Sea level and deep-sea temperature reconstructions suggest quasi-stable states and critical transitions over the past 40 million years.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 34172440.
- Also identified by DOI 10.1126/sciadv.abf5326 and PMC identifier 8232915.
- Licence recorded as CC BY-NC.
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Abstract
Sea level and deep-sea temperature variations are key indicators of global climate changes. For continuous records over millions of years, deep-sea carbonate microfossil-based δ<sup>18</sup>O (δ<sub>c</sub>) records are indispensable because they reflect changes in both deep-sea temperature and seawater δ<sup>18</sup>O (δ<sub>w</sub>); the latter are related to ice volume and, thus, to sea level changes. Deep-sea temperature is usually resolved using elemental ratios in the same benthic microfossil shells used for δ<sub>c</sub>, with linear scaling of residual δ<sub>w</sub> to sea level changes. Uncertainties are large and the linear-scaling assumption remains untested. Here, we present a new process-based approach to assess relationships between changes in sea level, mean ice sheet δ<sup>18</sup>O, and both deep-sea δ<sub>w</sub> and temperature and find distinct nonlinearity between sea level and δ<sub>w</sub> changes. Application to δ<sub>c</sub> records over the past 40 million years suggests that Earth's climate system has complex dynamical behavior, with threshold-like adjustments (critical transitions) that separate quasi-stable deep-sea temperature and ice-volume states.