Dennis Leslie, age 13, of Omaha, Nebraska for his question:

What causes the oceans to rise?

If nobody told you, you would never guess that the world oceans seem to be rising. If expert oceanographers had not measured the sea level in fine detail, they never would have guessed it either. The process is so slight and so gradual that no one need worry about this minuscule encroachment of the sea. Future generations living ages from now may or may not have to evacuate some of their coastal cities. However, experts are not certain that the rising is a trend of long duration. The seas may swell for a time, then shrink.

Naturally this ocean trend provoked a lot of scientific curiosity. It was added to other data, suggesting a warming up of the Arctic climate. In the past decade, birds have arrived that never nested there before. A warmer Arctic climate should bite into the northern glaciers. Careful measuring showed that this is just what seems to be happening. The Muir glacier and many other famous ice fields are indeed receding. Season by season their edges are backing up from several inches to several feet. Their ice is melting and draining into the seas. This extra water is thought to be the reason why the world oceans are gradually rising.