16 February, 2003

SPONGE BOB Meets ALISON

Perhaps you think that our little invertebrate friend is out of his element here in Fairbanks? Not So! After all, is he not filled with air pockets? Is he not the ideal individual to help us to study and understand heat transfer and insulation?

We are here in the heart of Alaska to work with Dr. Martin Jeffries at the University of Alaska, Fairbanks. Dr. Jeffries has established a network of lake-monitoring schools across the state. The Alaska Lake Ice and Snow

Observatory Network (ALISON) project involves K-12 students and teachers in measuring conductive heat flow and ice thickness data throughout the winter.

Visit the ALISON Web site at http://www.gi.alaska.edu/alison

Critical factors that impact lake ice growth include (but are not limited to) the air temperature, the snow/ice interface temperatures, the surface area of the lake, the snow or snow-ice blanket resting on the lake's surface, as well as the corresponding density of that blanket.

Remember that energy flows by the following mechanisms: radiation, convection, and conduction. The rate at which heat flows out of Arctic lakes and ponds in the winter depends, in part, on the thermal conductivity of the snow. Thermal conductivity is related to snow density. The more dense (or tightly packed) the snow cover is,the greater its conductive heat flow will be.

Because conduction occurs when heat flows from a hot object when it comes in direct contact with a colder one, good insulators are those that keep the hot and cold objects from touching. We often use air (a poor conductor of heat) to separate hot and cold substances.

For example, Styrofoam (used to contain hot and cold drinks) is filled with air. Down vests and coats are puffy because they hold so much air. Fiberglass insulation uses two poor thermal conductors (glass and air) to keep heat from flowing across the walls of buildings. Other poor thermal conductors include wood fibers, rubber, and polymers.

Naturally, the ideal substance for preventing the conduction of heat is NO substance at all! A vacuum provides a space devoid of molecular bombardment and, therefore, an environment that prohibits heat conduction between two objects or substances.

Sponge Bob gives new meaning to “CONDUCTING” research as he studies the insulating properties of snow.

Although the crystals of snow against Sponge Bob’s skin conduct heat away from his body, the fluffy snow with air pockets serves as a good insulator and prevents direct contact with the colder air above him.

A cold metal pipe at –20 degrees Celsius is NOT a good place for a wet sponge to stand! Heat will flow out of Sponge Bob (from a higher temperature to a lower temperature) until “thermal equilibrium” is reached. Yikes!

These boots worn by polar researchers use several centimeters of a poor thermal conductor in order to keep the heat of the researcher’s foot from flowing out to the underlying ice or snow.

Sponge Bob enjoys the bright sunshine, but receives little warmth from it. When “insolation” is low, your “insulation” should be high! Confused? Look for an explanation in tomorrow’s journal!