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TitleTemperature measurements and thermal gradient estimates on the slope and shelf-edge region of the Beaufort Sea, Canada
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AuthorRiedel, M; Villinger, H; Asshoff, K; Kaul, N; Dallimore, S R
SourceGeological Survey of Canada, Open File 7725, 2015, 143 pages, https://doi.org/10.4095/296570
Year2015
PublisherNatural Resources Canada
Documentopen file
Lang.English
Mediadigital; on-line
File formatpdf
ProvinceNorthern offshore region
AreaBeaufort Sea; Beaufort Sea shelf; Beaufort Sea slope
Lat/Long WENS-138.0000 -134.0000 70.9667 69.9167
Subjectsgeophysics; fossil fuels; geophysical surveys; seismographs; seismological network; seismology; seismic waves; acoustic surveys; acoustic surveys, marine; bathymetry; continental shelf; continental slope; slope deposits; temperature; geothermal gradient; geothermal temperatures; permafrost; ground ice
Illustrationslocation maps; tables; photographs; profiles; plots; images; screen captures
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Location
 
Natural Resources Canada Library - Ottawa (Earth Sciences)
 
ProgramMarine Geohazards, Public Safety Geoscience
Released2015 05 29
AbstractIn situ temperature measurements were conducted at 63 gravity-core stations during the 2013 expedition with the CCGS Sir Wilfrid Laurier in the Canadian Beaufort Sea. Outriggers attached to the outside of the gravity core-barrel were used to mount portable miniature temperature loggers (MTL) for down-core in situ temperature measurements. Several sub-regions were investigated during the expedition including two shelf-slope crossings, three mud volcano-type expulsion features, as well as two canyon sites. The last site visited was at the Gary Knolls, just east of the Mackenzie Trough at water depths of less than 100 m. Overall, temperature data obtained from the MTLs were of high quality at most stations and the data acquisition technique was proven to be robust and easy to adapt in the Arctic. However, depth determination for each logger position remains the largest challenge as no additional pressure sensor was used with the MTLs. Instead, depths were estimated based on the apparent core penetration and the geometry of the outriggers. The most significant result from this work is the discovery of the very large apparent geothermal gradients associated with the two expulsion features (EF) Coke Cap and the mud volcano at 420 m water depth. Temperatures measured within the top 2.5 meter below seafloor suggest geothermal gradients of up to 2.94ºC/m (Station 96, 420m EF) and 1.37 ºC/m (Station 58, Coke Cap EF). Away from the centre of the EFs, thermal gradients decrease to values of 0.5ºC/m for Station 99 at the 420 m EF, and 0.92ºC/m at Station 21 at the Coke Cap EF. Temperature data across the slope-shelf transect and the two transects across the canyon heads did not reveal considerable geothermal gradients, but show a water-depth dependent trend in temperature. From deep to shallow water, temperature appear to decrease until the most negative temperature values are found on the shelf itself at water depths of ~100 m (-1.2 to -1.4ºC). Overall, data from the top 1.0 to 1.5 meter below seafloor are likely affected by seasonal variations in the water column temperature and may not be used to define geothermal gradients. With an optimal full penetration of the core barrel, the deepest temperature data are from ~2.3 mbsf, which limits the accuracy of the estimated geothermal gradients as only few data points (2 - 4) can be used in the calculations.
Summary(Plain Language Summary, not published)
Temperature measurements were conducted at 63 stations during the 2013 expedition with the CCGS Sir Wilfrid Laurier in the Canadian Beaufort Sea. Outriggers attached to the outside of a gravity core-barrel were used to mount portable miniature temperature loggers. Several sub-regions were investigated including two shelf-slope crossings, three mud volcano expulsion features, as well as two canyon sites. The last site visited was at the Gary Knolls, just east of the Mackenzie Trough. Temperature data obtained from the MTLs were of high quality. The most outstanding result is the occurrence of very large geothermal gradients associated with the two expulsion features Coke Cap and the mud volcano at 420m water depth. Data suggest geothermal gradients of up to 2.94ºC/m (Station #96, 420m EF) and 1.37 ºC/m (Station #58, Coke Cap EF).
GEOSCAN ID296570