Arctic closure as a trigger for Atlantic overturning at the Eocene-Oligocene Transition

Hutchinson, David K.; Coxall, Helen; OʹRegan, Matt; Nilsson, Johan; Caballero, Rodrigo; Boer, Agatha M. de

doi:10.1038/s41467-019-11828-z

Cited by 72 publications

(113 citation statements)

References 61 publications

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“…Nevertheless, despite there being virtually no overflow, the AMOC remains relatively strong as a result of active deep-water formation south of the GSR. These results support our conclusion that GSR sill-depth changes are not likely the primary driver of AMOC variations and changes in global climate during the Cenozoic (see also Hutchinson et al 2019).…”

Section: A the Relationship Between Gsr Height And Amoc Strengthsupporting

confidence: 90%

“…Hence, when the GSR is present, deep convection occurs both in the polar basin (albeit weaker) and the subpolar North Atlantic. A similar response was found in a recent modeling study, using late Eocene boundary conditions (Hutchinson et al 2019), demonstrating that deep water formation shifted to the south of the GSR in response to a shoaling of the sill from 500 to 25 m. They also suggest that the Arctic-Atlantic freshwater transport may be critical in determining the location of deep-water formation, including the preferred basin of sinking (i.e., Atlantic vs Pacific sinking).…”

Section: E High-latitude and Global Surface Climate Responsesupporting

confidence: 83%

“…This builds on previous work by Ferreira et al (2010). We note, however, that the present study provides valuable insight into understanding Cenozoic climate evolution, where Arctic-Atlantic gateway changes are likely to have played a major role (Stärz et al 2017;Hutchinson et al 2019).…”

Section: Introductionsupporting

confidence: 76%

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Topological Constraints by the Greenland–Scotland Ridge on AMOC and Climate

2020

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Changes in the geometry of ocean basins have been influential in driving climate change throughout Earth’s history. Here, we focus on the emergence of the Greenland–Scotland Ridge (GSR) and its influence on the ocean state, including large-scale circulation, heat transport, water mass properties, and global climate. Using a coupled atmosphere–ocean–sea ice model, we consider the impact of introducing the GSR in an idealized Earth-like geometry, comprising a narrow Atlantic-like basin and a wide Pacific-like basin. Without the GSR, deep-water formation occurs near the North Pole in the Atlantic basin, associated with a deep meridional overturning circulation (MOC). By introducing the GSR, the volume transport across the sill decreases by 64% and deep convection shifts south of the GSR, dramatically altering the structure of the high-latitude MOC. Due to compensation by the subpolar gyre, the northward ocean heat transport across the GSR only decreases by ~30%. As in the modern Atlantic Ocean, a bidirectional circulation regime is established with warm Atlantic water inflow and a cold dense overflow across the GSR. In sharp contrast to the large changes north of the GSR, the strength of the Atlantic MOC south of the GSR is unaffected. Outside the high latitudes of the Atlantic basin, the surface climate response is surprisingly small, suggesting that the GSR has little impact on global climate. Our results suggest that caution is required when interpreting paleoproxy and ocean records, which may record large local changes, as indicators of basin-scale changes in the overturning circulation and global climate.

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Section: A the Relationship Between Gsr Height And Amoc Strengthsupporting

confidence: 90%

Section: E High-latitude and Global Surface Climate Responsesupporting

confidence: 83%

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Topological Constraints by the Greenland–Scotland Ridge on AMOC and Climate

2020

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“…The use of an adequate paleogeography is particularly important, as it impacts ocean circulation and properties (e.g., temperature and salinity distribution; see Yang et al, 2014;Zhang et al, 2010). For instance, the closure of the Central American Seaway and the Arctic Ocean and the subsidence of the Greenland Scotland Ridge have been described as causal mechanisms for NADW onset because of their impact on North Atlantic salinity (e.g., Abelson & Erez, 2017;Hutchinson et al, 2018Hutchinson et al, , 2019Ladant et al, 2018;Mikolajewicz et al, 1993;Sepulchre et al, 2014;Stärz et al, 2017). Experiments with the UVic intermediate complexity model (energy balanced model for atmosphere) and increased pCO 2 alone still describe a strong impact of DP opening on ocean meridional overturning circulation and climate, notably on surface temperatures (Sijp et al, 2009(Sijp et al, , 2011.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the Effect of the Drake Passage Opening on the Eocene Ocean

Toumoulin

Donnadieu

Ladant

et al. 2020

Paleoceanog and Paleoclimatol

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The opening of the Drake Passage (DP) during the Cenozoic is a tectonic event of paramount importance for the development of modern ocean characteristics. Notably, it has been suggested that it exerts a primary role in the onset of the Antarctic Circumpolar Current (ACC) formation, in the cooling of high‐latitude South Atlantic waters and in the initiation of North Atlantic Deep Water (NADW) formation. Several model studies have aimed to assess the impacts of DP opening on climate, but most of them focused on surface climate, and only few used realistic Eocene boundary conditions. Here, we revisit the impact of the DP opening on ocean circulation with the IPSL‐CM5A2 Earth System Model. Using appropriate middle Eocene (40 Ma) boundary conditions, we perform and analyze simulations with different depths of the DP (0, 100, 1,000, and 2,500 m) and compare results to existing geochemical data. Our experiments show that DP opening has a strong effect on Eocene ocean structure and dynamics even for shallow depths. The DP opening notably allows the formation of a proto‐ACC and induces deep ocean cooling of 1.5°C to 2.5°C in most of the Southern Hemisphere. There is no NADW formation in our simulations regardless of the depth of the DP, suggesting that the DP on its own is not a primary control of deepwater formation in the North Atlantic. This study elucidates how and to what extent the opening of the DP contributed to the establishment of the modern global thermohaline circulation.

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“…Hutchinson et al (2018Hutchinson et al ( , 2019. The ocean component uses the modular ocean model (MOM) version 5.1.0, while the other components of the model are the same as in CM2.1; Atmosphere Model 2, Land Model 2 and the Sea Ice Simulator 1.…”

mentioning

confidence: 99%

DeepMIP: Model intercomparison of early Eocene climatic optimum (EECO) large-scale climate features and comparison with proxy data

Lunt¹,

Bragg²,

Chan³

et al. 2020

Preprint

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Abstract. We present results from an ensemble of seven climate models, each of which has carried out simulations of the early Eocene climate optimum (EECO, ~ 50 million years ago). These simulations have been carried out in the framework of DeepMIP (www.deepmip.org), and as such all models have been configured with identical paleogeographic and vegetation boundary conditions. The results indicate that these non-CO2 boundary conditions contribute between 3 and 5 °C to Eocene warmth. Compared to results from previous studies, the DeepMIP simulations show reduced spread of global mean surface temperature response across the ensemble, for a given atmospheric CO2 concentration. In a marked departure from the results from previous simulations, at least two of the DeepMIP models (CESM and GFDL) are consistent with proxy indicators of global mean temperature, and atmospheric CO2, and meridional SST gradients. The best agreement with global SST proxies from these models occurs at CO2 concentrations of around 2400 ppmv. At a more regional scale the models lack skill in reproducing the proxy SSTs, in particular in the southwest Pacific, around New Zealand and south Australia, where the modelled anomalies are substantially less than indicated by the proxies. However, in these regions modelled continental surface air temperature anomalies are consistent with surface air temperature proxies, implying an inconsistency between marine and terrestrial temperatures in either the proxies or models in this region. Our aim is that the documentation of the large scale features and model-data comparison presented herein will pave the way to further studies that explore aspects of the model simulations in more detail, for example the ocean circulation, hydrological cycle, and modes of variability; and encourage sensitivity studies to aspects such as paleogeography and aerosols.

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Arctic closure as a trigger for Atlantic overturning at the Eocene-Oligocene Transition

Cited by 72 publications

References 61 publications

Topological Constraints by the Greenland–Scotland Ridge on AMOC and Climate

Topological Constraints by the Greenland–Scotland Ridge on AMOC and Climate

Quantifying the Effect of the Drake Passage Opening on the Eocene Ocean

DeepMIP: Model intercomparison of early Eocene climatic optimum (EECO) large-scale climate features and comparison with proxy data

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