Abstract
The Mindanao Current (MC) bridges the North Pacific low-latitude western boundary current system region and the Indonesian Seas by supplying the North Pacific waters to the Indonesian Throughflow. Although the previous study speculated that the diapycnal mixing along the MC might be strong on the basis of the water mass analysis of the gridded climatologic dataset, the real spatial distribution of diapycnal mixing along the MC has remained to be clarified. We tackle this question here by applying a finescale parameterization to temperature and salinity profiles obtained using two rapid-sampling profiling Argo floats that drifted along the MC. The western boundary (WB) region close to the Mindanao Islands and the Sangihe Strait are the two mixing hotspots along the MC, with energy dissipation rate ε and diapycnal diffusivity Kρ enhanced up to ~ 10–6 W kg−1 and ~ 10–3 m2 s−1, respectively. Except for the above two mixing hotspots, the turbulent mixing along the MC is mostly weak, with ε and Kρ to be 10–11–10–9 W kg−1 and 10–6–10–5 m2 s−1, respectively. Strong mixing in the Sangihe Strait can be basically attributed to the existence of internal tides, whereas strong mixing in the WB region suggests the existence of internal lee waves. We also find that water mass transformation along the MC mainly occurs in the Sangihe Strait where the water masses are subjected to strong turbulent mixing during a long residence time.
Highlights
The Mindanao Current (MC) is an important part of the North Pacific low-latitude western boundary current system (NP-LLWBC; see Fig. 1)
The previous study speculated that the diapycnal mixing along the MC might be very strong based on the water mass analysis of the gridded climatologic dataset (Li and Wang 2012), the real spatial distribution of diapycnal mixing along the MC has long remained to be clarified
We have given the high-resolution spatial distribution of turbulent diapycnal mixing along the MC by applying strain-based finescale parameterization to the data measured by two rapid-sampling Argo floats that drifted along the MC’s routes
Summary
The Mindanao Current (MC) is an important part of the North Pacific low-latitude western boundary current system (NP-LLWBC; see Fig. 1). The MC bridges the NP-LLWBC region and the Indonesian Seas by supplying the North Pacific waters to the ITF (e.g., Hu et al 2015; Kashino et al 2001), and the water mass transformation along the MC can influence the properties of the ITF’s source waters. On the basis of the water mass analysis using the gridded climatologic data from World Ocean Database 2009 and Argo floats, Li and Wang (2012) speculated the significant decrease of the salinity of NPTW along the MC caused by the existence of enhanced turbulent mixing along the MC.
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