TY - JOUR T1 - Erosion of modern terrestrial organic matter as a major component of sediments in fjords JF - Geophysical Research Letters Y1 - 2017 A1 - Cui, Xingqian A1 - Bianchi, Thomas S. A1 - Savage, Candida AB - Fjords have recently been recognized as “hot spots” of carbon burial. In this study, we investigated organic carbon (OC) and biomarker radiocarbon values in fjord sediments from New Zealand. Our results showed that OC was mostly modern with the most aged OC in middle reaches of fjords, likely related to hydrodynamic sorting and inputs along adjacent slopes. Radiocarbon ages of sedimentary OC increased from north-to-south, consistent with the Fiordland regional gradients of lower fjord slopes and less rainfall. Our biomarker results suggested that lignin and long-chain fatty acids were preferentially linked with fresh terrestrial debris and degraded soil, respectively, likely due to their chemical and physical properties. Finally, we propose that fjords are a significant sink of modern OC, in contrast to large lowland coastal systems as a major sink of preaged OC. Overall, this study indicated that radiocarbon techniques are critical in investigating carbon dynamics in coastal systems. VL - 442824441945245112168105110293225215662639493436151675187268234320723424507431438414191121427211539259 UR - http://doi.wiley.com/10.1002/2016GL072260http://onlinelibrary.wiley.com/wol1/doi/10.1002/2016GL072260/fullpdfhttps://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2016GL072260 IS - 345355903755111181-21212316171193141-2182341 ER - TY - JOUR T1 - Permafrost Organic Carbon Mobilization From the Watershed to the Colville River Delta: Evidence From 14C Ramped Pyrolysis and Lignin Biomarkers JF - Geophysical Research Letters Y1 - 2017 A1 - Zhang, Xiaowen A1 - Bianchi, Thomas S. A1 - Cui, Xingqian A1 - Rosenheim, Brad E. A1 - Ping, Chien‐Lu A1 - Hanna, Andrea J. M. A1 - Kanevskiy, Mikhail A1 - Schreiner, Kathryn M. A1 - Allison, Mead A. KW - Arctic KW - carbon cycling KW - Colville River KW - Lignin KW - permafrost KW - pyrolysis AB - The deposition of terrestrial‐derived permafrost particulate organic carbon (POC) has been recorded in major Arctic river deltas. However, associated transport pathways of permafrost POC from the watershed to the coast have not been well constrained. Here we utilized a combination of ramped pyrolysis‐oxidation radiocarbon analysis (RPO 14C) along with lignin biomarkers, to track the linkages between soils and river and delta sediments. Surface and deep soils showed distinct RPO thermographs which may be related to degradation and organo‐mineral interaction. Soil material in the bed load of the river channel was mostly derived from deep old permafrost. Both surface and deep soils were transported and deposited to the coast. Hydrodynamic sorting and barrier island protection played important roles in terrestrial‐derived permafrost POC deposition near the coast. On a large scale, ice processes (e.g., ice gauging and strudel scour) and ocean currents controlled the transport and distribution of permafrost POC on the Beaufort Shelf. VL - 44 UR - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GL075543 IS - 22 ER -