Cruise Day 35
Speed 0 knots (kts) Course n/a Location Makarov Basin, ~198 nautical miles south of N. Pole Depth 3475 m
GO DEEPER DISCUSSION: (see previous journal for the questions.)
To explain the behavior of my compass, let’s remember the basics about a simple magnetic field. Perhaps you’ve done the experiment with a bar magnet and iron filings to visualize magnetic field lines – each imaginary line connects the north to the south magnetic pole in a curve that arcs out of each pole, running to the other in a curving half-loop. If you are somewhere along the side of the magnet, magnetic field lines will run nearly parallel to the edge, but near the poles the lines are sloping steeply in. The Earth’s magnetic field is similar, with magnetic field lines emerging nearly perpendicular to the surface at the north and south magnetic poles and running essentially parallel to the surface once sufficiently far away from the magnetic poles.
Another factor to consider is the changing position of the Earth’s north magnetic pole. I checked our Wikipedia cache and found that the pole is moving fairly quickly (55 to 60 km) a year northwest per year. Many maps show the magnetic north pole near Ellesmere Island, Canada, but by now it is far offshore, at approximately 86.3° N, 160.0° W. Compare that to our position yesterday and today and you’ll see that we are nearly on top of the Earth’s north magnetic pole! So a hiking compass’s needle, designed to line up with magnetic field lines horizontally (or nearly so) along the Earth’s surface, won’t feel such a pull anywhere in the vicinity of the magnetic north pole. To find the Earth’s magnetic poles, an instrument such as a magnetometer, which can measure the strength and direction of magnetic fields, is employed.
TODAY’S JOURNAL:
We’re stopped for a relatively short repeat hydrography station that was stretched a bit by the need to re-terminate the starboard A-frame cable. As has been the pattern, we found an open lead to stop in, making the cast easier to prepare for and conduct than if we had to crunch open a sufficient pool to work in. It has gotten very windy but the snow has stopped for now.
On yesterday’s ice station I took some lessons learned from the prior two for using my GoPro camera through the ice to try for some footage of this hidden world. I had two strategies to try and happily both went pretty well. The first was to clamp my camera to an aluminum pole normally used for fending off ice during an instrument cast. There’s one on deck that had broken in half, a nice manageable 3 meters or so long, that I decided to use. With this pole I can lower my camera down the large (8-inch diameter) hole drilled by the beryllium pumping team for their sampling. I can also “steer” the camera, turning it in various directions and adjusting its depth while it is under the approximately 1.3 meter-thick ice.
Mark Stephens watches as Bill Schmoker lowers a GoPro camera on an aluminium pole through the sea ice at a beryllium-pumping station.
The other idea I was able to try was to lower about 9 meters of paracord line down the hole, weighted at the end with an eye bolt. Using an idea from Kyle Dilliplaine I clamped my GoPro to a short length of 1” PVC pipe, which Tim Kenna kindly loaned me. When I was set to go I let the camera slide down the line on its PVC pipe rider, angled to look up as it went.
Both methods are “flying blind”, since I can’t see what the camera is seeing until I get back to my laptop on board the Healy. So I try different angles and depths, hoping to see something of interest later. On yesterday’s outing I recorded about 40 minutes of video. I found several things living under the ice that I thought were pretty cool. There is a real contrast between the windswept, highly changing conditions of the surface and the protected, much more constant conditions found under the ice.
The first thing I found right under the ice on my GoPro footage was long, ropy strands of brownish algae. This turns out to be a type of algae called a diatom, in this case a species known for its slimy masses growing under Arctic sea ice called Melosira arctica. Diatoms are one of the most important types of phytoplankton in the world’s oceans but other kinds can be found in fresh water and other wet environments. Each diatom cell lives in a thin silica shell, some incredibly ornate. Perhaps you’ve heard a saying about living in glass houses? (If you do, don’t go throwing the first stone!) Well, that’s essentially what diatoms do. It was neat to see the Melosira arctica in its natural condition because they’ve been frequently tossed up to the surface on flipped blocks of ice left by the passage of Healy.
The Arctic diatom Melosira arctica forms into ropy, slimy strands under the sea ice. The brownish algae can often be seen on the underside of ice that has been flipped up by icebreaking activity.
The next highlight was a small, pale fish that came up into the bottom few centimeters of the hole drilled through the ice. We didn’t notice the fish, since the top of the hole had slushy ice in it, but when I lowered my GoPro facing down it caught a glimpse of the wee beastie swimming around and then back down out of the hole. The species is the northernmost fish known, an Arctic cod (Boreogadus saida.) Arctic cod forage for plankton right under the ice, somewhat like flipped versions of bottom feeders. A few folks have seen them come up in our wake along with blocks of ice as they tip over. I hadn’t yet seen one, and I’m glad this one wasn’t in any distress.
An Arctic cod inspected the bottom of the hole drilled in the ice for beryllium pumping at our last ice station. Next to the pale fish the blue hose for pumping sea water up to the beryllium filter and the braided line used to lower the CTD for the pumping operation are visible.
The last organism, and a real treat to see, was a ringed seal (Pusa hispida) that swam over my GoPro while it was down the line looking up at the surface of the ice. I was nearly done going through the ~40 minutes of video when a dark graceful form swam fluidly across my computer screen. I almost fell out of my chair in surprise and delight. We hadn’t seen any seals in the area, but when polar bears are a real concern you don’t grow old as a seal hanging around in plain view! Ringed seals eat Arctic cod, and are one of the main species preyed upon by polar bears. I speculate that the seal swam by in curiosity to see what was going on in its normally undisturbed sub-ice world.
The best surprise of the video I recovered from my GoPro was this ringed seal that swam over the camera while it was deployed about 8 meters deep, looking up at the ice surface.
These examples show that there is plenty going on under the vast white plains and ridges of Arctic ice that we have been traversing for the last several weeks. Usually these organisms are hidden and protected by the lid they live under, so it was a privilege and a treat to get a glimpse into their world. The screen shots I’ve used in this post don’t do them justice, so stay tuned for my return home when I’ll post the video (and many others from the expedition.)
GO DEEPER!
Ringed seals are gifted swimmers, but can fall prey to polar bears. How can a polar bear catch a ringed seal?
Aloft Con web cam updated every hour
Healy Track
That's all for now. Best- Bill
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