Why Isn’t the Arctic Ocean Full of Freshwater Anymore?

It’s the only instance of a freshwater ocean on the planet.

Transcript

00:00 It's easy to tell where glaciers have been on land because they leave glacial valleys

00:06 and strange rock formations behind.

00:08 But on the ocean, that's different.

00:10 Well according to new research published in the journal Nature, the Arctic Ocean was once

00:14 a vast sheet of ice half a mile thick, and its water had a distinct peculiarity.

00:19 Researchers say that the ocean was quite shallow back then, and it was separated by land from

00:23 the other oceans.

00:24 That's because during the ice ages so much of the world's water was tied up in glaciers.

00:28 But when summer temperatures rose, parts of the ice caps and rivers would melt, meaning

00:32 the world's smallest ocean was also completely full of fresh water, for a minimum of two

00:37 glacial periods over the last 150,000 years.

00:40 Dr. Walter Giebert of the Alfred Wegener Institute and the study's lead author said about the

00:45 findings, "To our knowledge, this is the first time that a complete freshening of the

00:48 Arctic Ocean and the Nordic seas has been considered, happening not just once, but twice."

00:53 To discover this, researchers took sediment core samples from the Arctic Ocean, the Fram

00:57 Strait and the Nordic seas, finding that thorium-230 was missing from the samples in the same intervals,

01:03 thorium-230 being created when naturally occurring uranium decays in salty water.

01:07 Meaning at those times, the Arctic Ocean was a giant, albeit shallow, body of fresh water

01:11 under a massive sheet of ice.

01:13 (upbeat music)

01:16 (upbeat music)