Variability in Optical Properties during LEO-15 Coastal Predictive Skill Experiment

1. Characterizing the Variability in the Inherent and Apparent Optical Properties During the LEO-15 1999 Coastal Predictive Skill Experiment Trisha Bergmann Oscar Schofield Joe Grzymski Mark Moline Taylor Newton Coastal Ocean Observation Lab Institute of Marine and Coastal Sciences Rutgers University

2. Objectives • review optical data from the past three years with special emphasis on the optics prior to and during an upwelling event • partition the IOPs into particulate and dissolved fractions • validate derived particulate and dissolved absorption spectra with discrete data

4. 6 Velocity (m/s) 0 Upwelling Wind Velocity & Direction -6 Nor’easter storm 175 210 Julian Day 32 25 Salinity (ppt) Temperature (C) 0 30 15 Depth (m) 175 210 175 210 Julian Day Julian Day 3 6 15 Diffuse Attenuation (m-1) 0 Chlorophyll (ug/L) Depth (m) 0 2 175 210 175 210 Julian Day Julian Day 15 LEO -15 Node Data Summer 1997 Data represents 30 days and 90 profiles

5. Diffuse Attenuation Coefficient Kd @ 440 nm (m-1) Mean absorption @ 440 nm (m-1) Temperature (oC) Depth (m) Pre-Upwelling July 6, 1998 onshore offshore .5m binned Depth (m) Initiation July 17, 1998 .5m binned Upwelling July 29, 1998 Depth (m) .5m binned Optics of an Upwelling Event

6. Temperature 22 Depth (m) Diffuse Attenuation Coefficient @ 440nm 1.2 10 Distance Offshore (km) Depth (m) Absorption @ 440 nm .15 2.5 Distance Offshore (km) Depth (m) Backscatter @ 440nm 0 .09 Distance Offshore (km) Depth (m) 0 Distance Offshore (km) Pre-Upwelling Conditions July 6, 1999 • vertically stratified • low optical loads (low AOP & IOPs) • inshore optics are dominated by estuarine outflow in surface waters and sediment resuspension in bottom waters

7. Attenuation @ 440nm (m-1) Absorption @ 440nm (m-1) Diffuse Attenuation @ 440nm (m-1) Depth (m) Range (km) Range (km) Range (km) Initiation of an Upwelling - July 30, 1999 Temperature (oC) Depth (m)

8. 99/07/16 absorption @ 555nm (m-1) onshore offshore AC-9 mean surface absorption (m-1) Wavelength (nm) Physical/Optical Coupling July 16, 1999 • Patterns in both the IOPs and AOPs in the coastal ocean mimic the local hydrography • Cold water advected from the north and a storm resuspension event result in high optical loads onshore • Onshore water masses are optically distinct both in the magnitude of their absorption/attenuation, but also in their spectral shapes (.5m binned data)

9. onshore surface Absorption (m-1) AC-9 adissolved aparticulate Wavelength (nm) offshore surface Absorption (m-1) AC-9 adissolved aparticulate Wavelength (nm) AC-9 vs discrete water samples • Onshore Surface Waters: aTOTAL is dominated by particulate absorption • Offshore and Bottom Waters: aTOTAL is dominated by dissolved organic absorption • Correlation between aTOTAL from the AC-9 and aTOTAL = aDOM + aPART has R2 = .77 and slope = 1.3 (excluding 555nm)

10. light source change light source change a CDOM (m-1) ln (a CDOM) (m-1) Absorption of CDOM a CDOM () = a CDOM (o) exp [-S ( - o)] S = 0.011  0.002 nm-1 Wavelength (nm)

11. AC-9 estimated Absorption (m-1) Wavelength (nm) Estimating a particulate absorption spectra “How far can we push the AC-9 data??” --Alan Weidemann July 29, 1999 3:30 AM • aTOTAL= aPART + aCDOM • aPART = aPH + aDET = summation of13 Gaussian curves(modified from Hoepffener & Sathyendranath) • aCDOM = estimated fromS = 0.011 • minimize residual between aTOTAL (AC-9) and aTOTAL (estimated) • sum series of Gaussian curves to calculate aPART

12. onshore surface Particulate Absorption (m-1) offshore surface measured estimated Particulate Absorption (m-1) Wavelength (nm) Preliminary Partition Results • 8 wavelengths as reference points reproduced general spectral shape and magnitude • the limitation of reference points will lead to a broadening and smoothing of spectra • agreement is poor where no AC-9 data is available • Improvements: more absorption data points and optimal placement of AC-9 channels, addition of detrital curve

13. 0 0.4 0.8 1.2 1.6 0 1 2 3 0 Upper mixed layer Upper mixed layer 4 4 Depth (m) 8 Depth (m) 12 8 offshore onshore 16 12 Carotenoid to Chlorophyll a Absorption ratio Photoacclimation • particulate absorption indicated photoacclimation • photoacclimation trends were most significant in turbid inshore waters • in offshore waters, with a deeper mixed layer depth, there were no trends in absorption ratios in the upper mixed layer

14. Conclusions • The spatial and temporal variability in the optical properties are coherent with the local hydrography. For example, upwelling leads to enhanced optical loads in coastal waters and tidal forcing can be significant (see the most excellent Dr. Weidemann up next). • Optical fingerprints of water masses can be used to track upwelling and other short term episodic events. The HyCODE Project will expand this work. • Spectral signatures of the upper water column are dominated by phytoplankton. Spectral signatures of the bottom water reflect variable contributions of phytoplankton, dissolved organic matter, and detrital material. • Partitioning of total absorption (AC-9) shows good correlation to discrete water samples. • In water data correlates well to satellite optics (see poster by Tozzi).

15. Where we're going • add detrital curve to deconvolution approach • begin to incorporate other optical data (e.g. scattering, backscatter) • assess the physical and optical length scales • data turnaround from ships to the web was within 48 hours in 1999 - next year go to near real time data availability for collaborating scientists to improve adaptive sampling and forecasting applications