43
Descriptive Oceanography
Since the mid-1970s, the ratio of F-11/F-12 in the atmosphere has remained nearly constant
(see Figure 1.49).
In more recent years, these amounts have leveled off and will decrease in the future.
Since these compounds have a long lifetime (75–100 yr) in the atmosphere, they can be
widely dispersed in the environment. As will be discussed further, their movement into
the stratosphere can lead to the destruction of ozone (Chapter 5). Much of these compounds
can be rained out and deposited on the surface of the oceans. This serves as a dye that can
be used to examine the movement of surface waters into the deep. The development of sensitive electron- capture gas chromatography by Lovelock, Maggs, and Wade (1973) has led
to the measurement of CFCs in ocean waters as a function of time and location. At present,
it is possible to detect 5 × 10 –15 mol kg –1 (5 fM) in a 30-cm 3 sample of seawater. The concentrations in surface waters are about three times higher than the detection limit. At these
levels, one must be careful to avoid sample contamination. The inputs of CFCs to the atmosphere have been modeled based on production records with corrections for losses due
to photolysis in the stratosphere. Most (90%) of the release has occurred in the Northern
Hemisphere. Due to the long lifetime and the rapid latitudinal mixing of the lower atmosphere (2 yr) these compounds are relatively uniformly distributed in the troposphere.
21
22
23
σ
θ (kg/m
3
)
24
25
26
27
0.5
1
3
1
0.5
2 1.5
1.5
28
–30
–20
–10
0
Tritium
TU91
10
20
30
3.00
2.00
1.00
0.50
0.25
0.10
0.05
0.00
21
22
23
σ
θ (kg/m
3
)
24
25
26
0 .5
1
3
4
2
27
–30
–20
–10
0
Latitude
Excess 3 He
TU
10
20
30
6.0
4.0
2.0
1.0
0.5
0.2
0.1
0.0
Figure 1.48
Section of tritium in the Pacific Ocean.
Descriptive Oceanography
Since the mid-1970s, the ratio of F-11/F-12 in the atmosphere has remained nearly constant
(see Figure 1.49).
In more recent years, these amounts have leveled off and will decrease in the future.
Since these compounds have a long lifetime (75–100 yr) in the atmosphere, they can be
widely dispersed in the environment. As will be discussed further, their movement into
the stratosphere can lead to the destruction of ozone (Chapter 5). Much of these compounds
can be rained out and deposited on the surface of the oceans. This serves as a dye that can
be used to examine the movement of surface waters into the deep. The development of sensitive electron- capture gas chromatography by Lovelock, Maggs, and Wade (1973) has led
to the measurement of CFCs in ocean waters as a function of time and location. At present,
it is possible to detect 5 × 10 –15 mol kg –1 (5 fM) in a 30-cm 3 sample of seawater. The concentrations in surface waters are about three times higher than the detection limit. At these
levels, one must be careful to avoid sample contamination. The inputs of CFCs to the atmosphere have been modeled based on production records with corrections for losses due
to photolysis in the stratosphere. Most (90%) of the release has occurred in the Northern
Hemisphere. Due to the long lifetime and the rapid latitudinal mixing of the lower atmosphere (2 yr) these compounds are relatively uniformly distributed in the troposphere.
21
22
23
σ
θ (kg/m
3
)
24
25
26
27
0.5
1
3
1
0.5
2 1.5
1.5
28
–30
–20
–10
0
Tritium
TU91
10
20
30
3.00
2.00
1.00
0.50
0.25
0.10
0.05
0.00
21
22
23
σ
θ (kg/m
3
)
24
25
26
0 .5
1
3
4
2
27
–30
–20
–10
0
Latitude
Excess 3 He
TU
10
20
30
6.0
4.0
2.0
1.0
0.5
0.2
0.1
0.0
Figure 1.48
Section of tritium in the Pacific Ocean.