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Antarctica's hula hoop of water

Click here for a high resolution photograph.

Hula hoops are big, light-weight, circular toys made to swing around your waist -- if you move your hips just right. There is a "hula hoop" made of water circling Antarctica right now. While Antarctica has no hips, it does have an arm -- and this arm is part of the story of how the invisible hula hoop which is really a huge circular stream of ocean water -- began circling Antarctica.

If you look at the map that goes along with this article, you can see that the arm or "peninsula" of Antarctica appears to be reaching out to South America. Millions of years ago, this arm and South America were connected.

Scientists think that the breakup of the connection between Antarctica and South America was important for kick-starting the ocean current that is now circling Antarctica like a hula hoop.

"So, Antarctica's arm disconnected from South America and started splashing its giant hand around in the water until it got this huge circular ocean current going. Right????"

No, not exactly. The disconnection between Antarctica's arm and South America was involved in forming the circular current of water around Antarctica, but not like that.

Click here for a high resolution photograph.

The circular ocean current we are talking about is called the Antarctic Circumpolar Current. It's an important current because it helps keep Antarctica cold by deflecting warm streams of water that come up from the equator.

Before this current could form, water needed to be able to move all the way around Antarctica. For this to happen, a gap had to form between Antarctica's arm and South America. Complex processes inside the earth called "plate tectonics" were responsible for the creation of this gap.

Scientists are not sure when this gap formed. Knowing when the gap formed would be very useful for determining the role that the Antarctic Circumpolar Current played in the growth of glaciers on Antarctica about 34 million years ago as well as other aspects of climate change.

And this is where the new research comes in. The scientists have just shown that, by 41 million years ago, Antarctica's arm and South America had separated enough for water to pass from the Pacific Ocean -- through a gap between Antarctica's arm and South America called Drake Passage and into the Atlantic Ocean.

To figure out when this gap formed, the scientists studied fossil teeth from fish that were recovered from rocks more than 1,000 feet below the bottom of the Atlantic Ocean. By testing the teeth for levels of the element neodymium, the researchers can tell when water from the Pacific Ocean started making its way to the Atlantic Ocean.

With this new information on when water started moving from the Pacific to the Atlantic, scientists can start to determine when Antarctica's hula hoop of water formed. And knowing when it formed is critical for understanding what role it played in the making of the huge sheets of ice found on Antarctica today.

So, even though the trick to getting the human hula hoop to move around your waist is in the hips, when it came to getting Antarctica's hula hoop of water moving around this continent, think arm not hips.


This research from Howie Scher from University of Rochester in Rochester, NY and Ellen Martin from the University of Florida in Gainesville, FL appears in the 21 April 2006 issue of the journal Science.