April 2002 Scientific Program

The three components of the North Pole Environmental Observatory shared the Twin Otter skiplane and AStar 350 helicopter to complete their planned activities.

  • Bottom-anchored mooring recovery and re-installation
  • Drifting data buoy array deployment
  • Aerial hydrographic survey

Among the ocean features monitored by the mooring include the cold halocline, a layer within about 150 meters (500 feet) of the surface that's as cold as minus 2°C, and the layer found generally at 200 to 400 meters (700 to 1,300 feet) depth that is 3° to 5° warmer. The presence of the low-salinity, upper halocline is a key to ice formation, since it acts as an insulating lid, keeping the much-warmer underlying layer away from the ice. Scientists are interested in detecting changes that might mean the water in these layers is changing or mixing, something that could greatly affect ice formation.

Retrieving and re-deploying the mooring

The mooring team led by Dr. Knut Aagaard of the Polar Science Center at the University of Washington successfully recovered the 4,300 meters (2.7 miles) long deep ocean mooring near the North Pole, at 89° 33' N and 66° 40' E, and replaced it with another. In turn, the new mooring will be replaced with another next year for a total of three years of data. Recovering a deep ocean mooring from beneath the ice is a complex and difficult task . The only previous such mooring at the North Pole was in place for only one month in 1979.

Unlike the observatory's drifting buoys that routinely broadcast information to researchers via satellite, the top of the mooring is beneath the ice and each instrument must record internally and be retrieved to recover any of the data. The scientists were relieved to find the instruments on the first mooring recording and in good condition. Instruments on each mooring include seven conductivity-temperature recorders to measure the warming, cooling and salinity changes in different layers of the ocean; four current meters to measure speed and direction of flow; an acoustic doppler current profiler to provide detailed information on the vertical structure of the ocean currents, as well as the ice drift; and an upward-looking sonar to measure ice thickness. Among other measurements, the instruments monitor the condition of the upper 400 meters (1,300 feet) of the ocean.

2002 is third year for drifting buoys

Unlike the mooring, the drifting buoys transmit their data to a satellite, so one need not recover the buoy to get the data, which is constantly accessible. However, the buoys are vulnerable to damage from ice activity like pressure ridging and lead shearing or polar bears. As the Arctic ice continues its thinning trend, it has become more challenging to pick a good floe on which a buoy may survive the year and ultimately drift out Fram Strait into the greenland Sea. Instruments on the buoys measure and report information about weather conditions and the amount of heat reaching the ice from the sun and atmosphere, plus ice thickness and the state of the upper ocean. This year a substantial floe 2.5 meters thick was found for the buoy array, about a kilometer out from the camp at Borneo. Everything for the buoys had to be dragged out from camp on akias or banana sleds.

Physical oceanographer Dr. Takashi Kikuchi and marine technician
Hirokatsu Uno with the Japanese Marine Science and Technology Center deployed their fourth Compact Arctic Drifter (JCAD-4). It measures ocean temperature, salinity and currents, atmospheric temperature and pressure, and wind velocity. The use of a J-CAD each year of the North Pole Environmental Observatory amounts to a $2.5 million contribution (over five years) of equipment from Japan. Also being installed will be five buoys from NOAA's Pacific Marine Environmental Laboratory of Seattle and the U.S. Army's Cold Regions Research and Engineering Laboratory of Hanover, N.H. A meteorological buoy will measure wind speed, atmospheric pressure and temperature. Two radiometer buoys will measure short-wave radiation from the sun and long-wave radiation from the atmosphere. Two ice-mass balance buoys measure ice temperature profiles and snow thickness. As an entertaining sidelight, one PMEL buoy was equipped with a North Pole WebCam, allowing us to observe conditions at the buoy array.

This year the Observatory welcomes the Autonomous Ocean Flux Buoy, capable of measuring ocean heat and salinity as it moves from the warmer interior of the ocean up and through the ice. This "flux" is influenced by mixing in the upper layers of the ocean, which the buoy will also monitor. This buoy has been developed by Dr. Tim Stanton's Ocean Turbulence Laboratory at the Naval Postgraduate School in Monterey, California, under National Science Foundation Grant OPP 0084858.

Hydrography surveying includes fine-scale survey of Lomonosov Ridge

Using an extremely lightweight winch and a helicopter instead of an airplane made it possible for Dr. James Morison of the Polar Science Center at the University of Washington to land at 8 locations across 100 miles of ice for the most-detailed survey ever of the water properties over the Lomonosov Ridge. Only 1,000 meters below the surface in places, the Lomonosov is the Arctic Ocean's shallowest major ridge. Two branches of warmer waters from the Atlantic seem to travel along the ridge before exiting the Arctic along the east coast of Greenland. Whether they mix or remain separate are among the unknowns. It also appears that the ridge is one of the places where these warmer waters spread to deeper basins. At each location, the helicopter was able to land adjacent to very thin ice and lower an instrument profiling temperature, salinity and dissolved oxygen down to 500 meters.

As in previous years, hydrographic stations will be taken from a Twin Otter skiplane across a much wider area. These will included drawing water samples to measure concentrations of such chemical tracers as O2 isotopes, barium, and nutrients out in the Makarov Basin.