Geology Reference
In-Depth Information
aspect(s) of sea ice, yet all of them draw from certain
fundamental physical or geophysical properties of sea
ice as explained below.
1.4.1. Sea Ice in Marine Navigation
Sea ice plays vital roles for naval transportation of
goods and supplies during winter months in ice‐rich
waters of many northern countries. Some major areas of
impacts are the Gulf of Bothnia for Sweden and Finland,
Gulf of Finland, Northern Sea Route, Okhotst Sea for
Russia, the Baltic Sea for Eurasia, the Gulf of Sr.
Lawrence and Labrador Sea for Canada, and the Bohai
Bay for China. Safe marine navigation in these water
bodies requires timely information on ice accompanied
with meteorological data. Technical products to map ice
extent, types, strength, and surface features are produced
regularly by a few ice centers in northern countries to
serve marine navigation. Charts are generated based on
interpretation of remotely sensed images. High‐resolu-
tion charts cover local areas such as fjords, straits, and
marginal ice zones. Medium‐resolution charts cover areas
that are used in determining ship routes. Regional fore-
cast and regional ice charts provide ice extent, concentra-
tion, motion, and perhaps thickness.
In Canada, the Canadian Coast Guard (CCG) provides
recommendations on safe navigation routes as well as
escort services to ships transiting Canadian ice‐covered
waters. The CCG receives ice information from a few
sources, of which the CIS of the federal department is the
prime. Icebreaker superintendents have the updated condi-
tions of the prevailing ice conditions and the anticipated
trend of ice motion. Therefore, they are well positioned to
provide reasoned advice regarding the best routes for the
ships to pursue. Usually, the masters of the ship report to
the CCG before entering an area of ice‐covered water.
This ensures a continuing monitor of the ship's position by
CCG operators. If icebreaker support becomes necessary,
it can be provided with minimum delay.
Records of sea ice concentration and thickness
obtained from remote sensing data during the past two
decades have confirmed a trend of Arctic ice cap thinning
and shrinking. This may lead to opening a seaway con-
necting the Atlantic and the Pacific Oceans for marine
navigation for a longer time or eventually for the entire
year. The dream of many early European explorers,
which occupied their adventures for more than 400 years,
may soon be realized by the merit of climate change. The
economic impact of this scenario is significant. Ice‐free
future sea routes will reduce the number of days of
marine transportation between Europe and Asia and
double the vessel fuel efficiency. More importantly, com-
mercial marine transportation will have more access to
natural resources in the Arctic. Two routes are expected
Figure 1.6
A tilted iceberg in Baffin Bay, June 1984, revealing
underwater bulbous bow extension of the hull, like modern
ships (photo by N. K. Sinha, unpublished).
icebergs in Baffin Bay and Labrador Sea ranges between
10,000 and 40,000. The Canadian Ice Service (CIS) pro-
duces charts of icebergs in the Canadian east coast water
south of 60°N. The information is mainly based on visual
observations from ships and aircrafts but also occasion-
ally obtained from satellite imagery.
Icebergs are fascinating to watch. An example of a
nontabular iceberg in northern Baffin Bay is shown in
Figure 1.6. It can provide interesting lessons to naval
architects regarding Mother Nature's efficient design of
bulbous bows. A bulbous bow, in the language of naval
architects, is an extension of the hull just below the water-
line. It has many subtle shape variations, but it's basically
a rounded front portion that flares out slightly as it blends
into the traditional displacement hull construction. These
forward protrusions are about twice as long as the width
of the base. They would usually not extend forward past
the top of the bow. This can be seen in Figure 1.6 also
by imagining the iceberg to its original position before
tilting. The basic principle of bulbous bow is to create a
low‐pressure zone to eliminate the bow wave and reduce
drag. Hulls built with bulbous bow sections are common
today for seagoing ships. Under certain conditions,
depending on speed and sea state, the bulbous bow is very
efficient at redirecting forces of hydrodynamic resistance
and drag. Ice breaking ships do have a special shape of
bulbous bow that is heavily reinforced to withstand the
pressures induced by sea ice.
1.4. sea ice in researcH and
operational disciplines
Sea ice is an important component in a few study and
application disciplines including navigation, physics,
climatology, meteorology, oceanography, marine biol-
ogy, and marine and offshore structural engineering.
Each community has developed its interest in certain
