Assessing the role of methane hydrates in the Late Paleocene – Early Eocene hyperthermals using a carbon cycle box model

The Late Paleocene – Early Eocene period is characterised by several short-term warming episodes superimposed on already high temperatures and CO₂ levels. These hyperthermal events are associated with negative carbon isotope excursions, which are thought to represent significant changes in the carbon cycle through input of isotopically light carbon into the exogenic carbon pool. Next to carbon release from melting permafrost, one large-scale carbon reservoir that might have been the source of this disturbance is marine methane hydrates. To study the potential role of this carbon reservoir in more detail, we expand the carbon cycle box model LOSCAR to include a methane hydrate reservoir. By adapting the carbon cycling parameterisations in the original LOSCAR ocean boxes to allow for organic carbon burial, and by determining a temperature-dependent gas hydrate stability zone in the sediment, we model the time-varying volume of marine methane gas hydrates. In order to investigate the dynamic response between methane hydrates and temperature fluctuations in the Eocene, we run simulations using the Early Eocene as a background state and orbital solutions plus noise as forcing, shedding new light on the role of methane hydrates in late Paleocene – early Eocene climate fluctuations.