Competition between ocean carbon pumps in simulations with varying Southern Hemisphere westerly wind forcing

Huiskamp, Willem; Meißner, Katrin J.; d’Orgeville, Marc

doi:10.1007/s00382-015-2781-0

Cited by 10 publications

(15 citation statements)

References 49 publications

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“…Significant weakening of AABW during the LIG due to Antarctic meltwater discharge has previously been inferred from paleo-proxy records (Hayes et al, 2014;Rohling et al, 2019). A shift in westerlies might also contribute to a weakening of the AABW (Menviel et al, 2008;Huiskamp et al, 2016;Glasscock et al, 2020). The reduced upwelling south of 55 • S and weaker AABW transport simulated here lead to an increased sequestration of DIC in the deep ocean, through an increase in the efficiency of the biological pump (Fig.…”

Section: Discussionsupporting

confidence: 66%

“…Numerical studies have unequivocally shown the impact of changes in the magnitude of the westerlies on the carbon cycle, with stronger westerlies leading to increased upwelling and SO outgassing, and vice-versa (e.g., Menviel et al, 2008;d'Orgeville et al, 2010;Lauderdale et al, 2013;Huiskamp et al, 2016;Lauderdale et al, 2017;Menviel et al, 2018;Gottschalk et al, 2019), however, the impact of changes in the latitudinal position of the westerlies on the carbon cycle is less certain (e.g., d 'Orgeville et al, 2010;Völker and Köhler, 2013;Lauderdale et al, 2013;Huiskamp et al, 2016). Given the simulated increase in DIC content in the deeper SO and the reduced DIC at the surface of the SO, our simulations suggest that the simulated equatorward shift of the westerlies reduces the SO CO 2 outgassing.…”

Section: Discussionmentioning

confidence: 99%

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Marine carbon cycle response to a warmer Southern Ocean: the case of the Last Interglacial

Choudhury

Menviel

Meißner

et al. 2021

Preprint

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Abstract. Recent studies investigating future warming scenarios have shown that the ocean carbon sink will weaken over the coming century due to ocean warming and changes in oceanic circulation. However, significant uncertainties remain regarding the magnitude of the oceanic carbon cycle response to warming. Here, we investigate the Southern Ocean’s (SO, south of 40° S) carbon cycle response to warmer conditions, as simulated under Last Interglacial boundary conditions (LIG, 129–115 thousand years ago, ka). We find a ∼150 % increase in carbon dioxide (CO2) outgassing over the SO at the LIG compared to pre-industrial (PI), due to a 0.5 °C increase in SO sea surface temperatures. This is partly compensated by an equatorward shift of the Southern Hemisphere westerlies and weaker Antarctic Bottom Water formation, which lead to an increase in dissolved inorganic carbon (DIC) in the deep ocean at the LIG compared to PI. These deep ocean DIC changes arise from increased deep and bottom water residence times, and higher remineralization rates due to higher temperatures. While our LIG simulation features a large reduction in SO sea-ice compared to PI, we find that changes in sea ice extent exert a minor control on the marine carbon cycle. Our results thus suggest that the projected poleward intensification of the SH westerlies, coupled with warmer conditions at the surface of the SO would weaken the SO carbon uptake over the coming century.

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Section: Discussionsupporting

confidence: 66%

Section: Discussionmentioning

confidence: 99%

Marine carbon cycle response to a warmer Southern Ocean: the case of the Last Interglacial

Choudhury

Menviel

Meißner

et al. 2021

Preprint

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“…This clockwise overturning introduces the dropping atmospheric temperature anomaly into the shallow North Pacific. At year 150, the largest carbon anomalies are near the surface and in the deep South Pacific, partly due to these being the first regions to exchange carbon with the atmosphere (though lateral advection and adjustment of ocean carbon pumps also have a role in response; Huiskamp et al 2016Huiskamp et al , Ödalen et al 2018. Rapidly accelerating anti-clockwise overturning in the deep Pacific has little effect on temperature until near the end of the simulation, but it has a large effect on DIC, as carbon-rich deep water is flushed upward.…”

Section: Response Of Ocean Heat and Carbon Storage To Changes In Circmentioning

confidence: 99%

Asymmetric dynamical ocean responses in warming icehouse and cooling greenhouse climates

Kvale

Turner

Keller

et al. 2018

Environ. Res. Lett.

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Warm periods in Earth's history tend to cool more slowly than cool periods warm. Here we explore initial differences in how the global ocean takes up and gives up heat and carbon in forced rapid warming and cooling climate scenarios. We force an intermediate-complexity earth system model using two atmospheric CO 2 scenarios. A ramp-up (1% per year increase in atmospheric CO 2 for 150 years) starts from an average global CO 2 concentration of 285 ppm to represent warming of an icehouse climate. A ramp-down (1% per year decrease in atmospheric CO 2 for 150 years) starts from an average global CO 2 concentration of 1257 ppm to represent cooling of a greenhouse climate. Atmospheric CO 2 is then held constant in each simulation and the model is integrated an additional 350 years. The ramp-down simulation shows a weaker response of surface air temperature to changes in radiative forcing relative to the ramp-up scenario. This weaker response is due to a relatively large and fast release of heat from the ocean to the atmosphere. This asymmetry in heat exchange in cooling and warming scenarios exists mainly because of differences in the response of the ocean circulation to forcing. In the ramp-up, increasing stratification and weakening of meridional overturning circulation slows ocean heat and carbon uptake. In the ramp-down, cooling accelerates meridional overturning and deepens vertical mixing, accelerating the release of heat and carbon stored at depth. Though idealized, our experiments offer insight into differences in ocean dynamics in icehouse and greenhouse climate transitions.

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“…Instrumental reconstructions of the SAM extend as far back as 1865 (Jones et al, 2009), but those for periods prior to the mid-twentieth century involve significant uncertainty due to fewer observations and the methods used to compensate for this (i.e. estimates based on atmospheric conservation of mass, e.g.…”

Section: Introductionmentioning

confidence: 99%

Quantifying Southern Annular Mode paleo-reconstruction skill in a model framework

Huiskamp

McGregor

2021

Clim. Past

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Abstract. Past attempts to reconstruct the Southern Annular Mode (SAM) using paleo-archives have resulted in records which can differ significantly from one another prior to the window over which the proxies are calibrated. This study attempts to quantify not only the skill with which we may expect to reconstruct the SAM but also to assess the contribution of regional bias in proxy selection and the impact of non-stationary proxy–SAM teleconnections on a resulting reconstruction. This is achieved using a pseudoproxy framework with output from the GFDL CM2.1 global climate model. Reconstructions derived from precipitation fields perform better, with 89 % of the reconstructions calibrated over a 61 year window able to reproduce at least 50 % of the inter-annual variance in the SAM, as opposed to just 25 % for surface air temperature (SAT)-derived reconstructions. Non-stationarity of proxy–SAM teleconnections, as defined here, plays a small role in reconstructions, but the range in reconstruction skill is not negligible. Reconstructions are most likely to be skilful when proxies are sourced from a geographically broad region with a network size of at least 70 proxies.

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Competition between ocean carbon pumps in simulations with varying Southern Hemisphere westerly wind forcing

Cited by 10 publications

References 49 publications

Marine carbon cycle response to a warmer Southern Ocean: the case of the Last Interglacial

Marine carbon cycle response to a warmer Southern Ocean: the case of the Last Interglacial

Asymmetric dynamical ocean responses in warming icehouse and cooling greenhouse climates

Quantifying Southern Annular Mode paleo-reconstruction skill in a model framework

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