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1. Southern Ocean Upwelling and the Marine Iron Cycle

   https://doi.org/10.1029/2020GL090737  

   Weber, Thomas ( October 2020 , Geophysical Research Letters)

   The iron (Fe) supply to phytoplankton communities in the Southern Ocean surface exerts a strong control on oceanic carbon storage and global climate. Hydrothermal vents are one potential Fe source to this region, but it is not known whether hydrothermal Fe persists in seawater long enough to reach the surface before it is removed by particle scavenging. A new study (Jenkins, 2020,https://doi.org/10.1029/2020GL087266) fills an important gap in this puzzle: a helium‐3 mass balance model is used to show that it takes ~100 yr for deep hydrothermally influenced waters to upwell to the surface around Antarctica. However, estimates of Fe scavenging time scales range from tens to hundreds of years and must be more narrowly constrained to fully resolve the role of hydrothermal Fe in the ocean's biological pump.

    

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2. The Influence of Ocean Topography on the Upwelling of Carbon in the Southern Ocean

   https://doi.org/10.1029/2021GL095088  

   Brady, Riley X. ; Maltrud, Mathew E. ; Wolfram, Phillip J. ; Drake, Henri F. ; Lovenduski, Nicole S. ( October 2021 , Geophysical Research Letters)

   The physical circulation of the Southern Ocean sets the surface concentration and thus air‐sea exchange of. However, we have a limited understanding of the three‐dimensional circulation that brings deep carbon‐rich waters to the surface. Here, we introduce and analyze a novel high‐resolution ocean model simulation with active biogeochemistry and online Lagrangian particle tracking. We focus our attention on a subset of particles with high dissolved inorganic carbon (DIC) that originate below 1,000 m and eventually upwell into the near‐surface layer (upper 200 m). We find that 71% of the DIC‐enriched water upwelling across 1,000 m is concentrated near topographic features, which occupy just 33% of the Antarctic Circumpolar Current. Once particles upwell to the near‐surface layer, they exhibit relatively uniformlevels and DIC decorrelation timescales, regardless of their origin. Our results show that Southern Ocean bathymetry plays a key role in delivering carbon‐rich waters to the surface.

    

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3. Using Excess 3 He to Estimate Southern Ocean Upwelling Time Scales

   https://doi.org/10.1029/2020GL087266  

   Jenkins, William J. ( August 2020 , Geophysical Research Letters)

   Using a recently compiled global marine data set of dissolved helium isotopes and helium and neon concentrations, we make an estimate of the inventory of hydrothermal³He in the Southern Ocean to be 4.9 ± 0.6 × 10⁴ moles. Under the assumption that the bulk of the hydrothermally sourced³He is upwelled there, we use recent estimates of the global hydrothermal³He flux to determine ane‐folding residence time of 99 ± 18 years, depending on assumptions of water mass and upwelling boundaries. Our estimate is within the broad range of values obtained from recent Southern Ocean circulation models.

    

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4. Dynamics of upwelling annual cycle in the equatorial Atlantic Ocean: Upwelling Annual Cycle

   https://doi.org/10.1002/2017GL072588  

   Wang, Li-Chiao ; Jin, Fei-Fei ; Wu, Chau-Ron ; Hsu, Huang-Hsiung ( April 2017 , Geophysical Research Letters)
5. Transformation and Upwelling of Bottom Water in Fracture Zone Valleys

   https://doi.org/10.1175/JPO-D-19-0021.1  

   Thurnherr, A. M. ; Clément, L. ; St. Laurent, L. ; Ferrari, R. ; Ijichi, T. ( March 2019 , Journal of Physical Oceanography)

   Abstract Closing the overturning circulation of bottom water requires abyssal transformation to lighter densities and upwelling. Where and how buoyancy is gained and water is transported upward remain topics of debate, not least because the available observations generally show downward-increasing turbulence levels in the abyss, apparently implying mean vertical turbulent buoyancy-flux divergence (densification). Here, we synthesize available observations indicating that bottom water is made less dense and upwelled in fracture zone valleys on the flanks of slow-spreading midocean ridges, which cover more than one-half of the seafloor area in some regions. The fracture zones are filled almost completely with water flowing up-valley and gaining buoyancy. Locally, valley water is transformed to lighter densities both in thin boundary layers that are in contact with the seafloor, where the buoyancy flux must vanish to match the no-flux boundary condition, and in thicker layers associated with downward-decreasing turbulence levels below interior maxima associated with hydraulic overflows and critical-layer interactions. Integrated across the valley, the turbulent buoyancy fluxes show maxima near the sidewall crests, consistent with net convergence below, with little sensitivity of this pattern to the vertical structure of the turbulence profiles, which implies that buoyancy flux convergence in the layers with downward-decreasing turbulence levels dominates over the divergence elsewhere, accounting for the net transformation to lighter densities in fracture zone valleys. We conclude that fracture zone topography likely exerts a controlling influence on the transformation and upwelling of bottom water in many areas of the global ocean. 

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