R/V BILIM   LEG-3 Cruise
Duration of the cruise: 03 Oct.-24 Oct. 1999

As part of the September-October 1999 R/V Bilim Cruise, a 21-day long survey in the Black Sea, Marmara Sea, Aegean Sea and the Mediterranean Sea carried out during October 3-24, 1999. This survey aimed to develop regional algorithm for SeaWiFS sensor, obtain optical properties for Turkish Seas and comparison of the ecosystem of the four seas which have different characteristics.


The specific objectives were:
To conduct a mesoscale survey to determine bio-optical properties of the seas around Turkey
To collect nutrient, chlorophyll, and light profile data to characterize basic state of the ecosystem
To measure optical variables such as: light transparency, irradiance and absorption coefficient of water at PAR;
To collect biological data that effects optical properties of the sea.
To collect data on the atmospheric transparency to perform atmospheric correction of SeaWiFS data.

Stations visited during  LEG-3

(726 bytes) standard oceanographic stations
(727 bytes) stations with optical measurements

This cruise was performed with participation of the 3 groups: Institute of Marine Sciences of Middle East Technical University(IMS-METU), Marine Hydrophysical Institute (MHI)-Sevastopol and Scripps Institution of Oceanography (SIO). MHI and SIO scientists made atmospheric and oceanic optical measurement while the other measurements were done by IMS-METU group.

   The work was a combination of station and underway activities. During the cruise 53 oceanographic stations (25 optic) visited; Black Sea 23 (10 optic), Marmara Sea 3, Aegean 12 (3 optic), Mediterranean 15 (8 optic). The along track work consisted of acoustic measurements of the volume backscatter of the plankton throughout the water column and atmospheric transparency and water surface reflectance. The ship’s ADCP unit was used to make continuos measurements of the water current profile under the ship.

   The CTD data obtained using SBE 11plus also equipped with fluorometer and transmissivity sensors. The fluorometer readings were calibrated with spectrofluorometric measurements of the Chlorophyll-a. Rosette with niskin bottles were used in conjuction with the CTD to provide bottle sampling for nutrients and Chlorophyll-a. Nutrient measurements were performed on board with Technicon Autoanalyser using standard methods.

   The hull mounted 150kHz ADCP (Acoustic Doppler Current Profiler) from RD Instruments were used to measure the current velocities while ship was cruising between stations. Ship gyro were used to convert the velocities measured relative to the ship coordinate to the earth referenced coordinate. Ship location at each ensemble were fixed using Differential Global Positioning System (DGPS). Absolute current velocity computations obtained by subtracting ship velocities calculated from DGPS fixes

   The Chlorophyll-a (Chl-a) and Phaeopigments-a data were collected usually from 3 depths; surface, sub-surface maxima and below the subsurface maxima. Phytoplanton samples were also collected at these depths.

   The following measurements were also done as a complimantary to biological and chemical measurements done during leg 2: absorption by Phytoplankton, absorption by Detritus, absorption by Soluble Material, Bacterial Chlorophyll-e, total suspended sediment.

   Irradiance measurements (upward and downward) are carried out by LI-1800UW model spectroradiometer. Also LI-1000 model PARmeter was used onboard with parallel to this measurements. LI-18000 scans were made between 300-800 nm with 1nm interval for all 25 optic stations and for the depths (with 2 meter interval) until 1% light depth. For validation of this data air measurements are also made for both downward and upward irradiance. Cloud and seasurface conditions (which greatly affect measurements) are noted as well for later check on processed irradiance data.Rolling2.jpg (9384 bytes)

   The reflectance spectra measurements were carried out in daylight time for sun elevation more than 20o at stations and underway using spectral radiometer developed at MHI. The water transparency at nine narrow visible channel simultaneously (360, 421, 444, 464, 520, 556, 606, 660, and 670 nm) were measured from surface to 5 m. These measurements were done in parallel to reflectance measurements.

   The measurement of atmospheric transparency through the measurement of the Aerosol Optical Thichness and marine reflectance were done by R. Frouin from SIO for the cases for which cloud cover was <0.3

Cruise materials are available here.



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