Document Type

Article

Department/Program

Virginia Institute of Marine Science

Publication Date

2018

Journal

Scientific Reports

Volume

8

Abstract

The abundance of organic carbon (OC) in vegetation and soils (similar to 2,600 PgC) compared to carbon in the atmosphere (similar to 830 PgC) highlights the importance of terrestrial OC in global carbon budgets. The residence time of OC in continental reservoirs, which sets the rates of carbon exchange between land and atmosphere, represents a key uncertainty in global carbon cycle dynamics. Retention of terrestrial OC can also distort bulk OC- and biomarker-based paleorecords, yet continental storage timescales remain poorly quantified. Using "bomb" radiocarbon (C-14) from thermonuclear weapons testing as a tracer, we model leaf-wax fatty acid and bulk OC C-14 signatures in a river-proximal marine sediment core from the Bay of Bengal in order to constrain OC storage timescales within the Ganges-Brahmaputra (G-B) watershed. Our model shows that 79-83% of the leaf-waxes in this core were stored in continental reservoirs for an average of 1,000-1,200 calendar years, while the remainder was stored for an average of 15 years. This age structure distorts high-resolution organic paleorecords across geologically rapid events, highlighting that compound-specific proxy approaches must consider storage timescales. Furthermore, these results show that future environmental change could destabilize large stores of old - yet reactive - OC currently stored in tropical basins.

DOI

10.1038/s41598-018-30091-8

Keywords

Fatty-Acids; Sediment Transport; River-Basin; Carbon; Radiocarbon; Himalaya; Erosion; Degradation; Constraints; Climate

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