Moorings and Current Meters

Ellen Martinsek

EPS 131

December 14, 2005

Outline

• Moorings– Purpose– Deployment & Recovery– Specific Projects

• Current Meters– Different Methods of Measuring Current– Acoustic Doppler Measurements– Applications

Moorings

Connection between water surface and instrumentation in the ocean below the surface

Deployment & Recovery

• Difficult since the mooring cable breaks if moved too quickly

• Need to keep instruments and data safe

Back to WHOI

Sub-Surface Mooring Operations Group: over 90% instrument and data recovery

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

Monterey Ocean Observing System (MOOS) test mooring

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.

Measuring Current …

• Mechanical current meters

• Electromagnetic current meters

• Acoustic Travel Time current meters

• Acoustic Doppler measurements

Acoustic Doppler measurements

• Why sound is good to use

• The Doppler Effect

• Back Scatter Sonar – How It Works

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

Applications of Current Profiling

• Climatic Research

• Ports and Harbors

• Fish Farming

• Pollution Control

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

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