Marine research at CNR
Figure 4: NORBAL 1, Transect 58-24, MEDOC area (150 m-bottom). (A) θ, (B) S, (C) O2 , (D) ν. Cyclonic circulation schematized atop each figure. The left side of each section corresponds to the northernmost part of the transect.
3.3
Surface hydrography, dy- (Figure 7D-7F) follows the density pattern namics, nutrients and (Figure 7C), with low concentrations to the south (DIN = 0.02-0.80 µmol·dm−3 , PO4 chlorophyll −3
The upper 150 m situation hydrography in Figure 7A,7B,7C (NORBAL 1 Transect 58-24) shows that colder and saltier waters found in the north are associated to the MEDOC isopycnal doming. The isoline uplifting observed between stations 28 and 24 to the south (Figure 7A-7C) is associated with warmer and fresher waters, with values close to those of the Modified Atlantic Water (MAW) (13.8714.85°C, 37.52-38.18 psu) found south of the NBF. The transect thus intersects the NBF, whose northern limit is between station 38 and 28. The nutrient distribution
= 0.03-0.08 µmol·dm , SiOH4 = 1.082.15 µmol·dm−3 ) and high concentrations to the north, especially in nitrogen and silicates (DIN = 1.86-4.31 µmol·dm−3 , PO4 = 0.09-0.10 µmol·dm−3 , SiOH4 = 3.254.85 µmol·dm−3 ), the latter also probably linked to both vertical and horizontal transport of Rhone river waters (stas. 58, 59). The nutricline is only 50 m deep to the north and reaches the surface at sta. 40, confirmining recent convective events and suggesting that the biomass (chl, Figure 7G) has not entirely used up the upwelled nutrients. The surface chl bloom (stas. 5838) in the upper 60 m reaches the nutri-
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