Category Archives: Ice Cover

As has been mentioned before on this blog, Dr. Renske Gelderloos, from Oxford University, is a fellow traveler on the CCGS Larsen this summer.  She, too, is blogging about her experience.  Below we reblog her post on the helicopter trip, another exciting and beautiful account of doing science in the Arctic, this one even with a couple pictures!  [Note that the pictures in the blog post are from other trips to the same area — limited internet connectivity to the ship does not permit transmission of current images.]  We will post some of her other entries here, but you can find her blog directly at this link.

Nares Strait from the air, and the first CTD section

5 August 2012

Today started with a nice surprise! During the eight-o-clock science meeting after breakfast the chief officer popped in to say that the helicopter would fly out for an ice survey and that it could take two extra passengers. I immediately volunteered, and as Allison and I had never flown in a helicopter before we would be the lucky ones today.

Ice along the Ellesmere Island coast viewed from the helicopter during an ice survey in 2007.

Together with helicopter pilot Don and ice surveyor Erin we flew off in northeasterly direction. Erin’s job was to maps the ice conditions in the channel ahead of the boat, and see whether there was possibly a better route (less ice-covered) for the boat to take. As Hans Island lay in the helicopter range, we decided to land on this island and do a quick check of the weather station there. The weather station looks like a pole on the top of the island (Hans Island is basically a bit-oversized rock…), firmly held down to the ground with three strings. On top of the pole is a weather vane that also measures the wind speed, and attached to the pole on other heights are a thermometer and a fancy measurement device that measures the incoming solar radiation. The pole also has batteries and a solar panel to provide electricity, and a communication device that sends the data to the more populated part of the world so that it is available immediately. This is unlike our oceanographic moorings under water, which we need to physically recover on the site before we can get the data. Dave had asked us to take photos of the instruments, so we landed the helicopter for a close look. All the instruments appeared to be in remarkably good shape. The previous time this weather station was serviced a polar bear had taken a fancy on it, but fortunately none of the kind had happened this time. When we had done all our duties we flew back over Ellesmere Island to see a glacier from closer by: astonishing!

At the end of the day we finally arrived at the site of our mooring array. As we need the deck crew for mooring recoveries (in particular for the crane and the FRC, which is the small inflatable boat that can be launched from the ship), and the deck crew on Canadian coastguard vessels works from 8 to 5 on weekdays, chief scientist Humfrey decided to do a CTD (Conductivity-Temperature-Depth) section first. This had the additional advantage that we would have the CTD data from this section and the moorings overlapping for an intercomparison between the two.

The multi-coloured mountains of Ellesmere Island

Around 7 o’clock in the evening we were ready for the first trial cast. We had already done ‘dry’ tests, which means we just checked whether the computer was willing to talk to the CTD sensors and the other way around, and whether the values we got were somewhat reasonable. The quantities we measure are the conductivity, the temperature and the pressure. From those quantities we can calculate the salinity of the water (the other way to measure salinity is to take a water sample and take it to a laboratory, so by using the conductivity of the water we can measure the salinity at every location from the surface to the bottom which gives a lot more information than just a few samples), as well as the density. For a CTD cast the sensors are tied to a frame, and the frame is lowered, using a winch, from the deck to the water and subsequently from the surface to just above the bottom of the ocean. The data is sent to our computer real time through the cable that is holding the frame, so we can do a visual inspection and get all excited during the cast. After the trial run things started to really speed up and everyone took up a task. Humfrey supervised, Jo did the winch, Dave (after a subtle hint) kindly provided tea with goodies (thanks Dave!), I monitored the data on the computer screen and made sure the data was saved, and Andreas did a quick-and-dirty first post-processing of the data which enabled us all to see the results of our measurements in almost real time. Just before midnight the section was completed, I took some pictures of the midnight sun and we could all go to sleep.