Timing of abrupt climate change at the end of the Younger Dryas interval from thermally fractionated gases in polar ice

Severinghaus, Jeffrey P.; Sowers, Todd; Brook, Edward J.; Alley, Richard B.; Bender, Michael L.

doi:10.1038/34346

Cited by 656 publications

(550 citation statements)

References 40 publications

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“…The atmospheric methane concentration is a global parameter, and its variations are very rapid. In fact, these variations are strongly correlated with the temperature changes observed in Greenland (Figure 11), with abrupt CH 4 increases lagging those of temperature by only 20-30 years [Severinghaus et al, 1998]. As a crude approximation, we may therefore use the methane concentration in the Antarctic ice cores as a proxy for the high northern latitude temperatures.…”

Section: Thresholds As An Integrating Conceptmentioning

confidence: 99%

Glacial cycles: Toward a new paradigm

Paillard¹

2001

Reviews of Geophysics

206

124

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Abstract. The largest environmental changes in the recent geological history of the Earth are undoubtedly the successions of glacial and interglacial times. It has been clearly demonstrated that changes in the orbital parameters of our planet have a crucial role in these cycles. Nevertheless, several problems in classical astronomical theory of paleoclimate have indeed been identified: (1) The main cyclicity in the paleoclimatic record is close to 100,000 years, but there is no significant orbitally induced changes in the radiative forcing of the Earth in this frequency range (the "100-kyr problem"); (2) the most prominent glacial-interglacial transition occurs at a time of minimal orbital variations (the "stage 11 problem); and (3) at ---0.8 Ma a change from a 41-kyr dominant periodicity to a 100-kyr periodicity occurred without major changes in orbital forcing or in the Earth's configuration (the "late Pleistocene transition problem"). Additionally, the traditional view states that the climate system changes slowly and continuously together with the slow evolution of the large continental ice sheets, whereas recent high-resolution data from ice and marine sediment cores do not support such a gradual scenario. Most of the temperature rise at the last termination occurred over a few decades in the Northern Hemisphere, indicating a major and abrupt reorganization of the ocean-atmosphere system. Similarly, huge iceberg discharges during glacial times, known as Heinrich events, clearly demonstrate that ice sheet changes may also be sometimes quite abrupt. In light of these recent paleoclimatic data the Earth climate system appears much more unstable and seems to jump abruptly between different quasi steady states. Using the concept of thresholds, this new paradigm can be easily integrated into classical astronomical theory and compared with recent observational evidence. If the ice sheet changes are, by definition, the central phenomenon of glacialinterglacial cycles, other components of the climate system (atmospheric CO2 concentration, Southern Ocean productivity, or global deep-ocean circulation) may play an even more fundamental role in these climatic cycles. INTRODUCTIONThe first astronomical theory of paleoclimates is already more than 150 years old (a detailed account of the history of this scientific adventure is given by Imbrie and Imbrie [1979]). The astronomical forcing is now well known, at least for the late Pleistocene. Recent advances in geochemistry helped to quantify the geological record, and it is now evident that climatic cycles have frequencies nearly identical to the Earth's orbital frequencies. However, the story is not finished, since we still do not understand how the climate system works and how small changes in the insolation at the top of the atmosphere can be amplified by the Earth system to create the large climatic changes associated with glacial-interglacial cycles. Traditionally, ice age models have concentrated on the behavior of the large Northern Hemisphere ice sheets, the Lauren...

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Section: Thresholds As An Integrating Conceptmentioning

confidence: 99%

Glacial cycles: Toward a new paradigm

Paillard¹

2001

Reviews of Geophysics

206

124

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“…ka B.P., when there was widespread warming, increase in snow accumulation rate, and reduction in surface wind intensity. The main period of transition may have occupied as little as 50 years [Alley et al, 1993;Björck et al, 1996;Severinghaus et al, 1998;Alley, 2000;Lotter et al, 2000]. It is now becoming clear that the YD event also had a significant impact on tropical Africa [e.g., Roberts et al, 1993;Beuning et al, 1998;Stager et al, 2002;Barker et al, 2004;Johnson et al, 2004;Schefuss et al, 2005;Weldeab et al, 2005;Garcin et al, 2006].…”

Section: Introductionmentioning

confidence: 99%

An abrupt change in the African monsoon at the end of the Younger Dryas

Talbot

Filippi

Jensen

et al. 2007

Geochem Geophys Geosyst

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[1] High-resolution studies of variations in the elemental and stable carbon-and nitrogen-isotope composition of organic matter in cores from Lakes Malawi, Tanganyika, and Bosumtwi (tropical Africa) indicate an abrupt change in the wind-driven circulation of these lakes that, within the limits of available chronologies, was contemporaneous with the end of the Younger Dryas in the northern hemisphere. The change was also coincident with shifts in surface winds recorded in cores from off the west and northeast coasts of Africa. A range of other proxies indicate that these changes in wind regime were accompanied by a marked increase in precipitation in the northern tropics. Africa south of 5°-10°S, on the other hand, initially suffered drought conditions. Together, the evidence suggests an abrupt northward translation of the African monsoon system at circa 11.5 ± 0.25 ka B.P. The data assembled here contribute to a growing body of work showing that the Younger Dryas was a major climatic excursion in tropical Africa. Furthermore, they add substance to recent suggestions that climatic events in the southern hemisphere may have played a significant role in the abrupt demise of the Younger Dryas.

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“…CH 4 shows a clear signal at every D-O event (figure 3; Brook et al 1996Brook et al , 2000Flückiger et al 2004). At the temperature increase that starts a D-O event, it has been shown (by the use of 15 N in N 2 , which imprints a signal into the gas record for a rapid change in temperature due to the thermal gradient imposed on the firn column) that the start of the methane response typically lags the start of the temperature rise by less than 30-70 years (Severinghaus et al 1998;Flückiger et al 2004). The increase in CH 4 is completed in typically about a century.…”

Section: Dansgaard-oeschger Eventsmentioning

confidence: 99%

Methane and nitrous oxide in the ice core record

Wolff

Spahni

2007

Phil. Trans. R. Soc. A.

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Polar ice cores contain, in trapped air bubbles, an archive of the concentrations of stable atmospheric gases. Of the major non-CO 2 greenhouse gases, methane is measured quite routinely, while nitrous oxide is more challenging, with some artefacts occurring in the ice and so far limited interpretation. In the recent past, the ice cores provide the only direct measure of the changes that have occurred during the industrial period; they show that the current concentration of methane in the atmosphere is far outside the range experienced in the last 650 000 years; nitrous oxide is also elevated above its natural levels. There is controversy about whether changes in the pre-industrial Holocene are natural or anthropogenic in origin. Changes in wetland emissions are generally cited as the main cause of the large glacial-interglacial change in methane. However, changing sinks must also be considered, and the impact of possible newly described sources evaluated. Recent isotopic data appear to finally rule out any major impact of clathrate releases on methane at these time-scales. Any explanation must take into account that, at the rapid Dansgaard-Oeschger warmings of the last glacial period, methane rose by around half its glacial-interglacial range in only a few decades. The recent EPICA Dome C (Antarctica) record shows that methane tracked climate over the last 650 000 years, with lower methane concentrations in glacials than interglacials, and lower concentrations in cooler interglacials than in warmer ones. Nitrous oxide also shows DansgaardOeschger and glacial-interglacial periodicity, but the pattern is less clear.

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Timing of abrupt climate change at the end of the Younger Dryas interval from thermally fractionated gases in polar ice

Cited by 656 publications

References 40 publications

Glacial cycles: Toward a new paradigm

Glacial cycles: Toward a new paradigm

An abrupt change in the African monsoon at the end of the Younger Dryas

Methane and nitrous oxide in the ice core record

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