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Many complex fjord systems cross British Columbia's coastline. A 70 year (1951–2020) time series analysis of temperature, salinity, and oxygen in four such fjords between ∼54 and 50oN (Douglas Channel, Rivers Inlet, Knight Inlet and Bute Inlet) shows that changes were greatest in deep waters between the sill and the bottom. In Rivers, Knight and Bute Inlet, the deep water temperature increased by 1.2–1.3°C over 70 years, up to two times the global average for open ocean waters at corresponding depths, while salinity increased by 0.1–0.2, and oxygen decreased by 0.4–0.7 mLL−1. The most northern inlet, Douglas Channel, showed a temperature increase of 0.8°C from 1951 to 2016, while trends in oxygen and salinity were not statistically significant. An analysis of Apparent Oxygen Utilization suggests that the deep waters in Douglas Channel are more readily exchanged with the outer coast than the three other fjords. Plain Language Summary: Glacially carved fjords draw their deep waters from adjacent offshore ocean basins through a combination of upwelling, cross‐shelf transport, tidal mixing and estuarine circulation related processes. We studied data spanning seven decades from four such systems covering four degrees of latitude along the Canadian Pacific and found that fjord deep waters below sill depth were warming two times faster than their offshore source waters. Changes in temperature were accompanied by significant trends of decreased oxygen concentrations and increased salinity. Potential processes explaining these anomalous responses to climate change are discussed. Key Points: Temperature and oxygen data from four fjords (Rivers, Knight, and Bute Inlets and Douglas Channel) from 1951 to 2020 were examinedOver 70 years, deep water has warmed by up to 1.3°C and lost up to 0.7 mLL−1 of oxygen, with evidence of accelerated warming since 2016Deep warming and deoxygenation trends are statistically alike in at least three of the four fjords, suggesting similar drivers [ABSTRACT FROM AUTHOR]

A 15‐year (2004–2018) record of mooring observations from the upper 50 m ocean in the eastern Eurasian Basin reveals increased current speeds and shear, associated with an increasing coupling between wind, ice, and oceanic currents and their vertical shear over 2004–2018, particularly in summer. Substantial increases in both current speeds and shears in the upper 50 m are dominated by a two times amplification of currents in the semidiurnal band, which includes tides and wind‐forced near‐inertial oscillations. For the first time the strengthened upper ocean currents and shear are observed to coincide with weakening stratification. This coupling links the Atlantic Water heat to the sea ice, a consequence of which would be reducing regional sea ice volume. These results point to a new positive feedback mechanism in which reduced sea ice extent facilitates more energetic inertial oscillations and associated upper‐ocean shear, thus leading in enhanced ventilation of the Atlantic water. Plain Language Summary: Previous studies demonstrated that in recent years density gradients above the warm and salty intermediate (~150–900 m) water of Atlantic origin in the eastern Arctic Ocean have weakened, allowing stronger upward transport heat to the bottom of the sea ice. Using mooring observations, we show that this weakening of stratification has been accompanied by stronger upper‐ocean currents and their vertical shear and by increasing coupling between the wind and sea ice with upper ocean currents and shear. Most of this enhanced energy and shear is in the semidiurnal band, which includes baroclinic tides and wind‐driven inertial oscillations. The increased shear together with the weakening stratification indicate a greater potential for shear‐driven turbulent mixing. We propose a new process, the ice/ocean‐heat positive feedback, that can accelerate current sea ice loss and impede the rate of recovery of eastern Arctic sea ice even if large‐scale climate warming conditions relax. Key Points: Currents and associated shear in the upper 50 m in the eastern Eurasian Basin are increased in the 2010sIncreased currents and shear are dominated by accelerating currents in the semidiurnal (inertial and tidal) bandThere was an increasing coupling between wind, ice, and oceanic currents in the eastern Eurasian Basin over 2004–2018 [ABSTRACT FROM AUTHOR]

The catastrophic August 2014 Mount Polley tailings spill, the second largest ever documented, sent ~18 Mm3 of waste plunging to the bottom of the >100 m deep West Basin of Quesnel Lake, British Columbia, a critical West Coast salmon habitat. To understand the impact of the spill on the lake, including the fate of suspended solids, we examine changes in physical water properties over 11 years (2006–2017) using water column profiles, moored timeseries, and satellite imagery. Contaminated waters were initially largely confined to the hypolimnion; however, during autumn 2014 turnover, turbid waters were mixed to the surface, resulting in the clear blue lake turning bright green. Twelve months after the spill, the lake's temperature, conductivity, and turbidity temporarily returned to pre‐spill conditions; however, initiation of mine effluent discharge in late 2015 was associated with a subsequent 15 μS cm−1 conductivity increase above historic values. Importantly, a post‐spill 1–2.5 formazin turbidity unit hypolimnetic turbidity increase was observed during spring and fall turnovers of 2015–2017, which appeared to be due to resuspension of a thin layer of unconsolidated spill‐related material from the lake bed driven by large internal seiche motions. This process implies spill contaminants may be seasonally mobilized into the water column, with potentially detrimental impacts on aquatic ecology. Our findings underscore that basin‐scale physical processes, including seasonal turnover and internal seiches, must be accounted for, even in deep lakes, to understand the long‐term impact of the ever increasing number of tailings spills into aquatic ecosystems. Plain Language Summary: The catastrophic failure of the Mount Polley copper and gold mine tailings pond dam in August 2014 was, at the time, the largest mine‐related spill ever documented. The turbid torrent of mine waste plunged to the bottom of the near pristine waters of Quesnel Lake, British Columbia, critical habitat for West Coast salmon stocks. Despite the scale of the spill, there was surprisingly little visible evidence of it at the surface of the lake in the months following. But what happened below the surface? Using 11 years of water column measurements we show that as the lake mixed from top to bottom (called turnover) that autumn the contaminated deep water was brought to the surface, abruptly changing the color of the clearblue lake to an abnormal bright green color—a change readily visible from space. Since the spill the turbidity of the lake has increased during spring and autumn turnover, apparently due to resuspension of spill material off the lake bottom driven by basin‐scale wave oscillations. This process, and the ongoing discharge of excess mine waste water directly into the lake, raises concerns over the seasonal mobilization of mine contaminants and their impact on aquatic ecosystems. Key Points: Quesnel Lake turned bright green when turbid spill material trapped in the hypolimnion mixed to the surface during autumn 2014 turnoverSeasonal turbidity increases since the spill are likely due to resuspension of spill‐related bottom sediment by internal seichesPhysical dynamics are key to understanding the long‐term impact of acute and chronic mine spills even in deep aquatic systems [ABSTRACT FROM AUTHOR]

A survey of 25 coastal-draining rivers across the Canadian Arctic Archipelago (CAA) shows that these systems are distinct from the largest Arctic rivers that drain watersheds extending far south of the Arctic circle. Observations collected from 2014 to 2016 illustrate the influences of seasonal hydrology, bedrock geology, and landscape physiography on each river's inorganic geochemical characteristics. Summertime data show the impact of coincident gradients in lake cover and surficial geology on river geochemical signatures. In the north and central CAA, drainage basins are generally smaller, underlain by sedimentary bedrock, and their hydrology is driven by seasonal precipitation pulses that undergo little modification before they enter the coastal ocean. In the southern CAA, a high density of lakes stores water longer within the terrestrial system, permitting more modification of water isotope and geochemical characteristics. Annual time-series observations from two CAA rivers reveal that their concentration-discharge relationships differ compared with those of the largest Arctic rivers, suggesting that future projections of dissolved ion fluxes from CAA rivers to the Arctic Ocean may not be reliably made based on compositions of the largest Arctic rivers alone, and that rivers draining the CAA region will likely follow different trajectories of change under a warming climate. Understanding how these small, coastal-draining river systems will respond to climate change is essential to fully evaluate the impact of changing freshwater inputs to the Arctic marine system. [ABSTRACT FROM AUTHOR]

Evidence of microbial zonation in the open ocean is rapidly accumulating, but while the distribution of communities is often described according to depth, the other physical factors structuring microbial diversity and function remain poorly understood. Here we identify three different water masses in the North Water (eastern Canadian Arctic), defined by distinct temperature and salinity characteristics, and show that they contained distinct archaeal communities. Moreover, we found that one of the water masses contained an increased abundance of the archaeal alpha-subunit of the ammonia monooxygenase gene ( amoA) and accounted for 70% of the amoA gene detected overall. This indicates likely differences in putative biogeochemical capacities among different water masses. The ensemble of our results strongly suggest that the widely accepted view of depth stratification did not explain microbial diversity, but rather that parent water masses provide the framework for predicting communities and potential microbial function in an Arctic marine system. Our results emphasize that microbial distributions are strongly influenced by oceanic circulation, implying that shifting currents and water mass boundaries resulting from climate change may well impact patterns of microbial diversity by displacing whole biomes from their historic distributions. This relocation could have the potential to establish a substantially different geography of microbial-driven biogeochemical processes and associated oceanic production. [ABSTRACT FROM AUTHOR]

Kamloops Lae in central British Columbia is a deep, intermontane lake fed by the strong and seasonally variable flows of the Thompson River. Considerations of lake-river interaction, supported by physical and geological evidence, suggest that sediment transport and deposition within the lake is controlled by three interdependent but distinct processes: delta progradation at the lake-river confluence which results in delta topset and forest bedding; sediment density surges originating along the delta face which result in turbidite sequences lakeward from the base of the delta; and dispersal by the interflowing river plume which, due to Coriolis effects, results in a higher sedimentation rate and greater fraction of coarser material along the right-hand Side (Northern Hemisphere) of the lake in the direction of flow. [ABSTRACT FROM AUTHOR]