Saturday, September 28, 2013

Scott Inlet - Getting to work

The bear looking annoyed with us
This is my third installment about this years field work. First is here, second is here.

A polar bear sleeping on a rock greeted us the first morning in Scott Inlet. The bear wasn't happy to see us as we rudely brought the ship in close to get a good look at him (a young male). The bear got up and moved further up the slope, casting disdainful glances our way. So far, I've seen a polar bear every time I've gone to the Arctic.

Steep faces on each side of the inlet bracket the narrow band of water of the inlet. The orange and black stained cliffs are high enough that base jumpers use the area – how they get up the cliffs in the first place baffles me, gaps to climb up were rare and filled with glaciers dripping in slow motion towards the sea. The inlet walls would fit the landscape in 'Game of Thrones' north of the wall, or exist in Middle Earth. Off one of the cliffs flows the most peculiar waterfall I've ever seen. It cascades off the top, then vanishes mid way down. Does the water freeze into snow? Where does the water come from? Below the water was just as shear - our depth sounder listed depths around 200 m and greater only a short distance form the cliffs.

Cliff face at Scott Island
The inlet appeared strangely devoid of life. A few Arctic Fulmars glided by, but never conglomerated around our ship even when we were offering up a free lunch (excess bait squid). Olive green jellyfish about the size of baseballs bobbed in the water. We knew narwhal were in the area, but never saw them – perhaps our depth sounder scared them off.

In 2012, three lines of receivers to listen for tagged fish, plus my two oceanographic moorings and some marine mammal listening devices were left in the water (to a total of 36). We came prepared to re-install these moorings plus add four additional receiver lines. As a result, the back deck of the ship was consumed with 200lb anchors weighing the aft end down. The first order of business was to deploy a batch of new receiver moorings before recovering any.

Instead of depth contours, the chart only listed a few depth soundings leaving most of the bottom topography to the imagination until mapping could be completed (the Nuliajuk is heavily involved in mapping when not doing our work). Depths for the mooring locations were needed to ensure we used the right type of float (non-compressible floats for the deeper moorings). As we checked depths, I did a line of CTD casts. Then we turned around and deployed a line of moorings. A process we repeated several times over several days.

Once the deck was cleared a bit we began recovering the previous year's moorings. Each mooring was fixed to its anchor with an acoustic release, essentially a hook with enough electronic brains to respond to a code sent from the surface and open the hook. Attached to the release is a length of rope holding the instruments ending in a float. From the ship, we call the release and have it uncouple – then the instruments are pulled to the surface by the float.

Several of us kept look out for the floats as they popped up. When a float was spotted, the zodiac zipped over and pulled in the mooring then transferred it over to the ship. Once the mooring was on board, we cleaned them up – an easy task as nothing much grew on the mooring lines and instruments. If we had put these instruments in temperate waters we'd be scrubbing matts of seaweeds and mussels off. Instead, there was a light growth of algae that wiped off with a towel.

One of my moorings - nothing fancy
One of my thermistors flooded. When I opened it up the batteries we so corroded I couldn't read any of the writing on them (batteries were removed carefully avoiding the battery acid). The rest of the instruments were fine. I downloaded each instrument, changed the batteries and re-programmed for a another year. I only briefly looked at the data to check if each instrument worked properly (I'll spend the next while looking at the data in more detail).

Kevin (another scientist) and I tackled the marine mammal recorders, instruments I had never worked with before that use large numbers of D cell batteries. By actually reading the instructions, we readied most of them for re-deployment. Unfortunately, one instrument needed a specialized wrench, which we didn't have. The wrench was to arrive with our replacements, so I assume it has been dealt with by now.

The mooring work was a success – all the moorings from 2012 were recovered and more moorings were put out.

Next up, some fishing...

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