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Arctic Leads Experiment

Project Description
The Lead Experiment (LeadEx) was a experiment sponsored by the Office of
Naval Research (ONR) to study the crack-like openings called leads
that are created by the deformation of Arctic pack ice. The study was
conducted by a group of scientists from various institutions and
disciplines to clarify the effect of open leads on the polar ocean and
atmosphere and to further understanding of the role of polar regions
on climate and global change.
The LeadEx was conducted during March and April 1992 in the Beaufort
Sea approximately 300 km north of Deadhorse, Alaska.
Leads range from a few meters to thousands of meters wide and have
long been considered important to the thermodynamics of the polar
regions. Leads can account for nearly half of the total heat flux from
the ocean (Badgley, 1966) because the lead exposed relatively warm
water to the cold atmosphere. Leads have a major effect on the
salinity of the ocean mixed layer.
The LeadEx program began in 1990 with funding from the ONR Accelerated
Research Initiative. Initial studies were made at the University of
Arizona and the Applied Physics Laboratory at the University of
Washington.
The main experiment began on March 16, 1992 with the establishment of
a base camp that drifted generally westward until the program ended on
April 25, 1992. Weather forecasts and remote sensing data were
provided by the LeadEx weather center at the National Weather Service
(NWS) in Anchorage, Alaska. The Naval Research Laboratory (NRL) at
Monterey, CA transmitted mesoscale meteorological model forecasts of
wind, temperature, moisture, and cloud height to the LeadEx weather
center twice daily. Near-real-time high-resolution satellite data from
NOAA satellites and DMSP satellites were also made available.
Huts and equipment were deployed from the main base camp to four sites
called Lead 1 - Lead 4. Most of the data were gathered at Lead 3 and 4
since Leads 1 and 2 were closed soon after the sites were occupied.
Helicopter and research aircraft made numerous oceanographic and
meteorological measurements.
Meteorological effects were measured primarily by the Wave Propogation
Laboratory (WPL) in Boulder, CO. WPL instrumentation included sonic
anemometers, pyranometers and pyrgeometers, and 6.5 kHz SODARs.
Rawinsondes were launched by WPL to support atmospheric soundings
conducted by the Naval Postgraduate School (NPS) in Monterey, CA. The
NOAA Pacific Marine Environmental Laboratory (PMEL) and NPS deployed
drifting buoys.
Several aircraft programs were conducted using the University of
Washington Convair C-131A and a DeHavilland Twin Otter (DHC-6). The
group measured atmospheric temperature, water vapor concentrations and
biogenic emissions of dimethylsulfide (DMS) from leads. A
high-resolution, down-looking infrared thermometer was used on both
aircraft.
Growth rate of ice in the leads was measured by groups from PSC using
freeze-in buoys. Physical properties of the ice was measured by the
Cold Regions Research and Engineering Laboratory (CRREL).
Remote sensing applications for ice studies was conducted by the
Department of Atmospheric Sciences at the University of Washington to
determine microwave and infrared brightness temperatures of thin ice
in the freezing leads and selected first-year ice. Observations were
made at 6.7, 10, 18.7, 37 GHz and 10 microns. A team from the
Environmental Research Institute of Michigan (ERIM) measured radar
backscatter at multiple frequencies, polarizations, and angles
simultaneously. A group from Williamson and Associates measured
thermally induced stress in the lead ice.
Oceanographic measurements included profiles of conductivity,
temperature, turbulent shear, and acoustic backscatter. The McPhee
Research Company (MRC) used a mast of multiple sensors to obtain time
series of mean velocity, temperature, and salinity and turbulent
fluxes. PSC used an untethered Autonomous Conductivity Temperature
Vehicle (ACTV) which carried a conductivity-temperature-depth (CTD)
probe. A specialized pontoon boat from the Oregon State University was
used to measure the microstructure of leads. A group from Scripps
Institution of Oceanography used a sector-scan, multibeam, Doppler
sonar.
Reference:
Badgley, F.J. 1966. 'Heat Budget at the surface of the Arctic Ocean',
in 'Proceedings on the Symposium on the Arctic Heat Budget and
Atmospheric Circulation', ed. by J.O. Fletcher, pp. 267-277, Rand
Corporation, Santa Monica, CA. (Avail as PB-182433 from Nat. Tech.
Inf. Serv., Springfield, VA)
Morison, J.H., M.G. McPhee, T. Curtin, and C.A. Paulson. 1992. 'The
oceanography of winter leads', J. Geophys. Res., Vol. 97, 11,199.
Morison, J. 1993. 'The LeadEx Experiment', EOS, Transactions of the
American Geophysical Union (AGU), Volume 74, Number 35, August 31,
1993, pp. 394, 396-397.
Contacts:
Dr. James Morison
Polar Science Center
Applied Physics Laboratory
University of Washington
1013 NE 40th Street
Seattle, WA 98105
Phone: 206-543-1394
FAX: 206-543-6785
Email: Internet > morison@apl.washington.edu
OMNET > j.morison
Data Availability:
The LeadEx data is being made available via anonymous FTP from the
Polar Sciences Center, Applied Physics Laboratory, University of
Washington:
FTP nansen.apl.washington.edu
login as anonymous
enter email address as password
cd to leadex
Only a small set of data has been made available at this time, and
additional datasets will be added to the site as they become
available.
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