An Ice-Free Arctic … Happening Before Our Eyes

New techniques are closing in on how to measure the amount of ice "freeboard" floating above the surface, which with a little fancy math can tell scientists the volume of the ice.

The world's first nuclear submarine, the USS Nautilus, made the first submarine sonar measurements of Arctic sea-ice thickness in 1958.

"In the early '60s, they found thicknesses in the North Pole region of about 3½ meters [about 11 feet], and then in the late '80s and early '90s it was down to about 2½ meters [7 feet or 8 feet,]" Serreze said to ABC News.

"They needed that info back then for two reasons. First, to know where they could surface in an emergency. Second, to know where they could surface if there was a 'boomer' and they needed to fire off some missiles."

A third reason now adds great value to those ice-thickness measurements from Cold War submarines -- the accelerating advance of global warming.

Both U.S. and former Soviet Union ice-thickness measurements have been declassified and are available to the world's ice experts.

Serreze says that a number of his colleagues are now working on Arctic summer sea-ice thickness, and that their findings so far show massive volume loss over the last 30 years.

Serreze cites work by Wieslaw Maslowski of the U.S. Navy Post Graduate School in Monterey, Calif., that strongly suggests it's not only Earth's warming atmosphere that is melting the Arctic ice from above.

"Wieslaw is saying it's also the warming sea currents melting the sea ice from below. He's been arguing that 2070 is way too far out in the future -- way too conservative. I suspect he may be right," Serreze said.

Both these reporters walking out on the Arctic sea ice last summer in the company of scientists and Coast Guard officers of the Ice Breaker USCG Healy, were, as Arctic first timers, naturally worried about walking on thin ice a mile and a half above the sea floor.

"How thick? Is it safe?" we asked several times, stepping from small landing craft onto the beautiful white and blue undulating planes of ice reaching to the horizon.

We always got answers something like: "It's still OK -- it's about four feet thick. It used to be eight feet thick, but now it's about four in most places."

Coasties and scientists are watching that thickness ever more closely now as they step off their landing boats, racing to gather what knowledge they can of this largely unknown and breathtakingly beautiful environment that is now melting away fast.

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