Biogenic carbon pool production maintains the Southern Ocean carbon sink

Huang, Yibin; Fassbender, Andrea J.; Bushinsky, Seth M.

doi:10.1073/pnas.2217909120

Cited by 22 publications

(23 citation statements)

References 70 publications

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“…Regionally, the contribution of advective-diffusive export (labile + semi-labile) to total carbon export can be higher than 50% (ref. 4 ) (Fig. 3c and Extended Data Fig.…”

Section: Organic Carbon Fluxesmentioning

confidence: 91%

“…The downward flux of biologically produced organic carbon draws CO 2 out of the atmosphere, contributing to the maintenance of a vertical gradient of dissolved inorganic carbon (DIC) in the ocean 4 . Much of the primary production occurring in sunlit waters is respired in surface waters without greatly affecting the partitioning of CO 2 between the atmosphere and ocean 2 .…”

Section: Mainmentioning

confidence: 99%

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Biological carbon pump estimate based on multidecadal hydrographic data

Wang,

Fu,

Le Moigne

et al. 2023

Nature

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The transfer of photosynthetically produced organic carbon from surface to mesopelagic waters draws carbon dioxide from the atmosphere1. However, current observation-based estimates disagree on the strength of this biological carbon pump (BCP)2. Earth system models (ESMs) also exhibit a large spread of BCP estimates, indicating limited representations of the known carbon export pathways3. Here we use several decades of hydrographic observations to produce a top-down estimate of the strength of the BCP with an inverse biogeochemical model that implicitly accounts for all known export pathways. Our estimate of total organic carbon (TOC) export at 73.4 m (model euphotic zone depth) is 15.00 ± 1.12 Pg C year−1, with only two-thirds reaching 100 m depth owing to rapid remineralization of organic matter in the upper water column. Partitioned by sequestration time below the euphotic zone, τ, the globally integrated organic carbon production rate with τ > 3 months is 11.09 ± 1.02 Pg C year−1, dropping to 8.25 ± 0.30 Pg C year−1 for τ > 1 year, with 81% contributed by the non-advective-diffusive vertical flux owing to sinking particles and vertically migrating zooplankton. Nevertheless, export of organic carbon by mixing and other fluid transport of dissolved matter and suspended particles remains regionally important for meeting the respiratory carbon demand. Furthermore, the temperature dependence of the sequestration efficiency inferred from our inversion suggests that future global warming may intensify the recycling of organic matter in the upper ocean, potentially weakening the BCP.

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“…Regionally, the contribution of advective-diffusive export (labile + semi-labile) to total carbon export can be higher than 50% (ref. 4 ) (Fig. 3c and Extended Data Fig.…”

Section: Organic Carbon Fluxesmentioning

confidence: 91%

Section: Mainmentioning

confidence: 99%

Biological carbon pump estimate based on multidecadal hydrographic data

Wang,

Fu,

Le Moigne

et al. 2023

Nature

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“…The increased NCP reflects the carbon export potential of particulate organic carbon (POC), dissolved organic carbon (DOC) (Emerson 2014), and also zooplankton‐mediated transport (Boyd et al 2019). Efficient DOC production has been found in the oligotrophic ocean (Roshan and DeVries 2017; Huang et al 2023). Moreover, enhanced zooplankton grazing is expected to result in more DOC production via sloppy feeding and excretion (Moran et al 2022).…”

Section: Discussionmentioning

confidence: 99%

Stimulation of small phytoplankton drives enhanced sinking particle formation in a subtropical ocean eddy

Liu,

Browning,

Laws

et al. 2024

Limnology & Oceanography

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Nutrient transfer into the sunlit surface ocean by cyclonic eddies is potentially crucial for sustaining primary productivity in the stratified subtropical gyres. However, the nature of productivity enhancements, including the flow of matter to higher trophic levels and its impact on carbon fluxes, remain poorly resolved. Here, we report a detailed assessment of the biogeochemical response to a cyclonic eddy in the subtropical Northwest Pacific via a combination of ship‐based and autonomous platforms. Primary production was enhanced twofold within the eddy core relative to reference sites outside, whereas phytoplankton biomass even decreased. Pico‐phytoplankton (< 2 μm) dominated (> 80%) both phytoplankton biomass and primary production inside and outside the eddy. The stimulated primary production in the eddy core was accompanied by an approximately twofold increase in mesozooplankton abundance, an approximately threefold increase in particle formation in the deep chlorophyll maximum layer, as well as significantly enhanced surface oceanic CO2 uptake and net community production. We suggest these observations carry important implications for understanding carbon export in the subtropical ocean and highlight the need to include such subtropical eddy features in ocean carbon budget analyses.

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“…However, formation and dissolution of calcium carbonate by certain phytoplankton species also change the mixed layer DIC and alkalinity content while not influencing the oxygen content (Krumhardt et al, 2020). This process is not accounted for in our budget, which is a reasonable assumption for the ASZ and SIZ where there is low abundance of calcifying organisms (Balch et al, 2016) and the mixed layer DIC consumption attributed to particulate inorganic carbon production, like calcium carbonate, is relatively low compared to organic carbon production (Huang et al, 2023).…”

Section: Uncertainty Estimationmentioning

confidence: 96%

Carbon Outgassing in the Antarctic Circumpolar Current Is Supported by Ekman Transport From the Sea Ice Zone in an Observation‐Based Seasonal Mixed‐Layer Budget

Sauvé,

Gray,

Prend

et al. 2023

JGR Oceans

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Despite its importance for the global cycling of carbon, there are still large gaps in our understanding of the processes driving annual and seasonal carbon fluxes in the high‐latitude Southern Ocean. This is due in part to a historical paucity of observations in this remote, turbulent, and seasonally ice‐covered region. Here, we use autonomous biogeochemical float data spanning 6 full seasonal cycles and with circumpolar coverage of the Southern Ocean, complemented by atmospheric reanalysis, to construct a monthly climatology of the mixed layer budget of dissolved inorganic carbon (DIC). We investigate the processes that determine the annual mean and seasonal cycle of DIC fluxes in two different zones of the Southern Ocean—the Sea Ice Zone (SIZ) and Antarctic Southern Zone (ASZ). We find that, annually, mixing with carbon‐rich waters at the base of the mixed layer supplies DIC which is, in the ASZ, either used for net biological production or outgassed to the atmosphere. In contrast, in the SIZ, where carbon outgassing and the biological pump are weaker, the surplus of DIC is instead advected northward to the ASZ. In other words, carbon outgassing in the southern Antarctic Circumpolar Current (ACC), which has been attributed to remineralized carbon from deep water upwelled in the ACC, is also due to the wind‐driven transport of DIC from the SIZ. These results stem from the first observation‐based carbon budget of the circumpolar Southern Ocean and thus provide a useful benchmark to evaluate climate models, which have significant biases in this region.

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Biogenic carbon pool production maintains the Southern Ocean carbon sink

Cited by 22 publications

References 70 publications

Biological carbon pump estimate based on multidecadal hydrographic data

Biological carbon pump estimate based on multidecadal hydrographic data

Stimulation of small phytoplankton drives enhanced sinking particle formation in a subtropical ocean eddy

Carbon Outgassing in the Antarctic Circumpolar Current Is Supported by Ekman Transport From the Sea Ice Zone in an Observation‐Based Seasonal Mixed‐Layer Budget

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