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The balance between ocean mixing and stratification influences primary productivity through light limitation and nutrient supply in the euphotic ocean. Here, we apply a hierarchical clustering algorithm (Ward's method) to four factors relating to stratification (wind energy, freshwater index, water-column-averaged vertical eddy diffusivity, and halocline depth), as well as to depth-integrated phytoplankton biomass, extracted from a biophysical ocean model of the Salish Sea. Running the clustering algorithm on 4 years of model output, we identify distinct regions of the model domain that exhibit contrasting wind and freshwater input dynamics, as well as regions of varying water-column-averaged vertical eddy diffusivity and halocline depth regimes. The spatial regionalizations in physical variables are similar in all 4 analyzed years. We also find distinct interannually consistent biological zones. In the northern Strait of Georgia and Juan de Fuca Strait, a deeper winter halocline and episodic summer mixing coincide with higher summer diatom abundance, while in the Fraser River stratified central Strait of Georgia, shallower haloclines and stronger summer stratification coincide with summer flagellate abundance. Cluster-based model results and evaluation suggest that the Juan de Fuca Strait supports more biomass than previously thought. Our approach elucidates probable physical mechanisms controlling phytoplankton abundance and composition. It also demonstrates a simple, powerful technique for finding structure in large datasets and determining boundaries of biophysical provinces.

Wind-driven upwelling is an important control on surface nutrients and water properties in stratified lakes and seas. In this study, a high-resolution biophysical coupled model is used to investigate upwelling in the Strait of Georgia on the Canadian Pacific coast. The model is forced with surface winds from a high-resolution atmospheric forecast and has been tuned in previous studies to reproduce extensive observations of water level, temperature, salinity, nutrients and chlorophyll with competitive skill relative to similar models of the study region. A total of 5 years of hourly surface nitrate and temperature fields are analyzed in order to characterize the dominant upwelling patterns of the basin. A prevailing along-axis wind pattern steered by mountainous topography produces episodic upwelling along the western shore during the spring and fall southeasterlies and along the eastern shore during the summer northwesterlies, as indicated by positive nitrate anomalies. Principal component analysis reveals that these cross-axis upwelling patterns account for nearly one-third of the surface nitrate variance during the summer productive season. By contrast, nearly half of the surface temperature variance over the same period is dominated by a single, combined mixing and diurnal heating–cooling pattern. The principal components associated with these patterns correlate with along-axis wind stress in a manner consistent with these physical interpretations. The cross-axis upwelling response to wind is similar to other dynamically wide basins where the baroclinic Rossby deformation radius is smaller than the basin width. However, the nitrate anomaly during upwelling along the eastern shore is stronger in the northern basin, which may be indicative of an along-axis pycnocline tilt or an effect of the background along-axis stratification gradient due to the Fraser River. Our findings highlight an important spatiotemporal consideration for future ecosystem monitoring.

The response of a coastal ocean numerical model, typical of eastern boundaries, is investigated under upwelling-favorable wind forcing and with/without the presence of a submarine canyon. Experiments were run over three contrasting shelf depth/slope bathymetries and forced by an upwelling-favorable alongshore wind. Random noise in the wind stress field was used to trigger the onset of frontal instabilities, which formed around the upwelling front. Their development and evolution are enhanced over deeper (and less inclined) shelves. Experiments without a submarine canyon agree well with previous studies of upwelling frontal instabilities; baroclinic instabilities grow along the front in time. The addition of a submarine canyon incising the continental shelf dramatically changes the circulation and frontal characteristics. Intensified upwelling is channeled through the downstream side of the canyon in all depth/slope configurations. Farther downstream a downwelling area is generated, being larger and stronger on a shallow shelf. The canyon affects mainly the location of the southward upwelling jet, which is deflected inshore and accelerated after passing over the canyon. This process is accompanied by a break in the alongshore scale of the instabilities on either side of the canyon. Term balances of the depth-averaged cross-shore momentum equation reaffirm the downstream acceleration of the jet and the increased wavelength of the instabilities, and clarify the dominant balance between the advection and ageostrophic terms around the canyon.

Biogeochemical cycles in the Arctic Ocean are sensitive to the transport of materials from continental shelves into central basins by sea ice. However, it is difficult to assess the net effect of t...

Since the 1980–1990s, international research efforts have augmented our knowledge of the physical and chemical properties of the Arctic Ocean water masses, and recent studies have documented changes. Understanding the processes responsible for these changes is necessary to be able to forecast the local and global consequences of these property evolutions on climate. The present work investigates the distributions of geochemical tracers of particle fluxes and circulation in the Amerasian Basin and their temporal evolution over the last three decades (from stations visited between 1983 and 2015). Profiles of 230‐thorium (230Th) and 231‐protactinium (231Pa) concentrations and neodymium isotopes (expressed as εNd) measured in the Amerasian Basin prior to 2000 are compared to a new, post‐2000s data set. The comparison shows a large scale decrease in dissolved 230Th and 231Pa concentrations, suggesting intensification of scavenging by particle flux, especially in coastal areas. Higher productivity and sediment resuspension from the shelves appear responsible for the concentration decrease along the margins. In the basin interior, increased lateral exchanges with the boundary circulation also contribute to the decrease in concentration. This study illustrates how dissolved 230Th and 231Pa, with εNd support, can provide unique insights not only into changes in particle flux but also into the evolution of ocean circulation and mixing., Key Points Concentration decreases of 230Thd and 231Pad suggest an enhancement of particulate scavenging since the 2000s in the Amerasian BasinParticulate scavenging results from higher productivity and sediment resuspension from the shelvesPost‐2000s changes in intermediate and deep layers suggest enhanced lateral mixing between the margins and central areas of the basins

The balance between ocean mixing and stratification influences primary productivity through light limitation and nutrient supply in the euphotic ocean. Here, we apply a hierarchical clustering algorithm (Ward's method) to four factors relating to stratification and depth-integrated phytoplankton biomass extracted from a biophysical regional ocean model of the Salish Sea to assess spatial co-occurrence. Running the clustering algorithm on four years of model output, we identify distinct regions of the model domain that exhibit contrasting wind and freshwater input dynamics, as well as regions of varying watercolumn-averaged vertical eddy diffusivity and halocline depth regimes. The spatial regionalizations in physical variables are similar in all four analyzed years. We also find distinct interannually consistent biological zones. In the Northern Strait of Georgia and Juan de Fuca Strait, a deeper winter halocline and episodic summer mixing coincide with higher summer diatom abundance, while in the Fraser River stratified Central Strait of Georgia, shallower haloclines and stronger summer stratification coincide with summer flagellate abundance. Cluster based model results and evaluation suggest that the Juan de Fuca Strait supports more biomass than previously thought. Our approach elucidates probable physical mechanisms controlling phytoplankton abundance and composition. It also demonstrates a simple, powerful technique for finding structure in large datasets and determining boundaries of biophysical provinces.

This study addresses an important knowledge gap in the distribution of lead (Pb) in the Arctic Ocean, by presenting dissolved Pb concentrations from samples collected during the GEOTRACES Canadian cruise in 2015. Dissolved Pb showed an increase in concentration from the Canada Basin toward Baffin Bay and the Labrador Sea. Canada Basin was the most isolated region from anthropogenic Pb inputs with low background concentrations (1.4–6.2 pmol kg–1) across most of the basin, although higher Pb features from the advection of Pacific-derived waters and sea ice meltwater were present. Likewise, high-Pb peaks (13.5–26.6 pmol kg–1) along narrow isopycnal surfaces (σθ, 27.4–27.6) in Baffin Bay were attributed to the advection of North Atlantic waters spreading a high-Pb signature into the bay, contrasting with the low values (2.5–7.4 pmol kg–1) present in the mixed layer, Arctic and Baffin Bay deep waters. The Labrador Sea, largely influenced by the recirculation of North Atlantic waters, had the highest Pb concent...

Meaningful interpretation of archaeobotanical assemblages in the Near East often includes determination of whether dung fuel is the source of some or all of the recovered plant remains. In the years since Miller (Economy and Environment of Malyan, a Third Millennium B.C. Urban Center in Southern Iran. Ph.D. Dissertation, Department of Anthropology, University of Michigan, Ann Arbor, 1982; Paleorient 10:71–79, 1984) and Miller and Smart (J Ethnobiol 4:15–28, 1984) first identified archaeological plant remains from Malyan (Iran) as those of burned dung, subsequent archaeobotanical, experimental, and ethnographic research has been undertaken to test and expand her criteria for its recognition. A key criterion of Miller’s was a high ratio of weed seeds to wood charcoal (or a low ratio of charcoal to weed seeds). When used together with other quantitative measures based on standardizing ratios, this measure can help to illuminate variability in the sources of the recovered carbonized plant remains and some of the taphonomic processes that contributed to the resulting assemblage. Using the Late Early Halaf dataset from Fistikli Hoyuk, Turkey, as a case study, non-parametric statistical analysis was applied to eight such measures, including a new Fragmentation Index (FI), density measures (per litre of sediment) for charcoal, cereal grains, weed seeds, chaff, non-wood items, and cereal-type indeterminate non-wood items, and a relative density measure of charcoal to weed seeds. Each measure was calculated on the basis of 35 samples (n = 8,532). The results of this analysis indicate that these measures, when used in combination with Miller’s weed seed to charcoal ratio, implemented here as the relative density of charcoal to weed seeds, can reveal recovery context-related variations in formation processes that help to clarify both the role of dung fuel in assemblage formation and to differentiate the remains of cereal processing from those of burned fuel.

Although the ceramic phases and relative chronology of the Mycenaean (or “Late Helladic” abbr. LH) period on the Greek mainland are well established, there is ongoing disagreement regarding the relationship between the ceramic phases and their associated calendar dates. Part of the problem is the small number of radiocarbon dates from Mycenaean sites. In this article, we publish a set of 15 new AMS radiocarbon dates from the Mycenaean site of Iklaina, in southwestern Greece. The resulting date ranges allow us to establish an absolute chronology for major stages in the life of the Iklaina settlement and the associated relative chronology based on ceramic phases. In general, the Iklaina dates show a better fit with the High Chronology for the early Mycenaean period. Specifically, the transition from the Middle to Late Helladic, at the beginning of the Mycenaean period, is placed between the end of the 19th c. and the beginning of the 17th c. BC. The LH II period, when large-scale architecture appears at Iklaina for the first time, spans the 17th century BC and the LH IIIA1 period goes into the 15th century. None of the analyzed samples were recovered from secure LH IIIA2 deposits, so they do not affect the chronology of this period. However, the samples from the destruction of the monumental buildings, which ceramically is placed in the LH IIIB period, provide a general latest use date in the 13th century. Given the possibility that this destruction marks the annexation of Iklaina by the Palace of Nestor and the unification of the Pylian state, this becomes an important chronological marker for the formation of this state. It also indicates a very short life-span for this state, since its destruction is traditionally dated to ca. 1200 BCE.

Wind driven upwelling is an important control on surface nutrients and water properties in stratified lakes and seas. In this study, a high resolution biophysical coupled model is used to investigate upwelling in the Strait of Georgia. The model is forced with surface winds from a high resolution atmospheric forecast and reproduces extensive observations of water level, temperature, salinity, nutrients and chlorophyll with competitive skill relative to similar models of the study region. Five years of hourly surface nitrate and temperature are analyzed in order to characterize the dominant upwelling patterns of the basin. An along-axis wind climatology steered by mountainous topography produces episodic upwelling along the western shore during the spring and fall southeasterlies and along the eastern shore during the summer northwesterlies, as indicated by positive nitrate anomalies. Principal component analysis reveals that these cross-axis upwelling patterns account for nearly one-third of the surface nitrate variance during the productive season. By contrast, nearly half of the surface temperature variance over the same period is dominated by a single mixing-heating pattern. The principal components associated with these patterns correlate with wind stress in a manner consistent with these physical interpretations. The cross-axis upwelling response to wind is similar to other dynamically wide basins where the baroclinic Rossby deformation radius is smaller than the basin width. However, the nitrate anomaly during upwelling along the eastern shore is stronger in the northern basin, which may be indicative of an along-axis pycnocline tilt or an effect of the background along-axis stratification gradient due to the Fraser River. Our findings highlight an important spatio-temporal consideration for future ecosystem monitoring.

The intermediate circulation of the Strait of Georgia, British Columbia, Canada, plays a key role in dispersing contaminants throughout the Salish Sea, yet little is known about its dynamics. Here, we use hydrographic observations and hindcast fields from a regional 3D model to approach the intermediate circulation from three perspectives. Firstly, we derive and model a “seasonality” tracer from temperature observations to age the water, estimate mixing, and infer circulation. Secondly, we analyze modeled velocity fields to create mean current maps and examine the advective and diffusive components of the mean flow field. Lastly, we calculate Lagrangian trajectories to derive Transit Time Distributions and Lagrangian statistics. In combination, these analyses provide an overview of the mean intermediate circulation that can be summarized as follows: subducting water in Haro Strait ventilates the intermediate water primarily via an up-strait boundary current that flows along the eastern shores of the southernmost basin in 1–2 months. This inflowing water is either incorporated into the interior of the basin, recirculated southwards, or transported into the northernmost basin, mixing steadily with adjacent water masses during its transit. A second, shallower ventilating jet emanates southwards from Discovery Passage, locally modifying the Haro Strait inflow signal. Outside of these well-defined advective features, diffusive transport dominates in the majority of the region. The intermediate renewal signal fully ventilates the region in 100–140 days, which serves as a benchmark for contaminant dispersal timescale estimates.

We have developed a coupled physical-biological model representing plankton and nutrient dynamics of the Strait of Georgia, a fjord-like semi-enclosed coastal sea on the west coast of Canada. The nutrient-phytoplankton-zooplankton-detritus (NPZD)-type biological model is based on nitrogen uptake and remineralization with a coupled silicon cycle and includes both diatom and non-siliceous phytoplankton functional groups. The Strait of Georgia exhibits an estuarine circulation driven by input from the Fraser River as well as many smaller rivers and streams. It has high levels of dissolved silica (can be >50 μM even at the surface). Silicon-replete conditions shape key characteristics of the local ecosystem, which include heavily silicified glass sponge reefs as well as frequent diatom and occasional silicoflagellate blooms. We therefore consider the ability of the model to match observed silicon levels an indicator of the fidelity of its representation of local biogeochemistry. Silicon in the model may be in the form of dissolved silica, living diatoms, or particulate biogenic silica, and model diatom growth may be limited by nitrogen, light, or dissolved silica availability. We will discuss the challenges involved in accurately representing important drivers of the regional silicon cycle. These include accurately capturing the division of primary productivity between diatoms and non-siliceous phytoplankton functional groups, as well as uncertainties in the magnitude of terrestrial inputs and sediment fluxes. We will show how evaluating the model functional groups by comparison with phytoplankton community composition determined by high performance liquid chromatography (HPLC) has informed our interpretation of model results and provided direction for efforts at improving model performance. We will discuss the impact of targeted adjustments to model parameters on the model silicon cycle in light of comparisons to observations.

The rapidly changing conditions of the Arctic sea ice system have cascading impacts on the biogeochemical cycles of the ocean. Sea ice transports sediments, nutrients, trace metals, pollutants, and gases from the extensive continental shelves into the more isolated central basins. However, it is difficult to assess the net contribution of this supply mechanism on nutrients in the surface ocean. In this study, we used Manganese (Mn), a micronutrient and tracer which can integrate source fluctuations in space and time, to understand the net impact of the long range transport of sea ice for Mn.We developed a three-dimensional dissolved Mn model within a subdomain of the 1/12 degree Arctic and Northern Hemispheric Atlantic (ANHA12) configuration of NEMO centred on the Canadian Arctic Archipelago, and evaluated this model with in situ observations from the 2015 Canadian GEOTRACES cruises. The Mn model incorporates parameterizations for the contributions from river discharge, sediment resuspension, atmospheric deposition of aerosols directly to the ocean and via melt from sea ice, release of sediment from sea ice, and reversible scavenging, while the NEMO-TOP engine takes care of the advection and diffusion of the tracers. Simulations with this model from 2002 to 2019 indicate that the majority of external Mn contributed annually to the Canada Basin surface is released by sediment from sea ice, much of which originates from the Siberian shelves. Reduced sea ice longevity in the Siberian shelf regions has been postulated to result in the disruption of the long range transport of sea ice by the transpolar drift. This reduced sea ice supply has the potential to decrease the Canada Basin Mn surface maximum and downstream Mn supply, with implications for other nutrients (such as Fe) contained in ice-rafted sediments as well. These results demonstrate some of the many changes to the biogeochemical supply mechanisms expected in the near-future in the Arctic Ocean and the subpolar seas.

Coastal regions by their very nature are dynamically diverse. Within one geographical region there are often multiple areas dominated by substantially different dynamics that shape not only the physical characteristics but also the ecosystem. The Salish Sea, in the northeast Pacific, is an excellent example with strongly tidally mixed regions, freshwater-dominated regions, and regions directly influenced by the open ocean. These regions are generally well known and multiple disciplines refer to them with various boundaries and under various names. Here we use unsupervised clustering on numerical model results to formalize these regional provinces. The model is SalishSeaCast, a three-dimensional real-time coupled bio-chem-physical model based on the NEMO framework. We find that the regions clustered on ecosystem variables (phytoplankton biomass) spatially coincide with those clustered on physical variables, particularly the stratification as diagnosed by the halocline depth. The clusters are robust across years with interannual variability manifesting mostly in changes in the size of the clusters. As the clusters are dynamically distinct, they provide a natural framework on which to evaluate the model against observations. We find that the model accurately simulates each of the major clusters. The spatial and temporal resolution of the model can then characterize these different clusters more systematically than the observations, revealing biases associated with sparse sampling in the observations. Two examples will be given, one addressing a long-standing issue of the productivity gradient in the stratified main basin, the Strait of Georgia, and another concerning the seasonal cycle of productivity in the ocean-influenced Juan de Fuca Strait.

Coastal regions are typically characterized by considerable physical variability that in turn leads to dramatic variability in coastal carbonate chemistry. Recent shipboard and mooring-based observations have shown large spatial and temporal variations of carbonate chemistry parameters, including air-sea CO2 flux and aragonite saturation state, in one prominent coastal region in the Northeast Pacific Ocean - the Salish Sea. The range of the observed variability in the regional carbonate system is significantly larger than the global anthropogenic change, complicating the detection of secular carbon trends. Simultaneously, sparse observations limit understanding of the carbonate balance as a whole. Here, we use a highly resolved coastal model, SalishSeaCast, to characterize the drivers of the carbonate chemistry balance of the Salish Sea, with an emphasis on air-sea CO2 flux and aragonite saturation state. We then investigate the impact of a relatively modest increase in anthropogenic carbon in this region in the context of the governing physical and biological dynamics of the system. We examine the striking effects of the anthropogenic change to date on the inorganic carbon balance of the system, highlighting impacts on the aragonite saturation state of the system and its buffering capacity, as well as suggesting some bounds for the regional air-sea and lateral carbon fluxes. We then use the GLODAP dataset of global coastal carbon observations to consider our results in the context of other regions of the Pacific Rim and the global coastal ocean.

Submarine canyons enhance cross-shelf mass exchanges, which are a key component of on-shelf nutrient budgets and biogeochemical cycles. Previous studies assume that canyon-induced tracer flux onto ...

International audience; Global climate change has had large impacts on the Arctic region including rapid reductions in sea ice and rapid increases in surface air temperatures. Documenting the consequences of these changes in the Arctic Ocean is difficult, however, because accessibility limits observations in space and time and aliases measurements. This problem can be alleviated by using geochemical tracers, which can act as natural integrators, allowing us to determine net changes over regions and years. One such tracer is 230 Th. We use measurements and an off-line scavenging model forced by ANHA4, a regional configuration of the NEMO general circulation model, to investigate changes in the Canada Basin in the years 2002-2015. Observations show a clear decrease in 230 Th in intermediate layers, particularly in the internal Canada Basin. The model reproduces the observed changes in 230 Th concentration profiles. Using the model to determine the origin of the reduction shows that the decrease is due to both higher particle fluxes from increased productivity resulting from the reduction in sea ice cover and increased circulation and stirring by mesoscale eddies increasing lateral exchange between the productive coastal regions and less productive internal Canada Basin. The circulation model clearly shows increased velocities as the ice cover has decreased and storms have increased.

The southern Greek archaeological site of Franchthi Cave, with occupation dating from the Upper Paleolithic, remains the only site in southern Greece that both spans the shift from foraging to farming and has produced systematically recovered plant remains associated with this important transition in human prehistory. Previously reported archaeobotanical remains from the site derive exclusively from the cave interior, as none were recovered from outside the cave on the Franchthi Cave Paralia. This article reports the first evidence for plant use in the settlement area outside the cave, as provided by five seed impressions in Early Neolithic ceramic sherds from the Paralia. Significantly, this new data expands the range of crops represented at the site during the Early Neolithic to include einkorn wheat (Triticum monococcum L.), pushing back its appearance at Franchthi by several centuries.

Ocean acidification threatens to reduce pH and aragonite saturation state (ΩA) in estuaries, potentially damaging their ecosystems. However, the impact of highly variable river total alkalinity (TA) and dissolved inorganic carbon (DIC) on pH and ΩA in these estuaries is unknown. We assess the sensitivity of estuarine surface pH and ΩA to river TA and DIC using a coupled biogeochemical model of the Strait of Georgia on the Canadian Pacific coast and place the results in the context of global rivers. The productive Strait of Georgia estuary has a large, seasonally variable freshwater input from the glacially fed, undammed Fraser River. Analyzing TA observations from this river plume and pH from the river mouth, we find that the Fraser is moderately alkaline (TA 500–1000 µmol kg−1) but relatively DIC-rich. Model results show that estuarine pH and ΩA are sensitive to freshwater DIC and TA, but do not vary in synchrony except at high DIC : TA. The asynchrony occurs because increased freshwater TA is associated with increased DIC, which contributes to an increased estuarine DIC : TA and reduces pH, while the resulting higher carbonate ion concentration causes an increase in estuarine ΩA. When freshwater DIC : TA increases (beyond ∼ 1.1), the shifting chemistry causes a paucity of the carbonate ion that overwhelms the simple dilution/enhancement effect. At this high DIC : TA ratio, estuarine sensitivity to river chemistry increases overall. Furthermore, this increased sensitivity extends to reduced flow regimes that are expected in future. Modulating these negative impacts is the seasonal productivity in the estuary which draws down DIC and reduces the sensitivity of estuarine pH to increasing DIC during the summer season.

This study investigates the sensitivity of a high resolution regional ocean model to several choices in mixing and advection. The oceanographic process examined is a deep water renewal event in the Juan de Fuca Strait–Strait of Georgia sill-basin estuarine system located on the west coast of North America. Previous observational work has shown that the timing of the renewal events is linked to the spring/neap tidal cycle, and in turn, is sensitive to the amount of vertical mixing induced by tidal currents interacting with sills and complicated bathymetry. It is found that the model’s representation of deep water renewal is relatively insensitive to several mixing choices, including the vertical turbulence closure and direction of lateral mixing. No significant difference in deep or intermediate salinity was found between cases that used k − ϵ versus k − ω closures and isoneutral versus horizontal lateral mixing. Modifications that had a stronger effect included those that involved advection such as modifying the salinity of the open boundary conditions which supply the source waters for the renewal event. The strongest impact came from the removal of the Hollingsworth instability, a kinetic energy sink in the energy-enstrophy discretization of the momentum equations. A marked improvement to the salinity of the deep water renewal suggests that the removal of the Hollingsworth instability will correct a fresh drift in the deep and intermediate waters in an operational version of this model.

The ocean knows no political borders. Ocean processes, like summertime wind-driven upwelling, stretch thousands of kilometers along the Northeast Pacific (NEP) coast. This upwelling drives marine ecosystem productivity and is modulated by weather systems and seasonal to interdecadal ocean-atmosphere variability. Major ocean currents in the NEP transport water properties such as heat, fresh water, nutrients, dissolved oxygen, pCO2, and pH close to the shore. The eastward North Pacific Current bifurcates offshore in the NEP, delivering open-ocean signals south into the California Current and north into the Gulf of Alaska. There is a large and growing number of NEP ocean observing elements operated by government agencies, Native American Tribes, First Nations groups, not-for-profit organizations, and private entities. Observing elements include moored and mobile platforms, shipboard repeat cruises, as well as land-based and estuarine stations. A wide range of multidisciplinary ocean sensors are deployed to track, for example, upwelling, downwelling, ocean productivity, harmful algal blooms, ocean acidification and hypoxia, seismic activity and tsunami wave propagation. Data delivery to shore and observatory controls are done through satellite and cell phone communication, and via seafloor cables. Remote sensing from satellites and land-based coastal radar provide broader spatial coverage, while numerical circulation and biogeochemical modeling complement ocean observing efforts. Models span from the deep ocean into the inland Salish Sea and estuaries. NEP ocean observing systems are used to understand regional processes and, together with numerical models, provide ocean forecasts. By sharing data, experiences and lessons learned, the regional ocean observatory is better than the sum of its parts.

Sedimentary 231Pa/230Th ratios have been used in the Atlantic Ocean as a proxy to reconstruct past changes in the strength and geometry of the Atlantic Meridional Overturning Circulation (AMOC), stemming from the southward export of 231Pa by the North Atlantic Deep Water (NADW). However, deep waters in the Pacific Ocean have a longer residence time, so that Pacific sedimentary 231Pa/230Th ratios are more strongly affected by particle/boundary scavenging, which obscures the influence of deep water circulation. The goal of this study is to examine how the Pacific Meridional Overturning Circulation (PMOC) affects the distribution of 231Pa and 230Th in the water column and sediment of the Pacific Ocean, and to explore whether sedimentary 231Pa/230Th ratios could provide useful constraints on past changes of the deep Pacific circulation. We examine the existing Pacific sedimentary 231Pa/230Th database and demonstrate that the Pacific Meridional Overturning Circulation (PMOC) has a distinctive influence on the distribution of sedimentary 231Pa/230Th. Using a 2D scavenging model with a simplified representation of the Pacific deep water circulation, we show that Pacific sedimentary 231Pa/230Th could potentially provide information on past variability in PMOC.

The Strait of Georgia (SoG) is a large semienclosed estuary that spatially dominates the Salish Sea on the North American Pacific coast. The region is well populated, harbors significant aquaculture, and is vulnerable to climate change. We present the first inorganic carbon data collected in the SoG covering all seasons (2003 and 2010–2012) and put them into the context of local circulation and oxygen cycles. Results show that the SoG has a higher carbon content and lower pH than surrounding waters. Aragonite saturation horizons in the SoG do not become deeper than 20–30 m and shoal to the surface for extended periods. Furthermore, incoming upwelled “acidified” water from the outer coast actually increases local pH. Finally, intense mixing in the physically restricted channels connecting the SoG to the outer coast allows significant oxygen uptake but minimal CO2 out gassing, protecting the SoG from hypoxia but not from ocean acidification.

Declines in mean ocean pH and aragonite saturation state (ΩA) driven by anthropogenic CO2 emissions have raised concerns regarding the trends of pH and ΩA in estuaries. Low pH and ΩA can be harmful to a variety of marine organisms, especially those with calcium carbonate shells, and so may threaten the productive ecosystems and commercial fisheries found in many estuarine environments. The Strait of Georgia is a large, temperate, productive estuarine system with numerous wild and aquaculture shellfish and finfish populations. We determine the seasonality and variability of near-surface pH and ΩA in the Strait using a one-dimensional, biophysical, mixing layer model. We further evaluate the sensitivity of these quantities to local wind, freshwater, and cloud forcing by running the model over a wide range of scenarios using 12 years of observations. Near-surface pH and ΩA demonstrate strong seasonal cycles characterized by low pH, aragonite-undersaturated waters in winter and high pH, aragonite-supersaturated waters in summer. The aragonite saturation horizon generally lies at ∼20 m depth except in winter and during strong Fraser River freshets when it shoals to the surface. Periods of strong interannual variability in pH and aragonite saturation horizon depth arise in spring and summer. We determine that at different times of year, each of wind speed, freshwater flux, and cloud fraction are the dominant drivers of this variability. These results establish the mechanisms behind the emerging observations of highly variable near-surface carbonate chemistry in the Strait.

Cross shelf-break exchange is limited by the tendency of geostrophic flow to follow bathymetric contours, not cross them. However, small scale topography, such as canyons, can reduce the local lengthscale of the flow and increase the local Rossby number. These higher Rossby numbers mean the flow is no longer purely geostrophic and significant cross-isobath flow can occur. This cross-isobath flow includes both upwelling and downwelling due to wind-driven shelf currents and the strong cascading flows of dense shelf-water into the ocean. Tidal currents usually run primarily parallel to the shelf-break topography. Canyons cut across these flows and thus are often regions of generation of strong baroclinic tides and internal waves. Canyons can also focus internal waves. Both processes lead to greatly elevated levels of mixing. Thus, through both advection and mixing processes, canyons can enhance Deep Ocean Shelf Exchange. Here we review the state of the science describing the dynamics of the flows and suggest further areas of research, particularly into quantifying fluxes of nutrients and carbon as well as heat and salt through canyons.

The exchanges of water, nutrients and oxygen between the coastal and open ocean are key components of on-shelf nutrient budgets and biogeochemical cycles. On a regional scale, submarine canyons enhance physical processes such as shelf-slope mass exchange and mixing. There is good understanding of the flow around upwelling submarine canyons; however, the flux of biologically relevant tracers is less understood. This work investigates the impact of submarine canyons on the cross-shelf exchange of tracers and water, taking into account the impact of locally-enhanced mixing within the canyon, and develops a scaling estimate for canyon-induced upwelling of tracers, proportional to local concentration, vertical diffusivity, and previously scaled upwelling flux. For that purpose, we performed numerical experiments simulating an upwelling event near an idealized canyon, adding a passive tracer with an initially linear profile. We varied the geographic distribution of vertical eddy diffusivity and its magnitude, the initial stratification, Coriolis parameter, and the strength of the incoming flow. We find that a canyon, of width 5% of the length of the shelf, upwells between 25 to 89% more tracer mass onto the shelf than coastal upwelling. Locally-enhanced vertical diffusivity has a positive effect on the tracer that is advected by the upwelling flow and can increase canyon-upwelled tracer flux by up to 27%., Accepted for publication in the Journal of Physical Oceanography

Flow dynamics around a downwelling submarine canyon were analysed with the Massachusetts Institute of Technology general circulation model. Blanes Canyon (northwestern Mediterranean) was used for topographic and initial forcing conditions. Fourteen scenarios were modelled with varying forcing conditions. Rossby and Burger numbers were used to determine the significance of Coriolis acceleration and stratification (respectively) and their impacts on flow dynamics. A new non-dimensional parameter (χ) was introduced to determine the significance of vertical variations in stratification. Some simulations do see brief periods of upwards displacement of water during the 10-day model period; however, the presence of the submarine canyon is found to enhance downwards advection of density in all model scenarios. High Burger numbers lead to negative vorticity and a trapped anticyclonic eddy within the canyon, as well as an increased density anomaly. Low Burger numbers lead to positive vorticity, cyclonic circulation, and weaker density anomalies. Vertical variations in stratification affect zonal jet placement. Under the same forcing conditions, the zonal jet is pushed offshore in more uniformly stratified domains. The offshore jet location generates upwards density advection away from the canyon, while onshore jets generate downwards density advection everywhere within the model domain. Increasing Rossby values across the canyon axis, as well as decreasing Burger values, increase negative vertical flux at shelf break depth (150 m). Increasing Rossby numbers lead to stronger downwards advection of a passive tracer (nitrate), as well as stronger vorticity within the canyon. Results from previous studies are explained within this new dynamic framework.

The Strait of Georgia is a large, semi-enclosed body of water between Vancouver Island and the mainland of British Columbia connected to the Pacific Ocean via Juan de Fuca Strait at the south and Johnstone Strait at the north. During the winter months, coastal communities along the Strait of Georgia are at risk of flooding caused by storm surges, a natural hazard that can occur when a strong storm coincides with high tide. This investigation produces storm surge hindcasts using a three-dimensional numerical ocean model for the Strait of Georgia and the surrounding bodies of water (Juan de Fuca Strait, Puget Sound, and Johnstone Strait) collectively known as the Salish Sea. The numerical model employs the Nucleus for European Modelling of the Ocean architecture in a regional configuration. The model is evaluated through comparisons of tidal elevation harmonics and storm surge with observations. Important forcing factors contributing to storm surges are assessed. It is shown that surges entering the...

A coupled biophysical model is used to explore the physical controls involved in the timing of the spring phytoplankton bloom in fjords. Observations from Rivers Inlet, British Columbia, are used to force and evaluate the model. It is found that the interannual variation in timing is due primarily to variations in retention, in particular, to variations in horizontal advection out of the fjord. The two dominant processes are (i) strong outflow winds rapidly advecting the surface layer and thus the phytoplankton population out of the fjord and (ii) losses due to high river flux increasing the estuarine circulation. Both processes delay the timing of spring bloom. Smaller effects on the interannual variation are due to increased wind mixing which deepens the mixing layer and reduces light to phytoplankton, and increased river flow which increases the stratification and decreases the mixing layer depth. Observed interannual variations in cloudiness were small. Strong outflow winds are common in winter along the British Columbia coast, but generally cease after the spring wind transition. Thus, observed interdecadal variations in the spring transition date probably imply strong variations in the timing of spring phytoplankton blooms in British Columbia fjords.

The Strait of Georgia (SoG), between Vancouver Island and mainland British Columbia, is a larval rearing ground for both hake and herring stocks, which are commercially important. Year-to-year variability in larval retention within the strait is examined by simulating drift tracks of larvae for these species using an ocean circulation model and a particle-tracking model. Larvae with different vertical swimming behaviors were tracked in the springs of 2007, 2008, and 2009. Since herring larvae mostly stay near the surface, their distribution is heavily influenced by the wind. Strong winds to the north soon after the hatching period tend to wash herring larvae out of SoG and winds to the south help retain herring larvae inside the Strait. In 2007, the model indicates a massive wind-driven export of herring larvae which may have led to the observed failure of herring production. In contrast, hake larvae reside deeper in the water column (50–200 m). Their distribution is less sensitive to surface forcing but is shaped by a deep gyre with cross-strait currents. This study also suggests that the northern and southern SoG are weakly connected for herring larvae dispersal, which makes both regions potentially important to recruitment.

Zooplankton vertical distribution data and velocity estimates from a hydrodynamicmodel were employed to determine zooplankton daily exchange during four cruisesconducted from March to June 2010 in Rivers Inlet, a fjord in central BritishColumbia, Canada. Zooplankton transport rates varied temporally, being fastest inMarch when water velocities were highest. The active vertical movement of thezooplankton interacted with the vertically sheared flow field to influence zooplanktonadvection. Surface dwelling plankton such as Acartia longiremis and larvaceans experi-enced the highest advection losses of 20.4 and 20.5 day

Current observations in submarine canyons poleward of 30° are usually dominated by the semidiurnal (M2) tidal frequency, which is superinertial at these latitudes. Observations from a submarine canyon at 44°N (the Gully, Nova Scotia) suggest that canyons can be dominated by the subinertial (K1) tidal frequency if length scales are correct for resonance of the K1 frequency. A model of the Gully was constructed in a tank on a rotating table and tidal currents generated to determine factors that influence resonance. Resonance curves were fit to measurements from the laboratory canyon for a range of stratifications, background rotation rates, and forcing amplitudes. Dense water was observed upwelling onto the continental shelf on either side of the laboratory canyon and traveled at least one canyon width along the shelf. Friction values measured in the laboratory were much higher than expected, probably due to upwelled water surging onto the shelf on each tidal cycle, similar to a tidal bore. By scaling observations from the laboratory to the ocean and assuming friction in the ocean is also affected by water traveling onto the shelf, a resonance curve for the ocean was created. Because of the broad resonance curve, the diurnal tide remains strong year round at the Gully, even as stratification at the shelf break changes. Dense water surging onto the shelf on tidal frequencies may affect friction and mixing at other nonresonant canyons.

Gjipali Ilir, Allen Susan E. Gërmimi në vendbanimin e neolitit të hershëm të Vashtëmisë. In: Iliria, vol. 38, 2014. pp. 173-179.

[1] Submarine canyons that cut into the continental shelf are regions of enhanced upwelling. The depth of upwelling and flux through the canyons determines their role in exchange between the shelf and the open ocean. Scaling analyses that relate these quantities to the strength of the flow, stratification, Coriolis parameter, and topographic shape parameters allow their estimation in the absence of a full numerical simulation or a detailed field study. Here we add the effect of the continental shelf slope to the scaling of the depth of upwelling, upwelling flux, and deep water stretching. The scaling is then tested using a three-dimensional primitive equation model over 18 distinct geometries. The impact of the continental shelf is significant for real canyons with changes in the depth of upwelling of up to 11% and of the flux of upwelling of up to 70%. The numerical simulations clearly show three types of canyon upwelling, a symmetric time-dependent flux, the dominant advection-driven flux, and a new flux that appears to be related to internal waves. They also suggest that the canyon width is more important than the upstream canyon shape in determining the strength of the flow across the canyon.

Using a one-dimensional coupled bio-physical model, the spring phytoplankton bloom in the Strait of Georgia was hindcast for years 1968 to 2010. Relative to the long term mean (March 25), the timing of the bloom was later in the early 1970s (about April 2), earlier in the early 1990s (about March 18) and later again in recent years (about March 30). These long term shifts are related to shifts in the intensity of winter storms and cloudiness. A more dramatic shift is seen in the interannual variation in timing with the standard deviation over seven consecutive years doubling during the timeseries. Since the early 1990s there have been a few, very early blooms leading to a large interannual spread in bloom times. We show that this change is related to warming and therefore we project that this level of variation may continue under climate change.

Allen Susan E., Gjipali Ilir. Zbulime të reja për Neolitin e hershëm në Shqipëri: Projekt arkeologjik për Neolitin në Shqipërinë jugore. (sanap), 2006-2013. In: Iliria, vol. 37, 2013. pp. 37-53.