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A combined remote sensing/modelling approach for the retrieval of sea ice thickness in East Antarctica


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Hungria, Clemente Soares 2002 , 'A combined remote sensing/modelling approach for the retrieval of sea ice thickness in East Antarctica', PhD thesis, University of Tasmania.

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Sea ice thickness is an essential parameter for the estimation of energy, mass and
momentum exchange and sea ice mass balance in the Southern Hemisphere. In situ
methods of estimating the ice thickness distribution cannot provide the necessary
areal coverage, while the coarse resolution of numerical models is unsuitable for
parameterising small-scale processes. Remote sensing technology has the potential to
address these issues of areal coverage and spatial resolution.
A procedure for estimating the distribution of sea ice thickness using remote sensing
data from the Advanced Very High Resolution Radiometer sensor is presented. This procedure is based on the method
described by Yu and Rothrock [1996] for Arctic sea ice and relies upon the
assumptions a) that the surface temperature of thin sea ice is closely related to its
thickness and b) that there is a linear vertical temperature gradient across the
recently-formed sea ice. Considerable modifications have been made to the Yu and
Rothrock method in order to apply it to Antarctic conditions.
Broadband albedo, ice/snow surface temperature and near-surface air temperature
were estimated for cloud-free AVHRR pixels identified by an "expert system"
algorithm. These variables were used as inputs to a thermodynamic model to
estimate ice thickness for two areas of the East Antarctic sector during the austral
winter of 1995 and spring of 1996. The sensitivity of the model was examined with
reference to the estimation of near-surface air temperature, effective thermal
conductivity of snow, bulk transfer coefficients for heat and evaporation and the
calibration of the satellite sensor's gain.
Resultant ice thickness maps and frequency distribution histograms were compared
with concurrent ship-based sea ice observations and digital aerial photography.
Comparisons were also made with historical ("climatological") data including drill
hole measurements, ship-based observations and Special Sensor Microwave/Imager-derived sea ice extent data.
In spite of the relative lack of concurrent data to validate the results, the analysis of
the 1996 data showed good agreement with ship-based observations from previous
years and with estimates of areal coverage obtained from passive microwave data.
The ice thickness distribution in the Prydz Bay area for the months of October and
November is also consistent with ice drift patterns, regional iceberg distribution and
ocean circulation described in the literature for that area. Important by-products of
the method proposed are maps of ice/snow surface physical temperature and albedo.
Comparisons with near-contemporary digital aerial photography demonstrated the
procedure's ability to resolve features such as icebergs and large floes and the
transition between areas of open water and/or thin ice and areas of thick, snow covered
ice. The model's response to the presence of more than one surface type
within a single pixel depends on their radiometric characteristics and relative
concentration. The small number of images from August 1995 precluded a more
detailed analysis, but it was clear that the larger solar zenith angles that occur in
winter significantly affected the result. In spite of these problems, it was possible to
interpret the thickness distribution in terms of the meteorological and geophysical

Item Type: Thesis - PhD
Authors/Creators:Hungria, Clemente Soares
Keywords: Sea ice, Sea ice
Copyright Holders: The Author
Copyright Information:

Copyright 2002 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 2002. Includes bibliographical references

Permission for OA received from author 10/3/15 IA

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