mmaheigan :: Ocean Carbon & Biogeochemistry

Studying marine ecosystems and biogeochemical cycles in the face of environmental change

Author Archive for mmaheigan – Page 3

Migrating zooplankton increase N2 production in Oxygen Deficient Zones

Posted by mmaheigan

· Friday, August 15th, 2025

Diel Vertically Migrating Zooplankton that spend their day in an Oxygen Deficient Zone to avoid predators are a previously ignored source of organic matter for N₂ producing bacteria.

A recent study in GBC, examined biogeochemical cycling in the offshore Eastern Tropical North Pacific Oxygen Deficient Zone. They found that the daytime maximum in backscattering, used as a proxy for zooplankton and forage fish, corresponded to quantitative PCR maxima in zooplankton and forage fish (metazoan) DNA and to the maximum in biological N₂ gas, and a shoulder of the nitrite maximum. At the same time, the C:N ratio of both suspended and sinking organic matter were reduced, indicating less degraded organic matter. These data strongly suggest that N₂ production in the core of the Oxygen Deficient Zone is stimulated by the daily migration of zooplankton and forage fish in the Oxygen Deficient Zone. These results decouple N₂ production from sinking organic matter fluxes. This work indicates that multicellular animals can affect key ocean biogeochemical cycles, and can cause hot spots of microbial activity well below the sunlit ocean.

Figure caption: Offshore Eastern Tropical North Pacific Oxygen Deficient Zone. The dashed black line indicates the top of the ODZ, the gray lines indicate the boundaries of the deep vertical migration maximum. A) Concentrations of nitrite and oxygen, B) C:N of suspended and of sinking (sediment trap) organic matter, C) Day and night backscattering, a proxy for zooplankton and forage fish, and D) Biological N2 gas concentrations and day and night quantitative PCR data for zooplankton and forage fish (metazoans).

Authors
Clara Fuchsman (UMCES Horn Point Laboratory)
Megan Duffy (Univ Vermont)
Jacob Cram (UMCES Horn Point Laboratory)
Paulina Huanca-Valenzuela (UMCES Horn Point Laboratory)
Louis Plough (UMCES Horn Point Laboratory)
James Pierson (UMCES Horn Point Laboratory)
Catherine Fitzgerald (UMCES Horn Point Laboratory)
Allan Devol (U. of Washington)
Richard Keil (U. of Washington)

Paper: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2024GB008365

Giant iceberg meltwater supplies nutrients to upper ocean layers

Posted by mmaheigan

· Friday, August 15th, 2025

Iceberg meltwater induces mixing which erodes upper-ocean layers. This supplies nutrients, both released from the iceberg and entrained from deeper waters, to surface waters which stimulates phytoplankton growth.

Meltwater from the base, sidewalls and surface of giant icebergs influences upper ocean stratification and mixing. Containing a substantial micro-nutrient load, (incorporating nutrient-rich deep waters along with mineral-rich particles, such as iron and silica, from the melting iceberg), this meltwater is thought to relieve nutrient limitation in surface ecosystems, impacting ocean biological productivity and carbon drawdown. A recent paper in Nature Geoscience provides high-resolution glider measurements right next to giant iceberg A-68A; elucidating the effects of meltwater on water mass modification and near-surface productivity.

The number of calving icebergs is expected to increase in the near future, however the impact of iceberg meltwater on the hydrography, circulation and mixing of the upper ocean is poorly quantified. Understanding the complex physical and biological impacts on the ocean waters through which icebergs transit is difficult to represent in global ocean models, precipitating complexity in prediction of future ocean circulation and the health of Antarctic ecosystems.

Authors
Natasha S Lucas (British Antarctic Survey)
J. Alexander Brearley (British Antarctic Survey)
Katharine R Hendry (British Antarctic Survey)
Theo Spira (University of Gothenburg)
Anne Braakmann-Folgmann (The Arctic University of Norway)
E. Povl Abrahamsen (British Antarctic Survey)
Michael P Meredith (British Antarctic Survey)
Geraint A Tarling (British Antarctic Survey)

Social media:
@krhendry.bsky.social
@TashaOcean
www.bas.ac.uk
@britishantarcticsurvey
@bangor_university
@bangor.sos
@polarwomen @womeninoceanscience
#TashaGoesSouth #PolarResearch #SouthernOcean #AgulhasII #WomenInPhysics #WomenInScience #ExperimentalPhysics #Oceanography #Antarctica

A little extra background:

Roughly a quarter the size of Wales at 5800 square kilometres, A-68A was the biggest iceberg on Earth when it calved from the Larsen-C Ice Shelf in 2017. It arrived at South Georgia as the sixth largest giant iceberg on record. A-68A deposited an estimated 152 billion tonnes of nutrient-rich fresh water, equivalent to 61 million Olympic sized swimming pools, and 27 times the annual freshwater outflow from South Georgia, into the seas around this sub-Antarctic island during the three months of this glider survey.

Ocean gliders are a type of small, robotic underwater vehicle that use density differences, or buoyancy, to move up and down through the water column with wings to create lift, propelling it forward. While ‘flying’ through the water, from the surface to 1 km in depth, the gliders’ sensors measure the water’s properties. The glider surfaces at regular intervals to check its position by GPS, transmit sparse data back to the UK using a satellite phone system, and check for new instructions on where to go and what instruments to turn on.

Research Briefing https://rdcu.be/eg39r

OSM SOLAS session

Posted by mmaheigan

· Monday, July 21st, 2025

SOLAS session: AI005 – SOLAS and SOCOM: Understanding Interactions and Feedbacks between the Ocean and Atmosphere (Chairs: Rachel Stanley, William L Miller, Christa A Marandino, Amanda R Fay, and Thea Hatlen Heimdal) SOLAS town hall

Find many more SOLAS-relevant sessions below and on our our sessions list:

AI001 – Advances in Air-Sea Interaction Observations and Remote Sensing: Autonomous Platforms, Multiscale Processes, and Cross-Disciplinary Linkages
AI002 – Aerosol Deposition in the Ocean: Sources, Drivers and Biogeochemical Effects
AI003 – Observations and Modeling of Physical Processes at and near the Air-sea Interface
AI004 – Polar Air-sea Interactions in a Warming Climate
AI006 – The Influence of Marine Biota on Air-sea Exchange Processes
AI007 – Tropical Cyclone-Ocean Interactions: From Weather to Climate
CM001 – Air-Sea Flux as the Limiting Step in Verifying Marine Blue Carbon
CM003 – Biogeochemical and Ecological Insights for Evaluation of Marine Carbon Dioxide Removal (mCDR)
CM005 – Interdisciplinary Approaches and Scalable Pathways for Marine Carbon Dioxide Removal: Integrating Science, Society, and Implementation
CM006 – Modeling Approaches for Marine Carbon Dioxide Removal (mCDR)
CC004 – Circulation, Biogeochemistry, and Coupled Processes in the Indian Ocean: Variability and Vulnerability to Anthropogenic Change
CC015 – Marine Heatwave Drivers and Compound Events in a Changing Climate
CC019 – Ocean Uptake, Transport, and Storage of Heat and Carbon
HE014 – The Southern Ocean Carbon Sink: Processes, Observations, and Change

Applications for the SOLAS Summer School 2026 are open!

Posted by mmaheigan

· Tuesday, July 15th, 2025

The SOLAS Summer School is a regular, international event with the goal to provide the multidisciplinary air-sea interaction background to the next generation of Earth System scientists. We are proud to celebrate the 10th SOLAS Summer School, with an expanded immersive three-week programme designed for early career researchers. Participants will explore the complex interactions between the ocean, atmosphere, and climate through a dynamic blend of lectures, hands-on practicals, collaborative student-led projects, all aligned with the SOLAS 3.0 framework “SOLAS Science Towards Solutions.”

SOLAS Summer School 2026 will take place from 9-27 March 2026 at Centro Nacional de Pesquisa e Conservação da Biodiversidade Marinha do Nordeste (CEPENE) in Tamandaré, Pernambuco (PE), Brazil.

To apply for Summer School 2026, please submit your application here by 31 August 2025. For students without access to Google Forms please download the form and email your application to solasschool@xmu.edu.cn.

Please send an email to solasschool@xmu.edu.cn, if you have any questions or need further assistance regarding the Summer School.

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)

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.

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.

Author Archive for mmaheigan – Page 3

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