#69 02/2010
# 69
30 years of
OCEANOGRAPHY
WITH ARGOS
ENVIRONMENTAL MONITORING
02/2010
1
02/2010 #69
CONTENTS
30 years of OCEANOGRAPHY WITH ARGOS
4
USERS’ PROGRAMS
JCOMM
AND ARGOS:
30 YEARS
OF CLOSE
COOPERATION
By
Mathieu Belbéoch & Hester Viola
6
USERS’ PROGRAMS
SATELLITEDERIVED
MOTION
ANALYSIS
USING ARGOS
ICE BUOYS
By
8
USERS’ PROGRAMS
A SHORT
HISTORY OF
THE SURFACE
VELOCITY
PROGRAM
DRIFTER (SVP)
By
Dr. Peter Niiler
Cathleen A. Geiger
ARGOS forum is published by CLS (www.cls.fr) - ISSN : 1638-315x - Publishing Director: Christophe Vassal - Editorial directors : Marie-Claire Demmou, Anne-Marie Bréonce, Bill Woodward - Editor-in-chief: Hester Ferro <hferro@
cls.fr> - Contributed to this issue: Yann Bernard <ybernard@cls.fr>, Christian Ortega <cortega@cls.fr>, Hidefumi Yatomi <argos@cubic-i.co.jp> - Design: Couleur Citron - Printing: Imprimerie Delort certified ISO 14001.
2
USERS’ PROGRAMS
SATELLITEDERIVED
MOTION
ANALYSIS
USING
ARGOS ICE
BUOYS
By
Cathleen A. Geiger
Figure 1. Geiger straddling a crack in the sea ice.
02/2010 #69
The
polar extremes, especially the sea ice (frozen sea water) on
polar ocean surfaces, serve as the thermal regulators (air
conditioners) of the planet. Argos ice buoys play an important role in
monitoring the dynamics, thickness and extent of sea ice in the Arctic
and Antarctic, that are interconnected to recent changes in the global
climate.
From an operational perspective, sea ice features
such as leads, slip lines, cracks and ridges
play a crucial role in navigating polar waters
and maintaining offshore structures. These
discontinuities are fundamental regulators of
heat, mass and momentum transfer at the airsea interface. Hence, there is a relevant need to
understand the distribution, orientation, size and
duration of these discontinuous regions.
Challenging
As with many geophysical phenomena, tracking
the dynamics of sea ice is very challenging. This is
primarily because sea ice is one of the largest fastmoving solids on the surface of the earth with drift
rates of around ten kilometers per day occurring
across varying spatial (1-100 km) and temporal
(hours to months) scales. The spatial coverage of
this deforming field spans thousands of kilometers
covering roughly 6% of the planet’s surface at any
one time. It is also shrouded in darkness half the
year and under variable cloud cover much of the
rest of the year.
High resolution motion tracking system
To learn more
MORE ON SEDNA, APLIS, AND MOTION TRACKING
CAN BE FOUND AT THE FOLLOWING WEBSITES:
http://research.iarc.uaf.edu/SEDNA/
http://passporttoknowledge.com/polar-palooza/
pp06aplis01.php
http://passporttoknowledge.com/polar-palooza/
pp06aplis02.php
http://www.eecis.udel.edu/wiki/vims/
observations to support both scientific research
and logistics.
The availability of high spatial resolution “allseason, all-weather” synthetic aperture radar
(SAR) combined with high temporal resolution in
situ buoys provide us with observing systems to
evaluate the formation, dynamics and melting of
sea ice. Using a cascaded framework, we are able
to track sea ice drift at 400m resolution, which
is an order of magnitude greater than standard
motion products (3~5 km).
The use of Argos ice buoys
In the recently concluded APLIS’07 Ice Camp
under the Sea-ice Experiment: Dynamic Nature
of the Arctic (SEDNA) project, we have explored
new ways to effectively combine high spatial
(50m), low temporal (1-3 day) resolution active
microwave imagery and low spatial (point), high
temporal (<1 hr) resolution Argos-telemetry
GPS buoys. These efforts were aimed at refining
satellite motion products down to the scale of field
Figure 2. Location of the APLIS’07 camp.
We have applied a near-real time sea ice motion
tracking system as a decision-making tool for the
deployment of autonomous buoys. This system
helped us determine the optimal locations for
deploying GPS position (for strain-rate) and stress
buoys. A total of 12 real-time Argos-telemetry GPS
buoys were deployed in two concentrated hexagons
around our camp (fig. 1 and 2). The inner 6 buoys
were located ~10 km from the camp while the
outer 6 buoys were deployed ~70 km away.
The presence of the buoys provided a Lagrangian
reference to study the non-rigid dynamics while
they were taking place. The Lagrangian location of
the camp was tracked using continuous recording
GPS devices (some connected via Argos). Using
sequential images of the camp, we applied our high
resolution motion algorithm to identify leads and
ridges in close proximity to the camp to aid with
local measurement campaigns whenever possible.
Figure 3 shows the nested array configuration
including the 12 real-time Argos-telemetry
buoys and 5 stress buoys, overlaid on Quicklook
RadarSat-1 images. The 12 Argos-GPS buoys (6
inner + 6 outer hexagonal arrays) provided us the
much needed ground truth for validating motion
tracking algorithms and understanding multi-scale
deformation processes.
6
7
Figure 4. Group photo of APLIS’07 Ice Participants.
#69 02/2010
Actively incorporated satellite-derived
diagnostic motion analysis for field
deployments
The satellite-derived motion tracking system shown
in figure 3b is one of the new tools developed
for IPY to actively incorporate diagnostic motion
analysis for instrument deployment in a sea ice
campaign. Successes of the system included preplanning through post-diagnostics applications
of this technology to support the deployment of
autonomous buoys, manned data collection activities
and synthesis of scientific findings. Pending further
funding, this new motion tracking system can be
used as an active component in a polar observation
system. The high resolution estimate of motion
from the system provides invaluable information in
localizing dynamic features in the sea ice.
Remote sensing and telemetry
The combination of large land-based support
infrastructure and light-weight, high powered
portable equipment such as Argos ice buoys makes
today’s field work more time and cost effective
than ever before. We hope that our motion tracking
system will aid in navigation and polar searchand-rescue operations as well as the validation,
diagnosis and further development of numerical
models, especially those that might help in ice
model forecasting and heat flux calculations in
climate modeling. Ŷ
Cathleen
A. Geiger
University of Delaware
Cathleen A. Geiger is a Research Associate Professor at
the University of Delaware, USA. Her research focuses on
sea ice motion analysis. Several of her ongoing research
projects focus on research and development ideas that
both support the discovery elements of science but also
advance the development of operational tools necessary
to facilitate scientific discovery. Long-term goals include
taking advantage use of scales beyond the range of human perception to improve navigation in the polar seas,
better prepare humanity for survival in these regions,
and assess the interaction and impact of sea ice on
our world.
The APLIS’07 research described in this article was
conducted in close cooperation with: P. Clemente-Colon
(NIC), M. Engram (Alaska Satellite Facility), J. Hutchings
(UAF), C. Kambhamettu (UD/CIS), J. A. Richter-Menge
(CRREL), and M. Thomas (UD/CIS).
Figure 3. Sea Ice Experiment: Dynamic Nature of the Arctic (SEDNA) nested array. Information about sea ice position, ice
thickness, ice stress, air pressure, air, ice & water temperature were recorded and transmitted via Argos at time intervals
from 10 minutes to 2 hours. This array was deployed just prior to the “shocking” sea ice melt back in the summer of
2007. The array recorded many local events which we continue to analyze regarding small to regional-scale processes
that coincided with the large-scale ice reduction event in the summer of 2007. Panel (a) provides an overview including
the buoy positions overlaid on a RADARSAT ScanSAR B scene (red diamonds are meteorological beacons; green diamonds are GPS drifters; yellow diamond is the ice camp with ice mass balance buoy and two of the five stress sensors).
Panel (b) is an enlargement of the outer 70-kilometer-scale array with nested inner 10-kilometer-scale array including
GPS buoy drifters (green diamonds). Ice motion vectors are plotted every 6.4 kilometers. Red dots, which appear as red
lines, show discontinuities in ice motion field, calculated between two synthetic aperture radar (SAR) images on 5 and
8 April 2007. Green squares are GPS drifters clustered in groups along individual leads. Panel (c) is an enlargement of
the central region in panel (b) without ice drift vectors and discontinuities (for clarity) with the inner 10-kilometer-scale
buoy array (green circles). Blue dots are stress buoys. The green asterisk in panel (c) shows the 1-kilometer-scale array
where detailed ice thickness and ridge studies where made. Panel (d) is oblique photography taken from aircraft on 3
April by Bruce Elder (CRREL) showing ground surveyed lines each 1000 m long except leg 3 which is 730m. True north is
shown by the N and black arrow. Light detection and ranging (not shown) and electromagnetic induction (yellow lines)
aerial surveys of ice thickness were performed over all scales shown. A submarine-based upward looking sonar survey of
the 10-kilometer-scale array was also taken (not shown).
Abbreviations:
NIC = National Ice Center
UAF = University of Alaska Fairbanks
UD = University of Delaware
CIS = Computer and Information Sciences
CRREL = Cold Regions Research and Engineering Laboratory
This research was funded by the U.S. National Science
Foundation under grants NSF ARC 0612527, 0612105,
0611991, and 0612402. The U.S. Navy’s Arctic Submarine Laboratory provided access to the Applied Physics
Laboratory (APL) Ice Station 2007 (APLIS07).