Atmospheric CO2 during the Mid-Piacenzian Warm Period and the M2 glaciation

Vega, Elwyn de la; Chalk, Thomas B.; Wilson, Paul A.; Bysani, Ratna Priya; Foster, Gavin L

doi:10.1038/s41598-020-67154-8

Cited by 117 publications

(95 citation statements)

References 60 publications

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“…An increase in atmospheric CO 2 and seawater pCO 2 would result in an increase in DIC and consequently an increase in foraminifer Sr/Ca. Major changes in pCO 2 occurred between 3.2 and 2.5 Ma corresponding to the intensification of NHG at 2.7 Ma (de la Vega et al, 2020;Seki et al, 2010). However, long-term increase in Sr/Ca values ( Figure 4) do not correlate with reconstructed pCO 2 as they do not reveal any significant…”

Section: Preservation Of Samples and Terrestrial Inputmentioning

confidence: 95%

Deep Thermohaline Circulation Across the Closure of the Central American Seaway

Öğretmen

Schiebel

Jochum

et al. 2020

Paleoceanog and Paleoclimatol

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The closure of the Central American Seaway (CAS) resulted in changes of ocean‐climate dynamics since the late Miocene following the uplift of northern Andes. Reconstructing the bottom‐water temperatures (BWTs) of the Caribbean Sea illustrates feedbacks of the closure on the ocean‐climate system including deep‐water dynamics of the Caribbean Sea. Here, Mg/Ca‐derived BWTs of the Plio‐Pleistocene Caribbean Sea from the benthic foraminifer Cibicidoides wuellerstorfi are presented for the first time and interpreted along with Na/Ca and Sr/Ca as proxies of salinity and continental input, respectively. Our results highlight several warm (93, Gi15‐19, and N1) and cool (92, M2, Gi20, and CN4) marine isotope stages (MISs). Accordingly, changes in the circulation of deep‐water masses during the CAS closure developed in four main time intervals: (I) between 5.2 and 4.1 Ma (million years ago) BWT was ~1.1°C, (II) 4.1–3.2 Ma ~2.1°C, (III) 3.2–2.7 Ma ~2.7°C, and (IV) 2.7–2.2 Ma ~2.1°C. Relatively higher, gradually increased temperatures between 3.2 and 2.7 Ma correspond to late Pliocene warmth and restricted inflow of Pacific waters into the Caribbean due to shoaling of the CAS. In addition, Sr/Ca values reveal gradually escalating terrigenous input until 2.7 Ma most likely related to the increased river discharge in response to the Andean uplift. The gradual decrease of the BWTs from 2.7 Ma may have resulted from the onset of Northern Hemisphere Glaciation. Overall, BWTs match with previous sea surface temperatures from the planktic foraminifer Neogloboquadrina dutertrei. The BWTs presented here confirm intensified thermohaline circulation during the overall Pliocene warmth with increased bottom‐water Na/Ca values indicating enhanced salinity.

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Section: Preservation Of Samples and Terrestrial Inputmentioning

confidence: 95%

Deep Thermohaline Circulation Across the Closure of the Central American Seaway

Öğretmen

Schiebel

Jochum

et al. 2020

Paleoceanog and Paleoclimatol

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“…such as long-term global cooling (Herbert et al, 2010;Ravelo et al, 2004) and declining atmospheric CO 2 levels (Bartoli et al, 2011;De La Vega et al, 2020;Martínez-Botí et al, 2015).…”

Section: 1029/2019pa003804mentioning

confidence: 99%

A Ternary Mixing Model Approach Using Benthic Foraminifer δ¹³C‐δ¹⁸O Data to Reconstruct Late Pliocene Deep Atlantic Water Mass Mixing

Weijst

Winkelhorst

Lourens

et al. 2020

Paleoceanog and Paleoclimatol

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Late Pliocene deep Atlantic δ 13 C data have been interpreted as evidence for enhanced Atlantic Meridional Overturning Circulation (AMOC) compared to the present, but this hypothesis is not supported by the Pliocene Model Intercomparison Project (PlioMIP). Here, we adopt a new approach to assess variability in deep ocean circulation based on paired stable carbon (δ 13 C) and oxygen isotopes (δ 18 O) of benthic foraminifera, both (semi)conservative water mass tracers. Assuming that deep Atlantic benthic δ 13 C-δ 18 O variability is predominantly driven by mixing, we extrapolate the δ 13 C-δ 18 O data outside the sampled range to identify the end-members. At least three end-members are needed to explain the spatial δ 13 C-δ 18 O variability in the deep North Atlantic Ocean: two Northern Component Water (NCW) and one Southern Component Water (SCW) water masses. We use a ternary mixing model to quantify the mixing proportions between SCW and NCW in the deep Atlantic Ocean. Our analysis includes new data from Ocean Drilling Program Sites 959 and 662 in the eastern equatorial Atlantic and suggests that the AMOC cell was deeper during the M2 glacial than during late Pliocene interglacials. Moreover, we identify a new cold and well-ventilated water mass that was geographically restricted to the southeast Atlantic Ocean between 3.6 and 2.7 Ma and did not contribute significantly to the δ 13 C-δ 18 O variability of the rest of the basin. This high-δ 13 C high-δ 18 O water mass has led to the misconception of a reduced latitudinal δ 13 C gradient. Our analyses show that the late Pliocene δ 13 C gradient between NCW and SCW was similar to the present-day value of 1.1‰.

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“…The Pliocene (5.33-2.58 Ma) is the most recent geological epoch with substantially higher greenhouse gas concentrations (De et al, 2020;Martínez-Botí et al, 2015;Stap et al, 2016) and elevated global surface temperatures (Brierley et al, 2009;Dowsett et al, 2016;McClymont et al, 2020) compared to preindustrial times. This makes it an interesting interval to study for its potential analogies with our future climate (Burke et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Early Pliocene deepening of the tropical Atlantic thermocline

Weijst

Winkelhorst

Heydt

et al. 2020

Preprint

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Abstract. The tropical thermocline may have played a crucial role in maintaining weaker sea surface temperature gradients during the early Pliocene and in the onset of late Pliocene northern hemisphere glaciation. Whereas the Pliocene Pacific thermocline evolution is well documented, complete records of Pliocene tropical Atlantic thermocline depths are limited to the Caribbean region. Here, we use the oxygen isotope gradient between surface to subsurface dwelling planktic foraminifera from Ocean Drilling Program Site 959 in the eastern equatorial Atlantic to track vertical changes in thermocline depth over the course of the Pliocene. This record shows that eastern equatorial Atlantic thermocline depth varied substantially during the early Pliocene, before finally deepening abruptly around 4.5 Ma to remain relatively stable until at least 2.8 Ma. Eastern equatorial Atlantic and Caribbean records are almost identical, suggesting a common control on the sudden step-wise thermocline deepening across the basin, in contrast to previous assumptions. The Pliocene evolution of the tropical Atlantic thermocline differs is remarkably from the Pacific, which is characterized by gradual basin-wide shoaling. It remains unclear what mechanisms were involved in the dichotomous thermocline evolutions. Whereas Central American Seaway closure may have shoaled the Pacific thermocline, it is not yet understood if and how this process may have deepened the Atlantic thermocline. A divergent evolution of temperatures of the source regions may explain the opposite thermocline developments observed, possibly amplified by a positive feedback loop involving tropical cyclone intensity.

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Atmospheric CO2 during the Mid-Piacenzian Warm Period and the M2 glaciation

Cited by 117 publications

References 60 publications

Deep Thermohaline Circulation Across the Closure of the Central American Seaway

Deep Thermohaline Circulation Across the Closure of the Central American Seaway

A Ternary Mixing Model Approach Using Benthic Foraminifer δ¹³C‐δ¹⁸O Data to Reconstruct Late Pliocene Deep Atlantic Water Mass Mixing

Early Pliocene deepening of the tropical Atlantic thermocline

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Atmospheric CO2 during the Mid-Piacenzian Warm Period and the M2 glaciation

Cited by 117 publications

References 60 publications

Deep Thermohaline Circulation Across the Closure of the Central American Seaway

Deep Thermohaline Circulation Across the Closure of the Central American Seaway

A Ternary Mixing Model Approach Using Benthic Foraminifer δ13C‐δ18O Data to Reconstruct Late Pliocene Deep Atlantic Water Mass Mixing

Early Pliocene deepening of the tropical Atlantic thermocline

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A Ternary Mixing Model Approach Using Benthic Foraminifer δ¹³C‐δ¹⁸O Data to Reconstruct Late Pliocene Deep Atlantic Water Mass Mixing