Export 5 results:
Sort by: Author Title Type [ Year  (Desc)]
Valente, A, Sathyendranath S, Brotas V, Groom S, Grant M, Taberner M, Antoine D, Arnone R, Balch WM, Barker K, Barlow R, Belanger S, Berthon JF, Besiktepe S, Brando V, Canuti E, Chavez F, Claustre H, Crout R, Frouin R, Garcia-Soto C, Gibb S, Gould R, Hooker S, Kahru M, Klein H, Kratzer S, Loisel H, McKee D, Mitchell BG, Moisan T, Muller-Karger F, O'Dowd L, Ondrusek M, Poulton AJ, Repecaud M, Smyth T, Sosik HM, Twardowski M, Voss K, Werdell J, Wernand M, Zibordi G.  2016.  A compilation of global bio-optical in situ data for ocean-colour satellite applications. Earth System Science Data. 8:235-252.   10.5194/essd-8-235-2016   AbstractWebsite

A 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).

Stukel, MR, Kahru M, Benitez-Nelson CR, Decima M, Goericke R, Landry MR, Ohman MD.  2015.  Using Lagrangian-based process studies to test satellite algorithms of vertical carbon flux in the eastern North Pacific Ocean. Journal of Geophysical Research-Oceans. 120:7208-7222.   10.1002/2015jc011264   AbstractWebsite

The biological carbon pump is responsible for the transport of similar to 5-20 Pg C yr(-1) from the surface into the deep ocean but its variability is poorly understood due to an incomplete mechanistic understanding of the complex underlying planktonic processes. In fact, algorithms designed to estimate carbon export from satellite products incorporate fundamentally different assumptions about the relationships between plankton biomass, productivity, and export efficiency. To test the alternate formulations of export efficiency in remote-sensing algorithms formulated by Dunne et al. (2005), Laws et al. (2011), Henson et al. (2011), and Siegel et al. (2014), we have compiled in situ measurements (temperature, chlorophyll, primary production, phytoplankton biomass and size structure, grazing rates, net chlorophyll change, and carbon export) made during Lagrangian process studies on seven cruises in the California Current Ecosystem and Costa Rica Dome. A food-web based approach formulated by Siegel et al. (2014) performs as well or better than other empirical formulations, while simultaneously providing reasonable estimates of protozoan and mesozooplankton grazing rates. By tuning the Siegel et al. (2014) algorithm to match in situ grazing rates more accurately, we also obtain better in situ carbon export measurements. Adequate representations of food-web relationships and grazing dynamics are therefore crucial to improving the accuracy of export predictions made from satellite-derived products. Nevertheless, considerable unexplained variance in export remains and must be explored before we can reliably use remote sensing products to assess the impact of climate change on biologically mediated carbon sequestration.

Saba, VS, Hyde KJW, Rebuck ND, Friedland KD, Hare JA, Kahru M, Fogarty MJ.  2015.  Physical associations to spring phytoplankton biomass interannual variability in the US Northeast Continental Shelf. Journal of Geophysical Research-Biogeosciences. 120:205-220.   10.1002/2014jg002770   AbstractWebsite

The continental shelf of the Northeast United States and Nova Scotia is a productive marine ecosystem that supports a robust biomass of living marine resources. Understanding marine ecosystem sensitivity to changes in the physical environment can start with the first-order response of phytoplankton (i.e., chlorophyll a), the base of the marine food web. However, the primary physical associations to the interannual variability of chlorophyll a in these waters are unclear. Here we used ocean color satellite measurements and identified the local and remote physical associations to interannual variability of spring surface chlorophyll a from 1998 to 2013. The highest interannual variability of chlorophyll a occurred in March and April on the northern flank of Georges Bank, the western Gulf of Maine, and Nantucket Shoals. Complex interactions between winter wind speed over the Shelf, local winter water levels, and the relative proportions of Atlantic versus Labrador Sea source waters entering the Gulf of Maine from the previous summer/fall were associated with the variability of March/April chlorophyll a in Georges Bank and the Gulf of Maine. Sea surface temperature and sea surface salinity were not robust correlates to spring chlorophyll a. Surface nitrate in the winter was not a robust correlate to chlorophyll a or the physical variables in every case suggesting that nitrate limitation may not be the primary constraint on the interannual variability of the spring bloom throughout all regions. Generalized linear models suggest that we can resolve 88% of March chlorophyll a interannual variability in Georges Bank using lagged physical data.

Kahru, M, Kudela R, Manzano-Sarabia M, Mitchell BG.  2009.  Trends in primary production in the California Current detected with satellite data. Journal of Geophysical Research-Oceans. 114   10.1029/2008jc004979   AbstractWebsite

Several ocean primary production algorithms using satellite data were evaluated on a large archive of net primary production (NPP) and chlorophyll-a (Chl-a) measurements collected by the California Cooperative Fisheries Investigations program in the California Current. The best algorithm matching in situ data was found by empirically adjusting the Behrenfeld-Falkowski Vertically Generalized Production Model. Satellite-derived time series of NPP were calculated for the California Current area. Significant increase in NPP and Chl-a annual peak levels, i.e., the "bloom magnitude,'' were found along the coasts of the California Current as well as other major eastern boundary currents for the period of modern ocean color data (1997-2007). The reasons for this increase are not clear but are associated with various environmental conditions.

Kahru, M, Savchuk OP, Elmgren R.  2007.  Satellite measurements of cyanobacterial bloom frequency in the Baltic Sea: interannual and spatial variability. Marine Ecology-Progress Series. 343:15-23.   10.3354/meps06943   AbstractWebsite

Owing to the potentially harmful character of nitrogen-fixing filamentous cyanobacterial blooms in the Baltic Sea, a capacity to predict their occurrence is of interest. We quantified the surface accumulations of cyanobacteria, mainly Nodularia spumigena, using ocean colour satellite data. The spatial and temporal frequency of the accumulations was mapped with an automated detection algorithm, using their high reflectance in the 670 or 555 nm bands. Coastal Zone Color Scanner (CZCS) data were used for a first period (1979 to 1984), and combined SeaWiFS and MODIS-Aqua data for a second period (1998 to 2006). The frequency of cyanobacterial accumulations (FCA) for each 1 km(2) pixel was calculated as the ratio of scenes with detected cyanobacteria to the number of valid cloud-free scenes in July-August. FCA varied greatly among years and the basins of the Baltic Sea. Mean FCA was 39% higher in the second period, but the increase was not statistically significant. The mean FCA for the whole Baltic was positively correlated with the residual phosphate (RP) concentration after the spring bloom in May-June. RP was a useful predictor of FCA in the coming summer, but could not predict the spatial pattern of the bloom. This was better explained by prevailing winds, with high FCA in the southwestern Baltic after northerly winds in July. It seems that, at the time of writing, useful FCA predictions can be made after the spring bloom, but only for the whole Baltic.