Palaeogeographic regulation of glacial events during the Cretaceous supergreenhouse.

Jean-Baptiste Ladant,Yannick Donnadieu

doi:10.1038/ncomms12771

Abstract

The historical view of a uniformly warm Cretaceous is being increasingly challenged by the accumulation of new data hinting at the possibility of glacial events, even during the Cenomanian–Turonian (∼95 Myr ago), the warmest interval of the Cretaceous. Here we show that the palaeogeography typifying the Cenomanian–Turonian renders the Earth System resilient to glaciation with no perennial ice accumulation occurring under prescribed CO2 levels as low as 420 p.p.m. Conversely, late Aptian (∼115 Myr ago) and Maastrichtian (∼70 Myr ago) continental configurations set the stage for cooler climatic conditions, favouring possible inception of Antarctic ice sheets under CO2 concentrations, respectively, about 400 and 300 p.p.m. higher than for the Cenomanian–Turonian. Our simulations notably emphasize that palaeogeography can crucially impact global climate by modulating the CO2 threshold for ice sheet inception and make the possibility of glacial events during the Cenomanian–Turonian unlikely.

Highlights

The historical view of a uniformly warm Cretaceous is being increasingly challenged by the accumulation of new data hinting at the possibility of glacial events, even during the Cenomanian–Turonian (B95 Myr ago), the warmest interval of the Cretaceous
The Aptian to Maastrichtian shift in Southern Ocean convective mixing areas is consistent with the onset of deepwater formation in the South Atlantic and Proto-Indian Ocean during the Late Cretaceous inferred from neodymium isotopes[47]
In spite of slightly different boundary conditions, our results are in close agreement regarding the sites of deep-water formation and the Turonian to Maastrichtian cooling of Donnadieu et al.[44], whereas the simulations of Lunt et al.[33] shows a warmer Maastrichtian, possibly because of different modes of ocean circulation, as sites of deep-water formation are not located in the same areas, or because of different palaeogeographic reconstructions

Summary

Introduction

The historical view of a uniformly warm Cretaceous is being increasingly challenged by the accumulation of new data hinting at the possibility of glacial events, even during the Cenomanian–Turonian (B95 Myr ago), the warmest interval of the Cretaceous. Estimates of Cretaceous climates reveal warmer inland[1,2] and oceanic temperatures[3,4,5,6] relative to today, possibly reaching up to more than 5 °C warmer in the low latitudes[3,4] and more than 15 °C warmer in the high latitudes[7] This led to reduced meridional temperature gradients[8], as indicated for instance by evidence for ectothermic crocodilian species poleward of 70° N The downward revision of atmospheric pCO2 estimates for the mid-Cretaceous[23,24,25], to levels possibly below those inferred from previous modelling studies[26,27] and proxy records[28,29] at the time of the major Eocene–Oligocene (EO) Antarctic glaciation[30,31] (B34 Myr ago), adds support to the possibility of Cenomanian–Turonian ice sheets. Our simulations highlight the role of palaeogeography in maintaining a warmer Cenomanian– Turonian relative to the late Aptian and Maastrichtian, supporting the absence of ice during the Cretaceous so-called Climatic Optimum

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Conclusion