8 February, 1998

Hi from Antarctica! This morning, I woke up an hour before the alarm went off . . . at 4:00 a.m.! The engines of the ship were very loud, and we were rolling around quite a bit. The ship would go forward and the front end would seem to go up . . . and then our forward progress would stop. The engines would then quiet down a little, and we would either slide right, left, or forward and then down. This was happening over and over. I knew right away that we were in heavy ice. The ship will push up onto a piece of ice with a lot of noise from the engines. Then, the weight of the ship will break the ice and we will slide down into the water . . . and then the engines will push us up onto another piece of ice. I got off my bunk bed and looked out the window -- it looked like we were in the middle of a snow covered landscape. The pack ice was so close that you couldn't see very much water at all! I turned on my television to look out the front of the ship (we have cameras all over the ship that we can see on different channels) and it looked like that in all directions. Needless to say, we ended up turning around and going back. So . . . our trip to the Eastern Ross Sea was cut short! We are now back in the Central Ross Sea and proceeding towards "Plan B." It looks like we may be heading back towards the Western Ross Sea in a few days. This will put us south of Cape Adare, but back towards the beautiful coastline of the Transantarctic Mountains. Dr. Anderson and Stephanie are not pleased about this setback, but they are making the best of it.

Due to our change of plans, we came back by the Ross Ice Shelf again today. Yesterday's questions asked "What exactly is an ice shelf? How do you suppose an ice shelf is formed?" Well, an ice shelf is a large, floating area of ice that is connected to the land. It is formed from the ice sheet that covers most of Antarctica. As this ice sheet approaches the sea, it sometimes extends from the land into the water. Because it is floating and not touching the seafloor, it is called an ice shelf.

There are no major ice shelves in the Arctic, but in Antarctica they are massive. The largest are in the Ross and Weddell Seas. The Ross Ice Shelf, which we observed, covers an area larger than the state of Texas! It's average thickness is 335 to 700 meters, but where the front end faces the Ross Sea it is closer to 100 meters thick. As the continental ice sheet moves from the center of the continent towards the sea (How do you suppose the ice sheet forms?), icebergs calve off the front of the ice shelf to allow for the new ice near the shore. This process does not keep the ice shelf at an exact size, however. According to our most recent observations, the Ross Ice Shelf seems to be advancing towards the sea. We were able to personally verify this today when we tried to Multibeam near a core site from 10 years ago. We plotted the way point on the map, and gave the latitude and longitude coordinates to the Mate on the Bridge. After a while, we received a phone call. It seems that the point that we gave him was over a mile inside the ice shelf! There was no way we could go back to that location . . . even though it was open water only a few years ago! At other times in history, the Ross Ice Shelf has been much smaller than it is today. When Borchgrevink (remember him, from our huts?) came upon the Ross Ice Shelf in 1900, it was noticeably smaller than it was when James Clark Ross first discovered it in 1841.

Not all ice shelves seem to be advancing, however. In fact, ice shelves in the Antarctic Peninsula seem to be disintegrating. One possible theory is that this is due to global warming. The Antarctic Peninsula is the northernmost part of the continent, and therefore it is the warmest. Since the 1940s, the average temperature in the Antarctic Peninsula has increased by 2.5 degrees C. This has weakened the ice shelves in that area. In addition, warmer sea water may be causing the ice shelves to melt from underneath. As a result, more than 3000 square miles of ice shelves in the Antarctic Peninsula area have disappeared without being renewed in the last 50 years.

It is important to understand that the gradual disintegration of the ice shelves in the Antarctic Peninsula won't necessarily raise sea levels. If you put an ice cube in a glass of water, the water level goes up as soon as the ice is added. As that ice cube melts, the water level does not change. Since the ice shelves are already floating, sea level will not change if they melt. The only way sea level would rise due to the gradual disintegration of the Antarctic Peninsula ice shelves would be if their crumbling caused the ice sheet overlying the land to discharge more ice. Even in that situation, however, the rest of the world would feel very little effect. The extra discharge would have to occur from many parts of the Antarctic Ice Sheet, not just near the Peninsula, for large changes in sea level to occur.

Well, that's about all for today. We will continue our Multibeam survey of the Central Ross Sea tomorrow and we are planning to begin a deep tow survey sometime very early on the 10th of February. Since our plans have made some pretty dramatic changes today, I'll have to keep you posted about the exact details. I do know that we are scheduled to pull into McMurdo Station on February 20th (that's the 19th back in the U.S.). I can still answer any questions sent before the 18th of February in the United States . . . so that gives us about 10 more days. I look forward to hearing from you!

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