Edge of the Arctic Shelf

Lights and Lobsters
I stayed up late last night - very late. How can you sleep when green ribbons of light are dancing across the clear night sky? The aurora borealis visited us last night and put on an incredible show. Starting at about midnight as a pale green glow, the aurora grew into a vast river of light arcing from horizon to horizon. The warm air (about 37°F) and light breeze made it the perfect aurora-watching night. I watched for hours as the ghostly tendrils snaked across the sky, finally fading into a pale mist.

A perfectly clear, calm dawn was a welcome sight to Jim Johnson and David Leech. Since their mooring work was complete, they were catching rides back to civilization on the ship's helicopter. Jim Johnson will be returning to his home in Seattle, but I don't think he'll even be unpacking - he is headed to another mooring cruise in a few short days! ... and David has some very rambunctious dogs that are waiting for a long walk in Seward, Alaska. We will miss their helping hands and their great company. As the HH-65A's rotor blades began to spin on the flight deck, we passed on our wishes for a happy journey, and moments later they were lifting off, headed for the small Alaskan town of Wainwright.

This afternoon we tested out Carin Ashjian's ring net system. This is one oceanographic tool that is easy to explain! All we do is dip this net into the water and bring it back up. Then we look at what we caught! The gooey substance that looks like applesauce is composed mainly of microscopic marine plants called phytoplankton. Carin was surprised at how much phytoplankton came up in this net tow - usually the concentration is much lower at this time of year. As we sifted through the 'sauce,' we looked for tiny marine crustaceans called copepods. They look like tiny lobsters, and they feed on phytoplankton and other copepods in the ocean. They are an important part of the food web in the Arctic Ocean, and are a key food source for the mighty bowhead whales that migrate through the Arctic.

I have received some questions from Mrs. Cadwell's 5th grade students at Varnum Brook Elementary School in Pepperell, Massachusetts.

Question from Kevin: How fast can the Healy go?
Answer: Hi Kevin, the Healy can go 18 knots at top speed. What's a knot, you might be asking? A knot is a nautical mile per hour. We use nautical miles and knots at sea because one nautical mile is equivalent to one minute of latitude - that makes it easy to measure distances on charts. So what's a nautical mile? A nautical mile is 2,025 yards, as opposed to a statute (regular, everyday) mile, which is 1,760 yards. So, knowing that, can you figure out how fast the Healy can go in miles per hour? I'll put the answer in tomorrow's dispatch.

Question from Marlayna: How far have you traveled since the day you left? Could you show us your path so we can look at it?
Answer: Marlayna, to view our most recent position click here. Due to security requirements the map is two days old, but it gives you an idea of where we have been. We have already traveled over 1,600 miles (statue miles). That's roughly halfway across the United States! We are about one third of the way done with the cruise, so we have a lot more traveling left to do...

Today's transit was a welcome break from the intense CTD surveying we have been doing in the Chukchi Sea. Tonight we will arrive at the deepest station of the WHOI mooring array and Carin Ashjian will do some net tows at the mooring locations. She is doing this for a very important reason. The WHOI moorings have been (hopefully) collecting data since last year. One of those instruments is an Acoustic Doppler Current Profiler (ADCP). It measures currents by bouncing sound waves off of small particles in the water column. Some of those particles are tiny copepods! So, in addition to measuring the currents, the ADCP can also give you an estimate of how many copepods there are. Carin's net tows will provide an important "ground truth" to the ADCP data. She will compare the number of copepods in the net to the number that the ADCP measures, and using that data she will be able to make assumptions about the numbers the ADCP has measured throughout the year. After the night net tows, John Kemp and Ryan Schrawder will start pulling up the WHOI mooring array, starting right after breakfast.