NASA scientists have used ice-penetrating radar to create a remarkable visualization of the many frozen layers that constitute Greenland's expansive ice sheet.

Prior to the new analysis, scientists who wanted to study the ice sheet had to drill down into it. By pulling up core samples, researchers were able to detect signs of past snow accumulation and temperature, while also observing impurities like dust and volcanic ash. But this sampling technique does not lend itself well to acquiring a "big picture" view of the sheet's interior.

The new technique, which relies on radar signals, transmitted into the ice from a plane and reflected back, is finally allowing scientists to measure the ice surface, sub-ice bedrock, and layers within the ice on a much larger scale

NASA/Goddard Visualization Studio

Using the technique, the scientists were able to map the three most prominent features of the 100,000 year-old ice sheet, each of which harbors clues about a distinct portion of climatic history. The top layer, which formed during the Holocene, is shown in green; the middle layer, which formed during the last ice age, is shown in blue; and the bottom layer, which formed during the Eemian period, is shown in red.

NASA/Goddard Visualization Studio

Interestingly, the Eemian occurred during a period of warmth — a phase similar to the one we're experiencing today. And indeed, the sheet is currently melting at an alarming rate. There's so much ice packed into the ice sheet that if it all melted, it is estimated the Earth's oceans would rise by about 20 feet (6 meters).

[NASA]