Air-sea disequilibrium enhances ocean carbon storage during glacial periods

Khatiwala, S.; Schmittner, Andreas; Muglia, Juan

doi:10.1126/sciadv.aaw4981

Cited by 93 publications

(140 citation statements)

References 65 publications

(103 reference statements)

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“…This decomposition assumes that dissolved oxygen in the ocean could have reached equilibrium everywhere. Due to disequilibrium during air‐sea gas exchange, AOU changes might be overestimated and therefore so might be

δ^{13} C_{B I O}

estimates (Khatiwala et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…Intermediate‐depth North Atlantic

δ^{13}

C anomalies are thus due to both a change in

δ^{13}

C and PO 4 NADW end‐members, as well as to changes in oceanic circulation. It should however be noted that, as this decomposition method relies on calculating AOU from the saturated dissolved O

_{2}

concentration in the ocean,

δ^{13} C_{B I O}

changes might be overestimated (Khatiwala et al, ).…”

Section: Comparison With Paleorecords and Implicationsmentioning

confidence: 99%

See 1 more Smart Citation

Enhanced Mid‐depth Southward Transport in the Northeast Atlantic at the Last Glacial Maximum Despite a Weaker AMOC

Menviel

Spence

Skinner

et al. 2020

Paleoceanog and Paleoclimatol

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While previous studies consistently suggest that North Atlantic Deep Water (NADW) was shallower at the Last Glacial Maximum (LGM) than at pre‐industrial, its strength is still controversial. Here, using a series of LGM experiments, we show that proxy records are consistent with a shallower and ∼50% weaker NADW, associated with a ∼3° equatorward shift of the sea ice edge and convection sites in the Norwegian Sea. A shoaling and weakening of NADW further allow penetration of Antarctic Bottom Water in the North Atlantic, despite Antarctic Bottom Water transport being reduced by ∼40%. While the Deep Western Boundary Current in the northwest Atlantic weakens with NADW, the mid‐depth southward flow on the east side of the north Mid‐Atlantic Ridge strengthens, consistent with paleorecords. This northeast Atlantic intensification is due to a change in density gradients: a weaker AMOC reduces the transport of equatorial waters to the northeast Atlantic, thus weakening the North Atlantic zonal density gradient. The resultant globally weaker oceanic circulation at the LGM would have contributed to an increase in oceanic carbon content and thus a decrease in atmospheric CO 2 concentration.

show abstract

δ^{13} C_{B I O}

estimates (Khatiwala et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…Intermediate‐depth North Atlantic

δ^{13}

C anomalies are thus due to both a change in

δ^{13}

C and PO 4 NADW end‐members, as well as to changes in oceanic circulation. It should however be noted that, as this decomposition method relies on calculating AOU from the saturated dissolved O

_{2}

concentration in the ocean,

δ^{13} C_{B I O}

changes might be overestimated (Khatiwala et al, ).…”

Section: Comparison With Paleorecords and Implicationsmentioning

confidence: 99%

Enhanced Mid‐depth Southward Transport in the Northeast Atlantic at the Last Glacial Maximum Despite a Weaker AMOC

Menviel

Spence

Skinner

et al. 2020

Paleoceanog and Paleoclimatol

View full text Add to dashboard Cite

show abstract

“…These tracers are reset to the local phosphate concentration and alkalinity at the surface, while being treated as passive tracers below. The alternative would be to extrapolate preformed alkalinity and phosphate using apparent oxygen utilization (36; 29); this leads to different results for the carbon pump decomposition (not shown) and may generate substantial overestimations and biases in the interpretation (41).…”

Section: Carbon Pump Decompositionmentioning

confidence: 99%

Global cooling linked to increased glacial carbon storage via changes in Antarctic sea ice

Marzocchi

Jansen

2019

Nat. Geosci.

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Paleoceanographic reconstructions indicate that the distribution of global ocean water masses has undergone major glacial-interglacial rearrangements over the past ∼2.5 million years. Given that the ocean is the largest carbon reservoir, such circulation changes were likely key in driving the variations in atmospheric CO 2 concentrations observed in the ice-core record. However, we still lack a mechanistic understanding of the ocean's role in regulating CO 2 on these time scales. Here we show that glacial ocean-sea-ice numerical simulations with a single-basin general circulation model, forced solely by atmospheric cooling, can predict ocean circulation patterns associated with increased atmospheric carbon sequestration in the deep ocean. Under such conditions, Antarctic Bottom Water becomes more isolated from the sea surface as a result of two connected factors: reduced air-sea gas exchange under

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“…This suggestion should be taken cautiously, knowing that the variation reported by Sutton et al (2013) was the maximum amount of variability explained by species-specific fractionation at one location. During the last glacial maximum (LGM), atmospheric CO 2 dropped from 280 to 190 ppmv likely related to an increase in surface productivity (Khatiwala et al, 2019). Indeed, several authors proposed that massive aeolian inputs of continental iron or silica during the LGM boosted the biological carbon production (Angelis et al, 1987;Duce et al, 1991;Martin et al, 1994;Monnin, 2001;Khatiwala et al, 2019).…”

Section: Broader Implicationsmentioning

confidence: 99%

An Overlooked Silica Source of the Modern Oceans: Are Sandy Beaches the Key?

et al. 2019

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We consider the Si flux resulting from sand grain dissolution on beaches under the pressure of the intensive and continuous shaking by the waves, a potential source of oceanic DSi that is not currently considered. Today, DSi source and sink fluxes are balanced within large uncertainties, at ca. 10.4 ± 4.2 and 14.6 ± 7.8 × 10 12 mol yr −1 , respectively, underlining that some processes are not well constrained and possibly overlooked so far. To quantitatively explore this idea, we first realized an experimental dissolution of quartz grains in a stirred vessel designed to simulate the sediment orbital motion induced by the waves. These experiments lead to the calculation of a solidliquid mass-transfer coefficient directly linked to the rotation speed of the shaker. This coefficient being itself related to the energy communicated to the liquid, we could apply the Nienow relationship to calculate a mass-transfer coefficient for beach sand exposed to 1 m height waves. Extrapolation of this value to the whole sandy beaches led us to conclude that this mechanism could be significant, shortening the calculated residence time of oceanic DSi by up to a factor 2.

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Air-sea disequilibrium enhances ocean carbon storage during glacial periods

Cited by 93 publications

References 65 publications

Enhanced Mid‐depth Southward Transport in the Northeast Atlantic at the Last Glacial Maximum Despite a Weaker AMOC

Enhanced Mid‐depth Southward Transport in the Northeast Atlantic at the Last Glacial Maximum Despite a Weaker AMOC

Global cooling linked to increased glacial carbon storage via changes in Antarctic sea ice

An Overlooked Silica Source of the Modern Oceans: Are Sandy Beaches the Key?

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