Responsible persons:

Kadija Oubelkheir (kadija@obs-vlfr.fr) and Hervé Claustre (claustre@obs-vlfr.fr)

Laboratoire de Physique et Chimie Marines, Quai de la Darse BP 08, 06238 Villefranche sur Mer - France

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Material and methods

Total attenuation and absorption coefficients were measured at 9 wavelengths using a WETLabs ac9 (412, 440, 488, 510, 532, 555, 630, 676, 715 nm). This ac9 was coupled with a 24-bottle Rosette and a Seabird CTD with a Seatech fluorimeter. The whole package was deployed in the 0-400 m (Mediterranean sea) or 0-100 m (Morocco upwelling) layer. Repeated profiles (every third hour) were conducted with this package during five days at DYF and MIO sites and 36 hours at UPW site, with a drop speed of 0.5 m.s^-1. A WETLabs M-PAK3 acquisition system was used to power the WETLabs instruments and to acquire data. After each profile, the data were downloaded onto a PC.

Ac9 was calibrated on board with optically-pure water using a water purification system (Millipore, A10). An alternative method was developed for this cruise to post-recalibrate data and correct for instrumental drift over time (Twardowski et al., 1999) by using 400 m seawater as a reference for Mediterranean sea. This method is based on the assumption that optical properties of Mediterranean waters at 400 m vary weakly, which was verified by several field observations. Correction for in situ temperature and salinity effects was applied using the algorithm of Pegau et al., 1997. Correction of the absorption coefficient for incomplete recovery of the scattered light in the ac9's a tube is made by subtracting the absorption coefficient at a reference wavelength (at 715 nm) (Zaneveld et al., 1994). In what follows, the terms a(l ) and c(l ) will designate the absorption and attenuation coefficients measured by the ac9 after subtraction of pure water coefficients.

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Data	DYF_up DYF_down  |  MIO_up MIO_down  |  ST_up ST_down  |   UPW_up UPW_down

Column 1: CTD
Column 2: Depth (m)
Column 3 - 11: Absorption coefficient (9 wavelengths) (m^-1)
Column 12 - 20: Attenuation coefficient (9 wavelengths) (m^-1)
Downcast (down) and Upcast (up)

 

dyf_u UP dyf_u_071 dyf_u_072 dyf_u_073 dyf_u_074 dyf_u_075 dyf_u_077 dyf_u_078 dyf_u_079 dyf_u_080 dyf_u_081 dyf_u_082 dyf_u_083 dyf_u_084 dyf_u_085 dyf_u_086 dyf_u_087 dyf_u_088 dyf_u_090 dyf_u_092 dyf_u_093 dyf_u_094 dyf_u_095 dyf_u_096 dyf_u_097 dyf_u_098 dyf_u_099 dyf_u_100 dyf_u_101 dyf_u_102 dyf_u_103 dyf_u_104 dyf_u_105   dyf_d DOWN dyf_d_071 dyf_d_072 dyf_d_073 dyf_d_074 dyf_d_075 dyf_d_077 dyf_d_078 dyf_d_079 dyf_d_080 dyf_d_081 dyf_d_082 dyf_d_083 dyf_d_084 dyf_d_085 dyf_d_086 dyf_d_087 dyf_d_088 dyf_d_090 dyf_d_092 dyf_d_093 dyf_d_094 dyf_d_095 dyf_d_096 dyf_d_097 dyf_d_098 dyf_d_099 dyf_d_100 dyf_d_101 dyf_d_102 dyf_d_103 dyf_d_104 dyf_d_105

MIO_U UP mio_u_027 mio_u_028 mio_u_029 mio_u_030 mio_u_031 mio_u_032 mio_u_033 mio_u_035 mio_u_037 mio_u_038 mio_u_039 mio_u_041 mio_u_043 mio_u_044 mio_u_045 mio_u_046 mio_u_047 mio_u_048 mio_u_049 mio_u_050 mio_u_051 mio_u_052 mio_u_053 mio_u_054 mio_u_055 mio_u_056 mio_u_057 mio_u_058 mio_u_060 mio_u_061   mio_d DOWN mio_d_027 mio_d_028 mio_d_029 mio_d_030 mio_d_031 mio_d_032 mio_d_033 mio_d_035 mio_d_037 mio_d_038 mio_d_039 mio_d_041 mio_d_043 mio_d_044 mio_d_045 mio_d_046 mio_d_047 mio_d_048 mio_d_049 mio_d_050 mio_d_051 mio_d_052 mio_d_053 mio_d_054 mio_d_055 mio_d_056 mio_d_057 mio_d_058 mio_d_060 mio_d_061

 

st_u_ UP st_u__011 st_u__013 st_u__014 st_u__019 st_u__022 st_u__023 st_u__025 st_u__026 st_u__064 st_u__067 st_u__068 st_u__069 st_u__070   st_d_ DOWN st_d__011 st_d__013 st_d__014 st_d__019 st_d__022 st_d__023 st_d__025 st_d__026 st_d__064 st_d__067 st_d__068 st_d__069 st_d__070

upw_u UP upw_u_002 upw_u_003 upw_u_004 upw_u_005 upw_u_006 upw_u_007 upw_u_008 upw_u_010   upw_d DOWN upw_d_002 upw_d_003 upw_d_004 upw_d_005 upw_d_006 upw_d_007 upw_d_008 upw_d_010

 

 

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References

 

Claustre H., F. Fell, K. Oubelkheir, L. Prieur, A. Sciandra, B. Gentili and M. Babin. 2000. Continuous monitoring of surface optical properties across a geostrophic front: Biogeochemical inferences. Limnology and Oceanography. 45: 309-321.

Pegau W. S., G. Deric and J. R. V. Zaneveld. 1997. Absorption and attenuation of visible and near-infrared light in water: dependence on temperature and salinity. Applied Optics. 36: 6035-6046.

Twardowski M. S., J. M. Sullivan, P. L. Donaghay and J. R. V. Zaneveld. 1999. Microscale quantification of the absorption by dissolved and particulate material in coastal waters with an ac-9. Journal of Atmospheric and Oceanic Technology. 16: 691-707.

Zaneveld J. R. V., J. C. Kitchen and C. M. Moore. 1994. The scattering error correction of reflecting-tube absorption meters. Proc. SPIE, Ocean Optics XII. 2258: 44-55.