The Cretaceous ‘greenhouse’ period (~145 to ~66 million years ago, Ma) in Earth’s history is relatively well documented by multiple paleoproxy records, which indicate that the meridional sea surface temperature (SST) gradient increased (non-monotonically) from the Valanginian (~135 Ma) to the Maastrichtian (~68 Ma). Changes in atmospheric CO2 concentration, solar constant, and paleogeography are the primary drivers of variations in the spatiotemporal distribution of SST. However, the particular contribution of each of these drivers (and their underlying mechanisms) to changes in the SST distribution remains poorly understood. Here we use data from a suite of paleoclimate simulations to compare the relative effects of atmospheric CO2 variability and paleogeographic changes on mid-latitudinal SST gradient through the Cretaceous. Further, we use a fundamental model of wind-driven ocean gyres to quantify how changes in the Northern Hemisphere paleogeography weaken the circulation in subtropical ocean gyres, leading to an increase in extratropical SSTs.
Bibliographical noteFunding Information:
K.G. and H.G. were supported by the Joint National Natural Science Foundation of China–Israel Science Foundation (research grant number 2547/17) and by the U.S.–Israel Binational Science Foundation (BSF grant number 2018152). D.J.L. and A.F. acknowledge Leverhulme grant RPG-2019-365; D.J.L. acknowledges NERC grant NE/X000222/1; A.F. acknowledges the Chinese Academy of Sciences Visiting Professorship for Senior International Scientists grant 2021FSE0001.
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