Transcript for:
The Role of Oceans in Climate and Monsoons

I want to tell you today about the role of the oceans in climate and much of what we feel as far as climate goals has to do with the atmosphere the temperature of the atmosphere but it's important to realize that a very large part of the climate signal resides in the oceans so just to give you an example of what I mean if you think about the amount of heat that's contained in the oceans and atmosphere the oceans hold about a thousand times more heat than the atmosphere and that's simply because the mass of the oceans is so much greater than the atmosphere and the heat capacity of the oceans is is much larger similarly the oceans also hold much more carbon or dissolved carbon dioxide than the atmosphere so the oceans hold about 50 times as much dissolved carbon compared to the atmosphere so the carbon dioxide in the atmosphere is very much controlled or regulated by the dissolved carbon in the oceans and similarly if you think about water the oceans contain 96% of all the water on the planet just about 2% isn't fresh one or two percent is freshwater two percent is in fact ice caps so the oceans play a really important role for regulating the climate and what we feel in terms of the atmosphere but also the water in regulating water and the hydrological cycle in regulating the co2 in the atmosphere in regulating the oxygen in the atmosphere because of our half the primary production or the fixation of carbon through photosynthesis occurs in the oceans so we owe a lot to the oceans for our lives but not many of us realize that because we live on land and which restor beings but really the earth owes its climate largely to the oceans and that's something that we really really need to realize today so what I wanted to tell you about today is really a research project that that I'm very much involved in along with the whole group of people it's a very collaborative project and science these days is done in in groups of people so on my colleagues I owe them very much and also my students who play very keen our important role in this project and also the funding agency so I started by acknowledging everyone and the we refers to everyone in this project and this project has to do with trying to better understand a region of the oceans which is relatively poorly understood it's the Indian Ocean the northern Indian Ocean is the focus of our study and this part of the oceans is particularly important because it supports a very important climate system the monsoons so the monsoons are an enormous breeze its enormous land breeze in which our ocean land breeze in which the winds blow from the oceans onto the lands and some onto the land and summer and then they reverse the mean winds completely reversed there's a huge seasonal change in the winds and along with the winds the circulation of the oceans rivers but these winds carry a huge amount of moisture with them and bring rainfall to a large part of Asia to South Asia and it's interesting to note that about half the world's population lives in that part of Asia about 1.5 billion people depend on the monsoons for their systems and the monsoons bring water to you know India and Malaysia and Burma and Pakistan and Sri Lanka and Indonesia and there's also an Australian monsoons so understanding this part of the climate system is very important because so much of the world's population relies on it and as you might have guessed the oceans play a huge role in the monsoons because all the water that comes into the atmosphere is really coming from the oceans the oceans provide the heat and the moisture for driving this huge weather system or this huge climate system so our motivation here is to better understand the role of the oceans and the monsoons and the reason we started this project is because we realized that when you look at climate models today or models that predict the weather or the weather over the timescale of a season we found that climate models do a really poor job in this part of the world's oceans and this part of the world they do a poor job at the ocean and the atmosphere because the atmosphere is so coupled to the oceans through the monsoons so this part of the world really the errors in the model are largest so why are these errors the largest if you try to ask that then we realized that as in this part the atmosphere and ocean are very coupled as I said the atmosphere gets its moisture and heat from the oceans and then the prediction of the oceans in the models was not is not working out quite well the models created ocean that's a little bit too cold and the surface cold compared to observations and then that doesn't drive the right monsoon system so we started this project in collaboration with several countries it's a very international project and before you go into some region of the world's oceans it's really good to reach out to the countries in that region and we reached out in particular to India also to Sri Lanka and started this collaborative project with them which entails several countries around that region we this this project was funded by the Office of Naval Research and it really brings cutting-edge technology to try to understand this problem when we spoke to scientists in India they told us that prediction of the monsoons is a very major problem for them and one of the big concerns is the onset of the monsoon but also the variability during the monsoon season or the summer monsoon season so the rainfall comes between June and August or September but it's highly variable so you might have a period of very high rainfall for about ten days then you have a dry spell then you have another intense period these are called active and break cycles and they see a strong correlation between surface temperature of the oceans and these active and break cycles so we really want to try and understand better what's happening here how the oceans feel into the atmosphere now the way we go about this is that we had a plan we take all the data that's available as I said this part of the ocean is under sampled but through the world ocean observing programs that are in existence today there is data available there are floats which are in the ocean that are autonomously making measurements and we're going to go to the float lab to see some of these floats and there is satellite data available from these oceans and we find that this part of the oceans is very unique it's very unique because it's one of the freshest oceans in the world and so why is it so fresh it's fresh because it gets an immense amount of rainfall if you want to look at global rainfall from a satellite image this part of the world's oceans just stands out it's the region of the world that receives the highest amount of rainfall 3me as much as some places receive as much as 3 meters of rainfall per per year or all during the summer season so there's a lot of fresh water that's coming into the oceans and there's also an enormous amount of fresh water that comes from rivers and the surrounding region so the rainfall that falls on the land and you have the Himalayas the mountains which are blocking off the winds there's you know the water is just flowing down the Himalayas and in enormous rivers the Ganges the Brahmaputra and the Irrawaddy they all flow into the Bay of Bengal and this fresh water creates a surface layer which is relatively fresh compared to the rest of the ocean so the oceans in general are very layered there's light water at the surface and denser water below the density varies by a small amount but it creates this layering which makes it very difficult to mix the oceans and in most places ocean density is governed by temperature so you have warm water at the top the surface is heated by the Sun and this layering prevents the oceans from mixing very strongly when you do have winds or mechanisms that mix the ocean you create a surface layer of the ocean which is called the mixed layer which gets mixed by the winds and cooling now in the Bay of Bengal which is the region of the oceans that we are studying here we find that the fresh water creates a light layer on the surface and the density of that water is governed by the salinity or the freshness of the water rather than the temperature and so why does this matter it matters because the vertical structure that vertical layering of the ocean affects how heat gets distributed so let me give you a thought experiment let me say that I have a region of the ocean in which this surface layer is well mixed to 100 meters and then I have another region of the ocean in which I have a fresh layer which is 10 meters or 20 meters of the surface and now I start heating both these oceans with the Sun in one case you'll find that the heat mix is deeper because the mixed layer is deeper and the winds are churning up that heat and distributing it over the upper 100 meters in another region where you have this fresh water layer the mixing is not penetrating as deep and so when you start heating the surface the heat gets more trapped in that surface layer and so you'll find that the surface temperature in these two regions of the ocean will actually differ even though the solar insolation is the same and this is in fact something that we know happens in the way of being cold so during the summer when the Sun is out and it's really warm in that part of the world the surface oceans heat up but the Bay of Bengal the temperature goes up very rapidly that increase in temperature drives evaporation and that latent heat then goes into the atmosphere and drives the circulation or affects the winds which form the monsoon so our goal here was to try and understand how this fresh water layering effects that the NCD structure in the upper ocean and how that affects the heat flux and the heat flux from the atmosphere of the ocean but also from the ocean to the atmosphere that both the heat and the moisture fluxes so this is what a you know I'll show you what a salinity and density section temperature sex section looks like so this by section I mean we are going along in a ship and we're making measurements in the vertical and we have a whole transect that we are making wither ship and that transect allows you to see what the temperature and density salinity of that ocean is now looking at that gives us some understanding of what the structure is but we really want to try and understand what processes drive that structure and an important role here is of people who think about theories and models and put those models together and trying to explain those structures so I'll give you an example of a model and my student watcher is working with this model now that's it's a model which describes the circulation and the flow field in the ocean as a function of heating/cooling winds and the initial temperature and salinity structure that you put into this model and so we created this model just as I explained to you a layer of light water as we see in the Bay of Bengal and with layer of slightly denser water which is less higher salinity and less fresh and then we start cooling this in this case this model from the surface and this cooling of the model of surface essentially takes out heat from the ocean surface so this is what you'd find in winter and you see that that heat loss is distributed over a greater depth in the region where the surface ocean is mixed to greater depth that heat loss is confined to lesser depth when you have a very fresh layer lying on top and so you start with a uniform temperature on top and now I apply the same cooling to both parts of the model and what we find is that one part of the surface ocean gets cooler than the other part of the surface ocean and I'll show you clip from this model which will allow you to see in fact how the surface ocean is now finding the heat fluxes responding because of this difference layering in this in this density which comes from the freshwater at the surface so models such as these there are many kinds of models you also we also have models of the entire circulation of the Bay and other people are working on these models but models such as this allows allow us to understand the processes that are play the processes that create that density structure and the density structure that have affects the air sea fluxes so let me go on to tell you a little bit more about the measurements that we make in the Bay how do we understand what the values of these off the air sea fluxes are so one of the things I'm going to show you a little bit later today is these buoys that we put out in the ocean so my colleagues your words hold Robert Weller and Tom Farrar are constructing or making ocean moorings and these ocean moorings are put out in the center of you in the middle of the ocean at various depths they have a string of instruments temperature and salinity measurements which are made at different depths and at the surface these boys have instruments which measure the atmosphere and they can also measure the transfer of heat and moisture between the oceans in the atmosphere so India has a number of these buoys in the Bay of Bengal and their ocean Technology Center National Abortion technology puts these buoys out Woods Hole has put out highly a very highly instrumented mooring just last November we'll see how that mooring is constructed in a little while and we'll be getting those measurements back later this year the morning is out for a year and we'll put in another moorings and we'll try to keep cycling these moorings so that we get continuous observations because getting observations over a period of time is very important in the oceans because the oceans are not just static they are evolving in space and time so different parts of the oceans we measure different things but it's evolving all the time in time since the same location things keep changing and this is why it's a difficult problem of having to measure both space and time and if you really want to understand how things are changing over some period of time particularly how warming global warming is affecting the oceans we need sustained observations and sustained observations over the period of several years actually costs a lot of money I mean having one of these single mooring like this can drum in two million dollars so you can imagine how much it costs to maintain a mooring for a year so besides the morning I'll tell you show you some other instruments today and and those instruments are gliders and floats will go to the float lab the gliders are autonomous instruments we are trying to automate a lot of our instruments at the same time we do have the need to go out on research vessel vessels or ships so we'll see a research vessel we've made three cruises already in the Bay of Bengal and this August will do yet another cruise on a research vessel called the Roger Revelle and it's Scripps institutions research vessel we see one of one's whole research vessels later today and this these research vessels are specially outfitted with all kinds of gear they carry a lot of instruments the back of the research vessel has a special special crane I should say which from which you can lower instruments into the water and as the ship is going along in the water we the research crew works 24 hours a day in shifts shifts because these cruises are very expensive day of a research cruise costs just for the ship cost something of the order of forty or fifty thousand dollars so you want to really maximize the measurements you get back from one of these research cruises you work throughout the day and shift shifts you want to make sure the data is good you want to make sure you get data all kinds of things can happen with this with the instruments in this particular study our cruises are involving also scientists from India and Sri Lanka and a large part of this effort is the collaboration the international collaboration because no one country can just and measure the oceans the oceans are vast and we really need a real an international effort in studying the oceans so it's our mission to try and involve these other countries and also to bring these cutting-edge observations that we are pioneering through the funding of our national agencies to these other countries promoting the use of some of the the equipment and learning also from their empirical knowledge about their oceans in this particular collaborative effort we are respecting what's called the economic exclusive zone of the countries so every country has an economic exclusive zone it can get quite political so working with the host countries where in the region where you're working has a lot of advantages and it the work of course also benefits them which which is very important so I'll just tell you a little bit about life on this research vessel this particular cruise that we are going on is very international we have people from all countries as I mentioned India and Sri Lanka and even scientists in general are our scientists at Woods Hole are very international the scientists get together in a lab in the ship they plan out before that we go on the mission we plan out in great detail what we are going to do what instruments we're going to take how we're going to make the measurements what the cruise track is what the cruise plan is how many people are coming which scientists are going to do what who's going to be on watch shift there are several PI's and we are all coming together to make these observations at the end of the observations we all go away work on the data but we gather very often to talk and a lot is learnt through these meetings and discussion we sit around the table we talk in small groups we get together in larger meetings where people fly from across the country or meet in one place or meet through you know the internet we show our data to each other and different people are learning different things and really the sum ends up being more than individual parts so the collaborative aspects are really really important for this kind of study because however much we try to sample the ocean we are under sampling it it's just evolving all the time and we're getting measurements some region we're trying to extrapolate with theory and models to other parts of the ocean to understand how it works now when we're at the in the ship so once we go to this other country where we're going to make the measurements there's some formality with all the equipment has to be shipped ahead of time we've already sent a container ahead from Scripps so all the different institutions right now the study there's seven or eight universities within the US and other seven or eight institutions in India we pulled all our equipment together we sent it to scripts container has shipped from Scripps and it will board the research vessel the research vessels are all the time involved in research programs in different parts of the world they don't come back home every time our research vessel is now in the Pacific the Roger Revelle it's going to meet us in India in a port called Chennai and the port of Chennai and the scientists will board the research vessel there we'll be out for four weeks starting mid-august and have a plan of action we're bringing several instruments making something called underway CTD that means while the ship is moving we have something called a fast CTD which measures conductivity temperature and depth through pressure and so conductivity gives us salinity temperature with the thermistor a special probe for temperature and then we also have acoustic measurements what's called a DCP at the bottom of the ship which measures the velocity or the speed of currents and then we deploy a lot of autonomous instruments which we throw leave in the ocean we deploy them in the ocean and these instruments will be making measurements some of them will be left there for six months at a time for a year at a time we go back and collect them at the next cruise or our Indian partners will go out and collect some of the instruments and some of the instruments we deploy while we're on the cruise and then bring them back with us there's a crane there are several cranes on the ship the instruments are lured from the crane there's something called a CTD rosette which has bottles on it these bottles are cocked open and at different depths that's the whole crane lures is resident to the ocean to depths of thousand meters or 1500 meters or whatever depth you wish and it's brought back up by the crane and the bottles pop shot automatically when you trigger them at the depth where you want to take more the samples so it's important also to measure the chemistry and the biology and the water it's a very interdisciplinary problem I've spoken mostly about the physics but the chemistry and biology of this region is also unique for example in May of Bengal is an oxygen minimum zone where oxygen is very depleted and we're trying to understand how that happens and then there are various labs in the ship so there's a computer lab where all these different streams of data are coming in we see them on the monitor in real-time and people have to make decisions so we have to make sure the data is good that all the instruments are working at all times but at the same time we also have to make decisions as to where we're going to go should we change our observational plan shall we make follow a feature shall we go to region which we're seeing lots of differences in density or where the velocity is higher or sometimes we have to change our plans because of a storm so the last time we were out there there was a hurricane that came and it significantly changed our plans as to what we should be doing next so we have simultaneously making measurements of temperature salinity velocity we measure the turbulence or the mixing the rate at which things are mixing people are analyzing the chemistry of the water people are making biological measurements of oxygen fluorescence will be taking water samples to look at what kinds of phytoplankton communities live there and we also measure the atmospheric variables the the wind the incoming solar radiation the heat fluxes from which we can calculate the heat fluxes and momentum fluxes and this is you know the back of the ship we have instruments that go out and making measurements these instruments some of times can be told behind the ship for example we can drop a probe which measures temperature and slowly pull it back and keep dropping it so that as the ship is moving along every three or four kilometers we're getting a measurement in the vertical of temperature salinity to look at that layering of salinity and temperature and the shifts work 24/7 throughout the cruise once we get underway we get our equipment going we we work 24 hours a day in shifts to make sure that everything is going as planned at the end of the day people get together for a meal and we sit around typically and talk about what we have seen that day or talk about each other science that we get inputs from everyone and try to you know really further us learning as a crew as I said that's an important part of this research and we also do it on the ship when we are at sea but what I'm working on in this study is trying to understand the dynamics of the upper ocean the dynamics and response to input of solar energy and in response to this fresh water that's coming out of the bay the fresh water that comes out of the bay not only creates a layering in the vertical but you have horizontal differences now in salinity and also horizontal differences in density and these horizontal differences in density lead to a very dynamic field of ocean currents and Eddie's so the ocean is very dynamic at all scales you have currents and Eddie's at large scales but you have swirling motions and Eddie's that are occurring on scales of thousand kilometres 100 kilometers 10 kilometers one kilometer and down to the smallest scale of meters and I am thinking of how these Eddie's or these swirling motions help to stir this fresh water round mix it and and transport the fresh water that's coming all in the northern part of the bay out into the southern part of the bay at the same time effecting this density structure so that it has an effect on the air see fluxes of heat and moisture and that feeds back into affecting the monsoons so our long-term growth through understanding these processes this once we understand these processes better we can incorporate them into models that cannot resolve these very small scales by small I mean kilometer skills that we are able to look at with these special models and these special tools of observing the climate models are have grids or spacings of about you know third of the green latitude longitude that's about 30 kilometers so they don't capture all these smaller scale processes but we are able to understand them now much better and are starting to understand them through these observations and modeling and our next step would be to try and take this understanding put it back in the climate models and improve their ability to forecast predict the oceans temperature and the monsoon this area we call our high bay and it's a place where we prepare instruments and boxes for cruises a packing list will be made and everything will be loaded into shipping containers with forklifts to be shipped off to the cruise destination so these are the buoys that that we use and there's a big square hole in the top of this buoy it's a two point 8 meter buoy so about 10 feet across and inside that big square hole we'll put one of these we call them buoy Wells so it's these big steel boxes will be filled filled with batteries essentially in computers and then on the buoy top we'll have instruments and over here you can see an instrumented buoy that we're testing so we call this burn in and we we run these instruments for about a month to test that they're working before they go into the field and so our group measures surface meteorology from these buoys and the goal of that is to understand the exchange of heat and moisture between the ocean and atmosphere and the exchange momentum from the winds pushing the ocean and so we're measuring solar radiation infrared radiation that comes down from the atmosphere sea temperature and currents we're measuring the winds humidity air temperature and from these things we can combine these measurements to estimate the exchange of heat and momentum and the evaporation from the sea surface we're measuring the rainfall with rain gauges and the buoy will stay out in place for about a year so Tom just showed you one of our surface moorings this here is one of the pieces of instrumentation that we have clamped along the mooring line and this measures subsurface currents this is a vector measuring current meter and you can see that it's got two axes here that measures currents flowing in two different directions in addition we also measure temperature and conductivity up and down the mooring line and we use these these are a seabird 37 you can see we have a whole rack of them right here and this is probably one of the most measured parameters in our mooring is the temperature and conductivity with temperature and conductivity were able to determine the salinity of the water bodies and that is one of the most important measurements that we make these are autonomous underwater gliders one one variety of them anyways so what they are are platforms for us to attach a lot a bunch of instruments to and what they do as a platform is go up and down through the water so they're able to change their buoyancy they do that by moving water or air in and out of the pressure case or in and out of the hull and then changing their volume that changes cause them to rise or fall in the water column and as they do that they're able to pitch their nose down as they're descending and up is there a sending and that lets them go through the water in a zigzag path like this so every time they come to the surface they're able to communicate in these gliders their antennas for GPS and satellite communications in the tail so they come up to the surface and they stick the tail up in the air and then they can send back data they can get new commands from us and they do that once every few hours typically depending on how deep they're diving as far as the types of measurements they make all of these gliders measure temperature and salinity profiles they're also able to make estimates of currents they measure optical properties such as chlorophyll fluorescence some of them one down there further down has a current profiler so it can not only measure the the average currents but the actual profiles of currents in terms of endurance these vehicles are typically able to be deployed for weeks to months at a time depending on the type of batteries we put in them so in that time they can cover hundreds to thousands of kilometres through the water they don't go very quickly they only go about half a knot so about walking speed or even less than walking speed but because they can stay out so long they can cover a long distance so overall these the gliders are a great tool for giving us long-duration high resolution measurements out in the ocean when we so that we don't have to be there to collect them they send back the data in real time so we have the data of coming back to us all the time when we're able to put a fleet of these out like we're planning to do in the Arabian Sea we can collect lots of data from lots of places we can plan together in different kinds of patterns and collect pretty unique data sets so this is a agro profiling float it's an instrument that measures temperature and salinity in the water currently there are over 3000 of leaves in the world's ocean as part of the Argo program which is an international program to seed the world's ocean with many of these to try to provide global coverage of measurements of the upper ocean temperature and salinity the float itself consists of a sensor at the top which is the part that actually measures the water properties and then the rest of it is a hydraulic system that makes the float go up and down in the water column these floats are capable of profiling the top 2 kilometers of the ocean which is roughly about half of the ocean they go out we can program them with different missions most of ours profile once every 10 days and that's chosen as a time period that meshes well with ocean variability and maximizes how long the floats last in the water our floats typically last from 4 to 5 years and we've had some last 7 to 8 years so they're very long-term missions when we put them out the technology is very much like the glider technology except it's simpler we've taken the wings off and instead of gliding around we just go up and down horizontally we drift wherever the currents take the float but by making things simpler we've reduced the cost and that's why we can get so many in the water the ocean has always been poorly sampled or under sampled and by having an instrument that we can deploy in large numbers we get many of them into the oceans most of the time the float is down at a thousand meters depth in the ocean and there's not much going on there these floats only spend about 15 minutes at the surface they need that time to get a GPS fix so they know where they are and then there's antenna here which transmits the data back to us via satellite network now it all takes place in about 10 to 15 minutes depending on how much data there is and then the float sinks back down so they Sui try to minimize the time at the surface both for avoiding obstacles and also before avoiding fouling of the sensor there's lots of biology at the surface when we're deep there's less concerns about bio fouling of the the sensors themselves so one of the strengths of the Argo program is that it's an international program and all the data that we collect is publicly available in near-real-time usually within 24 hours of the profile actually being reported by an instrument the data is placed at a public website and anybody has access to that data and can use it either for their scientific research or for weather forecasting my name is Chad Smith I'm the assistant marine Operations Coordinator here Woods Hole Oceanographic and what I do is essentially manage the research expeditions on one of our two ships the research vessel north where we are today our missions can range anywhere from the full gambit of oceanography geology physical oceanography climate research we have a very diverse needs of the scientific community that we have to meet the f deck of the Noir is where a lot of our action takes place as you can see the deck has a bolt pattern which allows us to mate up any equipment winches of any variety and bring it to any ship in the u.s. research fleet and bolt right down to the deck that facilitates our mobilizations of operations most anything that goes is deployed from the north stern goes out from this a-frame that can be towed or vertically dropped we deploy a wide variety of equipment from Lenoir it can be as diverse as a vertical cast CTD rosette - an aerial drone that has to be launched and recovered on our decks all of these things can happen in the course of a month because of noise versatility is a general oceanographic vessel she's not specialized to set into any one type of mission therefore she fulfilled a very crucial role catching a lot of different operations that need to go from US ships here we are in the bridge of the research vessel nor the being research vessel Knorr bridge equipment isn't appreciably different from other vessels in the u.s. merchant fleet we have radars that are for navigation and collision avoidance paper chart plotting as well as computerized chart waters we also have what's called dynamic positioning if you see here behind me you'll note an absence of a large ship's wheel we have several smaller controls on our helm which control the control surfaces that make up our dynamic positioning system what dynamic positioning is is it essentially allows the ship to stay in one geographic position as we conduct research it also allows the ship to be extremely maneuverable which makes docking which normally requires complex maneuvers I greatly simplifies the process other things that are controlled from this bridge all communications that come in the command of the vessel went under way and when conducting operations and you'll also notice a few things that look a little bit out of place such as this Navy style intercom and the sound powered phone this is essentially a highly engineered version of two cups in the string and it's the way we communicate on the vessel when power is down nor is actually owned built and owned by the US Navy and she's been operated by Woods Hole Oceanographic Institution since the late 60s I'm from a group in Cape Town South Africa and I'm working with and a mother primarily in the southern ocean so I'm visiting here for a couple of months of doing my PhD and the group that I'm working with in Cape Town we work primarily in the southern ocean which is a far way away from the Bay of Bengal but still equally as potent as important and we use these glider platforms as well because the southern ocean is a very rough and dangerous place to be over long periods of time so we put these guys out these are surface gliders so these guys remain at the surface of the ocean and then the diving gliders have been explained and how we do our sampling is that the surface gliders remain at the surface and the diving gliders dive just below them and in that way we were able to combine measurements of the atmosphere and the ocean to form a symbiotic understand the symbiotic relationship between the two I'm a graduate student working on my PhD and this summer we're going to the Bay of Bengal in the Indian Ocean on a ship very similar to this on the RV revell will be collecting various data for a whole month using CTD casts and gliders and floats and with all these platforms we'll try to measure the currents of the ocean the cylinder needs temperature the atmospheric conditions and we're hoping to use that data and combine it with modeling data to better understand the upper ocean structure and its its interactions with the atmospheric monsoon system and I hope to get my an interesting PhD thesis out of this you