D.G. BARBER, A. THOMAS, AND T.N. PAPAKYRIAKOU
In recent years, Earth system scientists have begun to use remotely sensed data to study
the planet through complex interactive units. With the advent of the new era of operational microwave remote-sensing sensors (e.g. ERS-l, ERS-2, JERS-l, RADARSAT,
SSM/I), it is now possible to obtain a systematic dataset of the marine cryosphere without concern for cloud cover or solar illumination. It is important that an understanding of the relationships between microwave interaction and climate state variables be
developed so that fields of radiative and conductive flux conditions may be generated
for subsequent use in numerical process models. A basic tenet of this type of observational system is that linkages between the energy regime of the volume and its electrical characteristics may be exploited as a means of estimating the former by the way in
which microwaves interact with the latter.
The main problem we face in studying processes operating within the marine cryosphere is the fact that the surface and volume are constantly changing. Ice ablation and
accretion are directly related to the variable atmospheric and hydrospheric forcing created by global general circulation patterns. Mass fluxes also affect ice growth and ablation through deposition of a layer which has low conductivity for both thermal and
radiative energy. That component of the energy which is transmitted across the upper
and lower interfaces is available within the volume to change the physical and electrical characteristics, which then cause changes in the flux proportions being reflected,
transmitted or absorbed. This feedback mechanism creates a fundamental link
between the physical properties of the marine cryosphere and the nature of electromagnetic interaction with the physical and electrical properties of the interface.
In this chapter we present three sections through which we document our current
understanding of how synthetic aperture radar (SAR) may be used in estimating components of the surface energy balance within the marine cryosphere. In the first, Sect.
3.2 (The Marine Cryosphere), we state the scientific rationale for this work and review
the important characteristics of a seasonally evolving marine cryosphere from the perspective of its dielectrical, energy balance and microwave-scattering properties. This
review sets the stage for Sect. 3.3 (Building Statistical Relationships), in which we present various statistical linkages between the time series evolution of the microwave-scattering coefficient and components of the surface energy balance. These statistical relationships are then exploited utilizing a variety of image-processing approaches in Sect.
3.4 (Generating Image Products). We conclude the chapter with a description of the future
directions of this work and a description of how these results are being implemented in
large-scale operational processing programs such as the Radarsat Geophysical Processor System (RGPS) and the Ice Information Services of Environment Canada.
3.2
The Marine Cryosphere
We consider sea ice as a volume interface between an overlying atmosphere and an
underlying hydrosphere; the pertinent physical interconnections can be rationalized
within the atmospheric and hydrospheric sub-components of the Arctic system.
Hydrologically, sea ice represents a storage volume for fresh water, primarily in the form
of ice ridges, multiyear ice and the snow cover on all ice types. The freshwater export
of sea ice from polar to temperate latitudes is a significant parameter in the global hydrologic cycle (Prinsenberg 1988).
In recent years, Earth system scientists have begun to use remotely sensed data to study
the planet through complex interactive units. With the advent of the new era of operational microwave remote-sensing sensors (e.g. ERS-l, ERS-2, JERS-l, RADARSAT,
SSM/I), it is now possible to obtain a systematic dataset of the marine cryosphere without concern for cloud cover or solar illumination. It is important that an understanding of the relationships between microwave interaction and climate state variables be
developed so that fields of radiative and conductive flux conditions may be generated
for subsequent use in numerical process models. A basic tenet of this type of observational system is that linkages between the energy regime of the volume and its electrical characteristics may be exploited as a means of estimating the former by the way in
which microwaves interact with the latter.
The main problem we face in studying processes operating within the marine cryosphere is the fact that the surface and volume are constantly changing. Ice ablation and
accretion are directly related to the variable atmospheric and hydrospheric forcing created by global general circulation patterns. Mass fluxes also affect ice growth and ablation through deposition of a layer which has low conductivity for both thermal and
radiative energy. That component of the energy which is transmitted across the upper
and lower interfaces is available within the volume to change the physical and electrical characteristics, which then cause changes in the flux proportions being reflected,
transmitted or absorbed. This feedback mechanism creates a fundamental link
between the physical properties of the marine cryosphere and the nature of electromagnetic interaction with the physical and electrical properties of the interface.
In this chapter we present three sections through which we document our current
understanding of how synthetic aperture radar (SAR) may be used in estimating components of the surface energy balance within the marine cryosphere. In the first, Sect.
3.2 (The Marine Cryosphere), we state the scientific rationale for this work and review
the important characteristics of a seasonally evolving marine cryosphere from the perspective of its dielectrical, energy balance and microwave-scattering properties. This
review sets the stage for Sect. 3.3 (Building Statistical Relationships), in which we present various statistical linkages between the time series evolution of the microwave-scattering coefficient and components of the surface energy balance. These statistical relationships are then exploited utilizing a variety of image-processing approaches in Sect.
3.4 (Generating Image Products). We conclude the chapter with a description of the future
directions of this work and a description of how these results are being implemented in
large-scale operational processing programs such as the Radarsat Geophysical Processor System (RGPS) and the Ice Information Services of Environment Canada.
3.2
The Marine Cryosphere
We consider sea ice as a volume interface between an overlying atmosphere and an
underlying hydrosphere; the pertinent physical interconnections can be rationalized
within the atmospheric and hydrospheric sub-components of the Arctic system.
Hydrologically, sea ice represents a storage volume for fresh water, primarily in the form
of ice ridges, multiyear ice and the snow cover on all ice types. The freshwater export
of sea ice from polar to temperate latitudes is a significant parameter in the global hydrologic cycle (Prinsenberg 1988).