Increased petrogenic and biospheric organic carbon burial in sub‐Antarctic fjord sediments in response to recent glacier retreat

Fjords are recognized as hotspots of organic carbon (OC) burial in the coastal ocean. In fjords with glaciated catchments, glacier discharge carries large amounts suspended matter. This sedimentary load includes OC from bedrock and terrigenous sources (modern vegetation, peat, soil deposits), which is either buried fjord or remineralized during export, acting a potential source CO2 to atmosphere. sub-Antarctic South Georgia, fjord-terminating glaciers have been retreating past decades, likely response changing climate conditions. We determine surface sediments Cumberland Bay, using lipid biomarkers bulk 14C isotopic composition, quantify at present for time period documented retreat (between 1958 2017). Petrogenic dominant type proximity present-day calving fronts (60.4 ± 1.4% 73.8 2.6%) decreases 14.0 2.7% outside fjord, indicating that petrogenic effectively fjord. Beside marine OC, comprises 2.7 0.5% 7.9 5.9% mostly derived modern plants Holocene peat deposits eroded along flanks rather than released by glaciers. estimate tidewater between 2017 led an increase accumulation 22% West Bay 6.5% East suggesting successive does not only release into but also increases capacity burial.