THE NEAR-SURFACE LAYER OF THE OCEAN
nevertheless, are closely related. For example, phytoplankton in the water
column produces particulate organic matter and a variety of biogenic
chemicals and gases, which then rise to the surface where they enter the
microlayer (Hardy et al., 1997). This organic matter modifies surface films,
which affects the gravity-capillary waves and, thus, the air-sea gas exchange
on the global scale.
Increasing pollution of the ocean threatens marine neuston and represents
one of the significant factors accelerating global ecological changes.
Anthropogenic enrichment of the sea surface impacts natural biochemical
processes in the ocean microlayer affecting the air-sea CO 2 exchange with
possible consequences for global climate (Hardy et al, 1997).
On the other hand, iron (the element which limits primary biological
productivity) is supplied to the ocean via the surface microlayer. The
increase of productivity due to an increased iron supply stimulates the
ocean’s “biological pump” increasing the CO 2 uptake by the ocean and
potentially reducing the global warming (Wu et al., 2003).
The mechanical influence of disturbances produced by the swimming
motion of small zooneuston organisms perhaps may also contribute to the
microlayer structure at some level (Gladyshev, 1997). Flying fish, birds, and
ships disturb the microlayer significantly, though only locally.
2.2.7 Effects of surface films
Surface films are an important part of the surface microlayer. Air-sea
exchanges depend on film properties, especially under low wind speed
conditions. The presence of surface films on the ocean is one of the factors
leading to uncertainty in the existing air-sea exchange parameterizations.
The effects of surface films are dependent on surfactant type,
concentration, and wind-wave regime. Breaking waves and near-surface
flow convergences substantially erode the surface films above wind speeds
of 5 - 6 m s
-1 . Surface films are also fragmented by rain.
Surface films can affect air-sea exchanges through static and dynamic
mechanisms (Liss, 1983). The static mechanism results from the physical
barrier provided by the film; it requires the presence of organized
(condensed, solid) surfactant films that can easily be reproduced in the
laboratory but hardly survive typical oceanic conditions of wind and waves.
The surfactant films or slicks with high surface concentrations of organic
material occupy only a small fraction of the global ocean surface. The
dominant point of view among ocean chemists is that surfactant
concentrations are quite low in the open ocean. The static mechanism
thereby is not of primary importance for typical open ocean conditions (Liss
and Duce, 1997). The dynamic mechanism is more important in the ocean,
because it can be effective even with relatively low surfactant
concentrations.
86
nevertheless, are closely related. For example, phytoplankton in the water
column produces particulate organic matter and a variety of biogenic
chemicals and gases, which then rise to the surface where they enter the
microlayer (Hardy et al., 1997). This organic matter modifies surface films,
which affects the gravity-capillary waves and, thus, the air-sea gas exchange
on the global scale.
Increasing pollution of the ocean threatens marine neuston and represents
one of the significant factors accelerating global ecological changes.
Anthropogenic enrichment of the sea surface impacts natural biochemical
processes in the ocean microlayer affecting the air-sea CO 2 exchange with
possible consequences for global climate (Hardy et al, 1997).
On the other hand, iron (the element which limits primary biological
productivity) is supplied to the ocean via the surface microlayer. The
increase of productivity due to an increased iron supply stimulates the
ocean’s “biological pump” increasing the CO 2 uptake by the ocean and
potentially reducing the global warming (Wu et al., 2003).
The mechanical influence of disturbances produced by the swimming
motion of small zooneuston organisms perhaps may also contribute to the
microlayer structure at some level (Gladyshev, 1997). Flying fish, birds, and
ships disturb the microlayer significantly, though only locally.
2.2.7 Effects of surface films
Surface films are an important part of the surface microlayer. Air-sea
exchanges depend on film properties, especially under low wind speed
conditions. The presence of surface films on the ocean is one of the factors
leading to uncertainty in the existing air-sea exchange parameterizations.
The effects of surface films are dependent on surfactant type,
concentration, and wind-wave regime. Breaking waves and near-surface
flow convergences substantially erode the surface films above wind speeds
of 5 - 6 m s
-1 . Surface films are also fragmented by rain.
Surface films can affect air-sea exchanges through static and dynamic
mechanisms (Liss, 1983). The static mechanism results from the physical
barrier provided by the film; it requires the presence of organized
(condensed, solid) surfactant films that can easily be reproduced in the
laboratory but hardly survive typical oceanic conditions of wind and waves.
The surfactant films or slicks with high surface concentrations of organic
material occupy only a small fraction of the global ocean surface. The
dominant point of view among ocean chemists is that surfactant
concentrations are quite low in the open ocean. The static mechanism
thereby is not of primary importance for typical open ocean conditions (Liss
and Duce, 1997). The dynamic mechanism is more important in the ocean,
because it can be effective even with relatively low surfactant
concentrations.
86