Environmental controls of rapid terrestrial organic matter mobilization to the western Laptev Sea since the Last Deglaciation

Abstract. Arctic permafrost stores vast amounts of terrestrial organic matter (terrOM). Under warming climate conditions, Arctic permafrost thaws, releasing aged carbon and potentially impacting the modern carbon cycle. We investigated the characteristics of terrestrial biomarkers, including n-alkanes, fatty acids, and lignin phenols, in marine sediment cores to understand how the sources of terrOM transported to the ocean change in response to varying environmental conditions, such as sea-level rise, sea-ice coverage, inland climate warming, and freshwater input. We examined two sediment records from the western Laptev Sea (PS51/154 and PS51/159) covering the past 17.8 kyr. Our analyses reveal three periods with high mass accumulation rates (MARs) of terrestrial biomarkers, from 14.1 to 13.2, 11.6 to 10.9, and 10.9 to 9.5 kyr BP. These terrOM MAR peaks revealed distinct terrOM sources, likely in response to changes in shelf topography, rates of sea-level rise, and inland warming. By comparing periods of high terrOM MAR in the Laptev Sea with published records from other Arctic marginal seas, we suggest that enhanced coastal erosion driven by rapid sea-level rise during meltwater pulse 1A (mwp-1A) triggered elevated terrOM MAR across the Arctic. Additional terrOM MAR peaks varied regionally. Peaks from the Beaufort Sea during the Bølling–Allerød coincided with a freshwater flooding event, while peaks from the Laptev Sea and the Fram Strait during the Preboreal/early Holocene coincided with periods of enhanced inland warming and prolonged ice-free conditions. Our results highlight the influence of regional environmental conditions, in addition to global drivers, which can either promote or preclude regional terrOM fluxes.