Publication Date:
2022-05-25
Description:
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August 1995
Description:
Data from fifteen globally distributed, modern, high resolution, hydrographic
oceanic transects are combined in an inverse calculation using large scale box models.
The models provide estimates of the global meridional heat and freshwater budgets
and are used to examine the sensitivity of the global circulation, both inter and
intra-basin exchange rates, to a variety of external constraints provided by estimates
of Ekman, boundary current and throughflow transports.
A solution is found which is consistent with both the model physics and the
global data set, despite a twenty five year time span and a lack of seasonal consistency
among the data. The overall pattern of the global circulation suggested by the models
is similar to that proposed in previously published local studies and regional reviews.
However, significant qualitative and quantitative differences exist. These differences
are due both to the model definition and to the global nature of the data set.
The picture of the global circulation which emerges from the models IS a
complex, turbulent flow. When integrated across ocean basins not one, but two
major cells emerge. The first connects an Atlantic overturning cell (estimated at
18± 4x 109 kg s- 1) to the Southern Ocean where the Antarctic Circumpolar Current
carries lower deep waters to the Indian and Pacific basins where they are converted to
upper deep and intermediate waters before returning to the Atlantic. The second cell
connects the Pacific and Indian Basins to the north and south of Australia. In t his
cell deep waters pass into the Pacific and return within the Indian Basin as intermediate
waters after passing through the Indonesian Passages. The two cells are found
to be independent of one another, i.e. within the models, the Indonesian Passages do
not represent a significant element in a net global circulation.
While there is ample evidence of westward flow around the southern tip of
South Africa which would support a "warm" water path scenario, the variability
of flow in this region, rich with eddies makes hydrography a poor estimator of the relative strengths of the controversial "warm" and "cold" water paths. All existing
estimates of Indonesian Passage throughflow, including the smallest (O x 106 m3 s-1)
and the largest (20 x 106 m3 s-1), are consistent with the model constraints. When
the Pacific- Indian throughflow is not constrained, the model produces an estimate of
11 ± 14x 109 kg s-1.
The model heat flux estimates are both significantly different from zero and
quite robust to changes in initial assumptions, with the exception of the choice of wind
field. Although in this work it was not possible to compute freshwater fluxes which
were significantly different from zero, future inclusion of salinity anomaly constraints
along with terms describing vertical diffusion may yet make it possible to compute
significant freshwater :flux estimates from hydrography.
Description:
This research was partially funded by a NASA Global Change Fellowship and
was also supported by NASA under contract NAGW-1048 and NSF under contract
OCE-9205942.
Keywords:
Ocean circulation
;
Atmospheric circulation
;
Ocean-atmosphere interaction
;
Thomas G. Thompson (Ship) Cruise
;
Moana Wave (Ship) Cruise
;
Atlantis II (Ship : 1963-) Cruise AII109
;
Atlantis II (Ship : 1963-) Cruise AII93
;
Charles Darwin (Ship) Cruise
;
Oceanus (Ship : 1975-) Cruise OC133
;
Oceanus (Ship : 1975-) Cruise OC338
;
Knorr (Ship : 1970-) Cruise
;
Melville (Ship) Cruise
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
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