Wm. Balch et al., Optical backscattering in the Arabian Sea - continuous underway measurements of particulate inorganic and organic carbon, DEEP-SEA I, 48(11), 2001, pp. 2423-2452
Citations number
82
Categorie Soggetti
Aquatic Sciences","Earth Sciences
Journal title
DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS
Continuous surface measurements of temperature, salinity, fluorescence and
optical backscattering were made during R/V Thompson cruise no. TN053 in th
e northern Arabian Sea ("Bio-Optical cruise"; October-November, 1995). The
cruise covered the early NE monsoon period. Optical measurements involved a
lternate estimates of total backscattering and acidified backscattering app
roximately every 1.5-2min (measured after addition of a weak acid to dissol
ve calcium carbonate). The difference between total and acidified backscatt
ering equals "acid-labile backscattering". Total and acid-labile backscatte
ring were converted to the concentration of particulate organic carbon (POC
) and particulate inorganic carbon (PIC; calcium carbonate), respectively,
and discrete samples taken along the cruise track were used for calibration
. Backscattering data were frequently coherent with temperature, salinity,
and density variability. Acid-labile backscattering values revealed that ca
lcium carbonate accounted for 10-40% of the total optical backscattering in
the region, and the semi-continuous records demonstrated distinct patches
of coccolith-rich water. The northern Arabian Sea had the highest acid-labi
le backscattering. Results suggest that PIC: POC ratios can vary over about
four orders of magnitude. Highest surface values of PIC: POC approached on
e in several places. We also report qualitative observations of phytoplankt
on community structure made aboard ship, on fresh samples. (C) 2001 Elsevie
r Science Ltd. All rights reserved.