Geology Reference
In-Depth Information
support development of remote sensing applications of
sea ice. The Canadian Space Agency made the data from
the Canadian satellite Radarsat suitable and available for
sea ice applications. A few academic institutes have
expanded their research programs on several geophysical
and climatic aspects of sea ice and its remote sensing
applications. Among them is the University of Manitoba's
Centre for Earth Observation Science, University of
Calgary Department of Geography, and University of
Waterloo Department of Geography and Environmental
Management. Research and operational work from these
and other Canadian academic institutes is quoted fre-
quently in the topic.
Materials related to physics of ice are presented in
Chapters 2-6 while remote sensing materials are pre-
sented in Chapters 7-10. Chapter 2 addresses the initial
formation and growth of sea ice with its two phases of
lateral and vertical growth. It then presents models of
ice growth to estimate its rate under different atmos-
pheric, oceanic, and snow effects. This is followed by
discussions on the processes of brine entrapment as the
freezing proceeds at the ice‐water interface and the sub-
sequent brine drainage from the ice mass during the
first year of its life. Forms of ice deformation, decay,
and aging are also introduced with geometric charac-
terization of some forms. The chapter concludes with a
section on sea ice classes and regimes. This includes a
brief account of commonly known regimes; namely
polynyas, pancake ice, marginal ice zone, and forms of
floating ice of land origin.
Chapter 3 presents data on basic physical properties of
sea ice and derivation of simple models to determine
elected parameters such as volume fractions of sea ice
constituents and the dielectric constant of the two‐phase
sea ice composition. Typical values of key physical param-
eters are given. The chapter addresses three basic physical
properties of sea ice (salinity, density, and temperature) as
well as relevant thermal properties (conductivity and heat
of fusion). The dielectric constant is presented in details
because of its relevance to remote sensing.
Chapter 4 presents detailed information on polycrystal-
line structures of freshwater lake and river ice and sea ice.
It starts with general structural features of ice and relates
the information to other material at high temperature.
A number of basic terms and definitions related to the
polycrystalline aspects of ice that are used in this topic are
introduced. At the core of this chapter is the crystallo-
graphic classification of natural sea ice. This is the key
information for the interpretation of texture of the ice,
from which information about ice growth conditions can
be inferred. Many examples of age‐based sea ice types and
their characteristic features are presented by photographs
of thin sections. Information that can be retrieved from
these data is presented in the last section (e.g., geometric
characteristics of crystals, brine pockets, and air bubbles).
Chapter 5 is about two major field experimental
programs, conducted in the 1980s in the western Arctic of
Canada. The first is the Mould Bay experiment that
marked the beginning of the field programs in support
for the development of the Canadian Radarsat project.
The study of sea ice from first‐year to second‐year type
and the continuation of the growth of first‐year ice under
the second‐year ice are two unique achievements from
this program. The second was a program conducted on
an ice island that broke away in 1982 from the East Ward
Hunt ice shelf in Ellesmere Island, Canada. Only limited
information from both of these experiments has been
published. Thus this topic is providing an opportunity to
disseminate technical as well as human aspects of con-
ducting long‐term experiments on sea ice in the Arctic.
Chapter 6 is dedicated to the methods developed for
revealing microstructural characteristics of sea ice and
performing forensic type of investigations. Following an
introduction to polarized light, polarizing sheets, large
field‐of‐view polariscopes, and the birefringent properties
of ice, it moves on to present detailed techniques for pre-
paring thin sections of ice and snow. Special emphasis is
given to the double‐microtoming technique (DMT) that
avoids the use of any warm‐to‐touch glass plates or
surface melting—hence the best choice for saline ice. The
procedures for examining and photographing thin
sections under polarized and scattered light, or their com-
binations, are then presented. The chapter is concluded
with descriptions of thermal and chemical etching, and
the dual process of etching/replicating (DPER) technique
in conjunction with scanning electron microscopy (SEM)
for examinations of subgrain boundaries and substruc-
tures involving line defects or dislocations. These are not
possible with the traditional polarized lights methods.
Moreover, these procedures can be performed in the field
and were actually used by the authors in the Arctic (using
tents and make‐shift shelters), and many examples from
these field experiments are presented in this topic. It is
stressed that microstructural analysis should be performed
in the field when the ambient conditions are cold (prefer-
ably below −15 °C) and immediately after recovering the
samples from the sea.
Chapter 7 addresses a few concepts of remote sensing
relevant to sea ice applications and particularly its
parameter retrieval. The breadth of the material in this
chapter is designed to appeal to researchers and users of
remote sensing data who want to develop quick acquaint-
ance with scientific issues that are outside their domain
of experiences. After a historical synopsis of satellite
remote sensing for sea ice, the chapter includes sections
on electromagnetic wave properties and processes.
Principles of optical, thermal, and microwave remote
sensing are introduced in separate sections. More focus is
placed on the imaging radar sensing since this is the
prime data source for operational sea ice monitoring.
