Author Archive for mmaheigan

NEW Report: Pathways Connecting Climate Changes to the Deep Ocean

Posted by mmaheigan 
· Thursday, August 28th, 2025 

Now published – workshop report from the Pathways Connecting Climate Changes to the Deep Ocean: Tracing physical, biogeochemical, and ecological signals from the surface to the deep sea
A joint OCB-US CLIVAR scoping workshop

This workshop will brought together observational oceanographers and modelers across physical, biogeochemical, and ecological communities to assess our understanding of pathways connecting the surface to the seafloor and to develop recommendations for improved detection and attribution of change in the global deep ocean system.

Workshop goals:

  1. Provide an updated comprehensive assessment of the deep ocean’s state and changes across disciplines, of key quantities in which these changes are expressed, and of pathways and timescales connecting the surface to the seafloor.
  2. Review existing observation and modeling tools and their adequacy for constraining, understanding, and attributing changes in the deep ocean system. Identify critical knowledge and observational data gaps and model deficiencies.
  3. Develop a collective set of recommendations for improved detection and attribution of change in the global deep ocean system, with a focus on better serving and supporting deep ocean science across disciplines.
  4. Build an interdisciplinary network of ocean modelers and observers across disciplines. Our aim is to open communication channels and facilitate collaborative exchange of data, knowledge, and tools across communities.

Scientific Organizing Committee
Xinfeng Liang (Univ. Delaware), Monique Messié (MBARI), Leslie Smith (Your Ocean Consulting LLC, DOOS), Isabela Le Bras (WHOI), Patrick Heimbach (Univ. Texas, Austin), Helen Pillar (Univ. Texas, Austin), Zachary Erickson (NOAA/PMEL), Charlie Stock (NOAA/GFDL)

Get the report

Workshop website

 

2026 OCB Activity Proposal Solicitation – open until Oct 24

Posted by mmaheigan 
· Wednesday, August 20th, 2025 

The Ocean Carbon and Biogeochemistry (OCB) Program is soliciting proposals for OCB activities that will take place or begin during the 2026 calendar year. We seek proposals for OCB-relevant workshops and activities as follows:

  • Workshops and training activities – These activities bring together practitioners across disciplines to build community and/or capacity on OCB-relevant topics (see scientific scope below). A training activity is typically limited to 30-40 participants, and a topical workshop is typically limited to 50-60 participants. A hybrid format is strongly encouraged to broaden input and impact. We also welcome proposals for fully virtual workshops and training activities. The participant selection process for training activities should use a pre-determined evaluative rubric. Budgets for these activities will be capped at $70,000.
  • Small group activities – These activities have a specific focus and set of outcomes. They are typically limited to ~8-16 participants and 1-2 years in duration. The majority of participant interaction must take place virtually. Work is to be completed both synchronously and asynchronously via Zoom and collaborative tools (e.g., Google Suite). A small amount of funding (add-on hotel night, food and beverage) can be provided to accommodate a side meeting in conjunction with other workshops (OCB, AGU, OSM, etc.), and publication costs. If a small group activity is a follow-on or direct outgrowth of a previous OCB activity, this connection should be explicitly noted, and PIs must address how this activity will further advance progress. Budgets for these activities will be capped at $15,000.
  • Regional hubs – This is a relatively new OCB activity model (based on the OCB-supported regional mCDR nodes) that aims to foster community building at the regional scale on OCB-relevant topics, including practitioners across sectors, disciplines, and career stages. A small amount of funding is provided to support one large or a series of smaller gatherings, as well as funding to support outcomes (e.g., publications, outreach materials, etc.). There is no travel/lodging support available for these activities, as all participants should be local or within driving distance of a regional hub. Budgets for these activities will be capped at $10,000.

Read the full solicitation

METS RCN workshop recordings

Posted by mmaheigan 
· Tuesday, August 19th, 2025 

Watch recordings from the METS RCN workshop held in April on the OCB YouTube Channel.

International Workshop: FAIR Data Practices for Ship-based Marine Ecological Time Series
April 22-25, 2025 (ASU/BIOS, Bermuda)

Workshop report: https://www.us-ocb.org/fair-data-practices-for-marine-ecological-time-series/

More on METS RCN Workshop: https://www2.whoi.edu/site/mets-rcn/projects/fair-ship-based-ocean-time-series-international-workshop/

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:

  1. AI001 – Advances in Air-Sea Interaction Observations and Remote Sensing: Autonomous Platforms, Multiscale Processes, and Cross-Disciplinary Linkages
  2. AI002 – Aerosol Deposition in the Ocean: Sources, Drivers and Biogeochemical Effects
  3. AI003 – Observations and Modeling of Physical Processes at and near the Air-sea Interface
  4. AI004 – Polar Air-sea Interactions in a Warming Climate
  5. AI006 – The Influence of Marine Biota on Air-sea Exchange Processes
  6. AI007 – Tropical Cyclone-Ocean Interactions: From Weather to Climate
  7. CM001 – Air-Sea Flux as the Limiting Step in Verifying Marine Blue Carbon
  8. CM003 – Biogeochemical and Ecological Insights for Evaluation of Marine Carbon Dioxide Removal (mCDR)
  9. CM005 – Interdisciplinary Approaches and Scalable Pathways for Marine Carbon Dioxide Removal: Integrating Science, Society, and Implementation
  10. CM006 – Modeling Approaches for Marine Carbon Dioxide Removal (mCDR)
  11. CC004 – Circulation, Biogeochemistry, and Coupled Processes in the Indian Ocean: Variability and Vulnerability to Anthropogenic Change
  12. CC015 – Marine Heatwave Drivers and Compound Events in a Changing Climate
  13. CC019 – Ocean Uptake, Transport, and Storage of Heat and Carbon
  14. 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)

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