|Next stop, Wilkins ice shelf. We hope to find whales and penguins.
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Photograph by Mark Christmas
May 21, 2001
Latitude: 70° 31 827 S
Longitude: 76° 37 264 W
Temperature: -2.0° C (28° F)
Wind Chill: -10.9° C (12° F)
0300 hours: The line-transect survey of the cruise is complete. We finished yesterday. Afterwards, Peter Wiebe led a meeting of the science groups to reach a consensus on the research goals to be accomplished in the next 12 days. One of the first, the bird and whale groups need time to study their subjects, up close and personal. So its off to the Wilkens Ice shelf, just below Charcot Island. Hopefully well find birds and whales there.
1000 hours: The trip to the ice shelf was uneventful. We encountered ice that was packed tightly. The temperatures have dropped to -4.2° C (25° F). The plan was to have the whale group head out in a Zodiac to search for whales to biopsy, and the bird group, also in a Zodiac, to look for birds to study stomach contents. The ice was packed too tightly for Zodiac operations. We changed course and headed to the edge of the ice. Flexibility is a necessity when the weather is a determining factor.
1230 hours: We finally got the Zodiacs in the water. I joined Ari Friedlaender, Catherine Berchok, Aparna Sreenivasan, and Cabell Davis looking for whales. The sun rose today at 1130 hours and set at 1400 hours. Thats not a lot of time to spend on the water. We didnt see any whales, but we saw some crabeater seals and were followed for about five minutes by a lone leopard seal. Ive been told that the leopard seal will actually bite a Zodiac. We were stopped for a moment and the leopard seal swam around and under us, carefully sizing us up. We returned to the ship, but not until after Ari took a couple of practice shots with his crossbow and we recovered the arrows.
There are televisions in every cabin and in most of the work areas. Surfing the channels here is very different than at home. There are video cameras aimed at various parts of the ship. The most interesting channels are those which have the heads-up display from the variety of sensors on the ship. At a glance you can learn; water temperature, air temperature, course, speed, wind direction and speed (both relative and true), barometric pressure, bottom depth, latitude, and longitude. This is the information I look at before I leave my cabin. Theres also information on currents, salinity, and a large number of environmental sensors that I admit to be ignorant about.
Here are some more questions sent in to us via e-mail:
Q: How old is the ice cap in Antarctica? Is the ice clear where it seems to have a blue tint to it? Does the ice melt at a considerable rate per year? Vern in Iowa
A: John Klinck and the geologists of Old Dominion University tackled this question!
Evidence suggests that South America separated from the Antarctic continent about 30 million years ago, at which time there is evidence of an ice cap forming. Although the volume of the ice cap changes over time, there seems to have been ice over Antarctica since that time. However, you should think of the ice in terms of honey slowly sliding off the Antarctic continent. Snow accumulates over the land and eventually slides off the ice shelves, making icebergs.
Ice melts where it is in contact with the ocean, mainly. Deep in the ice, there is some melting due to high pressure. When matter is compressed, its temperature goes up. That is why your bicycle pump seems warmer after you use it. There is a complicated pattern of melting and freezing where the ice slides into the ocean, so the net melt rate is not very large. Ice tends to break off the shelves and move northward where it melts in the warmer water (after a few years).
New ice looks white or clear. The white patterns come from air that was dissolved in the water and becomes trapped in the ice when it freezes. Slow freezing makes clear ice, rapid freezing makes white ice (like snow). After enough time, the air works its way out of the ice, leaving a relatively pure crystalline form of water ice. This tends to scatter blue light stronger than other colors, so the ice looks blue.
Thanks for your curiosity,
Department of Ocean, Earth, and Atmospheric Sciences, Old Dominion University, Norfolk, Virginia.
Ive received several questions about the camera equipment Im using.
Im shooting with a Nikon COOLPIX 990 digital camera. Most times Im using the WC-E63 wide converter lens. I also have the TC-E3ED 3x Tele Converter (a telephoto) lens. For the iPIX images, I use the FC-E8 0.21x fisheye lens. I use a SB-23 Speedlight flash with the SK E-900 flash bracket. Its extremely difficult to use the telephoto due to the low light and constant motion.
Mark Christmas, nationalgeographic.com field producer
Have a question for Mark or the SeaLab team about the expedition or life at sea in Antarctica? In every dispatch, Mark will answer selected questions from readers.
[Note: nationalgeographic.com does not research or copyedit dispatches.]
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