THE IMPORTANCE OF PALEOBATHYMETRY IN UNDERSTANDING THE LONG-TERM CARBON CYCLE THROUGH VARIATIONS IN PALEO-OCEAN CARBONATE COMPENSATION DEPTHS THROUGHOUT THE LAST 100MYR

The supercontinent cycle manifested through seafloor spreading and cooling of oceanic lithosphere results in a constantly evolving bathymetry. First order changes occurred throughout the Cenozoic as plates speeds slowed by a factor of 2 and major plates reorganized. We evaluate the role of period-accurate bathymetry distributions at global and basin scales on the carbonate compensation depth (CCD). We created new bathymetric reconstructions throughout the last 100my. using the most recent reconstructions of plate age. Our select reconstruction is ocean volume consistent and accounts for the loss of smaller scale bathymetric features back in time. To analyze the effects of bathymetry on the carbon cycle we focus here on the Late Paleocene.

We find a strong bathymetric dependence on the CCD at global and basin scale levels using LOSCAR. Steady states snapshots at 60 Ma reveal that the Indian, Pacific, and Atlantic basin CCDs are ~1km deeper than previous estimates, while the Tethys CCD is over 2km deeper. Variations in the initial riverine flux, an uncertain climate parameter, potentially reconciles global CCD predictions with ocean core sample data. Reconstructions of the Tethys ocean have a significant influence on the carbon cycle since the Tethys is an important carbon sink location. The influence of the Tethys reconstruction is of importance, given the uncertainties in its reconstruction.

Our study demonstrates the need to reconcile the interpretative climate parameters used within climate modeling with realistic bathymetric reconstructions. The addition of evolving bathymetry proves to be necessary when studying the long-term climate and carbon cycles through models such as LOSCAR, GEOCLIM, and DCESS. Consequently, chosen bathymetry reconstructions need to be rationalized for, and amongst, climate studies to improve interpretations of these cycles.