The Impact of Stratospheric Ozone Recovery on the Southern Hemisphere Westerly Jet

Son, Seung Woo; Polvani, Lorenzo M.; Waugh, Darryn W.; Akiyoshi, Hideharu; García, Rolando R.; Kinnison, D. E.; Pawson, Steven; Rozanov, Eugene; Shepherd, T. G.; Shibata, Kiyotaka

doi:10.1126/science.1155939

Cited by 331 publications

(356 citation statements)

References 17 publications

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“…If, as recently suggested [Son et al, 2008], ozone depletion is the primary cause of wind speed increases, then this cloud forcing acts as a positive feedback on the ozone induced cooling. It more than doubles the negative radiative forcing from stratospheric ozone loss and suggests that future ozone recovery would cause a positive radiative forcing.…”

Section: Discussionmentioning

confidence: 99%

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Aerosol climate feedback due to decadal increases in Southern Hemisphere wind speeds

Korhonen

Carslaw

Forster

et al. 2010

Geophysical Research Letters

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[1] Observations indicate that the westerly jet in the Southern Hemisphere troposphere is accelerating. Using a global aerosol model we estimate that the increase in wind speed of 0.45 ± 0.2 m s À1 decade À1 at 50-65°S since the early 1980s caused a higher sea spray flux, resulting in an increase of cloud condensation nucleus concentrations of more than 85% in some regions, and of 22% on average between 50 and 65°S. These fractional increases are similar in magnitude to the decreases over many northern hemisphere land areas due to changes in air pollution over the same period. The change in cloud drop concentrations causes an increase in cloud reflectivity and a summertime radiative forcing between at 50 and 65°S comparable in magnitude but acting against that from greenhouse gas forcing over the same time period, and thus represents a substantial negative climate feedback. However, recovery of Antarctic ozone depletion in the next two decades will likely cause a fall in wind speeds, a decrease in cloud drop concentration and a correspondingly weaker cloud feedback. Citation: Korhonen, H., K. S. Carslaw, P. M.Forster, S. Mikkonen, N. D. Gordon, and H. Kokkola (2010), Aerosol climate feedback due to decadal increases in Southern Hemisphere wind speeds, Geophys. Res. Lett.,

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Section: Discussionmentioning

confidence: 99%

“…An analysis of SH climate shows significant changes in the Southern Annular Mode over recent decades [Thompson and Solomon, 2002;Son et al, 2008]. These changes have been attributed mainly to stratospheric ozone loss [Yang et al, 2007] but also to increases in greenhouse gases [Fyfe et al, 1999].…”

Section: Introductionmentioning

confidence: 99%

Aerosol climate feedback due to decadal increases in Southern Hemisphere wind speeds

Korhonen

Carslaw

Forster

et al. 2010

Geophysical Research Letters

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“…Recently, Perlwitz et al [2008] and Son et al [2008] demonstrated the advantage of using coupled chemistry climate models (CCMs) to simulate the impacts of stratospheric ozone changes on the circulation of the Southern Hemisphere. CCMs are relatively new tools that include global dynamics and radiation as well as fully interactive stratospheric ozone chemistry, thereby simulating both ozone's influence on the atmospheric circulation and the circulation's (including transport of ozone from midlatitudes) influence on ozone concentrations.…”

Section: Introductionmentioning

confidence: 99%

Intra‐annual relationships between polar ozone and the SAM

Fogt

Perlwitz

Pawson

et al. 2009

Geophysical Research Letters

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[1] Observed co-variations between polar total column ozone and the Southern Hemisphere Annular Mode (SAM) during 1962 -2004 are presented and evaluated in a chemistry-climate model (CCM). Results show that austral spring total column ozone variability at South Pole is significantly related to the SAM, perhaps up to four months later; this relationship is only seen in simulations that include ozone depletion. The austral spring SAM also is linked to following late spring -early summer total column ozone over the polar cap, since both respond to the wavedriving of the stratosphere. Overall, the CCM captures many of the observed ozone-SAM links, but over-predicts the relationship between spring ozone and austral summer SAM, as a consequence of the delayed breakdown of the polar vortex in the CCM.

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“…Because the ventilation of SAMW and CDW occurs on decadal and longer time scales, a lag between peak ozone forcing and maximum changes in ocean ventilation is expected (9). As stratospheric ozone recovers over the next 40 to 60 years, the recent trend of intensifying summer westerly winds may slow or reverse (6,27,28). However, continued increases in greenhouse gases will likely lead to strengthened westerlies during other seasons.…”

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confidence: 99%

Recent Changes in the Ventilation of the Southern Oceans

Waugh

Primeau

DeVries

et al. 2013

Science

150

166

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Surface westerly winds in the Southern Hemisphere have intensified over the past few decades, primarily in response to the formation of the Antarctic ozone hole, and there is intense debate on the impact of this on the ocean's circulation and uptake and redistribution of atmospheric gases. We used measurements of chlorofluorocarbon-12 (CFC-12) made in the southern oceans in the early 1990s and mid-to late 2000s to examine changes in ocean ventilation. Our analysis of the CFC-12 data reveals a decrease in the age of subtropical subantarctic mode waters and an increase in the age of circumpolar deep waters, suggesting that the formation of the Antarctic ozone hole has caused large-scale coherent changes in the ventilation of the southern oceans.T he transport of surface waters into the interior ("ventilation") of the southern oceans plays an important role in global climate and the cycling of carbon, oxygen, and nutrients in the oceans (1-3). Over the past few decades, the southern oceans have warmed at roughly twice the rate of the global mean ocean (1), and around 40% of the anthropogenic carbon in the oceans entered south of 40°S (4). Southern ocean ventilation is driven primarily by the westerly winds (5), which have strengthened and shifted poleward over recent decades, primarily as a consequence of Antarctic stratospheric ozone depletion (6). Modeling studies suggest that this has caused changes in the ocean's overturning circulation (7-9), and carbon uptake (10, 11). However, the sensitivity of the southern ocean circulation and ventilation to decadal changes in wind stresses is under debate (12)(13)(14).Information on ventilation rates can be obtained from measurements of chlorofluorocarbons (CFCs). These compounds are conserved within the oceans, and their atmospheric concentrations have increased rapidly from when they were first produced in the 1930s until the mid1990s ( fig. S1). Because of this time dependence, CFC measurements can provide constraints on the rates and pathways of ocean transport (15, 16).We used CFC-12 measurements made along several sections in the southern oceans in the early 1990s as part of the World Ocean Circulation Experiment (WOCE) and resampled in mid-to late 2000s as part of the Climate Variability and Predictability (CLIVAR) and CO 2 repeat hydrography program (supplementary materials) to examine changes in the ventilation of the southern oceans over the past two decades.The measurements during WOCE show largest pCFC-12 at the surface, with values decreasing with depth along isopycnals (e.g., Fig. 1A). [We express the measurements as the partial pressure of CFC-12 ( pCFC-12), defined as the seawater concentration divided by the solubility (16). This enables direct comparison with the atmospheric history of CFC-12.] The repeat occupations 14 to 16 years later show large increases in pCFC-12 in the subtropical thermocline (~25°t o 45°S, 200 to 1000 m), which correspond to the waters formed by the transport of surface waters along surfaces of constant density (e.g., Fig. 1B). ...

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The Impact of Stratospheric Ozone Recovery on the Southern Hemisphere Westerly Jet

Cited by 331 publications

References 17 publications

Aerosol climate feedback due to decadal increases in Southern Hemisphere wind speeds

Aerosol climate feedback due to decadal increases in Southern Hemisphere wind speeds

Intra‐annual relationships between polar ozone and the SAM

Recent Changes in the Ventilation of the Southern Oceans

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