Spatial Variation in Sediment Organic Carbon Distribution across the Alaskan Beaufort Sea Shelf

• Main Authors: Richard B. Coffin, Joseph P. Smith, Brandon Yoza, Thomas J. Boyd, Michael T. Montgomery
• Format: Article in Journal/Newspaper
• Language: unknown
• Subjects: Beaufort Shelf; Cape Halkett; Barrow; Beaufort Sea; north slope; Point Barrow; Prudhoe Bay; Tundra; Alaska
• Online Access: https://www.mdpi.com/1996-1073/10/9/1265/pdf; https://www.mdpi.com/1996-1073/10/9/1265/

In September 2009, a series of sediment cores were collected across the Alaskan Beaufort Sea shelf-slope. Sediment and porewater organic carbon (OC) concentrations and stable carbon isotope ratios (δ 13 C) were measured to investigate spatial variations in sediment organic matter (OM) sources and distribution of these materials across the shelf. Cores were collected along three main nearshore (shelf) to offshore (slope) sampling lines (transects) from east-to-west along the North Slope of Alaska: Hammerhead (near Camden Bay), Thetis Island (near Prudhoe Bay), and Cape Halkett (towards Point Barrow). Measured sediment organic carbon (TOC) and porewater dissolved organic carbon (DOC) concentrations and their respective δ 13 C values were used to investigate the relative contribution of different OM sources to sediment OC pool cycled at each location. Sources of OM considered included: water column-sourced phytodetritus, deep sediment methane (CH 4 ), and terrestrial, tundra/river-sourced OM. Results of these measurements, when coupled with results from previous research and additional analyses of sediment and porewater composition, show a pattern of spatial variation in sediment OC concentrations, OM source contributions, and OM cycled along the Alaskan Beaufort Sea shelf. In general, measured sediment total organic carbon (TOC) concentrations, δ 13 C TOC values, porewater DOC concentrations, and δ 13 C DOC values are consistent with an east-to-west transport of modern Holocene sediments with higher OC concentrations primarily sourced from relatively labile terrestrial, tundra OM sources and phytodetritus along the Alaskan Beaufort shelf. Sediment transport along the shelf results in the medium-to-long term accumulation and burial of sediment OM focused to the west which in turn results in higher biogenic CH 4 production rates and higher upward CH 4 diffusion through the sediments resulting in CH 4 − AMO-sourced contribution to sediment OC westward along the shelf. Understanding current OM sources and ...