Geology Reference
In-Depth Information
and shape coefficients, respectively. These coefficients
can be obtained using regression of field measurements.
A number of field studies of the MIZ have been con-
ducted since early 1980s. The scientific questions that
were addressed in these studies involved the following
issues: (i) Statistics of ice floes that include floe size, abla-
tion rates, melt pond occurrence and albedo influence, (ii)
the decay of ocean waves in the sea ice cover (wave ampli-
tude and spectrum), (iii) the role of ice edge eddies in ice
mass transport and melting, and (iv) the verification of
ice rheology models and ice edge kinematics against in
situ measurements. The first major experiment was the
series of the Marginal Ice Zone Experiment (MIZEX),
which were conducted over two winter and two summer
expeditions from 1983 to 1987. The first winter experi-
ment was conducted in the Bering Sea (January-March
1983). That was followed by the first summer field pro-
gram in 1983 in the Greenland Sea ice and even larger
program in the summer of 1984 (June-July). The second
winter experiment was conducted in the Greenland and
Barents Seas. Remote sensing observations were used in
that experiment. Results from this series of field studies
were published in three special issues of the
Journal of
Geophysical Research
in 1983, 1987, and 1991.
Another systematic study of a different MIZ took
place in the Labrador Sea. It modeled on MIZEX and it
was called Labrador Ice Margin Experiment (LIMEX).
An initial pilot study was carried out in the spring of
1987 [
McNutt et al
., 1988] followed by the main study in
1989 [
Raney et al
., 1989]. LIMEX was largely a remote
sensing experiment designed in anticipation of using
SAR onboard the European ERS‐1 and the Canadian
Radarsat‐1 satellites. The field work involved the air-
borne SAR system onboard the Canada Center of
Remote Sensing (CCRS) Convair 580, and the airborne
Side Looking Airborne System (SLAR) onboard the
Atmospheric Environment Service (AES) Lockheed
Electra aircraft. Two Canadian icebreakers, Terra
Nordica and Sir John Franklin provided ground truth
data. Results were published in a special issue of the
IEEE
Transactions on Geosciences and Remote Sensing
(TGRS)
in 1989 (volume 27, number 5) and in
Atmospheric Ocean
in 1992 (volume 30, number 2).
Modelling the air‐ice‐ocean interaction for improved
prediction of the MIZ is addressed in
Lee et al
. [2012].
Dumont et al
. [2011] applied a model to estimate the extent
of the MIZ and explore the model sensitivity. The model
incorporates a parameterization for the ice breaking due
to the presence of waves in ice. A scattering model is used
to evaluate the extent of the MIZ and the maximum ice
floe size. Results show that the floe size distribution is
under the direct control of waves. As expected, the size
increases toward the pack ice as waves attenuate. The
model predicts a sharp transition between the MIZ and
the inner ice pack. It concluded that if the impacting
ocean waves are sufficiently energetic and the ice is thin
enough (<2 cm), broken ice floes can spread over distance
of hundreds of kilometers. Ice thickness and incident
wave energy are the most important factors affecting the
extent of the MIZ. A decrease in the thickness and/or an
increase of storm intensity (both are expected within the
scenario of climate change impact on Arctic ice) may
increase the extent of the MIZ significantly.
2.6.4.2. Ice Edge
Ice edge is the demarcation regime between pack ice
and open water. According to the Canadian Coast
Guards, the ice edge is the trace of 10% of ice concentra-
tions. This implies that traces of ice are expected beyond
the ice edge at the ocean side. When defined using remote
sensing observations, the ice edge coincides with the
boundary of the ice extent. The latter is the demarcation
of the 15% ice concentration as determined from remotes
sensing observations (section 10.3). Prior to using the sat-
ellite technology, two types of proxies for definition of sea
ice edge were used. The first was a record of the locations
of whales since they tend to congregate near the ice edge
to feed. A record of ice edge was established since the
1930 by whalers in the Antarctic. The second was a record
of phytoplankton‐derived sulfur‐containing organic com-
pound obtained from ice cores. This was justified because
phytoplankton grows most abundantly along the edges of
the ice pack. Aside from the laborious effort involved,
these methods provide information only at a limited local
scale. The large‐scale information available through using
remote sensing imagery data has been appreciated as
breakthrough for ice edge identification.
Ice edge may be classified as compacted or diffuse or
somewhere in between. Compacted ice edge appears
with a sharp edge (clear cut) between ice and water
(Figure 2.72). It is usually caused by wind that cracks an
Figure 2.72
Compacted ice edge in the Labrador Sea March
1996 (photograph of M. Shokr).
