20 Ocean-Colour Radiometry
357
subject of much debate. But discussions of straddling ecosystems may only be just
beginning. If integrity of ecosystems is to be maintained when marine resources are
exploited, and if an ecosystem is spread over more than one national jurisdiction,
then international agreements would have to be in place to implement ecosystembased management. In implementation of such agreements, remote sensing would
have a key role to play in mapping ecosystems, and their movements over time.
It is worth recalling that most of the ocean lies outside the jurisdiction of any
nation. The high seas are a commons whose welfare is in jeopardy unless some form
of high-seas governance is brought to bear. Information, continuously updated, will
be the key to success in this regard. Because remote sensing of ocean colour provides our only window into the ocean ecosystem on synoptic scales, we can expect
that, through the ecological indicators it provides, it will become of increasing
importance in future years for the rational management of the high seas.
Applications are enhanced when ocean-colour data are complemented with other
satellite-derived data, for example sea-surface temperature and photosyntheticallyavailable radiation, PAR. Some of the ocean-colour products and their applications
are presented schematically in Fig. 20.1.
20.5 Conclusion
In addition to advances in the technology, the interpretation and the applications,
what other developments may we see in the future? It is interesting to speculate
that there will be new developments and improvements in validation of the satellitederived products using in-situ data. In validation exercises, the in-situ observations
are considered the “truth”. But it may be argued that, at the scale of the satellite
observations determined by the pixel resolution at ground level, what the satellite
seas is the “truth”, in the sense that only the satellite is able to sample the entire
area in an instant. Furthermore, the satellite observations yield information without
the need for collecting sea-water samples, handling them or extracting pigments,
all of which add errors to the in-situ observations. Though the satellite observations
have also their own sources of error associated with radiometric data collection and
application of algorithms, the satellite observations may be more representative of
what is there at the scale of the pixel, than information derived from small volume
analyses from in-situ observing platforms. Will we get to the stage where the radiometric quantities derived from satellites will be treated as the primary standard at
that scale observation for some of the retrieved properties? Perhaps, but before we
attain that level of confidence in satellite observations, the issue of incompatibilities
in scales that continues to plague validation exercises has to be addressed fully. It
may be that some new thinking in our approaches to validation is needed, before the
issue is laid to rest.
The main thrust of the paper is on the potential for further development in the
field of ocean-colour research. But what factors are likely to set limits on further
growth? These would include the plasticity in inherent optical properties of phytoplankton, which makes it difficult to assign unique optical properties to different
357
subject of much debate. But discussions of straddling ecosystems may only be just
beginning. If integrity of ecosystems is to be maintained when marine resources are
exploited, and if an ecosystem is spread over more than one national jurisdiction,
then international agreements would have to be in place to implement ecosystembased management. In implementation of such agreements, remote sensing would
have a key role to play in mapping ecosystems, and their movements over time.
It is worth recalling that most of the ocean lies outside the jurisdiction of any
nation. The high seas are a commons whose welfare is in jeopardy unless some form
of high-seas governance is brought to bear. Information, continuously updated, will
be the key to success in this regard. Because remote sensing of ocean colour provides our only window into the ocean ecosystem on synoptic scales, we can expect
that, through the ecological indicators it provides, it will become of increasing
importance in future years for the rational management of the high seas.
Applications are enhanced when ocean-colour data are complemented with other
satellite-derived data, for example sea-surface temperature and photosyntheticallyavailable radiation, PAR. Some of the ocean-colour products and their applications
are presented schematically in Fig. 20.1.
20.5 Conclusion
In addition to advances in the technology, the interpretation and the applications,
what other developments may we see in the future? It is interesting to speculate
that there will be new developments and improvements in validation of the satellitederived products using in-situ data. In validation exercises, the in-situ observations
are considered the “truth”. But it may be argued that, at the scale of the satellite
observations determined by the pixel resolution at ground level, what the satellite
seas is the “truth”, in the sense that only the satellite is able to sample the entire
area in an instant. Furthermore, the satellite observations yield information without
the need for collecting sea-water samples, handling them or extracting pigments,
all of which add errors to the in-situ observations. Though the satellite observations
have also their own sources of error associated with radiometric data collection and
application of algorithms, the satellite observations may be more representative of
what is there at the scale of the pixel, than information derived from small volume
analyses from in-situ observing platforms. Will we get to the stage where the radiometric quantities derived from satellites will be treated as the primary standard at
that scale observation for some of the retrieved properties? Perhaps, but before we
attain that level of confidence in satellite observations, the issue of incompatibilities
in scales that continues to plague validation exercises has to be addressed fully. It
may be that some new thinking in our approaches to validation is needed, before the
issue is laid to rest.
The main thrust of the paper is on the potential for further development in the
field of ocean-colour research. But what factors are likely to set limits on further
growth? These would include the plasticity in inherent optical properties of phytoplankton, which makes it difficult to assign unique optical properties to different