Remote sensing of chlorophyll concentration is potentially affected by the presence of inorganic matter in the water column. Seasonal variability of total suspended particulate matter (SPM) concentration and its partition into organic and inorganic fractions was thus measured in the estuary and Gulf of St. Lawrence during five cruises. These measures were made in the surface layer down to the depth of the 0.1% light level. Results indicate that vertical variability was small for the entire study area. Data analysis lead to the definition of two main regions having different SPM characteristics: 1) the estuary zone characterized by a strong spatial variability, intermediate SPM concentrations and a clear spring phytoplankton bloom that is combined to an increased inorganic matter load; 2) the gulf region characterized by a relatively low SPM concentration and phytoplankton blooms in the spring and fall periods. Combined with in situ measurements of remote sensing reflectances, the database was used to validate existing inorganic matter retrieval algorithms and develop a new one better adapted to the low concentrations encountered in the St. Lawrence estuary and Gulf.

During the 2004 Canadian Arctic Shelf Exchanges Study (CASES) field program, an extensive in situ bio-optical data set covering the Cape Bathurst polynya was acquired. This data set was used to evaluate the performance of the OC4v4 (SeaWiFS) and OC3M (MODIS) ocean color algorithms, and to develop locally tuned ones for that region that is affected by the presence of high concentration of colored dissolved organic matter (CDOM) that contaminates the reflectance signal. The OC4v4 and the OC3M algorithms overestimated in situ chlorophyll a by roughly a factor of four. The western Beaufort sea versions of the SeaWiFS algorithm (OC4L and OC4P) provided slightly better results but still highly overestimated chlorophyll. Our new regional algorithms showed a much improved performance (MNB=5.33%) allowing for a better estimation of the chlorophyll concentration.

In order to verify the ability of RADARSAT-1 images to detect mesoscale oceanic features and the possible link of these oceanographic patterns with jack mackerel (Trachurus murphyi) distribution in the waters off central Chile, a project was developed as part of the Canada Centre for Remote Sensing Globesar-2 program. The combined use of simultaneously acquired RADARSAT-1, AVHRR sea surface temperature (SST), SeaWiFS Chlorophyll a concentration (Chl), TOPEX/ERS altimeter and ERS-2 scatterometer wind data greatly enhanced SAR imaging capabilities for the detection of oceanic features. Results show that detection of coastal wind-driven upwellings, eddies, frontal boundaries and phytoplankton blooms is possible using SAR imagery, given the proper environmental conditions. Results also suggest that jack mackerel distribution coastal resources is mainly associated with frontal boundaries, upwelling waters and high chlorophyll concentrations detected by the remotely sensing images

The North Water, a large polynya in northern Baffin Bay, has an extensive period of continuous primary production lasting up to 6 months. The well-known richness of this polynya in higher trophic levels, including numerous marine mammals and birds, must be based on the magnitude and duration of that production. As part of the International North Water Polynya Study, we observed that two groups of phytoplankton were responsible for most of the primary production in 1997–1999: the large centric diatoms, Thalassiosira spp., and the smaller, colonial centric diatom, Chaetoceros socialis Lauder. We studied the phytoplankton community assemblage in the North Water in August 1997, April–July 1998, and August–September 1999 using epifluorescence microscopy on samples fixed and filtered at sea, with unpreserved cells observed in July 1998. Blooms of C. socialis occurred at southern stations in June and throughout the polynya from July to September. Maximum concentrations reached 30,100 cellsml−1 (496μg Cl−1) in the western area in early July. Blooms of C. socialis directly followed those of Thalassiosira spp., which were more intense but also more transient. C. socialis appeared to maintain its population in the euphotic layer for up to 3 months by surviving at low nutrient levels, sinking to depths where dynamic physical regimes brought nutrient replenishment, and producing resting spores (up to 233μg Cl−1). The resting spores may survive low-nutrient periods and be introduced, some from fecal pellets, to waters of more favorable growth conditions; in July, 86% of fecal pellets and 76% of aggregates observed in shallow, floating sediment traps contained resting spores of C. socialis. Colonies of C. socialis were a potential mid-water food source and major contributor to the benthos: C. socialis contributed up to 91% of total phytoplankton cells (49% phytoplankton carbon) identified in moored sediment traps. Mats of polymer gels (mucous), likely formed from the observed C. socialis colonies, some containing frustule and setae fragments as well as resting spores, contributed massively to the material in traps in the southern and western polynya. C. socialis appears to be a very important primary producer throughout the productive season of the North Water.

A 4-month multidisciplinary expedition, beginning at the end of winter to track the spring phytoplankton bloom to its termination in summer, was conducted from April to July 1998. The aim of the expedition was to investigate possible mechanisms responsible for the high biological productivity of the North Water, the most productive and largest polynya in the Northern Hemisphere. The aims of the present study were to investigate: (1) the effects of the physical forces, driving the formation of the polynya, on the dynamics of the phytoplankton stock in the polynya over the spring–summer period; and (2) the factors that limit the maximum biomass of phytoplankton. Contrasting physical characteristics, including ice concentration, surface mixed-layer depth (MLD), salinity and temperature in the surface mixed layer (SML), were observed between the east and west sides of the polynya. The Greenland (eastern) side of the polynya was characterized by a shallow SML, warm temperature, and high salinity relative to the Ellesmere Island, Canada (western) side. Chlorophyll a (Chl)>1 mg m−3 was observed in late April on the eastern side, and in late May on the western side. The peak phytoplankton bloom occurred in the southeastern part of the polynya, with average Chl of 15 mg m−3 (240–300 mg m−2) in the euphotic zone during the end of May and beginning of June. The increased phytoplankton biomass was associated with higher salinity and warmer temperature on the eastern side of the polynya. Low temperature in April and May decoupled the increase of Chl biomass from the shallowed SML, as predicted by Sverdrup's model. As Chl in the euphotic zone increased to 5 mg m−3, the proportion of light absorption by phytoplankton could not increase further with Chl biomass, which might have limited the increase of primary production in the water column. Although the initial nutrient inventories largely determined the maximum biomass of phytoplankton, self-shading occurred in the build-up phytoplankton biomass to ∼5 mg m−3, which retarded the timing of the peak bloom. Both sensible heat due to deep warm water entrainment into the SML and the biological heating effect via phytoplankton light absorption appear to contribute to the pattern of phytoplankton distribution in the North Water.

The timing of copepodite recruitment and population development of copepods in spring and early summer (April-July) were compared between the North Water polynya and Barrow Strait, a non-polynya region in the Canadian Archipelago. In the North Water, young copepodites (CI-CIII) of calanoid herbivores were concentrated in the cold and chlorophyll-rich water at the base of the Arctic surface layer, while later stages (CIV-CV) invaded the warmer surface layer. The phytoplankton bloom and the recruitment of the first cohort of copepodites of Calanus hyperboreus, C. glacialis, and Pseudocalanus spp started in May-June, some 1.5-3 months earlier than in Barrow Strait. Consistent with a precocious summer recruitment, population stage structure of these species in early spring (April-May) was more advanced in the North Water than in Barrow Strait. The recruitment in June of Cl of the omnivore Metridia longa was advanced by at least 5 weeks in the polynya relative to Barrow Strait. We found no evidence for an acceleration of the population development of the small Microcalanus pygmaeus, Oithona similis or Oncaea borealis in the polynya.Once the recruitment of young copepodites had started, recruitment success (i.e. % of young copepodites in the population) increased primarily with Chl a concentration for C. hyperboreus, with both sea-surface temperature and Chl a for C. glacialis, and with temperature only for Pseudocalanus spp. Hence, depending on the species, both greater food availability and higher temperature resulting from reduced ice cover contributed to improve reproductive success in herbivorous copepods in the North Water relative to Barrow Strait. A climate-induced reduction of ice cover duration is predicted to favour the population growth of the predominant large calanoid copepods and Pseudocalanus on Arctic shelves. (C) 2002 Elsevier Science Ltd. All rights reserved.

The seasonal patterns of phytoplankton biomass and production were determined in the North Water, located between Greenland and Ellesmere Island (Canadian Arctic), in August 1997, April–July 1998, and August–September 1999. The patterns differed among the four defined regions of this large polynya, i.e. North (>77.5°N), East (>75°W), West (<75°W), and South (<76°N). Phytoplankton biomass and production were low during April throughout the North Water. Biomass first increased in the East during April. From there, the biomass spread north- and westwards during May–June, when the bloom culminated (chlorophyll a concentrations up to 19.8 mg m−3). The large-sized (>5 μm) fraction dominated the biomass and production during the bloom. During July, August, and September, biomass and production decreased over the whole region, with the highest biomass, dominated by large cells, occurring in the North. The annual particulate and dissolved phytoplankton production were the highest ever reported for the high Arctic, reaching maximum values of 254 and 123 g C m−2 yr−1, respectively, in the East. Rates in the North and West were considerably lower than in the East (ca. two- and three-fold, respectively). The f-ratios (i.e. ratio of new to total production), derived from the size structure of phytoplankton, were high north of 76°N (0.4–0.7). Regionally, this indicated a high potential export of particulate organic carbon (EPOC) from the phytoplankton community to other trophic compartments and/or downwards in the East (155 g C m−2 yr−1), with lower values in the North and West (i.e. 77 and 42 g C m−2 yr−1, respectively). The seasonal and spatial patterns of EPOC were consistent with independent estimates of potential carbon export. Phytoplankton biomass and production were generally dominated by the large size fraction, whereas EPOC seemed to be dominated by the large size fraction early in the season and by the small size fraction (<5 μm) from June until the end of the growing season.

The Upper St. Lawrence estuary is an area where many physical factors such as the wind, the freshwater runoff, the tides and the bathymetry interact to generate a strong spatio-temporal variability of measurable parameters. Six Landsat-5 Thematic Mapper thermal images were analysed to study the sea surface temperature spatial variability of this complex region. Results show that the bathymetry is the principal factor controlling this structure. Sea surface temperatures are usually warmer in shallower areas. Bathymetry is also responsible for the localization of the principal density front close to le aux Coudres. Finally, the results show that the sea surface temperature is influenced by the intense tidal mixing and by wind-induced upwellings. Data analysis finally showed that the Thematic Mapper sensor was able to significantly detect spatial temperature gradients that are stronger than 1°C. L'estuaire superieur du Saint-Laurent est une region ou interagissent divers facteurs physiques tels que le vent, le debit d'eau douce, la maree et la bathymetrie qui generent une forte variabilite spatio-temporelle des parametres mesurables. Six images thermiques du capteur Thematic Mapper de Landsat-5 ont ete analysees afin d'etudier la structure spatiale du champ de temperature de surface de cette region complexe. Les resultats montrent que la bathymetrie est le facteur principal controlant cette structure. Les temperatures de surface de l'eau sont ainsi generalement plus chaudes dans les zones moins profondes. La bathymetrie est aussi responsable de la position du principal front de densite situe pres de l' le aux Coudres. Finalement, les resultats montrent que la temperature de surface de l'eau est aussi affectee par endroits par le melange intense cause par la maree ainsi que par des remontees d'eau induites par le vent. L'analyse des donnees a finalement permis de montrer que le capteur TM permettait de detecter de facon significative des changements spatiaux de temperature de surface de la mer lorsque ceux-ci sont superieurs a environ 1°C.

We report here on a statistical study of physical-biological interactions in the Gulf of St. Lawrence that uses for the first time ocean color images (phytoplankton pigments) and data on runoff and wind. Based on a Monte Carlo test for statistical significance, we extracted four orthogonal (independent) spatial patterns (Empirical Orthogonal Functions, EOF) in pigments that explain 64% of the total variance. We also computed four EOFs from the wind data that explain 90% of the total variance. Based on multiple correlations among these EOFs and runoff anomalies, we derived two modes of physical-biological variability. The first mode is the dual regulation of production by runoff in the Lower St. Lawrence Estuary (LSLE) and the western Gulf and by alongshore wind stress in the northeastern Gulf. The second mode incorporates mesoscale circulation features (eddies, meanders) that respond to low frequency fluctuations in runoff (in the lower estuary) or wind (Gaspé Current, northwestern Gulf, northern Esquiman Channel). The third mode reflects the impact of seasonal wind regimes on pigment levels in the LSLE, the Gaspé Current, and the southwestern Gulf. The fourth mode is dominated by one coccolithophore bloom event in August 1979. The analysis also gives some insight into sources of interannual variability in pigment levels and distributions. The spring bloom does not dominate the seasonal pigment cycle; only the third pigment EOF (5% of the variation) displays a spring peak stronger than the fall peak. The seasonal cycle of pigments is in part linked to that of runoff, driven mostly by year to year differences in the spring freshet. However, year to year differences in the summer wind and runoff regimes also play a role. This suggests that late summer and fall blooms and the physical factors that regulate them deserve more study.

The aim of this note is to test an empirical algorithm using spectral curvature theory at selected SeaWiFS hyerspectral bands, in order to estimate the chlorophyll pigment concentrations in the coastal waters of Baie des Chaleurs (Gulf of St. Lawrence). Simulated SeaWiFS algorithms require the measurement of reflectances with a high sensitive spectroradiometer as well as the responsitivity of SeaWiFS sensor at each band. Volume reflectances were taken using a hand held spectroradiometer simultaneously to measurements of in situ chlorophyll pigment concentrations. An empirical algorithm of the form: log (chlorophyll pigments) 0.92-0.46 Delta2 log R0sea(555) yields an estimate of chlorophyll pigment concentrations within a mean deltaC / C of 23%.

The western Gulf of St. Lawrence (GSL) is characterized by high, persistent phytoplankton production and functions as the principal supplier of phytoplankton biomass for the central and eastern Gulf. The main objective of this study was to report on the evolution of a wind-induced phytoplankton bloom in this region. We used Coastal Zone Color Scanner images taken on 20, 22, 28, and 30 August 1980 to calculate phytoplankton pigment concentration, sea surface temperature and water reflectance fields. We coupled the satellite information with storm track, wind, air temperature, and bright sunshine data. A strong storm blew over the Gulf between 15 and 17 August, triggering upwelling and mixing processes that presumably made high nutrient concentrations available in the euphotic layer. High atmospheric pressure and southwesterly winds between 18 and 25 August allowed air and water temperatures to rise, stabilizing the water column and stimulating phytoplankton growth. A northern storm between 25 and 27 August associated with clear weather and low temperatures between 28 and 30 August, coinciding with the bloom decline, Water-normalized reflectance values suggested that the estuarine region was characterized by diatoms, the western-central GSL by a mixed composition of diatoms/small flagellates/coccolithophorids, and the eastern-central region by coccolithophorids and small flagellates. These blooms may be critical for fish recruitment. Cooling and warming of the water column by meteorological events seem to be intermittent but frequent at this time of year, The resulting nutrient input may support phytoplankton blooms of intensities similar to or higher than those recorded during spring in the western region of the Gulf.

Describes a system to receive, archive and process NOAA AVHRR data into useful products. These include sea surface temperature, sediment concentration and coccolithophore bloom maps. Of four main components: 1) image acquisition; 2) archival, catalog and quicklooks production; 3) image analysis and products generation; 4) database searches and quicklooks visualization. Ultimately, this information will be used to monitor the St. Lawrence Gulf and Hudson Bay ecosystems and define the relations between physical and biological processes

An analysis of ice drift from consecutive Landsat multispectral scanner images of the same area taken at 24‐h interval allowed the calculation of the surface circulation using a dynamical approach. Comparison between calculated and measured values shows that this method leads to a good approximation of the surface circulation in a region where ice floes are free drifting. On the other hand, the sole use of the floe drift over time to evaluate the currents leads to results that are far from the measured values. Tests made using various air and ice drag coefficients, and wind speeds and directions for different drift distances show that the error associated with these parameters is small. Although the values obtained using the numerical data involved considerably more effort and expense, the results were not significantly better than those found using photographic products. A good approximation of the surface circulation can thus be made using a simple digitization of the floe positions on photographic products. Application of the methodology to a set of four image pairs led to the recognition of two modes of circulation in southeastern Hudson Bay in spring 1985. This method can thus become a useful tool for rapid evaluations of surface currents in ice‐covered areas that can hardly be sampled otherwise.

An intercomparison of three different types of current meter was performed in an Arctic environment where wave action was absent, permitting the evaluation of the instruments under natural conditions of weak currents and cold water. The instruments were an Aanderaa RCMS4S, an Inter Ocean S4 and an EG&G-Neil Brown Smart Acoustic Current Meter (SACM). The S4 and the SACM both showed their ability to measure very small currents as opposed to the RCM4S which is limited by a mechanical rotor threshold. The agreement of the direction was better between the RCM4S and the SACM than between the RCM4S and the S4. Due to the misalignment of the Aanderaa vane in very weak currents, direction differences between the instruments of either pair can, however, reach 180°. The misalignment also shields the Aanderaa rotor leading to underestimation of current speed. The threshold for a good speed reading for the Aanderaa can be put conservatively at 5 cm s−1. Above this value, the RCM4S over-responded compared to both the S4 and the SACM. The source of that problem seems to be related to different calibrations of the instruments. Finally a power spectrum analysis showed that the RCM4S, when not influenced by wave action, can produce a measure of the energy as good as that of a vector averaging instrument.

The lateral stratification and momentum balance in the lower Saint Lawrence estuary (LSLE) were investigated over a period of six days from current, temperature, and salinity measurements taken in 1979 at the Matane transect. Asymptotic singular decomposition analysis was used to show that the spatial variability of hydrodynamic parameters at that cross-section was more pronounced than their temporal or tidal variability. Classification of the section in the lateral circulation/stratification diagram revealed that the LSLE is one of the most laterally-stratified estuaries examined in the world. Estimates of various acceleration terms in the lateral dynamic balance equation showed that, when averaged over many tidal cycles, the motion can be considered as being quasigeostrophic to a first approximation, with contributions of the same order of magnitude from the baroclinic and the barotropic pressure gradients. Convection accelerations were found to be important only near the north shore, where strong cross-channel currents were recorded, whilst local and centrifugal accelerations were found to be of secondary importance.