The
world's sea level has increased by
2mm/year over the past century, it
is predicted to rise between 50 and
70 cm within the next hundred years.
The threat of flooding from the thermal
expansion of the ocean and melting
of mountain glaciers can be devastating.
With the premise that the main contributing
factors of the sea level rise come
from Greenland and Antarctica, a program
to monitor the mass balance of the
Greenland ice sheet was initiated by
NASA in 1993 known as the PARCA (Program
for Arctic Regional Climate Assessment)
initiative.
The
Radar Systems and Remote Sensing
Laboratory (RSL) at the University
of Kansas has played a significant
role in PARCA by collecting and monitoring
the mass and overall ice dynamics
of the ice sheets in Greenland with
the use of an ice penetrating radar.
The University of Kansas developed
the Coherent Antarctic Radar Depth
Sounder (CARDS) in the 1980s for
the use of data collecting in Antarctica.
However, there were several shortcomings
with this system which resulted in
less than optimum performance. As
a result, this system was redesigned
and rebuilt in 1996. Although the
Improved Coherent Antarctic Radar
Depth Sounder (ICARDS) eliminated
previous problems faced by CARDS,
it was oversized. This led to the
development of the Next-Generation
Coherent Radar Depth Sounder (NG-CORDS)
system, which is an
airborne radar that uses complementary
Surface-Acoustic-Wave (SAW) devices
for both signal generation and matched
filtering of a linear chirp wave
form. NG-CORDS uses Radio Frequency
Integrated Circuits (RFICs) and Microwave
Monolithic Integrated Circuits (MMICs)
with 12-bit A/D converters instead
of the two 8-bit A/D converters previously
used by CARDS. Recent field experiments
have used the ACORDS (Advanced COherent
Radar Depth Sounder) which is a more
compact design. ACORDS is an enhanced
version of the NG-CORDS that incorporated
the latest digital technology in
the radar system. It is unique because
of its ability to generate the transmit
waveform digitally and uses band
pass sampling and digital pulse compression
techniques. By having the improved
Radar Depth Sounder, data has and
continues to be collected from Greenland’s
ice sheets. These data acquisitions
have to be obtained periodically
to provide solid measurement of the
ice and its behavior. Even though
there are some challenges remaining
with the ACORDS system, such as surface
clutter due to heavy crevassing masking
the bedrock return and signal loss
due to increased melting in some
outlet glaciers, over 90% of the
collected data were of good quality.
