B. G. Mitchell

Global correlations between winds and ocean chlorophyll

Global time series of satellite‐derived winds and surface chlorophyll concentration n(Chl‐a) show patterns of coherent areas with either positive or negative correlations. The ncorrelation between Chl‐a and wind speed is generally negative in areas with deep nmixed layers and positive in areas with shallow mixed layers. These patterns are ninterpreted in terms of the main limiting factors that control phytoplankton growth, i.e., neither nutrients that control phytoplankton biomass in areas with positive correlation nbetween Chl‐a and wind speed or light that controls phytoplankton biomass in areas nwith negative correlation between Chl‐a and wind speed. More complex patterns are nobserved in the equatorial regions due to regional specificities in physical‐biological ninteractions. These correlation patterns can be used to map out the biogeochemical nprovinces of the world ocean in an objective way.

Estimating net community production in the Southern Ocean based on atmospheric potential oxygen and satellite ocean color data

(1) The seasonal cycle of atmospheric potential oxygen (APOO2 + 1.1 CO2) reflects three seasonally varying ocean processes: 1) thermal in- and outgassing, 2) mixed layer net community production (NCP) and 3) deep water ventilation. Previous studies have isolated the net biological seasonal signal (i.e., the sum of NCP and ventilation), after using air-sea heat flux data to estimate the thermal signal. In this study, we resolve all three components of the APO seasonal cycle using a methodology in which the ventilation signal is estimated based on atmospheric N2O data, the thermal signal is estimated based on heat flux or atmospheric Ar/N2 data, and the production signal is inferred as a residual. The isolation of the NCP signal in APO allows for direct comparison to estimates of NCP based on satellite ocean color data, after translating the latter into an atmospheric signal using an atmospheric transport model. When applied to ocean color data using algorithms specially adapted to the Southern Ocean and APO data at three southern monitoring sites, these two independent methods converge on a similar phase and amplitude of the seasonal NCP signal in APO and yield an estimate of annual mean NCP south of 50°S of 0.8-1.2 Pg C/yr, with corresponding annual mean NPP of � 3 Pg C/yr and a mean growing season f ratio of � 0.33. These results are supported by ocean biogeochemistry model simulations, in which air-sea O2 and N2O fluxes are resolved into component thermal, ventilation and (for O2) NCP contributions. Citation: Nevison, C. D., R. F. Keeling, M. Kahru, M. Manizza, B. G. Mitchell, and N. Cassar (2012), Estimating net community production in the Southern Ocean based on atmospheric potential oxygen and satellite ocean color data, Global Biogeochem. Cycles, 26, GB1020, doi:10.1029/2011GB004040.

A compilation of global bio-optical in situ data

André Valente, Shubha Sathyendranath , Vanda Brotas , Steve Groom, Michael Grant, Malcolm Taberner, David Antoine, Robert Arnone, William M. Balch, Kathryn Barker, Ray Barlow, 5 Simon Bélanger, Jean-François Berthon, Şükrü Beşiktepe, Yngve Borsheim, Astrid Bracher, Vittorio Brando, Elisabetta Canuti, Francisco Chavez, Andrés Cianca, Hervé Claustre, Lesley Clementson, Richard Crout, Robert Frouin, Carlos García-Soto, Stuart W. Gibb, Richard Gould, Stanford B. Hooker, Mati Kahru, Milton Kampel, Holger Klein, Susanne Kratzer, Raphael Kudela, Jesus Ledesma, Hubert Loisel, Patricia Matrai, David McKee, Brian G. 10 Mitchell, Tiffany Moisan, Frank Muller-Karger, Leonie ODowd, Michael Ondrusek, Trevor Platt, Alex J. Poulton, Michel Repecaud, Thomas Schroeder, Timothy Smyth, Denise SmytheWright, Heidi M. Sosik, Michael Twardowski, Vincenzo Vellucci, Kenneth Voss, Jeremy Werdell, Marcel Wernand, Simon Wright, Giuseppe Zibordi 15

A compilation of global bio-optical in situ data for ocean-colour satellite applications

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).