflow water first flows northward to the east of the Western Mariana Basin and then turns westward at approximately 18?N. The inflow water mainly enters the Philippine Basin(PB), with a small part turning southward to constitute a weak cyclonic circulation. The water entering the PB mainly merges into a strong southward western boundary current in the southern PB. In the bottom layer(below 4500 m), both the northeast and northwest PB show single cyclonic gyres, whereas the south PB shows a single anticyclonic gyre. Moreover, comparisons with the observations indicate the possible existence of a cyclonic sense of circulation over the Philippine Trench. The current study provides the implications for future observations, which are needed to further investigate the temporospatial variations of the abyssal circulation in the PS on multiple scales.

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