Impact of brine-induced stratification on the glacial carbon cycle

Bouttes, Nathaëlle; Paillard, Didier; Roche, Didier M.

doi:10.5194/cp-6-575-2010

Cited by 101 publications

(112 citation statements)

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“…This mechanism was shown to result in a net glacial CO 2 decrease. Previous studies also showed that frac = 0.6 is a good estimate (Bouttes et al, 2010(Bouttes et al, , 2011. In this study the frac parameter is thus set to 0.6 when the sinking of brines is taken into account.…”

Section: Sinking Of Brines In Climber-2mentioning

confidence: 99%

“…1c). We then explore the impact of the same fresh water fluxes in a situation with more realistic glacial CO 2 levels obtained including the "brine sinking" mechanism previously studied (Bouttes et al, 2010(Bouttes et al, , 2011. Finally, we evaluate the impact of adding fresh water flux to the Southern Ocean.…”

Section: N Bouttes Et Al: Fresh Water Fluxes Impact On the Carbon Cmentioning

confidence: 99%

“…Yet, as brines are very dense because of their high salt content, they should rapidly sink to the deep ocean when the local conditions allow this. To avoid the dilution of such an effect, the brine sink has been previously parameterized and studied in CLIMBER-2 (Bouttes et al, 2010(Bouttes et al, , 2011. These studies focused on the Southern Ocean where the interactions with the continental shelves are important; hence no sinking of brines is considered in the Northern Hemisphere.…”

Section: Sinking Of Brines In Climber-2mentioning

confidence: 99%

“…The model computes the carbon cycle both in the ocean and on land, and takes into account carbonate compensation. It has already been used for a number of studies on the links between the climate and the carbon cycle (Brovkin et al, 2002(Brovkin et al, , 2007Bouttes et al, 2010Bouttes et al, , 2011.…”

Section: Climber-2 Climate-carbon Modelmentioning

confidence: 99%

“…The LGM climate is obtained by modifying the orbital parameters (Berger, 1978), ice sheets (Peltier, 2004), sea level (Waelbroeck et al, 2002) and atmospheric CO 2 (Monnin et al, 2001) for the radiative code. As done in previous studies (Brovkin et al, 2002(Brovkin et al, , 2007Bouttes et al, 2010Bouttes et al, , 2011, the radiative CO 2 is imposed so as to obtain a glacial climate. CH 4 and N 2 O are not explicitly considered in the model, but the CO 2 is an "equivalent CO 2 " calculated to reproduce the cumulative radiative effect arising from the changes in CO 2 , CH 4 and N 2 O (Brovkin et al, 2007).…”

Section: Design Of Experimentsmentioning

confidence: 99%

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Systematic study of the impact of fresh water fluxes on the glacial carbon cycle

2012

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Abstract. During glacial periods, atmospheric CO 2 concentration increases and decreases by around 15 ppm. At the same time, the climate changes gradually in Antarctica. Such climate changes can be simulated in models when the AMOC (Atlantic Meridional Oceanic Circulation) is weakened by adding fresh water to the North Atlantic. The impact on the carbon cycle is less straightforward, and previous studies give opposite results. Because the models and the fresh water fluxes were different in these studies, it prevents any direct comparison and hinders finding whether the discrepancies arise from using different models or different fresh water fluxes.In this study we use the CLIMBER-2 coupled climate carbon model to explore the impact of different fresh water fluxes. In both preindustrial and glacial states, the addition of fresh water and the resulting slow-down of the AMOC lead to an uptake of carbon by the ocean and a release by the terrestrial biosphere. The duration, shape and amplitude of the fresh water flux all have an impact on the change of atmospheric CO 2 because they modulate the change of the AMOC. The maximum CO 2 change linearly depends on the time integral of the AMOC change. The different duration, amplitude, and shape of the fresh water flux cannot explain the opposite evolution of ocean and vegetation carbon inventory in different models. The different CO 2 evolution thus depends on the AMOC response to the addition of fresh water and the resulting climatic change, which are both model dependent. In CLIMBER-2, the rise of CO 2 recorded in ice cores during abrupt events can be simulated under glacial conditions, especially when the sinking of brines in the Southern Ocean is taken into account. The addition of fresh water in the Southern Hemisphere leads to a decline of CO 2 , contrary to the addition of fresh water in the Northern Hemisphere.

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Section: Sinking Of Brines In Climber-2mentioning

confidence: 99%

Section: N Bouttes Et Al: Fresh Water Fluxes Impact On the Carbon Cmentioning

confidence: 99%

Section: Sinking Of Brines In Climber-2mentioning

confidence: 99%

Section: Climber-2 Climate-carbon Modelmentioning

confidence: 99%

Section: Design Of Experimentsmentioning

confidence: 99%

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Systematic study of the impact of fresh water fluxes on the glacial carbon cycle

2012

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Deep water formation in the North Pacific and deglacial CO₂rise

et al. 2014

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Deep water formation in the North Atlantic and Southern Ocean is widely thought to influence deglacial CO 2 rise and climate change; here we suggest that deep water formation in the North Pacific may also play an important role. We present paired radiocarbon and boron isotope data from foraminifera from sediment core MD02-2489 at 3640 m in the North East Pacific. These show a pronounced excursion during Heinrich Stadial 1, with benthic-planktic radiocarbon offsets dropping to~350 years, accompanied by a decrease in benthic δ 11 B. We suggest that this is driven by the onset of deep convection in the North Pacific, which mixes young shallow waters to depth, old deep waters to the surface, and low-pH water from intermediate depths into the deep ocean. This deep water formation event was likely driven by an increase in surface salinity, due to subdued atmospheric/monsoonal freshwater flux during Heinrich Stadial 1. The ability of North Pacific Deep Water (NPDW) formation to explain the excursions seen in our data is demonstrated in a series of experiments with an intermediate complexity Earth system model. These experiments also show that breakdown of stratification in the North Pacific leads to a rapid~30 ppm increase in atmospheric CO 2 , along with decreases in atmospheric δ 13 C and Δ 14 C, consistent with observations of the early deglaciation. Our inference of deep water formation is based mainly on results from a single sediment core, and our boron isotope data are unavoidably sparse in the key HS1 interval, so this hypothesis merits further testing. However, we note that there is independent support for breakdown of stratification in shallower waters during this period, including a minimum in δ 15 N, younging in intermediate water 14 C, and regional warming. We also re-evaluate deglacial changes in North Pacific productivity and carbonate preservation in light of our new data and suggest that the regional pulse of export production observed during the Bølling-Allerød is promoted by relatively stratified conditions, with increased light availability and a shallow, potent nutricline. Overall, our work highlights the potential of NPDW formation to play a significant and hitherto unrealized role in deglacial climate change and CO 2 rise.

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Control of the glacial carbon budget by topographically induced mixing

Boer

Hogg

2014

Geophysical Research Letters

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Evidence for the oceanic uptake of atmospheric CO 2 during glaciations suggests that there was less production of southern origin deep water but, paradoxically, a larger volume of southern origin water than today. Here we demonstrate, using a theoretical box model, that the inverse relationship between volume and production rate of this water mass can be explained by invoking mixing rates in the deep ocean that are proportional to topographic outcropping area scaled with ocean floor slope. Furthermore, we show that the resulting profile, of a near-linear decrease in mixing intensity away from the bottom, generates a positive feedback on CO 2 uptake that can initiate a glacial cycle. The results point to the importance of using topography-dependent mixing when studying the large-scale ocean circulation, especially in the paleo-intercomparison models that have failed to produce the weaker and more voluminous bottom water of the Last Glacial Maximum.

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Impact of brine-induced stratification on the glacial carbon cycle

Cited by 101 publications

References 56 publications

Systematic study of the impact of fresh water fluxes on the glacial carbon cycle

Systematic study of the impact of fresh water fluxes on the glacial carbon cycle

Deep water formation in the North Pacific and deglacial CO₂rise

Control of the glacial carbon budget by topographically induced mixing

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Impact of brine-induced stratification on the glacial carbon cycle

Cited by 101 publications

References 56 publications

Systematic study of the impact of fresh water fluxes on the glacial carbon cycle

Systematic study of the impact of fresh water fluxes on the glacial carbon cycle

Deep water formation in the North Pacific and deglacial CO2rise

Control of the glacial carbon budget by topographically induced mixing

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Resources

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Deep water formation in the North Pacific and deglacial CO₂rise