Spatial Variation in Sediment Organic Carbon Distribution across the Alaskan Beaufort Sea Shelf
Open Access
Abstract
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 (δ13C) 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 δ13C 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 (CH4), 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, δ13CTOC values, porewater DOC concentrations, and δ13CDOC 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 CH4 production rates and higher upward CH4 diffusion through the sediments resulting in CH4−AMO-sourced contribution to sediment OC westward along the shelf. Understanding current OM sources and distributions along the Alaskan Beaufort shelf is important for enhancing models of carbon cycling in Arctic coastal shelf systems. This will help support the prediction of the climate response of the Arctic created in the face of future warming scenarios.Keywords
This publication has 56 references indexed in Scilit:
- Methane hydrate-bearing seeps as a source of aged dissolved organic carbon to the oceansNature Geoscience, 2010
- Origin and fate of particulate organic matter in the southern Beaufort Sea – Amundsen Gulf region, Canadian ArcticEstuarine, Coastal and Shelf Science, 2010
- Microbial activity in surficial sediments overlying acoustic wipeout zones at a Gulf of Mexico cold seepGeochemistry, Geophysics, Geosystems, 2008
- Contrasting lipid biomarker composition of terrestrial organic matter exported from across the Eurasian Arctic by the five great Russian Arctic riversGlobal Biogeochemical Cycles, 2008
- Flux and age of dissolved organic carbon exported to the Arctic Ocean: A carbon isotopic study of the five largest arctic riversGlobal Biogeochemical Cycles, 2007
- Seafloor evidence for ice shelf flow across the Alaska–Beaufort margin of the Arctic OceanEarth Surface Processes and Landforms, 2007
- Heat and salt inhibition of gas hydrate formation in the northern Gulf of MexicoGeophysical Research Letters, 2005
- Sources of terrestrially-derived organic carbon in lower Mississippi River and Louisiana shelf sediments: implications for differential sedimentation and transport at the coastal marginMarine Chemistry, 2002
- Organic carbon isotope ratios (δ 13 C) of Arctic Amerasian Continental shelf sedimentsInternational Journal of Earth Sciences, 2000
- Seismic studies of a bottom simulating reflection related to gas hydrate beneath the continental margin of the Beaufort SeaJournal of Geophysical Research: Solid Earth, 1995