Rising Sea Level and the Next Ice Age
During the last four billion years, Earth has many times flip-flopped from a cold, icy sphere to a greener, warmer place. We’re currently in the latter state, a time scientists call “interglacial” because they expect another ice age to follow. Or will it? Sea level is the highest it has been in 250,000 years, and a warming climate may be stalling Earth’s natural cycle of hot and cold periods.
Robert Bindschadler’s goal is to find the culprit in the rising of the world’s oceans, which have crept up more than 375 feet since the last ice age. Bindschadler, a glaciologist with the NASA Goddard Space Flight Center who visited Fairbanks last week, said oceans have swelled since the last ice age because glaciers and immense sheets of ice have melted. While drastic sea level rises between ice ages are normal, Bindschadler said the planet might never have seen a warm spell like the present one. He wants to learn more about the current sea level rise by looking at Earth’s ice from above.
Satellites orbiting 500 miles above Earth provide a good look at the larger portions of the world’s ice supply, 90 percent of which is in Antarctica. Antarctica consists of several massive fields of ice, but the smallest one is the most compelling to Bindschadler and others studying sea level rise. The west Antarctic ice sheet, which is about the size of Mexico, might be the main contributor to sea level rise now and in the future. Since the last ice age ended about 20,000 years ago, the west Antarctic ice sheet has lost two-thirds of its mass, probably adding about 30 feet to sea level worldwide. Bindschadler said the west Antarctic ice sits on a bed of slippery ocean sediment rather than bedrock, which means it may collapse into the sea. If the whole ice sheet calves into the sea, it will raise sea level in the world’s oceans another 15 feet.
In 2001, NASA will launch a satellite that will use a laser beam to measure the size of glaciers and ice sheets. The satellite will shoot the beam down to the ice surface, then record the time it takes for the beam to be reflected. Scientists will check the elevation of ice fields and later compare the information with new readings to see how much melting, calving, or ice growth occurred between satellite passes.
The new satellite may allow scientists to find out how fast sea level might rise in the future, a statistic that affects most of the people on Earth. Bindschadler said two-to-three billion people live in coastal areas of the world, and a three-foot rise in sea level will slowly destroy as much as $475 billion worth of homes and property in the U.S. alone. He said the rising of the world’s oceans also makes him wonder if people, through the emission of greenhouse gases, have disrupted the planet’s natural succession from ice age to warming period to ice age.
“Sea level is the highest it’s ever been and climate is about as warm as it’s ever been,” Bindschadler said. “We’re really moving into uncharted territory.”
