Abstract:
A new, global inversion is used to estimate the large scale oceanic circulation based on
the World Ocean Circulation Experiment and Java Australia Dynamic Experiment hydrographic
data. A linear inverse "box" model is used to combine consistently the transoceanic
sections. The circulation is geostrophic with an Ekman layer at the surface and oceanic
layers defined by neutral surfaces. Near-conservation of mass, salt and top-to-bottom silica
is required and, in addition, heat and the phosphate-oxygen combination (170[P04]+[02])
are conserved in layers that are not in contact with the surface. A globally-consistent solution
is obtained for a depth-independent adjustment to the thermal wind field, freshwater
flux divergenees, the Ekman transport, and the advective and diffusive dianeutral fluxes
between layers. A detailed error budget permits calculation of statistical uncertainties,
taking into account both the non-resolved part of the solution and the systematic errors
due to the temporal oceanic variability. The estimated water mass transports during the
WOCE period (1985-1996) are generally similar to previous published estimates. However,
important differences are found. In particular, the inflow of bottom waters into the
Pacific Ocean is smaller than in most previous estimates. Utilization of property anomaly
conservation constraints allows the estimation of significant dianeutral diffusivities in deep
layers, with a global average of 3 ± lcm2s- 1 north of 30°S. Dianeutral transfers indicate
that about 20 Sv of bottom water is formed in the Southern Ocean. Significant ocean-atmosphere
heat fluxes are found, with a global heating of 2.3 ± 0.4PW in the tropical
band and a corresponding cooling at high latitudes. The signature of a large-scale average
export production is found for nutrients in several temperate regions. Despite the large
uncertainties, the production magnitudes are consistent with independent measurements
from sediment traps and isotopic data. Net nutrient sources or sinks are found in several
regions, suggesting either transport of dissolved organic matter or a seasonal alias.
Oxygen indicates large exchanges with the atmosphere, with intake at high latitudes and
outgassing/remineralization at low latitudes.
