Finding the Heartbeat of the Arctic Ocean

In last week's column , an oceanographer described the path of a yellow disc scientists set adrift at Prudhoe Bay in 1979. That same disc emerged at the feet of two brothers on a Scotland beach in early 1998. Ocean currents carried the disc more than 5,000 miles in its 19-year odyssey, which included a decade of floating on the Arctic Ocean.

The ocean on top of the world is getting plenty of attention from scientists these days, including two who believe they have found the Arctic Ocean's pulse: five- or six-year cycles during which the water level in the central Arctic Ocean is about one meter higher than it is during the following five or six years.

Two UAF oceanographers, Mark Johnson and Andrey Proshutinsky, thinks that understanding more about this ocean cycle could ultimately help scientists predict changes in the climate.

The Arctic Ocean is an ice-covered pool the size of Australia. With its center near the North Pole, the ocean touches the northern limits of Alaska, Russia, Norway, Denmark, Sweden, Greenland and Canada. Ice floes--huge hunks of sea ice that bump into one another for years before currents spit them to lower latitudes--cover the ocean like a layer of plastic film on a tub of water.

Johnson and Proshutinsky took all the variables we know about the Arctic Ocean, such as wind direction, wind speed, and depth of the ocean, and plugged all the numbers into a computer model. The model--an attempt to reproduce the Arctic Ocean on UAF's supercomputer--mixed all the variables and created a simulated ocean. Using the model, the scientists were able to see a pattern of five-to six-year bulges and recessions of the ocean by about one meter, about the distance from an average-size man's shoes to his belt.

Since the actual Arctic Ocean is immensely more complex than any computer version, the two researchers compared the model's results with real-life measurements. The flow of rivers in Russia, for example, followed a pattern that corresponded to sea-level changes in the model: when the model forecasted the Arctic Ocean would pulse upward, the discharge of the rivers into the Arctic Ocean was higher. Records of Alaska's permafrost also show a rhythm similar to that found by Johnson and Proshutinsky.

So what does it mean, this ocean with a pulse? Johnson and Proshutinsky are trying to find a correlation between the flexing of the Arctic Ocean and climate. The researchers found that when the ocean flexed up in the center, the pressure of the atmosphere directly above the ocean was higher. They also noticed that higher atmospheric pressure over the Arctic Ocean corresponds to lower pressure over Alaska. Low pressure systems mean increased snow and rainfall. When the cycle ebbs--when the Arctic Ocean is one meter lower--the researchers see the opposite: Low pressure over the ocean corresponds with high pressure over Alaska, which results in cold and clear weather in the winter and warm in the summer.

Of course, computer models are as imperfect as the organisms who use them. Knowing this, Johnson and Proshutinsky continue to check their model with real world results. They expect to soon collaborate with other scientists to install a noise-generating machine in the ocean off Franz Joseph Land in Russia so they can broadcast sound signals across the Arctic Ocean to a receiver in Barrow. The character of the sound waves will help them further understand the heartbeat of the Arctic Ocean.