Doktora Yeterlilik Tez Özeti
The University of Texas at San Antonio, 2010
ESTIMATION OF ANTARCTIC SEA ICE PROPERTIES USING SURFACE AND
SPACE BORNE DATA
Sea ice is a fundamental component of the Earth‟s systems that cannot be
ignored in the large scale environmental predictions of future climate conditions.
Sea ice is a complex material and has major influences on global climate with its
large maximum extent and seasonal change. In contrast, sea ice is also
vulnerable and sensitive to global climate change. The Antarctic sea ice zone
remains one of the least known regions of the Earth‟s surface. Both passive and
active microwave remote sensing have provided useful information about sea ice
properties in both Polar Regions and their trends of change over 30 years.
Satellite laser and radar altimetry measurements are nascent technology and
have been used less than a decade. For Antarctic sea ice, however, work on
computing ice properties from satellite algorithms are still in a developmental
and quasi-validated state. In this research, remote sensing validation based on
comparisons with surface based data has been done for quantitative monitoring
of the ice properties. Various satellite products consisting of passive microwave,
active microwave, and high resolution visible imagery were used and compared
with in-situ measurements collected during scientific Antarctic cruises, conducted
during International Polar Year (IPY) 2007 - 2008. In-situ measurements were
used as ground truth data to validate satellite measurements, in terms of looking
at sea ice concentration, sea ice extent, and sea ice types. In addition, National
Ice nter (NIC) ice edge data was used to compare and compliment satellite and
in-situ measurements. In chapter 5, data sets on small-scale profiles on surface
elevation gathered from ships were standardized. This data used to provide a
quantifiable method for observing sea ice, from all regions of the Antarctic sea
ice zone to develop relationships that test existing remote sensing algorithms,
evaluate alternative algorithms and provide error estimates on sea ice thickness
derived from existing algorithms.
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Chapter 2 presents the comparison of ice extent/ice edge data from the NIC and
the AMSR-E (Advanced Microwave Scanning Radiometer - Earth Observing
System) passive microwave products using the Antarctic Sea Ice Process and
Climate (ASPeCt) ship observations from the Oden expedition in December 2006
as ground truth to verify the two products during Antarctic summer. Ice edge
location comparison has also been made between the two data sets, ship ice
observations and NIC daily ice edge products. NIC analyses rely more heavily on
high resolution satellite imagery such as active radar and visible imagery when
visibility (clouds) allows. From these comparisons, a quantitative estimate of the
differences in summer ice extent between the two remotely obtained products,
AMSR-E and NIC ice edge, over the larger West Antarctic sea ice zone, has been
obtained.
Chapter 3 evaluates the comparison of ASPeCt ship based observations
(conducted during Sea Ice Mass Balance in the Antarctic (SIMBA) 2007 Antarctic
cruise) with coincident satellite active and passive microwave data. We combined
visual ship-based observations of sea-ice and snow properties during SIMBA with
coincident active and passive microwave satellite data with the aims to a) derive
typical radar backscatter ranges for observed sea-ice es and ice type mixtures,
b) improve our knowledge about the radar backscatter of different ice types in
the Bellingshausen Sea at early-middle spring, c) interpret AMSR-E snow depth
over these ice types, and d) identify the potential of the investigated active
microwave signatures for a synergy with AMSR-E data to eventually improve the
snow depth retrieval.
Chapter 4 presents the validation of remote sensing measurements of ice extent
and concentration with ASPeCt ship-based ice observations, conducted during
the SIMBA and the Sea Ice Physics and Ecosystem eXperiment (SIPEX)
International Polar Year (IPY) cruises (Sept-Oct 2007). First, the total sea ice
cover around the entire continent was determined for 2007-2008 from Advanced
Microwave Scanning Radiometer - Earth Observing System (AMSR-E) passive
microwave and National Ice Center (NIC) charts. Second, Antarctic Sea Ice
Processes and Climate (ASPeCt) ship observations from the SIMBA and SIPEX
expeditions in the austral end of winter – beginning of spring 2007 are used as
ground truth to verify the AMSR-E sea ice concentration product provided by
both the Enhanced NASA Team Algorithm (NT2) and Bootstrap Basic Algorithm
(BBA).
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Chapter 5 presents supplemental analysis related to the baseline thickness of
Antarctic sea ice on a circumpolar basis from field measurements. In this part,
our objectives were (1) Develop statistical relationships between surface
elevation (snow freeboard), ice elevation (ice freeboard) and mean sea ice
thickness using previous and newly obtained Antarctic sea ice profiles and
examine these relationships for any consistent regional trends, (2) Derive sea ice
thickness from profile elevations, using buoyancy equation, to determine error
estimates compared to measured thickness; compare error estimates between
the thicknesses derived using statistical relationships bjective 1) and buoyancy
theory where the additional term for the density of the slush layer is needed,
when surfaces are flooded from snow loading.
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