Global impact of tropical cyclones on primary production

Abstract

International audienceIn this paper, we explore the global responses of surface temperature, chlorophyll, and primary production to tropical cyclones (TCs). Those ocean responses are first characterized from the statistical analysis of satellite data under ~1000 TCs over the 1998–2007 period. Besides the cold wake, the vast majority of TCs induce a weak chlorophyll response, with only ~10% of induced blooms exceeding 0.1 mg m<sup-3</sup>. The largest chlorophyll responses mostly occur within coastal regions, in contrast to the strongest cold wakes that generally occur farther offshore. To understand this decoupling, we analyze a coupled dynamical-biogeochemical oceanic simulation forced by realistic wind vortices applied along observed TC tracks. The simulation displays a realistic spatial structure of TC-induced blooms and its observed decoupling with TC cold wakes. In regions of strong TC energy input, the strongest cold wakes occur in regions of shallow thermocline (<60 m) and the strongest blooms in regions of shallow nitracline and/or subsurface chlorophyll maximum (<60 m). Shallow thermoclines are found over many open ocean regions, while regions of shallow nitracline and/or subsurface chlorophyll maximum are most prominent in near-coastal areas, explaining the spatial decoupling between the cold and bloom wakes. The overall TC contribution to annual primary production is weak and amounts to ~1%, except in a few limited areas (east Eurasian coast, South tropical Indian Ocean, Northern Australian coast, and Eastern Pacific Ocean in the TC-prone region) where it can locally reach up to 20–30%. Nearly 80% of this TC-induced annual primary production is the result of the biogeochemical response to the 30% strongest TCs

The impact of hurricanes on the oceanographic conditions in the Exclusive Economic Zone of Cuba

“…The SST cooling induced by rains might have been observed during the days before the hurricane passage given the high DAP anomalies at this time ( Figure 3B). Yet, though it has been reported that SST starts to decrease at day -3 (Vincent et al, 2012b;Menkes et al, 2016), we found that this occurred only from the day 0 on ( Figure 3C). Thus, the DAP effects did not seem to have been sufficient to cool the waters of the EEZ.…”

“…In previous studies of other regions, researchers considered different spatial scales to assess the TCinduced oceanographic variability. For example, Babin et al (2004) constructed cells of 0.5 • latitude north and south and 1 • longitude west and 2 • longitude east for each hurricane track point analysed, while other authors have used 200 km radius disks centered at the consecutive TC positions (Menkes et al, 2016;Shropshire et al, 2016) and square areas of different sizes located at variable distances from the TC trajectory (Wang and Zhao, 2008;Merritt-Takeuchi and Chiao, 2013). On the other hand, Son et al (2007) and Farfán et al (2014) analysed a band of 700 km and 15 km wide, respectively, centered on storm tracks, while Foltz et al (2015) and Parker et al (2017) assessed TC activity across a large region of the Western Subtropical North Atlantic and the Great Barrier Reef of Australia, respectively.…”

“…The used product is a set of objectively analysed (1 • × 1 • ) climatological fields of in situ nitrate concentration at standard depths for monthly composite periods (https://www.nodc.noaa.gov/OC5/woa13/ ). We estimated DNO 3 following the procedure in Menkes et al (2016), i.e., by identifying the depth where the concentration of NO 3 becomes higher than 1 µM and DNO 3 is set to zero if surface NO 3 concentration exceeds this threshold. The depth of the deep chlorophyll maximum (DCM) is also an important factor contributing to the chl-a increase after the TC passage (Menkes et al, 2016), but we did not include it in our analysis since only a limited number of chl-a profiles from the World Ocean Atlas Database were available for the EEZ of Cuba and also they only extended to depths of 100 m.…”

Phytoplankton Responses to Climate‐Induced Warming and Interdecadal Oscillation in North‐Western Australia

“…Phytoplankton living in tropical oligotrophic water is sensitive to nutrient enhancement (Cloern & Jassby, ). Modeling results suggested that the tropical cyclone‐induced phytoplankton blooms in north‐western Australia could contribute to 20% of annual primary production (Menkes et al, ). The shift changes of diatoms and dinoflagellates in the three locations were asynchronous after the 1970s, which might be related to their different geographic and hydrologic conditions.…”

Globally consistent impact of tropical cyclones on the structure of tropical and subtropical forests

“…For each grid cell with a spatial resolution of 1° latitude × 1° longitude (≈12,345 km 2 at the equator, Figure 1), the energy released by TCs was computed as the power dissipated by friction in the surface layer (Emanuel, 2005) following Menkes et al (2016) and . At each point, the maximum 10-min sustained wind speeds at 10 m above the ground (V) was extracted from the database.…”