Seasonal and Interannual Changes in Ciliate and Dinoflagellate Species Assemblages in the Arctic Ocean (Amundsen Gulf, Beaufort Sea, Canada)

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.

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The Seasonal Variability of the Arctic Ocean Ekman Transport and Its Role in the Mixed Layer Heat and Salt Fluxes

Journal of Climate ◽

10.1175/jcli3892.1 ◽

2006 ◽

Vol 19 (20) ◽

pp. 5366-5387 ◽

Cited By ~ 61

Author(s):

Jiayan Yang

Keyword(s):

Arctic Ocean ◽

Mixed Layer ◽

Seasonal Variability ◽

Surface Wind ◽

Beaufort Sea ◽

Ekman Transport ◽

The Arctic ◽

Ekman Pumping ◽

Basin Scale ◽

The Arctic Ocean

Abstract The oceanic Ekman transport and pumping are among the most important parameters in studying the ocean general circulation and its variability. Upwelling due to the Ekman transport divergence has been identified as a leading mechanism for the seasonal to interannual variability of the upper-ocean heat content in many parts of the World Ocean, especially along coasts and the equator. Meanwhile, the Ekman pumping is the primary mechanism that drives basin-scale circulations in subtropical and subpolar oceans. In those ice-free oceans, the Ekman transport and pumping rate are calculated using the surface wind stress. In the ice-covered Arctic Ocean, the surface momentum flux comes from both air–water and ice–water stresses. The data required to compute these stresses are now available from satellite and buoy observations. But no basin-scale calculation of the Ekman transport in the Arctic Ocean has been done to date. In this study, a suite of satellite and buoy observations of ice motion, ice concentration, surface wind, etc., will be used to calculate the daily Ekman transport over the whole Arctic Ocean from 1978 to 2003 on a 25-km resolution. The seasonal variability and its relationship to the surface forcing fields will be examined. Meanwhile, the contribution of the Ekman transport to the seasonal fluxes of heat and salt to the Arctic Ocean mixed layer will be discussed. It was found that the greatest seasonal variations of Ekman transports of heat and salt occur in the southern Beaufort Sea in the fall and early winter when a strong anticyclonic wind and ice motion are present. The Ekman pumping velocity in the interior Beaufort Sea reaches as high as 10 cm day−1 in November while coastal upwelling is even stronger. The contributions of the Ekman transport to the heat and salt flux in the mixed layer are also considerable in the region.

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Effects of Vertical Water Mass Segregation on Bacterial Community Structure in the Beaufort Sea

Microorganisms ◽

10.3390/microorganisms7100385 ◽

2019 ◽

Vol 7 (10) ◽

pp. 385

Author(s):

Yunyun Fu ◽

Richard B. Rivkin ◽

Andrew S. Lang

Keyword(s):

Bacterial Community ◽

Sea Ice ◽

Arctic Ocean ◽

Community Composition ◽

Bacterial Communities ◽

Water Mass ◽

Beaufort Sea ◽

The Arctic ◽

The Arctic Ocean ◽

Mass Segregation

The Arctic Ocean is one of the least well-studied marine microbial ecosystems. Its low-temperature and low-salinity conditions are expected to result in distinct bacterial communities, in comparison to lower latitude oceans. However, this is an ocean currently in flux, with climate change exerting pronounced effects on sea-ice coverage and freshwater inputs. How such changes will affect this ecosystem are poorly constrained. In this study, we characterized the bacterial community compositions at different depths in both coastal, freshwater-influenced, and pelagic, sea-ice-covered locations in the Beaufort Sea in the western Canadian Arctic Ocean. The environmental factors controlling the bacterial community composition and diversity were investigated. Alphaproteobacteria dominated the bacterial communities in samples from all depths and stations. The Pelagibacterales and Rhodobacterales groups were the predominant taxonomic representatives within the Alphaproteobacteria. Bacterial communities in coastal and offshore samples differed significantly, and vertical water mass segregation was the controlling factor of community composition among the offshore samples, regardless of the taxonomic level considered. These data provide an important baseline view of the bacterial community in this ocean system that will be of value for future studies investigating possible changes in the Arctic Ocean in response to global change and/or anthropogenic disturbance.

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Simulated Interannual Variations of Freshwater Content and Sea Surface Height in the Beaufort Sea*

Journal of Climate ◽

10.1175/2011jcli4121.1 ◽

2012 ◽

Vol 25 (4) ◽

pp. 1079-1095 ◽

Cited By ~ 12

Author(s):

Z. Long ◽

W. Perrie ◽

C. L. Tang ◽

E. Dunlap ◽

J. Wang

Keyword(s):

Arctic Ocean ◽

Surface Wind ◽

Polar Vortex ◽

Beaufort Sea ◽

Sea Surface Height ◽

Sea Surface ◽

The Arctic ◽

Rapid Decline ◽

Interannual Variations ◽

The Arctic Ocean

Abstract The authors investigate the interannual variations of freshwater content (FWC) and sea surface height (SSH) in the Beaufort Sea, particularly their increases during 2004–09, using a coupled ice–ocean model (CIOM), adapted for the Arctic Ocean to simulate the interannual variations. The CIOM simulation exhibits a (relative) salinity minimum in the Beaufort Sea and a warm Atlantic water layer in the Arctic Ocean, which is similar to the Polar Hydrographic Climatology (PHC), and captures the observed FWC maximum in the central Beaufort Sea, and the observed variation and rapid decline of total ice concentration, over the last 30 years. The model simulations of SSH and FWC suggest a significant increase in the central Beaufort Sea during 2004–09. The simulated SSH increase is about 8 cm, while the FWC increase is about 2.5 m, with most of these increases occurring in the center of the Beaufort gyre. The authors show that these increases are due to an increased surface wind stress curl during 2004–09, which increased the FWC in the Beaufort Sea by about 0.63 m yr−1 through Ekman pumping. Moreover, the increased surface wind is related to the interannual variation of the Arctic polar vortex at 500 hPa. During 2004–09, the polar vortex had significant weakness, which enhanced the Beaufort Sea high by affecting the frequency of synoptic weather systems in the region. In addition to the impacts of the polar vortex, enhanced melting of sea ice also contributes to the FWC increase by about 0.3 m yr−1 during 2004–09.

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The delivery of mercury to the Beaufort Sea of the Arctic Ocean by the Mackenzie River

The Science of The Total Environment ◽

10.1016/j.scitotenv.2006.10.041 ◽

2007 ◽

Vol 373 (1) ◽

pp. 178-195 ◽

Cited By ~ 88

Author(s):

Daniel R. Leitch ◽

Jesse Carrie ◽

David Lean ◽

Robie W. Macdonald ◽

Gary A. Stern ◽

...

Keyword(s):

Arctic Ocean ◽

Beaufort Sea ◽

The Arctic ◽

The Arctic Ocean ◽

Mackenzie River

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Oceanographic Features of the Canadian Archipelago

Journal of the Fisheries Research Board of Canada ◽

10.1139/f57-030 ◽

1957 ◽

Vol 14 (5) ◽

pp. 731-769 ◽

Cited By ~ 24

Author(s):

W. B. Bailey

Keyword(s):

Arctic Ocean ◽

Beaufort Sea ◽

The Arctic ◽

Temperature Structure ◽

Vertical Temperature ◽

Baffin Bay ◽

The North ◽

The Arctic Ocean ◽

North Water ◽

Ice Floes

Oceanographic data collected during the first cruise of H.M.C.S. Labrador to the Canadian Arctic in August and September 1954 permit comparisons of the vertical temperature and salinity structures in Baffin Bay, the Canadian Archipelago and the Arctic Ocean. From a comparison of the temperature–salinity characteristics of the waters in the Arctic Ocean (Beaufort Sea) with those in Baffin Bay, it is found that: (a) the surface waters of the Arctic Ocean are much less saline than those in Baffin Bay, but minimum temperatures are the same (−1.8 °C), (b) the waters of the upper 200 m. in Baffin Bay are denser than those found at corresponding depths in the Arctic Ocean, (c) below 200 m., Arctic waters are the denser, and below 500 m. they are denser than any waters found in Baffin Bay, and (d) waters found at 250 m. in the Beaufort Sea, at 500 m. in Smith Sound, and at 1250 m. in central Baffin Bay, have identical temperature and salinity characteristics (−0.3 °C., 34.4‰).In addition the data permitted limited investigations into the effect of drifting ice floes on the vertical temperature structure of the water, the origin of the "north water", long-term variations in the oceanographic conditions in Baffin Bay, and dynamic calculations of currents and volume transports of the waters through the channels leading into Baffin Bay.

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Trends in the intensity of dense water cascading from the Arctic shelves due to ice cover reduction in the Arctic seas

Arctic and Antarctic Research ◽

10.30758/0555-2648-2021-67-4-318-327 ◽

2021 ◽

Vol 67 (4) ◽

pp. 318-327

Author(s):

F. K. Tuzov

Keyword(s):

Arctic Ocean ◽

Barents Sea ◽

Beaufort Sea ◽

Ice Cover ◽

The Arctic ◽

Arctic Seas ◽

Dense Water ◽

The Barents Sea ◽

The Arctic Ocean ◽

Shelf Seas

The article discusses the possible relationship between changes in the ice cover area of the shelf seas of the Arctic Ocean and the intensity of dense water cascading, based on calculation data obtained with the NEMO model for the period 1986–2010, with the findings issued at 5-day intervals and a spatial resolution of 1/10°. The cascading cases were calculated using an innovative method developed by the author. The work is based on the assumption that as the ice cover in the seas retreats, the formation of cooled dense water masses is intensified, which submerge and flow down the slope from the shelf to great depths. Thus, in the Arctic shelf seas, the mechanism of water densification due to cooling is added to the mechanism of water densification during ice formation, or, replaces it for certain regions. It was found that in the Barents Sea, the Laptev Sea and the Beaufort Sea, a decrease in the ice cover area causes an increase in the number of cases of cascading. However, in most of the Arctic seas, as the area of ice cover decreases, the number of cases of cascading also decreases. As a consequence, for the whole Arctic shelf area, the number of cases of cascading also decreases with decreasing ice cover. It is shown that in the Beaufort Sea the maximum number of cascading cases was observed in the winter period of 2007–2008, which was preceded by the summer minimum of the ice cover area in the Arctic Ocean. In the Barents Sea after 2000, a situation has been observed where the ice area has been decreasing to zero values, whereas the number of cascading cases has for some time (1 month approximately) remained close to high winter values. This possibly means that the cooling and densification of the waters in ice-free areas occurs due to thermal convection. Based on the calculation of the number of cases of cascading, it can be argued that the intensification of cascading due to a reduction in the ice cover is a feature of individual seas of the Arctic Ocean, those in which there is no excessive freshening of the upper water layer due to ice melting.

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Pigment signatures of phytoplankton communities in the Beaufort Sea

Biogeosciences Discussions ◽

10.5194/bgd-11-14489-2014 ◽

2014 ◽

Vol 11 (10) ◽

pp. 14489-14530 ◽

Cited By ~ 4

Author(s):

P. Coupel ◽

A. Matsuoka ◽

D. Ruiz-Pino ◽

M. Gosselin ◽

H. Claustre ◽

...

Keyword(s):

Arctic Ocean ◽

Environmental Changes ◽

Beaufort Sea ◽

Total Carbon ◽

The Arctic ◽

Clustering Methods ◽

Phytoplankton Assemblages ◽

Pigment Analysis ◽

Phytoplankton Communities ◽

The Arctic Ocean

Abstract. Phytoplankton are expected to respond to recent environmental changes of the Arctic Ocean. In terms of bottom-up control, modifying the phytoplankton distribution will ultimately affect the entire food web and carbon export. However, detecting and quantifying change in phytoplankton communities in the Arctic Ocean remains difficult because of the lack of data and the inconsistent identification methods used. Based on pigment and microscopy data sampled in the Beaufort Sea during summer 2009, we optimized the chemotaxonomic tool CHEMTAX for the assessment of phytoplankton community composition in an Arctic setting. The geographical distribution of the main phytoplankton groups was determined with clustering methods. Four phytoplankton assemblages were determined and related to bathymetry, nutrients and light availability. Surface waters across the whole survey region were dominated by prasinophytes and chlorophytes, whereas the subsurface chlorophyll maximum was dominated by the centric diatoms Chaetoceros socialis on the shelf and by two populations of nanoflagellates in the deep basin. Microscopic count showed a high contribution of the heterotrophic dinoflagellates Gymnodinium and Gyrodinium spp. to total carbon biomass, suggesting high grazing activity at this time of the year. However, CHEMTAX was unable to detect these dinoflagellates because they lack peridinin. The inclusion in heterotrophic dinoflagellates of the pigments of their prey potentially leads to incorrect group assignments and some misinterpretation of CHEMTAX. Thanks to the high reproducibility of pigment analysis, our results can serve as a baseline to assess change and spatial or temporal variability in phytoplankton populations.

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

Elem Sci Anth ◽

10.1525/elementa.321 ◽

2018 ◽

Vol 6 ◽

Cited By ~ 4

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.

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