We’ve been spending a few days prowling around the iceberg trying to find a suitable spot for landing. The weather has varied between days of glorious sunshine, but with wind high enough to make a swell that prevents mooring alongside, to calm days with fog and misty rain. Pulling alongside in any sort of swell risks damaging the ship’s side: on one occasion one of the crew had an unpleasant awakening with the wood of his wardrobe splintering as the ship’s side was pushed in a few inches during a particularly vicious bump. Attempts to land using small boats in inlets have been parried by strong river flows from the surface of the berg. Places that look good to land are often compromised by a large ice foot jutting out below sea level. These features can be one or two times the width of the ship, and if they decided to break off and float to the surface while the ship was moored above them, the situation would become very serious. One way and another, this particular iceberg seems to be determined to hang on to its secrets.
Ship-based work has been progressing well. We’ve finished an oceanographic survey around the iceberg, using the ship during the night when it’s not been used for other activities. These data will need careful analysis, but one feature that has been very obvious is the sharp change in water temperature and salinity at a depth of fourteen metres. This thermocline, which in this area is very near the surface, goes hand-in-hand with a change in density, and it’s on this density interface that we have seen strong internal waves. Internal waves are just like the waves on the surface of the ocean, except that they are under water. The characters of surface waves and internal waves are very different, as they depend on the change in density across the interface: the change in density across the thermocline is only 0.4% of the huge difference between water and air. Those internal waves have a period of several minutes, and can move the thermocline up and down by over five metres. When they arrive at the iceberg, they wash up and down the ice wall and might make a real contribution to the rate of melting. They were even felt by one of the divers when they were filming over the ice foot. Oceanographers normally only see the behaviour of the ocean through the lens of their instrumentation – it’s really exciting to listen to the reports from divers who actually experience these effects first hand.
Yesterday we finally managed to moor up alongside and get some instruments deployed on the ice surface, and also some fuel for use by the helicopter pilot who’s patiently waiting on Baffin Island. Whenever a group is working on the ice, we have a team of watchful observers on the ship, keeping an eye out for polar bears. There was one animal moving around in the vicinity while the moorings were being installed and while the instruments were being deployed, but it kept a healthy distance from ship and all was well. We’ve since had to move away from this mooring point, as the ever-changing circumstances became awkward again. There’s no doubt that getting onto the iceberg has been a great deal trickier than anyone ever imagined, but we’re optimistic that we’re going to get back “ashore” and win some great insights into the decay of these enigmatic leviathans of the ocean. Whatever else it is, it’s a great adventure.