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  berg 9 dec 2001  
Giant iceberg B-15 before the storm.
Click to enlarge.
   

Blowing in the Wind

Nature's Icebreaker
by Paul Doherty

December 20 , 2001

The old Antarctic hands play many jokes on newcomers. In 50-mile-per-hour (80 kph) storm winds, I faced downwind, then laid back, allowing the air to hold me up. This is called "leaning on the wind." One geologist saw me doing this and immediately walked behind me, "stealing my wind" and causing me to stagger around. He did this twice before I figured out what was going on.

Out on the ice, meanwhile, the winds were 100 mph (160 kph). When the speed of the wind doubles, the force the wind exerts on any object, like a human body, quadruples! At 120 mph (190 kph), the force of the wind is equal to the force of gravity, and humans can fly, whether they want to or not.

Here at McMurdo Station on Ross Island there is a giant iceberg named B-15 stealing our wind and ocean currents. It is 100 miles (160 km) long and 20 miles (30 km) wide, just about the size of the San Francisco peninsula. It stands 150 feet (50 m) above the ocean, and from what we know about icebergs, this means it extends 1500 feet (500 m) deep into the ocean. Some people wondered whether it was anchored to the bottom or not. In addition, because B-15 blocked the ocean currents last year, the sea ice never left the vicinity of McMurdo, and the icebreaker that clears the way for the all-important Greenwave supply ship had to cut a longer channel through the ice. This year there was so much ice that the Coast Guard sent two icebreakers.

  berg 17 dec 2001  
After the storm, the iceberg has rotated, and the sea ice has broken and blown away. Click to enlarge.
   

Then came the storm.

The old hands said it was the worst December storm in memory. The images from the weather satellite told an amazing tale. The 100+ mph winds pushed so hard on iceberg B-15 that it rotated around like the hour hand on a clock running backward. This answered the question about whether it was hitting the bottom or not: It was floating. The wind also broke up and blew out a 30-mile-diameter region of sea ice. The coast guard will have to do less work, thanks to the winds of December.

Now that I've been through my first storm, I'm beginning to feel like an old Antarctic hand myself. If I see anyone leaning on the wind, I know exactly what to do.

 

 

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