Received: 18 Jan 2023 – Discussion started: 19 Jan 2023
Abstract. Decreasing sea ice extent in summer caused by climate change is affecting the carbon cycle of the Arctic Ocean. In this study, surface sediments across the western Arctic Ocean are investigated to characterize sources of sedimentary organic carbon (OC). Bulk organic parameters (total organic carbon, total nitrogen, δ13Corg and δ15N) combined with molecular organic biomarkers (e.g., sterols and highly branched isoprenoids (HBIs)) are applied to distinguish between sympagic, pelagic, and terrestrial OC. Furthermore, downcore profiles of these parameters were also generated from the Chukchi Sea R1 core (74° N) to evaluate changes in the relative contribution of these three components of sedimentary OC over the last 200 years with decreasing sea ice. Our data evidence that from 1820s to 1930s, prevailing high and variable sea ice cover inhibited in situ primary production resulting in prominent land-derived material stored in sediments. From 1930s to 1980s, with the gradual decline of sea ice, primary production increased progressively. The ratio of sympagic and pelagic OC began to rise to account for a larger portion of sedimentary OC. Since 1980s, accelerated sea ice loss led to enhanced primary production, stabilizing over the last decades due to freshwater induced surface ocean stratification in summer.
We reconstructed sea ice and organic carbon composition variabilities based on biomarkers and carbon stable isotopes in the northern Chukchi Sea, western Arctic Ocean, over the past 200 years. Under permanent ice cover, organic carbon was dominated by land sources transported by sea ice and ocean currents, while local primary productivity was suppressed by light limitation. Since ice retreated in 20th century, organic carbon from primary production gradually overtook the terrestrial component.
We reconstructed sea ice and organic carbon composition variabilities based on biomarkers and...