Edge of the Arctic Shelf

Countdown
The big countdown has started... The last CTD section has been posted on the white board, and the end is in sight. In only a few days we'll be back on land, heading home. The crew of the Healy is even more excited - this science expedition is the last one of the summer season. Their long deployment, which started in June, will be over shortly after they drop us off in Nome.

Our eddy hunt today was a success. We found what we were looking for - evidence in both the temperature and turbidity (water "dirtiness") data that an eddy was present on the shelf edge. The eddy was located at 300 feet in depth. Since the eddy was carrying shelf waters off into the deep basin, it had picked up (entrained) dirt and phytoplankton and carried them over the shelf edge. Dean Stockwell noticed it right away when he compared two water samples. The deeper sample contained a lot more mud and biological matter than a sample taken only 100 feet above.

These questions about arctic plankton come from Mrs. Lyons' 5th grade class at Mt. Alvernia Academy in Chestnut Hill, Massachusetts. Dean Stockwell is a researcher at the University of Alaska, Fairbanks. He has been studying polar phytoplankton for over 25 years, with countless trips to both Arctic and Antarctic waters.

Question from Gina and James: Can plants photosynthesize underwater, and how do they survive during the winter when there is no sun and it is very cold?
Answer from Dean: "Yes, photosynthesis can take place underwater. The seaweeds we are all familiar with along our coastlines are photosynthetic plants.

Polar regions present marine plants with a difficult problem, how to survive the long periods of winter darkness. Many of the microscopic algae that occupy polar oceans have the ability to produce resting stages. During this time all plant processes are reduced to a minimum. Perhaps you can compare it to a bear's hibernation. Other plants actually produce specialized resting spores which protect the cell until light conditions improve."

Question from Ryan and Patricia:What is your hypothesis so far concerning the temperature of the water? Do you think it is changing and will this kill the algae?
Answer: These are both good questions. Water temperatures change over many different time scales. They range from very short time scales, such as those we have recently observed with the eddies, to very long time scales, such as the freezing and thawing of ice ages. The data the moorings have collected will be very important in determining how the water changes over the course of a year. Since the moorings are going to be deployed for two years, we can then compare how the temperature behaves from one year to the next. Those are called interannual changes. To fully understand how the temperature changes you would need the longest possible data record - several hundred years would be a good start! That's why there's still so many unsolved problems in oceanography. If one of you becomes an arctic oceanographer some day, you could be comparing our temperature measurements to those that you have collected!

Dean had this to say about the algae: "If in fact temperatures begin to rise in polar oceans, many of the algae forms present may die out. Extinctions are common in the geologic record. This warmimg, however, may also allow species now living in warmer waters to extend their habitat ranges into these newly warmed waters. As cold water species leave town, warm water species move in."

For Brian and his classmates at Wayzata West Middle School who have been wondering about the worm that we brought up on one of the moorings, I have an update. Carin Ashjian brought the preserved worm back to Woods Hole Oceanographic Institution and showed it to some colleagues in the biology department. They thought it was interesting enough to put the tiny creature through a very specialized CAT scanner! Hopefully we'll know more in the next few days - I'll keep you posted.