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 <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.

Cenozoic evolution of deep ocean temperature from clumped isotope thermometry

“…S4). Distinct cold spells around 55 Ma have previously been reported for the North Atlantic region ( 32 ), and the Δ 47 temperatures from ( 18 ) show that these extended to the deep South Atlantic (Fig. 1A, pink stars and blue triangle).…”

Preservation and Taphonomy of Fossil Insects from the Earliest Eocene of Denmark

“…Such factors may contribute to the retention of eumelanin in the fossil record by stabilizing it against decay and providing an inherent resistance to diagenetic alteration [89]. Moreover, the relatively mild geothermal conditions of the Stolleklint Clay and Fur Formation [90,91] presumably limited breakdown (previous studies have indicated that elevated burial temperature is a major factor controlling the preservation of eumelanin [92] as well as other molecular components and structures in arthropods [11,61,66,69]).…”

Temperature Dependence of Clumped Isotopes (∆47) in Aragonite

“…The ∼1.5°C difference in reconstructed temperature between the calibrations in the low temperature range (<30°C) may seem trivial and requires the complete A. islandica data set (N = 278; see Figure 3) to resolve. However, in paleoclimate reconstructions (e.g., Agterhuis et al, 2022;de Winter, Müller et al, 2021;de Winter et al, 2017;Meckler et al, 2022;Petersen et al, 2016;Vickers, Fernandez, et al, 2020), this temperature offset may have significant consequences. A ∼1.5°C cold bias in temperature reconstructions may lead to a significant underestimation of climate sensitivity to CO 2 forcing, biasing the physical science basis for informing policymakers about future climate change (e.g., Dennis et al, 2013;IPCC, 2021;Modestou et al, 2020;Tierney et al, 2020;Westerhold et al, 2020).…”