[speaker002:] Hello Chris We play games on it though. No Has anyone got a? [LAUGHTER] I don't think it's, I mean Good communication though. Mm. Try A two see if A two's on it. Yeah... absolutely nothing at all. what sort of resistance on that lot? Christina go to your lecture tomorrow Say again? ten o'clock drive down to North Shields with all speed. [LAUGHTER] What's this []? All speed Then you don't need to miss your lecture. Oh no, right. Shame, bad luck Chris. Can you drive over with either Christina or Edward? Yeah Where was that man that wanted
[speaker001:] [LAUGHTER]
[speaker002:] Is he willing to pay for them?
[speaker001:] [video comes on]
[speaker002:] [shouting] Oh yeah whooo! Hurray []! Oh well done Lily. [LAUGHTER] Oh I just wanted to ask you how to work the machine but it's done now. Oh right. Good. Oceans and climate, it's not currents it's oceans and climate. Who?... We're missing out currents.... I might have to steal some more paper later on Mm! but I'll give it you back. Can I switch the lights on? Yeah.... [video on oceanography and the changing face of the sea] The highly productive waters off once supported one of the most bountiful fisheries in the world but in nineteen eighty three the which produced the fish failed and the fishery crashed.... Deprived of the which they the marine iguanas of the Galapagos starved to death. Arid equatorial islands were transformed by rainfall but their sea bird populations disappeared. had returned The climatic perturbations known as alminio seemed to occur every two to ten years. The nineteen eighty two to three event was one of the most severe on record and its affects were felt around the world. Large parts of Africa, India and Australia were ravished by drought... while the west coast of the Americas was lashed by storms and torrential rain. The nineteen eighty two to three event was also the most comprehensibly observed so far. The changing patterns of sea surface temperature were recorded by satellite mounted sensors and they showed a region of unusually warm water travelling across the Pacific. But why did this happen?... At the time a number of instrumented buoys were moored along the equator and were sending back information about the wind and sea conditions. In addition, large numbers of drifter buoys were launched into the ocean off Peru... and for several months they were tracked via the Argos satellite as they drifted with the surface currents. You can see the paths of the drifter buoys looking like comet tails... thin arrows centred on the equator show wind direction... while the thicker arrows show current direction. Watch the buoy drifting westwards just north of the equator, as it approaches one of the moorings it suddenly changes direction with the current. Normally we'd expect these buoys to move west in the south equatorial current under the influence of the south easterly trade winds but during alminio winds become weak and westerly and buoys putting off the coast of Peru seemed to wander about aimlessly. Other buoys previously moving westwards now changed direction. So it seems that the weakening of the trade winds allowed more surface water normally piled up in the western Pacific to flow back eastwards across the ocean. But it's not as simple as that. Sea surface temperature affects processes in the atmosphere... ocean and atmosphere form one system.... Our work proceeds by trying to model this ocean atmosphere system and initially we made these models to develop an understanding but it turned out that the models worked pretty well to make predictions.... Now in order to make a prediction of what say what's going to happen this year I would have to know the state of the system of the ocean and the atmosphere on January first... and in order to do that in an ideal world I would have a tremendous amount of data about the ocean and about the atmosphere and be able to put it into this model... but this data, by and large, doesn't exist. What we do have are some relatively scanty observations of the surface movements over the tropical Pacific based on volunteer observers on merchant ships. We need the winds everywhere and we rely on people in Florida state to take these very sparse observations and turn them into a map which covers the whole surface of the tropical Pacific. We then take those kind of and use it in an ocean to create the state of the ocean. Now we have the ocean and the atmosphere and we can go and we go forward and, in a good year, if we're lucky, the way the model evolves with the ocean driving the atmosphere and the atmosphere driving the ocean, mimics what happens in the real world and so we can make a prediction. Predictions have value of course because these are things which affect climate and affect people's lives, but also making a prediction is a way of trying to verify whether the understanding that we think we have about how the system works can actually be translated into equations which are put on a computer, and then when you let this go it in fact s does indeed do what the real world does.... With increasing success at modelling changes in the tropical oceans, oceanographers are now aiming to predict global changes in the world ocean circulation experiment, W O C E for short. In this experiment we would be making measurements of the entire world ocean looking at essentially a snapshot view of the behaviour of the ocean during a five year period. Crucial to these observations are satellites, satellites have the ability to make measurements at least of the surface layer of the ocean on a nearly daily basis. Also the observations in all parts of the global ocean from ships, from moorings, from drifters on the surface of the ocean and floats in the interior of the ocean. This data set, coupled with extensive satellite observations, will give us for the first time a... essentially a snapshot view of the behaviour of the ocean. Understanding how the global ocean works is important if we're to forecast climatic change. Pollution of our planet may already be warming the atmosphere and there's rising concern about what will happen at the poles. The polar regions of the ocean play a very crucial role in the global climate system. It's in these areas that the ocean heat is lost or vented to the atmosphere as this heat vent was... carried into the ocean in the lower latitudes. In polar regions, as the heat is lost to the atmosphere the surface water naturally gets denser and it sinks and it spreads at some level in the ocean into the rest of the world ocean. Even under the equator if you go deep enough you'll enter water masses that were formed in the polar regions. This has an effect of cooling the deep waters of the world ocean and it also has an important climatic effect in removing excess C O two from the atmosphere. The north Atlantic in particular is important in removing excess er carbon dioxide from the atmosphere. Perhaps half of the carbon dioxide introduced to the atmosphere has been removed by the ocean, primarily occurring in the northern hemisphere in the production of north Atlantic deep water.... The southern hemisphere polar region may play a smaller role in carbon dioxide balance but it is primarily responsible for cooling the deep ocean. Until the advent of satellites in the nineteen seventies we knew very little about the sea ice cover around Antarctica other than the northern fringes. The satellites revealed a rather remarkable feature in the Antarctic sea ice in that there are persistent open water areas even in the middle of winter... when the area should be frozen over, the atmosphere is cold enough to freeze the ocean and yet, in these areas, the ice does not form. These are called poleniers There are two kinds of poleniers one occurs along the coastline of Antarctica and is essentially formed as the strong winds blowing off Antarctica just remove the ice exposing the ocean, and the ice forms in this now exposed ocean very rapidly and then it's removed by the wind. Within these coastal poleniers an enormous amount of sea ice could form and then is removed to the north dumping enormous amounts of salt into the shelf water making it very dense and setting up the stage for the deep sinking associated with Antarctic. The ocean er poleniers were also revealed by the satellite images and these were even more remarkable and perhaps more unexpected. In these areas the surface water is convected deep into the ocean and deep water then comes up to replace it. Now the, the elongated convection cells which carry the heat of the deep ocean into the surface layer and prevent the formation of ice. These are called sensible heat poleniers in that they're maintained by the sensible heat of the ocean. The most remarkable of the ocean or sensible heat occurred in the mid nineteen seventies, what's referred to as the Widdell polenier An area of about three hundred thousand square kilometres was ice free for each winter for three consecutive years. The amount of ocean heat that was lost to the atmosphere during the Widdell polenier events in the mid nineteen seventies was absolutely enormous. We have temperature measurements before the polenier event and we have temperature measurements of the ocean after. The ocean cooled by about one degree down to depths of three thousand metres, an enormous amount of heat was extracted from the ocean. However, although the polenier event is associated with cooling of the ocean, it may not have had a very large impact on the carbon dioxide balance. The speed of the overturning does not allow er an equilibrium to be reached between the ocean and the atmosphere C O two content, and this is probably true throughout the southern ocean. It appears that the main extraction of excess C O two of the atmosphere is accomplished in the northern hemisphere, associated with the north Atlantic deep water. And then the southern ocean's primary role in a global climate system is to very significantly cool the ocean. So how fast do the deep water masses carry heat and carbon dioxide through the oceans?... Fall out from nuclear explosions has provided useful for water masses especially as the radio active nucleons are effectively time coded. Another group of artificial substances which can be used to track water masses are the fluoro fluorocarbons, C F Cs or freons for short. Water collected from the deep ocean contains gases dissolved in it when it was last at the surface and the relative proportion of these gases depends on their solubilities and their concentrations in the atmosphere. Denise has used a ratio of two C F Cs, freon eleven and freon twelve, to work out where water several kilometres deep in the ocean was last at the surface. The concentrations of freon eleven and freon twelve dissolved in surface waters have both increased dramatically since nineteen fifty but not by the same amount... and so measuring their ratio in a sea water sample will tell us how old the water is. This equipment can measure freon concentrations down to just a few parts per trillion.... Bubbling inert gas through the sample removes the freons which are condensed in a cooled coil. When all the C F C gas has been collected the cooling flask around this coil is replaced with one containing boiling water. The volatile freons quickly evaporate and are analyzed by a gas chromatograph.... These twin peaks on the chromatograph are directly in proportion to the amount of freon eleven and freon twelve in the water sample. If we analyze lots of water samples taken at different depths at the same we can then plot a graph of concentration versus depth and get a profile that looks something like this. This profile is for samples that I just north of South Georgia in the south Atlantic in nineteen eighty six. The red line represents freon eleven and the green line freon twelve. There are high concentrations in the top fifteen inches, but when we get below the next layer, the concentrations become very much less and the ratio of the two concentrations doesn't change very much. As we go deeper, there is a slight variation at three thousand metres which we know corresponds to Antarctic intermediate water. As we go even deeper to five thousand metres the concentrations begin to right again and the ratio begins to change.... If we now look at the curve which shows the freon ratios in surface water and look for a ratio of two, and lining this up with the nought degree curve because we're working with Antarctic water which of course is very cold, we can see that a ratio of two corresponds to the year nineteen fifty nine. These samples were collected in nineteen eighty six so we can calculate that the water is seventeen years old. Now we know that Antarctic bottom water is formed here in the Webber Sea and the samples that I've been talking about were taken here in the South Georgia basin, so we can see that it has taken seventeen years for the water to travel from here to here.... It's not just water sinking into the deep ocean that carries information about conditions on the surface. The tiny alga cochilicus amenianarxia multiplies in the spring forming enormous milky blues.... On death their placed as aggregate and rain down onto the sea floor where they dissolve if the water is deep enough. But scientists at the university of Bristol have discovered that, even where sediments contain no skeletal remains, two rather special organic are being preserved... molecular fossils if you like. They're very similar except that one has an extra double bond.... How we stumbled on this was that when we grew some of these algae at Plymouth... with our colleagues there, we found that when we grew them at one temperature then these two molecules were present in a certain ratio but when we changed the water temperature then the er ratio changed. So we, we then wondered could this actually be a sort of thermometer for the water temperature? And we were absolutely amazed when, in going round the ocean floors, we found that indeed these molecules in the sediments showed a, a relationship to the surface temperatures above them at the present day. And what we've done now, and with colleagues from Germany, is to take cores off north west Africa, say about twenty metres down into the sediment, we sample them in the lab here and took the small amounts of sediment and examined them for these long chain compounds and we were extremely excited to see that as we went down this core, back through the last few hundred thousand years, we could see our signal on sea surface temperature oscillating about roughly in the same way that er has been found with other methods of getting at the past history of the climate. For example, where the last ice age was taking place in Europe, then you can see the signal of the lower temperatures in the oceans off north west Africa in the form of this sediment signal.... Well so much for the sea surface temperatures of the past, but we've been looking at our records of the compounds in the sediments even more carefully and what we've seen in there are molecular fingerprints which do not match those of the marine organisms. So where are they coming from? Well we've fortunately been able to track them down to the waxes which er occur on land so what we're seeing here is a, an input from the land carried on the dusts which are blown in the winds from the Sahara and other regions out into the Atlantic Ocean. So this indeed looks a very exciting new development for us. But anyway, the whole problem we face now is how to do more samples because we're only looking at intercourse in the cores of, say, a thousand or two thousand year spacing, we've got to get down to a few hundred year spacing to really see some of the changes in climate that we know have gone on. How are we gonna do this? Well the only way we can see is to turn to the, to the physicists and the computer experts and to remove the chemical steps from our analytical scheme and use the speed and precision of the newer types of maschotrometer We already use auto-samplers for gas chromatography but now we need to bypass chemical steps.... One device we are testing is an advanced maschotrometer system with three small maschotrometers coupled together in a series. This device should give us a single analysis in about five minutes rather than ninety as at present as we don't need to separate the mixtures, we can do the analysis directly.... Really detailed molecular records at a spacing of a hundred years or less will be necessary to predict the climate change in the future and we'll really need that information if we're going to live safely on this planet. Now geologists have a maxim that the present is the key to the past... but what we need to do is to use the past to predict the future.... In the tropical oceans reef building corals have been responding to climatic changes for hundreds of years. They act as living tape recorders of the past.... When we five and a half years of life of the coral from Isabella Island in the Galapagos... the remarkable thing about this coral record is that it represents nearly three hundred and eighty years of continuous coral growth. Now corals grow under the sea but we didn't collect this particular specimen there. This specimen came from a reef that was uplifted virtually overnight in nineteen fifty four during volcanic eruption. This photograph taken several years before the uplift shows the dark oceans to the left and the grey volcanic land to the right. The has a small beach. This photograph, taken several years after the uplift, shows the beach now one kilometre from the present day shore line. This uplift brought with it many large colonies of corals one of which, this massive colony of, we sampled and brought back to the lab. So what can we learn about the oceans from this coral slab? If we look at them carefully we see a faint band in it but we can't count the bands this way, we can see them much better with X- rays. We placed the coral slabs on film, illuminated with them with X-rays and when we develop the film you see band patterns like this. The alternating light and dark bands form as coral growth responds to seasonal changes in the water temperature and cloud cover. Each band here represents one year we can age the, the coral by counting its bands just as trees can be banded by counting.... We know very precisely the age at the top of the coral when it was uplifted and died and what we've done is counted these bands back through hundreds of years, back to the time when the coral first started growing... and that was in the year fifteen eighty three. Now in the bottom part of this coral, the bands are quite widely spaced and are very regular. Now corals are very sensitive to changes in water temperature and these regular bands tell us that the water temperatures didn't change very much. Now if we look forward through time we see regular bands like this occurring through the mid sixteen hundred to sixteen forty, on up into sixteen sixty... sixteen eighty... still broad regular bands, conditions very conducive to coral growth, and in the early seventeen hundreds... on up into the mid seventeen hundreds one can see a remarkable change in the character of the growth bands. If you look carefully at this level you'll see two dark bands and in between the growth. At this point the coral was extremely stressed, in fact large parts of this colony died at that time. This tells us water temperatures were changing and we believe this represents a major almenial event which occurred in the year seventeen forty seven. Well so far we've just been looking at the record of growth bands in this coral skeleton, but we can acquire a great deal of additional information by sampling the skeleton, and we sample the skeleton using a small drill and we can analyze the, the powders that we collect for the stabilized of oxygen. The oxygen isotonic ratios of the coral tell us the water temperature at the time the coral was growing. Now remember this coral is from the western side of Isabella Island and at this location water temperatures are primarily controlled by the of cold, deep water as the trade winds blow from east to west across the islands. If you look at the oxygen results and plot them against the year of coral growth we see cooler water temperatures and hence stronger trade winds during the little ice age prior to nineteen hundred. The coolest water temperatures occur near seventeen hundred and eighteen hundred A D which also correspond to periods of. The period between eighteen sixty and nineteen hundred is especially important. This was a time of very rapid warming at the end of a little ice age and if we can understand how the climate changed at this time, we're much better able to predict future climatic perturbations as the earth warms up due to the addition of greenhouse gases. A rise in sea surface temperature will lead to an increase in the frequency and severity of tropical hurricanes. Parts of the world now outside the hurricane belt may soon experience their destructive power. There will be more almenial events in the Pacific. Climatic perturbations in general will become more frequent and more severe. There will be more floods and more droughts.... All these inter-related events result from the powerful coupling between ocean and atmosphere which controls our climate. [video ends]...