The DeepMIP contribution to PMIP4: methodologies for selection, compilation and analysis of latest Paleocene and early Eocene climate proxy data, incorporating version 0.1 of the DeepMIP database

This is the final version of the article. Available from European Geosciences Union via the DOI in this record.Data availability. The data referenced in this manuscript are provided as Supplement Data Files 1 to 8. In the final version, these files will form DeepMIP database version 0.1 and will be accessible online via a citable DOI reference.The early Eocene (56 to 48 million years ago) is inferred to have been the most recent time that Earth's atmospheric CO2 concentrations exceeded 1000 ppm. Global mean temperatures were also substantially warmer than those of the present day. As such, the study of early Eocene climate provides insight into how a super-warm Earth system behaves and offers an opportunity to evaluate climate models under conditions of high greenhouse gas forcing. The Deep Time Model Intercomparison Project (DeepMIP) is a systematic model–model and model–data intercomparison of three early Paleogene time slices: latest Paleocene, Paleocene–Eocene thermal maximum (PETM) and early Eocene climatic optimum (EECO). A previous article outlined the model experimental design for climate model simulations. In this article, we outline the methodologies to be used for the compilation and analysis of climate proxy data, primarily proxies for temperature and CO2. This paper establishes the protocols for a concerted and coordinated effort to compile the climate proxy records across a wide geographic range. The resulting climate “atlas” will be used to constrain and evaluate climate models for the three selected time intervals and provide insights into the mechanisms that control these warm climate states. We provide version 0.1 of this database, in anticipation that this will be expanded in subsequent publications.Natural Environment Research Council (NERC)GNS Science Global Change through Time ProgrammeNational Science Foundation (NSF)KU Leuve

Proxy evidence for state-dependence of climate sensitivity in the Eocene greenhouse

Despite recent advances, the link between the evolution of atmospheric CO2 and climate during the Eocene greenhouse remains uncertain. In particular, modelling studies suggest that in order to achieve the global warmth that characterised the early Eocene, warmer climates must be more sensitive to CO2 forcing than colder climates. Here, we test this assertion in the geological record by combining a new high-resolution boron isotope-based CO2 record with novel estimates of Global Mean Temperature. We find that Equilibrium Climate Sensitivity (ECS) was indeed higher during the warmest intervals of the Eocene, agreeing well with recent model simulations, and declined through the Eocene as global climate cooled. These observations indicate that the canonical IPCC range of ECS (1.5 to 4.5 °C per doubling) is unlikely to be appropriate for high-CO2 warm climates of the past, and the state dependency of ECS may play an increasingly important role in determining the state of future climate as the Earth continues to warm

Registered Replication Report: Dijksterhuis and van Knippenberg (1998)

Dijksterhuis and van Knippenberg (1998) reported that participants primed with a category associated with intelligence ("professor") subsequently performed 13% better on a trivia test than participants primed with a category associated with a lack of intelligence ("soccer hooligans"). In two unpublished replications of this study designed to verify the appropriate testing procedures, Dijksterhuis, van Knippenberg, and Holland observed a smaller difference between conditions (2%-3%) as well as a gender difference: Men showed the effect (9.3% and 7.6%), but women did not (0.3% and -0.3%). The procedure used in those replications served as the basis for this multilab Registered Replication Report. A total of 40 laboratories collected data for this project, and 23 of these laboratories met all inclusion criteria. Here we report the meta-analytic results for those 23 direct replications (total N = 4,493), which tested whether performance on a 30-item general-knowledge trivia task differed between these two priming conditions (results of supplementary analyses of the data from all 40 labs, N = 6,454, are also reported). We observed no overall difference in trivia performance between participants primed with the "professor" category and those primed with the "hooligan" category (0.14%) and no moderation by gender

The DeepMIP contribution to PMIP4: methodologies for selection, compilation and analysis of latest Paleocene and early Eocene climate proxy data, incorporating version 0.1 of the DeepMIP database

The early Eocene (56 to 48 million years ago) is inferred to have been the most recent time that Earth's atmospheric CO₂ concentrations exceeded 1000 ppm. Global mean temperatures were also substantially warmer than those of the present day. As such, the study of early Eocene climate provides insight into how a super-warm Earth system behaves and offers an opportunity to evaluate climate models under conditions of high greenhouse gas forcing. The Deep Time Model Intercomparison Project (DeepMIP) is a systematic model–model and model–data intercomparison of three early Paleogene time slices: latest Paleocene, Paleocene–Eocene thermal maximum (PETM) and early Eocene climatic optimum (EECO). A previous article outlined the model experimental design for climate model simulations. In this article, we outline the methodologies to be used for the compilation and analysis of climate proxy data, primarily proxies for temperature and CO₂. This paper establishes the protocols for a concerted and coordinated effort to compile the climate proxy records across a wide geographic range. The resulting climate “atlas” will be used to constrain and evaluate climate models for the three selected time intervals and provide insights into the mechanisms that control these warm climate states. We provide version 0.1 of this database, in anticipation that this will be expanded in subsequent publications

Cold spells in the Nordic Seas during the early Eocene Greenhouse

Abstract The early Eocene (c. 56 - 48 million years ago) experienced some of the highest global temperatures in Earth’s history since the Mesozoic, with no polar ice. Reports of contradictory ice-rafted erratics and cold water glendonites in the higher latitudes have been largely dismissed due to ambiguity of the significance of these purported cold-climate indicators. Here we apply clumped isotope paleothermometry to a traditionally qualitative abiotic proxy, glendonite calcite, to generate quantitative temperature estimates for northern mid-latitude bottom waters. Our data show that the glendonites of the Danish Basin formed in waters below 5 °C, at water depths of &lt;300 m. Such near-freezing temperatures have not previously been reconstructed from proxy data for anywhere on the early Eocene Earth, and these data therefore suggest that regionalised cool episodes punctuated the background warmth of the early Eocene, likely linked to eruptive phases of the North Atlantic Igneous Province.</jats:p

Deoxygenation and organic carbon sequestration in the Tethyan realm associated with the Middle Eocene Climatic Optimum

The Middle Eocene Climatic Optimum (MECO; ~40 Ma) stands out as a transient global warming phase of ~400 kyr that interrupted long-term Eocene cooling, associated with a rise in atmospheric CO2 concentrations that has been linked to a flare-up in Arabia-Eurasia Revised manuscript for submission to GSA Bulletin continental arc volcanism. Increased organic carbon burial in the Tethys Ocean has been proposed as a carbon sequestration mechanism to bring the MECO to an end. To further test these hypotheses, we assess the sedimentary and geochemical expression of the MECO in the northern Peri-Tethys, specifically the organic-rich Kuma Formation of the Belaya River section, located on the edge of the Scythian Platform in the North Caucasus, Russia. We construct an age-depth model using nannofossil chronobiostratigraphy. Throughout the studiedmiddle Eocene interval (41.2–39.9 Ma), we document TEX86-based sea surface temperatures of 32–36°C depending on proxy calibration, and during the early MECO we observe sea surface warming of 2–3 °C. Despite the proximity of the section to the Arabia-Eurasia volcanic arc, the hypothesized source of volcanic CO2, we find no evidence for enhanced regional volcanism in sedimentary mercury concentrations. Sedimentary trace element concentrations and iron speciation indicate reducing bottom waters throughout the middle Eocene, but the most reducing, even euxinic conditions were reached during late MECO cooling. This apparent regional decoupling between ocean warming and deoxygenation hints at a role for regional tectonics in causing basin restriction and anoxia. Associated excess organic carbon burial, extrapolated to the entire regional Kuma Fm, may have been ~8.1 Tg C yr-1, comprising ~450 Pg C over this ~55 kyr interval. Combined with evidence for enhanced organic carbon drawdown in the western Peri-Tethys, this supports a quantitatively significant role for the basin in the termination of the MECO by acting as a large organic carbon sink, and collectively illustrates that the closing Tethys Ocean might have affected global Paleogene climate. Moreover, this study highlights that the interplay of global climate and regional gateway evolution is important in determining local climate and oceanographic change

Deoxygenation and organic carbon sequestration in the Tethyan realm associated with the Middle Eocene Climatic Optimum

The Middle Eocene Climatic Optimum (MECO; ~40 Ma) stands out as a transient global warming phase of ~400 kyr that interrupted long-term Eocene cooling, associated with a rise in atmospheric CO2 concentrations that has been linked to a flare-up in Arabia-Eurasia Revised manuscript for submission to GSA Bulletin continental arc volcanism. Increased organic carbon burial in the Tethys Ocean has been proposed as a carbon sequestration mechanism to bring the MECO to an end. To further test these hypotheses, we assess the sedimentary and geochemical expression of the MECO in the northern Peri-Tethys, specifically the organic-rich Kuma Formation of the Belaya River section, located on the edge of the Scythian Platform in the North Caucasus, Russia. We construct an age-depth model using nannofossil chronobiostratigraphy. Throughout the studiedmiddle Eocene interval (41.2–39.9 Ma), we document TEX86-based sea surface temperatures of 32–36°C depending on proxy calibration, and during the early MECO we observe sea surface warming of 2–3 °C. Despite the proximity of the section to the Arabia-Eurasia volcanic arc, the hypothesized source of volcanic CO2, we find no evidence for enhanced regional volcanism in sedimentary mercury concentrations. Sedimentary trace element concentrations and iron speciation indicate reducing bottom waters throughout the middle Eocene, but the most reducing, even euxinic conditions were reached during late MECO cooling. This apparent regional decoupling between ocean warming and deoxygenation hints at a role for regional tectonics in causing basin restriction and anoxia. Associated excess organic carbon burial, extrapolated to the entire regional Kuma Fm, may have been ~8.1 Tg C yr-1, comprising ~450 Pg C over this ~55 kyr interval. Combined with evidence for enhanced organic carbon drawdown in the western Peri-Tethys, this supports a quantitatively significant role for the basin in the termination of the MECO by acting as a large organic carbon sink, and collectively illustrates that the closing Tethys Ocean might have affected global Paleogene climate. Moreover, this study highlights that the interplay of global climate and regional gateway evolution is important in determining local climate and oceanographic change

Surface-circulation change in the Southern Ocean across the Middle Eocene Climatic Optimum: inferences from dinoflagellate cysts and biomarker paleothermometry

Global climate cooled from the early Eocene hothouse (~ 52–50 Ma) to the latest Eocene (~ 34 Ma). At the same time, the tectonic evolution of the Southern Ocean was characterized by the opening and deepening of circum-Antarctic gateways, which affected both surface- and deep-ocean circulation. The Tasman Gateway played a key role in regulating ocean throughflow between Australia and Antarctica. Southern Ocean surface currents through and around the Tasman Gateway have left recognizable tracers in the spatiotemporal distribution of plankton fossils, including organic-walled dinoflagellate cysts. This spatiotemporal distribution depends on physico-chemical properties of the water masses in which these organisms thrived. The degree to which the geographic path of surface currents (primarily controlled by tectonism) or their physico-chemical properties (significantly impacted by climate) have controlled the composition of the fossil assemblages has, however, remained unclear. In fact, it is yet poorly understood to what extent oceanographic response as a whole was dictated by climate change, independent of tectonics-induced oceanographic changes that operate on longer time scales. To disentangle the effects of tectonism and climate in the southwest Pacific Ocean, we target a climatic deviation from the long-term Eocene cooling trend, a 500 thousand year long global warming phase termed the Middle Eocene Climatic Optimum (MECO; ~ 40 Ma). The MECO warming is unrelated to regional tectonism, and thus provides a test case to investigate the oceans physiochemical response to climate change only. We reconstruct changes in surface-water circulation and temperature in and around the Tasman Gateway during the MECO through new palynological and organic geochemical records from the central Tasman Gateway (Ocean Drilling Program Site 1170), the Otway Basin (southeastern Australia) and the Hampden Section (New Zealand). Our results confirm that dinocyst communities track tectonically driven circulation patterns, yet the variability within these communities can be driven by superimposed temperature change. Together with published results from the east of the Tasman Gateway, our results suggest that as surface-ocean temperatures rose, the East Australian Current extended further southward during the peak of MECO warmth. Simultaneous with high sea-surface temperatures in the Tasman Gateway area, pollen assemblages indicate warm temperate rainforests with paratropical elements along the southeastern margin of Australia. Finally, based on new age constraints we suggest that a regional southeast Australian transgression might have been caused by sea-level rise during MECO