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Submarine canyons are hot spots for topography‐internal wave interactions, with elevated mixing contributing to regional water mass transport and productivity. Two velocity time series compare and contrast internal waves deep inside Barkley Canyon to a nearby site on the shelf‐break slope of the Vancouver Island Continental Shelf. Elevation of internal wave energy occurs near topography, up to a factor of 10 above the slope and 100 in the canyon. All frequency bands display strong seasonal variability but weak interannual variability. Diurnal (K1) energy is sub‐inertial, trapped along topography, and forced locally through barotropic motions. Both sites have high near‐inertial (NI) energy linked to wind events, though fewer events are observed deep inside the canyon. At the slope site, near‐inertial energy is attenuated with depth, while in the canyon it is amplified near the bottom. Freely propagating semidiurnal (M2) energy appears focused near critical shelf‐break and canyon floor topography, due to local and remote baroclinic forcing. The high‐frequency internal wave continuum has enhanced near‐bottom energy at both sites (up to 7 × the Garrett‐Munk spectrum), and inferred dissipation rates, ɛ, reaching 10−7 W kg−1 near topography. Dissipation is most strongly correlated with semidiurnal energy variability at both sites, with secondary contributors that are site dependent. Forcing power law fits are ε∼M20.8+ $\varepsilon \sim {M}_{2}^{0.8}+$SubK10.6 ${\text{Sub}}_{{K}_{1}}^{0.6}$ on the slope, and ε∼M21.5+ $\varepsilon \sim {M}_{2}^{1.5}+$ NI0.2 in the canyon. There is also a build‐up of "shoulder" energy (PSh) near the buoyancy frequency, with a power law fit to dissipation of PSh ∼ ɛ0.3 at both sites. Plain Language Summary: Internal waves are sub‐surface waves that can mix ocean water, particularly over rough topography such as that found on continental slopes or in submarine canyons. Mixing is important for understanding ocean circulation, climate, and biological productivity. At Barkley Canyon on Canada's west coast, 4 years of current observations are used to study internal waves at both slope and canyon sites. These long‐term data allow for analysis of seasonal and year‐to‐year trends. The currents follow topography, and near‐bottom internal wave energy is generally increased. The observed seasonal patterns change little year‐to‐year. Internal waves occurring once‐a‐day or less are trapped along the slope, and result from once‐a‐day surface tides. Internal waves associated with the Earth's rotation are driven by wind—with only some events reaching the deep canyon. Internal waves occurring twice‐a‐day may be amplified by topography, and result from twice‐a‐day surface tides and internal waves from other underwater sites. Seasonal trends indicate that larger internal waves transfer energy to smaller, turbulent motions near topography, elevating mixing. There is evidence that this transfer of energy may continue to smaller scales than is typically observed. These findings can support models of mixing near topography and improve understanding of internal wave processes. Key Points: Analysis of 4 years of acoustic Doppler current profiler horizontal velocity data from Barkley Canyon and nearby slopeElevated internal wave energy and mixing near topography, with power law relationships to semidiurnal and site‐dependent secondary forcingBuild‐up of energy near the local buoyancy frequency with a power law relationship to dissipation [ABSTRACT FROM AUTHOR]

Observations of temperature, salinity, and oxygen on the southern Vancouver Island shelf show a large‐scale exchange of shelf water with offshore water, just offshore of a semi‐permanent recirculation, often termed the Juan de Fuca Eddy. The Eddy occupies a region where the shelf widens abruptly in the lee of a bank. The water in this Eddy is a mixture of offshore water and water from a buoyant coastal current. This water is well‐mixed along a mixing line in temperature‐salinity space, though it retains stratification, and is either rapidly mixed or has a long residence time. There is a less than 1 km wide temperature‐salinity front on the offshore side of this well‐mixed water that has no sign of instabilities. The clearest evidence of cross‐front transport is found during a tidally resolved survey over a bank. The transport is due to flows in the cross‐bank direction that also drive 50 m tall hydraulic jumps. Upstream of the Eddy, there is an along‐shelf current flowing equatorward. However, the whole current separates from the shelf before reaching the Eddy, in the lee of a bank, and is replaced by water from offshore. The separation event was also seen in sea‐surface temperatures from satellite images as a tongue of cool coastal water that is ejected offshore. Plain Language Summary: The southern Vancouver Island continental shelf is biologically productive due to high nutrient input from the Strait of Juan de Fuca and Salish Sea estuarine system and substantial cross‐shelf transport due to the complicated topography. Here, we present an intensive sampling of the Juan de Fuca Eddy region. The observations show that below the surface mixed layer, the water in the Eddy is low in oxygen, and has undergone substantial vertical and lateral mixing. In contrast to previous literature, we find that the low oxygen in the Eddy is likely because of respiration rather than being pulled from low‐oxygen water in the California Undercurrent. The observations also show a remarkable flow separation of the equatorward shelf current. The current is seen to detach and is pushed offshore. Such events are readily seen in satellite imagery, but our observations indicate that the separation extends the depth of the water column on the shelf, and that this separation may be partially driven by the local bathymetry. The separation is a very strong cross‐shelf exchange event, and transports substantial nutrient‐rich coastal water offshore to drive productivity in the deeper ocean adjacent to the continental slope. Key Points: The shelf break current along Vancouver Island separates downstream of a submarine bankOffshore water is drawn onto the shelf and forms a sharp semi‐persistent front with the Juan de Fuca EddyThe Eddy shows evidence of long residence times, and little evidence of deep‐water origin [ABSTRACT FROM AUTHOR]

A shortage of dissolved oxygen in seawater can adversely impact marine life and ecosystems. Low oxygen conditions at depth occur in many coastal regions, driven by both local productivity and remote changes in the source waters. A low‐oxygen dense pool of water is observed every summer over the mid‐shelf off southwest Vancouver Island in the Juan de Fuca Eddy region. We trace the dense pool waters back to their source using Lagrangian Particle tracking in an ocean model. The model accuracy is evaluated against a set of dense observations collected in August 2013. Only locations where the model represents water properties well are used as starting locations for the tracking. These locations are selected using a K‐Means clustering algorithm. Tracking particles backwards in time showed that the low oxygen dense pool is primarily composed of water from the California Undercurrent, shallower water from further offshore of the Washington shelf, and offshore water. Waters from the northern shelf were not a primary source even though summer currents are from the north. Correspondingly, the water primarily arrived in the south Vancouver Island region in spring, months before the cruise. A kernel density estimate shows the final water properties of the dense pool are well represented by this mixture. The dense water pathways up and onto the shelf are primarily through coastal submarine canyons in early summer. Combining high spatial resolution observations, a carefully evaluated numerical model, Lagrangian tracking, and statistical techniques reveal detailed answers not obtainable through a single method. Plain Language Summary: A shortage of dissolved oxygen in seawater can adversely impact marine life and ecosystems. A low‐oxygen dense pool of water is observed every summer over the mid‐shelf off southwest Vancouver Island. The dense pool waters are traced back to their source by tracking particles backwards in time using ocean currents from a numerical model. The California Undercurrent, shallower water from the south from further offshore of the Washington shelf, and offshore water contribute the most volume to the dense pool waters. Though summer currents are from the north in the region, they are not a major contributing source. The dense water pathways up and onto the shelf are primarily through the coastal submarine canyons and occur in early summer. Key Points: Using an evaluated numerical model, backward Lagrangian tracking, and kernel density estimation illuminates water mass originPrincipal pathways of the deep, low oxygen summer water onto the shelf are through the submarine canyonsLow‐oxygen deep summer water on the Vancouver Island shelf originates from the south, opposite to summer shelf currents [ABSTRACT FROM AUTHOR]

The tides in the Kitikmeot Sea, in the southern Canadian Arctic Archipelago, are found to be heavily influenced by seasonal sea‐ice formation and blocking in a strait. Data from a moored current profiler in Dease Strait exhibit strong tidal damping during wintertime seasonal sea‐ice cover, with 50%–60% reduction in tidal elevation and 65% reduction in tidal velocities. We used a 3D unstratified barotropic numerical tidal model of the region to show that the observed wintertime tidal damping likely requires both high sea‐ice friction and a partial sea‐ice blockage in Victoria Strait (VS), the eastern gateway of the Kitikmeot Sea, where tidal‐induced ridging causes thick, rough ice to accumulate over its shallow sill. Our analysis of the model shows different dynamics for the M2 and K1 tides. Both tidal constituents are dominated by the Atlantic tides entering through VS. Overall, ∼90% of the M2 tidal energy entering VS does not reach Dease Strait because, in addition to dissipation in VS (∼25%), it is significantly diverted into adjoining bays and around an amphidrome in eastern Queen Maud Gulf (∼65%). In contrast, the smaller K1 tide is less diverted into the subsidiary channels, after ∼20% dissipation in VS and only ∼25% in adjoining bays, it propagates far into the region and is amplified due to resonance in Dease Strait and Coronation Gulf, resulting in larger tidal height than the M2 tide in Coronation Gulf. Plain Language Summary: In the Canadian Arctic Archipelago tides influence the nutrient distribution, heat flux, and sea‐ice dynamics amid other processes. While most tidal models of the Arctic do not include the seasonal growth and melt of sea ice, we show that tides in the Kitikmeot Sea are greatly impacted by this. Tidal elevation and velocities from a moored current profiler in Dease Strait are damped 50%–65% during wintertime seasonal sea‐ice cover. In Victoria Strait (VS), the eastern gateway of the Kitikmeot Sea, thick, rough ice accumulates over the shallow sill. We use numerical models to show that our observed tidal damping in Dease Strait requires both large sea‐ice friction and a partial sea‐ice blockage in VS. Key Points: Tidal height and currents are damped >50% in winter, likely due to high sea‐ice friction and tidal‐induced sea‐ice blockages upstreamUpon entering the Kitikmeot Sea, the dominant Atlantic‐origin tides dissipate, resulting in relatively low tidal energyThe K1 tidal height is larger than the M2 tidal height in the western Kitikmeot Sea due to tidal resonance [ABSTRACT FROM AUTHOR]

The deployment of 206 surface drifters over 3 years in a fjord system in northern British Columbia allows examination of drift and dispersion in complex coastal regions on time scales up to 10 days. The surface drift is found to be seasonally variable, with stronger dispersion and outflows in the spring and fall, and negligible outflow in the summer. Dispersion at time scales less than 10 hr is well described by fractional Brownian motion, where the drifter tracks exhibit fractal characteristics with a dimension of 1.34 over scales of 2 to 13 km. Drifters are found to reach less energetic nearshore regions within 12–15 hr, which slows along‐channel dispersion. The comparison of the drifter statistics (from 2014–2016) with observations of the spatial distribution of oil sheen following an oil spill in 2006 shows that the drifter results provide a reasonable proxy for oil drift in this area. A statistical model for the extent of along‐channel transport of spilled oil is proposed for use in planning emergency response activities in the area. Plain Language Summary: This paper is an analysis of the movement of 206 surface drifting buoys (drifters), which were released in the Kitimat fjord system in northwestern British Columbia between 2014 and 2016. This fills a knowledge gap concerning drift of objects at the ocean surface in narrow fjord systems over times longer than 1 day. Drift is toward the ocean on average and stronger in the spring and fall than in the summer. Drifters move approximately twice as fast near midchannel than they do near the shorelines and are found to come in close proximity of the shoreline within 12–15 hr of being released. Consequently, this cross‐channel movement slows drift along the channel. Comparison with observations of sheening from a previous oil spill in the study region suggests that the drifters are an adequate proxy for spilled oil. A statistical model for the maximum likely extents of oil spills in the fjord system after times up to 10 days is proposed. Key Points: Analysis of ocean surface dynamics in a multiply connected fjord system from 3 years of drifter dataOver time scales longer than 15 hr interaction between the drifters and channel walls restrict along‐channel dispersionThe drifters are an adequate proxy for oil and results can be used for spill response planning [ABSTRACT FROM AUTHOR]

Submesoscale oceanic fronts (SFs), which typically occur on a spatial scale of 0.1–10 km, may have a large influence on the atmospheric surface layer (ASL). However, due to their short temporal‐spatial scales, evaluating their direct impact on this layer remains challenging and characterizing the nature of SF‐ASL interaction has not been done in the field. To address this, a study of the air‐sea response to SFs was conducted using observations collected during the Lagrangian Submesoscale Experiment, which took place in the northern Gulf of Mexico. This manuscript focuses on the meteorological measurements made from a pair of masts installed on the bow of the R/V Walton Smith. This work represents one of the first observation‐based investigations into the potential influence that SFs have on the ASL. Contemporaneous measurements from an X‐band marine radar, moving vessel profiler, and Lagrangian drifters were also used to analyze the SF dynamics. Systematic surface wind velocity changes over several cross‐frontal transects were observed, a process previously associated with mesoscale fronts. A comparison between the eddy covariance and parameterized (COARE 3.5) air‐sea fluxes revealed that the directly observed heat flux was 1.5 times larger than the bulk value in the vicinity of the SFs. This suggests that the hydrodynamic processes near the front enhance the local exchange of sensible and latent heat. Given the prevalence of SF over the global upper ocean, these findings suggest that these features may have a widely distributed and cumulative impact on air‐sea interactions. Plain Language Summary: The atmosphere responds to the ocean over all scales—from microscopic to planetary scales. Previous studies showed that surface wind and even the entire atmospheric boundary layer could be affected by the relatively large‐scale (10–1,000 km) temperature variations across the open ocean, for example, the Gulf Stream. However, the impacts of relatively small‐scale (100 m to 10 km) and rapidly (hours to days) evolving fronts are largely unknown due to the difficulty in actually observing the physical processes. As part of an ongoing effort to better understand surface material dispersion across the northern Gulf of Mexico, we conducted ship‐based measurements of air‐sea fluxes across near small‐scale fronts. The observations showed that the physical mechanism used to explain the interaction between the atmosphere and large‐scale ocean temperature gradients readily downscales to these smaller fronts, which have a direct impact of wind directly above the ocean surface. These small‐scale fronts were also observed to locally enhance the air‐sea heat flux, and the conventional model used to predict this underestimates the observed value by as much as 50%. These small‐scale frontal features are common across the global ocean, and our findings suggest that they could cumulatively impact the global energy budget. Key Points: Systematic ship‐based observations of wind and fluxes across submesoscale fronts were conducted in varying wind directionsCross‐frontal wind variance depended on the airflow relative to the in‐water thermal gradientSubmesoscale fronts were observed to locally enhance air‐sea heat flux, compared to values from commonly used bulk algorithm [ABSTRACT FROM AUTHOR]

Abstract: The Canadian Arctic Archipelago is a key conduit for comparatively fresh Arctic waters flowing to the Atlantic. Model estimates of the freshwater outflow, which is strongly correlated with the volume flux, contain major uncertainties because most existing models exclude tides, marginally resolve the internal Rossby radius, or both. At the same time, barotropic tidal models preclude stratified flow effects. Here we assess the relative importance of barotropic and baroclinic processes to water mass transformation, friction, and energy losses motivated by processes observed in a fine‐scale survey in the central Archipelago. A sharp separation of warmed Canada Basin water and locally formed water is observed over a long sill in a narrow channel and coincides with an internal hydraulic jump caused by the mean flow. Tidal currents, however, modulate the jump, as demonstrated by both scale analysis and a two‐dimensional simulation. The jump, together with internal tides propagating as Kelvin waves, leads to isopycnal displacements up to 50 m. The generation of these internal Kelvin waves has a leading‐order role in a regional energy budget. It is small, however, relative to bottom boundary layer dissipation, which accounts for an estimated 50% of the total tidal energy losses. Consequently, adding tides needs to be a priority for regional models. [ABSTRACT FROM AUTHOR]