The Glaciology Group at Swansea University are engaged with trying to understand what controls the way glaciers and ice sheets change over time, especially in response to climate. This is important for many reasons but in particular, ice that sits on land represents a huge reservoir of water than can influence sea level.
One of the team, Dr Timothy D. James, is busy measuring changes in these ice bodies over the longer term (up to 80 years) using old aerial photographs and satellite images. More recently he has become interested in using timelapse photography as a really inexpensive way to measure the changes at the front of a glacier where it terminates in the sea (a.k.a. the calving front). This is an area that is very difficult to measure because they are so dynamic and unstable. So in the summer of 2010, he was out in Greenland on the south shore of Helheim Fjord, which is accessible only by helicopter from the town of Tasiilaq. They installed cameras that would take digital photographs of Helheim's calving front every hour - picking up the cameras again in the autumn. The exercise has been repeated every year.
The glacier had been quite quiet in the summer of 2010 and the team had been told by colleagues not to expect much activity, which was a bit disappointing.
They had been in the field for 5 days and very little had happened. Only very small bits of ice broke off which could be heard but not seen. The team were camped about 4 km away from the fjord front. After 6 days they had installed two cameras that were running nicely and were installing the third camera when out of nowhere they a really deep rumble that was shooting down the fjord. They hadn’t heard anything like that before.
As the video shows, these icebergs at Helheim tend to fall over backwards. The glacier is about 800m thick at the front with only about 100m showing above the surface. This means that there is a huge face of ice that has to push through a lot of water. The early rumbling was the sound of all that ice floating in the fjord starting to move.
The timelapse, which is made up of a photo every 10 seconds, gives the impression that the calving event happened quite quickly but it was really surprising how slow it was. The first thing we saw was the ice breaking off (calving) across the fjord. It was definitely the largest event we'd seen. As this progressed, one of the team Dr Nick Selmes, thought he could see a crack forming along the whole width of the glacier. Indeed there was! There was so much noise... the team could hardly hear each other.
When ice calves off a glacier in such a way, it produces a pretty big wave. There are lots of videos of this on the web. When the fjord is full of ice the wave is considerably dampened but the currents it generates are significant. The floating ice started racing out of the fjord.
While providing important information about these events to scientists, the team are hoping that their video will help people understand the scale of these calving events. It's hard to grasp, even for glaciologists, the scale of an iceberg like this. They are HUGE. 1.5 cubic kilometres of ice came off this glacier in 15 minutes. The front of the glacier that came off was over 37 American football fields long. That's about the same length of Central Park. If you put all this ice into Central Park it would be over 300 m high... that's similar to the height of the Empire State Building observation deck. Even this, in the context of the ocean, isn't very much water but there are thousands of glaciers like this around the world. This is how glaciers can influence sea level.
Having said that, it is important for people to understand that an individual calving event is not evidence of climate change.
Large glaciers produce icebergs of this magnitude all the time not normally caught on camera though! What is important is how the size and frequency of these events change over time and what causes them to occur. We expected these events to increase with frequency and possibly size in a warming climate but that might not be the case as suggested by the recent paper in Nature by Faezeh Nick.
Clearly this is something that science still does not quite understand and the team are working hard to answer.
- For more information on the work of the Glaciology Group go to www.swansea.ac.uk/glaciology
- Monday 20 May 2013 18.33 BST
- Tuesday 21 May 2013 13.51 BST
- Swansea University, Tel: 01792 295050