GEOCHEMICAL EVIDENCE FOR THE DISCHARGE OF METEORIC FLOW TO THE CHUKCHI SEA SUGGESTIVE OF A SUBSURFACE FLOW PULSE DURING THE EARLY HOLOCENE THERMAL MAXIMUM (EHTM) (Invited Presentation)

The impact of permafrost thaw on the discharge of subsurface flow in the Arctic Ocean and its connection to (bio-) geochemical interactions in this critical zone of our planet are still poorly understood. We present geochemical data collected on the Chukchi Shelf, where chloride and water isotope data reveal a meteoric source enriched in cations with a radiogenic fingerprint. The postulated subsurface fluid is enriched in dissolved inorganic carbon and methane; the isotopic composition of the carbon reservoirs is consistent with discharge of fluids affected by diagenetic reactions in a closed system. This scenario is in accordance with published reports of high abundance of a terrestrial humic-like fluorescent dissolved organic matter at this shelf site. These fluid characteristics are in stark contrast with those from other sites in the Chukchi Sea, where fluid discharge does not impact regional biogeochemical reactions in marine sediment. Numerical simulations indicate that the observed data at the investigated site in the shelf cannot be attributed to a water discharge that occurred during the past centuries and thus suggest no association with anthropogenically-induced climate change. Alternatively, we attribute our observations to paleo-subsurface flow resulting from permafrost thaw during the Early Holocene Thermal Maximum (EHTM).