McGhee Claire A.

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Last Name
McGhee
First Name
Claire A.
ORCID
0000-0003-3819-726X

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  • Article
    Turbidity currents can dictate organic carbon fluxes across river‐fed fjords: an example from Bute Inlet (BC, Canada)
    (American Geophysical Union, 2022-05-25) Hage, Sophie ; Galy, Valier ; Cartigny, Matthieu J. B. ; Heerema, Catharina ; Heijnen, Maarten S. ; Acikalin, Sanem ; Clare‬, Michael A. ; Giesbrecht, Ian J. W. ; Grocke, Darren R. ; Hendry, A. ; Hilton, Robert G. ; Hubbard, Stephen M. ; Hunt, James E. ; Lintern, D. Gwyn ; McGhee, Claire A. ; Parsons, Daniel R. ; Pope, Edward L. ; Stacey, Cooper David ; Sumner, Esther J. ; Tank, Suzanne E. ; Talling, Peter J.
    The delivery and burial of terrestrial particulate organic carbon (OC) in marine sediments is important to quantify, because this OC is a food resource for benthic communities, and if buried it may lower the concentrations of atmospheric CO2 over geologic timescales. Analysis of sediment cores has previously shown that fjords are hotspots for OC burial. Fjords can contain complex networks of submarine channels formed by seafloor sediment flows, called turbidity currents. However, the burial efficiency and distribution of OC by turbidity currents in river-fed fjords had not been investigated previously. Here, we determine OC distribution and burial efficiency across a turbidity current system within Bute Inlet, a fjord in western Canada. We show that 62% ± 10% of the OC supplied by the two river sources is buried across the fjord surficial (30–200 cm) sediment. The sandy subenvironments (channel and lobe) contain 63% ± 14% of the annual terrestrial OC burial in the fjord. In contrast, the muddy subenvironments (overbank and distal basin) contain the remaining 37% ± 14%. OC in the channel, lobe, and overbank exclusively comprises terrestrial OC sourced from rivers. When normalized by the fjord’s surface area, at least 3 times more terrestrial OC is buried in Bute Inlet, compared to the muddy parts of other fjords previously studied. Although the long-term (>100 years) preservation of this OC is still to be fully understood, turbidity currents in fjords appear to be efficient at storing OC supplied by rivers in their near-surface deposits.
  • Article
    Efficient preservation of young terrestrial organic carbon in sandy turbidity-current deposits
    (Hage, S., Galy, V. V., Cartigny, M. J. B., Acikalin, S., Clare, M. A., Grocke, D. R., Hilton, R. G., Hunt, J. E., Lintern, D. G., McGhee, C. A., Parsons, D. R., Stacey, C. D., Sumner, E. J., & Talling, P. J. (2020). Efficient preservation of young terrestrial organic carbon in sandy turbidity-current deposits. Geology, 48(9), 882-887., 2020-05-29) Hage, Sophie ; Galy, Valier ; Cartigny, Matthieu J. B. ; Acikalin, Sanem ; Clare‬, Michael A. ; Grocke, Darren R. ; Hilton, Robert G. ; Hunt, James E. ; Lintern, D. Gwyn ; McGhee, Claire A. ; Parsons, Daniel R. ; Stacey, Cooper David ; Sumner, Esther J. ; Talling, Peter J.
    Burial of terrestrial biospheric particulate organic carbon in marine sediments removes CO2 from the atmosphere, regulating climate over geologic time scales. Rivers deliver terrestrial organic carbon to the sea, while turbidity currents transport river sediment further offshore. Previous studies have suggested that most organic carbon resides in muddy marine sediment. However, turbidity currents can carry a significant component of coarser sediment, which is commonly assumed to be organic carbon poor. Here, using data from a Canadian fjord, we show that young woody debris can be rapidly buried in sandy layers of turbidity current deposits (turbidites). These layers have organic carbon contents 10× higher than the overlying mud layer, and overall, woody debris makes up >70% of the organic carbon preserved in the deposits. Burial of woody debris in sands overlain by mud caps reduces their exposure to oxygen, increasing organic carbon burial efficiency. Sandy turbidity current channels are common in fjords and the deep sea; hence we suggest that previous global organic carbon burial budgets may have been underestimated.