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Towards a global survey of intense surface plankton blooms using MERIS MCI

Towards a global survey of intense surface plankton blooms using MERIS MCI. Jim Gower and Stephanie King, Institute of Ocean Sciences, Sidney, BC, Canada gowerj@pac.dfo-mpo.gc.ca Goncalves, Pedro, ESRIN/ESA, ITALY pedro-.goncalves@terradue.com October 2007 Sputnik-2007, Vladivostok.

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Towards a global survey of intense surface plankton blooms using MERIS MCI

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  1. Towards a global survey of intense surface plankton blooms using MERIS MCI Jim Gower and Stephanie King, Institute of Ocean Sciences, Sidney, BC, Canada gowerj@pac.dfo-mpo.gc.ca Goncalves, Pedro, ESRIN/ESA, ITALY pedro-.goncalves@terradue.com October 2007 Sputnik-2007, Vladivostok

  2. ESA’s MERIS imager • A European sensor with a Canadian heritage • Launched by European Space Agency (ESA) on Envisat in 2002 • Similar to NASA’s MODIS, but no thermal IR • 300 m resolution, but data usually available at reduced resolution (RR) at 1200 m. • New optical bands (620, 709, 761, 900nm) • 709 nm is a significant wavelength for chlorophyll pigment detection, hence red tides, vegetation.

  3. Definitions • Plankton blooms: only those with high surface chlorophyll concentrations “red tides.” • MERIS: MEdium Resolution Imaging Spectrometer • FLH: Chlorophyll fluorescence peak at 685 nm • MCI: Maximum Chlorophyll Index (peak at 705 nm)

  4. Peaks at 685 and 705 nm in spectra of water-leaving radiance • Fluorescence shows a peak at 685 nm for C<30 mg.m-3 FLH (MERIS bands: 665, 681, 709 nm) • Models show that an absorption/scattering peak near 705 nm should dominate for C>30 mg.m-3 • 705 nm peak is measured by MERIS 709 nm band • MCI (MERIS bands: 681, 709, 753 nm) indicates high surface chlorophyll

  5. Water reflectance model based on Morel et al., (1988), with saturating fluorescence at 685 nm, giving red-tide peak at 705 nm mg.m-3 of chlorophyll a

  6. Canada Vancouver Vancouver Island June 25 2003MERIS FR difference spectra for MCI targetsLevel 1Blooms in Saanich Inlet and among Gulf Islands Pacific Ocean (under cloud) U.S.A Data provided by the European Space Agency

  7. PAKISTAN IRAN Arabian Sea MERIS MCI RR 9 Feb 2006

  8. MERIS bloom hunt: 2 June 2005 Western Gulf of Mexico

  9. Model reflectance spectra for submerged vegetation showing MERIS band positions and high MCI with peak near 709 nm 0.15 m 0.4 m 1 m

  10. Floating Sargassum • First noted in Gulf of Mexico by MERIS MCI, May 2005 • MERIS spectrum confirms floating vegetation • Sargassum confirmed by surface observations • Houston press calls 2005 “High sargassum summer” • Tracked using the MODIS web product (FLH) archive from real time reception at USF (University of South Florida)

  11. Statistics from MODIS images (USF local reception) Number of days in each month in which Sargassum slicks were detected, west to east across the Gulf of Mexico and into the Gulf Stream.

  12. A “sargassum eddy” imaged off the east coast of the US on 4 October 2006.Top: true colourCentre: MCIBottom: ChlorophyllThe eddy began as a meander in the Gulf Stream and is now almost detached and rotating counter-clockwise.It is on the edge of the Sargasso Sea, which was once said to be thick with this weed

  13. High MCI on bright background suggests Antarctic bloom mixed with iceMERIS RR L14 March 2006Spectra are:clear water (green)ice/algae (red)difference (blue)

  14. Antarctic image shows streaks of high MCI, suggesting “super bloom” algae/ice mixture

  15. ESA’s new G-POD initiative(GRID – Processing On Demand) • Intensive processing for higher level data products • Global MCI accepted as one such product • Present prototype product is 2.5 arc min resolution (5 by 5 km), showing maximum MCI of 4 by 4, RR pixels • Time step is one day

  16. GRID processing on demand (G-POD) Data provided by the European Space Agency Example of a MERIS daily MCI global composite for 7 July 2006. Full coverage would consist of 14 day-time passes. Major bloom event in the Baltic at top centre.

  17. Part of MERIS daily MCI global composite for 7 July 2006. Major bloom event in the Baltic

  18. Segments of the daily global MCI composites from 29 June (060629) to 18 July 2006 (060718) showing a bright bloom (cyanobacteria) event in the southern Baltic

  19. Daily MCI composites An area of high MCI near the edge of the Chiang Jiang River plume as shown by the daily global MCI composites for 29 July and 1 and 4 August 2006

  20. Water-leaving radiance spectra from MERIS for 18 April 2007, for silt-laden water near the Fraser River mouth in the Strait of Georgia.Left, spectra with low associated chlorophyll concentration. Right, spectra with high chlorophyll. Absorption of backscattered radiance by chlorophyll at 665 and 681 nm leads to a high MCI signal.

  21. Daily MCI composites A bright bloom off Repulse Bay, Queensland, Australia as shown by the daily global MCI composites for 5, 21 and 27 August 2006. The event started some time after Aug. 5, peaking near Aug. 21 Bloom Coral reef Australia

  22. A bloom extending out of Repulse Bay, NE Australia, shown by the daily global MCI composite (left) for 21 August 2006, compared to higher resolution MERIS RR data (right), which includes spectra of level 1 (top-of-atmosphere) radiances from the bloom (left spectrum) and from an area of coral reef (right spectrum) MCI daily composite (G-POD) RR data (15 bands)

  23. Monthly MCI composites The bright bloom off Repulse Bay as shown by monthly MCI composites for July, August and September 2006. July 2006 August 2006 September 2006

  24. Monthly MCI composites Pelagic Sargassum faintly visible in the north-west Gulf of Mexico in the summer of 2006. Sargassum is less extensive and concentrated further north compared to 2005 July 2006 August 2006 September 2006

  25. A composite MCI image for February 2007 showing the Antarctic in polar stereographic projection shows the presence of high MCI close to the summer ice edge in some areas. Highest signals are in the south west Weddell Sea (upper left) where Smetacek et al., (Deep Sea Res., 39, 153, 1992) reported “superblooms” among ice. Black areas are land, ice or persistent cloud.

  26. South Atlantic Anomaly as observed with MERISCount of all single pixel MCI events in global composites for July, 2006 Data provided by the European Space Agency

  27. Cosmic ray hits on sensors at satellite altitude Satellites orbit below the van Allen radiation belts except over the South Atlantic, where the belts dip lower (South Atlantic Anomaly, SAA). Region moves west 0.3 degrees per year. Image from NASA’s SAA Detector on ROSAT, 1990-1999

  28. Conclusions • MERIS has great potential for bloom detection (709 nm band). The “false alarms” are also interesting (Sargassum, benthic vegetation (coral bleaching?), cosmic rays). • Blooms: Baltic event has been most intense and extensive, but several others detected • Why has no one ever reported Sargassum from space before? Why don’t we see it in the Sargasso Sea? • Sargassum and “Bloom in ice” seem to be two new “firsts” for satellite sensing by MERIS. • Sensors need to include a 709 nm band (Anatoly Gitelson would agree).

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