disintegration of the polar ice sheets, with the surface
glaciers as a major contributor to an associated sea-level
rise.
The ecosystems of Canada, which are intrinsically linked to
climate will inevitably respond to these changes. In a
major assessment of the greenhouse effect on Canada,
research within Environment Canada suggests that across
Canada there will be generally milder winters and warmer
summers. The eastern and central parts of the country are
likely to get drier, while the west and north will get wetter.
As a result, the prairies are likely to face more frequent and
severe droughts of the type that have caused hundreds of
millions of dollars in losses in the mid-1980’s. At the same
time, climate warming would likely cause the Great Lakes
to drop (over the next few decades) by as much as one
meter because of greater evaporation with all the attendant
losses to hydro power, shipping and largely competing
demands for available water—lakes in northwestern Ontario
are already three degrees warmer than they were twenty
years ago and are ice-free for some 15 days more each year
(Keating, 1989). While water levels are predicted to fall in
the interior of Canada, they will rise on the sea coasts.
With a 250,000 km coastline (the world’s longest) that
ranges through widely varying environments and three
bounding oceans, Canada may be one of the countries at
greatest risk. If current global warming forecasts prove
accurate, and temperatures keep rising, the polar ice caps
will gradually melt and Canada’s surrounding oceanic
waters could potentially rise (perhaps by as much as 5-7 cm
each year). The ice barriers of the Arctic will melt back,
opening the Northwestern Passage to commercial and
military navigation (thus testing Canada’s claim to
sovereignty over the waters of the Canadian Arctic
archipelago). Weather in Canada will likely become more
extreme, leading to more storms with more powerful
winds. On the Atlantic coast, storm-driven waves and high
tides are already causing extensive flooding and property
damage. Storm tracks will likely shift, meaning that new
areas will be at risk. Depending on the extent of local
development, this could result in further property
destruction and disrupt transportation networks and
municipal services.
Knowledge of the climatic changes, especially of the Arctic
Ocean, is however, more than of regional importance to
Canada. The country’s vast extent (-7% of the Earth’s
land surface), critical high latitude position, and dominant
role in the global climate of the past ensure that the
Canadian landmass and the arctic regions in particular will
attract considerable attention within Global Change related
programs (e.g. the International Geosphere-Biosphere
Program (IGBP), and future programs such as Eos). For
instance, it would be impossible to model former global
changes without understanding the glacial/postglacial
history of the Laurentide ice sheet. In addition, existing
climatic models suggest that the greatest impact of potential
global warming will occur first and be most dramatically
detected in higher latitudes. Hence understanding the
critical role Canada’s environment and particularly of the
Canadian Arctic is vital to future climatic scenarios and in
determining the global climate and ocean circulation
systems.
GEODETIC SATELLITES TO IMPLEMENT
THE EARTH OBSERVING STRATEGY
The only way to evaluate the effects of global change, not
only in Canada but also at a global scale, is to try to model
the interactions of the processes involved, both now and in
the past, while maintaining an information system in which
long-term and short-term observational records are
obtained routinely, maintained and interpreted.
Unequivocal documentation of change is needed to provide
state variables for prediction models and to establish the
hard evidence on which difficult decisions must be based.
In this context, geodetic and remote sensing satellites will
have a prominent role to play in the various pre-Eos and
Eos planned programs. Altimeter-carrying satellites in
particular will provide important data for the monitoring of
the oceans and the coupling of the ocean and the
atmosphere, all of which are essential for the understanding
of the dynamics of the ocean circulation, the role of the
oceans in the climate, and the refinements of the Earth’s
gravitational field models.
TOPEXIPoseidon will be a dedicated altimetry mission
planned for a 1994 time frame launch, offering the highest
achievable accuracy and precision (~1 cm) over most
wavelengths of interest, in an orbit specifically chosen to
produce optimum results for oceanographic experiments.
An earlier mission, with the European Space Agency’s
ERS-1 satellite (planned for an early 1991 launch), is
primarily oriented towards ice and ocean monitoring with,
in addition, all-weather high resolution microwave imaging
capabilities over land and coastal zones. To fulfill the
measurement objectives of the mission, ERS-1 will carry
instrumentation consisting of a core set of sensors (i.e. a
Synthetic Aperture Radar (SAR) and a wave and wind
Scatterometer, and a nadir-pointing Radar Altimeter)
supported by additional complementary instruments (i.e. an
Along Track Scanning Radiometer and Microwave
Sounder, and Presice Range and Range-rate Equipment,
PRARE) providing in general all-weather, day and night,
high accuracy observations. With a planned minimum
temporal overlap with TOPEX of one year, ERS-1 will
extend orbital coverage to the highest achievable latitudes
(-82°) to give coverage of the near-polar regions. In
addition, adequate plans exist to date, in NASA’s
Geopotential REsearch Mission (GREM) and ESA’s
ARISTOTELES mission, for a gravity program capable of
determining the Earth’s geoid with an absolute accuracy of
2 cm or better down to wavelengths of the order of 100 km
which is essential not only for the determination of the
time-variable ocean circulation, but also for the accurate
determination of the satellite’s orbit.
As part of NASA’s and ESA’s multi-mission Earth
Observation System (Eos) program, TOPEX-class radar
altimeters, combined with the modern practices of precision
orbit determination, will provide accurate and precise
means of sea surface topography changes over several
years. When combined with appropriate in-situ
measurements these obervations will permit the
determination of a three-dimensional structure of the world
oceans. Also proposed for Eos is a Geodynamics Laser
Ranging and Altimeter System (GLRS), for rapid
measurements of crustal deformation and micro
topography mapping of the ocean, land and ice surfaces. In
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