EOS, Transactions, AGU, 1999 Fall Meeting,
Vol. 80, No. 46, November 16, 1999, page F9
Modeling
Glacial and Meltwater Global Ocean Conveyor: The Assessment of Millennial-Scale
Bipolar Ocean Seesaw
(1) Earth System Science Center,
Pennsylvania State University, University Park, PA 16802-2711
The millennial--scale
asynchrony of Antarctic and Greenland climate records during the last glacial
period (Blunier et al., 1998) implies that the global climate system acts as
a bipolar seesaw driven by either high-latitudinal, and/or near--equatorial
sea-surface perturbations (Broecker, 1998).
To address the question whether the ocean thermohaline conveyor might
be the major mechanism controlling the bipolar seesaw, we simulated both generic
Heinrich and Dansgaard-Oeschger scenarios (Seidov and Maslin, 1999). On the
basis of these generic meltwater scenarios, we argue that a
simple comeback--kid oscillations of deep-ocean conveyor might be sufficient
to cause and sustain the bipolar seesaw. The basic mechanism is the toggling
between North Atlantic overturning modes causing ocean heat rebounds. It is
emphasized that the warming or cooling of the alternate hemispheric oceans is
due to deepwater circulation rather than change of the surface currents. Since
the centuries are required to warm the respective high latitudinal waters due
to the deepwater-driven oscillating system, the observed climate lead and lags
between the Hemispheres can be explained by the variability of the meridional
overturning and by the corresponding change in the oceanic heat transport.
Accordingly, global climate works like a deepwater-driven pendulum which
is controlled by pushing in deep convection sites.
