Response and feedback of sea ice, terrestrial organic carbon, and meltwater discharge to last deglacial climate change (Beaufort Sea, Arctic Ocean)

Abstract

Earth’s climate system is changing rapidly under global warming. For instance, in the polar region, the Arctic Ocean is losing sea ice, which can influence the heat flux, albedo effect, “Arctic Amplification” (additional warming), and the Atlantic Meridional Overturning Circulation. Besides, permafrost temperatures are increasing to record high levels, and the permafrost is expected to release additional CO2 and CH4 to the atmosphere. These variabilities of the Arctic components have been proposed as responses to anthropogenic activities. However, the climate system is of complexity. The distinction of variability between anthropogenic forcing and natural (external and internal) forcing will help us to understand the complex climate system and improve our future predictions. The transition from the Last Glacial Maximum to the Holocene is an ideal time frame to study the natural variability of the Arctic components as a response to external forcing and subsequent internal feedbacks. In this context, we performed a detailed study of a sediment core from the Canadian Beaufort Sea (core ARA04C/37), reconstructing sea-ice history, ancient terrestrial organic carbon mobilization (petrogenic organic carbon and permafrost carbon), and meltwater discharge. Sea-ice reconstruction has been achieved by analyses of multiple biomarkers, e.g., sea-ice biomarker IP25, HBI-III, and specific sterols. In order to conduct a comprehensive reconstruction of the surface water characteristics, more biomarkers (e.g., long-chain diols and GDGTs) were used. For the study of ancient terrestrial organic carbon remobilization, radiocarbon dating was applied on both terrestrial compounds (long-chain fatty acids) and bulk organic carbon to characterize the carbon age. Finally, hydrogen isotope analyses were performed on specific compounds (i.e., phytoplankton sterols, short-chain and long-chain fatty acids) to reconstruct the paleo hydrology and the Laurentide Ice Sheet meltwater discharge, with particular interest in the Younger Dryas flood event.