Concept information
Preferred term
LEADEX
Definition
- 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. (en)
Broader concept
- J - L (en)
URI
https://gcmd.earthdata.nasa.gov/kms/concept/5fbb5ec6-85db-49ad-9a2f-3089a644febd
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