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New unified interface for existing ocean carbonate chemistry data products

Posted by mmaheigan

· Tuesday, March 24th, 2026

The paper provides a comprehensive synthesis of 68 existing ocean carbonate chemistry data products and data product sets, including cruise-based compilations, time-series datasets, gap-filled observational products, and model-based reconstructions. The authors highlight the diversity of available products, noting differences in spatial coverage, temporal resolution, methodologies, and intended scientific applications. By systematically cataloguing and comparing these datasets, the study helps researchers identify which products are most suitable for specific scientific questions related to ocean carbon cycling and ocean acidification.

ESSD Paper

Interface for the most updated list of products

Submission interface

Authors
Li-Qing Jiang (University of Maryland; NOAA National Centers for Environmental Information; Scripps Institution of Oceanography)
Amanda Fay (Columbia University / Lamont-Doherty Earth Observatory)
Jens Daniel Müller (ETH Zürich; Carbon to Sea Initiative)
Luke Gregor (ETH Zürich; Swiss Data Science Center)
Alizée Roobaert (Flanders Marine Institute, VLIZ)
Lydia Keppler (Vycarb Inc.)
Dustin Carroll (Moss Landing Marine Laboratories; NASA Jet Propulsion Laboratory)
Siv K. Lauvset (NORCE Research / Bjerknes Centre for Climate Research)
Tim DeVries (University of California, Santa Barbara)
Judith Hauck (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research)
Christian Rödenbeck (Max Planck Institute for Biogeochemistry)
Nicolas Metzl (Sorbonne Université / LOCEAN)
Andrea J. Fassbender (NOAA Pacific Marine Environmental Laboratory)
Jean-Pierre Gattuso (Sorbonne Université / CNRS; Laboratoire d’Océanographie de Villefranche)
Peter Landschützer (Max Planck Institute for Meteorology)
Rik Wanninkhof (NOAA Atlantic Oceanographic and Meteorological Laboratory)
Christopher Sabine (University of Hawaii at Mānoa)
Simone R. Alin (NOAA Pacific Marine Environmental Laboratory)
Mario Hoppema (Alfred Wegener Institute)
Are Olsen (University of Bergen / Bjerknes Centre for Climate Research)
Matthew P. Humphreys (University of East Anglia)
Kunal Chakraborty (National Institute of Oceanography, India)
Ana C. Franco (University of Miami)
Kumiko Azetsu-Scott (Bedford Institute of Oceanography / Fisheries and Oceans Canada)
Dorothee C. E. Bakker (University of East Anglia)
Leticia Barbero (NOAA Atlantic Oceanographic and Meteorological Laboratory)
Nicholas R. Bates (Bermuda Institute of Ocean Sciences / Arizona State University)
Nicole Besemer (University of Natural Resources and Life Sciences Vienna)
Henry C. Bittig (GEOMAR Helmholtz Centre for Ocean Research Kiel)
Albert E. Boyd (University of Tasmania)
Daniel Broullón (Spanish Institute of Oceanography, IEO-CSIC)
Wei-Jun Cai (University of Delaware)
Brendan R. Carter (University of Washington)
Thi-Tuyet-Trang Chau (LSCE, CEA-CNRS-UVSQ)
Chen-Tung Arthur Chen (National Sun Yat-sen University)
Frédéric Cyr (Fisheries and Oceans Canada)
John E. Dore (University of Hawaii)
Ian Enochs (NOAA Atlantic Oceanographic and Meteorological Laboratory)
Richard A. Feely (NOAA Pacific Marine Environmental Laboratory)
Hernan E. Garcia (NOAA National Centers for Environmental Information)
Marion Gehlen (LSCE, CEA-CNRS-UVSQ)
Prasanna Kanti Ghoshal (CSIR-National Institute of Oceanography, India)
Lucas Gloege (Princeton University)
Melchor González-Dávila (University of Las Palmas de Gran Canaria)
Nicolas Gruber (ETH Zürich)
Debby Ianson (Fisheries and Oceans Canada / Institute of Ocean Sciences)
Yosuke Iida (Japan Meteorological Agency)
Masao Ishii (Meteorological Research Institute, Japan)
Apurva Padamnabh Joshi (CSIR-National Institute of Oceanography, India)
Esther Kennedy (NOAA Pacific Marine Environmental Laboratory)
Alex Kozyr (NOAA National Centers for Environmental Information)
Nico Lange (GEOMAR Helmholtz Centre for Ocean Research Kiel)
Claire Lo Monaco (Sorbonne Université / LOCEAN)
Derek P. Manzello (NOAA Atlantic Oceanographic and Meteorological Laboratory)
Galen A. McKinley (Columbia University / Lamont-Doherty Earth Observatory)
Natalie M. Monacci (NOAA Pacific Marine Environmental Laboratory)
Xosé A. Padin (Spanish Institute of Oceanography, IEO-CSIC)
Ana M. Palacio-Castro (Instituto de Investigaciones Marinas, CSIC)
Fiz F. Pérez (Spanish Institute of Oceanography, IEO-CSIC)
J. Magdalena Santana-Casiano (University of Las Palmas de Gran Canaria)
Jonathan Sharp (University of Delaware)
Adrienne Sutton (NOAA Pacific Marine Environmental Laboratory)
Jim Swift (Scripps Institution of Oceanography)
Toste Tanhua (GEOMAR Helmholtz Centre for Ocean Research Kiel)
Maciej Telszewski (International Ocean Carbon Coordination Project, IOCCP)
Jens Terhaar (University of Bern)
Ruben van Hooidonk (University of Miami / NOAA Coral Reef Watch)
Anton Velo (Spanish Institute of Oceanography, IEO-CSIC)
Andrew J. Watson (University of Exeter)
Angelicque E. White (Oregon State University)
Zelun Wu (University of Delaware)
Liang Xue (Xiamen University)
Hyelim Yoo (University of Maryland / NOAA NCEI)
Jiye Zeng (National Institute for Environmental Studies, Japan)
Guorong Zhong (Xiamen University)

How much carbon do fish move towards the seafloor as they feed and migrate in the water column?

Posted by mmaheigan

· Tuesday, March 24th, 2026

Ocean organisms transfer carbon via many natural processes from surface to seafloor. These include the passive sinking of carbon-rich particles and the active transport of carbon as animals swim downward. A recent study in GBC modeled how carbon stored in fish biomass moves from the sea surface to the seafloor in shelf–slope–abyssal systems through feeding interactions alone. This transport occurs as large fish eat smaller fish while occupying different vertical habitats in the water column. On average, this process delivers an amount equivalent to 5% of all carbon that reaches the seafloor—through sinking organic particles from phytoplankton and zooplankton. Yet, this can be as high as 20% in some shelf areas. On continental slopes, midwater fishes play a key role as a stepping-stone for carbon transfer (up to 50%) to the seafloor. Overall, the study reveals that the vertical movement of fish is an important pathway for delivering carbon to groundfish species, particularly on shelf areas where most commercially valuable fisheries operate.

Caption: Schematic of a shelf-slope-abyssal system with hypothesized fluxes of carbon among major functional groups (top panel); and model-estimated fluxes of carbon from functional groups to demersal fishes (bottom panel). Solid and dotted lines are mean fluxes for Eastern and Western North Atlantic systems, respectively, and shaded areas are standard deviations. Values are proportional.

Authors

Daniel Ottmann (Technical University of Denmark (DTU-Aqua); Institute of Marine Sciences of Andalusia)
Ken H. Andersen (Technical University of Denmark (DTU-Aqua))
Yixin Zhao (Technical University of Denmark (DTU-Aqua))
Colleen M. Petrik (Scripps Institution of Oceanography)
Charles A. Stock (Scripps Institution of Oceanography)
Clive Trueman (University of Southampton)
P. Daniël van Denderen (Technical University of Denmark (DTU-Aqua))

Follow the authors:
bluesky: @danielottmann.bsky.social; @kenandersen.bsky.social
LinkedIn accounts: Ottman; Andersen; Truman
X: @daniel_ottmann; @69kno; @OceanLifeCenter; @van_denderen; @clivetrue;

Active Transport of Carbon to Demersal Fish Communities in Shelf-Slope-Abyssal Systems of the North Atlantic Ocean
Global Biogeochemical Cycles, Vol 40:2, e2025GB008861. https://doi.org/10.1029/2025GB008861

The ocean is the largest natural carbon sink for atmospheric CO2

Posted by mmaheigan

· Friday, January 23rd, 2026

Only about half of human-made CO2 emissions remain in the atmosphere and drive global warming. The other half has so far been said to be taken up in roughly equal amounts by the biosphere on land and by physical-chemical processes in the ocean. In equal amounts?

In a new assessment, Friedlingstein et al. reassess the various components of the Global Carbon Budget. Major changes were suggested for the land and ocean sinks. For the land, the prior assumption of a preindustrial land-cover in the Dynamic Global Vegetation Models (DGVM) led to an overestimation of the natural land sink in previous studies. The land sink is further revised downwards by accounting for an anthropogenic perturbation of lateral carbon export to the ocean. For the ocean, adjustments were made for the known underestimation of the ocean sink from Global Ocean Biogeochemical Models and the cool and salty skin effect in surface fCO₂-observation-based estimates. As a result, the ocean is now estimated to have taken up 29% of anthropogenic CO₂ emissions in the last decade 2015-2024, while the land sink has taken up 21%. In this revised estimate with virtually no budget imbalance over the last decade and no significant trend in the budget imbalance since 1960, climate-driven impacts on the natural sinks are quantified: Land and ocean sinks would be 25% and 7% higher, respectively, without this carbon-climate feedback. Since 1960, the carbon-climate feedback has already contributed 8 ppm (8%) to the rise in atmospheric CO₂ concentration.

The negative imprints of earth system changes (e.g., warming, droughts, changes in wind patterns and ocean circulation, etc.) on these important carbon sinks is worrisome and is expected to intensify as warming continues. The most effective way to protect these sinks is to drastically reduce CO₂ emissions from fossil fuels and land-use changes, ultimately to net zero.

Authors
Judith Hauck (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, University of Bremen)
Peter Landschützer (VLIZ)
Corinne Le Quéré (University of East Anglia)
Pierre Friedlingstein (University of Exeter)

Bluesky: @pfriedling @jhauck @clequere

New software enables global ocean biogeochemical modeling in Python

Posted by mmaheigan

· Friday, September 5th, 2025

Have you ever wondered what life would be like if you could write and run complex biogeochemical models easily and conveniently in Python? Wonder no more. In a paper published in J. Adv. Model. Earth Syst., Samar Khatiwala (2025; see reference below) describes tmm4py, a new software to enable efficient, global scale biogeochemical modelling in Python.

tmm4py is based on the Transport Matrix Method (TMM), an efficient numerical scheme for “offline” simulation of tracers driven by circulations from state-of-the-art physical models and state estimates. tmm4py exposes this functionality in Python, providing the tools needed to implement complex models in pure Python using standard modules such as NumPy, and run them interactively on hardware ranging from laptops to supercomputers. No knowledge of parallel computing required! tmm4py even extends the interactivity to models written in Fortran, allowing the many existing models coupled to the TMM, e.g., MITgcm, to be used from the familiar comfort of Python. Whether you’re a seasoned modeler, just want to try out an idea, or illustrate a concept in your teaching, tmm4py is designed to make biogeochemical modeling more widely accessible.

Download the code from: https://github.com/samarkhatiwala/tmm

Figure: Schematic illustrating the structure of tmm4py and its relationship with the various libraries and components it is built on or interacts with. Outlined boxes represent user‐supplied code (such as the “Hello World” example of the ideal age tracer shown on the left). Other low-level libraries on which tmm4py depends, for example, BLAS and LAPACK for linear algebra, MPI for parallel communication, and CUDA for GPUs, are not shown.

Author
Samar Khatiwala (Waseda Univ)

Joint Science Highlight with GEOTRACES.

Photoacclimation by phytoplankton under clouds

Posted by mmaheigan

· Thursday, May 29th, 2025

Unlike most remote sensing products, Net Primary Production (NPP) is computed under clouds. Since satellites can’t see through clouds, NPP models rely on clear-sky observations, interpolate model inputs, and assume that phytoplankton behavior stays the same, regardless of light conditions.

Figure caption: (a) Schematic of the photoacclimation process. In yellow, a standard photoacclimation curve where θ (the chlorophyll to phytoplankton carbon ratio), adjusts as a function of light in the mixed layer (Eg). In blue, the schematic when we do not consider photoacclimation under cloud: Eg is reduced due to cloud-cover, but θ remains the same as it was under cloud, resulting in a strongly reduced μ (a proxy for growth rate). When considering photoacclimation under clouds (red), θ increases because of a reduced Eg, resulting in a μcloudy(photo) > μcloudy(no photo). (b) Histogram of the distribution of θ*Eg (a proxy for growth rate) from BGC-Argo floats separated by whether under cloudy (red) or clear (yellow) skies.

But phytoplankton are known to photoacclimate, adjusting their internal chlorophyll to carbon ratio in response to changes in light. In this study published in GRL we used data from BGC-Argo floats to show that this acclimation occurs consistently under both clear and cloudy skies across the global ocean. Despite reduced light, phytoplankton maintain similar growth rates, suggesting that current estimates of NPP may be biased low when cloud cover is present.

Recognizing and correcting this bias could improve satellite-based NPP estimates, particularly in persistently cloudy regions like the Southern Ocean or eastern boundary upwelling zones. This, in turn, would refine models of the ocean’s biological carbon pump, leading to better projections of CO₂ uptake and export.

Authors
Charlotte Begouen Demeaux (Univ Maine)
Emmanuel Boss (Univ Maine)
Jason R. Graf (Oregon State Univ)
Michael J. Behrenfeld (Oregon State Univ)
Toby Westberry (Oregon State Univ)

The ocean is shifting toward phosphorus limitation

Posted by mmaheigan

· Friday, February 28th, 2025

Biogeochemical models predict that ocean warming is weakening the vertical transport of nutrients to the upper ocean, with severe implications for marine productivity. However, nutrient concentrations across the ocean surface often fall below detection limits, making it difficult to observe long-term changes.

In a recent study in PNAS, we analyzed over 30,000 nitrate and phosphate depth profiles observed between 1972 and 2022 to quantify nutricline depths, where nutrient concentrations are reliably detected. These depths accurately represent nutrient supplies in a global model, allowing us to assess long-term trends. Over the past five decades, upper ocean phosphate has mostly declined worldwide, while nitrate has remained mostly stable. Model simulations support that this difference is likely due to nitrogen fixation replenishing upper ocean nitrate, whereas phosphate has no equivalent biological source.

Figure caption: Five decades of global and regional nutricline depth data reveal declining phosphate-to-nitrate trends. Nutricline depths were defined based on threshold concentrations of 3 μmol kg−1 nitrate (TNO3) and 3/16 μmol kg−1 phosphate (TPO4). Site-specific trends were quantified for each unique pair of geographic coordinates where sufficient data was available (TNO3, n = 1,859 sites; TPO4, n = 1,641 sites). Shown are 95% confidence intervals (CI95%) calculated for each median trend by generating 10,000 bootstrap samples. The curves over the histograms depict the kernel densities. The sets of error bars from top to bottom are the interquartile ranges of TNO3 and TPO4 from a monthly climatology, the total observations, and the total observations with added measurement error.

These findings suggest that the ocean is becoming more limited in phosphorus. This decline could make phytoplankton less nutritious for marine animals. Fish larvae growth rates correlate with phosphorus availability in the ecosystem, so intensifying phosphorus limitation may greatly impact fisheries worldwide.

Authors
Skylar Gerace (University of California, Irvine)
Jun Yu (University of California, Irvine)
Keith Moore (University of California, Irvine)
Adam Martiny (University of California, Irvine)

@UCI_OCEANS

Persistent bottom trawling impairs seafloor carbon sequestration

Posted by mmaheigan

· Friday, February 28th, 2025

Bottom trawling, a fishing method that uses heavy nets to catch animals that live on and in the seafloor, could release a large amount of organic carbon from seafloor into the water, that metabolizes to CO₂ then outgasses to the atmosphere. The magnitude of this indirect emission has been heavily debated, with estimates spanning from negligibly small to global climate relevant. Thus, a lack of reliable data and insufficient understanding of the process hinders management of bottom trawling for climate protection.

We set out to solve this problem in two steps. First, we analyzed a large field dataset containing more than 2000 sediment samples from one of the most intensely trawled regions globally, the North Sea. We identified a trawling-induced carbon reduction trend in the data, but only in samples taken in persistently intensively trawled areas with multi-year averaged swept area ratio larger than 1 yr^-1. In less intensely trawled areas, there was no clear effect. In a second step, we applied numerical modelling to understand the processes behind the observed change (Fig. 1). Our model results suggest that bottom trawling annually releases one million tonnes of CO₂ in the North Sea and 30 million tonnes globally. Along with sediment resuspension in the wake of the trawls, the main cause for altered sedimentary carbon storage is the depletion of macrofauna, whose locomotion and burrowing effectively buries freshly deposited carbon into deeper sediment layers. By contrast, macrofauna respiration is reduced owing to trawling-caused mortality, partly offsetting the organic carbon loss. Following a cessation of trawling, the simulated benthic biomass can recover in a few years, but the sediment carbon stock would take several decades to be restored to its natural state.

Figure 1. (a) Benthic–pelagic coupling in a natural system. (b) Processes involved in bottom trawling. (c) Model-estimated source and sink terms of organic carbon in surface sediments in the No-trawling (solid fill, n = 67 annual values for 1950–2016) and trawling (pattern fill, n = 67 ensemble-averaged values for 1950–2016) scenarios of the North Sea. © 2024, Zhang, W. et al., CC BY 4.0.

Marine conservation strategies traditionally favor hard bottoms, such as reefs, that are biologically diverse but accumulate limited amounts of organic carbon. Our results indicate that carbon in muddy sediments is more susceptible to trawling impacts than carbon in sand and point out a need to safeguard muddy habitats for climate protection. Our methods and results might be used in the context of marine spatial planning policies to gauge the potential benefits of limiting or ending bottom trawling within protected areas.

Zhang, W., Porz, L., Yilmaz, R. et al. Long-term carbon storage in shelf sea sediments reduced by intensive bottom trawling. Nat. Geosci. 17, 1268–1276 (2024). https://doi.org/10.1038/s41561-024-01581-4

Authors
Wenyan Zhang (Hereon)
Lucas Porz (Hereon)
Rümeysa Yilmaz (Hereon)
Klaus Wallmann (GEOMAR)
Timo Spiegel (GEOMAR)
Andreas Neumann (Hereon)
Moritz Holtappels (AWI)
Sabine Kasten (AWI)
Jannis Kuhlmann (BUND)
Nadja Ziebarth (BUND)
Bettina Taylor (BUND)
Ha Thi Minh Ho-Hagemann (Hereon)
Frank-Detlef Bockelmann (Hereon)
Ute Daewel (Hereon)
Lea Bernhardt (HWWI)
Corinna Schrum (Hereon)

Quantifying uncertainties in future projections of Chesapeake Bay Hypoxia

Posted by mmaheigan

· Wednesday, December 4th, 2024

Climate change is expected to especially impact coastal zones, worsening deoxygenation in the Chesapeake Bay by reducing oxygen solubility and increasing remineralization rates of organic matter. However, simulated responses of this often fail to account for uncertainties embedded within the application of future climate scenarios.

Recent research published in Biogeosciences and in Scientific Reports sought to tackle multiple sources of uncertainty in future impacts to dissolved oxygen levels by simulating multiple climate scenarios within the Chesapeake Bay region using a coupled hydrodynamic-biogeochemical model. In Hinson et al. (2023), researchers showed that a multitude of climate scenarios projected a slight increase in hypoxia levels due solely to watershed impacts, although the choice of global earth system model, downscaling methodology, and watershed model equally contributed to the relative uncertainty in future hypoxia estimates. In Hinson et al. (2024), researchers also found that the application of climate change scenario forcings itself can have an outsized impact on Chesapeake Bay hypoxia projections. Despite using the same inputs for a set of three experiments (continuous, time slice, and delta), the more commonly applied delta method projected an increase in levels of hypoxia nearly double that of the other experiments. The findings demonstrate the importance of ecosystem model memory, and fundamental limitations of the delta approach in capturing long-term changes to both the watershed and estuary. Together these multiple sources of uncertainty interact in unanticipated ways to alter estimates of future discharge and nutrient loadings to the coastal environment.

Figure 1: Chesapeake Bay hypoxia is sensitive to multiple sources of uncertainty related to the type of climate projection applied and the effect of management actions. Percent contribution to uncertainty from Earth System Model (ESM), downscaling methodology (DSC), and watershed model (WSM) for estimates of (a) freshwater streamflow, (b) organic nitrogen loading, (c) nitrate loading, and (d) change in annual hypoxic volume (ΔAHV). (e) Summary of all experiment results for ΔAHV, expressed as a cumulative distribution function. The Multi-Factor experiment (blue line) used a combination of multiple ESMs, DSCs, and WSMs, the All ESMs experiment (pink line) simulated 20 ESMs while holding the DSC and WSM constant, and the Management experiment (green line) only simulated 5 ESMs with a single DSC and WSM but incorporated reductions in nutrient inputs to the watershed. The vertical dashed black line marks no change in AHV.

Understanding the relative sources of uncertainty and impacts of environmental management actions can improve our confidence in mitigating negative climate impacts on coastal ecosystems. Better quantifying contributions of model uncertainty, that is often unaccounted for in projections, can constrain the range of outcomes and improve confidence in future simulations for environmental managers.

Figure 2: A schematic of differences between the Continuous and Delta experiments. In the Delta experiment a combination of altered distributions in future precipitation and changes to long-term soil nitrogen stores eventually result in increased levels of hypoxia (right panel).

Authors
Kyle E. Hinson (Virginia Institute of Marine Science, William & Mary)
Marjorie A. M. Friedrichs (Virginia Institute of Marine Science, William & Mary)
Raymond G. Najjar (The Pennsylvania State University)
Maria Herrmann (The Pennsylvania State University)
Zihao Bian (Auburn University)
Gopal Bhatt (The Pennsylvania State University, USEPA Chesapeake Bay Program Office)
Pierre St-Laurent (Virginia Institute of Marine Science, William & Mary)
Hanqin Tian (Boston College)
Gary Shenk (USGS Virginia/West Virginia Water Science Center)

Swirling Currents: How Ocean Mesoscale Affects Air-Sea CO2 Exchange

Posted by mmaheigan

· Friday, October 25th, 2024

Due to a sparsity of in‐situ observations and the computational burden of eddy‐resolving global simulations, there has been little analysis on how mesoscale processes (e.g., eddies, meanders—lateral scales of 10s to 100s km) influence air‐sea CO₂ fluxes from a global perspective. Recently, it became computationally feasible to implement global eddy‐resolving [O (10) km] ocean biogeochemical models. Many questions related to the influence of mesoscale motions on CO₂ fluxes remain open, including whether ocean eddies serve as hotspots for CO₂ sink or source in specific dynamic regions.

A recent study in Geophysical Research Letters investigated the contribution of ocean mesoscale variability to air-sea CO₂ fluxes by analyzing the CO₂ flux anomaly within the mesoscale band using a coarse-graining approach in a global eddy-resolving biogeochemical simulation. We found that in eddy-rich mid-latitude regions, ocean mesoscale variability can contribute to over 30% of the total CO₂ flux variability. The cumulative net CO₂ flux associated with mesoscale motions is on the order of 10⁵ tC per year. The global pattern of cumulative mesoscale-related CO₂ flux exhibits significant spatial heterogeneity, with the highest values in western boundary currents, the Antarctic Circumpolar Current, and the equatorial Pacific. The local distribution of cumulative mesoscale-related CO₂ flux displays zonal bands alternate between positive (a net source) and negative (a net sink) due to the meandering nature of ocean mesoscale currents, which is related to local relative vorticity and the background cross-stream pCO₂ gradient.

Figure caption. Mesoscale (<nominal 2 degree) contribution to air‐sea CO₂ flux (F^<2°_CO2)in the model. (a)–(d) Monthly time series of F^<2°_CO2 (black lines) and cumulative F^<2°_CO2 (green/red solid lines) in four locations marked in (e). Dashed lines are the least squares regression of cumulative flux for the period 1982–2000; slopes are indicated in the bottom left; (e) Blue colors imply a CO₂ sink, and red colors represent a source. The figure shows the global distribution of the regressed slopes of cumulative F^<2°_CO2. Units are converted from mol m^-2 per year to kg of CO₂ per year using the atomic mass of CO₂. This figure shows significant spatial heterogeneity of mesoscale-modulated CO₂ flux, showing contributions to both CO₂ sources and sinks across different regions of the ocean, with a magnitude on the order of 10⁵ tC per year.

Authors
Yiming Guo (Yale University; now at Woods Hole Oceanographic Institution)
Mary-Louise Timmermans (Yale University)

Turbulent Mixing: A Dominant Source of Oxygen in the Upper Equatorial Pacific

Posted by mmaheigan

· Tuesday, March 12th, 2024

What balances oxygen removal in the equatorial Pacific? For a long time, oxygen in the eastern and central tropical Pacific was assumed to be mainly supplied by the large-scale advection of remotely ventilated waters via the equatorial current system and meridional circulation. A recent study used an eddy-resolving simulation of a global ocean model to show that turbulent mixing and its regulation by mesoscale eddies play a critical role in balancing oxygen removal (by consumption and upwelling) in the upper thermocline. Deeper in the water column, mean advection by the zonal currents and meridional circulation dominates. This mixing is tightly regulated by tropical instability waves, which intensify the shear between the equatorial currents and enhance the downward turbulent mixing flux of oxygen into the thermocline. Mesoscale phenomena thus play an indirect yet critical role as a local pathway of ventilation in this region. Testing these model-based hypotheses in the real ocean through dedicated field studies and long-term observations is needed to advance our understanding of the observed expansion of the oxygen deficient zones (ODZs) and model their future trajectory in a warmer and more stratified ocean.

Figure: The main processes that set the mean structure of oxygen in the equatorial Pacific are assessed in an eddy resolving simulation of the Community Earth System Model (CESM). Panel a shows the climatological oxygen distribution on the 26.25 isopycnal in CESM. Panels b-e show the contribution of advection by mean circulation and eddies, vertical mixing, and production and consumption. These processes are illustrated in panel f). Figure adapted from Eddebbar et al (2024).

Authors
Yassir A. Eddebbar (Scripps Institution of Oceanography)
Daniel B. Whitt (NASA Ames)
Ariane Verdy, (Scripps Institution of Oceanography)
Matthew R. Mazloff (Scripps Institution of Oceanography)
Aneesh C. Subramanian (CU Boulder)
Matthew C. Long, (National Center for Atmospheric Research)

Funding for the Ocean Carbon & Biogeochemistry Project Office is provided by the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA). The OCB Project Office is housed at the Woods Hole Oceanographic Institution.

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