LOOKING FORWARD BY LOOKING BACK: RESPONSE OF THE CARBONATE SYSTEM TO MASSIVE CARBON ADDITION AT THE PALEOCENE/ EOCENE BOUNDARY

The addition of anthropogenic carbon to the ocean/ atmosphere system is a risky experiment with uncertain consequences for the Earth system, but greenhouse gas release at these rates is not a new experiment in Earth history.  Mass balance calculations suggest that rapid global warming at the Paleocene/ Eocene boundary (5 to 8 °C warming of global sea surface temperatures in less than 10,000 years), referred to as the Paleocene/ Eocene Thermal Maximum (PETM), was caused by methane emission at a rate similar to modern anthropogenic methane emission rates.  Measurements of the calcium carbonate content of pelagic sediments containing the PETM interval indicate that the response of the carbonate system was a dramatic shoaling of the lysocline in some regions, but that other regions were relatively unaffected.  Using a 3D fully coupled intermediate complexity earth system model (CBS-GOLDSTEIN) tuned to Late Paleocene (pre-PETM) conditions, the spatial and temporal evolution of the carbonate system is investigated.  Preliminary results show that for CO₂ released into the atmosphere with even spatial distribution, the model generates greater dissolution of Atlantic Ocean carbonate sediments than of sediments in the Pacific Ocean.  This result is consistent with observations, however the observations were originally interpreted as an indication that carbon release was focussed on the Atlantic Ocean.