Subantarctic Mode Water Biogeochemical Formation Properties and Interannual Variability

Bushinsky, Seth M.; Cerovečki, Ivana

doi:10.1029/2022av000722

Cited by 6 publications

(6 citation statements)

References 88 publications

(205 reference statements)

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“…The pCO ocn 2 is not directly measured by the floats but derived using measurements from pH sensors, as well as CTD and oxygen data to estimate total Alkalinity and carbon parameters 91,94 . We acknowledge pCO ocn 2 inferred from float data may be biased high 14,18,21,22,[101][102][103][104] , and systematic biases could be potentially corrected by leveraging the higher accuracy O 2 data from the floats 102 . However, for the purpose of this study, we are interested in the change induced by storms relative to pre-storm conditions in a statistical sense (averaging across ~1000s of profiles).…”

Section: Air-sea Co 2 Fluxes Derived From Argo Floatsmentioning

confidence: 99%

Extratropical storms induce carbon outgassing over the Southern Ocean

Carranza,

Long,

Di Luca

et al. 2024

npj Clim Atmos Sci

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The strength and variability of the Southern Ocean carbon sink is a significant source of uncertainty in the global carbon budget. One barrier to reconciling observations and models is understanding how synoptic weather patterns modulate air-sea carbon exchange. Here, we identify and track storms using atmospheric sea level pressure fields from reanalysis data to assess the role that storms play in driving air-sea CO2 exchange. We examine the main drivers of CO2 fluxes under storm forcing and quantify their contribution to Southern Ocean annual air-sea CO2 fluxes. Our analysis relies on a forced ocean-ice simulation from the Community Earth System Model, as well as CO2 fluxes estimated from Biogeochemical Argo floats. We find that extratropical storms in the Southern Hemisphere induce CO2 outgassing, driven by CO2 disequilibrium. However, this effect is an order of magnitude larger in observations compared to the model and caused by different reasons. Despite large uncertainties in CO2 fluxes and storm statistics, observations suggest a pivotal role of storms in driving Southern Ocean air-sea CO2 outgassing that remains to be well represented in climate models, and needs to be further investigated in observations.

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Section: Air-sea Co 2 Fluxes Derived From Argo Floatsmentioning

confidence: 99%

Extratropical storms induce carbon outgassing over the Southern Ocean

Carranza,

Long,

Di Luca

et al. 2024

npj Clim Atmos Sci

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“…However, the uncertainty of the ocean carbon sink is highest in the Southern Ocean (Fay & McKinley, 2021; Friedlingstein et al., 2022; Gloege et al., 2021) and the discrepancy between models and observations is also most significant there compared to other ocean basins (Hauck et al., 2020). There is also discrepancy between observational estimates of the Southern Ocean carbon sink, or the carbonate parameters necessary to determine it, based on the method or data set used (Bushinsky & Cerovečki, 2023; Coggins et al., 2023; Long et al., 2021; Mackay & Watson, 2021; Wu et al., 2022; Wu & Qi, 2022). Further, sampling alias linked to the spatial distribution of available observations has been shown to be significant (Hauck et al., 2023).…”

Section: Discussionmentioning

confidence: 99%

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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“…However, the uncertainty of the ocean carbon sink is highest in the Southern Ocean Friedlingstein et al, 2022;Gloege et al, 2021) and the discrepancy between models and observations is also most significant there compared to other ocean basins (Hauck et al, 2020). There is also discrepancy between observational estimates of the Southern Ocean carbon sink, or the carbonate parameters necessary to determine it, based on the method or data set used (Bushinsky & Cerovečki, 2023;Coggins et al, 2023;Long et al, 2021;Mackay & Watson, 2021;Wu & Qi, 2022). Further, sampling alias linked to the spatial distribution of available observations has been shown to be significant (Hauck et al, 2023).…”

Section: Discussionmentioning

confidence: 99%

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

Preprint

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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 an 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 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 frontal zones of the Antarctic Circumpolar Current (ACC)—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 then, 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 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.

show abstract

Subantarctic Mode Water Biogeochemical Formation Properties and Interannual Variability

Cited by 6 publications

References 88 publications

Extratropical storms induce carbon outgassing over the Southern Ocean

Extratropical storms induce carbon outgassing over the Southern Ocean

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

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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