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Moorings and Current Meters
Ellen Martinsek
EPS 131
December 14, 2005
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Outline
• Moorings– Purpose– Deployment & Recovery– Specific Projects
• Current Meters– Different Methods of Measuring Current– Acoustic Doppler Measurements– Applications
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Moorings
Connection between water surface and instrumentation in the ocean below the surface
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Deployment & Recovery
• Difficult since the mooring cable breaks if moved too quickly
• Need to keep instruments and data safe
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Back to WHOI
Sub-Surface Mooring Operations Group: over 90% instrument and data recovery
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North Pole Environmental Observatory
Retrieving a mooring that has been collecting oceanographic data from the Arctic Ocean for a year at the NSF’s North Pole Environmental Observatory
Photo Credit: Peter West/National Science Foundation
• First year-round mooring at the North Pole retrieved in April 2002
• Purpose: to see how the Arctic Ocean influences global climate
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Monterey Ocean Observing System (MOOS) test mooring
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MOOS test mooring
instruments
“S” bend
float
Power source (on float)
•Biggest engineering problem: creating a cable that can stay intact!
•11 days after the first deployment (December 3, 2002) the cable snapped had to redesign it before finally redeploying on April 23, 2004.
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Measuring Current …
• Mechanical current meters
• Electromagnetic current meters
• Acoustic Travel Time current meters
• Acoustic Doppler measurements
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Acoustic Doppler measurements
• Why sound is good to use
• The Doppler Effect
• Back Scatter Sonar – How It Works
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Acoustic Doppler Current Profiler (ADCP)
RDCP 600 (by Aanderaa) – 600kHz self-recording Doppler Current Profiler
Constant frequency pings transmitted
Ricochet off suspended particles and reflect back
Calculate speed of particle and surrounding water using Doppler shift
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Applications of Current Profiling
• Climatic Research
• Ports and Harbors
• Fish Farming
• Pollution Control
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Summary
• Moorings serve as a connection between the water surface (which itself is connected via satellite to labs onshore) and instruments in the ocean
• An important example of such instrumentation is the current profiler; in particular, the ADCP
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References• http://www.pmel.noaa.gov/vents/nemo1999/logbook/cal062399/• http://www.mbari.org/news/homepage/2004/moosII.html• http://www.whoi.edu/institutes/occi/currenttopics/
ct_oms_stationw.html• http://www.washington.edu/newsroom/news/2002archive/05-
02archive/npfactsheet.html• http://www.antarctica.ac.uk/BAS_Science/programmes2000-2005/
DYNAMOE/Moorings/index.html• http://walrus.wr.usgs.gov/mcgaw/depmoor.html• http://pulson.seos.uvic.ca/lecture.html• http://www.soc.soton.ac.uk/OED/gxg/Single_Point_CMs.pdf• http://www.aanderaa.com/docs/RDCP_600_D343.pdf• http://www.nsf.gov/od/lpa/news/03/ma0329.htm