Wednesday, 3 August 2011

Met Office Work Experience - Day 1 (for Monday)

I am an extremely lucky student as for a few days this week I will be at the Met Office in Exeter with the 'Oceans, Cryosphere and Dangerous Climate Change Gourp'; and today (Monday) was my first day! And, because this is such a privilege, I thought I would share with you some of the things I get up to and learn! You will have to bear with me on this thoughh as I can't even pretend to say that I understood everything that I heard about today - the vast majority of it went over my head - and I think my brain is still trying to take it all in!

One of the first things I did today was to sit in on a meeting of the Ocean Biochemistry Working Group whom, like the names suggests, do lots of research into the oceans - whether that be linked to ecocsystems or carbon dioxide uptake or DMS and lots more! Particular focus is placed on the factors affecing carbon dioxide uptake of the oceans and various negative feedback loops that they believe exist involing phytoplankton and temperature control (an idea I will come back to at a later date). This session was really interesting and gave me a really good insight into the work that some of the researchers at the Met Office do. Much of this research is based on calculating the amount of chlorophyll in the oceans and this can be linked to phytoplankton and plankton blooms. Due to its influence on global climate change, the study of such things is crucial in understanding likely future changes in climate. Phytoplankton take in carbon dioxide and is one of the ways in which the oceans take in carbon dioxide as it allows the carbon to sink deep into the oceans where it can be stored. This is an example of a biological carbon dioxide uptake process used by the oceans but there are also physical processes that are responsible for the ocean's uptake of carbon dioxide too. Carbon dioxide dissovles more easily in cold water that in warm water and it also dissolves more easily in sea water compared to pure water because sea water naturally contains carbonate ions (I will spare you from as much of the chemistry as possible at this stage!). The reaction of the carbon dioxide with carbonate produces hydrogen carbonate and because of this reaction, only 0.5% of the inorganic carbon in seawater occurs as carbon dioxide gas. Since levels of carbon dioxide are so low in seawater, more carbon dioxide can enter the oceans from the atmosphere. Something that I never knew before today was that carbon dioxide can be stored in 3 different 'forms' in the oceans and the oceans ability to do this enables it to store more carbon dioxide. Anyway, if the water stays at the surface and warms up as it moves around the globe, the carbon dioxide will relatively quickly escape back to the atmosphere but (this is where I can make a link to my EPQ!) if the water sinks to the deep ocean, the carbon can be stored for more than 1000 years before the general ocean circulation (via the upwelling of the THC after it has completed its circulation of the globe) returns it to the surface. This is one of the reasons that the current circulation pattern is so important as regions in which the sinking of deep water occurs are also, therefore, major physical carbon dioxide removal areas - especially the North Atlantic.

After a tour of the building (which is massive and very modern!) I attended a seminar on "The sensitivity of the energy and water cycles to different forcing agents" by Nathalie Schaller from the Institute for Atmospheric and Climate Science, ETH Zurich, Switzerland. I will try and talk about some of the background of this seminar as the majority of it discussed various models - something that went way over my head! It is now commonly accepted that, as a result of anthropogenic influences, primarily greenhouse gas emissions, that the hyrdological cycle, on a whole, will be intensified which, in turn, will have major impacts on human soieties and ecosystems. Therefore it is vital that more reliable statements about future changes to precipitation patterns can be found and this is where various global climate models come in. The variabilty produced by various models leads to some uncertainities which are then only amplified by the added complications of forcing agents such as solar forcing and carbon dioxide. So, basically, this seminar consisted of the results of running various simulations with different forcing factors, at varying levels and over varying temporal and spatial scales, to see what the likely impacts are. I think that one of the main messages was that the relationship between the energy and hydrological cycles with the forcing factors, especially CO2, was not linear and so say increasing the forcing agent by x2 wouldnt just lead to twice the impact on the hyrdological cycle and in many cases it is more. Despite the content being far to advanced for me to even start to really get an substantial understanding of it, it was really interesting to see some of the worrk happening in various research departments around the world and, if I manage to do a bit of reading over the next few days, I may write a post on the alterations that the discussed factors could make to the movement pattern of the ITCZ and the global impacts of this as this was something briefly touched upon.

Then, to finish off a great day, I had a discussion with a researcher about ocean circulation. Lots was covered, which I won't go into too much now but I am hoping to be allowed to include some of it in my EPQ. Something I think I will briefly discuss is the idea of vorticity as it is important in explaining the differing characteristics of eastern and western boundary currents and the formations of gyres - I might elaborate on it at a later date (perhaps including some maths!). Energy and mass are not the only properties that must be conserved as momentum also has to be - both in terms of linear momentum (associated with motion in straight lines) and angular momentum ( associated with rotatory motion). Vorticity essentailly means the 'tendency to rotate' and it is referred to as 'tendency' rather than simply 'rotatory motion' as water can be aquiring both positive and negative vorticity at the same time. Therefore, instead of saying the conservation of angular momentum or tendency to rotate, it is referred to as the conservation of vorticity. Ocean water have rotating movements on all scales - from large basin wide subtropical and subpolar gyres to tiny eddies. For water to have vorticity, therefore the tendency to rotate, it doesn't have to been enclosed in a closed system as, as long as there is a current shear (a change in velocity at right angles to the direction of flow), rotatory motion will be possible. Mainly due to the fact that it apparently makes the maths easier, a tendency to rotate anti-clockiwise is referred to as positive and a tendency to rotate clockwise is referred to as negative. I mention a before about that fact that water could aquire both positive and negative vorticity and the first time I heard this I was a little confused but an example I was given helped me to understand it a little better. So, water could be aquiring positive vorticity as a result of current shear provoked by friction with an adjacent water body or coastal feature (say a spit), whilst also aquiring negative vorticity from a wind blowing clockwise. Therefore the actually motion will depend on the relative sizes of the two tendencies and so, in theory, no rotational motion could be the result as the tendencies could be equal. This rotatory motion is caused by wind stress and so is said to be relative vorticity but, as with anything linked to ocean cicrulation, the rotation of the Earth complicates things and so the vorticity possessed by a parcel of fluid on the rotating Earth actually has planetary vorticity - this is where the Coriolis force links in. When I have talked about Coriolis force before, I have explained it in terms of the poleward decrease in the eastward velocity of the surface of the Earth. However, although this is okay for the basics, there is something missing........... In addition to this linear eastward velocity, the surface of the earth also has an angular velocity which means that, in the Northern Hemisphere, it turns anticlockwise about a local vertical axis (southern hemipshere is opposite). This angular velocity os latitude dependent and so there would be a relative motion between the moving parcel regardless of the direction it was initially travelling in; with this relative motion increasing with increasing latitude (this applies to both winds and currents). This is where a lot of maths comes in but I will try and skip over most of it as I am struggling to get my head around all of it! Linear eastward velocity decreases with latitude whereas the angular velocity about a local vertical axis increases latitude. The bigger the angle between the Earth's axis of rotation and the local vertical axis, the smaller the angular velocity of the surface of the Earth about this local vertical axis and so, at the Equator, where a vertical axis is perpendicular to the axis of rotation, the angular velocity is zero. So, I guess what I am trying to say is that any parcel of fluid on the Earth shares the components of the Earth's angular rotation, appropriate to that latitude. I hope you kind of followed that - if you did it would be really good to know as then maybe I can include it in my EPQ! It is quite a tricky area and I am still trying to fully understand it and I haven't even got into much of the maths yet! I will come back to this idea soon though as when you combine it with a summary of Stommel's (he is this guy who has done loads of thereotical stuff on the basics of ocean circulation) calculations, it helps to explain the characteristics of different boundary currents - which is both relevant to my EPQ and I find it quite interesting!

Sorry for not going into much detail about these things but I still need to do a bit more further reading and perhaps some images to aid my explanation and my brain is rather tired and I need a good nights sleep! Honestly, I don't think I slept at all last night as I was like a little kid on Christmas Eve - but to be honest who can blame me as, being an aspiring Geographer, I really couldn't of asked for much more as a kind of early Christmas present really! Anyway, I will come back to these various topics at some poitn soon and write something that is more beneficial for you all to read...................

I have another extremely interesting day to look forward to tomorrow with another meeting, seminar and some more discussion groups and so, if I manage to contain my excitement, my blog post will hopefully make more sense and be a bit more logical!

Sorry that this is a bit late in arriving, I couldn't seem to get the post to publish over the last few days so its kind of all out of time but better late than never I suppose!

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