Anticyclonic eddies are more productive than cyclonic eddies in subtropical gyres because of winter mixing

Dufois, François; Hardman-Mountford, Nick J.; Greenwood, Jim; Richardson, Anthony J.; Feng, Ming; Matear, Richard J.

doi:10.1126/sciadv.1600282

Cited by 150 publications

(186 citation statements)

References 32 publications

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“…the MLD and Chl-a seasonal climatology dynamics (Figure 4) suggest the MLD could be a key environmental driver of differences in Chl-a between these two environments. The importance of MLD deepening to Chl-a seasonality in subtropical water is consistent with a recent study of Chl-a variability in eddies of the Indian Ocean (Dufois et al, 2016).…”

Section: Discussion the Role Of Mixed Layer Depth And Light On Phytopsupporting

confidence: 71%

“…Indeed, the seasonal deepening of the MLD can bring nutrient-rich water from depth into the euphotic zone but decrease the total photon flux to cells. Due to the differing nutrient requirements of phytoplankton, the water mass below the MLD could therefore play an important role in determining eddy phytoplankton concentration and composition (Bibby and Moore, 2011;Dufois et al, 2016). Furthermore, the shallower MLD that characterizes CE leads to higher light levels in the surface mixed layer, while ACE have lower light levels (Tilburg et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

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Key Drivers of Seasonal Plankton Dynamics in Cyclonic and Anticyclonic Eddies off East Australia

et al. 2016

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Mesoscale eddies in the south west Pacific region are prominent ocean features that represent distinctive environments for phytoplankton. Here, we examine the seasonal plankton dynamics associated with averaged cyclonic and anticyclonic eddies (CE and ACE, respectively) off eastern Australia. We do this through building seasonal climatologies of mixed layer depth (MLD) and surface chlorophyll-a for both CE and ACE by combining remotely sensed sea surface height (TOPEX/Poseidon, Envisat, Jason-1, and OSTM/Jason-2), remotely sensed ocean color (GlobColour) and in situ profiles of temperature, salinity and pressure from Argo floats. Using the CE and ACE seasonal climatologies, we assimilate the surface chlorophyll-a data into both a single (WOMBAT), and multi-phytoplankton class (EMS) biogeochemical model to investigate the level of complexity required to simulate the phytoplankton chlorophyll-a. For the two eddy types, the data assimilation showed both biogeochemical models only needed one set of parameters to represent phytoplankton but needed different parameters for zooplankton. To assess the simulated phytoplankton behavior we compared EMS model simulations with a ship-based experiment that involved incubating a winter phytoplankton community sampled from below the mixed layer under ambient and two higher light intensities with and without nutrient enrichment. By the end of the 5-day field experiment, large diatom abundance was four times greater in all treatments compared to the initial community, with a corresponding decline in pico-cyanobacteria. The experimental results were consistent with the simulated behavior in CE and ACE, where the seasonal deepening of the mixed layer during winter produced a rapid increase in large phytoplankton. Our model simulations suggest that CE off East Australia are not only characterized by a higher chlorophyll-a concentration compared to ACE, but also by a higher concentration of large phytoplankton (i.e., diatoms) due to the shallower CE mixed layer. The model simulations also suggest the zooplankton community is different in the two eddy types and this behavior needs further investigation.

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Section: Discussion the Role Of Mixed Layer Depth And Light On Phytopsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Key Drivers of Seasonal Plankton Dynamics in Cyclonic and Anticyclonic Eddies off East Australia

et al. 2016

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“…However, to be able to construct a standard scale based on the eddy radius of each eddy, we normalized the Chl-a fields by twice the radius (2R) in each case [8,22,73]. Then, we ensured that during the tracking period of eddies, the size-fractionated Chl-a fields covered at least 50% of their spatial extension, screening out the periods (weeks) when this was not achieved.…”

Section: Size-fractionated Chlorophyll-a Satellite Estimates In Mesosmentioning

confidence: 99%

Phytoplankton Size Structure in Association with Mesoscale Eddies off Central-Southern Chile: The Satellite Application of a Phytoplankton Size-Class Model

et al. 2018

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Understanding the influence of mesoscale and submesoscale features on the structure of phytoplankton is a key aspect in the assessment of their influence on marine biogeochemical cycling and cross-shore exchanges of plankton in Eastern Boundary Current Systems (EBCS). In this study, the spatio-temporal evolution of phytoplankton size classes (PSC) in surface waters associated with mesoscale eddies in the EBCS off central-southern Chile was analyzed. Chlorophyll-a (Chl-a) size-fractionated filtration (SFF) data from in situ samplings in coastal and coastal transition waters were used to tune a three-component (micro-, nano-, and pico-phytoplankton) model, which was then applied to total Chl-a satellite data (ESA OC-CCI product) in order to retrieve the Chl-a concentration of each PSC. A sea surface, height-based eddy-tracking algorithm was used to identify and track one cyclonic (sC) and three anticyclonic (ssAC1, ssAC2, sAC) mesoscale eddies between January 2014 and October 2015. Satellite estimates of PSC and in situ SFF Chl-a data were highly correlated (0.64 < r < 0.87), although uncertainty values for the microplankton fraction were moderate to high (50 to 100% depending on the metric used). The largest changes in size structure took place during the early life of eddies (~2 months), and no major differences in PSC between eddy center and periphery were found. The contribution of the microplankton fraction was~50% (~30%) in sC and ssAC1 (ssAC2 and sAC) eddies when they were located close to the coast, while nanoplankton was dominant (~60-70%) and picoplankton almost constant (<20%) throughout the lifetime of eddies. These results suggest that the three-component model, which has been mostly applied in oceanic waters, is also applicable to highly productive coastal upwelling systems. Additionally, the PSC changes within mesoscale eddies obtained by this satellite approach are in agreement with results on phytoplankton size distribution

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“…Anticyclones/cyclones deepen/shoal isopycnals and the nutricline, resulting in less/more available nutrients. However deeper/shallower mixed layers in anticyclones/cyclones can provide more/less nutrients to the surface [Kunze, 1985;Kunze et al, 1995;Koszalka et al, 2010;Song et al, 2015;Dufois et al, 2016].…”

Section: Introductionmentioning

confidence: 99%

Mesoscale modulation of air‐sea CO₂ flux in Drake Passage

et al. 2016

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We investigate the role of mesoscale eddies in modulating air‐sea CO2 flux and associated biogeochemical fields in Drake Passage using in situ observations and an eddy‐resolving numerical model. Both observations and model show a negative correlation between temperature and partial pressure of CO2 (pCO2) anomalies at the sea surface in austral summer, indicating that warm/cold anticyclonic/cyclonic eddies take up more/less CO2. In austral winter, in contrast, relationships are reversed: warm/cold anticyclonic/cyclonic eddies are characterized by a positive/negative pCO2 anomaly and more/less CO2 outgassing. It is argued that DIC‐driven effects on pCO2 are greater than temperature effects in austral summer, leading to a negative correlation. In austral winter, however, the reverse is true. An eddy‐centric analysis of the model solution reveals that nitrate and iron respond differently to the same vertical mixing: vertical mixing has a greater impact on iron because its normalized vertical gradient at the base of the surface mixed layer is an order of magnitude greater than that of nitrate.

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Anticyclonic eddies are more productive than cyclonic eddies in subtropical gyres because of winter mixing

Abstract: In subtropical ocean gyres, anticyclonic eddies increase surface nutrient injection and primary production during winter.

Cited by 150 publications

References 32 publications

Key Drivers of Seasonal Plankton Dynamics in Cyclonic and Anticyclonic Eddies off East Australia

Key Drivers of Seasonal Plankton Dynamics in Cyclonic and Anticyclonic Eddies off East Australia

Phytoplankton Size Structure in Association with Mesoscale Eddies off Central-Southern Chile: The Satellite Application of a Phytoplankton Size-Class Model

Mesoscale modulation of air‐sea CO₂ flux in Drake Passage

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Anticyclonic eddies are more productive than cyclonic eddies in subtropical gyres because of winter mixing

Abstract: In subtropical ocean gyres, anticyclonic eddies increase surface nutrient injection and primary production during winter.

Cited by 150 publications

References 32 publications

Key Drivers of Seasonal Plankton Dynamics in Cyclonic and Anticyclonic Eddies off East Australia

Key Drivers of Seasonal Plankton Dynamics in Cyclonic and Anticyclonic Eddies off East Australia

Phytoplankton Size Structure in Association with Mesoscale Eddies off Central-Southern Chile: The Satellite Application of a Phytoplankton Size-Class Model

Mesoscale modulation of air‐sea CO2 flux in Drake Passage

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Product

Resources

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Mesoscale modulation of air‐sea CO₂ flux in Drake Passage