Seasonal and Interannual Variability of the Currents off the New Guinea Coast From Mooring Measurements
Linlin Zhang, Jie Wu, Fujun Wang, Shijian Hu, Qingye Wang, Fan Jia, Fan Wang, Dunxin Hu
Abstract
Abstract Seasonal and interannual variability of the New Guinea Coastal Current (NGCC) and New Guinea Coastal Undercurrent (NGCUC) were investigated with 3 years of mooring measurements off the northern coast of New Guinea and outputs from the Ocean General Circulation Model for the Earth Simulator during 1980–2018. Acoustic Doppler Current Profilers mounted on the two moorings captured variations of the currents in the upper 800 m off the New Guinea coast during 2015–2018. NGCC is a seasonally reversing current in the upper 100 m, which flows southeastward in boreal winter with maximum velocity of 63 cm/s near the surface, and flows northwestward in boreal summer with maximum velocity of −55 cm/s at 80 m. NGCUC flows northwestward all year round between 100 and 400 m, and its temporal mean velocity reaches −40 cm/s at 200 m. A seasonally reversing current named New Guinea Coastal Intermediate Current with speed of 10 cm/s is detected below the NGCUC, which is in phase with the NGCC on seasonal time scale. Seasonal variation of the NGCUC is also in phase with that of the NGCC, and it is strong in boreal summer and weak in winter. Such seasonal signal reaches down to the depth of 800 m. Both mooring measurements and model outputs indicate that NGCUC demonstrates significant interannual variations associated with El Nino‐Southern Oscillation (ENSO), with its velocity core shoaling during El Nino and deepening during La Nina, but the net transport of NGCUC exhibits no significant relationship with ENSO.