The dynamics of global change at the Paleocene-Eocene thermal maximum: A data-model comparison

We integrate published stable isotopic, chemical, mineralogical, and biotic data from the onset of the Paleocene-Eocene thermal maximum (PETM) at Site 690, Maud Rise in the Southern Ocean. The integrated data set documents a sequence of environmental steps including warming of the ocean from the surface downward, and modification of its thermal and nutrient structure, acidification of the deep ocean, and the onset of continental weathering. The age of the events with respect to the onset of the PETM is calibrated with three different age models. The relative and absolute timing of the steps are compared with simulated temperature, salinity, calcite saturation, and dissolved PO₄ and O₂, at different depths in the ocean, generated with the UVic Earth System Climate Model of intermediate complexity. The simulation supports the top to bottom transfer of heat and carbon, and generally agrees with age models in terms of the durations of leads and lags in temperature, C-isotope, and biotic responses. Moreover, the simulation shows that stratification increased and the nutricline strengthened at the onset of the PETM. These environmental changes explain the abundance of deep-dwelling nannoplankton and foraminifera during the early part of the event. The modeled calcite saturation is consistent with a harsh deep-sea habitat at the time of the benthic foraminiferal extinction.