Edge of the Arctic Shelf

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Dispatch 05 - July 19, 2002
By C.A. Linder

Weather conditions: clear skies, calm winds and seas, air temperature 52° F

Over the Side
You couldn’t ask for a finer day to be studying the waters of the Chukchi Sea. The sun is shining brightly, gentle swell waves barely disturb the water’s surface, and a cool breeze blows across the deck. John Kemp speculates that a navigational error has taken us south to Hawaii instead of north to the Arctic, but the sun, already high in the sky at 8am, proves him wrong (or the fact that he can see his breath?).


Sarah Thornton’s nitrate analyzer is joined to the mooring line. David Leech supervises the operation.
Click for more photos of the mooring deployment

David Leech from the University of Alaska, Fairbanks, supervised the deployment of the first mooring of the cruise. This mooring will collect a variety of oceanographic data. It will measure the speed and direction of the currents and a variety of different water properties, such as the temperature, the amount of light penetrating the water column, and the amount of dissolved nutrients. This mooring is the only one that will have an instrument called the NAS-2E nutrient analyzer. Sarah Thornton is the technician who deploys this machine and interprets the data. The instrument is very similar to the shipboard analyzer that the CTD group uses except that it runs unattended, collecting data 4 times a day for an entire year! This technology has only been recently developed (1998), and Sarah has been working with this instrument for the past 2 years. She currently has five of these analyzers collecting data in the Bering and Chukchi Seas for various projects. You are probably wondering about the cooler that is bolted to the top of the instrument (see photo of the nutrient analyzer attached to mooring line). It’s not to keep Sarah’s beer cold... Since the instrument was designed to be operated for a maximum of only two months, Sarah manufactured a new housing to hold the extra chemicals to last a one-year deployment. She found that an ordinary styrofoam cooler does the job quite well! So why is nitrate important? You can think of nitrate as “fertilizer” for the “garden” of tiny plants (phytoplankton) that are found all over the world’s oceans. They are the base of the food chain, and thus understanding the phytoplankton is critical to understanding the web of life in the Chukchi Sea. This is the first time that scientists will be able to see how nitrate changes over an entire year in the Arctic.


	T.J. Riley hits the water.
	Click here for more photos of the Polar Star’s divers taking the plunge

A short steam then took us to the start of our first CTD section. A section is a series of CTD stations arranged in a pattern (often a straight line). Scientists sample in this manner to see a two-dimensional cross-section of water properties. In this case our section will run from west to east across the Chukchi Sea central channel. We are hoping to observe one of the locations where Pacific water is flowing northward into the Arctic.

This evening the ship’s divers braved the frigid Arctic waters to perform a routine check on the propeller blades. Our last CTD showed a surface water temperature of 38° F! This may seem cold, but the Polar Star’s divers are used to diving under the ice, where the water can be as cold as 28° F.

We look forward to your questions. Please email us at arcticedge@whoi.edu.

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