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18 November, 1999

Icebergs! I had the opportunity to see many icebergs up close since I have been in Antarctica. In the area around Cape Roberts and in several other locations, icebergs are frozen into the sea ice of the Ross Sea. These are icebergs that got trapped in the winter before they reached the water of the open sea. I walked around and up to several of these huge ice cubes. I even had the opportunity to climb up on one.

Icebergs are fragments of ice sheets and glaciers that extend into a sea or ocean. Icebergs will break off their ends and float in the surrounding ocean. Ninety-three percent of the world's mass of icebergs is found surrounding the Antarctic. Antarctic icebergs are characterized by their tremendous size and tabular shape. Lengths up to five miles are not unusual, with ice 150 feet above water. I saw several that were like medium sized islands. Most Antarctic icebergs are formed from the Antarctic continental ice sheet as it thins toward the coast and exudes into the ocean as a great ice shelf with fronts hundreds of miles long. The glacial ice of most icebergs has a specific gravity of .9 (Density = .9g/mL). This only means that about 90% of the mass of an iceberg is below the sea. (See diagram.) An icebergs' appearance depends upon how it is floating in the water. Many have flat tops, looking like floating plateaus. This happens when the iceberg is floating with the original surface of the glacier on top. These types of icebergs are very dangerous to approach because slabs of glacial ice may fall from the sides of the iceberg and throw ice and snow many hundreds of feet. The icebergs may also roll over. As the waves and currents wear away at the base of the glacier, the center of mass of the glacier will change and the glacier will change position. After the iceberg does this, the water-eroded surface is exposed. We walked up on one of these rolled over bergs near Cape Roberts.

The icebergs I saw were all frozen in the sea ice, but when the ice melts and these bergs reach open water, their movement will be influenced by wind and ocean currents. The speed and direction of this movement is also controlled by the size and shape of the iceberg, previous and present wind, surface wind current, and general ocean current. Dirt and debris covered the surface of many of the icebergs I saw. Icebergs transport pebbles, cobbles, boulders, and finer material, and even plant and animal life, thousands of miles from their source areas.

For more information about icebergs in the world, check out the Discovery web site at: http://www.discovery.com/exp/icebergs/ice101.html.

Today's featured CRP Team Members are three members of the palynology team. They are Rosemary Askin from Byrd Polar Research Center at Ohio State University and John Wrenn from the Center for Excellence in Palynology at Louisiana State University. Rosie and John work as palynologists in the project. Palynologists study organic walled microfossils. John specializes in dinoflagellates and acritarchs while Rosie focuses on fossil spores and pollen. The other member of the team is Vanessa Thorn, a paleobotanist from Victoria University in Wellington, New Zealand. Vanessa works to produce photographic images of the fossils the palynologists find under the microscope.

Note: I found an appropriate pan for the evaporation experiment. I will start again tomorrow

Here is what an iceberg might look like under the water. As much as 90% of it's mass may be underwater. This image came from the following NASA website: http://dcb.larc.nasa.gov/larcst/Iceberg.html.

Here are a number of large bergs imbedded in the sea off Cape Roberts.

This is the nose of the Barnes Glacier on Ross Island. It is from the front of glaciers like this that icebergs calve off.

Here I am in front of a relatively small iceberg frozen in the sea.

From left to right: John Wrenn, Rosemary Askin and Vanessa Thorne. These are only some of the members of the POD.

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