Evolving ocean basins in the Early Cretaceous greenhouse : A climate model-proxy synthesis of circulation, surface temperatures and carbon burial
Greenhouse climates with global mean temperatures significantly higher than today prevailed during large parts of the geological history. They provide direct evidence for the adaptation of the climate system to enhanced greenhouse gas forcing during the past and represent the only possibility to constrain model-derived projections of future anthropogenic warming. The Early Cretaceous (~145-100.5 Ma) provides a special opportunity to test our understanding of past greenhouse dynamics, as the long-term warmth was punctuated by severe perturbations of the global carbon cycle and episodes of transient cooling. Young and restricted ocean basins, emerging from the break-up of Gondwana, are a possible driver of both short- and long-term carbon cycle dynamics due to their enhanced organic carbon burial potential. This thesis aims to better constrain the main drivers of the Early Cretaceous greenhouse climate and to assess how they differed from the present-day dynamics. Dedicated climate model simulations of the Early Cretaceous were integrated with paleoceanographic records of water mass mixing, surface temperatures and organic carbon burial to assess both the causes for the mean state warming, as well as to reconstruct the tectonically driven ocean circulation and carbon cycle changes.