Publications

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2016
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).

2009
McClatchie, S, Charter R, Watson W, Lo N, Hill K, Manzano-Sarabia M, Goericke R, Collins C, Bjorkstedt E, Schwing FB, Bograd SJ, Kahru M, Mitchell BG, Koslow JA, Ralston S, Field J, Peterson WT, Emmett R, Gomez-Valdes J, Lavaniegos BE, Caxiola-Castro G, Rogers-Bennet L, Gottschalck J, Heureux ML, Xue Y, Munger L, Campbell G, Merkens K, Camacho D, Havron A, Douglas A, Hildebrand J.  2009.  The state of the California Current, Spring 2008-2009: Cold conditions drive regional differences in coastal production. California Cooperative Oceanic Fisheries Investigations Reports. 50:43-68. AbstractWebsite

This report describes the state of the California Current system (CCS) between the springs of 2008 and 2009 based on observations taken along the west coast of North America The dominant forcing on the CCS during this time period were La Nina-type conditions that prevailed from the summer of 2007 through early 2009, transitioning to neutral El Nino-Southern Oscillation conditions in the spring of 2009 The Pacific Decadal Oscillation index was negative during this time period and its values had not returned to normal by the spring of 2009 The general effects on the California Current system were stronger thin normal southward winds and upwelling as well as generally colder than normal SST and shallow nitraclines, however, there were repot-ill differences Off alp California sea surface temperatures did not respond to the La Nina conditions, however, concentrations of chlorophyll a (Chl a) were significantly above normal, probably due to the anomalously high upwelling off Baja during most of the year Off southern California there was no clear evidence of increased primary or secondary production, despite observations that previous La Nina conditions affected mixed layer depth, temperatures, nutrients, and nitracline depths In both central and northern California and Oregon, stronger than normal upwelling increased primary production and prevented potential spawning of sardine north of San Francisco In central California the midwater fish community resembled that of recent cool years, and cover by kelp was much reduced along the coast Off Oregon there was evidence of increased abundance of boreal copepods, although the neritic boreal species did not appear to extend as far south is central California Current predictions are for cooler conditions to change to El Nino conditions by the end of 2009, these are expected to last through the Northern Hemisphere wintet of 2009-10

2007
Kahru, M, Mitchell BG, Gille ST, Hewes CD, Holm-Hansen O.  2007.  Eddies enhance biological production in the Weddell-Scotia confluence of the southern ocean. Geophysical Research Letters. 34   10.1029/2007gl030430   AbstractWebsite

[1] Satellite data show that oceanic eddies generated in the Southern Antarctic Circumpolar Current Front ( SACCF) are associated with increased phytoplankton biomass. Cyclonic eddies with high chlorophyll a concentration ( Chl-a) retain phytoplankton within the eddy cores and increase the light available for photosynthesis in the upper mixed layer by limiting vertical mixing and lifting of the isopycnal surfaces. Anticyclonic eddies have low Chl- a in the core but increased Chl- a in the periphery. Cross- frontal mixing mediated by eddies transports nutrients ( e. g., Fe and Si) to the north and contributes to the increased Chl- a in the frontal zone. Interannual variations in the cyclonic eddy activity are positively correlated with variations in Chl- a during the spring bloom in regions of the Antarctic Circumpolar Current around South Georgia.

1999
Stramski, D, Reynolds RA, Kahru M, Mitchell BG.  1999.  Estimation of particulate organic carbon in the ocean from satellite remote sensing. Science. 285:239-242.   10.1126/science.285.5425.239   AbstractWebsite

Measurements from the Southern Ocean show that particulate organic carbon (POC) concentration is welt correlated with the optical backscattering by particles suspended in seawater. This relation, in conjunction with retrieval of the backscattering coefficient from remote-sensing reflectance, provides an algorithm for estimating surface POC from Satellite data of ocean color. Satellite imagery from SeaWiFS reveals the seasonal progression of POC, with a zonal band of elevated POC concentrations in December coinciding with the Antarctic Polar Front Zone. At that time, the POC pool within the top 100 meters of the entire Southern Ocean south of 40 degrees S exceeded 0.8 gigatons.