Biogeochemical properties of eddies in the California Current System

Chenillat, Fanny; Franks, Peter J. S.; Combes, Vincent

doi:10.1002/2016gl068945

Cited by 28 publications

(49 citation statements)

References 45 publications

(129 reference statements)

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“…Furthermore, a combination of the aforementioned perspectives is required in order to describe the properties of biogeochemical tracers averaged over multiple individual eddies. In this study, we aim to assess the nitrate transports resulted from mesoscale variability by applying Reynolds decomposition method (McGillicuddy et al, ; Nagai et al, ); then we focus on quantifying the overall effects of CEs and ACEs by using an eddy‐centric perspective (Castelao, ; Chenillat et al, ; Gaube et al, ; Gaube & McGillicuddy, ) based on daily samples extracted from a 25‐year simulation generated with a three‐dimensional physical‐biological coupled model of the GS region. Our methods are described in section 2. In section 3, the simulated mean state of the nutrients field over the study area is presented, followed by a description of the time‐dependent nutrient flux variations distributed in the horizontal and vertical directions.…”

Section: Introductionmentioning

confidence: 99%

Impacts of Mesoscale Eddies on the Vertical Nitrate Flux in the Gulf Stream Region

et al. 2018

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The Gulf Stream (GS) region has intense mesoscale variability that can affect the supply of nutrients to the euphotic zone (Zeu). In this study, a recently developed high‐resolution coupled physical‐biological model is used to conduct a 25‐year simulation in the Northwest Atlantic. The Reynolds decomposition method is applied to quantify the nitrate budget and shows that the mesoscale variability is important to the vertical nitrate supply over the GS region. The decomposition, however, cannot isolate eddy effects from those arising from other mesoscale phenomena. This limitation is addressed by analyzing a large sample of eddies detected and tracked from the 25‐year simulation. The eddy composite structures indicate that positive nitrate anomalies within Zeu exist in both cyclonic eddies (CEs) and anticyclonic eddies (ACEs) over the GS region, and are even more pronounced in the ACEs. Our analysis further indicates that positive nitrate anomalies mostly originate from enhanced vertical advective flux rather than vertical turbulent diffusion. The eddy‐wind interaction‐induced Ekman pumping is very likely the mechanism driving the enhanced vertical motions and vertical nitrate transport within ACEs. This study suggests that the ACEs in GS region may play an important role in modulating the oceanic biogeochemical properties by fueling local biomass production through the persistent supply of nitrate.

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Section: Introductionmentioning

confidence: 99%

Impacts of Mesoscale Eddies on the Vertical Nitrate Flux in the Gulf Stream Region

et al. 2018

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“…Despite the large number of studies and observations in the CCS and other EBUS, the ecological roles of coastal eddies in upwelling systems are poorly documented. Recent studies have shown that eddies in the CCS are responsible for the offshore transport of coastal, nutrient-rich water and the redistribution of biogeochemical components through advection and diffusion (Gruber et al 2011;Stramma et al 2013) reach similar conclusions in the Humboldt Current System; Chenillat et al 2016). However, the mechanisms of formation of such coastal eddies, and, perhaps, more importantly their capacity to trap and transport tracers, are poorly understood, mainly due to the difficulties of studying these features at sea.…”

Section: Introductionmentioning

confidence: 80%

“…From the kinematic analyses of eddy C01-2, we found that it (i) formed near shore, trapping shallow coastal waters from the northern CC and nutrient-rich coastal waters from the southern CUC, and (ii) traveled offshore for at least 6 months with limited exchange with surrounding waters. Mesoscale eddies, and in particular cyclonic eddies, are known to play a fundamental role in modulating the biology of upwelling systems (Moore et al 2007;Almazán-Becerril et al 2012;Stramma et al 2013;Chenillat et al 2015Chenillat et al , 2016. In-depth investigations of the effects of eddies on planktonic ecosystem dynamics were carried out for eddy C01-2 in Chenillat et al (2015).…”

Section: Biological Impactsmentioning

confidence: 99%

“…However, a significant fraction of that mesoscale activity is generated near shore (Marchesiello et al 2003;Chaigneau et al 2009) in response to wind forcing (Pares-Sierra et al 1993;Batteen 1997) and instabilities of boundary currents (Batteen et al 2003;Marchesiello et al 2003;Colas et al 2013) including interactions between topography and currents (Hickey 1998;Hickey et al 2003;Caldeira et al 2005;Dong et al 2009). Eddies are known to enhance biological activity, driving high chlorophyll-a concentrations, high zooplankton biomass, and intense sardine spawning (Hayward and Venrick 1998;Checkley et al 2000;Logerwell et al 2001;Almazán-Becerril et al 2012;Chenillat et al 2015Chenillat et al , 2016. This locally enhanced productivity is often transported far from its coastal origin.…”

Section: Introductionmentioning

confidence: 99%

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Eddy properties in the Southern California Current System

et al. 2018

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The California Current System (CCS) is an eastern boundary upwelling system characterized by strong eddies that are often generated at the coast. These eddies contribute to intense, long-distance cross-shelf transport of upwelled water with enhanced biological activity. However, the mechanisms of formation of such coastal eddies, and more importantly their capacity to trap and transport tracers, are poorly understood. Their unpredictability and strong dynamics leave us with an incomplete picture of the physical and biological processes at work, their effects on coastal export, lateral water exchange among eddies and their surrounding waters, and how long and how far these eddies remain coherent structures. Focusing our analysis on the southern part of the CCS, we find a predominance of cyclonic eddies, with a 25-km radius and a SSH amplitude of 6 cm. They are formed near shore and travel slightly northwest offshore for~190 days at~2 km day −1 . We then study one particular, representative cyclonic eddy using a combined Lagrangian and Eulerian numerical approach to characterize its kinematics. Formed near shore, this eddy trapped a core made up of~67% California Current waters and~33% California Undercurrent waters. This core was surrounded by other waters while the eddy detached from the coast, leaving the oldest waters at the eddy's core and the younger waters toward the edge. The eddy traveled several months as a coherent structure, with only limited lateral exchange within the eddy.

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“…With the ability to transport physical properties over long distances away from their formation region, nonlinear mesoscale eddies [ Chelton et al ., ] can presumably transport upwelled water as well as its chemical and biological properties [ Nagai et al ., ] with their westward drifts. Indeed, eddy‐induced transport of nutrients from the nearshore environment to the open ocean may result in reduced biological production in EBCS [ Gruber et al ., ], while maintaining locally elevated production in the eddies' interior [ Chenillat et al ., ]. Mesoscale eddies can also impact the spatial variability of SST through other mechanisms, including current‐induced and SST‐induced Ekman pumping [ Gaube et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Eddy‐induced sea surface temperature gradients in Eastern Boundary Current Systems

Yuan

Castelao

2017

JGR Oceans

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Many processes are known to influence the distribution of sea surface temperature (SST) fronts in Eastern Boundary Current Systems (EBCS), including wind forcing, mesoscale activity, flow instabilities, and flow‐topography interactions. Here we used satellite observations to quantify the relative importance of one of these processes, mesoscale eddy activity, on the distribution of SST gradients in EBCS. Eddies are characterized by large SST and SST gradient anomalies in all EBCS. At the end of the upwelling season, eddy‐induced SST gradients are dominant components of full SST gradients offshore of 300 km from the coast, especially in regions of high eddy activity. Comparisons between eddy‐induced and full SST gradients in the California Current System indicate that the offshore migration of mesoscale eddies plays a significant role on the seasonal widening of the region of high frontal activity. SST gradients associated with anticyclonic eddies are largest within 400 km from shore, while the signature of cyclones can extend for up to 700 km from the coast.

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Biogeochemical properties of eddies in the California Current System

Cited by 28 publications

References 45 publications

Impacts of Mesoscale Eddies on the Vertical Nitrate Flux in the Gulf Stream Region

Impacts of Mesoscale Eddies on the Vertical Nitrate Flux in the Gulf Stream Region

Eddy properties in the Southern California Current System

Eddy‐induced sea surface temperature gradients in Eastern Boundary Current Systems

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