Canadian Institute of Ocean Sciences

Victoria, Canada

Canadian Institute of Ocean Sciences

Victoria, Canada
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Connolly T.P.,Woods Hole Oceanographic Institution | Hickey B.M.,University of Washington | Shulman I.,U.S. Navy | Thomson R.E.,Canadian Institute of Ocean Sciences
Journal of Physical Oceanography | Year: 2014

The California Undercurrent (CUC), a poleward-flowing feature over the continental slope, is a key transport pathway along the west coast of North America and an important component of regional upwelling dynamics. This study examines the poleward undercurrent and alongshore pressure gradients in the northern California Current System (CCS), where local wind stress forcing is relatively weak. The dynamics of the undercurrent are compared in the primitive equation Navy Coastal Ocean Model and a linear coastal trapped wave model. Both models are validated using hydrographic data and current-meter observations in the core of the undercurrent in the northern CCS. In the linear model, variability in the predominantly equatorward wind stress along the U.S. West Coast produces episodic reversals to poleward flow over the northern CCS slope during summer. However, reproducing the persistence of the undercurrent during late summer requires additional incoming energy from sea level variability applied south of the region of the strongest wind forcing. The relative importance of the barotropic and baroclinic components of the modeled alongshore pressure gradient changes with latitude. In contrast to the southern and central portions of the CCS, the baroclinic component of the alongshore pressure gradient provides the primary poleward force at CUC depths over the northern CCS slope. At time scales from weeks to months, the alongshore pressure gradient force is primarily balanced by the Coriolis force associated with onshore flow. © 2014 American Meteorological Society.

Batten S.D.,Sir Alister Hardy Foundation for Ocean Science | Gower J.F.R.,Canadian Institute of Ocean Sciences
Journal of Plankton Research | Year: 2014

Deliberate fertilization of a patch of water west of Haida Gwaii, British Columbia, with iron sulphate and oxide occurred in summer 2012 and triggered a phytoplankton bloom strongly visible in satellite imagery in late August and detectable through September 2012. Routine sampling by the Continuous Plankton Recorder Survey from commercial ships occurred in the vicinity of the fertilized patch between April and October that year. Comparisons with samples from the same region in the years 2000-2011 showed that phytoplankton and microzooplankton abundance indices were the lowest recorded over the time series in the autumn of 2012, while crustacean zooplankton were higher than average, and often higher than previously recorded in the autumn. Possible other contributory factors are discussed but this evidence suggests that the iron-induced bloom could have caused an increase in zooplankton that in turn exerted a heavy grazing pressure on the large phytoplankton and microzooplankton by the autumn of 2012. © 2014 The Author. Published by Oxford University Press. All rights reserved.

Mucci A.,McGill University | Lansard B.,McGill University | Miller L.A.,Canadian Institute of Ocean Sciences | Papakyriakou T.N.,University of Manitoba
Journal of Geophysical Research: Oceans | Year: 2010

Surface mixed layer CO2 fugacities (fCO2-sw) calculated from carbonate system parameters in the southeastern Beaufort Sea during the ice-free period ranged from 240 to 350 μatm in fall 2003 and from 175 to 515 μatm in summer 2004. The surface mixed layer remains mostly undersaturated with respect to atmospheric CO2 (378 μatm) and, therefore, acts as a potential CO2 sink throughout this period. Air-sea CO2 fluxes (FCO2) were first computed assuming ice-free conditions and ranged from -32.4 to +8.6 mmol m-2 d -1 in fall 2003 and summer 2004, respectively. Then we included a reduction factor to account for ice cover (ic) and we computed the resulting fluxes (FCO2-ic). In fall 2003, FCO2-ic ranged from -4.7 mmol m-2 d-1 in the relatively open water of the Cape Bathurst Polynya to -0.1 mmol m-2 d-1 in the southeastern Beaufort Sea, limited by the presence of the multiyear sea ice. In summer 2004, FCO2-ic ranged from -13.1 mmol m-2 d-1 on the western Mackenzie Shelf to +8.6 mmol m-2 d-1 at Cape Bathurst; the variability being ascribed to competing effects of vertical mixing, temperature variations, and possibly biological production. On average, a net sink of -2.3 ± 3.5 mmol m-2 d-1 was estimated for the ice-free period over the study area. Nevertheless, the FCO2 displays strong variability due to ice coverage, freshwater input, and upwelling events. The potential responses (direction and intensity of potential feedbacks) of the carbon cycle in the study area to a changing Arctic climate are discussed. © 2010 by the American Geophysical Union.

Fine I.V.,Canadian Institute of Ocean Sciences | Kulikov E.A.,RAS Shirshov Institute of Oceanology | Cherniawsky J.Y.,Canadian Institute of Ocean Sciences
Pure and Applied Geophysics | Year: 2013

We use a numerical tsunami model to describe wave energy decay and transformation in the Pacific Ocean during the 2011 Tohoku tsunami. The numerical model was initialised with the results from a seismological finite fault model and validated using deep-ocean bottom pressure records from DARTs, from the NEPTUNE-Canada cabled observatory, as well as data from four satellite altimetry passes. We used statistical analysis of the available observations collected during the Japan 2011 tsunami and of the corresponding numerical model to demonstrate that the temporal evolution of tsunami wave energy in the Pacific Ocean leads to the wave energy equipartition law. Similar equipartition laws are well known for wave multi-scattering processes in seismology, electromagnetism and acoustics. We also show that the long-term near-equilibrium state is governed by this law: after the passage of the tsunami front, the tsunami wave energy density tends to be inversely proportional to the water depth. This fact leads to a definition of tsunami wave intensity that is simply energy density times the depth. This wave intensity fills the Pacific Ocean basin uniformly, except for the areas of energy sinks in the Southern Ocean and Bering Sea. © 2012 Springer Basel AG.

Cronin M.F.,National Oceanic and Atmospheric Administration | Pelland N.A.,University of Washington | Emerson S.R.,University of Washington | Crawford W.R.,Canadian Institute of Ocean Sciences
Journal of Geophysical Research: Oceans | Year: 2015

Data from two National Oceanographic and Atmospheric Administration (NOAA) surface moorings in the North Pacific, in combination with data from satellite, Argo floats and glider (when available), are used to evaluate the residual diffusive flux of heat across the base of the mixed layer from the surface mixed layer heat budget. The diffusion coefficient (i.e., diffusivity) is then computed by dividing the diffusive flux by the temperature gradient in the 20 m transition layer just below the base of the mixed layer. At Station Papa in the NE Pacific subpolar gyre, this diffusivity is 1 × 10-4 m2/s during summer, increasing to ∼3 × 10-4 m2/s during fall. During late winter and early spring, diffusivity has large errors. At other times, diffusivity computed from the mixed layer salt budget at Papa correlate with those from the heat budget, giving confidence that the results are robust for all seasons except late winter-early spring and can be used for other tracers. In comparison, at the Kuroshio Extension Observatory (KEO) in the NW Pacific subtropical recirculation gyre, somewhat larger diffusivities are found based upon the mixed layer heat budget: ∼ 3 × 10-4 m2/s during the warm season and more than an order of magnitude larger during the winter, although again, wintertime errors are large. These larger values at KEO appear to be due to the increased turbulence associated with the summertime typhoons, and weaker wintertime stratification. © 2015. The Authors.

Recently compiled databases facilitated estimation of basin-wide benthic organic biomass and turnover in the Strait of Georgia, an inland sea off western Canada. Basin-wide organic biomass was estimated at 43.1×106kgC and production was 54.6×106kgCyr-1, resulting in organic biomass turnover (P/B) of 1.27×yr-1. Organic biomass and production for sub-regions were predictable from modified organic flux (r2>0.9). P/B declined significantly with increasing modified organic flux, suggesting greater biomass storage in high flux sediments. Biomass and production were highest, and P/B lowest near the Fraser River. Annual basin-wide benthic production was 60% of previously estimated oxidized organic flux to substrates, which agrees with proportional measurements from a recent, localized study.Deviations from expected patterns related to organic enrichment and other stressors are discussed, as are potential impacts to benthic biomass and production, of declining bottom oxygen, increasing bottom temperature and potential changes in riverine input. © 2014 Elsevier Ltd.

Gower J.F.R.,Canadian Institute of Ocean Sciences
Remote Sensing Letters | Year: 2014

The Fluorescence Line Height (FLH) algorithm provides a standard method of measuring solar-stimulated chlorophyll fluorescence from coastal and ocean waters using the Moderate Resolution Imaging Spectroradiometer (MODIS), the Medium Resolution Imaging Spectrometer (MERIS) or other satellite sensors having the necessary spectral bands near 680 nm. In many coastal areas, this can provide superior estimates of chlorophyll concentration when compared to estimates derived from the standard green/blue algorithms. However, at least one significant data supplier normalizes the derived FLH values (to Normalized Fluorescence Line Height) on the assumption that the fluorescence signal is proportional to local solar irradiance. This is not the case, and normalization results in errors which make the fluorescence data much less useful. This paper demonstrates that FLH should be used as a measure of chlorophyll concentration without normalization. © 2014 Taylor and Francis.

Gower J.,Canadian Institute of Ocean Sciences | King S.,Canadian Institute of Ocean Sciences
International Journal of Remote Sensing | Year: 2012

This article demonstrates a successful application of fluorescence line height (FLH) images from the Medium Resolution Imaging Spectrometer (MERIS) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagers and provides a strong argument for making more widespread use of FLH in monitoring surface phytoplankton in coastal waters. In the present example, MERIS and MODIS FLH images show the start of the spring bloom in coastal waters of the Strait of Georgia in British Columbia, Canada. The images clearly show a recurring pattern in five of the eight years from 2003 to 2010 covered by MERIS, which suggests seeding of the early spring bloom from narrow coastal inlets. Such seeding has been suggested before, but never observed. FLH images show the blooms more clearly than images of surface chlorophyll based on the ratios of water-leaving radiances in the blue and green spectral range (440-560 nm). FLH images used here have been derived with no atmospheric correction. Alternative products based on the blue/green ratio require atmospheric correction, which is difficult in coastal areas. Such products also tend to be more significantly confused with other constituents of coastal waters. © 2012 Copyright Taylor and Francis Group, LLC.

Walters R.A.,Canadian Institute of Ocean Sciences | Tarbotton M.R.,Triton Consultants Ltd | Hiles C.E.,Cascadia Coast Research Ltd
Renewable Energy | Year: 2013

Several approaches can be used for estimating tidal power potential. From a theoretical point of view, others have shown that the problem can be reduced to a single or multiple boundary problem with simple geometry where each case has a well defined maximum power potential. From a practical point of view, the potential can be approximated from the ambient flow. Questions naturally arise whether the theoretical approach can be applied to a typical field-scale problem, and whether the practical approach has any validity. In order to provide more insight into these questions, form drag representing tidal turbines has been introduced into a numerical flow model. This is an unstructured grid model with an implicit treatment of wetting and drying that has been shown to be robust, accurate, and efficient for highly irregular coastal ocean environments and is well suited for this problem. The field site that has been examined is Minas Passage in the Bay of Fundy which provides an interesting practical perspective for this problem. In the end, only a fraction of the theoretical maximum power potential can be realized in practice because of physical constraints on the maximum form drag for tidal turbines. © 2012 Elsevier Ltd.

Rabe B.,University of Delaware | Munchow A.,University of Delaware | Johnson H.L.,University of Oxford | Melling H.,Canadian Institute of Ocean Sciences
Journal of Geophysical Research: Oceans | Year: 2010

Nares Strait to the west of Greenland facilitates the exchange of heat and freshwater between the Arctic and Atlantic Oceans. This study focuses on salinity, temperature, and density measurements from Nares Strait from a mooring array deployed from 2003 to 2006. Innovative moorings requiring novel analysis methods measured seawater properties near 80.5°N, at spacing sufficient to resolve the internal Rossby deformation radius. The 3-year mean geostrophic velocity has a surface-intensified southward flow of 0.20 m s-1 against the western side of the strait and a secondary core flowing southward at 0.14 m s-1 in the middle of the strait. Data show warm salty water on the Greenland side and cold fresher water on the Ellesmere Island side, especially in the top layers. There was a clear difference in hydrographic structure between times when sea ice was drifting and when it was land fast. Ice was drifting in late summer, fall, and early winter with a strong surface-intensified geostrophic flow in the middle of the strait. Ice was land fast in late winter, spring, and early summer, when there was a subsurface core of strong geostrophic flow adjacent to the western side of the strait. Salinity variations of about 2 psu in time and space reflect a variable freshwater outflow from the Arctic Ocean. One particularly strong pulse occurred at the end of July 2005. For several days, steeply sloping isohalines indicated strong geostrophic flow down the middle of the strait coinciding with an amplified ice export from the Arctic due to strong southward winds. Copyright 2010 by the American Geophysical Union.

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