First up was a very interesting discussion with a researcher about ice sheets. There is currently a lot of uncertainity about ice sheets and their stability, with much of this uncertainity stemming from a lack of understanding of the mechanisms for ice sheet melt. Currently, it is believed that Antarctica is the most likely to experience significant melt and this is because much of it is under the sea. If the proportion that lies below sea-level was to melt, which scientists think could occur over the next few hundred years (although this may sound quite slow, it is considered to be rather rapid!), it would raise global sea-level by 6 metres!!! Greenland melting is an area that often recieves much attention, perhaps becuase we are unsure just how much freshwater could be released or how quicly it would occur, but for now alteast, many feel that a large freshwater input is unlikely. Before this discussion, I had never really given much thought to the influence that the angle of the bedrock, upon which the ice sheet lies, on melting but it does, in fact, seem to play quite a large role. The bedrock that the Greenland ice sheet lies upon slopes away from the sea, whilst that in Antarctica slopes towards the sea and thus making runaway melting possible. When the Laurentide Ice Sheet existed it was sat upon 'flat' bedrock, something that many considered essential for the occurence of Heinrich events. Due to this, depsite the fact that models currently cannot replicate Heinrich events, it is believed that this current climatic state cannot provoke Heinrich events. The fact that surprised me the most was that increased surface air or sea surface temperatures, as a result of global climate change, are not the biggest threat to the stability of ice sheets and would not be responsible for instigating the greatest volume of melt. Instead it is increased wind speeds.....but why?  |
| This is a bit of an exaggeration of what happens but hopefully you get the general idea.... |
Well, increased wind speeds would raise the height of local sea-level and increase Ekman Pumping. Increased Ekman Pumping would provoke old warm waters from the deep ocean to be dragged closer to the surface and over the terminal morraine, which marks the end of glaciers or ice sheets, and towards the base of the ice sheet, thus causing melting to occur. This is believed to be responsible for more melting than raised surface air/sea temperatures. One thing that scientists are unsure of though is what happens to the warm water once it passes the terminal morraine. Does it hit the base of the ice sheet and then continually circle, gradually melting away the base or does it bounce back off and return to the rest of the ocean? Understanding this is, again, crucial if predictions of ice sheet melt are to become more cetain..... Anyway, all of this 'stuff' is important if scientists are to make more certain predictions of the future of the MOC and there is a lot of debate over just how much of an impact melt of Greenland or Antarctica would have. Most focus is placed on Greenland, as a result of its location. Some feel that perhaps, if enough of Greenland melted, it could significantly reduce the MOC intensity whilst others believe that, due to existance of sinking sites either side of Greenland, that Greenland melt could provoke a switch in sinking sites to the western side of Greenland - a switch that could have the potential to actually warm the UK during winter. There are a couple of other quite specific topics that we covered but I think I will leave them for another blog post.
After this I attended a Modelling Team meeting which was quite interesting as it provided an insight into some of the work that researchers at the Met Office are currently doing and some of the problems they are facing at present. Following this I had a chat with someone regarding ENSO, a topic that fascinates me, and as, again, there was lots that we covered,and I am a bit more confident about talking about ENSO, I am going to write another post solely on this. The afternoon was finished off with a chat about the relationship between the ocean and atmosphere and how this relationship is replicated in models. The relationship between the ocean and atmosphere is really really complex and I literally touched the very very basics. The ocean is sort of like the memory of the Earth climate system. The atmosphere cannot store things, like signals or changes in climate, and so instead it passes the signals on to the oceans. The oceans can store this information for hundreds and hundreds of years, whilst it circulates them around the world, and then passes the signal back to the atmosphere where it provokes a short term, but rapid, response. This coupling is crucial for many things such as ENSO. It is tricky to model all of the processes that link the oceans and atmosphere and all of the exchanges that happen between them (I am in the process of writing a post on the real basics of climate modelling as it is like a whole new science).
I apologise as I realise that all of my posts regarding my time at the Met Office have been a bit all over the place but I honestly learnt so much and I am not that great at explaining things. Despite this, I still hope they have been interesting to read and have given you a bit of an insight into the work done at the Met Office and some of the things I was fortunate to do whilst up there. I really cannot thank the people who made this whole experience possible enough - I learnt an unbelievable amount, gained some invaluable advice universities courses and careers etc, got to meet some great and highly intelligent people and simply had just an amazing time!!!
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