CO<sub>2</sub>‐induced change in a coupled ocean‐atmosphere model and its paleoclimatic implications

Manabe, Syukuro; Bryan, Kirk

doi:10.1029/jc090ic06p11689

Cited by 232 publications

(171 citation statements)

References 35 publications

(24 reference statements)

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“…Although the precise latitudinal registry may have varied in the geologic past because of different continental distributions, the overall latitudinal width of the equatorial humid belt may be a stable feature of global climate. This is suggested by climate model calculations showing relatively similar latitudinal patterns of P-E for pCO 2 values ranging up to 10 times the preindustrial level (59) and is supported by the paleolatitudinal distribution over geologic time of evaporites, which is approximately the same as occurs today (60). We use a zonally averaged P-E latitudinal profile calculated for 8 ϫ pCO 2 with an idealized geography (59) for the approximate position of the equatorial humid belt in the early Cenozoic (Fig.…”

Section: Weathering Of Deccan Traps In Equatorial Humid Beltmentioning

confidence: 82%

Equatorial convergence of India and early Cenozoic climate trends

Kent

Muttoni

2008

Proc. Natl. Acad. Sci. U.S.A.

143

108

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India's northward flight and collision with Asia was a major driver of global tectonics in the Cenozoic and, we argue, of atmospheric CO 2 concentration (pCO2) and thus global climate. Subduction of Tethyan oceanic crust with a carpet of carbonate-rich pelagic sediments deposited during transit beneath the high-productivity equatorial belt resulted in a component flux of CO 2 delivery to the atmosphere capable to maintain high pCO 2 levels and warm climate conditions until the decarbonation factory shut down with the collision of Greater India with Asia at the Early Eocene climatic optimum at Ϸ50 Ma. At about this time, the India continent and the highly weatherable Deccan Traps drifted into the equatorial humid belt where uptake of CO 2 by efficient silicate weathering further perturbed the delicate equilibrium between CO 2 input to and removal from the atmosphere toward progressively lower pCO 2 levels, thus marking the onset of a cooling trend over the Middle and Late Eocene that some suggest triggered the rapid expansion of Antarctic ice sheets at around the Eocene-Oligocene boundary.CO2 ͉ Deccan ͉ Tethys ͉ Himalaya ͉ Eocene M odern-day glacial climate, characterized by polar ice at sea level, is the long-term cooling derivative of a Cretaceousearly Cenozoic world dominated by warm conditions and the general absence of ice sheets (1, 2). The zenith of global warmth in the Cenozoic (0-65 Ma) was reached at Ϸ50 Ma during the Early Eocene climatic optimum (EECO) as the culmination of a Late Paleocene-Early Eocene (Ϸ60-50 Ma) warming trend in oceanic bottom waters (3) (Fig. 1A). The EECO was characterized by the widespread occurrence of cherts (4) (Fig. 1B) and reflected in warm climate conditions at even extreme high latitudes (5, 6). A persistent cooling trend ensued over the Middle and Late Eocene that eventually plummeted into a glacial climate mode with the inception of major Antarctic ice sheets at Oi-1 near the Eocene-Oligocene boundary at Ϸ34 Ma (7). Changes in ocean circulation and heat transport related to the opening of Southern Ocean gateways (8) occurred well after the start of the cooling trend at Ϸ50 Ma and do not seem to adequately account for inception of Antarctic glaciation according to recent climate models (e.g., refs. 9 and 10). Instead, reduction in greenhouse gas concentrations is the more likely fundamental cause of Antarctic freezing and global cooling (10). This is supported by the occurrence of high (albeit highly scattered) pCO 2 estimated values of Ͼ1,000 ppm at around the EECO (e.g., 11, 12; see also ref. 13) and generally low (Ͻ500 ppm) pCO 2 estimated values after Oi-1 that followed a decline that more or less parallels the long-term temperature record (14, 15) (Fig. 1 A). However, what triggered the global cooling from the EECO to Oi-1 (and thus the cause of the long-term decrease in pCO 2 ) is unclear (16).The BLAG model (17, 18) postulates that long-term changes in pCO 2 and resulting climate were driven primarily by variations in mantle outgassing tied to global seafloor prod...

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Section: Weathering Of Deccan Traps In Equatorial Humid Beltmentioning

confidence: 82%

Equatorial convergence of India and early Cenozoic climate trends

Kent

Muttoni

2008

Proc. Natl. Acad. Sci. U.S.A.

143

108

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“…12). First, the warming could have accelerated the hydrologic cycle and thus increased rates of chemical weathering (Manabe and Bryan, 1985;Berner, 1994;White and Blum, 1995;Sloan, Bluth, and Filippelli, 1997). This would increase the flux of nutrients (particularly phosphorus) to the oceans and thus help stimulate biological productivity (Pedersen and Calvert, 1990).…”

mentioning

confidence: 99%

Seawater strontium isotopes, oceanic anoxic events, and seafloor hydrothermal activity in the Jurassic and Cretaceous

Jones¹

2001

American Journal of Science

460

323

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ABSTRACT. There were three negative seawater strontium-isotope excursions (shifts to lower 87 Sr/ 86Sr values) during the Jurassic and Cretaceous that were of relatively short duration (5-13 my) and showed a relatively quick recovery to pre-excursion 87 Sr/ 86 Sr ratios. These excursions occurred in the Pliensbachian-Toarcian (Early Jurassic), Aptian-Albian, and Cenomanian-Santonian (Early and Late Cretaceous respectively). Each excursion coincided closely in time with an Oceanic Anoxic Event (OAE) marked by sediments unusually rich in organic carbon. The Jurassic OAE occurred at the end of the strontium-isotope excursion, whereas the two Cretaceous OAEs occurred at the onset of the accompanying strontium-isotope excursions.The possible causes of these excursions were evaluated by successively examining the changes in the riverine strontium fluxes, riverine 87 Sr/ 86 Sr ratios, or hydrothermal strontium fluxes required to produce each excursion. A range of seawater strontium budgets was used to encompass the uncertainties in modern and ancient cycles. To produce the excursions, we calculate that the riverine strontium fluxes would have had to decrease by 6 to 15 percent or the fluvial 87 Sr/ 86 Sr ratios by 0.00019 to 0.00046. The uncertainties largely stem from the assumed magnitude of the hydrothermal strontium flux at the onset of each excursion. Alternatively, increases in sea-floor hydrothermal activity of 7 to 104 percent could also have produced the strontium-isotope excursions. This large range is due mostly to uncertainties in the relative flux of strontium from axial high-temperature hydrothermal systems and low-temperature off-axis systems. Only a small portion of this range stems from uncertainties in the riverine strontium terms.The possible causes of the excursions were further evaluated by examining several geologic factors that could have affected riverine strontium, including climate change, sealevel, and the eruption of flood basalts. We conclude that neither variations in riverine strontium fluxes nor in 87 Sr/ 86 Sr ratios is the likely cause of the strontiumisotope excursions. The most probable explanation is increased rates of hydrothermal activity related to increased ocean-crust production at the mid-ocean ridges.The close correlation in time between the strontium-isotope excursions and the major Oceanic Anoxic Events (OAEs) is compatible with a causal linkage. We propose that increased ocean-crust production led to enhanced CO 2 outgassing and global warming, which in turn led to several processes that acted to make surface ocean waters more productive. However, because OAEs did not occur throughout the proposed periods of enhanced hydrothermal activity, it appears that these processes only preconditioned the oceans for the OAEs: sealevel rise may have been the final trigger. This model explains why all three OAEs did not occur at the same time relative to the onset of excess hydrothermal activity and why OAEs are not associated with every sealevel rise documented in the stratigraphic re...

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“…Another possible dynamical mechanism that might contribute to the resolution of the paradox is the change in advection of heat due to the non-linear equation of state for seawater (Pond and Pickard, 1983) as shown in Manabe and Bryan (1985) and Gough and Lin (1992). In these studies a more vigorous thermohaline circulation was found, under certain conditions, when the temperature gradient weakened.…”

Section: Introductionmentioning

confidence: 74%

“…Manabe and Bryan (1985) found that, in their ocean circulation simulations, the meridional density gradient increased while the temperature gradient decreased. This arises from the non-linearity of the coefficient of thermal expansion for sea water (Pond and Pickard, 1983).…”

Section: Introductionmentioning

confidence: 99%

Ocean heat transport and a climate paradox

Gough¹,

Lozinova

2001

Atmosphere-Ocean

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CO₂‐induced change in a coupled ocean‐atmosphere model and its paleoclimatic implications

Abstract: The climatic effects of very large changes of CO 2 concentration in the atmosphere are explored using a general circulation model of the coupled ocean-atmosphere system. As a simplification the model has an annual mean insolation and a highly idealized geography.

Cited by 232 publications

References 35 publications

Equatorial convergence of India and early Cenozoic climate trends

Equatorial convergence of India and early Cenozoic climate trends

Seawater strontium isotopes, oceanic anoxic events, and seafloor hydrothermal activity in the Jurassic and Cretaceous

Ocean heat transport and a climate paradox

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CO2‐induced change in a coupled ocean‐atmosphere model and its paleoclimatic implications

Abstract: The climatic effects of very large changes of CO 2 concentration in the atmosphere are explored using a general circulation model of the coupled ocean-atmosphere system. As a simplification the model has an annual mean insolation and a highly idealized geography.

Cited by 232 publications

References 35 publications

Equatorial convergence of India and early Cenozoic climate trends

Equatorial convergence of India and early Cenozoic climate trends

Seawater strontium isotopes, oceanic anoxic events, and seafloor hydrothermal activity in the Jurassic and Cretaceous

Ocean heat transport and a climate paradox

Contact Info

Product

Resources

About

CO₂‐induced change in a coupled ocean‐atmosphere model and its paleoclimatic implications