Simulations of anthropogenic change in the strength of the Brewer–Dobson circulation

Butchart, Neal; Scaife, Adam A.; Bourqui, M. S.; Grandpré, J. de; Hare, Sylvia H. E.; Kettleborough, J.; Langematz, Ulrike; Manzini, Elisa; Sassi, Fabrizio; Shibata, Kiyotaka; Shindell, D. T.; Sigmond, Michael

doi:10.1007/s00382-006-0162-4

Cited by 398 publications

(454 citation statements)

References 46 publications

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“…This leads to an O 3 reduction in the upper tropical troposphere and an O 3 buildup at high latitudes in the lower stratosphere, (in part also due to reduced ozone destruction in the cooler lower stratosphere, consistent with our earlier finding based on an older model version, Zeng and Pyle, 2003). In a recent multimodel comparison (Butchart et al, 2006) most participating models also produce an increase in the stratosphere-troposphere mass exchange rate in response to growing greenhouse gas concentrations. Consequently, the enhanced STE transports stratospheric O 3 more rapidly to the troposphere leading to significant increases of O 3 in the free troposphere; for the NH this feature is most pronounced in April when STE normally maximizes.…”

Section: Response To Climate Changesupporting

confidence: 87%

Impact of climate change on tropospheric ozone and its global budgets

2008

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Abstract.We present the chemistry-climate model UM CAM in which a relatively detailed tropospheric chemical module has been incorporated into the UK Met Office's Unified Model version 4.5. We obtain good agreements between the modelled ozone/nitrogen species and a range of observations including surface ozone measurements, ozone sonde data, and some aircraft campaigns.Four 2100 calculations assess model responses to projected changes of anthropogenic emissions (SRES A2), climate change (due to doubling CO 2 ), and idealised climate change-associated changes in biogenic emissions (i.e. 50% increase of isoprene emission and doubling emissions of soil-NO x ). The global tropospheric ozone burden increases significantly for all the 2100 A2 simulations, with the largest response caused by the increase of anthropogenic emissions. Climate change has diverse impacts on O 3 and its budgets through changes in circulation and meteorological variables. Increased water vapour causes a substantial ozone reduction especially in the tropical lower troposphere (>10 ppbv reduction over the tropical ocean). On the other hand, an enhanced stratosphere-troposphere exchange of ozone, which increases by 80% due to doubling CO 2 , contributes to ozone increases in the extratropical free troposphere which subsequently propagate to the surface. Projected higher temperatures favour ozone chemical production and PAN decomposition which lead to high surface ozone levels in certain regions. Enhanced convection transports ozone precursors more rapidly out of the boundary layer resulting in an increase of ozone production in the free troposphere. Lightning-produced NO x increases by about 22% in the doubled CO 2 climate and contributes to ozone production.The response to the increase of isoprene emissions shows that the change of ozone is largely determined by background NO x levels: high NO x environment increases ozone producCorrespondence to: G. Zeng (guang.zeng@atm.ch.cam.ac.uk) tion; isoprene emitting regions with low NO x levels see local ozone decreases, and increase of ozone levels in the remote region due to the influence of PAN chemistry. The calculated ozone changes in response to a 50% increase of isoprene emissions are in the range of between −8 ppbv to 6 ppbv. Doubling soil-NO x emissions will increase tropospheric ozone considerably, with up to 5 ppbv in source regions.

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Section: Response To Climate Changesupporting

confidence: 87%

Impact of climate change on tropospheric ozone and its global budgets

2008

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“…The exchange rate may be accelerated by greenhouse effects (15,16). However, a previous study shows that upward mass flux in the tropical lower stratosphere will increase to only two times the present-day value when pCO 2 is raised by four times, and a further increase in pCO 2 would not increase the exchange rate (15). Therefore, the enhancement of γ due to high pCO 2 should be limited.…”

Section: Resultsmentioning

confidence: 96%

Dynamic model constraints on oxygen-17 depletion in atmospheric O ₂ after a snowball Earth

Cao

Bao

2013

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

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A large perturbation in atmospheric CO 2 and O 2 or bioproductivity will result in a drastic pulse of 17 O change in atmospheric O 2 , as seen in the Marinoan Oxygen-17 Depletion (MOSD) event in the immediate aftermath of a global deglaciation 635 Mya. The exact nature of the perturbation, however, is debated. Here we constructed a coupled, four-box, and quick-response biosphereatmosphere model to examine both the steady state and dynamics of the MOSD event. Our model shows that the ultra-high CO 2 concentrations proposed by the "snowball' Earth hypothesis produce a typical MOSD duration of less than 10 6 y and a magnitude of 17 O depletion reaching approximately −35‰. Both numbers are in remarkable agreement with geological constraints from South China and Svalbard. Moderate CO 2 and low O 2 concentration (e.g., 3,200 parts per million by volume and 0.01 bar, respectively) could produce distinct sulfate 17 O depletion only if postglacial marine bioproductivity was impossibly low. Our dynamic model also suggests that a snowball in which the ocean is isolated from the atmosphere by a continuous ice cover may be distinguished from one in which cracks in the ice permit ocean-atmosphere exchange only if partial pressure of atmospheric O 2 is larger than 0.02 bar during the snowball period and records of weathering-derived sulfate are available for the very first few tens of thousands of years after the onset of the meltdown. In any case, a snowball Earth is a precondition for the observed MOSD event. (3,(6)(7)(8)(9). Available data show that for the past 750 My, tropospheric O 2 has had a small magnitude of 17 O depletion, except for one unusual episode: the immediate aftermath of the Marinoan glacial meltdown at 635 Mya, when the Δ 17 O O2 probably reached values as negative as ∼−40‰ (6), compared with the −0.34‰ in today's atmospheric O 2 (10). An ultra-high pCO 2 condition was proposed to explain this Marinoan Oxygen-17 Depletion (MOSD) event (3, 6), which is consistent with the "snowball" Earth hypothesis that argues for a completely icecovered globe lasting several million years (11,12). However, it is not known if there are other potential atmosphere-biosphere scenarios that might produce distinctively negative Δ 17 O O2 , such as a condition in which pCO 2 is moderate but pO 2 and/or biosphere O 2 flux are low, as proposed recently in an effort to reconcile organic and inorganic carbon isotope data from the postglacial cap carbonates (13). It therefore is imperative to examine the Δ 17 O O2 variability among geologically reasonable scenarios. Previous modeling studies on Δ 17 O O2 vary the ratio of pO 2 /pCO 2 , but with a fixed O 2 residence time, or focus on steady state without considering dynamic evolution of pO 2 , pCO 2 , or O 2 production fluxes (3, 13) or consider only minor Δ 17 O O2 difference between recent glacial and interglacial periods (14). In addition, a critical piece of information, the evolution of pO 2 before and after the meltdown of the most severe global glaciation in Earth history, w...

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“…Additionally, breaking planetary waves cause rapid isentropical, quasi-horizontal mixing in the lower stratosphere. This "surf zone" reaches from the subtropics to high latitudes (Holton et al, 1995) and combines fast meridional transport with the slow BDC (Butchart et al, 2006). This quasi-horizontal mixing is the main transport branch for the sulfate aerosol in the lower extratropical stratosphere.…”

Section: Circulation In the Stratospherementioning

confidence: 99%

Changing transport processes in the stratosphere by radiative heating of sulfate aerosols

2017

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Abstract. The injection of sulfur dioxide (SO 2 ) into the stratosphere to form an artificial stratospheric aerosol layer is discussed as an option for solar radiation management. Sulfate aerosol scatters solar radiation and absorbs infrared radiation, which warms the stratospheric sulfur layer. Simulations with the general circulation model ECHAM5-HAM, including aerosol microphysics, show consequences of this warming, including changes of the quasi-biennial oscillation (QBO) in the tropics. The QBO slows down after an injection of 4 Tg(S) yr −1 and completely shuts down after an injection of 8 Tg(S) yr −1 . Transport of species in the tropics and subtropics depends on the phase of the QBO. Consequently, the heated aerosol layer not only impacts the oscillation of the QBO but also the meridional transport of the sulfate aerosols. The stronger the injection, the stronger the heating and the simulated impact on the QBO and equatorial wind systems. With increasing injection rate the velocity of the equatorial jet streams increases, and the less sulfate is transported out of the tropics. This reduces the global distribution of sulfate and decreases the radiative forcing efficiency of the aerosol layer by 10 to 14 % compared to simulations with low vertical resolution and without generated QBO. Increasing the height of the injection increases the radiative forcing only for injection rates below 10 Tg(S) yr −1 (8-18 %), a much smaller value than the 50 % calculated previously. Stronger injection rates at higher levels even result in smaller forcing than the injections at lower levels.

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Simulations of anthropogenic change in the strength of the Brewer–Dobson circulation

Cited by 398 publications

References 46 publications

Impact of climate change on tropospheric ozone and its global budgets

Impact of climate change on tropospheric ozone and its global budgets

Dynamic model constraints on oxygen-17 depletion in atmospheric O ₂ after a snowball Earth

Changing transport processes in the stratosphere by radiative heating of sulfate aerosols

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Simulations of anthropogenic change in the strength of the Brewer–Dobson circulation

Cited by 398 publications

References 46 publications

Impact of climate change on tropospheric ozone and its global budgets

Impact of climate change on tropospheric ozone and its global budgets

Dynamic model constraints on oxygen-17 depletion in atmospheric O 2 after a snowball Earth

Changing transport processes in the stratosphere by radiative heating of sulfate aerosols

Contact Info

Product

Resources

About

Dynamic model constraints on oxygen-17 depletion in atmospheric O ₂ after a snowball Earth