Sources and age of terrigenous organic matter exported from the Lena River watershed, NE Siberia

• Main Authors: Winterfeld, Maria, Goñi, Miguel, Just, Janna, Hefter, Jens, Sun, Shuwen, Han, Pai, Mollenhauer, Gesine
• Format: Conference Object
• Language: unknown
• Published: 2015
• Subjects: Arctic; Laptev Sea; laptev; lena delta; lena river; permafrost; taiga; Tundra; Siberia
• Online Access: https://epic.awi.de/id/eprint/39647/; https://epic.awi.de/id/eprint/39647/1/Winterfeld_Goldschmidt_2015.pdf; https://hdl.handle.net/10013/epic.46764; https://hdl.handle.net/10013/epic.46764.d001

The Lena River in central Siberia represents one of the major pathways for relocating pre-aged terrestrial organic matter (OMterr) stored in permafrost soils from its catchment to the coastal zone of the Laptev Sea. Future Arctic warming and permafrost thawing will likely enhance the re-mobilization and export of this pre-aged OMterr. Despite our improving knowledge about the fate of OMterr released from permafrost, the quality and age of particulate OMterr as well as the sources within the large watershed contributing to the exported OMterr are still not completely understood. To characterize the composition and sources of OMterr discharged by the Lena River, we analyzed the lignin phenol and carbon isotopic composition (δ13C and ∆14C) in Lena Delta soils, total suspended matter (TSM) from surface waters along with surface sediments offshore the delta. A simple linear mixing model based on the bulk lignin phenol distributions indicates that OMterr in TSM samples and coastal surface sediments contains comparable contributions from gymnosperms originating from the taiga forests south of the delta and angiosperms typical for tundra vegetation. Further, we present results of the lignin phenol compositions and inferred sources of OMterr transported with specific grain-size classes (>2mm, 63µm – 2mm, <63µm) of soil and sediment samples associated with different hydrological conditions (spring flood vs. summer low flow). Overall stronger diagenetic alteration in TSM and coastal sediments relative to soils appears to reflect degradation of more labile components during permafrost thawing and transport. Moreover, Lignin phenols and ∆14C of surface sediments suggest that OMTERR deposited offshore is more degraded and older than materials present in river suspended particles and catchment soils.