Multi-proxy biomarker and bulk geochemical records from surface sediments and five sediment cores across the Chukchi Sea

Ongoing global warming is rapidly altering the Arctic carbon cycle, yet the influence of key environmental drivers remains poorly constrained. We present multi-proxy records of bulk organic parameters (TOC, TN, δ¹³C, δ¹⁵N, C/N) and terrestrial n-alkanes (TERR-alkanes) from 19 surface sediments and five 210Pb-dated sediment cores spanning the past three centuries from the Chukchi Sea. All cores reveal an increase in organic carbon (OC) since the onset of the Industrial Era, with distinct regional trends. Southern Chukchi Sea cores record higher TOC, TN and C/N values, consistent with increased riverine terrestrial OC input supported by TERR-alkane trends, while northern cores show enhanced marine OC contributions linked to sea ice retreat. A pronounced pre-industrial terrestrial OC export event (1750–1800 CE) coincides with multi-decadal sea-ice loss. Comparison with paleo-records and instrumental data indicates that air temperature and sea ice concentration exert the primary control on organic carbon dynamics, whereas river discharge plays a secondary role, limited to the southwestern Chukchi Sea. These findings provide new evidence for climate-driven acceleration of terrestrial OC fluxes since pre-industrial times and highlight the Chukchi Sea as a sensitive gateway for Arctic carbon cycle responses to global warming.