Evidence for increased latent heat transport during the Cretaceous (Albian) greenhouse warming

Quantitative estimates of increased heat transfer by atmospheric H2O vapor during the Albian greenhouse warming suggest that the intensified hydrologic cycle played a greater role in warming high latitudes than at present and thus represents a viable alternative to oceanic heat transport. Sphaerosiderite d18O values in paleosols of the North American Cretaceous Western Interior Basin are a proxy for meteoric d18O values, and massbalance modeling results suggest that Albian precipitation rates exceeded modern rates at both mid and high latitudes. Comparison of modeled Albian and modern precipitation minus evaporation values suggests amplification of the Albian moisture deficit in the tropics and moisture surplus in the mid to high latitudes. The tropical moisture deficit represents an average heat loss of ;75 W/m2 at 108N paleolatitude (at present, 21 W/m2). The increased precipitation at higher latitudes implies an average heat gain of ;83 W/ m2 at 458N (at present, 23 W/m2) and of 19 W/m2 at 758N (at present, 4 W/m2). These estimates of increased poleward heat transfer by H2O vapor during the Albian may help to explain the reduced equator-to-pole temperature gradients.