Week 6

Weddell seal helps deploy sediment traps

Using a paddle and boat to get to the sampling site © David N Thomas

Using a paddle and boat to get to the sampling site © David N Thomas

During previous visits to pack ice regions I have experienced many wonderful, and on occasions, highly peculiar moments. However, paddling a half-inflated rubber boat between ice floes has to be one of the most surreal. One of our study sites has completely broken away and there is a ten metre wide stretch of water to cross before we can reach it. The only way is by boat, and sitting in a small rubber boat gives a whole different outlook on sea ice research, especially when a curious seal pops up to see what's going on. Why was the boat only half inflated? If it had been full of air and hard, it would more easily rip when coming into contact with ice.

A curious Weddell seal decided to make our sediment trap hole its home for a few days © David N Thom

A curious Weddell seal decided to make our sediment trap hole its home for a few days © David N Thomas

The week started with another odd moment when we went to investigate the hole we had made to deploy our sediment traps. To our surprise, a young Weddell seal was lying in the hole, and clearly enjoying having an access hole onto the ice already prepared for it. It was quite at home and even seemed to enjoy posing for the inevitable photo-shot.

The only problem is that seals produce copious amounts of droppings, and we dread to think what we will find in our traps when we pull them up in a few weeks time!

To complete the list of oddities, I went to visit the Belgium team as they sampled at their remote ice station. They are measuring the iron content of the snow and ice, and the possible role this may have in limiting productivity of algae in the ice and in the surface waters.

In order not to contaminate the ice, some researchers have to wear snowman suits © David N Thomas

In order not to contaminate the ice, some researchers have to wear snowman suits © David N Thomas

This is a rather tricky element to measure since it is so easy to contaminate samples by contact with clothing and boots, and of course with metal tools that have iron in them. To combat this problem they use specially (expensively) constructed ice corers and work in special clean suits and plastic bags over their boots and gloves. They are of course doing very serious science, but it is rather difficult to watch these snowmen and women working without grinning.

As beautiful as the wildlife is, there are some downsides to coming up close to nature. We have a keen group of divers on board who are here to help deploy instruments under the ice, and to sample the underside of the ice for organisms that live within the ice-water interface. Unfortunately there are leopard seals in the vicinity, and having seen how these predators hunt and attack seals, it is more than understandable that the divers have to proceed with extreme caution. Naturally this is frustrating for the divers, who are itching to do their job, and for us too, since they have already collected some unique samples.

A scientist takes ice samples using a muscle-powered ice corer © David N Thomas

A scientist takes ice samples using a muscle-powered ice corer © David N Thomas

The assemblages of algae and zooplankton living on the underside of ice floes are living in a fragile ice matrix that we normally cannot sample as we core down from above. The divers, using re-breathing apparatus to cut down on the disturbance by bubbles, are able to sample this delicate layer with the minimum of disruption. For instance, we are seeing species of algae in the divers' samples that we would never have thought would be associated with the ice.

On Sunday we celebrated the halfway point of the expedition. In the evening we had a wonderful meal, followed by a celebration that went on (for some) until the next morning. The party served to accentuate how little time we really have left, and we are even more earnestly fighting hard to get all the sampling done that we set out to achieve. On the other hand the event highlighted that we are getting closer to coming home: as spectacular and exciting as our experiences are, and no matter how intriguing the scientific issues we get to address, how much better it would all be if we were together with those who we love and cherish.

David Thomas
17th December
68°S 55°W