Clues to Ocean History: a Brief Overview of Proxies
31
nificantly from those of the open ocean realm at
least in the upper and mid-depth water masses
(SACW, AAlW, UCDW). The deviations from the
Redfield fractionation, caused by air-sea
fractionation, remain constant within each water
mass, which means that the carbon isotope
changes toward upwelling areas are exclusively
determined by biological cycling.
3
N
2
0
(.0 0
()
H
0
o~oo 0'0 0
C')
~
0
•
0
•
0
0.5
1
Cd/Ca Ratios
The now classic tracer of phosphate content in
ocean waters is the Cd/Ca ratio, introduced by
Boyle (1988). The correlation between this ratio
and phosphate concentrations is quite well documented (Fig. 19). This correlation serves as a calibration in the same sense as calibrations for
microfossils sets. It also raises the analogous ques0 open ocean
•
upwelling area
a
1.5
2
2.5
3
Phosphate (J.Lmol / kg )
NA-Surface
a.
~ SO-~urface
... ... .................. 0.
" " NA~ AAlw"..
UC~~ UCDWupw
b
o o
0.5
1
1.5
2
2.5
3
Phosphate (J.Lmol / kg )
Fig. 18. o13Cl: C02 versus phosphate concentrations of the open ocean water samples and from the Namibia coastal
upwelling area, shown for (a) all samples and (b) selected samples representative for characteristic water masses in
the two different realms. Thin line indicates the bio-fractionational trend expected where no ocean-atmosphere
CO 2 exchange occur (Broecker and Maier-Reimer 1992). Related water masses are South Atlantic Central Water
(SACW), Antarctic Intermediate Water (AAIW), Upper Circumpolar Deep Water (UCDW), Lower Circumpolar Deep
Water (LCDW) and North Atlantic Deep Water (NADW). From Bickert and Wefer (1999).
31
nificantly from those of the open ocean realm at
least in the upper and mid-depth water masses
(SACW, AAlW, UCDW). The deviations from the
Redfield fractionation, caused by air-sea
fractionation, remain constant within each water
mass, which means that the carbon isotope
changes toward upwelling areas are exclusively
determined by biological cycling.
3
N
2
0
(.0 0
()
H
0
o~oo 0'0 0
C')
~
0
•
0
•
0
0.5
1
Cd/Ca Ratios
The now classic tracer of phosphate content in
ocean waters is the Cd/Ca ratio, introduced by
Boyle (1988). The correlation between this ratio
and phosphate concentrations is quite well documented (Fig. 19). This correlation serves as a calibration in the same sense as calibrations for
microfossils sets. It also raises the analogous ques0 open ocean
•
upwelling area
a
1.5
2
2.5
3
Phosphate (J.Lmol / kg )
NA-Surface
a.
~ SO-~urface
... ... .................. 0.
" " NA~ AAlw"..
UC~~ UCDWupw
b
o o
0.5
1
1.5
2
2.5
3
Phosphate (J.Lmol / kg )
Fig. 18. o13Cl: C02 versus phosphate concentrations of the open ocean water samples and from the Namibia coastal
upwelling area, shown for (a) all samples and (b) selected samples representative for characteristic water masses in
the two different realms. Thin line indicates the bio-fractionational trend expected where no ocean-atmosphere
CO 2 exchange occur (Broecker and Maier-Reimer 1992). Related water masses are South Atlantic Central Water
(SACW), Antarctic Intermediate Water (AAIW), Upper Circumpolar Deep Water (UCDW), Lower Circumpolar Deep
Water (LCDW) and North Atlantic Deep Water (NADW). From Bickert and Wefer (1999).