254 Paleoceanography - the Deep-Sea Record
300,---------------------------------------------------~
E a.
.s 250
N
o
()
200
o
ICE CORE DATA
40
80
Age (ky)
120
160
1.0
2.0
Fig. 9.8. Carlxm dioxide concentrations in the Vostok ice core from Antarctica (1. M. Bamola et a!. ,
1987, Nature 329: 408), compared with a productivity-related ol3C signal from the eastern tropical
Pacific (N. J. Shackleton et a!., 1983, Nature 306: 319). The signal plotted is the difference in ol3C
of a planktonic and a benthic species , which constitutes a proxy for the nutrient content in deep
waters. The time scale of the C02 record was adjusted using the deuterium record in the ice and the
0 18 0 record in the sediments. [W. H. Berger, V. S. Smetacek, O. Wefer, 1989, Productivity of the
ocean: present and past. Wiley-Interscience, Chichester]
distinguished American geologist Thomas C. Chamberlin (1843-1928) both put forward hypotheses about how the concentration of C02 could be changed through time.
The recent ice-core results prove that glacial C02 concentrations in air were lower
than interglacial ones by a factor of 1.5 (Fig. 9.8, upper curve). The C02 fluctuations
run parallel to the temperature at which the snow was deposited. Methane gas also
was measured; the fluctuations are similar to those of carbon dioxide.
The observed amplitude of C02 variation corresponds to a greenhouse effect of
between 1 and 2°C, according to recent climate models. Changes are very rapid,
making it very likely that the ocean is responsible: it has a large carbon reservoir
(roughly 60 times that of the present atmosphere), and it has a "memory" of only
about 1000 years (the average age of its deep water masses). Small changes in its
overall chemistry, leading to a small proportional change of carbon dissolved in the
ocean, can potentially have large effects on the atmosphere.
9.4.2 Paleoproductivity. There are a number of ways to affect the sharing of carbon
dioxide between ocean and atmosphere (see Sect. 3.7.1). For example, if dissolved
()
.0
300,---------------------------------------------------~
E a.
.s 250
N
o
()
200
o
ICE CORE DATA
40
80
Age (ky)
120
160
1.0
2.0
Fig. 9.8. Carlxm dioxide concentrations in the Vostok ice core from Antarctica (1. M. Bamola et a!. ,
1987, Nature 329: 408), compared with a productivity-related ol3C signal from the eastern tropical
Pacific (N. J. Shackleton et a!., 1983, Nature 306: 319). The signal plotted is the difference in ol3C
of a planktonic and a benthic species , which constitutes a proxy for the nutrient content in deep
waters. The time scale of the C02 record was adjusted using the deuterium record in the ice and the
0 18 0 record in the sediments. [W. H. Berger, V. S. Smetacek, O. Wefer, 1989, Productivity of the
ocean: present and past. Wiley-Interscience, Chichester]
distinguished American geologist Thomas C. Chamberlin (1843-1928) both put forward hypotheses about how the concentration of C02 could be changed through time.
The recent ice-core results prove that glacial C02 concentrations in air were lower
than interglacial ones by a factor of 1.5 (Fig. 9.8, upper curve). The C02 fluctuations
run parallel to the temperature at which the snow was deposited. Methane gas also
was measured; the fluctuations are similar to those of carbon dioxide.
The observed amplitude of C02 variation corresponds to a greenhouse effect of
between 1 and 2°C, according to recent climate models. Changes are very rapid,
making it very likely that the ocean is responsible: it has a large carbon reservoir
(roughly 60 times that of the present atmosphere), and it has a "memory" of only
about 1000 years (the average age of its deep water masses). Small changes in its
overall chemistry, leading to a small proportional change of carbon dissolved in the
ocean, can potentially have large effects on the atmosphere.
9.4.2 Paleoproductivity. There are a number of ways to affect the sharing of carbon
dioxide between ocean and atmosphere (see Sect. 3.7.1). For example, if dissolved
()
.0