Introduction to the shelf seas - Introduction to the Physical and Biological Oceanography of Shelf Seas - page 9

the frictional dissipation previously estimated by G. I. Taylor. Bowden determined
the stresses by inferences from the dynamical balance (Bowden and Fairbairn, 1952 )
and later went on to make the first direct measurements of stress in the ocean using
the newly-developed electromagnetic flowmeter (Bowden and Fairbairn, 1956 ).
With these and many other contributions, Bowden, a quiet and modest man, was
responsible for stimulating progress in the physical oceanography of the shelf seas
and for laying the foundation for many of the developments we shall be considering
in later chapters.
At the same time, important progress was being made in understanding the biology
of the shelf seas. Working over Georges Bank, Gordon Riley, along with Henry
Stommel and Dean Bumpus, developed the fundamental understanding of how the
spring bloom of phytoplankton is triggered by physical stability. From our twenty-
first-century perspective, the idea of stability and light being key to rapid phyto-
plankton growth in the surface ocean can perhaps seem blindingly obvious, but in the
1930s and early 1940s there was some considerable effort aimed at demonstrating
that the spring bloom was a product of grazing pressure, an idea related to a large
degree to the understanding of terrestrial ecosystems. We will, however, see how
grazing does play a more subtle role in determining the species that dominate the
spring bloom later in Chapter 5 . Riley applied statistical analyses to his careful
sampling of phytoplankton biomass and growth over Georges Bank, leading to a
key paper in biological oceanography (Riley, 1946 ) which included one of the first
coupled theoretical models of physics and phytoplankton growth, the basics of which
can still be seen in the codes of most coupled models today.

1.5 Instrumentation: 'Tools of the trade'

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Progress in oceanography has been, and continues to be, closely linked to technical
developments for making measurements in the ocean. This is true to some degree in
most scientific disciplines, but in few areas is the constraint of technical limitation
as severe as it is in our efforts to understand the workings of the ocean. The basic
problem is that the ocean is largely impenetrable to electromagnetic radiation. Even
in relatively clear water, light is absorbed on a scale of tens of metres, and at other
wavelengths the absorption of energy is even more rapid. Only sound waves can
travel relatively freely through the ocean, and even then, long-range propagation
is restricted to low frequencies where the scope for the transmission of information is
limited. So, unlike meteorologists who can watch the evolution of the atmosphere
through the movement of clouds and measure velocities remotely with radar, ocean-
ographers have to rely mainly on measurements from sensor systems lowered into the
ocean or make the most of what can be learned from probing by acoustic methods.
In this section, we shall consider the principal measurement tools and instrument
platforms which are now available to determine the physical, chemical and biological
characteristics through the water column.