Learning about Antarctica Part I
A couple of weekends ago I spent the weekend at Lake Ohau, attending a seminar for media hosted by the NZ Antarctic Research Institute.
NZARI is a charitable trust (launched by John Key in 2012) which partners with research agencies to develop a global understanding of Antarctica’s impacts and vulnerability in a changing global climate. It focuses especially on Antarctica and the Ross Sea and its job is to achieve the NZ government Antarctic Science Strategy.
As you can see Lake Oahu is a beautiful place to be, albeit rather cold in May. It was chosen as a location for the seminar, as it is a glacial lake itself, and the location for a lot of scientific work examining NZ’s past climate.
The purpose of the seminar, or winter school, was to explore what it would take to melt an ice sheet. However this wasn’t just a series of talks – we actually got to play with ice and buckets!
The total spend by the Government on Antarctica is around $20 million a year, which includes Scott Base, staff, and the 27 different science programmes we are involved in. So that’s around a cup of coffee per person in spending.
As home work we read five scientific studies on melting ice in Antarctica, plus a Guardian article.
The most useful of the scientific studies was this one titled “Accelerated West Antarctic ice mass loss continues to outpace East Antarctic gains“.
Going into the weekend, I had many questions about the studies, including:
- How do they accurately measure ice mass?
- Why would some parts of Antarctica be shrinking and others growing?
- Is it only a problem if there is shrinking everywhere?
- Isn’t the amount of shrinking far less than the annual change in sea ice cover?
The first question was answered by Nigel Latta, who spoke to us on the Saturday evening. Basically the continent is measured by satellites in space, which can detect minute gravitational changes caused by the land mass below being smaller or larger.
The issue of the changes being much smaller than the annual change in sea ice was also quickly cleared up also. Basically there are three types of ice structures and they are all quite different. They are:
- Sea ice – this is basically frozen seawater. It floats on the water and covers 12% of the world’s oceans. It does massively change during the seasons of the year. in the Arctic it can go from 5,000 cubic kms to 25,000 cubic kms.
- Ice shelf – a thick floating platform of ice that forms where a glacier flows down to a coastline and onto the ocean surface. Ice shelves are from 100 to 1,000 metres thick.
- Ice sheet – a continental glacier ice structure of at least 50,000 square kms. Think of this as ice on land (even if some of it is below sea level).
Now when it comes to West Antarctica and East Antarctica, it is important to note that West Antarctica is mainly on sea bed below sea level. East Antarctica is not.
So what does this mean? Well we did some experiments under the supervision of Gary Wilson.
We all got given a two litre block of ice, which we weighed and then placed in large containers. They were then arranged as follows:
- Ice in the shade (control)
- Ice in the sun
- Ice in the sun with dust on it
- Ice grounded in fresh water
- Ice grounded in salty water
- Ice grounded in warm fresh water
- Ice grounded in warm salty water
- Ice floating in fresh water
- Ice floating in salty water
- Ice floating in warm fresh water
- Ice floating in warm salty water
During the day we would weigh our ice blocks every hour, to track which ones were melting faster or slower than others.
The results are above, and what they showed was that the factor that makes the massive difference in speed of melting is whether the ice is just grounded in water (had around an inch depth around it), or whether the ice was floating in water. When you have water underneath the ice, it melts far far quicker. This is more significant than whether it was fresh or salty, or warm or cold – even though they also had an impact.
So what does this mean for Antarctica? Well this is why West Antarctica can be melting, yet East Antarctica can be staying the same, or even growing in places.
So if you think that there is not a potential issue with the West Antarctica ice sheet, because you’ve read that East Antarctica is growing or stable, well think again. Because WAIS is more exposed to the ocean, and because the ocean is warmer than in the recent past, there is a melting effect.
I’ll look into what the impact of this melting could be in future posts, as well as a fascinating look we had of photos of core drilled up from 300 metres below the surface of Antarctica, which gives us a picture of what happened to the continent over the last 2.7 million years.