Seasonal Variation in the Correlation Between Anomalies of Sea Level and Chlorophyll in the Antarctic Circumpolar Current

Song, Hajoon; Long, Matthew C.; Gaube, Peter; Frenger, Ivy; Marshall, Johh C.; McGillicuddy, Dennis J.

doi:10.1029/2017gl076246

Cited by 34 publications

(61 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition to supply of iron through dust deposition, sediment, and sea ice melt, vertical mixing is an important process since it entrains iron‐rich subsurface waters (Boyd & Ellwood, ; Tagliabue et al, ). In summer when light is abundant, satellite observations and eddy‐rich biogeochemical simulations show a positive correlation between anomalies of sea level and chlorophyll, suggesting that anomalously deep vertical mixing increases the iron supply and primary production (Song et al, ). Hence, increased stratification in the thermocline induced by current‐wind interaction may make entrainment of iron‐rich water more sporadic thus suppressing primary productivity.…”

Section: Discussionmentioning

confidence: 99%

Impact of Current‐Wind Interaction on Vertical Processes in the Southern Ocean

et al. 2020

Self Cite

View full text Add to dashboard Cite

Momentum input from westerly winds blowing over the Southern Ocean can be modulated by mesoscale surface currents and result in changes in large-scale ocean circulation. Here, using an eddy-resolving 1/20 degree ocean model configured near Drake Passage, we evaluate the impact of current-wind interaction on vertical processes. We find a reduction in momentum input from the wind, reduced eddy kinetic energy, and a modification of Ekman pumping rates. Wind stress curl resulting from current-wind interaction leads to net upward motion, while the nonlinear Ekman pumping term associated with horizontal gradients of relative vorticity induces net downward motion. The spatially averaged mixed layer depth estimated using a density criteria is shoaled slightly by current-wind interaction. Current-wind interaction, on the other hand, enhances the stratification in the thermocline below the mixed layer. Such changes have the potential to alter biogeochemical processes including nutrient supply, biological productivity, and air-sea carbon dioxide exchange. Plain Language Summary Momentum transfer between winds blowing over the SouthernOcean depends on the relative speed of the winds and surface currents. Mesoscale eddies with a scale of 100 km or less are very vigorous and thus can modulate momentum transfer. Here, we use an ocean model with sufficiently high horizontal resolution that it can resolve the mesoscale and hence capture the modulation. We find a reduction in the momentum transfer from the wind to the ocean and a reduction in eddy kinetic energy, together with a modification of wind-driven vertical motion. Structural changes in the wind stress field modify patterns of upwelling and downwelling in a manner that can be understood from nonlinear Ekman theory. Moreover, current-wind interaction results in an increase in the stratification below the mixed layer and hence a reduced communication between the surface and the interior ocean. There is thus a potential impact on biogeochemical processes and the climate of the Southern Ocean. Key Points: • High-resolution SouthernOcean simulations suggest that current-wind-stress interaction on the mesoscale reduces eddy kinetic energy by 25% • Current-wind interaction induces a net upward linear but downward nonlinear modulation of Ekman pumping rates • Current-wind interaction enhances stratification near the bottom of the mixed layer by up to 10% Supporting Information:• Supporting Information S1

show abstract

Section: Discussionmentioning

confidence: 99%

Impact of Current‐Wind Interaction on Vertical Processes in the Southern Ocean

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…In addition, primary production in the ocean is modulated by fluxes of nutrients and phytoplankton through the base of the mixed layer and the availability of light (Dawson et al, 2018;Frenger et al, 2018;Song et al, 2018). In addition, primary production in the ocean is modulated by fluxes of nutrients and phytoplankton through the base of the mixed layer and the availability of light (Dawson et al, 2018;Frenger et al, 2018;Song et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…The near-surface mixed layer is the conduit by which the atmosphere influences the ocean interior, and conversely, the ocean modulates fluxes into the atmosphere. In addition, primary production in the ocean is modulated by fluxes of nutrients and phytoplankton through the base of the mixed layer and the availability of light (Dawson et al, 2018;Frenger et al, 2018;Song et al, 2018). The fact that mesoscale eddies modulate the spatial and temporal evolution of the mixed layer has been known for decades (e.g., Klein et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the work of Hausmann et al (2017) revealed that the magnitude of eddy-mediated MLD perturbations were largest at the center of Southern Ocean eddies and decayed toward the eddy periphery. In the Southern Ocean this eddy-mediated MLD variability has been shown to generate enhanced iron flux in anticyclonic eddies (Song et al, 2018) that leads to elevated near-surface chlorophyll during the austral summer (Dawson et al, 2018;Frenger et al, 2018;Song et al, 2018). Using a global eddy-resolving simulation, 10.1029/2018GL080006 Dufois et al (2016) showed that during the winter, nutrients from below the mixed layer were entrained into the interiors of anticyclones at higher rates when compared to cyclones and the areas outside of the influence of eddies, leading the authors to suggest eddy-mediated MLD perturbations as a mechanism by which elevated near-surface chlorophyll concentrations could be sustained in anticyclones.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Mesoscale Eddies Modulate Mixed Layer Depth Globally

Gaube

McGillicuddy

Moulin

2019

Geophysical Research Letters

Self Cite

107

View full text Add to dashboard Cite

Mesoscale eddies, energetic vortices covering nearly a third of the ocean surface at any one time, modulate the spatial and temporal evolution of the mixed layer. We present a global analysis of concurrent satellite observations of mesoscale eddies with hydrographic profiles by autonomous Argo floats, revealing rich geographic and seasonal variability in the influence of eddies on mixed layer depth. Anticyclones deepen the mixed layer depth, whereas cyclones thin it, with the magnitude of these eddy‐induced mixed layer depth anomalies being largest in winter. Eddy‐centric composite averages reveal that the largest anomalies occur at the eddy center and decrease with distance from the center. Furthermore, the extent to which eddies modulate mixed layer depth is linearly related to the sea surface height amplitude of the eddies. Finally, large eddy‐mediated mixed layer depth anomalies are more common in anticyclones when compared to cyclones. We present candidate mechanisms for this observed asymmetry.

show abstract

“…There has, however, been comparatively limited investigation into how ocean dynamics, specifically eddies and fronts, transport iron from the ocean interior, where it is high in concentration, to the surface layer. Conventional focus on ocean dynamics has been on coastal processes (McGillicuddy et al, ; Mack et al, ; Jiang et al, ), mixed‐layer entrainment of iron due to wintertime cooling (Tagliabue et al, ; Llort et al, , ) and storms (Carranza & Gille, ; Nicholson et al, ), mesoscale isopycnal heaving (Swart et al, ; Song et al, , ), and lateral stirring (d’Ovidio et al, ; Ardyna et al, , ). To the best of our knowledge, Rosso et al (), Rosso et al () are the only studies that examine the effect of submesoscale dynamics on iron supply to the surface ocean in the open‐ocean region of Southern Ocean, but with the geographical coverage limited to the Kerguelen Plateau region and no consideration of the seasonal cycle.…”

Section: Introductionmentioning

confidence: 99%

The Contribution of Submesoscale over Mesoscale Eddy Iron Transport in the Open Southern Ocean

Uchida

Balwada

Abernathey

et al. 2019

J Adv Model Earth Syst

View full text Add to dashboard Cite

Biological productivity in the Southern Ocean is limited by iron availability. Previous studies of iron supply have focused on mixed-layer entrainment and diapycnal fluxes. However, the Southern Ocean is a region highly energetic mesoscale and submesoscale turbulence. Here we investigate the role of eddies in supplying iron to the euphotic zone, using a flat-bottom zonally re-entrant model, configured to represent the Antarctic Circumpolar Current region, that is coupled to a biogeochemical model with a realistic seasonal cycle. Eddies are admitted or suppressed by changing the model's horizontal resolution. We utilize cross spectral analysis and the generalized Omega equation to temporally and spatially decompose the vertical transport attributable to mesoscale and submesoscale motions. Our results suggest that the mesoscale vertical fluxes provide a first-order pathway for transporting iron across the mixing-layer base, where diapycnal mixing is weak, and must be included in modeling the open-Southern Ocean iron budget. Plain Language SummaryOcean currents at the surface on the spatial scales of 1-200 km are energetic due to heating by the sun and stirring by the winds. These currents contribute to the climate system by transporting heat and carbon horizontally towards the poles and vertically into the deep ocean. By running a numerical simulation at very high spatial resolution that resolve these currents, we show that these currents are also responsible for transporting iron from the ocean interior to the surface in the Southern Ocean, where phytoplankton growth is limited by the lack of iron-a key nutrient for most living organisms on Earth. Our results highlight the importance of accurately representing these ocean currents and associated iron transport, in order to understand the Southern Ocean ecosystem and its impact on the climate via photosynthesis, the process in which carbon dioxide is converted to organic carbon and oxygen is produced as a bi-product.

show abstract

Seasonal Variation in the Correlation Between Anomalies of Sea Level and Chlorophyll in the Antarctic Circumpolar Current

Cited by 34 publications

References 30 publications

Impact of Current‐Wind Interaction on Vertical Processes in the Southern Ocean

Impact of Current‐Wind Interaction on Vertical Processes in the Southern Ocean

Mesoscale Eddies Modulate Mixed Layer Depth Globally

The Contribution of Submesoscale over Mesoscale Eddy Iron Transport in the Open Southern Ocean

Contact Info

Product

Resources

About