Total Organic Carbon, Lead-210, and Thermogravimetric analysis data from sediment cores from Marian Cove, Börgen Bay, and Sheldon Cove, December 2018 to January 2020.

This dataset comprises sediment geochronology, organic carbon, and thermogravimetric data from three deglaciating fjords along the West Antarctic Peninsula (WAP): Marian Cove (Maxwell Bay, King George Island), Börgen Bay (Anvers Island) and Sheldon Cove (Adelaide Island). The three sites form a north–south transect spanning a major hydrographic boundary, from the cold Bransfield Strait Water in the north to sites influenced by upper Circumpolar Deep Water (uCDW) shoaling further south, and additionally capture contrasting fjord geometries, bathymetries, glacial-retreat histories, and atmospheric climates. The data were collected to quantify long-term organic carbon accumulation, burial and sequestration potential in WAP fjords. Sediment cores were collected during the 2018/19 and 2019/20 austral summers aboard the RRS James Clark Ross (cruises JR18003 and JR19002). These observations were primarily funded by NERC ICEBERGS Standard Grant NE/P003087/1 (funding for research cruises for collection of sediment cores), with additional funding from the European Research Council (ERC) Synergy Project SEACHANGE, grant agreement No 856488 (for 210Pb analysis at the University of Plymouth), and Convex Group Ltd for the Convex Seascape Survey, which is facilitated by Blue Marine Foundation (for additional TOC analysis).