Preliminary lithostratigraphy of piston cores from the Beaufort Sea continental slope off northeastern Alaska

1991 ◽  
Author(s):  
R.L. Phillips ◽  
Arthur Grantz ◽  
M.W. Mullen ◽  
J.M. White
Keyword(s):  
Continental Slope ◽  
Beaufort Sea

scholarly journals Sea–ice and water dynamics and moonlight impact the acoustic backscatter diurnal signal over the eastern Beaufort Sea continental slope

2020 ◽  
Author(s):  
Igor A. Dmitrenko ◽  
Vladislav Petrusevich ◽  
Gérald Darnis ◽  
Sergei A. Kirillov ◽  
Alexander S. Komarov ◽  
...  
Keyword(s):  
Sea Ice ◽  
Continental Slope ◽  
Light Transmission ◽  
Acoustic Scattering ◽  
Water Layer ◽  
Beaufort Sea ◽  
Water Dynamics ◽  
Acoustic Backscatter ◽  
Intermediate Water ◽  
Upwelling And Downwelling

Abstract. A two-year-long time series of currents and acoustic backscatter from an Acoustic Doppler Current Profiler, moored over the eastern Beaufort Sea continental slope from October 2003 to September 2005, were used to assess dynamics and variability of the sound-scattering layer. It has been shown that acoustic backscatter is dominated by a synchronized diel vertical migration (DVM) of the zooplankton. Our results show that DVM timings (i) were synchronous with sunlight, and (ii) were modified by moonlight and sea-ice, which attenuates light transmission to the water column. Moreover, DVM is modified or completely disrupted during highly energetic current events. Thicker ice observed during winter 2004–2005 lowered the backscatter values, but favored extending DVM toward the midnight sun. In contrast to many previous studies, DVM occurred through the intermediate water layer during the ice-free season of the midnight sun in 2004. In 2005, the midnight sun DVM was likely masked by a high acoustic scattering generated by suspended particles. During full moon at low cloud cover, the nighttime moonlight illuminance led to zooplankton avoidance of the sub-surface layer disrupting DVM. Moreover, DVM was disrupted by upwelling, downwelling and eddy passing. We suggest that these deviations are consistent with DVM adjusting to avoid enhanced water dynamics. For upwelling and downwelling, zooplankton likely respond to the along-slope water dynamics dominated by surface- and depth-intensified flow, respectively. This drives zooplankton to adjust DVM by aggregating in the low or upper intermediate water layer for upwelling and downwelling, respectively. The baroclinic eddy reversed DVM below the eddy core.

Bowhead and Beluga Whale Distributions, Sighting Rates, and Habitat Associations in the Western Beaufort Sea in Summer and Fall 2009–16, with Comparison to 1982–91

ARCTIC ◽  
2018 ◽  
Vol 71 (2) ◽  
Author(s):  
Janet T. Clarke ◽  
Megan C. Ferguson ◽  
Amy L. Willoughby ◽  
Amelia A. Brower
Keyword(s):  
Habitat Use ◽  
Sea Ice ◽  
Continental Slope ◽  
Beaufort Sea ◽  
Habitat Associations ◽  
Bowhead Whale ◽  
Line Transect ◽  
Outer Continental Shelf ◽  
Beluga Whales ◽  
Shallow Habitat

We analyzed data from line-transect aerial surveys for marine mammals conducted in the western Beaufort Sea (shore to 72˚ N, 140˚–157˚ W) from July to October of 2009–16 to investigate the distribution, behaviors, sighting rates, and habitat use preferences of bowhead and beluga whales. The habitat use data allowed for direct comparison with data collected in the same area from 1982 to 1991. Both species are ice-adapted, migrating through leads in sea ice in spring, and are seasonal inhabitants of the western Beaufort Sea during summer and fall. From 2009 to 2016, bowheads were seen in all survey months, with the highest overall sighting rate (whales per km) in August. Bowhead sighting rates were highest in the whales’ preferred habitats: outer shelf habitat (51–200 m depth) in July and inner shelf-shallow habitat (≤ 20 m depth) in August, September, and October. Beluga whales were also seen in all survey months, with highest overall sighting rate in July. Beluga whales were overwhelmingly associated with continental slope habitat (201–2000 m depth) in all months. Bowhead distribution and depth preferences in summer months of 2009–16 differed from those observed in 1982–91, when bowheads were not seen during limited survey effort in July and preferred outer continental shelf habitat in August. These differences indicate that bowhead whale preference for shallow shelf habitat now occurs earlier in summer than it used to. Beluga distribution and depth preference remained similar between 1982–91 and 2009–16, with strong preference for continental slope during both periods. Differences in sea ice cover habitat association for both species are likely due more to the relative lack of sea ice in recent years compared to the earlier period than to shifts in habitat preference. Habitat partitioning between bowhead and beluga whales in the western Beaufort Sea remained evident except in July, when both species used continental slope habitat. In July – October 2009–16, the distribution, sighting rates, and behavior of both bowheads and belugas in the western Beaufort showed considerable interannual variation, which underscores the importance of annual sampling to accurate records of the complex western Beaufort Sea ecosystem.

scholarly journals Shelfbreak current over the Canadian Beaufort Sea continental slope: Wind‐driven events in January 2005

2016 ◽  
Vol 121 (4) ◽  
pp. 2447-2468 ◽  
Author(s):  
Igor A. Dmitrenko ◽  
Sergei A. Kirillov ◽  
Alexandre Forest ◽  
Yves Gratton ◽  
Denis L. Volkov ◽  
...  
Keyword(s):  
Continental Slope ◽  
Beaufort Sea ◽  
Slope Wind

scholarly journals Upwelling of Atlantic Water along the Canadian Beaufort Sea Continental Slope: Favorable Atmospheric Conditions and Seasonal and Interannual Variations

2016 ◽  
Vol 29 (12) ◽  
pp. 4509-4523 ◽  
Author(s):  
Sergei Kirillov ◽  
Igor Dmitrenko ◽  
Bruno Tremblay ◽  
Yves Gratton ◽  
David Barber ◽  
...  
Keyword(s):  
Continental Slope ◽  
Recent Decade ◽  
Beaufort Sea ◽  
Vertical Displacement ◽  
Atlantic Water ◽  
Wind Forcing ◽  
Atmospheric Conditions ◽  
Vertical Displacements ◽  
Highly Correlated ◽  
Favorable Conditions

Abstract The role of wind forcing on the vertical displacement of the −1°C isotherm and 33.8 isohaline depths was examined based on snapshots of historical (1950–2013) temperature and salinity profiles along the Mackenzie continental slope (Beaufort Sea). It is found that upwelling is correlated with along-slope northeast (T59°) winds during both ice-free and ice-covered conditions, although the wind impact is more efficient during the ice-free season. One of the most important factors responsible for vertical displacements of isopycnals is sustained wind forcing that can last for several weeks and even longer. It accounts for 14%–55% of total variance in isotherm/isohaline depths, although these numbers might be underestimated. The upwelling and downwelling events are discussed in the context of the interplay between two regional centers of action—the Beaufort high and Aleutian low—that control the wind pattern over the southern Beaufort Sea. The probability of upwelling-favorable wind occurrence is closely related to the sea level pressure difference between these two centers, as well as their geographical positions. The combined effect of both centers expressed as the SLP differences is highly correlated (0.68/0.66 for summer/winter) with occurrences of extreme upwelling-favorable northeast (NE) winds over the Mackenzie slope, although the Beaufort high plays a more important role. The authors also diagnosed the predominant upwelling-favorable conditions over the Mackenzie slope in the recent decade associated with the summertime amplification of the Beaufort high. The upwelling-favorable NE wind occurrences also demonstrate the significant but low (−0.30) correlation with Arctic Oscillation (AO) during both summer and winter seasons, whereas the high correlation with North Pacific index (NPI; −0.52) is obtained only for the ice-covered period.

scholarly journals Wind-forced depth-dependent currents over the eastern Beaufort Sea continental slope: Implications for Pacific water transport

Elem Sci Anth ◽  
2018 ◽  
Vol 6 ◽  
Author(s):  
Igor A. Dmitrenko ◽  
Sergei A. Kirillov ◽  
Paul G. Myers ◽  
Alexandre Forest ◽  
Bruno Tremblay ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Arctic Ocean ◽  
Continental Slope ◽  
Water Transport ◽  
Beaufort Sea ◽  
The Arctic ◽  
Pacific Water ◽  
Barotropic Flow ◽  
The Pacific ◽  
The Arctic Ocean

Pacific water contributes significantly to the Arctic Ocean freshwater budget. Recent increases in Arctic freshwater flux, also affected by the Pacific-derived Arctic water, impact the Atlantic overturning circulation with implications for global climate. The interannual variability of the Pacific water outflow remains poorly understood, partly due to different branches of the Pacific water flow in the Arctic Ocean. The shelfbreak current over the Beaufort Sea continental slope transports ~50% of the Pacific-derived water eastward along the Beaufort Sea continental slope towards the Canadian Archipelago. The oceanographic mooring deployed over the eastern Beaufort Sea continental slope in October 2003 recorded current velocities through depths of 28–108 m until September 2005. Data analysis revealed that these highly energetic currents have two different modes of depth-dependent behaviour. The downwelling-favourable wind associated with cyclones passing north of the Beaufort Sea continental slope toward the Canadian Archipelago generates depth-intensified shelfbreak currents with along-slope northeastward flow. A surface Ekman on-shore transport and associated increase of the sea surface heights over the shelf produce a cross-slope pressure gradient that drives an along-slope northeastward barotropic flow, in the same direction as the wind. In contrast, the upwelling-favourable wind associated with deep Aleutian Low cyclones over the Alaskan Peninsula and/or Aleutian Island Arc leads to surface-intensified currents with along-slope westward flow. This northeasterly wind generates a surface Ekman transport that moves surface waters offshore. The associated cross-slope pressure gradient drives an along-slope southwestward barotropic flow. The wind-driven barotropic flow generated by upwelling and downwelling is superimposed on the background bottom-intensified shelfbreak current. For downwelling, this flow amplifies the depth-intensified background baroclinic circulation with enhanced Pacific water transport towards the Canadian Archipelago. For upwelling, the shelfbreak current is reversed, which results in surface-intensified flow in the opposite direction. These results are supported by numerical simulations.

scholarly journals Upwelling on the continental slope of the Alaskan Beaufort Sea: Storms, ice, and oceanographic response

2009 ◽  
Vol 114 ◽  
Author(s):  
Robert S. Pickart ◽  
G. W. K. Moore ◽  
Daniel J. Torres ◽  
Paula S. Fratantoni ◽  
Roger A. Goldsmith ◽  
...  
Keyword(s):  
Continental Slope ◽  
Beaufort Sea

scholarly journals Freshwater Seepage Into Sediments of the Shelf, Shelf Edge, and Continental Slope of the Canadian Beaufort Sea

2018 ◽  
Vol 19 (9) ◽  
pp. 3039-3055 ◽  
Author(s):  
R. Gwiazda ◽  
C. K. Paull ◽  
S. R. Dallimore ◽  
H. Melling ◽  
Y. K. Jin ◽  
...  
Keyword(s):  
Continental Slope ◽  
Beaufort Sea ◽  
Shelf Edge

scholarly journals Biogeochemical evidence of anaerobic methane oxidation on active submarine mud volcanoes on the continental slope of the Canadian Beaufort Sea

2018 ◽  
Vol 15 (24) ◽  
pp. 7419-7433 ◽  
Author(s):  
Dong-Hun Lee ◽  
Jung-Hyun Kim ◽  
Yung Mi Lee ◽  
Alina Stadnitskaia ◽  
Young Keun Jin ◽  
...  
Keyword(s):  
Continental Slope ◽  
Distribution Patterns ◽  
Beaufort Sea ◽  
Anaerobic Oxidation Of Methane ◽  
Mud Volcanoes ◽  
Operational Taxonomic Units ◽  
Carbon Isotopic ◽  
Oxidation Of Methane ◽  
Lipid Biomarker ◽  
Archaeal Communities

Abstract. In this study, we report lipid biomarker patterns and phylogenetic identities of key microbial communities mediating anaerobic oxidation of methane (AOM) in active mud volcanoes (MVs) on the continental slope of the Canadian Beaufort Sea. The carbon isotopic compositions (δ13C) of sn-2- and sn-3-hydroxyarchaeol showed the highly 13C-depleted values (−114 ‰ to −82 ‰) associated with a steep depletion in sulfate concentrations within 0.7 m of sediment depths. This suggested the presence of methanotrophic archaea involved in sulfate-dependent AOM, albeit in a small amount. The ratio of sn-2-hydroxyarchaeol to archaeol (> 1) and operational taxonomic units (OTUs) indicated that the anaerobic methanotrophic archaea (ANME) clades ANME-2c and ANME-3 were involved in AOM. Higher δ13C values of archaeol and biphytanes (BPs; -55.2±10.0 ‰ and -39.3±13.0 ‰, respectively) suggested that archaeal communities were also assimilating AOM-derived inorganic carbon. Furthermore, the distinct distribution patterns of methanotrophs in the three MVs appears to be associated with varying intensities of ascending gas fluids. Consequently, our results suggest that the niche diversification of active mud volcanoes has shaped distinct archaeal communities that play important roles in AOM in the Beaufort Sea.

scholarly journals Sea-ice and water dynamics and moonlight impact the acoustic backscatter diurnal signal over the eastern Beaufort Sea continental slope

Ocean Science ◽  
2020 ◽  
Vol 16 (5) ◽  
pp. 1261-1283
Author(s):  
Igor A. Dmitrenko ◽  
Vladislav Petrusevich ◽  
Gérald Darnis ◽  
Sergei A. Kirillov ◽  
Alexander S. Komarov ◽  
...  
Keyword(s):  
Sea Ice ◽  
Continental Slope ◽  
Subsurface Layer ◽  
Acoustic Scattering ◽  
Water Layer ◽  
Beaufort Sea ◽  
Water Dynamics ◽  
Acoustic Backscatter ◽  
Intermediate Water ◽  
Upwelling And Downwelling

Abstract. A 2-year-long time series of currents and acoustic backscatter from an acoustic Doppler current profiler, moored over the eastern Beaufort Sea continental slope from October 2003 to September 2005, were used to assess the dynamics and variability of the sound-scattering layer. It has been shown that acoustic backscatter is dominated by a synchronized diel vertical migration (DVM) of zooplankton. Our results show that DVM timings (i) were synchronous with sunlight and (ii) were modified by moonlight and sea ice, which attenuates light transmission to the water column. Moreover, DVM is modified or completely disrupted during highly energetic current events. Thicker ice observed during winter–spring 2005 lowered the backscatter values but favored extending DVM toward the midnight sun. In contrast to many previous studies, DVM occurred through the intermediate water layer during the ice-free season of the midnight sun in 2004. In 2005, the midnight-sun DVM was likely impacted by a high acoustic scattering generated by suspended particles. During full moon at low cloud cover, the nighttime moonlight illuminance led to zooplankton avoidance of the subsurface layer, disrupting DVM. Moreover, DVM was disrupted by upwelling, downwelling, and eddy passing. We suggest that these deviations are consistent with DVM adjusting to avoid enhanced water dynamics. For upwelling and downwelling, zooplankton likely respond to the along-slope water dynamics dominated by surface- and depth-intensified flow, respectively. This drives zooplankton to adjust DVM by aggregating in the low or upper intermediate water layer for upwelling and downwelling, respectively. The baroclinic eddy reversed DVM below the eddy core.

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