Quantitative and mechanistic understanding of the open ocean carbonate pump - perspectives for remote sensing and autonomous in situ observation

Neukermans, Griet; Bach, Lennart T.; Butterley, A.; Sun, Qibing; Claustre, Hervé; Fournier, Georges

doi:10.1016/j.earscirev.2023.104359

Cited by 17 publications

(8 citation statements)

References 254 publications

(355 reference statements)

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“…By estimating the POC flux from transmissometers or surface variables, BGC‐Argo floats can provide basin‐wide characterizations of the gravitational pump at unique spatio‐temporal resolutions. Pending future deployments of floats with an OST and other carbon flux sensors, such as the Underwater Vision Profiler (Picheral et al., 2022) and particulate inorganic carbon sensors (Bishop et al., 2022; Neukermans et al., 2023), the global array of floats has the potential to fill important knowledge gaps in global ocean carbon sequestration and its linkage with surface ocean ecosystems.…”

Section: Discussionmentioning

confidence: 99%

BioGeoChemical‐Argo Floats Reveal Stark Latitudinal Gradient in the Southern Ocean Deep Carbon Flux Driven by Phytoplankton Community Composition

Terrats,

Claustre,

Briggs

et al. 2023

Global Biogeochemical Cycles

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The gravitational sinking of particles in the mesopelagic layer (∼200–1,000 m) transfers to the deep ocean a part of atmospheric carbon fixed by phytoplankton. This process, called the gravitational pump, exerts an important control on atmospheric CO2 levels but remains poorly characterized given the limited spatio‐temporal coverage of ship‐based flux measurements. Here, we examined the gravitational pump with BioGeoChemical‐Argo floats in the Southern Ocean, a critically under‐sampled area. Using time‐series of bio‐optical measurements, we characterized the concentration of particles in the productive zone, their export and transfer efficiency in the underlying mesopelagic zone, and the magnitude of sinking flux at 1,000 m. We separated float observations into six environments delineated by latitudinal fronts, sea‐ice coverage, and natural iron fertilization. Results show a significant increase in the sinking‐particle flux at 1,000 m with increasing latitude, despite comparable particle concentrations in the productive layer. The variability in deep flux was driven by changes in the transfer efficiency of the flux, related to the composition of the phytoplanktonic community and the size of particles, with intense flux associated with the predominance of micro‐phytoplankton and large particles at the surface. We quantified the relationships between the nature of surface particles and the flux at 1,000 m and used these results to upscale our flux survey across the whole Southern Ocean using surface observations by floats and satellites. We then estimated the basin‐wide Spring‐Summer flux of sinking particles at 1,000 m over the Southern Ocean (0.054 ± 0.021 Pg C).

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Section: Discussionmentioning

confidence: 99%

BioGeoChemical‐Argo Floats Reveal Stark Latitudinal Gradient in the Southern Ocean Deep Carbon Flux Driven by Phytoplankton Community Composition

Terrats,

Claustre,

Briggs

et al. 2023

Global Biogeochemical Cycles

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“…A new autonomous PIC measurement concept was recently proposed by Neukermans and Fournier (2022), which may overcome the aforementioned issues. Such PIC sensors are currently under development and are expected to cover a PIC concentration range of 0.5 to 500 µg C L −1 (Neukermans et al, 2023). These PIC sensors are intended for use on autonomous platforms such as floats profiling up to 2000 m deep, autonomous moorings, tethered buoys, or Saildrones.…”

Section: Observation-based Techniques For Mrv and Limitationsmentioning

confidence: 99%

“…Ballasting of POC flux by coccolithophore calcite and the resulting increase in the sinking velocity of POC aggregates has been confirmed in many experimental studies and may be an important mechanism in some ocean regions. This potential secondary effect of OAE on POC flux could be monitored from autonomous profiling floats equipped with a PIC sensor (Neukermans et al, 2023).…”

Section: Observation-based Techniques For Mrv and Limitationsmentioning

confidence: 99%

Monitoring, Reporting, and Verification for Ocean Alkalinity Enhancement

Bopp

Palter

et al. 2023

Preprint

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Abstract. Monitoring, Reporting, and Verification (MRV) refers to the multistep process of monitoring the amount of greenhouse gas removed by a Carbon Dioxide Removal (CDR) activity and reporting the results of the monitoring to a third party. The third party then verifies the reporting so the results. While MRV is usually conducted in pursuit of certification in a voluntary or regulated CDR market, this chapter focuses on key recommendations for MRV relevant to ocean alkalinity enhancement (OAE) research. Early-stage MRV for OAE research may become the foundation on which markets are built. Therefore, we argue that such research carries a special obligation toward comprehensiveness, reproducibility, and transparency. Observational approaches during field trials should aim to quantify the delivery of alkalinity to seawater and monitor for secondary precipitation, biotic calcification, and other ecosystem changes that can feed back on sources or sinks of greenhouse gases where alkalinity is measurably elevated. Observations of resultant shifts in ocean pCO2 and pH can help determine the efficacy of OAE and are amenable to autonomous monitoring. However, because the ocean is turbulent and energetic and CO2 equilibration between the ocean and atmosphere can take several months or longer, added alkalinity will be diluted to perturbation levels undetectable above background variability on timescales relevant for MRV. Therefore, comprehensive quantification of carbon removal via OAE will be impossible through observational methods alone and numerical simulations will be required. The development of fit-for-purpose models, carefully validated against observational data, will be a critical part of MRV research.

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“…Smaller constellations of cube satellites can sometimes be tasked to give a very high (sub-meter) resolution and sometimes multiple transits in a single day, but their spatial scales are limited to coastal areas, and many are never tasked for open-ocean work. Satellites are capable of imaging the surface expression of bloom events (Neukermans et al, 2023) and CaCO 3 precipitation features, such as whitings (Yao et al, 2023), as well as other optical properties, such as chlorophyll fluorescence. They could potentially measure alkalinity if proxied by salinity (Priyanka et al, 2022).…”

Section: Choice Of Platformmentioning

confidence: 99%

Natural analogs to ocean alkalinity enhancement

2023

Guide to Best Practices in Ocean Alkalinity Enhancement Research

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Ocean alkalinity enhancement (OAE) research can be supplemented by studying the natural alkalinity cycle. In this chapter, we introduce the concept of natural analogs to ocean alkalinity enhancement. We describe Earth system processes relevant to OAE deployment and its measurement, reporting, and verification. We then describe some suitable natural analog locations that could serve as study sites to understand how these processes may interact with OAE. Approaches to examining the geological record are also considered. Practical considerations for establishing a natural analog study are discussed, including geochemical mass balance, choosing a site, establishing a control, choosing a measurement suite and platform, and coordinating with ocean models. We identify rivers and their plumes, glacial fjords, whiting events, and basinal seas with elevated alkalinity as promising candidates for initial natural analog studies. This chapter is not meant to be prescriptive but instead is written to inspire researchers to creatively explore the power of natural analogs to advance our understanding of OAE. Key recommendations include considering appropriate spatial and temporal scales of the study and associated measurement criteria and designing the study with applicable outcomes to OAE research, including implications for deployment and/or monitoring.

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Quantitative and mechanistic understanding of the open ocean carbonate pump - perspectives for remote sensing and autonomous in situ observation

Cited by 17 publications

References 254 publications

BioGeoChemical‐Argo Floats Reveal Stark Latitudinal Gradient in the Southern Ocean Deep Carbon Flux Driven by Phytoplankton Community Composition

BioGeoChemical‐Argo Floats Reveal Stark Latitudinal Gradient in the Southern Ocean Deep Carbon Flux Driven by Phytoplankton Community Composition

Monitoring, Reporting, and Verification for Ocean Alkalinity Enhancement

Natural analogs to ocean alkalinity enhancement

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