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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.

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.

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.

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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