Chemistry Reference
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later, in assessing mass-transfer rates on global scales (for balancing global
budgets for CO
2
and other environmentally important gases).
It became apparent that the presence of surfactant films could affect all
of these estimates, but at the time when the first quantitative studies were
being performed on capillary ripple propagation, many aspects of the re-
mote sensing field were still in stages of development. For instance, su-
percomputers had not yet developed to the point where dense maps of
wind speed could be assimilated in real time to predict global weather.
Similarly, synthetic aperture radar had not yet been developed to produce
the scale resolution needed for ship wake tracking or internal wave field
interpretation. It was also evident that environmental issues of global
warming and greenhouse gases had not yet achieved prominent recog-
nition. These reasons accounted for the ebb in research efforts between the
time of the first formulation by Levich in 1962 and the revitalisation that
occurred two decades ago. The renewed interest that occurred in the 1980s
was spurred by the maturation of several independent technologies, includ-
ing computing power, remote-sensing capabilities, and the development of
robust techniques for making short wave measurements
in situ.
This com-
bination enabled studies to assess the amount, extent, and physical proper-
ties of the microlayer that forms at the air-sea interface from both natural
and anthropogenic sources.
2 Theoretical and experimental studies
Following Levich, subsequent wave propagation studies sought to deter-
mine the extent to which surface films modify the air-water interface and
its dynamics for intermediate cases of surface dilational viscoelasticity
(Mann and Hansen 1963, Hansen and Mann 1964, van den Temple and
van de Riet 1965, Lucassen-Reynders and Lucassen 1969, Cini and
Lombardini 1978, Hühnerfuss et al. 1982, Bock and Mann 1989). Theory
predicted, and laboratory studies validated, that damping enhancements
could exceed two orders of magnitude under some circumstances. The
bulk of the experimental data was obtained from measurements of the dis-
tance-damping characteristics of short ripples. The wavelengths studied
ranged from roughly 0.01 cm to 10 cm using waves induced by mechani-
cal, electro-capillary, active thermal, and passive thermal techniques (Sohl
et al. 1978, Bock 1987, Stenvot and Langevin 1988).
Other experimental efforts focused on the collection of ocean surface
samples in order to investigate properties of the marine microlayer in the
laboratory. Samples were retrieved using either inert screens (Garrett
1965) or drum-type samplers (Carlson et al. 1988, Frew and Nelson 1992).
