Edge of the Arctic Shelf

Moving Day
A sliver of moon hung in the clear morning sky as I strolled the decks this morning. David Leech was already busy setting up the University of Alaska central channel mooring instruments on the fantail. Just as the sun cleared the horizon, the mooring was assembled and ready to drop into place. David pulled the release and the mooring sank to the seafloor, collecting data for another year in the Chukchi Sea.

This afternoon the fantail was a blur of activity as WHOI mooring technicians John Kemp and Ryan Schrawder brought their mooring gear out of the cargo hold. They are getting ready to redeploy the line of eight WHOI moorings across the "edge of the arctic shelf" -- the steep dropoff into the Beaufort Sea north of Barrow.

This evening I caught up with Dan Schuller as he was analyzing the nutrient content of the water samples we have been collecting with the Niskin bottles. He uses a machine called a nutrient auto-analyzer to determine the amount of dissolved phosphate, silicate, and nitrate in seawater. You can think of these nutrients as the "fertilizer" for the tiny plants known as phytoplankton that comprise the base of the marine food chain. The levels of nutrients are also important in determining where the water came from. This figure shows the various currents that flow through the Chukchi Sea - they are color coded based on the amount of nutrients that they carry. Dan's data is important in helping us identify how the nutrient-rich Pacific Ocean waters travel across the shallow Chukchi Sea.

I have received a number of questions about the weather from Mrs. Cadwell's 5th grade students at Varnum Brook Elementary School in Pepperell, Massachusetts.

Question from Jesse: We are looking at Isabel at this time, how it is affecting us here in Pepperell. Is it affecting you at all?
Answer: Hi Jesse. No, hurricane Isabel is (thankfully!) not affecting us here in the Chukchi Sea. It is too far away to influence our weather. We do keep a close eye on weather, though. Wind and waves can have a serious imapact on our science. Since the CTD and moorings are very heavy, when the weather is rough they become difficult to handle. The Marine Science Technicians on the ship download weather charts every day, and the ship receives satellite images via the Terascan system. Every night Marine Science Technician Daniel Goana or Senior Chief Glen Hendrickson gives a weather brief to the Captain, Chief Scientist, and ship's officers so that we can know what to expect the next day.

Question from Mark: Our humidity is very high (93%) due to Isabel. Does your humidity ever reach those numbers?
Answer: Good question, Mark. Right now our humidity is 86%. This may seem high, but in reality there is not very much moisture in the air at all. My hands and lips are quite chapped from the dry air. So how is it that 86% is "not much moisture"? Well, it all depends on the temperature. Warm air can hold a lot more moisture than cold air. Since the Arctic is so cold compared to the temperate latitudes, it is also very very dry. In fact, it is considered a desert based on the amount of rainfall it receives every year. The annual precipitation (rain and snow) is less than 8 inches. The only place in North America that is drier than this is the desert southwest (Arizona/New Mexico)!

Pat from Mrs. Cadwell's class at Varnum Brook asks:
Question: What kind of camera do you have and how do you keep it from fogging up?
Answer: Hi Pat - be careful! I love talking about photography and cameras, so I hope this answer isn't too wordy for you! For these dispatch images I am using a 6 megapixel digital single-lens-reflex camera body (Nikon D100). The camera is digital, so I download the pictures to my laptop to review and post to the website. Single-lens-reflex means that when you look through the camera you are actually looking through the glass of the lens. The lenses are interchangeable, and I have a variety of lenses from wide angle lenses (for taking in the whole scene) to telephotos (for bringing those bears closer!) A fogged lens can indeed be a problem. Usually this happens if the camera gets very cold outside and then you bring it into a warm, humid room. The warm air then condenses on the cool surfaces of the camera, including the lens. This can be avoided by keeping the camera in a case when coming inside - that way the camera warms up gradually and condensation does not have a chance to form.

I also received a question from Mrs. Rollo's class at Varnum Brook.
Question from Ben: Why did the huge jellyfish have a huge hole in it and why was the woman holding not being stung by the tenticles.
Answer: Ben, jellyfish like cyanea sp. can in fact deliver a painful sting, but Christina was wearing some very thick rubber gloves, so she was not stung. The hole in the jellyfish was caused by its impact with the CTD instruments.

After we finish tonight's CTD work, it will be full speed ahead to the WHOI Beaufort Shelf Edge Mooring Array north of Barrow. We hope to begin the mooring work by Wednesday morning. Thanks for the wonderful questions - keep em flowing!