Author Archive for mmaheigan

Tracing the biological carbon pump across diverse export regimes

Posted by mmaheigan 
· Thursday, May 29th, 2025 

The ocean’s biological carbon pump (BCP) plays a crucial role in regulating Earth’s climate. But how efficiently does it transport carbon to the deep? It has been difficult to answer this question because observations are sparse, labor-intensive, and the uncertainties of the BCP’s magnitude, which are nearly equivalent to human emissions. Fortunately, autonomous vehicles unlock our ability to observe the upper ocean in three dimensions, garner a greater spatial and temporal range than a research vessel and, unlike a satellite, enable us to see into the deep.

Figure caption: This figure compares mean daily organic carbon flux (blue bars) with ship-based particulate organic carbon (POC) flux (purple bars) to show the different export regimes at 60 and 100 m depth at each study site (left panel: the subpolar northeast Pacific late summer; right panel: North Atlantic spring bloom. The inferred net DOC production (orange bars) was calculated as the difference between the organic carbon flux and the ship-based POC. At times, net community production (NCP, yellow bars) is smaller than the export terms, which suggests a contribution from earlier productivity to export that is consistent with the cruise period beginning on the tail end of a previous bloom. The error bars depict the 95% confidence interval.

A new paper in Limnology & Oceanography leverages these vehicles to autonomously characterize the BCP in two dramatically diverse carbon export regimes. The results reveal strong variability in carbon export efficiency, and further comparison with ship-based data informed the transport pathways. At the lower productivity site, nearly all of the carbon fixed by phytoplankton was routed into sinking particulate organic carbon, while at the highly productive site, nearly half was diverted to dissolved organic carbon. These insights refine our understanding of carbon transport processes and highlight the strength of multiple observational approaches used in tandem. This work is part of the NASA-led EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) program, that ultimately seeks to reduce the uncertainty in the global BCP through improved remote sensing algorithms.

Why does this matter? With climate change mitigation at the forefront of global policy, improving our understanding of the marine carbon cycle is essential. By providing continuous, high-resolution observations, autonomous platforms offer critical data to inform climate predictions, carbon sequestration strategies, and ocean conservation efforts.

 

Authors
Shawnee Traylor (MIT-WHOI Joint Program)
David P. Nicholson (Woods Hole Oceanographic Inst.)
Samantha J. Clevenger (MIT-WHOI Joint Program)
Ken O. Buesseler (Woods Hole Oceanographic Inst.)
Eric D’Asaro (Univ Washington)
Craig M. Lee (Univ Washington)

New over-determined CO2 system solver QUODcarb

Posted by mmaheigan 
· Thursday, May 29th, 2025 

Do you work with over-determined datasets of seawater carbon dioxide system chemistry? QUODcarb (Quantifying Uncertainty in an Over-Determined marine carbonate system), a new over-determined CO2-system solver is described in the recently published “QUODcarb: A Bayesian solver for over-determined datasets of seawater carbon dioxide system chemistry.” The Bayesian formulation of the novel solver and demonstrates its use on an over-determined dataset from the Gulf of Mexico (COMECC-3) that included measurements of DIC, AT, pH, pCO2, and [CO3]. The over-determined calculations, with self-consistent uncertainty quantification, can calculate carbonate ion concentration uncertainty within the GOA-ON climate uncertainty target of 1% with implications for ocean acidification monitoring projects.

Find the Matlab code on GitHub: https://github.com/fprimeau/QUODcarb

Figure caption: Diagram depicting the measured quantities (left side) and the use of thermodynamic constant (pK) formulations and mass balance total (_T) formulations in seawater carbonate chemistry calculations. Adapted from Figure 1 in Carter et al., 2024 a, to illustrate how QUODcarb can replace CO2SYS calculations to include three or more carbonate variable measurements in over-determined calculations while also enabling uncertainty quantification.
Physical measurements are shown with pink backgrounds, mass balance total contents are shown with light green backgrounds, thermodynamic constants are in gray, and carbonate chemistry variables are in yellow. Temperature dependent carbonate chemistry measurements (e.g., pH and pCO2) may be included at different input temperatures. The calculator reflects the analogy that QUODcarb acts as a calculator for solving the system of nonlinear equations.

 

Authors
Marina Fennell (University of California, Irvine)
Francois Primeau (University of California, Irvine)

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)

OCB2025 schedule – science, connection, community

Posted by mmaheigan 
· Tuesday, May 20th, 2025 

Thank you for being a part of OCB2025 online Summer Science Workshop for a week of science, connection, and community - June 2-6

OCB2025 plenary sessions

Constraining the dark ocean carbon cycle: Implications for ocean carbon budgets? (Co-chairs: Anne Dekas, Anela Choy, Jeff Bowman, Randie Bundy)

Rivers to coasts: Biogeochemical linkages and environmental resilience (joint with North American Carbon Program) (Co-chairs: Fei Da, Kanchan Maiti, Shaily Rahman, Libby Larson, David Butman)

Rapidly changing systems (Co-chairs: Kristen Krumhardt, Rachel Stanley, Melissa Melendez)

Bridging scales in the ocean carbon cycle (Co-chairs: Zachary Erickson, Tim DeVries, Roo Nicholson, Daniel Whitt, Dreux Chappell

Learn more and see the schedule

PAUSE on all bulk travel requests

Posted by mmaheigan 
· Friday, May 2nd, 2025 

Until further notice, OCB will not be able to consider bulk travel support requests.

We will post an announcement if this changes.

Now available from BCO-DMO: Time series water sample data from four OOI arrays

Posted by mmaheigan 
· Wednesday, April 30th, 2025 

The Ocean Observatories Initiative (OOI) is a science-driven ocean observing network that delivers real-time data from multiple coastal and open-ocean arrays to address critical science questions regarding the world’s oceans. During each array service cruise OOI performs hydrographic sampling to evaluate and validate the deployed instrumentation. Service cruises are conducted annually for the open ocean arrays and every six months for the coastal arrays.  This repeat sampling has created time series of valuable physical, chemical, and biological information. Water samples from Niskin bottles on CTD casts are analyzed either on the ship or in onshore labs to measure oxygen, salinity, nutrients (nitrate, nitrite, silicate, phosphate, ammonium), chlorophyll, and the carbon system (pH, dissolved inorganic carbon, total alkalinity).

FIGURE 1

OOI launched a collaboration in 2023 with the Biological & Chemical Oceanography Data Management Office (BCO-DMO) to make OOI water sampling data available via the BCO-DMO website and ERDDAP server. BCO-DMO curates publicly available research-ready oceanographic data in accordance with FAIR data principles. Advantages of distributing OOI data through BCO-DMO include concatenation of the cruise-by-cruise data into a single dataset with a Digital Object Identifier (DOI) and provisioning through ERDDAP, which provides both human and machine-to-machine interfaces. The BCO-DMO Dataset pages include descriptions of sampling and processing methods, and README  files for each cruise.

Currently BCO-DMO has data from the OOI Station Papa Array (Gulf of Alaska, annual cruises over 11 years), Irminger Sea Array (North Atlantic, 10 years), Southern Ocean Array (SW of Chile, 6 years) and Argentine Basin Array (South Atlantic, 4 years). You can access the datasets via this direct link or from the BCO-DMO home page: Click on Projects, then search for “OOI Discrete CTD and Water Sampling Cruise Data”.

FIGURE 2

Figures 1 and 2 provide an example of the concatenated datasets using 10 years of data from the Irminger Sea Array. A Python script (implemented in a Jupyter Notebook available in https://github.com/WHOIGit/ooi-on-bco-dmo ) was used to access the data from the BCO-DMO ERDDAP server, extract variables of interest, apply available quality control (QC) flags, and visualize the data.  Figure 1 shows profiles of selected variables for successive cruises to give a sense of the depth-time data coverage. Note that the sample depths are relatively sparse since the OOI sampling goal is to validate instruments on the moorings rather than collect comprehensive profile data. Figure 2 represents profile variability over time by an overplot color-coded by year.

Even though constrained to “Acceptable” QC flags, some of the values plotted appear to be outliers, indicating the need for the user to consider further data quality assessment. Note that Discrete README files within the BCO-DMO dataset and CTD Cast Logs on OOI’s Raw Data Archive provide useful information. For example, the low values of oxygen in 2021are noted as inconsistent with oxygen from the CTD cast, whereas the high values of salinity in 2015 appear to be real, associated with a salinity maximum observed by the CTD. Since creating the Jupyter Notebook, data for two of the Irminger Sea cruises in OOI’s Raw Data Archive have been updated (including Nitrate for the 2021 cruise); these updates will be in the next version of the Irminger Sea dataset on BCO-DMO.

For additional Python scripts to explore OOI Discrete CTD and Water Sampling Cruise Data as distributed by BCO-DMO, for example to plot a discrete parameter against its corresponding CTD sensed parameter, see notebooks available in https://github.com/WHOIGit/ooi-on-bco-dmo/tree/main/notebooks .

SOLAS and OASIS Joint Statement of Collaboration

Posted by mmaheigan 
· Monday, April 28th, 2025 

The Surface Ocean-Lower Atmosphere Study (SOLAS) and the Observing Air-Sea Interactions Strategy (OASIS) are formalising a collaborative partnership to advance and deepen scientific understanding of ocean-atmosphere interactions. This partnership merges SOLAS’s long-standing expertise in biogeochemical and physical processes with OASIS’s leadership in physical flux observations and operational oceanography, enabling a comprehensive, interdisciplinary approach to observing, modeling, and understanding the dynamic air-sea interface.

Through this affiliation, OASIS will become an officially recognised partner in the upcoming SOLAS 2026–2035 science plan, while SOLAS will designate liaisons to the OASIS Scientific Steering Committee. Together, the two programs will co-develop integrated strategies from small-scale process studies to Earth System Model improvements and capacity building in the Global South to joint participation in significant international efforts such as the UN Decade of Ocean Science for Sustainable Development.

Key areas of collaboration include:
• Air-sea transition zone physical-biogeochemical process studies
• Integration of physical and biogeochemical satellite and in situ observational datasets
• Parameterisation of ocean-atmosphere interactions in coupled climate models
• Advancing Earth System Modeling through constrained air-sea flux estimates
• Support for early career researchers via training, liaisons, and interdisciplinary capacity-building programs
The partnership also includes a shared commitment to public engagement, standardised methodologies, and developing educational resources and events such as workshops, town halls, and curriculum initiatives. Regular meetings and representation on each other’s governance structures will ensure ongoing coordination, communication, and community alignment.

SOLAS and OASIS will work together to enhance the global impact of air-sea research by creating a more connected and solution-oriented scientific community.

Read the joint statement of collaboration here.

We welcome feedback on the statement here.

OCB2025 online only

Posted by mmaheigan 
· Monday, April 21st, 2025 

The OCB2025 Summer Science Workshop will take place VIRTUALLY June 2 - 6, 2025.

OCB2025 Plenary Sessions

Constraining the dark ocean carbon cycle: Implications for ocean carbon budgets? (Co-chairs: Anne Dekas, Anela Choy, Jeff Bowman, Randie Bundy)

Rivers to coasts: Biogeochemical linkages and environmental resilience (joint with North American Carbon Program) (Co-chairs: Fei Da, Kanchan Maiti, Shaily Rahman, Libby Larson, David Butman)

Rapidly changing systems (Co-chairs: Kristen Krumhardt, Rachel Stanley, Melissa Melendez)

Bridging scales in the ocean carbon cycle (Co-chairs: Zachary Erickson, Tim DeVries, Roo Nicholson, Daniel Whitt, Dreux Chappell)

Learn more and register

Leaky Deltas workshop summary

Posted by mmaheigan 
· Thursday, April 10th, 2025 

The Leaky Deltas OCB workshop was held 17-20 March 2025 at Louisiana State University, in Baton Rouge, USA, which is situated within the Mississippi River delta. We brought together 57 members of the research community who study river deltas in the context of the global carbon cycle. The goal of the workshop was to create a community consensus on the state of delta carbon cycle science, identify critical knowledge gaps, and brainstorm opportunities and priorities for future research efforts. Participants ranged in career stage from graduate student to senior scientist, and from disciplines ranging from biogeochemistry to geomorphology, river scientists to oceanographers; and scientists using a variety of methodological approaches.

The workshop included five oral sessions, four breakout sessions, numerous opportunities for discussion over meals and coffee breaks, a trip to the LSU Center for River Studies, and a workshop dinner. The breakout sessions were formatted to encourage discussion among interdisciplinary groups of scientists at different career stages. During breakout session 1, participants were randomly assigned to groups that spanned career stages and expertise. This session was aimed at identifying grand challenges in delta carbon cycle science. Breakout session 2 had a disciplinary focus, where we broke out into groups of biogeochemistry, geomorphology, modeling, and ecosystems. Breakout session 3 was broken out into groups based on physical domains of the delta: river, wetlands, subaqueous delta, shelf, and continental slope. A highlight of day three was a field trip to the LSU Center for River Studies, where workshop participants were guided on a tour of the historical changes of the Mississippi River Delta, as well as the large-scale physical model of the delta. On the fourth and final day of the workshop, we had short break-out sessions and reconvened as a whole to synthesize ideas and circle back to the workshop objectives.

In summary, the workshop resulted in a consensus on the key knowledge gaps and research grand challenges, which included constraining the composition of organic matter, the timescales of geomorphic processes, biogeochemical reaction rates, impacts of human perturbations and extreme events, and challenges in monitoring deltaic processes. Workshop participants now have the task of writing a position paper that summarizes these grand research challenges, identifies the data needed to address these challenges, and recommends a framework and directions for future research. One outcome of the workshop included the structure and organization for this paper. The early career workshop participants will also lead an early-career-led perspective paper that discusses ideas for integrating new technologies and methodologies to address these grand challenges and identifies future challenges for the delta science community.

Learn more about this workshop

New: Connecting Observations to Models

Posted by mmaheigan 
· Thursday, April 10th, 2025 

Ombres, E., H. Benway, K. Bisson, A. Larkin, L. Perotti, L. Wright-Fairbanks (eds.) (2024). Connecting Observations to Models: Biogeochemical Observing and Modeling Workshop, 2024 Summary Report and Suggested Steps Forward. Published Date: 2024 Series: NOAA technical memorandum OAR-OAP ; 6, DOI: https://doi.org/10.25923/wpdj-ja69

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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.