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Evaluating climatic response to external radiative forcing during the late Miocene to early Pliocene: New perspectives from eastern equatorial Pacific (IODP U1338) and North Atlantic (ODP 982) locations

Drury, AJ; John, CM; Shevenell, AE; (2016) Evaluating climatic response to external radiative forcing during the late Miocene to early Pliocene: New perspectives from eastern equatorial Pacific (IODP U1338) and North Atlantic (ODP 982) locations. Paleoceanography , 31 (1) pp. 167-184. 10.1002/2015PA002881. Green open access

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Abstract

Orbital‐scale climate variability during the latest Miocene‐early Pliocene is poorly understood due to a lack of high‐resolution records spanning 8.0–3.5 Ma, which resolve all orbital cycles. Assessing this variability improves understanding of how Earth's system sensitivity to insolation evolves and provides insight into the factors driving the Messinian Salinity Crisis (MSC) and the Late Miocene Carbon Isotope Shift (LMCIS). New high‐resolution benthic foraminiferal Cibicidoides mundulus δ18O and δ13C records from equatorial Pacific International Ocean Drilling Program Site U1338 are correlated to North Atlantic Ocean Drilling Program Site 982 to obtain a global perspective. Four long‐term benthic δ18O variations are identified: the Tortonian‐Messinian, Miocene‐Pliocene, and Early‐Pliocene Oxygen Isotope Lows (8–7, 5.9–4.9, and 4.8–3.5 Ma) and the Messinian Oxygen Isotope High (MOH; 7–5.9 Ma). Obliquity‐paced variability dominates throughout, except during the MOH. Eleven new orbital‐scale isotopic stages are identified between 7.4 and 7.1 Ma. Cryosphere and carbon cycle sensitivities, estimated from δ18O and δ13C variability, suggest a weak cryosphere‐carbon cycle coupling. The MSC termination coincided with moderate cryosphere sensitivity and reduced global ice sheets. The LMCIS coincided with reduced carbon cycle sensitivity, suggesting a driving force independent of insolation changes. The response of the cryosphere and carbon cycle to obliquity forcing is established, defined as Earth System Response (ESR). Observations reveal that two late Miocene‐early Pliocene climate states existed. The first is a prevailing dynamic state with moderate ESR and obliquity‐driven Antarctic ice variations, associated with reduced global ice volumes. The second is a stable state, which occurred during the MOH, with reduced ESR and lower obliquity‐driven variability, associated with expanded global ice volumes.

Type: Article
Title: Evaluating climatic response to external radiative forcing during the late Miocene to early Pliocene: New perspectives from eastern equatorial Pacific (IODP U1338) and North Atlantic (ODP 982) locations
Open access status: An open access version is available from UCL Discovery
DOI: 10.1002/2015PA002881
Publisher version: https://doi.org/10.1002/2015PA002881
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Earth system response, cryosphere sensitivity, carbon cycle sensitivity, Messinian Salinity Crisis, late Miocene carbon isotope shift, benthic foraminiferal isotopes
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10076959
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