Planet Earth Online - Surveying Lake Windermere
Richard - It really is a beautiful day here on Windermere. Around the centre of the lake, you've got the trees above the water line and the green hills beyond that, and then the mountains. I'm onboard the White Ribbon which is really a slightly large day boat, if you like, but rather than people with picnics, it's crammed with computer monitors and scientific equipment. With me is Carol Cotterill from British Geological Survey. Carol, what are you aiming to do here?
Carol - One of the aims that we're looking at is the lake bed itself and the modern day processes that are going on, both sedimentary processes, but also, the habitats for the fish, in particular, the Arctic charr. We also want to know what's going on beneath the lake bed so what happened in the past, in particular during the last Ice Age when the British ice sheet came down this far. So did it leave a series of moraines, how quickly did it retreat, and what we can tell about the glacial processes and any changes to the watershed in the drainage into the lake since that time.
Richard - Now we're standing on the aft deck here, but beneath us, there's a hole.
Carol - Yes, that's actually a moon pool. That's what it's called and it's quite unusual on our vessel of this size. Normally, you find them on much larger drilling or geotechnical ships. But here, we decided it was much safer for the equipment if we actually carved a whole in the centre of the boat and we can now deploy our equipment down through the centre of that, so we can keep an eye on it basically and it's semi-protected.
Richard - So if we peer down through this hole, you've got an instrument here suspended beneath the surface of the water. What's that measuring?
Carol - It's painting a picture of the seabed using sound. So what we have are two sonar heads that are angled, opposed to each other, and they send out a number of beams. In total, we have 508 beams. So 508 sound waves effectively radiate out, or pings, as we call them, and when they hit the seabed, they bounce back off the seabed or the sediments or anything on the seabed, and then they come back to us and we hear their returns. And from the time it takes for the sound ping to bounce down and come back to us, we can then calculate the depth that that is.
Richard - Now, we go inside. I think we can see some of the results as they come in. Let's follow the cable from the instrument, into the cabin here and here's Nick Smart and you got two large computer monitors in front of you with this very pretty colour patterns in three dimensions, but that's what we're looking at now, is that right?
Nick - It's directly what's below the boat. We are running along the edge of the contour at the moment. You can see the change in depth which is illustrated by the difference in colours. The red is showing a slightly shallow area then as it gets deeper off to our left-hand side, it goes to the blue.
Richard - Carol, what have you found so far? I was quite surprised when I looked at these that there was a bump in the middle of the lake.
Carol - Across the central section where the current ferry runs, there's actually a high in the lake bed which some to only 2 metres water depth, it's very very shallow in certain parts. We think that this is a remnant of this glacial path that I mentioned before, adn that this could be where there's more solid bed rock that the glacier, the ice sheet, couldn't wear down through.
Richard - This is material the glacier would have dumped there, but it's right across the centre of the lake?
Carol - It is. It is right across the centre of the lake and we've seen it in both the north and the south basin as well, much smaller examples. So material that has come down with the water coming out from the water underneath the glacier so you get this sort of outwash of debris that the glacier's ground up as it's been on it's journey and it leaves these big ridges that are called glacial moraines and there are a number of different types of moraines. In this lake, from a very preliminary interpretation we think we've got terminal moraines which are at the snout or very edge of the glacier but also a series of De Geer moraines that build up underneath the glacier.
Richard - What's the point of doing a study like this?
Carol - It's trying to understand the history and how the lake has evolved, how it might evolve in the future, how the species that live within this lake work with this habitat. Are there certain areas that they prefer to spawn or to feed? Is there the stratification that we find in the lake from temperature, so the top getting much warmer and the bottom quite cooler. Does that have an impact on the species? So it's a whole number of different things.
Richard - You're also looking for a monster here.
Carol - Yes. When we came down and we launched the boat, just over a week ago, we were talking to the lake wardens who were helping us and have provided their jetty, and they asked us to look out for Bow-nessie.
Richard - Bow-nessie?
Carol - Bow-nessie. Apparently, there have been sightings of Bow-nessie and I'm shown some photographs that one of the wardens took a couple of years ago.
Richard - But no sign yet?
Carol - No sign. Bow-nessie has been quite elusive so far and I think she hears us coming and just scurries away to the deeper parts where we're not working.
Chris - And they're still hunting for that, their monster. That was Carol Cotterill from the British Geological Survey and she was with Richard Hollingham, and they were aboard White Ribbon which is the boat surveying Lake Windermere.