Synchronous Marine And Terrestrial Carbon Cycle Perturbation In The High Arctic During The Petm

The Paleocene-Eocene Thermal Maximum (PETM; 56 Ma) is considered to be one of the best analogs for future climate change. The carbon isotope composition (delta C-13) of n-alkanes derived from leaf waxes of terrestrial plants and marine algae can provide important insights into the carbon cycle perturbation during the PETM. Here, we present new organic geochemical data and compound-specific delta C-13 data from sediments recovered from an early Cenozoic basin-margin succession from Spitsbergen. These samples represent one of the most expanded PETM sites and provide new insights into the high Arctic response to the PETM. Our results reveal a synchronous similar to-6.5 parts per thousand carbon isotope excursion (CIE) in short-chain n-alkanes (nC(19); marine algae/bacteria) with a similar to-5 parts per thousand CIE in long-chain n-alkanes (nC(29) and nC(31); plant waxes) during the peak of the PETM. Although delta C-13(n-alkanes) values were potentially affected via a modest thermal effect (1 parts per thousand-2 parts per thousand), the relative changes in the delta C-13(n-alkanes) remain robust. A simple carbon cycle modeling suggests peak carbon emission rate could be similar to 3 times faster than previously suggested using delta C-13(TOC) records. The CIE magnitude of both delta C-13 (n-C19) and delta C-13(n-C29) can be explained by the elevated influence of C-13-depleted respired CO2 in the water column and increased water availability on land, elevated pCO(2) in the atmosphere, and changes in vegetation type during the PETM. The synchronous decline in delta C-13 of both leaf waxes and marine algae/bacteria argues against a significant contribution to the sedimentary organic carbon pool from the weathering delivery of fossil n-alkanes in the Arctic region.