Carbon and Sediment
in the Nearshore of an Eroding Permafrost Coast: Herschel Island, Canada
Radosavljevic, Boris , Lantuit, H., and M. Fritz
COPER
0321 0320
0315 0310 0168
0167 01660165
USA
Canada
Beaufort Sea
1 km
$
-25 -15 -10 -5
-20 0
Depth (m)
Thermal and Wave Erosion Zone
Wave and Current Reworking Zone
Ice-Push Zone Temporary Depocentre?
Ice Blocks
Ice Gouging Zone
Ice
Sediment
Resuspension
Erosion Accretion
Erosion
Coast Parallel Sed. Transport
Coast Perpendicular Sed. Transport after Hequette and Barnes, 1990
Introduction
Study Area Methods
Results (Preliminary)
Sediment/Organic Carbon Coastal
Erosion
Nearshore
Atmosphere Shelf Rock
Record
Burial Export
Physical, chemical and biological
processes
Rock Record
Through the combination of
thermal abrasion and coastal ero- sion, arctic coasts are highly
threatened by climate change that result in extremely high rates of shoreline retreat. The eroded materials contain large fractions of organic carbon
whose release in nearshore
waters may affect coastal ecosys- tems, and possibly act as a posi- tive feedback to ongoing climate change (Fig.1).
Arctic erosion takes two forms:
1) “normal” shoreline retreat, and 2) through thermokarst features that act as point sources of re- leased sediments and carbon.
Previous workers suggest that deposition could occur within the nearshore. Submarine per- mafrost degradation and sea-
level rise are possibly creating ac- ccommodation space (Figs 2, 3).
Questions
This study focuses following questions:
• How is the cross-shore and longshore coastal morphology related to shoreface evolution?
• How does shoreface evolution in relate to sequestration of carbon and coastal erosion?
• What percentage of eroded sediment is buried within the near shore?
• How might the shoreface evolve given present trends of climate change and sea-level rise?
• What changes can be anticipated for sedimentary features such as Simpson Point, the site of the historic whaling settlement?
Fig. 1. The fate of sediments and organic carbon released by
coastal erosion.
Fig. 2. Conceptual model of shoreface processes in the Canadian Beaufort Sea.
Fig. 3. Shoreline retreat resulting from sea-level rise, the Bruun rule. Note deposition on lower shoreface.
Fig. 4. Map of Herschel Island showing sidescan coverage and locations of SVP profiles.
Fig. 6. Instruments and samples (purple) deliver data (grey) that answer relevant questions (blue) for the completion of study objectives.
Fig 7. The AWI RV Christine is equipped to perform sid- escan and seismic sur- veys.
An array of complementary geophysical and conventional geologic methods are applied in this study.
• interferometric sidescan sonar (coupled with a real-time kinematic GPS system)
• seismic sub-bottom profiler
• surface sediment samples
• sediment cores
The 2012 field season yielded sidescan bathymetry and surface sediment samples(Figs. 4, 8, 9). Additional sidescan-, seismic-, as well as the collection of surface grab samples and shallow cores is planned for the summer of 2013 (Fig. 9).
boris.radosavljevic@awi.de Have questions? Feel free to contact me!
Fig. 8. Hill-
shade of Pau- line Cove ba- thymetry ob- tained
during summer 2012. The bathymetric survey of
Pauline Cove has already revealed benthic fea- tures of cryo- genic or an- thropogenic origin that may indicate conditions favorable for deposition.
Fig. 9. Map of Herschel Island showing coverage of sidescan (yellow) and locations of surface grab samples (pink). Areas
shaded in green indicate future focus locations.
Cyan dots are sites of a prior study that aimed at characteriying terrestrail and marine carbon.
Validation/
Stratigraphy ∆14C, 210Pb,
137Cs, CNS grain size,
CNS, δ13C Bathymetry/
Imagery Seismic Short
Cores
Evolution of shoreface
Sedimentation/sequestration rates
Surface
Sediment Samples Multibeam/
Sidescan
Characterize sediments/carbon
&
Identify sediment sources, sinks, and pathways
Eroded Volume
Deposited Volume
Sea-level Shoreline Retreat
t
1after Bruun, 1954
