A systematic role for extreme ocean-atmosphere oscillations in the development of glacial conditions since the Mid Pleistocene transition

Barker, Stephen ORCID: https://orcid.org/0000-0001-7870-6431 and Knorr, Gregor 2023. A systematic role for extreme ocean-atmosphere oscillations in the development of glacial conditions since the Mid Pleistocene transition. Paleoceanography and Paleoclimatology 38 (12) , e2023PA004690. 10.1029/2023PA004690

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Abstract

We introduce a new hypothesis concerning the role of internal climate dynamics in the non-linear transitions from interglacial to glacial (IG-G) state since the Mid Pleistocene Transition (MPT). These transitions encompass large and abrupt changes in atmospheric CO2, ice volume, and temperature that we suggest involve critical interactions between insolation and high amplitude oscillations in ocean/atmosphere circulation patterns. Specifically, we highlight the large amplitude of millennial-scale climate oscillations across the transition from Marine Isotope Stage (MIS) 5 to 4, which we argue led to amplified cooling of the deep ocean and we demonstrate that analogous episodes of extreme cooling systematically preceded glacial periods of the last 800 kyr. We suggest that such cooling necessitates a reconfiguration of the deep ocean to avoid a density paradox between northern and southern-sourced deep waters (SSW), which could be accomplished by increasing the relative volume and or salinity of SSW, thus providing the necessary storage capacity for the subsequent (delayed) and relatively abrupt drawdown of CO2. We therefore explain the transient decoupling of Antarctic temperature from CO2 across MIS 5/4 as a direct consequence of millennial activity at that time. We further show that similar climatic decoupling typically occurred during times of low obliquity and was a ubiquitous feature of IG-G transitions over the past 800 kyr, producing the appearance of bimodality in records of CO2, benthic δ18O and others. Finally we argue that the apparent lack of bimodality in the pre-MPT record of benthic δ18O implies that the dynamics associated with IG-G transitions changed across the MPT.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Publisher:	American Geophysical Union
ISSN:	2572-4517
Date of First Compliant Deposit:	20 December 2023
Date of Acceptance:	5 December 2023
Last Modified:	21 Dec 2023 15:00
URI:	https://orca.cardiff.ac.uk/id/eprint/165009

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