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They also pointed out that ''the largest
d
14
C excursion was a 190
decrease
termination. This excursion accompanied a 40 ppm rise in atmospheric CO
2
.''
Stott and Timmerman (2011) concluded that there must be a reservoir of
14
C-depleted water in the oceans which displaces
%
14
C-rich water. They noted that
recent research has shown that ''
active submarine volcanic arcs in the Pacific
and hydrothermal vents in the northeastern and tropical eastern Pacific have
documented CO
2
-rich fluids venting at intermediate water depths (
1,000m).''
Although estimates of the CO
2
flux at these sites are sparse, recent data indicate
that submarine vents in the Pacific may represent a greater source of carbon to the
global carbon budget than previously estimated. Carbon dioxide can exist in liquid
state at surprisingly high temperatures if the pressure is high enough. The critical
temperature of CO
2
is 31.1
C at 1,070 psi. Stott and Timmerman (2011) drew a
phase diagram for CO
2
in which they replaced pressure by depth in the ocean
(100m
160 psi). Carbon dioxide can exist as a hydrate or as liquid CO
2
at su-
cient depth (see
Figure 10.16
). The current estimate for temperature vs. depth is
shown in
Figure 10.16
. It is hypothesized that the cooling that occurred during
the LGM produced a temperature profile vs. depth similar to that shown in
higher levels by ''several hundred meters''. It is proposed that this CO
2
was
depleted in
14
C and, as the oceans warmed after the LGM, this water became an
important source of CO
2
emitted to the atmosphere.
It is still not clear to this writer exactly how various levels in the ocean
contribute to the rise and fall of CO
2
in glacial-interglacial cycles within the
...
Figure 10.16. Phase diagram for CO
2
as a function of temperature and pressure showing how
cooling during glaciations would shift the depth of hydrate stability upward (Stott and
Timmerman, 2011).
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