24 July, 2001

Seismic Science

Tuesday, 24 July 2001

Hej!

Life on Board

I have noticed that often in the evenings about 8 pm, the fog clears, the sun comes out, and it is beautiful until sometime in the middle of the night when the fog appears again. I started wondering to myself (and out loud), "Hmmm, how does the fog know when evening is?" One of the meteorologists in our Atmospheric Chemistry group, Michael Tjernstrom, from the University of Stockholm, gives us a weather report every day at our meeting including 24- and 48-hour forecasts (surprisingly, he is right most of the time!). The Arctic is not like San Diego where the weather person can get away with saying, "Late night and early morning fog, cool at the beach and warmer inland." After our meeting this morning, I asked him about the fog's disappearance. He suggested that there is enough of a tilt to the sun's circle-around-the-sky by this of the year to get the sun angle high enough by about 6 pm to start warming up the fog and causing it to disperse. He called this a "slight diurnal effect," even though it is not really noticeable to the naked eye that the sun angle changes throughout the day.

Where Are We Now?

It was snowing and beautiful this afternoon, with intermittent sunshine breaking through the clouds to light up the ice. We are heading south along the Lomonosov Ridge, traversing back and forth across the top. At 4:30 pm, our coordinates were 87o41' North and 134o33' East.

Scientists at Work

For the past several days, the Seismic team from the University of Bergen, Norway, has been working 24 hours a day on the aft (back) deck of the Oden. Using an underwater sonic air cannon, they are mapping out the structure of the Lomonosov Ridge. The air cannon is attached to a cable towed behind the ship about 10 meters (30 feet) below the ocean surface. Every 30 seconds, it shoots out a strong air pulse which creates a sound wave that travels down to the ocean floor and bounces back up towards the surface. Also towed behind the boat is a 450-meter long cable with microphones attached. The time it takes for the reflected sound wave to reach the microphones can be used to calculate the distance to the ocean floor for each pulse. By crossing back and forth over an area and using some computer technology, they can create a 3-D map of the area.

On the top of the Lomonosov Ridge sits 500 meters of sediments. These sediments, horizontal and in order, could tell the history of the climate in the Arctic Basin for the last 500,000 years by drilling a sediment core. This team of scientists wants to also map below the sediment layer into the bedrock of the Ridge and perhaps drill some cores here in future expeditions. They do not have the equipment available on this expedition to drill cores.

E-MAIL Away up here in the north the satellites are sketchy so I have about 6 minutes on-line before I lose connection. That doesn't leave much time for email after I send my daily report and no time for email if I send a picture, too. I managed to look at a few today:

John Lohr: I am glad you sent an answer concerning the whiteness of fog bows. I had just spoken to our resident fog expert on the Oden, Keith Biggs from Australia, who seems to spend most of his time collecting fog, filming fog, and counting ice crystals in fog. Your answer confirmed his reply that due to the small size of the fog droplets, the pathlength of the light is not sufficient to produce the colors that are associated with rainbows. Thanks for your expertise, and everything else. Annie Barnes, Julianna Snow, Ron Cooper, Dave Wright and everybody at El Capitan High School: Thanks for help on the phone yesterday and for your good wishes. Send me some heat! Rochelle and the gang in Boise, Idaho: Hello to all. Good ham radio to you.

Vi ses! (See you later!)

From Deck 4 on the Icebreaker Oden, somewhere north of 87 on the Lomonosov Ridge,

Dena Rosenberger

A fog bow off the bow of the Oden