Large-amplitude, nonlinear internal waves are rarely considered in operational navigation, yet they can generate strong and rapidly varying currents in stratified coastal environments. This study investigates their potential impact on ship manoeuvrability near the Grande-Anse Terminal in the Saguenay Fjord (QC, Canada), motivated by a 2019 docking incident involving a cargo vessel under otherwise calm conditions. Field measurements were collected during fall 2023 and summer 2024 using ADCPs, CTDs, an echosounder, shore-based imaging, and a drone. The measurements reveal the frequent occurrence of large-amplitude internal wavetrains, observed almost daily and phase-locked with the semi-diurnal tidal cycle. These waves propagate across the fjord and interact with the wharf, generating rapid current fluctuations on time scales of one to two minutes. Wave amplitudes of up to 10 m and associated horizontal current variations approaching 1 m/s were measured, significantly larger than previously reported in this region. Such conditions can substantially alter the local flow field and potentially affect ship manoeuvrability during critical operations such as docking. These results demonstrate that internal waves constitute a previously underappreciated source of current variability in stratified coastal environments and highlight the need to account for their effects in pilot training, navigation guidance, and ship-handling simulators.

As part of the new Fisheries Act, Fisheries and Oceans Canada (DFO) has made it a priority to disseminate its data publicly. The project proposed here is to create an open-access data product that includes most of the historical temperature and salinity profiles collected in Northwest Atlantic Ocean and its Arctic gateways. This project does not aim to replace a potential database, but rather provides an easily accessible and quality-controlled product that can inform fisheries management and support DFO priorities such as the Ecosystem Approach to Fisheries Management, Marine Spatial Planning and the Blue Economy. The Canadian Atlantic Shelf Temperature-Salinity (CASTS) data product consists of 853 748 individual casts (as of 22 August 2025) collected in a geographical zone corresponding to [35-80 degrees N] and [42-100 degrees W] since 1873. The data sources used to make this product were gathered from multiple sources, including DFO regional archives at the Maurice-Lamontagne Institute (MLI), the Bedford Institute of Oceanography (BIO), and the Northwest Atlantic Fisheries Center (NAFC). Other sources of data include the Fisheries and Marine Institute of Memorial University, data from international ships of opportunity archived by the Marine Environmental Data Services (MEDS), and the Polar Data Catalog. This data product also offers new opportunities to review the changes in the ocean climate of Atlantic Canada, another priority of the Government of Canada. The analysis of these data collected over more than a century also reveals the profound changes undergone by the Northwest (NW) Atlantic Ocean during that period. Climate highlights include large decadal fluctuations of temperature and salinity throughout the entire zone, as well as sustained warming trends on the Scotian Shelf and the Bay of Fundy since the early 1990s, coinciding with an important freshening on the Newfoundland and Labrador Shelf during the same period. The CASTS data product is available at 10.20383/103.01462 .

In 2019, the Motor Vessel Jaeger Arrow collided with the Grande-Anse Terminal wharf (Saguenay Fjord, Canada) during docking from unknown causes. However, the timeline of the incident and the ship’s behavior during docking suggest that underwater waves may have caused the collision. Data collected in 2023 using a camera and thermometers confirmed that this area of the fjord regularly experiences underwater waves with wavelengths ranging from 50 to $$100~\textrm{m}$$ , wave heights of 1 and $$3~\textrm{m}$$ , and periods of around $$2~\textrm{min}$$ . These waves frequently collide with and reflect off the wharf, generating currents of 0.1 to $$0.3~\textrm{m}\,\textrm{s}^{-1}$$ . Numerical simulations further illustrate the interactions between the waves and the wharf, highlighting regions near the wharf where wave-induced currents, both inshore and offshore, occur, including areas with near-zero currents that could create a false sense of calm conditions. Importantly, our observations also revealed that large ships, such as the Jaeger Arrow, can generate their own underwater waves, potentially compromising docking operations. While we cannot definitively confirm that underwater waves caused the incident involving the Jaeger Arrow, our study offers a plausible explanation: the ship may have been caught in a wavetrain reflecting off the wharf, leading to unpredictable movement during docking. These results highlight the potential risks posed by underwater waves to ship safety and maneuverability during docking operations, a topic under-explored in existing scientific literature.

This research is motivated by an incident in the Saguenay Fjord (QC, Canada) that occured in 2019, where a cargo ship collided with a wharf while docking, resulting in minor material damage to both the vessel and the wharf under circumstances that remain unknown. Our hypothesis is that internal solitary waves may have contributed to the ship's unexpected drift. To test this hypothesis, CTDs, ADCPs and an echosounder were deployed during the summer of 2024. The measurements collected revealed the presence of internal waves over a two-week period. These observations show that trains of internal waves impacted the wharf daily and that they appear to be phase-locked with the tidal cycle. Internal waves of a wavelength of 60 m and a period of 40 s were recorded with amplitudes reaching 10 m and wave-induced horizontal currents of 1m.s-1. These currents are potentially strong enough to affect the maneuverability of a cargo ship during docking. The results of this research could contribute to the improvement of navigation simulators, adding the ability to account for the effects of internal waves on docking maneuvers.

A recent study suggests that the sky of van Gogh's The Starry Night accurately depicts the intrinsic and complex structure of real, fully developed turbulent flows. This conclusion was reached by comparing the slope of the power spectral density of the image to Kolmogorov's famous -5/3 law of turbulence. In this essay, we show that this correspondence is coincidental and anecdotal and argue that examining the spectral slope alone is not sufficient to state whether or not a painting, or any other type of image, accurately reflects Kolmogorov-like turbulence. Otherwise, we would be forced to conclude that Degas' A Woman Seated beside a Vase of Flowers also accurately depicts turbulence.

Brightness temperature is operationally used to retrieve sea surface salinity (TB-SSS) over the global ocean, but is contaminated by land and sea ice in close proximity. Ocean color can be used to retrieve SSS (OC-SSS) via the relation between color and salinity, but this relation is only valid over the coastal ocean with terrestrial influence. Important ecological areas exist where both spectral domains can provide SSS estimates. Here we compare these estimates over the St. Lawrence Estuary and Gulf in Eastern Canada, where a large collection of near-surface in situ salinity measurements is available. While TB-SSS faces a significant limitation in undersampling spatial variability, OC-SSS is predominantly hindered by cloud cover. Offshore, TB-SSS data are considerably more abundant than OC-SSS data, the latter of which are available only about 30% as often as the former. However, OC-SSS estimates extend into more nearshore areas, such as the St. Lawrence Estuary. Additionally, OC-SSS estimates are more accurate, with a root mean square difference of 0.46 g kg−1 compared to 0.79 g kg−1 for TB-SSS. We employed each of these satellite-derived SSS products to compare the pronounced freshwater pulse of 2017 and post-tropical storm Dorian of fall 2019, finding that short-lived events were better captured by the OC-SSS product. In contrast, the TB-SSS product offered more extensive temporal coverage but smoothed out such events. Our analyses underscore the need for higher-resolution satellite salinity-sensors in coastal studies. In the meantime, ocean color data resolves submesoscale features and can help enhance our understanding of these dynamic environments.

The Gulf of St. Lawrence has been nearly free of sea ice five times in its recorded history, three of which have occurred since 2010. This study examines the inter-annual variability of sea ice cover characteristics (1969-2023) and winter mixed layer heat content (1996-2023), their sensitivity to fall oceanic conditions (since fall of 1995) and to winter air temperatures. The study finds no relationship between the first occurrence of sea ice, maximum seasonal volume or winter mixed layer heat content and fall oceanic conditions as determined by the heat content of the water column in early fall. However, it shows that the first occurrence of sea ice in the northwestern Gulf is related to the timing of sea surface temperature crossing the 0C threshold with a lag time of about 3 weeks, and with air temperature dropping below -1.8C with a lag of roughly 40 days. The average air temperature over the Gulf between December and February or March is highly correlated to seasonal maximum sea ice area and volume, as well as ice season duration. This is likely through a link with sensible heat flux. The five nearly ice-free winters correspond to the warmest December to February (or December to March) average air temperatures over the Gulf. From this is inferred that a warming of 2.2 to 2.4C above the 1991-2020 climatology leads to nearly ice-free conditions in the Gulf of St. Lawrence. This finding is consistent with numerical simulation studies.

Open data that can be easily incorporated into analyses are essential for developing ecosystem approaches to marine ecological management: a common goal in fisheries policy in many countries. Although it is not always clear what constitutes an ecosystem approach, it always involves scientists working with a large variety of data and information, including data from physical and oceanographic sampling, multispecies surveys, and other sources describing human pressures. This can be problematic for analysts because these data, even when available, are often held in disparate datasets that do not necessarily correspond at appropriate temporal and spatial scales. Data can often only be obtained by specific requests to individuals in governmental agencies who are delivering on an increasing number of data requests as interest grows in practical ecosystem approach implementation. This data access model is not sustainable and hinders the momentum for ecosystem approach development. We describe a data bundling R package that makes data and climate projections available at appropriate scales to facilitate development of an ecosystem approach for the Gulf of St. Lawrence, Canada. This approach integrates closely with the present workflow of most government analysts, academics in fisheries, and scientists in private industry. The approach conforms with open data initiatives and makes data easily available globally while relieving some of the burden of data provision that can fall to some individuals in government laboratories. The structure and approach are generic, adaptable, and transferable to other regions and jurisdictions.

The Strait of Belle Isle (SBI) is an important pathway for water mass exchanges between the Labrador Shelf and the Gulf of St. Lawrence (GSL), particularly for transport toward the GSL. Seasonal and inter-annual variability of transport in the SBI are examined using 15 years of moored acoustic Doppler current profiler data. Tidal currents are largely along strait and homogeneous with depth. Transports are toward the GSL on average, lowest (-1.0 & plusmn; 0.8 dSv) from April to July, and highest (-4.0 & plusmn;1.1 dSv) from September to January. Averaged seasonal transports are usually within one standard deviation of previously published modeled values. The volume of winter Labrador Shelf water (LShW) entering the GSL is computed by transport integration and compares well with integrated volumes that meet LShW temperature-salinity criteria during an annual March survey of the GSL. Integrating over the whole year showed that on average 649 & plusmn; 397 km(3) enters the GSL after the March surveys are conducted, independently of the volume that has entered up to March; this addition represents on average about a third of the total volume. Annual volumes of LShW calculated from transport suggest that flow through the SBI accounts for 12%-18% of the GSL winter surface mixed layer. Cross-strait current shear may affect transport integration values, but sea surface temperature data suggests this bias is limited to the summer. Corrections are empirically derived to account for cross-strait shear in our transport calculation. The corrected time series suggests that the average transport may be flowing toward the Labrador Shelf in July (0.6 & plusmn; 1.0 CI [0.1 1.1] dSv).

The Atlantic Zone Monitoring Program (AZMP) was established by Fisheries and Oceans Canada (DFO) in 1998 with the aim of monitoring physical and biological ocean conditions in Atlantic Canada in support of fisheries management. Since 2014, at least two of the carbonate parameters (pH; total alkalinity, TA; and dissolved inorganic carbon, DIC) have also been systematically measured as part of the AZMP, enabling the calculation of derived parameters (e.g., carbonate saturation states, Ω, and partial pressure of CO2, pCO2). The present study gives an overview of the spatiotemporal variability in these parameters between 2014 and 2022. Results show that the variability in the carbonate system reflects changes in both physical (e.g., temperature and salinity) and biological (e.g., plankton photosynthesis and respiration) parameters. For example, most of the region undergoes a seasonal warming and freshening. While the former will tend to increase Ω, the latter will decrease both TA and Ω. Spring and summer plankton blooms decrease DIC near the surface and then remineralize and increase DIC at depth in the fall. The lowest pCO2 values (down to ∼ 200 µatm) are located in the cold coastal Labrador Current, whereas the highest values (>1500 µatm) are found in the fresh waters of the Gulf of St. Lawrence and the St. Lawrence Estuary. The latter is also host to the lowest pH values of the zone (7.48 in the fall of 2022). Finally, most of the bottom waters of the Gulf of St. Lawrence (>90 %) are undersaturated with respect to aragonite (Ωarg<1). In addition to providing a baseline of carbonate parameters for the Atlantic Zone as a whole, this comprehensive overview is a necessary and useful contribution for the modelling community and for more in-depth studies. The full dataset of measured and derived parameters is available from the Federated Research Data Repository: https://doi.org/10.20383/102.0673 (Cyr et al., 2022a).

Abstract. The Atlantic Zone Monitoring Program (AZMP) was established by Fisheries and Oceans Canada (DFO) in 1998 with the aim of monitoring physical and biological ocean conditions in Atlantic Canada in support of fisheries management. Since 2014, at least two of the carbonate parameters (pH, Total Alkalinity - TA, Dissolved Inorganic Carbon - DIC) have also been systematically measured as part of the AZMP, enabling the calculation of derived parameters (e.g., carbonate saturation states - Ω, partial pressure of CO2 - pCO2, etc.). The present study gives an overview of the spatiotemporal variability of these parameters between 2014 and 2020. Results show that the variability of carbonate parameters reflects changes in both physical (e.g., temperature, salinity) and biological (e.g., plankton photosynthesis and respiration) parameters. For example, most of the region undergoes a seasonal warming and freshening. While the former will tend to increase Ω, the latter will decrease both TA and Ω. Spring and summer plankton blooms decrease DIC near the surface and then remineralize and increase DIC at depth in the fall. The lowest pCO2 values are located in the cold Coastal Labrador Current and the highest in the fresh waters of the Gulf of St. Lawrence and the St. Lawrence Estuary. The latter is also the host of the lowest pH values of the zone. Finally, most of the bottom waters of the Gulf of St. Lawrence are undersaturated with respect to aragonite (Ωarg<1). In addition to providing a baseline of carbonate parameters of the Atlantic Zone as a whole, this comprehensive overview is a necessary and useful contribution for the modeling community and for more in-depth studies. The full data set of measured and derived parameters is available in the Federated Research Data Repository at https://doi.org/10.20383/102.0673.

Bivalve growth is affected by phytoplankton quality and availability, but long-term, coastal environmental time series related to these parameters are often lacking. Therefore, it is crucial to develop methods to accurately quantify trends in phytoplankton dynamics over time. This would be especially important for the fished scallop beds in the northern Gulf of St. Lawrence, where landings sharply declined since the early-2000s. Over the past decade, many studies have highlighted the potential of Ba/Ca ratios in bivalve shells as an environmental proxy for phytoplankton dynamics. This study presents records of Ba/Ca ratios in 31 young Chlamys islandica shells sampled in the Mingan Archipelago from 1979 to 2018. The Ba/Ca master chronology showed a decreasing trend since 2002, which could reflect changes in local phytoplankton bloom taxonomic composition, and coincides with the aforementioned decline in scallop landings. Investigations of environmental controls on barium incorporation into the shells highlight the importance of bottom, nutrient-rich waters to support diatom production or export in this fishing area. The use of such high-resolution seasonal records extracted from bio-archives may identify essential environmental mechanisms that will then assist with the development of an ecosystem-based fishery management strategy.

We report the first water-column dissolved methane data set from the Estuary and Gulf of St. Lawrence (EGSL). Per surface-water methane concentration and sea-to-air flux, the upper estuary behaved like a typical shallow macrotidal estuary, while the lower estuary and the gulf resembled outer shelf seas and ocean slopes, respectively. The EGSL emitted 166.3 (71.5-214.4) x 10(6) mol CH4 year(-1) to the atmosphere, representing 0.3% (0.1%-0.4%) of the total emission from global estuarine environments. A net production of 11.7 x 10(7) mol CH4 year(-1) was required to sustain this emission. Methane distributions in the upper estuary were dominated by physical mixing, while those in the lower estuary and the gulf bore characteristic subsurface maxima and deep minima shedding light on the methane consumption and production pathways. Elevated but highly variable near-bottom methane concentrations (10.4-695.3 nmol L-1) transpired over pockmarks on the seabed of the lower estuary, inferring an upward diffusive flux of up to similar to 700 mmol CH4 m(2) d(-1). Hypoxia in the lower estuary bottom water had little influence on methane concentrations. Lab incubations yielded methane cycling rates from a net production of 0.0068 nmol L-1 d(-1) to net consumption with turnover times of 33.3-263 days. Methane in the EGSL was isotopically enriched with C-13 (delta C-13(CH4): -40.9 parts per thousand to -27.4 parts per thousand relative to Peedee Belemnite). This study reveals that the EGSL is a smaller proportional contributor to methane emission from estuarine environments and that complex physical-biogeochemical interactions control methane cycling and isotopic composition in this vast estuarine system.

Near-shore environments are a significant source of atmospheric methane but the size of this source is poorly constrained, particularly for fjords and fjards. This study investigated the methane emission rates and the drivers controlling the dynamics of dissolved methane in the Saguenay Fjord, a deep, stratified, and well-oxygenated subarctic fjord system in eastern Canada. Dissolved methane concentrations ([CH4]) in the water column were measured in October 2016 and June, October, and November 2017, with stable carbon isotope composition of methane (delta(CCH4)-C-13) analyzed during the November 2017 survey. Surface-water [CH4] ranged from 16 to 184 nmol L-1 and decreased with increasing salinity in a bi-segment linear manner, inferring a temporally constant marine endmember but a freshwater discharge-dependent river endmember. The multi-cruises dataset yields a mean [CH4] saturation ratio of 12.7 (range: 4.5-48.7) and a mean emission rate of 53.4 mu mol m 2 d 1 (range: 16.4-256.9 mu mol m(-2) d(-1)). [CH4] was generally higher in surface water than in deep water. However, sillinduced mixing could homogenize [CH4] near the mouth of the fjord and sedimentary input of biogenic methane (delta(CCH4)-C-13: 57.660%) in the fjord's head region increased [CH4] in the overlying bottom water up to 459 nmol L-1. The longitudinal pattern of [CH4] below the surface layer was primarily controlled by deep-water renewal events. Deep-water [CH4] declined with rising apparent oxygen utilization, suggestive of aerobic microbial methane oxidation at rates estimated to be <0.1 nmol L-1 d(-1). The delta(CCH4)-C-13 data yields a carbon isotopic fractionation factor of 1.08 in both the surface and deep waters that points to microbial oxidation dictating the carbon isotopic fractionation of methane in the fjord. Mass-balance budgeting reveals that river runoff accounts for 81% of the total methane input to the fjord (12.13 x 10(6) mol year(-1)) and that microbial oxidation of methane (4.45 x 10(6) mol year(-1)) is comparable to emission to the atmosphere (4.27 x 10(6) mol year(-1)). This study demonstrates the important roles of river runoff and deep-water renewal in controlling the dynamics of [CH4], delta(CCH4)-C-13, and methane emission to air in fjords receiving large terrestrial freshwater discharges and experiencing frequent deep-water renewals. The areal methane emission rates for deep fjords obtained by this and earlier studies are one to two orders of magnitude higher than the mean flux estimate for global coastal oceans, placing fjords and fjards as a potentially significant contributor to coastal methane emission.

A multi-institutional initiative was created in a context of potential oil exploration at the Old Harry site to monitor the marine ecosystem and manage resources of the Gulf of St. Lawrence (GSL). As part of this initiative, two sediment traps were deployed at depths of 34 m and 100 m at a site northwest of Cabot Strait in the Laurentian Channel to measure downward carbon fluxes from October 2014 to October 2015. Fluxes of particulate organic carbon (POC), biogenic silica (BSi), chloropigments, protists and zooplankton fecal pellets were used to evaluate vertical and temporal changes in the magnitude and composition of biogenic carbon fluxes and to provide baseline information prior to any exploration activities in the region. Peaks in POC, BSi, chloropigment and diatom fluxes at both depths at the end of April 2015 indicated the rapid export of a locally-produced bloom mainly composed of pennate diatoms. A coincident peak in fecal pellet carbon fluxes at 100 m indicated a match between the spring ascent of copepods and the diatom bloom. The distinct composition of protist fluxes at 34 and 100 m following the formation of the winter mixed layer highlighted the influence of the pycnocline as a physical barrier for the export of particles in the region. Among identifiable components, dinoflagellates and fecal pellets, followed by diatoms and foraminifera, contributed most to the annual POC flux at 100 m, indicating a balance between lateral advection of slow-sinking protists and rapid export of fast-sinking diatoms and fecal pellets in the supply of POC toward the seafloor in the GSL. These measurements of biogenic carbon export provide insight into the fate of large and small particles in the Cabot Strait region to consider in the potential development of oil and gas activities.

This study presents in detail a new climate index for the Newfoundland and Labrador (NL) shelf. The NL climate index (NLCI) aims to describe the environmental conditions on the NL shelf and in the Northwest Atlantic as a whole. It consists of the average of 10 normalized anomalies, or subindices, derived annually: winter North Atlantic Oscillation, air temperature, sea ice season severity, iceberg count, seasonal sea surface temperature, vertically averaged temperature and salinity at the Atlantic Zone Monitoring Program (AZMP) Station 27, summer cold intermediate layer (CIL) core temperature at AZMP Station 27, summer CIL area on three AZMP hydrographic sections, and bottom temperature on the NL shelf. This index runs from 1951 to 2020 and will be updated annually. It provides continuity in the production of advice for fisheries management and ecosystem status on the NL shelf, for which a similar but recently abandoned index was used. The new climate index and its subindices are available at https://doi.org/10.20383/101.0301 (Cyr and Galbraith, 2020).

The St. Lawrence Estuary connects the Great Lakes with the Atlantic Ocean. The accepted view, based on summer conditions, is that the estuary's surface layer receives its nutrient supply from vertical mixing processes. This mixing is caused by the estuarine circulation and tides interacting with the topography at the head of the Laurentian Channel. During winter when ice forms, historical process-based studies have been limited in scope. Winter monitoring has been typically confined to vertical profiles of salinity and temperature as well as near-surface water samples collected from a helicopter for nutrient analysis. In 2018, however, the Canadian Coast Guard approved a science team to sample in tandem with its ice-breaking and ship escorting operations. This opportunistic sampling provided the first winter turbulence observations, which covered the largest spatial extent ever measured during any season within the St. Lawrence Estuary and the Gulf of St. Lawrence. The nitrate enrichment from tidal mixing resulted in an upward nitrate flux of about 30 nmol m−2 s−1, comparable to summer values obtained at the same tidal phase. Further downstream, deep nutrient-rich water from the gulf was mixed into the subsurface nutrient-poor layer at a rate more than an order of magnitude smaller than at the head. These fluxes were compared to the nutrient load of the upstream St. Lawrence River. Contrary to previous assumptions, fluvial nitrate inputs are the most significant source of nitrate in the estuary. Nitrate loads from vertical mixing processes would only exceed those from fluvial sources at the end of summer when fluvial inputs reach their annual minimum.

Uncertainties in fish tracking studies limit their integration into conservation and fisheries management plans. This is especially true for archival tagging studies that rely on geolocation models to infer fish tracks from recorded environmental variables. Hidden Markov Models (HMMs) are increasingly popular to geolocate marine fish equipped with archival tags; however, true errors and sensitivity of geolocation HMMs are seldom evaluated. In this study, we first review validation methods and implementations of geolocation HMMs to adapt to regional oceanography, fish species and tag data. We then use a case-study to evaluate strengths and limitations of each validation approach and to illustrate the sensitivity of geolocation HMMs to implementation assumptions. Simulated and fixed tag locations are the most widely implemented methods, but less common methods relying on true fish tracking, that is double-tagging or distance from recapture experiments, provide more informative estimates of model accuracy and precision. Results showed that model performance can be improved using simple assumptions when pre-processing tag data rather than using a complex movement behaviour model. In addition, accelerometer show potential to further parameterise geolocation models. Overall, results from our case-study and previous studies showed that current geolocation HMMs have average errors of ca. 30-50 and 120 km for demersal and large pelagic fish, respectively. We suggest that these errors are acceptable for investigations at the scale of fisheries management units.