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How did temperatures near the Cretaceous poles compare with temperatures near the Equator?

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Cretaceous paleogeography — Cretaceous Period Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the late Cretaceous Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.

During the Cretaceous Period, the global climate was significantly warmer and more equable than it is today, with the temperature difference between the poles and the Equator being approximately half of what is observed in the modern era.1

Models of the mid-Cretaceous climate indicate that surface water temperatures at the Equator remained around 30 °C (86 °F) year-round. In contrast, temperatures at the poles were much milder than today, measuring 14 °C (57 °F) in the winter and 17 °C (63 °F) in the summer. This relatively small temperature gradient supported temperate conditions even at the poles, and ice sheets and glaciers were almost entirely absent, existing only in high mountain regions. These temperature estimates are derived from oxygen isotope measurements taken from the calcitic remains of marine organisms.1