ABSTRACTUpper-level winds are primarily measured by tracking the position of radiosonde balloons as they rise through the atmosphere. Radiosondes are released from a global network at 0000 utc and 1200 utc each day, and data are quickly available to the world's weather services, as well as to the public. The network is relatively coarse spatially, and there are normally only two soundings per day. In an endeavour to provide better spatial and temporal upper-level regional wind measurements, the O-QNet (a demonstration very high frequency wind profiler network for Ontario and Quebec) was installed and has been operated by York, Western, and McGill Universities with support from Mardoc Inc., The Weather Network, and Environment and Climate Change Canada. Initial funding was provided by the Canada Foundation for Innovation, the Ontario Innovation Trust, and Mardoc Inc. The present paper reports primarily on comparisons between winds measured by the O-QNet profilers and the winds reported in the North American Regional Reanalysis (NARR). There is good agreement between the two, which provides support for the use of NARR data to investigate longer term variations in upper-level winds associated with climate change for this region.

ABSTRACTAcoustic Doppler Current Profilers and underwater gliders were simultaneously deployed as part of the Ocean Tracking Network to continuously monitor the Halifax Line (HL) and the Nova Scotia Current (NSC) between 2008 and 2014. The HL transects the Scotian Shelf, which connects dynamically important areas, such as the Grand Banks, the Gulf of Maine, and the Gulf of St. Lawrence (GSL). The oceanographic measurements made at the HL during this period provide a unique opportunity to study the temperature, salinity, and alongshore current conditions and variability at both seasonal and interannual time scales. The analysis of observations reveals that the water over the Scotian Shelf is mainly composed of water coming from the Gulf of St. Lawrence (Cabot Strait subsurface water) in the upper layer (30 to 50 m, 81%) and Warm Slope Water below 100 m (77%), highlighting the connectivity between the GSL and the Scotian Shelf. The temperature–salinity characteristics of the Cold Intermediate Layer (CIL) observed along the HL and located mainly between 50 and 100 m, is indistinguishably influenced by both water coming from the Inshore Branch of the Labrador Current and CIL water formed in the GSL. These proportions stay similar over interannual time scales, suggesting that the 2012 warm anomaly observed over the Scotian Shelf is primarily driven by the advection of already anomalously warm water coming from offshore regions. The analysis of glider data also reveals that most of the alongshore transport over the Scotian Shelf occurs within the first 60 km from the coast, where the NSC is located. It was found that the freshwater discharge from the St. Lawrence River at Québec and the alongshore transport across the NSC have a significant covariance at a 9-month lag. The Empirical Orthogonal Function (EOF) analysis demonstrates that most of the current variability (between 78 and 92%) can be explained by the first EOF, which represents the baroclinicity resulting from the freshwater outflow coming from the GSL. Part of the second EOF is associated with the local wind forcing and explains between 4 and 14% of the NSC variability.

ABSTRACTA one-dimensional model was run to hindcast water levels and flows for the St. Lawrence River between Montréal and Saint-Joseph-de-la-Rive (100 km east of Québec, Canada). At the upstream boundary, the model uses the flows from Lake Ontario and the Ottawa River basin through lakes Saint-Louis and des Deux-Montagnes and from tributary rivers inside the domain, while at the downstream boundary, it uses water level observations and wind forcing, over the 2005–2012 period. Observations of water level in real time are available at 18 water level gauges but model results provide values at 1061 positions within the domain. The water flow is not measured in real time. Calibration of the model flows provides the ability to issue the flow at the same positions and at the same 3-minute frequency as the water level. Daily flow hindcasts of the St. Lawrence River at Québec over the period is presented. The uncertainties associated with the model results are evaluated using water level and flow observations.

ABSTRACTA long-term record of surface currents from a high-frequency radar system, along with near-surface hydrographic transects, moored current meter records, and satellite imagery, are analyzed to determine the relative importance of river discharge, wind, and tides in driving the surface flow in the Fraser River plume. The observations show a great deal of oceanographic and instrumental variability. However, averaged quantities yielded robust results. The effect of river flow, which determines buoyancy and inertia near the river mouth, was found by taking a long-term average. The resulting flow field was dominated by a jet with two asymmetric gyres; the anticyclonic gyre to the north had flow speeds consistent with geostrophy. The mean flow speed near the river mouth was 14.3 cm s–1, while the flow further afield was 5 cm s–1 or less. Wind stress and surface currents were highly coherent in the subtidal frequency band. Northwesterly winds drive a surface flow to the southeast at speeds of nearly 30 cm s–1. Southeasterly winds drive a surface flow to the northwest at speeds reaching 20 cm s–1; however, there is more spatial variability in speed and direction relative to the northwesterly wind case. A harmonic analysis was used to extract the tidally driven flows. Ellipse parameters for the major tidal constituents varied considerably in both alignment and aspect ratio over the radar domain, in direct contrast to a barotropic model which predicted rectilinear flow along the Strait of Georgia. This is a result of water filling and draining the shallow mud flats north of the Fraser's main channel. The M2 velocities at the surface were also weaker than their barotropic counterparts. However, the shallow water constituent MK3 was enhanced at the surface and nearly as strong as the mean flow, implying that non-linear interactions are important to surface dynamics.

The atmospheric boundary layer mixing height (MH) is an important bulk parameter in air quality (AQ) modelling. Formulating this parameter under statically stable conditions, such as in the Arctic, has historically been difficult. In an effort to improve AQ modelling capacity in North America, MH is studied in two geographically distinct areas: the Arctic (Barrow, Alaska) and the southern Great Plains (Lamont, Oklahoma). Observational data from the Atmospheric Radiation Measurement program, Climate Research Facility and numerical weather forecasting data from Environment Canada's Regional Global Environmental Multiscale (GEM15) model have been used in order to examine the suitability of available parameterizations for MH under statically stable conditions and also to compare the level of agreement between observed and modelled MH. The analysis period is 1 October 2011 to 1 October 2012. The observations alone suggest that profile methods are preferred over surface methods in defining MH under statically stable conditions. Surface methods exhibit poorer comparison statistics with observations than profile methods. In addition, the fitted constants for surface methods are site-dependent, precluding their applicability for modelling under general conditions. The comparison of observations and GEM15 MH suggests that although the agreement is acceptable in Lamont, the default model surface method contributes to a consistent overprediction of MH in Barrow in all seasons. An alternative profile method for MH is suggested based on the bulk Richardson number. This method is shown to reduce the model bias in Barrow by a factor of two without affecting model performance in Lamont.

ABSTRACTMonthly output from a high-resolution numerical ocean model simulation of the North Atlantic Ocean for the 1990–2011 period is analyzed to investigate the properties and relationships between the various current streams in Atlantic Canadian shelf waters at seasonal and annual time scales. Particular focus is placed on the sections of the Atlantic Zone Monitoring Program, which are subdivided into nearshore and shelf-break components. At seasonal time scales, model results indicate that all nearshore series exhibit seasonal cycles with minima during mid-year, but shelf-break series do not. The seasonal cycles are consistent with the barotropic component of the Arctic melt cycle. At annual time scales, shelf-break series show generally decreasing correlations with increasing downstream distance. Correlation coefficients of approximately 0.5 exist for sections on the Newfoundland and Scotian shelves separated by over 2000 km. Remarkably, no correlation is found for the inshore Labrador Current and the flow through the Strait of Belle Isle or other downstream sections. The transport through these sections is found to correlate with across- and along-shelf sea level gradients. On the Scotian Shelf, nearshore series exhibit decreasing sequential correlation. Behaviour of flows into the Gulf of Maine is consistent with a conservation of volume relation whereby an increase in the Nova Scotia Current is compensated for by less inflow and more outflow through the Northeast Channel (and vice versa).

The Minister of the Environment announced a $148.8 million Government of Canada climate change adaptation initiative, a thematic area under the Government's Clean Air Agenda, in November 2011. Fish...

ABSTRACTIn this study an individual-based numerical model with three-dimensional (3D) and time-dependent fields of circulation and hydrography is used to examine the effects of the physical environment and various biological behaviours on the distribution and movement of particles in the Gulf of St. Lawrence and adjacent waters. The 3D circulation and hydrographic fields are simulated by a numerical ocean circulation model. The model domain covers the St. Lawrence Estuary (SLE), the Gulf of St. Lawrence (GSL), the Scotian Shelf, the Gulf of Maine, and their adjacent waters. The basis of the individual-based model is a numerical scheme that tracks the movement of particles carried by ocean currents. Several swimming behaviours of marine animals are considered with efficient seaward migration in the GSL as the goal. Electronic tagging data for the American eel (Anguilla rostrata) are used as guidance in specifying the behaviours. It is demonstrated that particles that undergo an observed behaviour, known as selective tidal stream transport, are able to exit the SLE more efficiently than particles that are carried passively by the 3D ocean currents. Outside the SLE, particles that search for and swim towards higher salinity move further downstream than those that have a preference for deeper water or swim in random directions.

Key physical variables for the Northwest Atlantic (NWA) are examined in the “historical” and two future Representative Concentration Pathway (RCP) simulations of six Earth System Models (ESMs) available through Phase 5 of the Climate Model Intercomparison Project (CMIP5). The variables are air temperature, sea-ice concentration, surface and subsurface ocean temperature and salinity, and ocean mixed-layer depth. Comparison of the historical simulations with observations indicates that the models provide a good qualitative and approximate quantitative representation of many of the large-scale climatological features in the NWA (e.g., annual cycles and spatial patterns). However, the models represent the detailed structure of some important NWA ocean and ice features poorly, such that caution is needed in the use of their projected future changes. Monthly “climate change” fields between the bidecades 1986–2005 and 2046–2065 are described, using ensemble statistics of the changes across the six ESMs. The results point to warmer air temperatures everywhere, warmer surface ocean temperatures in most areas, reduced sea-ice extent and, in most areas, reduced surface salinities and mixed-layer depths. However, the magnitudes of the inter-model differences in the projected changes are comparable to those of the ensemble-mean changes in many cases, such that robust quantitative projections are generally not possible for the NWA.

A three dimensional ice–ocean coupled model with a 7 km horizontal resolution has been developed to examine spatial and seasonal variability of hydrography and circulation over the Newfoundland and Labrador Shelves. Daily atmospheric forcing is applied and monthly open boundary forcing is prescribed based on a global ocean assimilation model. Monthly mean results averaged over a simulation period from 1979 to 2010 are evaluated using a variety of temperature, salinity, current, and ice observations. In comparison with observations and previous model results, the present model shows good skill in simulating the inshore and shelf-edge Labrador Current. The model temperature and salinity agree well with observations. Model sea-ice extent compares well with observations. The model mean transport is approximately 7.5 and 0.7 Sv (Sv = 106 m3 s−1) for the shelf-edge and inshore branches of the Labrador Current, respectively, consistent with observational estimates. The modelled total transport from the coast to the central Labrador Sea is 27.5 Sv from June to September, in good agreement with the observational estimate. The seasonal range for the shelf-edge and inshore branches is 2.0 and 0.6 Sv, respectively, strong in winter and fall and weak in spring and summer. The model mean freshwater transport at the Seal Island and Flemish Cap transects is 0.12 and 0.14 Sv, respectively, consistent with observational estimates, and the range of the seasonal freshwater transport is 0.09 Sv and 0.04 Sv for each transect, respectively, which is approximately in phase with the volume transport.