July 15, 2006 Options

[Betty_Carvellas]

July 15, 2006

With stations running well into the night and early morning and with daylight most of that time, the last couple of days have become a bit blurry. We started the line of 12 CTD stations across Bering Strait last night around 7 PM and we finished our work at 3 AM. Since we only took water from 5 of the stations, and some of the stations didn't include water at all, I'm not sure what time the last one ended. I do know that just before I went to bed, there were 8 members of the science team working, and 2 others who had only recently turned in. Even with all that, there's another long line of CTD stations tonight. Ship time is expensive, and everyone wants to make the most of their time out here; science happens round the clock.

Shortly after I woke up, there was an announcement that the small boat would be departing for Little Diomede with anyone who wanted to go ashore. We were anchored in the middle of Bering Strait between Little Diomede and Big Diomede Islands, just east of the US/Russian border. The Russian island of Big Diomede is around from the U.S. island of Little Diomede. The entire settlement of approximately 150 people exists right on the edge of the rocky island which is accessible only by boat, small plane, or helicopter depending on the time of year. I came over on the first boat with Lee Cooper who has done extensive work on the island and who knows many people in the community. Huge flocks of birds flew overhead, the island was shrouded in fog, and it was very cold when we landed. Soon after we got on the island, I began talking with a woman who has lived on Diomede all her life, and who works in the city office. She showed me pictures of her children and of the procedures they use to make raincoats from walrus intestines and drums from the stomach of the walrus. The economy of the island is subsistence based, and the people hunt beluga and bowhead whales, seals, walrus, and polar bear, and supplement their diet with fish, crabs, local wild greens and vegetables. Frances told me how they use every part of the walrus, including the skin for their boats. She proudly told me that the men make the boat frames, but it's the women who know how to prepare and sew the skins for the covering. Diomede is remote and isolated, but the sense of community here is strong. Frances told me that she occasionally goes to Anchorage and she likes the malls, but she is always happy to come home to Diomede.


This satellite image clearly shows the russian island of Big Diomede and the U.S. Little Diomede Island in the Bering Strait.


If you look closely, you can see the settlement of Diomede on Little Diomede Island in the Bering Strait.

Once we returned to the ship, Dr. Rebecca Woodgate began preparations to retrieve her third mooring and deploy one more. You might remember from my journal of July 5, that I helped Rebecca check the release mechanisms for the three moorings. Rebecca is a senior oceanographer at the Polar Science Center of the University of Washington in Seattle. While on this cruise last year, I watched Rebecca set out the three moorings she is retrieving this year. Each mooring was out for almost exactly one year, and this particular series of moorings has been on-going since 1990, set out in the same place each year. If you're interested, you can check out the website at . I hope to do a pod cast with Rebecca before we leave the ship; it will be available on the TREC website.


Rebecca Woodgate has now succesfully retrieved three moorings and deployed three others while on this cruise. She seen here with an Aanderaa current meter.

Each of the moorings carries instruments to measure water flow/velocity, temperature and salinity, and ice thickness and motion. One mooring also has an instrument to measure fluorescence (used to assess phytoplankton). To measure the water flow/velocity, the ADCP (Acoustic Doppler Current Profile) sends an acoustic signal that reflects off organisms and inanimate objects drifting in the water column. Because it comes back with a slightly different frequency, due to the Doppler shift, you can tell how fast the water is moving. It picks up a signal every two meters, thus showing differences in the currents. For example, while there is a one knot current in the middle of the eastern channel of the Bering Strait, the Alaska Coastal Current, on the east coast of the strait, flows at two - three knots. Data suggest that 1/8th of the fresh water entering the Arctic Ocean comes through this current; the Bering Strait through flow, as a whole, brings in one third of the fresh water entering the Arctic Ocean. The Arctic Ocean flows into the Atlantic Ocean, and scientists are concerned about the amount of fresh water entering the Atlantic. It's possible that an increase in fresh water could disturb global ocean circulation. It's this circulation pattern that brings the warm Gulf Stream water along the northeastern shores of North America and on to parts of Europe. A change in the circulation might mean harsher winters in some parts of Europe. Global warming doesn't mean that temperatures increase everywhere!


You can see the entire mooring in this picture, from the floats at the top to the train wheel at the bottom.

I was interested to find out how a mooring instrument could measure ice thickness and motion. An acoustic sonar device on the top of the mooring sends a signal up to the ice above it. From the return signal, you can tell how deep the mooring is under the ice. If you know the actual depth of the mooring instrument, it's possible to calculate how much ice is above it.

There are really two channels running through the Bering Strait, one in U.S. waters, and one in Russian waters. Rebecca retrieved and deployed two moorings in the U.S. side of the Strait and one just north of the two channels. The northern mooring gives integrated data about flow in both channels. Now that the moorings have been retrieved, Rebecca will download all but the ice thickness data. With instruments that collect data every 30 - 60 minutes, a year's worth of data is extremely valuable.

Rebecca is pleased that she was able to retrieve all three moorings. Each mooring is anchored by train wheels to the bottom. The dual releases are just above the anchor, followed by large glass spheres for flotation, and then the series of instruments. A large, round, steel float sits at the top of the mooring. To retrieve the mooring, Rebecca lowers a hydrophone into the water to send a coded acoustic signal to 'wake up" the releases which then send a signal back. The hydrophone can pick up a signal from up to ten miles. When the ship is close enough to see the mooring, Rebecca triggers the release, which releases the floats and instruments from the train wheel and when the mooring comes to the surface, the crew attaches a line and brings the mooring on board.

I asked Rebecca what changes she's seen since 1990 when this series began. From 1990-1997, there was a warming trend, from 1997-2000, scientists saw a period of cooling, and from 2000 on, we are once again into a warming period. In a few days, she'll have data from this past year.