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Investigating historical transmissometer data collected globally to analyze beam attenuation values and estimate particulate organic carbon (POC) levels. Comparison with satellite backscatter data. Future plans include expanding data collection and refining algorithms for POC prediction.
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Prospects for Using Historical Transmissometer Data in Large-Scale Assessment of Particular Organic Carbon A.V. Mishonov, W.D. Gardner, & M.J. Richardson Department of Oceanography, Texas A & M University, College Station, TX, USA, 77843.
Data Set • Transmissometer data have been collected using instruments provided by our group over the last decade in collaboration with WOCE, JGOFS, and other large-scale hydrographic programs. • These data include basin-wide transects in the North and South Atlantic, North and South Pacific, Indian, and Southern Oceans. • We have proposed to analyze these data and convert the beam attenuation values to POC using the beam attenuation:POC relationships derived by our group during JGOFS Process studies.
Approach • Stramski et al. (1999, Science, 285: 239-242) have introduced algorithms to estimate POC from satellite backscatter data for the Southern Ocean for both surface values and euphotic zone integrations. • In a similar manner, our basin-wide data will be compared with satellite backscattering data on appropriate seasonal and space scales to establish region-specific algorithms. • A compilation of historic hydrographic/optical data has been compared by season with recent satellite data by Mishonov et al. (1999, IUGG-99, Vol. B., p. 242) and the results further validate our proposed global synthesis of POC in Case I waters (non-coastal) using satellite-derived data.
Dominant Wavelength Secchi Disk Calculated by regression Sep’98 Chlorophyll-a Forele-Ule Scale Data from Comparison of SeaWiFS & in-situ Sampling Data: 37th cruise of RV Academician Vernadsky,Aug - Sep 1988 SeaWiFS chlorophyll Sep’98
Dominant Wavelength Secchi Disk Chlorophyll-a SeaWiFS chlorophyll Forele-Ule Scale Data from Feb’98 Feb’98 Comparison of SeaWiFS & in-situ Sampling Data: 41st cruise ofRV Academician Vernadsky,Feb - May 1990
Initial Data Set • 15 cruises from February 1992 till June 1997; • 2027 Stations in Pacific, Indian and Atlantic oceans; • 1817 Transmissometer Casts; • Accompanied hydrological data on Temperature, Salinity and Dissolved Oxygen; • More data will be added from JGOFS, SAVE, WOCE, etc. legs.
Loaded Not loaded Station Coverage: WOCE, JGOFS & other data
Transmissometer Data Set Monthly Distribution
Pacific Ocean SectionTh.Thompson, Jul-Aug.93, p14n line Beam Attenuation South North Depth, m Distance, nm
Data from Pacific Ocean SectionTh.Thompson, Jul-Aug.93, p14n line Upper 500 meters Stations Position S, p.s.u. Temperature AVHRR SST July 1993 Salinity t, °C
Data from Pacific Ocean SectionTh.Thompson, Jul-Aug.93, p14n line Upper 500 meters Stations Position C m-1 Density SeaWiFS CHL July 1998 Beam Attenuation Kg/m3
Indian Ocean Section Knorr, Feb. 95, i09s line S N Stations Position Depth, m Beam Attenuation Distance, nm
Data from Indian Ocean Section Knorr, Feb. 95, i09s line Upper 500 meters North Stations Position Temperature Salinity AVHRR SST Feb 1995 t, °C S, p.s.u.
Data from Indian Ocean Section Knorr, Feb. 95, i09s line Upper 500 meters North Stations Position Density Beam Attenuation SeaWiFS CHL Feb, 1998 C m-1 Kg/m3
Future plans: 1 • Transmissometer database: • Process 17 WOCE cruises of transmissometer data; • Add processed transmissometer & POC data from 19 JGOFS cruises; • Add processed transmissometer data from other basin-scale cruises where we have data (9+). • Beam attenuation / POC relationship: • Use algorithms developed during JGOFS, NABE, EqPAC, Indian Ocean and Southern Ocean expeditions;
Future plans: 2 • Compile SeaWiFS back-scatter data for comparable times of POC + Beam attenuation measurements; • Refine algorithms for predicting POC from SeaWiFS data; • Examine hydrography of each area: • Mixed layer depth; • Subsurface maxima. • Correlate POC standing stock by ocean basin & season; • Analyse data in context of JGOFS Synthesis & Modelling Program.