THE NEAR-SURFACE LAYER OF THE OCEAN
and then extrapolated to the surface. Due to the burst mechanism in the
vicinity of whitecaps a shallow layer may exist where the small bubble
In addition to the effects on marine aerosol generation, the near-surface
layer populated by small bubbles may affect gas transfer. Very small bubbles
dissolve rapidly due to Laplace pressure; the water adjacent to the whitecap
can be supersaturated with atmospheric gases, thus contributing to the
supersaturation term, ' e , in the Woolf and Thorpe (1991) bulk-flux formula
Bubbles produced by the bubble-burst mechanism may also influence
the surface microlayers and their chemistry and microbiology (Blanchard,
1988). Rising bubbles accumulate surfactants and bacteria and transport
them to the surface. The bubble-burst bubbles thus represent a source of
materials to the surface microlayer, which modifies the balance between
diffusion to the interface due to turbulence and loss due to processes such as
aerosol generation, photochemistry, and surface disruption. The enhanced
oxygenation near the interface from dissolving micro-bubbles can modify
the microbiological environment of the sea surface microlayer
Detection of the secondary bubbles from measurements of whitecap
coverage is difficult since bubble bursting is dispersed horizontally, and the
production is localized very close to the ocean surface (e.g., shallower than a
significant wave height) where bubble measurements are extremely
complicated. The secondary bubbles have a short lifetime if they are not
transported away from the surface by turbulence or other fluid motions. The
turbulence generated by a surfacing bubble plume may also diffuse these
burst-bubbles deeper into the water column.
In addition to film and jet droplets, spume drops are produced by direct
tearing of water from wave crests at wind speeds higher than about 9 m s
-1 .
(Monahan et al., 1983). The spume drops are the largest spray droplets;
minimum radii are generally about 20 Pm and there is no definite maximum
radius. Spume generation is associated with eliminating the clearly defined
air-sea interface under high wind speed conditions. Koga (1981) has shown
from observations in a wind-wave tank that near the crest of the wave, where
the wind stress is generally highest, small projections develop, which then
break up to form droplets. The maximum diameter of these droplets was
about 3 mm in diameter. The projections were supposedly developing due
to Kelvin-Helmholtz instability.
Droplets with radii in the range 10–500 Pm contribute most to the
heat fluxes at high wind speeds (Andreas, 1992). This size range is
dominated by spume droplets, implying that spume generation is the most
important mechanism of droplet generation for mediating fluxes under very
high wind speed conditions.
414
for air-sea gas exchange (7.22).
concentration is significantly greater than elsewhere (Leifer et al., 2000b).
and then extrapolated to the surface. Due to the burst mechanism in the
vicinity of whitecaps a shallow layer may exist where the small bubble
In addition to the effects on marine aerosol generation, the near-surface
layer populated by small bubbles may affect gas transfer. Very small bubbles
dissolve rapidly due to Laplace pressure; the water adjacent to the whitecap
can be supersaturated with atmospheric gases, thus contributing to the
supersaturation term, ' e , in the Woolf and Thorpe (1991) bulk-flux formula
Bubbles produced by the bubble-burst mechanism may also influence
the surface microlayers and their chemistry and microbiology (Blanchard,
1988). Rising bubbles accumulate surfactants and bacteria and transport
them to the surface. The bubble-burst bubbles thus represent a source of
materials to the surface microlayer, which modifies the balance between
diffusion to the interface due to turbulence and loss due to processes such as
aerosol generation, photochemistry, and surface disruption. The enhanced
oxygenation near the interface from dissolving micro-bubbles can modify
the microbiological environment of the sea surface microlayer
Detection of the secondary bubbles from measurements of whitecap
coverage is difficult since bubble bursting is dispersed horizontally, and the
production is localized very close to the ocean surface (e.g., shallower than a
significant wave height) where bubble measurements are extremely
complicated. The secondary bubbles have a short lifetime if they are not
transported away from the surface by turbulence or other fluid motions. The
turbulence generated by a surfacing bubble plume may also diffuse these
burst-bubbles deeper into the water column.
In addition to film and jet droplets, spume drops are produced by direct
tearing of water from wave crests at wind speeds higher than about 9 m s
-1 .
(Monahan et al., 1983). The spume drops are the largest spray droplets;
minimum radii are generally about 20 Pm and there is no definite maximum
radius. Spume generation is associated with eliminating the clearly defined
air-sea interface under high wind speed conditions. Koga (1981) has shown
from observations in a wind-wave tank that near the crest of the wave, where
the wind stress is generally highest, small projections develop, which then
break up to form droplets. The maximum diameter of these droplets was
about 3 mm in diameter. The projections were supposedly developing due
to Kelvin-Helmholtz instability.
Droplets with radii in the range 10–500 Pm contribute most to the
heat fluxes at high wind speeds (Andreas, 1992). This size range is
dominated by spume droplets, implying that spume generation is the most
important mechanism of droplet generation for mediating fluxes under very
high wind speed conditions.
414
for air-sea gas exchange (7.22).
concentration is significantly greater than elsewhere (Leifer et al., 2000b).