Geology Reference
In-Depth Information
5
Aging of Sea Ice: Stories That Were Never Told
In the context of imaging radar remote sensing applica-
tions in sea ice, the series of Mould Bay experiments is
considered to be one of the major early endeavors that
led to the development of Canada's first remote sensing
satellite, Radarsat‐1. On 13 September 1989, the govern-
ment of Canada announced its initiative to build and
operate the satellite, which carried a single payload sen-
sor, synthetic aperture radar. The design of the sensor
was based on more than 10 years of mission study and
preparation in Canada. Monitoring sea ice was a prime
objective of the mission at that time. That was the time
when exploration and utilization of gas and petroleum in
the Arctic carried great promise and with it the realiza-
tion that the only reliable tool to gather regular informa-
tion on Arctic ice conditions would be a space‐borne
imaging radar system. That is how Arctic ice monitoring
became the prime economic drive for Radarsat‐1, 2, and
the future Radarsat‐3.
Until the late 1970s knowledge of radar signatures of
ice types as well as their strength and deformation pro-
perties was limited. It was inclined in general toward
qualitative speculations. The knowledge on the physics
and mechanics of ice and particularly natural sea ice as a
solid‐state material had advanced significantly by the
early 1980s. The technical questions that the investigators
of Canada's remote sensing Radarsat mission, which
started in 1981, had to address were about the specifica-
tions (frequency, polarization, incidence angle, spatial
resolution) of the radar system that offer the best dis-
crimination between ice types as well as between ice and
open water. For that purpose, Canada launched and
supported a few field campaigns in the Arctic to measure
microwave signatures (passive and active as explained in
section 7.1) from sea ice in relation to detailed studies on
physical properties of sea floating in the oceans. The task
was to provide practical ranges of radar backscatter from
various types of ice under different meteorological and
formation conditions.
There were numerous investigations on sea ice at many
locations scattered all over the Arctic beyond the Arctic
Circle, namely Beaufort Sea, Canada Basin, Sverdrup
Basin, and Baffin Bay, but all of them were performed on
an opportunity basis. Long‐term field studies on sea ice
in the Canadian High Arctic were conducted at three dif-
ferent high‐latitude locations: Pond Inlet for Eclipse
Sound in the eastern High Arctic, Mould Bay and the ice
island named, “Hobson's Choice,” in the western High
Arctic, and Resolute in the central High Arctic.
The Eclipse Sound studies [
Sinha and Nakawo
, 1981;
Nakawo and Sinha
, 1981] started several years before the
onset of the Radarsat project, and the goal was to develop
an understanding of the growth and decay of annual sea
ice by making continuous observations throughout the
entire growth season for a number of years. One of the
major thrusts of studies conducted, at all three locations
mentioned above, was the investigation on thermorheo-
logical and strength properties of sea ice and ice‐struc-
ture interactions. There is no room in this topic to delve
on that vast subject. This chapter is devoted to only a
fraction of the activities carried out at Mould Bay and
the Hobson's Choice ice island.
Section 5.1. discusses a series of unique field experi-
ments, conducted in the vicinities of the permanent
weather station of Mould Bay (76°14'N, 119°20'W) in the
Canadian western Arctic. The intensive study period
extended over four freezing/melting seasons during
1981-1985. It was unique in terms of the large number of
participants from Canada and the United States, variety
of data acquisitions, detailed in situ data collection, and
documentation. The most important of all was the con-
tinuous and the most comprehensive in situ observations
ever carried out on the transition of first‐year (FY) ice to
