Glacial Water Mass Geometry and the
Distribution of d
13 C of
S
CO
2 in the
Western Atlantic
William Curry
Delia Oppo
Department of Geology and Geophysics
Woods Hole Oceanographic Institution

Fate of Fossil Fuel CO
2 in the Ocean
Shackleton (1977)

M12392
Atlantic d
13 C
Glacial = -1.2 ‰ PDB
Shackleton (1977)

Y71-6-12MG
Pacific d
13 C
Same as Atlantic
During Glacial
Shackleton (1977)

Conservative Mixing
NADW High Salinity
– High d
13 C
AABW Low Salinity – Low d
13 C

NADW
GEOSECS

NADW
Kroopnick (1985)

Benthic Foraminifera
Cibicidoides sp.
Cibicides sp.
Planulina sp.
d
13 C of
S
CO
2
~ d
13 C of CaCO
3
Data sources:
Duplessy et al., 1984
Curry and Lohmann, 1990
Mackensen et al., 1993
McCorkle and Keigwin, 1994

AAIW
UCPDW
NADW
LCPDW
South Atlantic
Water Masses

Sedimentation Rates:
~ 10 cm kyr -1 above 1500 m
~ 5 cm kyr -1 below 2000 m

Cibidicoides at Brazil Margin
GNAIW
NADW
Curry and Oppo (in press)

North versus South Atlantic
GNAIW
Curry and Oppo (in press)

Core locations
New Brazil Margin Cores
(Curry and Oppo)
New Blake Ridge Cores
(Keigwin)
Curry and Oppo (in press)

Curry and Oppo (in press)

Curry and Oppo (in press)

Curry and Oppo (in press)

Curry and Oppo (in press)

North versus South Atlantic
GNAIW
Curry and Oppo (in press)

Vertical Mixing Along the MAR
Mauritzen et al. (2002)

North versus South Atlantic
GNAIW
Curry and Oppo (in press)

Summary
• Carbon isotope tracers show the presence of three water masses a reduced volume and shoaling of NADW – GNAIW.
•GNAIW southward penetration to 26º S. Intermediate water mass northward penetration unconstrained by carbon isotopes.
• Bathymetric and meridional gradients in d
13 C much larger because of changes in end member water mass properties.
• Bathymetric gradients in d
13 C imply that lateral advection remained strong with respect to expected strong vertical mixing.

What ’ s in the d
18 O Data?

North versus South Atlantic
GNAIW
Curry and Oppo (in press)

30 ºS to 30 ºN
D
T = 4 ºC

d
18 O gradient at Constant Density
0.6 permil

Global SSS and E-P distributions
Source: HydroBase2 Source: R.Schmitt,WHOI
Sea surface salinity distributions are determined in large part by E-P patterns

Large Scale Ocean Circulation

Vema Channel
Curry and Lohmann (1982)

Glacial Southern Ocean d
13 C slightly higher than
Atlantic and Pacific
(-0.9
‰ > -1.2‰ PDB)
Shackleton (1977)

Curry and Lohmann (1982)

Bathymetric
Changes in
Dd
13 C –
Decreased NADW
Curry and Lohmann (1982)