The sequence of events surrounding Termination II and their implications for the cause of glacial‐interglacial CO<sub>2</sub> changes

Broecker, Wallace S.; Henderson, Gideon M.

doi:10.1029/98pa00920

Cited by 362 publications

(244 citation statements)

References 91 publications

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“…One proposal for lowering glacialpCO2 is to raise the NO•-inventory of the glacial ocean until the biological pump reaches limitation by PO43-, increasing the capacity of the biological pump [Falkowski, 1997]. A more radical proposal is to raise the NO•-inventory and release plankton from PO43-limitation, by assuming that the plankton N/P ratio follows the chemistry of the seawater in which they grow [Broecker and Henderson, 1998]. This would allow a much larger increase in the strength of the biological pump.…”

Section: Organic Carbon Production and Export To The Deep Seamentioning

confidence: 99%

“…The Milankovitch orbital theory for the glacial cycles would seem to imply the latter, because there is a clear physical link between Northern Hemisphere summer heating and ice sheets but no easy link from orbital variations to pCO 2. However, in the last two glacial terminations, the pCO 2 rise clearly precedes the •80 of the atmosphere (an indicator of melted ice sheets) by several thousand years [Sowers and Bender, 1995;Broecker and Henderson, 1998], implying that pCO2 is a primary driver (Figure 2). Alternatively, pCO 2 could be driven by changes in meteorological forcing, such as dust delivery of trace metals to the ocean surface, resulting in an acausal correlation between Northern Hemisphere summer insolation and ice volume.…”

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confidence: 99%

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What caused the glacial/interglacial atmospheric pCO₂ cycles?

Archer

Winguth²,

Lea

et al. 2000

Reviews of Geophysics

455

472

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Abstract. Fifteen years after the discovery of major glacial/interglacial cycles in the CO2 concentration of the atmosphere, it seems that all of the simple mechanisms for lowering pCO 2 have been eliminated. We use a model of ocean and sediment geochemistry, which includes new developments of iron limitation of biological production at the sea surface and anoxic diagenesis and its effect on CaCO 3 preservation in the sediments, to evaluate the current proposals for explaining the glacial/ interglacial pCO 2 cycles within the context of the ocean carbon cycle. After equilibration with CaCO 3 the model is unable to generate glacial pCO 2 by increasing ocean NO•-but predicts that a doubling of ocean H4SiO 4 might suffice. However, the model is unable to generate a doubling of ocean H4SiO 4 by any reasonable changes in SiO 2 weathering or production. Our conclusions force us to challenge one or more of the assumptions at the foundations of chemical oceanography. We can abandon the stability of the "Redfield ratio" of nitrogen to phosphorus in living marine phytoplankton and the ultimate limitation of marine photosynthesis by phosphorus. We can challenge the idea that the pH of the deep ocean is held relatively invariant by equilibrium with CaCO 3. A third possibility, which challenges physical oceanographers, is that diapycnal mixing in ocean circulation models exceeds the rate of mixing in the real ocean, diminishing the model pCO 2 sensitivity to biological carbon uptake. The ice age cycles underwent a midlife transition

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Section: Organic Carbon Production and Export To The Deep Seamentioning

confidence: 99%

mentioning

confidence: 99%

What caused the glacial/interglacial atmospheric pCO₂ cycles?

Archer

Winguth²,

Lea

et al. 2000

Reviews of Geophysics

455

472

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“…This ice core extends back to 420,000 yr ago, allowing comparison of the Holocene interval with four previous interglacials (Broecker and Henderson, 1998;Petit et al, 1999). It provides the most detailed and reliable local temperature proxy of the last interglacial (Fig.…”

Section: Polar Icementioning

confidence: 99%

Last Interglacial Climates

Kukla¹,

et al. 2002

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The last interglacial, commonly understood as an interval with climate as warm or warmer than today, is represented by marine isotope stage (MIS) 5e, which is a proxy record of low global ice volume and high sea level. It is arbitrarily dated to begin at approximately 130,000 yr B.P. and end at 116,000 yr B.P. with the onset of the early glacial unit MIS 5d. The age of the stage is determined by correlation to uranium-thorium dates of raised coral reefs. The most detailed proxy record of interglacial climate is found in the Vostok ice core where the temperature reached current levels 132,000 yr ago and continued rising for another two millennia. Approximately 127,000 yr ago the Eemian mixed forests were established in Europe. They developed through a characteristic succession of tree species, probably surviving well into the early glacial stage in southern parts of Europe.

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“…This warming of the Southern Hemisphere corresponds to the timing of maximal summer insolation in this hemisphere (Fig. 3A, B), which has been suggested to be one of the possible causes for this SST lead [Broecker and Henderson, 1998] Comparison with the orbital parameters shows that most of the thermal record seems to be forced by low latitude insolation related to eccentricity. However, during Stages 11-9 and Termination I, the SST-obliquity concordance suggests a major control from high latitudes.…”

Section: Introductionmentioning

confidence: 99%