Glacial Water Mass Geometry and the Distribution of d 13 C of S CO 2 in the Western Atlantic

Glacial Water Mass Geometry and the Glacial Water Mass Geometry and the Distribution of Distribution of 1313C of C of COCO22 in the in the

Western AtlanticWestern Atlantic

William Curry

Delia Oppo

Department of Geology and Geophysics

Woods Hole Oceanographic Institution

Shackleton (1977)

Fate of Fossil Fuel COFate of Fossil Fuel CO22 in the Ocean in the Ocean

M12392

Atlantic 13C

Glacial = -1.2 ‰ PDB

Shackleton (1977)

Y71-6-12MGY71-6-12MG

Pacific Pacific 1313CC

Same as AtlanticSame as Atlantic

During GlacialDuring Glacial

Shackleton (1977)

NADW High Salinity – High 13C

AABW Low Salinity – Low 13C

Conservative MixingConservative Mixing

NADW

GEOSECS

NADW

Kroopnick (1985)

Benthic ForaminiferaBenthic Foraminifera

13C of CO2 13C of CaCO3

Cibicidoides sp.Cibicides sp.Planulina sp.

Data sources:Duplessy et al., 1984

Curry and Lohmann, 1990Mackensen et al., 1993

McCorkle and Keigwin, 1994

AAIWAAIW

UCPDWUCPDW

LCPDWLCPDW

NADWNADW

South AtlanticWater Masses

Sedimentation Rates:

~ 10 cm kyr-1 above 1500 m

~ 5 cm kyr-1 below 2000 m

Cibidicoides at Brazil MarginCibidicoides at Brazil Margin

Curry and Oppo (in press)

NADW

GNAIW

North versus South AtlanticNorth versus South Atlantic

Curry and Oppo (in press)

GNAIWGNAIW

Core locationsCore 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 AtlanticNorth versus South Atlantic

Curry and Oppo (in press)

GNAIWGNAIW

Mauritzen et al. (2002)

Vertical Mixing Along the MARVertical Mixing Along the MAR

North versus South AtlanticNorth versus South Atlantic

Curry and Oppo (in press)

GNAIWGNAIW

SummarySummary

• 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 13C much larger because of changes in end member water mass properties.

• Bathymetric gradients in 13C imply that lateral advection remained strong with respect to expected strong vertical mixing.

What’s in the What’s in the 1818O Data?O Data?

North versus South AtlanticNorth versus South Atlantic

Curry and Oppo (in press)

GNAIWGNAIW

30 ºS to 30 ºN

T = 4 ºC

1818O gradient at Constant DensityO gradient at Constant Density

0.6 permil

Sea surface salinity distributions are determined in large part by E-P patterns

Global SSS and E-P distributions

Source: R.Schmitt,WHOISource: HydroBase2

Large Scale Ocean CirculationLarge Scale Ocean Circulation

Vema ChannelVema Channel

Curry and Lohmann (1982)

Shackleton (1977)

Glacial Southern Ocean

13C slightly higher than

Atlantic and Pacific

(-0.9‰ > -1.2‰ PDB)

Curry and Lohmann (1982)

Curry and Lohmann (1982)

Bathymetric

Changes in 13C –

Decreased NADW