A case study of Chlorophyll a response to tropical cyclone Wind Pump considering Kuroshio invasion and air-sea heat exchange

Yupeng Liu; Danling Tang; Shilin Tang; Evgeny Morozov; Wenzhao Liang; Yi Sui

doi:10.1016/j.scitotenv.2020.140290

A case study of Chlorophyll a response to tropical cyclone Wind Pump considering Kuroshio invasion and air-sea heat exchange

Sci Total Environ. 2020 Nov 1:741:140290. doi: 10.1016/j.scitotenv.2020.140290. Epub 2020 Jun 18.

Authors

Yupeng Liu¹, Danling Tang², Shilin Tang³, Evgeny Morozov⁴, Wenzhao Liang⁵, Yi Sui⁶

Affiliations

¹ Guangdong Key Laboratory of Ocean Remote Sensing, State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences; Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, China; University of Chinese Academy of Sciences, Beijing, China. Electronic address: liuyupeng@scsio.ac.cn.
² Guangdong Key Laboratory of Ocean Remote Sensing, State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences; Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, China; University of Chinese Academy of Sciences, Beijing, China. Electronic address: lingzistdl@126.com.
³ Guangdong Key Laboratory of Ocean Remote Sensing, State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences; Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, China; University of Chinese Academy of Sciences, Beijing, China. Electronic address: sltang@scsio.ac.cn.
⁴ Marine Hydrophysical Institute, Russian Academy of Sciences, 299011 Sevastopol, Russia. Electronic address: frisman@list.ru.
⁵ Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China. Electronic address: liangwz@hku.hk.
⁶ Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada.

PMID: 32603939
DOI: 10.1016/j.scitotenv.2020.140290

Abstract

New evidences provided that the tropical cyclone (TC) Linfa in 2015 induced looping path of Kuroshio invasion into the northeastern South China Sea (NESCS) through the northwestern Luzon Strait (LS), based on the in-situ measurements, satellite data and model output data. This TC-enhanced Kuroshio invasion with low nutrients and denser waters suppressed the TC "Wind Pump" induced upwelling and nutrients uptake, and therefore inhibited the Chlorophyll a concentration (Chl-a) increase from surface to ~50 m in the open ocean of the NESCS. The TC-induced Kuroshio invasion promoted the generation of the strong cyclonic eddy to its left side where weak Ekman Pumping Velocity was observed. This enhancing cyclonic eddy then dominated the nutrients uplift and increased the surface and subsurface (0-50 m) Chl-a through eddy pumping rather than Ekman Pumping. The TC-declined anti-cyclonic eddy, which shoaled the Mixed Layer Depth (MLD), benefited to the nutrient uptake through TC-induced upwelling and thereby increased the surface Chl-a and raised the Chl-a Maximum Layer (CML) to ~20 m over the southwestern LS. The temporal Chl-a variations were also influenced by TC intensities and biochemical processes. The air-sea heat budget analysis indicated that, the air-sea heat exchange contributed to nearly 80% of the sea surface cooling (SST cooling) over the northwestern LS with Kuroshio invasion, while eddy-induced upwelling dominated the SST cooling over the western LS, and the wind-driven upwelling (and mixing) controlled the SST cooling over the southwestern LS. These different formations of SST cooling then played important role in Chl-a variations. This study is the first case of TC "Wind Pump" induced Chl-a variations considering air-sea heat exchange, Kuroshio invasion and mesoscale eddies over LS, which would help to evaluate the influence of TCs over the other major heat transport arteries of the world ocean: The Gulf Stream area.

Keywords: Chlorophyll a concentration; Heat flux; Kuroshio; Mesoscale eddy; Tropical cyclone; Wind Pump.