scholarly journals Coastal Erosion of Permafrost Soils Along the Yukon Coastal Plain and Fluxes of Organic Carbon to the Canadian Beaufort Sea

2018 ◽  
Vol 123 (2) ◽  
pp. 406-422 ◽  
Author(s):  
Nicole J. Couture ◽  
Anna Irrgang ◽  
Wayne Pollard ◽  
Hugues Lantuit ◽  
Michael Fritz
Keyword(s):  
Organic Carbon ◽  
Coastal Plain ◽  
Coastal Erosion ◽  
Beaufort Sea ◽  
Permafrost Soils

scholarly journals Geochemistry of Coastal Permafrost and Erosion-Driven Organic Matter Fluxes to the Beaufort Sea Near Drew Point, Alaska

2021 ◽  
Vol 8 ◽  
Author(s):  
Emily M. Bristol ◽  
Craig T. Connolly ◽  
Thomas D. Lorenson ◽  
Bruce M. Richmond ◽  
Anastasia G. Ilgen ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Late Pleistocene ◽  
21St Century ◽  
Marine Sediments ◽  
Coastal Erosion ◽  
Beaufort Sea ◽  
The Arctic ◽  
The Holocene ◽  
Kuparuk River

Accelerating erosion of the Alaska Beaufort Sea coast is increasing inputs of organic matter from land to the Arctic Ocean, and improved estimates of organic matter stocks in eroding coastal permafrost are needed to assess their mobilization rates under contemporary conditions. We collected three permafrost cores (4.5–7.5 m long) along a geomorphic gradient near Drew Point, Alaska, where recent erosion rates average 17.2 m year−1. Down-core patterns indicate that organic-rich soils and lacustrine sediments (12–45% total organic carbon; TOC) in the active layer and upper permafrost accumulated during the Holocene. Deeper permafrost (below 3 m elevation) mainly consists of Late Pleistocene marine sediments with lower organic matter content (∼1% TOC), lower C:N ratios, and higher δ13C values. Radiocarbon-based estimates of organic carbon accumulation rates were 11.3 ± 3.6 g TOC m−2 year−1 during the Holocene and 0.5 ± 0.1 g TOC m−2 year−1 during the Late Pleistocene (12–38 kyr BP). Within relict marine sediments, porewater salinities increased with depth. Elevated salinity near sea level (∼20–37 in thawed samples) inhibited freezing despite year-round temperatures below 0°C. We used organic matter stock estimates from the cores in combination with remote sensing time-series data to estimate carbon fluxes for a 9 km stretch of coastline near Drew Point. Erosional fluxes of TOC averaged 1,369 kg C m−1 year−1 during the 21st century (2002–2018), nearly doubling the average flux of the previous half-century (1955–2002). Our estimate of the 21st century erosional TOC flux year−1 from this 9 km coastline (12,318 metric tons C year−1) is similar to the annual TOC flux from the Kuparuk River, which drains a 8,107 km2 area east of Drew Point and ranks as the third largest river on the North Slope of Alaska. Total nitrogen fluxes via coastal erosion at Drew Point were also quantified, and were similar to those from the Kuparuk River. This study emphasizes that coastal erosion represents a significant pathway for carbon and nitrogen trapped in permafrost to enter modern biogeochemical cycles, where it may fuel food webs and greenhouse gas emissions in the marine environment.

Land-to-ocean fluxes and biolability of organic matter eroding along the Beaufort Sea coast near Drew Point, Alaska

2021 ◽  
Author(s):  
Emily Bristol ◽  
Craig Connolly ◽  
Thomas Lorenson ◽  
Bruce Richmond ◽  
Anastasia Ilgen ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Active Layer ◽  
Late Pleistocene ◽  
Coastal Erosion ◽  
Organic Matter Content ◽  
Beaufort Sea ◽  
The Arctic ◽  
Series Data ◽  
Sea Coast

<p>Coastal erosion rates are increasing along the Alaskan Beaufort Sea coast due to increases in wave action, the increasing length of the ice-free season, and warming permafrost. These eroding permafrost coastlines transport organic matter and inorganic nutrients to the Arctic Ocean, likely fueling biological production and CO<sub>2</sub> emissions. To assess the impacts of Arctic coastal erosion on nearshore carbon and nitrogen cycling, we examined geochemical profiles from eroding coastal bluffs and estimated annual organic matter fluxes from 1955 to 2018 for a 9 km stretch of coastline near Drew Point, Alaska. Additionally, we conducted a laboratory incubation experiment to examine dissolved organic carbon (DOC) leaching and biolability from coastal soils/sediments added to seawater.</p><p>Three permafrost cores (4.5 – 7.5 m long) revealed that two distinct horizons compose eroding bluffs near Drew Point: Holocene age, organic-rich (~12-45% total organic carbon; TOC) terrestrial soils and lacustrine sediments, and below, Late Pleistocene age marine sediments with lower organic matter content (~1% TOC), lower carbon to nitrogen ratios, and higher δ<sup>13</sup>C-TOC values. Organic matter stock estimates from the cores, paired with remote sensing time-series data, show that erosional TOC fluxes from this study coastline averaged 1,369 kg C m<sup>−1</sup> yr<sup>−1</sup> during the 21<sup>st</sup> century, nearly double the average flux of the previous half century. Annual TOC flux from this 9 km coastline is now similar to the annual TOC flux from the Kuparuk River, the third largest river draining the North Slope of Alaska.</p><p>Experimental work demonstrates that there are distinct differences in DOC leaching yields and the fraction of biodegradable DOC across soil/sediment horizons. When core samples were submerged in seawater for 24 hours, the Holocene age organic-rich permafrost leached the most DOC in seawater (~6.3 mg DOC g<sup>-1</sup> TOC), compared to active layer soils and Late-Pleistocene marine-derived permafrost (~2.5 mg DOC g<sup>-1</sup> TOC). Filtered leachates were then incubated aerobically in the dark for 26 and 90 days at 20°C to examine biodegradable DOC (i.e. the proportion of DOC lost due to microbial uptake or remineralization). Of this leached DOC, Late Pleistocene permafrost was the most biolabile over 90 days (31 ± 7%), followed by DOC from active layer soils (24 ± 5%) and Holocene-age permafrost (14% ± 3%). If we scale these results to a typical 4 m tall eroding bluff at Drew Point, we expect that ~341 g DOC m<sup>-2 </sup>will rapidly leach, of which ~25% is biodegradable. These results demonstrate that eroding permafrost bluffs are an increasingly important source of biolabile DOC, likely contributing to greenhouse gas emissions and marine production in the coastal environment.</p>

Mobilization of aged carbon via meltwater floods and coastal erosion in the Canadian Arctic during the last deglaciation

2021 ◽  
Author(s):  
Junjie Wu ◽  
Gesine Mollenhauer ◽  
Ruediger Stein ◽  
Jens Hefter ◽  
Kirsten Fahl ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Coastal Erosion ◽  
Drainage System ◽  
Beaufort Sea ◽  
Sediment Flux ◽  
Biological Degradation ◽  
Last Deglaciation ◽  
Marine Organic Matter ◽  
Ocean Carbon

<p>It is consensus that the deglacial changes in ocean carbon storage and circulation play a role in regulating atmospheric CO<sub>2</sub>. However, emerging evidence suggests that the rapid deglacial CO<sub>2</sub> rises can in part be attributed to large quantities of pre-aged carbon being released from degrading permafrost. In this study, we apply a radiocarbon approach on both terrestrial compounds (high molecular weight fatty acids; HWM-FA) and bulk organic carbon from a well-studied core ARA04C/37 from the Canadian Beaufort Sea. Based on our records, substantial amounts of ancient carbon were supplied from land to the ocean during the mid-late deglaciation (14.5-10 cal. kyr BP) by frequent high sediment flux events. Because the core location is strongly influenced by the Mackenzie River discharge, sediments only contain minor contributions from marine organic matter, allowing to consider mainly two terrestrial sources to explain the characteristics of bulk sedimentary organic matter. The terrestrial HMW-FA are taken to represent the biospheric carbon, and their age differences from the bulk organic carbon are explained by petrogenic carbon input. During the Younger Dryas, ice-sheet melting and meltwater outbursts enhanced petrogenic carbon contributions, suggesting a major source in the hinterland drainage system. During the rapid sea-level rise (meltwater pulses 1a and 1b), the very old organic carbon and comparable ages between biospheric carbon and bulk organic carbon indicate the occurrence of permafrost carbon remobilization primarily via coastal erosion while petrogenic carbon from the drainage system was found negligible. Remobilized ancient permafrost carbon is commonly regarded to be highly bioavailable, while petrogenic carbon is likely more recalcitrant to biological degradation. Our records thus suggest that the release of ancient carbon to the Beaufort Sea had the strongest impact on the atmospheric CO<sub>2</sub> level and contributed to its rapid increases during the B/A and Pre-Boreal when permafrost deposits along the coast were eroded.</p>

scholarly journals Ground ice, organic carbon and soluble cations in tundra permafrost soils and sediments near a Laurentide ice divide in the Slave Geological Province, Northwest Territories, Canada

2020 ◽  
Vol 14 (12) ◽  
pp. 4341-4364
Author(s):  
Rupesh Subedi ◽  
Steven V. Kokelj ◽  
Stephan Gruber
Keyword(s):  
Organic Carbon ◽  
Landscape Change ◽  
Ice Sheet ◽  
Canadian Arctic ◽  
Landscape Changes ◽  
Ground Ice ◽  
Basal Ice ◽  
Permafrost Soils ◽  
Western Arctic ◽  
Mineral Soils

Abstract. The central Slave Geological Province is situated 450–650 km from the presumed spreading centre of the Keewatin Dome of the Laurentide Ice Sheet, and it differs from the western Canadian Arctic, where recent thaw-induced landscape changes in Laurentide ice-marginal environments are already abundant. Although much of the terrain in the central Slave Geological Province is mapped as predominantly bedrock and ice-poor, glacial deposits of varying thickness occupy significant portions of the landscape in some areas, creating a mosaic of permafrost conditions. Limited evidence of ice-rich ground, a key determinant of thaw-induced landscape change, exists. Carbon and soluble cation contents in permafrost are largely unknown in the area. Twenty-four boreholes with depths up to 10 m were drilled in tundra north of Lac de Gras to address these regional gaps in knowledge and to better inform projections and generalizations at a coarser scale. Excess-ice contents of 20 %–60 %, likely remnant Laurentide basal ice, are found in upland till, suggesting that thaw subsidence of metres to more than 10 m is possible if permafrost were to thaw completely. Beneath organic terrain and in fluvially reworked sediment, aggradational ice is found. The variability in abundance of ground ice poses long-term challenges for engineering, and it makes the area susceptible to thaw-induced landscape change and mobilization of sediment, solutes and carbon several metres deep. The nature and spatial patterns of landscape changes, however, are expected to differ from ice-marginal landscapes of western Arctic Canada, for example, based on greater spatial and stratigraphic heterogeneity. Mean organic-carbon densities in the top 3 m of soil profiles near Lac de Gras are about half of those reported in circumpolar statistics; deeper deposits have densities ranging from 1.3–10.1 kg C m−3, representing a significant additional carbon pool. The concentration of total soluble cations in mineral soils is lower than at previously studied locations in the western Canadian Arctic. This study can inform permafrost investigations in other parts of the Slave Geological Province, and its data can support scenario simulations of future trajectories of permafrost thaw. Preserved Laurentide basal ice can support new ways of studying processes and phenomena at the base of an ice sheet.

scholarly journals A 50 % increase in the mass of terrestrial particles delivered by the Mackenzie River into the Beaufort Sea (Canadian Arctic Ocean) over the last 10 years

2015 ◽  
Vol 12 (11) ◽  
pp. 3551-3565 ◽  
Author(s):  
D. Doxaran ◽  
E. Devred ◽  
M. Babin
Keyword(s):  
Organic Carbon ◽  
Arctic Ocean ◽  
Suspended Solids ◽  
Beaufort Sea ◽  
Freshwater Discharge ◽  
The Arctic ◽  
Field Observations ◽  
The Arctic Ocean ◽  
Arctic Rivers ◽  
Mackenzie River

Abstract. Global warming has a significant impact on the regional scale on the Arctic Ocean and surrounding coastal zones (i.e., Alaska, Canada, Greenland, Norway and Russia). The recent increase in air temperature has resulted in increased precipitation along the drainage basins of Arctic rivers. It has also directly impacted land and seawater temperatures with the consequence of melting permafrost and sea ice. An increase in freshwater discharge by main Arctic rivers has been clearly identified in time series of field observations. The freshwater discharge of the Mackenzie River has increased by 25% since 2003. This may have increased the mobilization and transport of various dissolved and particulate substances, including organic carbon, as well as their export to the ocean. The release from land to the ocean of such organic material, which has been sequestered in a frozen state since the Last Glacial Maximum, may significantly impact the Arctic Ocean carbon cycle as well as marine ecosystems. In this study we use 11 years of ocean color satellite data and field observations collected in 2009 to estimate the mass of terrestrial suspended solids and particulate organic carbon delivered by the Mackenzie River into the Beaufort Sea (Arctic Ocean). Our results show that during the summer period, the concentration of suspended solids at the river mouth, in the delta zone and in the river plume has increased by 46, 71 and 33%, respectively, since 2003. Combined with the variations observed in the freshwater discharge, this corresponds to a more than 50% increase in the particulate (terrestrial suspended particles and organic carbon) export from the Mackenzie River into the Beaufort Sea.

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

Energies ◽  
2017 ◽  
Vol 10 (9) ◽  
pp. 1265 ◽  
Author(s):  
Richard Coffin ◽  
Joseph Smith ◽  
Brandon Yoza ◽  
Thomas Boyd ◽  
Michael Montgomery
Keyword(s):  
Organic Carbon ◽  
Spatial Variation ◽  
Beaufort Sea ◽  
Carbon Distribution ◽  
Sediment Organic Carbon

Organic carbon and colloids in the Mackenzie River and Beaufort Sea

1989 ◽  
Vol 26 (4) ◽  
pp. 371-378 ◽  
Author(s):  
Brian G Whitehouse ◽  
Robie W Macdonald ◽  
Kazuo Iseki ◽  
Mark B Yunker ◽  
Fiona A McLaughlin
Keyword(s):  
Organic Carbon ◽  
Beaufort Sea ◽  
Mackenzie River
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