Geology Reference
In-Depth Information
The chapter provides also a brief account of radiative
processes in the atmosphere, ocean, and snow on sea
ice. These three media contribute to the satellite observa-
tions of sea ice. The material in this chapter provides
sufficient background to facilitate comprehending the
information presented in the next chapters.
Chapter 8 presents data sets on radiative properties
and satellite observations of sea ice, its snow cover, and
surrounding open water. These include radar backscatter,
microwave brightness temperature, visible and near‐
infrared reflectance and albedo, emissivity, and penetra-
tion depth in the microwave spectral region. Data are
arranged according to the commonly used age‐based ice
types and for snow under different physical conditions
(wetness, density, and grain size). Limited information is
provided to explain the overlap between measurements
from different ice types or snow cover. Most of the data are
obtained from several satellite observations but airborne
and ground measurements are also used. No attempt has
been made to explain discrepancies (if they exist) between
data sets of the same parameter from different sources.
The data can serve as benchmarks to guide the process of
retrieval of ice parameters from remote sensing data.
Methods of retrieval of surface features of sea ice are
presented in Chapter 9. The features include surface
deformation (ridges, rubble ice, and brash ice between
floes), leads within the ice cover, forms (stages) of surface
melt, and frost flowers cover on thin ice. For each feature
the most suitable sensors are identified and the most com-
mon methods of retrieval are described. Geometrical
characterization of ice ridging is included. The charac-
terization of leads in terms of their geometries and
the wind conditions that generate them is presented.
Procedures for determining the onset of surface melting
and its advanced phases using optical, passive microwave,
and imaging radar data are also described. The advantage
of combining observations to retrieve surface features is
demonstrated. The chapter concludes with a presentation
on frost flowers on thin ice surface in relation to the
conditions of their formation and their effect on
modulating the received radar backscatter.
Chapter 10 presents methods for the retrieval of seven
sea ice parameters: ice types, concentration, extent, thick-
ness, surface temperature, snow depth, and ice displace-
ment and velocity. Whenever possible, methods for each
parameter are grouped according to the type of observa-
tion: optical, thermal infrared, passive microwave, and
radar. Ice type is an important operational parameter,
and it can be retrieved from all categories of remote sens-
ing observations. Special focus is placed on retrieval of
ice concentration because this has been the most suc-
cessful retrievable parameter from remote sensing obser-
vations. Detailed descriptions of four methods that
represent four different retrieval approaches are included.
As for the rest of the seven parameters, the most com-
monly used retrieval methods are presented. Once again,
more coverage is given to the ice thickness retrieval. Some
critical issues that affect the accuracy of retrieval of all
parameters, especially ice concentration, are presented.
The information in this chapter aims at understanding
the potential and limitations of the ice parameter retrieval
algorithms.
Chapter 11 presents a brief historical account showing
the development of interest in Arctic sea ice in Canada
and a synopsis of the Canadian ice monitoring program,
which is currently operated by the Environment Canada
(the federal Department of the Environment). The his-
torical narration focuses on the turning point when sea
ice became a service offered by the federal government
after it had been just an issue that had to be “attended to”
for a few centuries. The material on operational ice moni-
toring program and the examples of operational ice
charts products from CIS serve as supporting material to
a few parts throughout the topic. In general, this chapter
adds another human dimension to the sea ice material in
this topic.
