Abstract

Laser spectroscopy and laser probes now provide previously unobtainable information on the physico-chemical structure and processes of the ocean microlayer. Methods range from laboratory techniques to in situ ocean microlayer probes.

In the laboratory, laser-induced fluorescence from water-soluble dye molecules is used to track aqueous layer interfacial movement. With these techniques, researchers infer turbulence in the upper several millimetres of a water surface. It is also possible to measure timescales of interfacial layer concentration fluctuations and interfacial layer penetration depths thus providing estimates of gas transfer velocities. Laser induced fluorescence methods are presently limited to laboratory studies.

Two-dimensional scanning laser slope gauges provide in situ measurement of ocean slope. Ocean slope is measured from the refraction of a vertical laser beam upon passing from the ocean into the air. By rapid scanning of the laser beam through a geometric pattern on the ocean surface, the researcher determines ocean wave slope at a variety of surface positions. This measurement is performed on a timescale during which the ocean surface is essentially frozen in time. From the set of slopes, an estimate is obtained of the two-dimensional capillary–gravity wave spectrum for a given instant of time and a given region of ocean surface.

Nonlinear spectroscopic processes such as reflected second harmonic generation and reflected sum frequency generation provide non-intrusive in situ spectroscopic probes of the ocean surface.