Impacts of pre‐existing ocean cyclonic circulation on sea surface chlorophyll‐a concentrations off northeastern Taiwan following episodic typhoon passages

Abstract

Off northeastern Taiwan, enhancement of sea surface chlorophyll‐a (Chl‐a) concentration is frequently found after typhoon passages. From 1998 to 2013, 46 typhoon events are analyzed to examine the variations in Chl‐a concentration from satellite ocean color data. On average, Chl‐a concentration increased by 38% after a typhoon passage. Noticeably, four remarkable Chl‐a increases after typhoons coincide with pre‐existing oceanic cyclones in the study area. The Chl‐a increase is significantly anticorrelated (p < 0.01) with relative SSH, defined as the difference of SSH in the study area and in the surrounding area. To assess the impact of pre‐existing cyclones on the upper ocean response to typhoons, we conduct a series of numerical experiments to simulate the oceanic response to Typhoon Kaemi (2006) with or without a pre‐existing oceanic cyclone, and with or without strong typhoon winds. The results show that the experiment with a pre‐existing oceanic cyclone produces the largest upwelling due to cyclone intensification, mainly induced by the positive wind stress curl dipole northeast of Taiwan.

Upper ocean response to tropical cyclones: a review

“…There can be no subsurface warm anomaly in (b) if upwelling is strong enough. Salinity anomalies are similar to temperature anomalies plankton blooms depend not only on the TC characteristics but also on the ocean background conditions (Lin et al 2003b;Chen and Tang 2012;Shang et al 2015;Xu et al 2017a). For example, weak and slowmoving TCs induce phytoplankton blooms with higher chlorophyll-a concentrations, while strong and fastmoving TCs induce blooms over a larger area .…”

“…TCs induce phytoplankton blooms and primary production increase, which is mainly attributed to the increased nutrient supply in the euphotic zone induced by vertical mixing (or entrainment) and upwelling during a TC (Mooers 1975;Morimoto et al 2009;Siswanto et al 2009;Zheng et al 2010;Chiang et al 2011;Shibano et al 2011;Hung et al 2013;Huang and Oey 2015) and ocean restratification after the TC (Huang and Oey 2015;Lin and Oey 2016). The chlorophyll increases after a TC usually ranges from 5 to 91% (Babin et al 2004;Zhao et al 2017;Xu et al 2017a), while a lingered slow-moving TC (Kai-Tak in year 2000) can even triggered 30-fold of surface chlorophyll-a concentration (Lin et al 2003b). In Northern (Southern) Hemisphere, the chlorophyll increases usually biases to the right (left) side of the TC track (Lin et al 2003b;Babin et al 2004;Yin et al 2007;Hanshaw et al 2008;Shang et al 2008;Zheng et al 2010;Shibano et al 2011), although the rightward (leftward) bias is not obvious or may even occur towards the left (right) side of the TC track (Zheng et al 2010;Shibano et al 2011).…”

“…For example, weak and slowmoving TCs induce phytoplankton blooms with higher chlorophyll-a concentrations, while strong and fastmoving TCs induce blooms over a larger area . A pre-existing cold core eddy plays an important role in the increase in chlorophyll-a concentration by TCs (Chen and Tang 2012;Shang et al 2015;Xu et al 2017a;Jin et al 2020), and the concentration of pre-existing chlorophyll-a in cold core eddies is approximately 25-45% (8-25%) of that of the post-existing chlorophylla in cold core eddies for relatively high (low) TC transition speeds (Shang et al 2015). The biological response in coastal regions is more complicated than that in the open ocean (Pan et al 2017).…”

Observational Evidence of Subsurface Chlorophyll Response to Mesoscale Eddies in the North Pacific

“…Oceanic productivity is modulated by mesoscale eddies via nutrient fluxes into the euphotic zone in global oceans (Benitez-Nelson et al, 2007;Chelton et al, 2011a;Dufois et al, 2014;Dufois et al, 2016;Fong et al, 2008;Gaube et al, 2014;McGillicuddy, 2016;McGillicuddy et al, 1998;Xu et al, 2017). Eddy-induced nutrient supply was suggested to account for the "missing" nutrients in the subtropical gyre (Jenkins, 1988).…”

Introduction to Special Section on Oceanic Responses and Feedbacks to Tropical Cyclones

“…The special collection received more than 70 submissions and about 30 papers have been published so far. Papers included in this international special collection cover a broad topic of the ocean‐TC interactions, such as, but not limited to, the physical mechanism for ocean‐TC interactions, ocean‐TC interactions in the context of climate change, the data assimilation techniques and TC prediction using coupled models, and other related interdisciplinary studies such as coastal environments (Seroka et al, ; Shen et al, ), biochemical (Xu et al, ; Zhao et al, ), and geological (Lin et al, ) processes associated with TCs. This introduction is not a comprehensive review of recent progress in ocean‐TC interaction, but a brief introduction to some highlights in this special section.…”