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ArticleBiological structure and seasonality in the Japan/East Sea(Oceanography Society, 2006-09) Ashjian, Carin J. ; Arnone, Robert ; Davis, Cabell S. ; Jones, Burton ; Kahru, Mati ; Lee, Craig M. ; Mitchell, B. GregoryThe Japan/East Sea (JES) contains several oceanic regions separated by dynamic boundaries. These distinct regions, and the physical features that establish and maintain the boundaries between the regions, have significant impacts on its ocean biology. Until recently, most studies of the biology of the JES have focused on nearshore regions, with few detailed studies of the interior of the JES or the dynamic features that define the different regions. In addition, the classic sampling methods used in previous work have not allowed high-resolution studies of biological-physical interactions associated with key dynamic mesoscale frontal zones, quasi-synoptic surveys of water column and biological structure in three dimensions, or broad-scale description of the seasonal cycles in the different biogeographic regions of the JES.
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ArticleAn ocean-colour time series for use in climate studies: The experience of the ocean-colour climate change initiative (OC-CCI)(MDPI, 2019-10-03) Sathyendranath, Shubha ; Brewin, Robert J. W. ; Brockmann, Carsten ; Brotas, Vanda ; Calton, Ben ; Chuprin, Andrei ; Cipollini, Paolo ; Couto, André B. ; Dingle, James ; Doerffer, Roland ; Donlon, Craig ; Dowell, Mark ; Farman, Alex ; Grant, Michael ; Groom, Steven ; Horseman, Andrew ; Jackson, Thomas ; Krasemann, Hajo ; Lavender, Samantha ; Martinez-Vicente, Victor ; Mazeran, Constant ; Melin, Frederic ; Moore, Timothy S. ; Müller, Dagmar ; Regner, Peter ; Roy, Shovonlal ; Steele, Chris J. ; Steinmetz, François ; Swinton, John ; Taberner, Malcolm ; Thompson, Adam ; Valente, André ; Zühlke, Marco ; Brando, Vittorio ; Feng, Hui ; Feldman, Gene ; Franz, Bryan A. ; Frouin, Robert ; Gould, Richard ; Hooker, Stanford B. ; Kahru, Mati ; Kratzer, Susanne ; Mitchell, B. Greg ; Muller-Karger, Frank E. ; Sosik, Heidi M. ; Voss, Kenneth ; Werdell, Jeremy ; Platt, TrevorOcean colour is recognised as an Essential Climate Variable (ECV) by the Global Climate Observing System (GCOS); and spectrally-resolved water-leaving radiances (or remote-sensing reflectances) in the visible domain, and chlorophyll-a concentration are identified as required ECV products. Time series of the products at the global scale and at high spatial resolution, derived from ocean-colour data, are key to studying the dynamics of phytoplankton at seasonal and inter-annual scales; their role in marine biogeochemistry; the global carbon cycle; the modulation of how phytoplankton distribute solar-induced heat in the upper layers of the ocean; and the response of the marine ecosystem to climate variability and change. However, generating a long time series of these products from ocean-colour data is not a trivial task: algorithms that are best suited for climate studies have to be selected from a number that are available for atmospheric correction of the satellite signal and for retrieval of chlorophyll-a concentration; since satellites have a finite life span, data from multiple sensors have to be merged to create a single time series, and any uncorrected inter-sensor biases could introduce artefacts in the series, e.g., different sensors monitor radiances at different wavebands such that producing a consistent time series of reflectances is not straightforward. Another requirement is that the products have to be validated against in situ observations. Furthermore, the uncertainties in the products have to be quantified, ideally on a pixel-by-pixel basis, to facilitate applications and interpretations that are consistent with the quality of the data. This paper outlines an approach that was adopted for generating an ocean-colour time series for climate studies, using data from the MERIS (MEdium spectral Resolution Imaging Spectrometer) sensor of the European Space Agency; the SeaWiFS (Sea-viewing Wide-Field-of-view Sensor) and MODIS-Aqua (Moderate-resolution Imaging Spectroradiometer-Aqua) sensors from the National Aeronautics and Space Administration (USA); and VIIRS (Visible and Infrared Imaging Radiometer Suite) from the National Oceanic and Atmospheric Administration (USA). The time series now covers the period from late 1997 to end of 2018. To ensure that the products meet, as well as possible, the requirements of the user community, marine-ecosystem modellers, and remote-sensing scientists were consulted at the outset on their immediate and longer-term requirements as well as on their expectations of ocean-colour data for use in climate research. Taking the user requirements into account, a series of objective criteria were established, against which available algorithms for processing ocean-colour data were evaluated and ranked. The algorithms that performed best with respect to the climate user requirements were selected to process data from the satellite sensors. Remote-sensing reflectance data from MODIS-Aqua, MERIS, and VIIRS were band-shifted to match the wavebands of SeaWiFS. Overlapping data were used to correct for mean biases between sensors at every pixel. The remote-sensing reflectance data derived from the sensors were merged, and the selected in-water algorithm was applied to the merged data to generate maps of chlorophyll concentration, inherent optical properties at SeaWiFS wavelengths, and the diffuse attenuation coefficient at 490 nm. The merged products were validated against in situ observations. The uncertainties established on the basis of comparisons with in situ data were combined with an optical classification of the remote-sensing reflectance data using a fuzzy-logic approach, and were used to generate uncertainties (root mean square difference and bias) for each product at each pixel.
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ArticleA compilation of global bio-optical in situ data for ocean-colour satellite applications - version two(Copernicus Publications, 2019-07-15) Valente, André ; Sathyendranath, Shubha ; Brotas, Vanda ; Groom, Steven ; Grant, Michael ; Taberner, Malcolm ; Antoine, David ; Arnone, Robert ; Balch, William M. ; Barker, Kathryn ; Barlow, Ray ; Belanger, Simon ; Berthon, Jean-François ; Besiktepe, Sukru ; Borsheim, Yngve ; Bracher, Astrid ; Brando, Vittorio ; Canuti, Elisabetta ; Chavez, Francisco P. ; Cianca, Andrés ; Claustre, Hervé ; Clementson, Lesley ; Crout, Richard ; Frouin, Robert ; García-Soto, Carlos ; Gibb, Stuart W. ; Gould, Richard ; Hooker, Stanford B. ; Kahru, Mati ; Kampel, Milton ; Klein, Holger ; Kratzer, Susanne ; Kudela, Raphael M. ; Ledesma, Jesus ; Loisel, Hubert ; Matrai, Patricia A. ; McKee, David ; Mitchell, Brian G. ; Moisan, Tiffany ; Muller-Karger, Frank E. ; O'Dowd, Leonie ; Ondrusek, Michael ; Platt, Trevor ; Poulton, Alex J. ; Repecaud, Michel ; Schroeder, Thomas ; Smyth, Timothy ; Smythe-Wright, Denise ; Sosik, Heidi M. ; Twardowski, Michael ; Vellucci, Vincenzo ; Voss, Kenneth ; Werdell, Jeremy ; Wernand, Marcel ; Wright, Simon ; Zibordi, GiuseppeA global compilation of in situ data is useful to evaluate the quality of ocean-colour satellite data records. Here we describe the data compiled for the validation of the ocean-colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI). The data were acquired from several sources (including, inter alia, MOBY, BOUSSOLE, AERONET-OC, SeaBASS, NOMAD, MERMAID, AMT, ICES, HOT and GeP&CO) and span the period from 1997 to 2018. Observations of the following variables were compiled: spectral remote-sensing reflectances, concentrations of chlorophyll a, spectral inherent optical properties, spectral diffuse attenuation coefficients and total suspended matter. The data were from multi-project archives acquired via open internet services or from individual projects, acquired directly from data providers. Methodologies were implemented for homogenization, quality control and merging of all data. No changes were made to the original data, other than averaging of observations that were close in time and space, elimination of some points after quality control and conversion to a standard format. The final result is a merged table designed for validation of satellite-derived ocean-colour products and available in text format. Metadata of each in situ measurement (original source, cruise or experiment, principal investigator) was propagated throughout the work and made available in the final table. By making the metadata available, provenance is better documented, and it is also possible to analyse each set of data separately. This paper also describes the changes that were made to the compilation in relation to the previous version (Valente et al., 2016). The compiled data are available at https://doi.org/10.1594/PANGAEA.898188 (Valente et al., 2019).
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ArticleA compilation of global bio-optical in situ data for ocean-colour satellite applications(Copernicus Publications on behalf of the European Geosciences Union, 2016-06-03) Valente, André ; Sathyendranath, Shubha ; Brotas, Vanda ; Groom, Steven ; Grant, Michael ; Taberner, Malcolm ; Antoine, David ; Arnone, Robert ; Balch, William M. ; Barker, Kathryn ; Barlow, Ray ; Belanger, Simon ; Berthon, Jean-François ; Besiktepe, Sukru ; Brando, Vittorio ; Canuti, Elisabetta ; Chavez, Francisco P. ; Claustre, Hervé ; Crout, Richard ; Frouin, Robert ; García-Soto, Carlos ; Gibb, Stuart W. ; Gould, Richard ; Hooker, Stanford B. ; Kahru, Mati ; Klein, Holger ; Kratzer, Susanne ; Loisel, Hubert ; McKee, David ; Mitchell, Brian G. ; Moisan, Tiffany ; Muller-Karger, Frank E. ; O'Dowd, Leonie ; Ondrusek, Michael ; Poulton, Alex J. ; Repecaud, Michel ; Smyth, Timothy ; Sosik, Heidi M. ; Twardowski, Michael ; Voss, Kenneth ; Werdell, Jeremy ; Wernand, Marcel ; Zibordi, GiuseppeA compiled set of in situ data is important to evaluate the quality of ocean-colour satellite-data records. Here we describe the data compiled for the validation of the ocean-colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI). The data were acquired from several sources (MOBY, BOUSSOLE, AERONET-OC, SeaBASS, NOMAD, MERMAID, AMT, ICES, HOT, GeP&CO), span between 1997 and 2012, and have a global distribution. Observations of the following variables were compiled: spectral remote-sensing reflectances, concentrations of chlorophyll a, spectral inherent optical properties and spectral diffuse attenuation coefficients. The data were from multi-project archives acquired via the open internet services or from individual projects, acquired directly from data providers. Methodologies were implemented for homogenisation, quality control and merging of all data. No changes were made to the original data, other than averaging of observations that were close in time and space, elimination of some points after quality control and conversion to a standard format. The final result is a merged table designed for validation of satellite-derived ocean-colour products and available in text format. Metadata of each in situ measurement (original source, cruise or experiment, principal investigator) were preserved throughout the work and made available in the final table. Using all the data in a validation exercise increases the number of matchups and enhances the representativeness of different marine regimes. By making available the metadata, it is also possible to analyse each set of data separately. The compiled data are available at doi:10.1594/PANGAEA.854832 (Valente et al., 2015).
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ArticleNew approaches and technologies for observing harmful algal blooms(Oceanography Society, 2005-06) Babin, Marcel ; Cullen, John C. ; Roesler, Collin S. ; Donaghay, Percy L. ; Doucette, Gregory J. ; Kahru, Mati ; Lewis, Marlon R. ; Scholin, Christopher A. ; Sieracki, Michael E. ; Sosik, Heidi M.Harmful algal blooms (HABs) represent a diverse range of phenomena that universally share only two characteristics: they produce effects on ecosystems or food resources that humans perceive as harmful, and their progression is fundamentally a process of population dynamics under oceanographic control. Because of the complexity, scales, and transient nature of HABs, their monitoring and prediction requires rapid, intensive, extensive, and sustained observations at sea. These requirements cannot be met with traditional approaches that depend on ships for sampling and laboratories for chemical or biological analyses. Fortunately, new sensing technologies that operate autonomously in situ will allow, in the near future, the development of comprehensive observation strategies for timely detection of HABs. In turn, developments in modeling will support prediction of these phenomena, based directly on real-time measurements.
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ArticleSatellite detection of dinoflagellate blooms off California by UV reflectance ratios(University of California Press, 2021-06-09) Kahru, Mati ; Anderson, Clarissa ; Barton, Andrew D. ; Carter, Melissa L. ; Catlett, Dylan ; Send, Uwe ; Sosik, Heidi M. ; Weiss, Elliot L. ; Mitchell, B. GregoryAs harmful algae blooms are increasing in frequency and magnitude, one goal of a new generation of higher spectral resolution satellite missions is to improve the potential of satellite optical data to monitor these events. A satellite-based algorithm proposed over two decades ago was used for the first time to monitor the extent and temporal evolution of a massive bloom of the dinoflagellate Lingulodinium polyedra off Southern California during April and May 2020. The algorithm uses ultraviolet (UV) data that have only recently become available from the single ocean color sensor on the Japanese GCOM-C satellite. Dinoflagellates contain high concentrations of mycosporine-like amino acids and release colored dissolved organic matter, both of which absorb strongly in the UV part of the spectrum. Ratios <1 of remote sensing reflectance of the UV band at 380 nm to that of the blue band at 443 nm were used as an indicator of the dinoflagellate bloom. The satellite data indicated that an observed, long, and narrow nearshore band of elevated chlorophyll-a (Chl-a) concentrations, extending from northern Baja to Santa Monica Bay, was dominated by L. polyedra. In other high Chl-a regions, the ratios were >1, consistent with historical observations showing a sharp transition from dinoflagellate- to diatom-dominated waters in these areas. UV bands are thus potentially useful in the remote sensing of phytoplankton blooms but are currently available only from a single ocean color sensor. As several new satellites such as the NASA Plankton, Aerosol, Cloud, and marine Ecosystem mission will include UV bands, new algorithms using these bands are needed to enable better monitoring of blooms, especially potentially harmful algal blooms, across large spatiotemporal scales.
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ArticleAn inverse relationship between production and export efficiency in the Southern Ocean(John Wiley & Sons, 2013-04-23) Maiti, Kanchan ; Charette, Matthew A. ; Buesseler, Ken O. ; Kahru, MatiIn the past two decades, a number of studies have been carried out in the Southern Ocean to look at export production using drifting sediment traps and thorium-234 based measurements, which allows us to reexamine the validity of using the existing relationships between production, export efficiency, and temperature to derive satellite-based carbon export estimates in this region. Comparisons of in situ export rates with modeled rates indicate a two to fourfold overestimation of export production by existing models. Comprehensive analysis of in situ data indicates two major reasons for this difference: (i) in situ data indicate a trend of decreasing export efficiency with increasing production which is contrary to existing export models and (ii) the export efficiencies appear to be less sensitive to temperature in this region compared to the global estimates used in the existing models. The most important implication of these observations is that the simplest models of export, which predict increase in carbon flux with increasing surface productivity, may require additional parameters, different weighing of existing parameters, or separate algorithms for different oceanic regimes.