Development of the Cretaceous Greenhouse Climate and the Oceanic Thermal Structure

Abstract

Abstract. The development of the climate during the Cretaceous greenhouse interval is reviewed based on geological and paleontological records, geochemical proxy records for paleotemperature and atmospheric carbon-dioxide concentration (pCO2), the production rate of oceanic crust, and the timing and scale of emplacement of large igneous provinces. Geological and paleontological evidence, and paleotemperature records indicate that the Early Cretaceous climate was relatively cool, possibly accompanied by the development of continental ice sheets. Subsequent warming reached a peak in the Turonian, when sea surface temperatures in equatorial and high-latitude regions exceeded 36° C and 20° C, respectively. The possibility of a maximum temperature above 36° C at the equator is inconsistent with the cirrus cloud negative-feedback hypothesis proposed for the modern ocean, which may indicate that the hypothesis is not valid for an ice-free greenhouse system. Although elevated levels of pCO2 are thought to be resp...