Spatial structure and temporal variability of the zonal flow in the Luzon Strait

Abstract

One year long, full-depth velocity measurements were used to examine the spatial structure and temporal variability of the zonal flow in the Luzon Strait (LSZF). The observation revealed a renewed mean flow structure: in the upper (<500 m) and deep (>2000 m) layers, the LSZF was mostly westward; in the intermediate layer (500-2000 m), it was dominated by an eastward flow in the south but a westward flow in the north. The volume transport across the observed section between 19.8 N and 21.2 N exhibited strong seasonal and intraseasonal variability. On the seasonal time scale, the upper-layer transport showed a clear annual cycle, strongest in January and weakest in June; the intermediate-layer transport also showed a semiannual cycle, attaining its peaks (troughs) in January and June (April and October). On the intraseasonal time scale, both the upper-layer and intermediate-layer transports showed significant energy peaks at about 60 and 10-30 days. Further analysis indicated that the $60 day variability might be attributed to the impinging mesoscale eddies from the Pacific, while the 10-30 day variability appeared to obtain its energy from local intraseasonal wind forcing and baroclinic instability of the background current. The 10-100 day upper-layer and intermediate-layer transport variabilities were highly anticorrelated, suggesting a baroclinic nature of the intraseasonal variabilities of the LSZF.

Spatiotemporal Characteristics and Generation Mechanisms of Submesoscale Currents in the Northeastern South China Sea Revealed by Numerical Simulations

“…The large MSR here is not only attributed to Kuroshio‐islands interaction but also associated with the westward propagating mesoscale eddies from the open Pacific, which impinge on the Kuroshio and islands in the LS. As a result of the Kuroshio/eddies‐islands interactions, the MSR, and thus the SMI, does not have a significant seasonality but shows prominent intraseasonal variabilities with periods of 60–120 days (Zhang, Zhao, et al, ). Dynamically, growth of submesoscales in region LS is mainly through barotropic instability that extracts KE from the background current (i.e., the BT term).…”

The Linkage of Kuroshio Intrusion and Mesoscale Eddy Variability in the Northern South China Sea: Subsurface Speed Maximum

“…The Luzon Strait (LS) is the key ocean channel connecting the South China Sea (SCS) to the North Pacific (Figure 1a). LS transport advects the North Pacific signal into the SCS and then impacts the dynamic state of the SCS (Nan et al, 2015;Qu et al, 2000Qu et al, , 2005Qu et al, , 2006Qu et al, , 2009Zhang et al, 2015). LS transport, as a major component of the SCS throughflow (Qu et al, 2004(Qu et al, , 2005Wang et al, 2006), also modulates the thermodynamic state of the SCS (Xiao et al, 2018;Zeng et al, 2014Zeng et al, , 2016Zhao & Zhu, 2016) and plays an important role in the interannual variability of the Indonesian throughflow (Fang et al, 2003;Qu et al, 2009;.…”

“…Observations have revealed a "sandwich" vertical structure of LS transport; that is, the Kuroshio flows into the SCS in the upper (<500 m) and deep layers (>2,000 m) with outflow in the middle layer (Tian et al, 2006;Yang et al, 2010;Yuan et al, 2008Yuan et al, , 2009Zhang et al, 2015). There is a net westward vertically integrated LS transport, with estimates of the annual mean ranging from 0.5 to 6.5 Sv (Chu & Li, 2000;Liang et al, 2003;Qu et al, 2000).…”

Marine Group II Dominates Planktonic Archaea in Water Column of the Northeastern South China Sea

“…The water column dynamics of the SCS is regulated by complex basin topography and water circulations resulting from East Asian Monsoon activities and the Pacific Kuroshio current intrusion (Xu and Oey, 2015; Zhang Z. et al, 2015). Occurrence of surface-confined phototrophic populations in deep waters has been observed in the western Pacific, Luzon Strait, and the SCS, which may be attributed to the active vertical mixing and isopycnal heaving of water associated with internal solitary waves, mesoscale eddies, and/or other physical processes (Jiao et al, 2014b; Chen et al, 2016).…”