44
S.M.P . Benbow
The range of factors affecting phytoplankton and their production of
DMS is therefore extremely varied , and the combination of factors
influencing the production of DMS in different regions at different times
will be the result of a complex mixture of these factors. Currently, it is
not understood which factors dominate and how they vary spatially or
temporally. In order to understand the role of DMS, it is vital to examine
not only the broad range of factors outlined above but also to consider
their role in otherwise productive regions. Highly productive regions,
such as upwelling regions, do not produce significantly higher amounts of
DMS (Charlson et aI., 1987). However, once DMS has been produced,
regardless of conditions , its effects are dependent upon its transfer to the
atmosphere and its subsequent deposition.
Increasingly, DMS is being shown to affect climatic variables. Shaw
(1983) proposed that the emission of sulfur gases by marine organisms
was the most efficient method of climate control. He proposed that global
warming could be offset by marine life increasing its output of carbonyl
sulfide and carbon disulfide; this would result in an increase in the number
of droplets of sulfuric acid in the stratosphere, thereby cooling the earth
by increasing the albedo . The DMS feedback, proposed by Charlson
et al. (1987), suggests that the DMS produced by marine phytoplankton
forms, CCN via oxidation in the atmosphere. These influence the earth's
albedo and hence the global climate, in turn affecting the phytoplankton.
The DMS feedback has been tested in order to understand its role in
climatic regulation. For example, Rampino and Yolk (1988) proposed
that mass extinctions at the Cretaceous/Tertiary boundary, when the
marine calcareous plankton were reduced by 90%, may have produced a
warming of up to 6°C or more if the DMS feedback was operational.
Therefore, study of the role of the DMS feedback in upwelling regions
and the relationships between some of the factors outlined above needs to
be undertaken. The remainder of this chapter focuses upon these problems and addresses the role of DMS in the climate system.
A GIS Model of DMS in the Eastern Pacific Environment
The operation of the DMS feedback can be demonstrated using a simple
box model, as shown in Figure 3.1, which provides plausible figures for
the production of DMS worldwide (see Table 3.1). The model itself is a
compilation of simple population biology models, a sea-air transfer
model , and an energy balance model to represent global climate. It is a
simple, broad-scale model to provide an indication of the operation of the
feedback and is by no means predictive. The population biology models
are designed to represent plausible behavior, though they are obviously
generalized to conform to the generality of the other model components.
To model the DMS feedback loop, observations of the processes inherent
S.M.P . Benbow
The range of factors affecting phytoplankton and their production of
DMS is therefore extremely varied , and the combination of factors
influencing the production of DMS in different regions at different times
will be the result of a complex mixture of these factors. Currently, it is
not understood which factors dominate and how they vary spatially or
temporally. In order to understand the role of DMS, it is vital to examine
not only the broad range of factors outlined above but also to consider
their role in otherwise productive regions. Highly productive regions,
such as upwelling regions, do not produce significantly higher amounts of
DMS (Charlson et aI., 1987). However, once DMS has been produced,
regardless of conditions , its effects are dependent upon its transfer to the
atmosphere and its subsequent deposition.
Increasingly, DMS is being shown to affect climatic variables. Shaw
(1983) proposed that the emission of sulfur gases by marine organisms
was the most efficient method of climate control. He proposed that global
warming could be offset by marine life increasing its output of carbonyl
sulfide and carbon disulfide; this would result in an increase in the number
of droplets of sulfuric acid in the stratosphere, thereby cooling the earth
by increasing the albedo . The DMS feedback, proposed by Charlson
et al. (1987), suggests that the DMS produced by marine phytoplankton
forms, CCN via oxidation in the atmosphere. These influence the earth's
albedo and hence the global climate, in turn affecting the phytoplankton.
The DMS feedback has been tested in order to understand its role in
climatic regulation. For example, Rampino and Yolk (1988) proposed
that mass extinctions at the Cretaceous/Tertiary boundary, when the
marine calcareous plankton were reduced by 90%, may have produced a
warming of up to 6°C or more if the DMS feedback was operational.
Therefore, study of the role of the DMS feedback in upwelling regions
and the relationships between some of the factors outlined above needs to
be undertaken. The remainder of this chapter focuses upon these problems and addresses the role of DMS in the climate system.
A GIS Model of DMS in the Eastern Pacific Environment
The operation of the DMS feedback can be demonstrated using a simple
box model, as shown in Figure 3.1, which provides plausible figures for
the production of DMS worldwide (see Table 3.1). The model itself is a
compilation of simple population biology models, a sea-air transfer
model , and an energy balance model to represent global climate. It is a
simple, broad-scale model to provide an indication of the operation of the
feedback and is by no means predictive. The population biology models
are designed to represent plausible behavior, though they are obviously
generalized to conform to the generality of the other model components.
To model the DMS feedback loop, observations of the processes inherent