Friday, 12 August 2011

The Day After Tomorrow - A student's film review

I have spent rather a lot of time over the past month or so with my head in textbooks and papers etc. to help me try and get to grips with some of the basics of oceanography (trust me, it is literally like a whole new science) and so I fancied a bit of a break from the heavy reading. Therefore I thought I would watch the film The Day After Tomorrow......
This film is based on the events that follow, rather rapidily, the shut down of the Atlantic Meridional Overturning Circulation (AMOC) and a shift in the Gulf Stream as a result of global warming triggering the melt of ice shelves, with the collapse of the Larsen B ice shelf being the example in the film. In the film this leads to the onset of a new Ice Age where tornadoes flatten Los Angeles, tidal waves engulf New York and the entire Northern Hemisphere begins to freeze solid, forcing millions to migrate rather quickly as far south as possible. Stuck in the middle of all of this is a small band of survivors who have to ride out the 'superstorm' in the shelter offered by an old library whilst they wait for the father of one of the survivors, also a climatologist, to come and rescue them.

Now obvisouly this film was produced to be entertaining and so presents the extremes, and perhaps not quite reality and essentially it is this trait that makes it a good film to watch for geography as you can allow it to really test your knowledge. Its one of those films that, from an educational point of view, you have to watch and then point out the geographical mistakes made - quite an interesting challenge really (just do it when you're on your own though as, from experience, I have learnt that not everyone will appreciate an indepth explanation every 5 minutes as to why something would/could probably never happen in real life!). It is because of this that it really helped me consolidate some of the basics that I had learnt so far, in relation to my EPQ, and by doing this I could see the areas I had clearly understood well and others not so well - I might have to look out for films which would allow me to do this for topics on our syllabus as a different way of revising! For now though, I think I will write a little about the science behind the film and hopefully explain the basic priniciples that the film is based on.

At the beginning of the film, you see footage of the collapse of the Larsen B ice shelf. This actually happened in 2002. Larsen B was 200 metres thick, with a surface area of 3,250 square kilometres and all 500 billion tonnes of the ice sheet rapidly disintergrated ; thus making it the closest thing to a modern day Heinrich event we have ever witnessed. Not only did this result in a large freshwater water input as a direct result of the ice shelf collapse but it also resulted in a two-to-six-fold increase in the centreline speed of the four glaciers that flow into the now collapsed section of the Larsen B ice shelf - basically a lot of freshwater entered the sea as a result! It is this event that the film suggests caused the shutdown of the AMOC and although technically the large freshwater input would have had an impact on it, the freshwater from the disintergration of Larsen B didn't really affect the AMOC. This event, therefore, demonstrates the importance of the location of the freshwater input. The most sensitive areas of the THC are those where the sinking occurs, so in the Atlantic, up near Iceland etc.. The freshwater from Larsen B didn't reached this high latitude in the Northern Hemishpere due to the Antarctic circum-polar current which prevented it from spreading that far and therefore from having a large detrimental impact on the general oceanic circulation. Why could a freshwater influx effect the THC? Well, it is all to do with density and a freshwater input would upset the differing densities of the water and so prevent or weaken the formation of deep water and thereby effect the entire thermohaline circulation. In turn, this would alter surface currents, such as the Gulf Stream which dictates our climate, as it would reduce the movement of warmer waters to the higher latitudes in the Northern Hemisphere, allowing for greater sea ice formation and provoke the Gulf Stream to shift southwards. This would have a huge impact on the climate of the Northern Hemipshere and greatly reduce the temperatures experienced in the UK and countries of similar or higher latitiude. However, this change would not occur on the timescale portrayed in the film!!! This is, I suppose, the foundations of the science that the film tries to base itself on, although, as it is a film, scientific content is lacking but I will leave that for you to discover yourself!

So, is it a good geography film? Well, if you approach the film as one to watch with the aim to point out the geographical errors and try to add science to what you see, then yes. There are a few scientific mistakes to be found and the film does portray the extremes of what could happen if the AMOC was to weaken or shut down - a possibility in the future as it has happened in the past. You definitely get the idea that allowing a large volume of freshwater to enter the Atlantic is a dangerous thing! Like I said above, I found watching and then picking out the mistakes, quite a good way to consolidate what I have been trying to teach myself  and doing so was kind of like quite a good revision technique - something I might try again in the future!

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