Bottom-Anchored Mooring

In April 2006, the fifth NPEO bottom-anchored mooring was recovered and a sixth deployed, each anchored more than 4000 meter deep to the abyssal plain near the North Pole. Measurements include ice thickness and drift, water temperature and salinity, and current speed and direction, from near the surface to great depths. (Diagram) Each instrument records internally for at least one year. Data from the first five years' moorings was successfully recovered and is being analyzed. Other automated measurements were added beginning in 2005, including concentrations of nutrients and a variety of other biological tracers.

Measurement of the precise ocean depth is critical to ensure the Upward Looking Sonar at the top of the mooring is just 50 meters beneath the drifting ice. Recovery of each mooring from beneath the ice is a logistically complex operation, requiring the ability to return to a precise location and, in most cases, divers to go beneath the ice.

The intent is to maintain each year's mooring at the same position. However, slight differences are operationally unavoidable, because of the ice drift during the one-to-three day period between the release of the old mooring and actual deployment of the new one. Closeness to the Pole accounts for the wild-appearing changes in longitude.

Data from the first three mooring years may be obtained via FTP at this website.