Spectra of Backscattered Light from the Sea Obtained from Aircraft as a Measure of Chlorophyll Concentration

Clarke, George L.; Ewing, Gifford C.; Lorenzen, Carl J.

doi:10.1126/science.167.3921.1119

Cited by 215 publications

(81 citation statements)

References 7 publications

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“…Terrestrial ecosystems would also become less efficient at photon dissipation with less water in the global water cycle. Incident angle and frequency dependent albedo for sunlight on ocean water of today has been measured by Clarke et al (1970) and Jin et al (2004). They find that organic material in ocean water reduces the albedo at all incident angles and wavelengths and that this effect increases significantly towards the shorter wavelengths of the ultraviolet.…”

Section: The Sea-surface and Entropy Productionmentioning

confidence: 99%

Thermodynamic dissipation theory for the origin of life

Michaelian

2011

Earth Syst. Dynam.

168

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Abstract. Understanding the thermodynamic function of life may shed light on its origin. Life, as are all irreversible processes, is contingent on entropy production. Entropy production is a measure of the rate of the tendency of Nature to explore available microstates. The most important irreversible process generating entropy in the biosphere and, thus, facilitating this exploration, is the absorption and transformation of sunlight into heat. Here we hypothesize that life began, and persists today, as a catalyst for the absorption and dissipation of sunlight on the surface of Archean seas. The resulting heat could then be efficiently harvested by other irreversible processes such as the water cycle, hurricanes, and ocean and wind currents. RNA and DNA are the most efficient of all known molecules for absorbing the intense ultraviolet light that penetrated the dense early atmosphere and are remarkably rapid in transforming this light into heat in the presence of liquid water. From this perspective, the origin and evolution of life, inseparable from water and the water cycle, can be understood as resulting from the natural thermodynamic imperative of increasing the entropy production of the Earth in its interaction with its solar environment. A mechanism is proposed for the reproduction of RNA and DNA without the need for enzymes, promoted instead through UV light dissipation and diurnal temperature cycling of the Archean sea-surface.

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Section: The Sea-surface and Entropy Productionmentioning

confidence: 99%

Thermodynamic dissipation theory for the origin of life

Michaelian

2011

Earth Syst. Dynam.

168

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“…By absorbing and dissipating UV and visible light on the surface of oceans and lakes, life therefore augments the entropy production of the Earth in its solar environment. Without life at the surface, a greater portion of light would be reflected, increasing the albedo of Earth (Clarke et al, 1970, give measurements for the reduction of water albedo at different frequencies due to the presence of organic material), and light would penetrate deeper into the ocean, thereby augmenting the overall bulk black-body temperature of the ocean (see, for example, Jones et al, 2005 for the effect of phytoplankton on the temperature profile with depth for a lake). Both effects reduce the entropy production of Earth; greater albedo reduces the amount of available light to dissipate, and penetration of light to greater depth shifts the radiated spectrum (day + night integrated) to shorter wavelengths (see Eq.…”

Section: Entropy Production Due To Life In the Ocean Surface Layermentioning

confidence: 99%

HESS Opinions "Biological catalysis of the hydrological cycle: life's thermodynamic function"

Michaelian

2012

Hydrol. Earth Syst. Sci.

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Abstract. Darwinian theory depicts life as being overwhelmingly consumed by a fight for survival in a hostile environment. However, from a thermodynamic perspective, life is a dynamic, out of equilibrium process, stabilizing and coevolving in concert with its abiotic environment. The living components of the biosphere on the Earth's surface of greatest biomass, the plants and cyanobacteria, are involved in the transpiration of a vast amount of water. Transpiration is part of the global water cycle, and it is this cycle that distinguishes Earth from its apparently life-barren neighboring planets, Venus and Mars. The dissipation of sunlight into heat by organic molecules in the biosphere, and its coupling to the water cycle (as well as other abiotic processes), is by far the greatest entropy-producing process occurring on Earth. Life, from this perspective, can be viewed as performing an important thermodynamic function, acting as a dynamic catalyst by aiding irreversible abiotic processes such as the water cycle, hurricanes, and ocean and wind currents to produce entropy. The role of animals in this view is that of unwitting but dedicated servants of the plants and cyanobacteria, helping them to grow, and to spread into initially inhospitable areas.

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“…6 This followed on from the work of Clarke et al 7 who showed that chlorophyll concentration in the ocean surface waters could be estimated from airborne measurements of the light leaving the sea surface. CZCS made measurements in four channels in the visible part of the spectrum, one channel in the near-infrared, and one in the infrared (IR) (see Table 2 for details of the sensor).…”

Section: A Brief History Of Ocean Color Measurements From Spacementioning

confidence: 99%

Biological Oceanography by Remote Sensing

Srokosz

2000

Encyclopedia of Analytical Chemistry

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Biological oceanography may be studied from space using sensors on satellites that determine the color of the ocean. The presence of phytoplankton (microscopic algae) in the upper layers of the ocean changes the color of the water as seen from above. In simplified terms, this is due to the selective absorption of blue light by the phytoplankton pigments (primarily chlorophyll) which changes the appearance of the water from blue to green. These changes in color can be observed using a satellite‐borne spectroradiometer that measures the water‐leaving radiance in a number of bands in the visible part of the electromagnetic spectrum. The limitations of the technique are first, that only information on the phytoplankton in the upper layers of the ocean can be obtained (light does not penetrate very far into the ocean). Second, most of the signal measured by the satellite sensor originates in the atmosphere (due to the molecular and aerosol scattering of photons there), so careful correction for atmospheric effects is necessary if good ocean data are to be obtained. Of course, in the presence of clouds the sensor will not “see” the ocean surface at all, and no data will be obtained. Third, only one component of the ocean ecosystem, namely the phytoplankton, can be studied by this means. Despite these limitations, satellite observations of ocean color have given new insights into biological oceanography on a global scale that could not have been obtained by any other means of observation. Observations of ocean color have contributed to a better understanding of the biophysical interactions that determine the phytoplankton productivity, the seasonal and interannual variations of the phytoplankton biomass on global scales, and the role of phytoplankton in the climate system. They have also contributed to the improved modeling of biogeochemical processes in the ocean.

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Spectra of Backscattered Light from the Sea Obtained from Aircraft as a Measure of Chlorophyll Concentration

Cited by 215 publications

References 7 publications

Thermodynamic dissipation theory for the origin of life

Thermodynamic dissipation theory for the origin of life

HESS Opinions "Biological catalysis of the hydrological cycle: life's thermodynamic function"

Biological Oceanography by Remote Sensing

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Spectra of Backscattered Light from the Sea Obtained from Aircraft as a Measure of Chlorophyll Concentration

Cited by 215 publications

References 7 publications

Thermodynamic dissipation theory for the origin of life

Thermodynamic dissipation theory for the origin of life

HESS Opinions &quot;Biological catalysis of the hydrological cycle: life's thermodynamic function&quot;

Biological Oceanography by Remote Sensing

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HESS Opinions "Biological catalysis of the hydrological cycle: life's thermodynamic function"