THE NEAR-SURFACE LAYER OF THE OCEAN
of the scatter from particles (the chlorophyll). For the void fraction of order
10
-5 (note that average void fractions of 10
-5 are observed at wind speed of
~12 ms
-1 ), the bubble scatter is about equal with that of chlorophyll for 0.5
mg m
–3 concentration.
The remote sensing relevant parameter is the backscatter parameter b b .
The bubble backscatter exceeds the backscatter for pure water at average
void fractions of 10
-5 (Figure 7-7b). Terrill et al. (2001) unfortunately do
not provide the corresponding backscatter parameter for chlorophyll D. It is
therefore impossible to make quantitative estimates of the distortion of color
imagery by bubbles from their results. The effect of bubbles is most likely
strong under high wind speed conditions, especially if the assumption of
Zhang et al. (1998) regarding the role of organic films in coating the bubbles
and enhancing their ability to scatter the light is correct.
7.3 Marine Chemistry and Biology
Chemical and photochemical reactions in the near-surface layer of the
ocean ensure the growth and accumulation of phytoplankton and neuston.
Some of the chemical processes in the upper ocean do not require light (dark
chemical processes). Other chemical processes are excited by chemical
absorption of sunlight (photochemical processes). The biological cycling and
supply of inorganic and organic elements necessary for phytoplankton
growth can depend on both dark chemical and photochemical reactions
(Bissett et al., 2001). The cycling of dissolved inorganic macronutrients
(nitrogen, phosphorous, silica, etc.) is mostly related to biological activity in
the water, with plant growth removal and microbial regeneration, rather than
to photochemical reactions. In some situations, mixing processes can lead to
substantial redistribution of chemical properties in the upper ocean,
overshadowing in situ chemical reactions. The supply of materials such as
cobalt, iron, manganese, vitamins and some other essential micronutrients
depends on biological, dark-chemical, and photochemical reactions.
The majority of ultraviolet irradiance (O< 400 nm) in the sea is absorbed
by chromophoric (colored) dissolved organic matter (CDOM). This absorbed
The photochemical reactions include photo-destruction of chemical bonds
and fragmentation of complex molecules into smaller compounds; both
reactions are of fundamental importance for bio-productivity in the upper
ocean (Plane et al., 1997; Bissett et al., 2001). These photochemical
reactions can both promote (by breaking down complex molecules and
increasing accessibility of organic carbon and some inorganic nutrients) and
retard (by damaging cellular constituents) biological processes. In addition,
secondary reaction between energized organic molecules and dissolved
456
energy drives photochemical reactions in the near-surface layer of the ocean.
of the scatter from particles (the chlorophyll). For the void fraction of order
10
-5 (note that average void fractions of 10
-5 are observed at wind speed of
~12 ms
-1 ), the bubble scatter is about equal with that of chlorophyll for 0.5
mg m
–3 concentration.
The remote sensing relevant parameter is the backscatter parameter b b .
The bubble backscatter exceeds the backscatter for pure water at average
void fractions of 10
-5 (Figure 7-7b). Terrill et al. (2001) unfortunately do
not provide the corresponding backscatter parameter for chlorophyll D. It is
therefore impossible to make quantitative estimates of the distortion of color
imagery by bubbles from their results. The effect of bubbles is most likely
strong under high wind speed conditions, especially if the assumption of
Zhang et al. (1998) regarding the role of organic films in coating the bubbles
and enhancing their ability to scatter the light is correct.
7.3 Marine Chemistry and Biology
Chemical and photochemical reactions in the near-surface layer of the
ocean ensure the growth and accumulation of phytoplankton and neuston.
Some of the chemical processes in the upper ocean do not require light (dark
chemical processes). Other chemical processes are excited by chemical
absorption of sunlight (photochemical processes). The biological cycling and
supply of inorganic and organic elements necessary for phytoplankton
growth can depend on both dark chemical and photochemical reactions
(Bissett et al., 2001). The cycling of dissolved inorganic macronutrients
(nitrogen, phosphorous, silica, etc.) is mostly related to biological activity in
the water, with plant growth removal and microbial regeneration, rather than
to photochemical reactions. In some situations, mixing processes can lead to
substantial redistribution of chemical properties in the upper ocean,
overshadowing in situ chemical reactions. The supply of materials such as
cobalt, iron, manganese, vitamins and some other essential micronutrients
depends on biological, dark-chemical, and photochemical reactions.
The majority of ultraviolet irradiance (O< 400 nm) in the sea is absorbed
by chromophoric (colored) dissolved organic matter (CDOM). This absorbed
The photochemical reactions include photo-destruction of chemical bonds
and fragmentation of complex molecules into smaller compounds; both
reactions are of fundamental importance for bio-productivity in the upper
ocean (Plane et al., 1997; Bissett et al., 2001). These photochemical
reactions can both promote (by breaking down complex molecules and
increasing accessibility of organic carbon and some inorganic nutrients) and
retard (by damaging cellular constituents) biological processes. In addition,
secondary reaction between energized organic molecules and dissolved
456
energy drives photochemical reactions in the near-surface layer of the ocean.