Submesoscale winter bloom induced by Kuroshio-island interactions in the southern Luzon Strait
Yingzhi Xu¹, Hongyang Lin^1*, Bicheng Chen¹ & Zhiyu Liu¹
1. State Key Laboratory of Marine Environmental Science, Department of Physical Oceanography, College of Ocean and Earth Sciences, Xiamen University, China
Correspondence to: hylin@xmu.edu.cn

Abstract: The wintertime Kuroshio path tends to exhibit a more pronounced anticyclonic intrusion pattern than its summertime counterpart in the Luzon Strait, and hence has a higher probability to directly interact with islands within the strait. High-resolution satellite ocean color images indicate that phytoplankton blooms in forms of fronts or filaments are often observed in winter in the wakes of the Babuyan Islands (located in the south of the Luzon Strait). Diagnostic analysis based on high-resolution primitive-equation simulations in the study region suggests that the vigorous submesoscale instabilities caused by flow-topography interactions within the bottom boundary layer (BBL) play a crucial role in transporting the subsurface nutrients into the euphotic layer which leads to the observed winter bloom. More specifically, the topographic wake flows and filaments that separate from the BBL transport nutrient-rich water, which is sourced from the Cagayan River, across the Luzon Strait and thereby increase the phytoplankton productivity. Further analysis based on idealized large eddy simulations indicates that multi-scale instabilities may augment local kinetic energy dissipation and influence the distribution of chlorophyll. These process studies pave the way for better understanding of the winter blooming in the Luzon Strait.

Keywords: Luzon Strait; winter blooming; submesoscale instabilities; Kuroshio-island interactions

Luzon Strait, winter blooming, submesoscale instabilities, Kuroshio-island interactions