Its been years since the ice fully melted in McMurdo Sound, as far up as Scott Base. Apparently, thats typical of sea-ice, some years it melts, others not, regardless of global warming. Ive talked to people who saw killer whales from the base, 'back in the day' when there was a big melt, but with that not happening nowadays, its Weddell seals that come up through holes in the ice and laze about for days on end, like immobile, overweight sunbathers. We were able to watch them for most of the season because their pups are born during September and October. Around the 2 month mark the pups are weaned and by this time will have learnt how to swim, hunt and haul themselves out of the water so will be ready to go it alone!
Weddell seals live the furtherest south of any mammal and are known for their deep diving – up to 700m, and able to stay underwater for up to an hour at a time. They do this by lowering their breathing rate and forcing air out of their lungs, which collapses them. They can look for food -fish, squid and krill, with deep dives, or spend the time underwater looking for cracks in the sea ice, which can lead to new breathing holes.
The seals stick to the ice-shelf side of the pressure ridges – where ocean meets land, causing the ice to push up into varied sizes and shapes of natural icy sculptures. So while easy to see from base, which was higher than the ridges, you couldn't really access them when you walked around the pressure ridges, however, just before I left I went on a walking trip from the base to get a closer look at the seals. It was late season, so being allowed to walk on the pressure ridges was no-more for the real threat of falling through thin ice, but as per usual with all organized trips, we had the safety aspect covered with a field safety member leading us. We all kept an eye out for cracks in the ice and any that did show up on our path were probed if they needed double checking. Luckily, we had a marine scientist at the base for a project he was working on, so he came along to. I'd sat with him the night before at dinner and had a great chat with him. Not only was his marine science background interesting but he'd worked a lot with the late Sir Peter Blake, what an inspiring conversation we had!
After our pre-trip safety brief we set off, seal bound. It took around half an hour or so to get near to where the seals were, and we weren't disappointed – there was at least a dozen of them. They barely noticed us, as they lay snoring and dribbling in their sleep. Such little movement from these obese 'pinnipeds', except for the one we saw coming up for air in the one available breathing hole.
In the past they were hunted for oil, food and skins and though their numbers are stable now their mortality rate is naturally high because they use their teeth to scrape away ice when they're making breathing holes, so once their teeth are worn down, they struggle to survive though lack of food.
We spent about an hour observing the seals before following our tracks back to base. Yet another amazing day out, especially as it was my last day in Antarctica.
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