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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