A aediment collector from a mooring
I stayed up later than was sensible last night to watch the last of the sampling tasks — grabbing a chunk of sea-floor sediment. This started at 1 a.m., and it was dark and cold on the foredeck of the Amundsen.
Robbie Bennett from Natural Resources Canada was in charge of the operation. They were using a device called a "box corer," which is dropped on the ocean floor using a large winch. The corer has a half-metre-square box, open at the bottom, which is driven into the sediment on the sea floor. At that point, a weighted shovel sweeps across the bottom of the device, closing it and sealing in the sediment sample.
At this site, the corer had to be dropped 450 metres to the sea floor, but they've done sampling in waters 1.5 kilometres deep. Depending on the location, these samples could represent thousands of years of sediment deposition of everything from atmospheric dust deposited on the sea and sunk to the bottom, to material from melting sea ice, or just the remains of plants, animals and possibly microbes and viruses that have died and sunk over time.
If they're lucky, occasionally they pick up some hapless bottom-dwelling worms or a brittlestar, which is related to the starfish. This sample, of course, just looks like gray ooze, but that's doubtless a failure of imagination on my part. I was a little tired and fairly certain my fingers were going to need amputation after what seemed like hours on deck, clutching a microphone.
Amundsen's lifeboat and Heron launch
Today was a relatively quiet day for most of the research teams, but busy for the groups doing underwater mapping. The day was spent steaming back and forth across De Salis Bay on the southwest coast of Banks Island. At dawn, one of the ship's survey launches, the Heron, set off to go into shallow waters and use sonar to map the floor of the bay. The sonar used on the Heron and the Amundsen are multi-band systems sending out a fan of sonar signals that can see a swath of sea floor roughly three times the depth of the water the boat or ship is travelling in. The small launch charts water down to only a few metres deep.
The Amundsen stays in deeper waters, averaging between 40 and 50 metres, but the crew was keeping a sharp eye out. This bay hasn't been charted in detail – that's what the ship is doing at the moment – so encountering a navigational hazard like an undersea hill or shoal is possible. The Amundsen needs about 20 metres of water below, and grounding would be a bad idea. This is an icebreaker, not a rock-breaker, and we're a long way from assistance.
Survival suit instruction
I'm feeling a bit tense about all this just now, because this afternoon we did a long safety tour, looking at the watertight compartments, the lifeboats and the firefighting equipment, led by the second lieutenant/safety officer who has a flair for the dramatic and seemed to take an almost gleeful interest in just how long we'd last in the water without equipment. This was followed by a demonstration of how to get into a survival suit, should it become necessary. After watching some volunteers on the tour try to struggle into these suits (an operation that looked like it would require four arms, involve three pulled muscles and result in two possibly dislocated joints), I'm now one intimidated radio producer.
The Heron, sonar bottom mapping vessel
Anyway, to get back to the subject of sonar mapping, all this will potentially be used for navigation in the future, but the main point of the inshore mapping in particular is to try to reconstruct the geological history (and possibly future) of the coastline up here. That's because a lot of the coastline is expected to change, perhaps quite dramatically, as the Arctic and the planet warm. Climate change is expected to have two different effects that will influence sea level.
The larger effect, at least in the immediate future, is the melting of the Greenland ice cap, which is accelerating, according to recent studies, and the Antarctic ice cap, which we know less about. But if they continue to melt, all of this new water, previously tied up on land as ice, will be added to the oceans.
The other effect is thermal expansion. Warmer water is less dense and takes up more volume than colder water, so as the surface waters of the world warm (an effect that's likely to be most pronounced in the Arctic), the warmer water will take up more room, and sea levels will rise.
This is going to be an issue worldwide, but it's a little more complicated in the Arctic, thanks to the geological after-effects of the last ice age, and a phenomenon known as isostatic rebound. During the last ice age, which ended roughly 12,000 years ago, much of Canada was covered in huge, kilometres-thick ice sheets. These ice sheets persisted longest in the North. The massive weight of the ice actually pressed the land down into the earth's crust, and as the ice melted, that pressure was released, and the land started to rebound back up, even as sea levels rose.
So there was something of a race between land and sea. Sea levels stabilized for thousands of years, but the rebound of the land is continuing to happen today in some areas. Now sea level is rising again in the Arctic, but because of this continuing rebound, so are parts of the land. That means in some areas the race is on again, and it's not clear which phenomenon will win.
All of this, of course, is particularly important for the local communities, which is why much of this mapping is being done. By looking at different areas that were inundated by glacial melting 12,000 years ago (where rising sea levels from melting ice won the race against rebounding land), the geologists aboard hope to find patterns that will predict how the coast will be affected in the future. So today's sonar missions are mapping the bottom of the bay, looking for old beaches, lagoons, lakes and rivers that might have been flooded at the end of the last ice age. If they can see where and how the flooding occurred, then they can perhaps tell people how their communities might be at risk and might then best deal with rising sea levels.
One final note about the sonar. I first noticed it almost as soon as I entered my cabin. There was an odd sound — sometimes like a cricket, sometimes like a budgie, and sometimes like someone bouncing a ball bearing on a marble floor. Sometimes there was also an echo, fractionally later. It turned out to be the sonar, which sounded nothing at all like the familiar "pinging" sound from submarine movies. The sonar never goes off. So 24 hours a day, this clicking sound reverberated through the lower levels of the ship. I was surprised how easily I blocked it out. On occasion, I thought it had actually stopped, but as soon as I focused on it, it was back again. On other occasions (when I was trying to fall asleep), I couldn't stop listening to it. There's a lesson in perception in this somewhere. Google "auditory adaptation" and I think you'll discover the psychology of the phenomenon, though I can't be sure, since I can't Google anything from the ship, which is a real adaptation for an internet junkie like me.
— Jim Lebans, just inside De Salis Bay, aboard the Amundsen
