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welcome to the introduction to oceanography chapter six water and ocean structure so two different components will talk about water in the structure of water and how its form the way it is and what that means about the water molecule why it makes it so special and its unique properties then we'll get into motion structure salinity and temperature and how the different aspects of salinity and temperature govern how the ocean
0:22
access it moves to its basins let's go ahead and get into Chapter six water and ocean structure so a quick look at the main concepts from Chapter six heat and temperature are not the same thing temperature is an object response to an input or a removal of heat and not all substances respond in the same way we also talked about the fact that water resist rising and temperature is heat is added it means it's slow it's slowly heats up and it slowly cools off it also
0:51
gives off heat when it freezes and absorbs heat when it thaws thats latent heat that's going to be very interesting aspect of water these properties of liquid water helped to moderate the earth's temperature in so we're also gonna look at how the water molecules structure to make it a very very powerful solvent or also talked about how the ocean is density stratified dense cold and salty water underneath less dense warm and fresh water we're
1:16
going to take a look at light and how it moves through water and how sound and light move in different ways through water and then we talked about how the ocean is a vast reservoir that affects the Earth's climate can be a vast carbon reservoir so you very likely have seen this view of the hydrologic cycle many many times water circulating constantly between the oceans the atmosphere and the reservoirs of fresh water and the whole numbers represent thousands of
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cubic kilometres of water transport each year and the percentages show the proportion of total global water in different parts of the cycle alright let's talk about solutions and mixtures so what our solutions and mixtures a solution is like taking a fresh distilled water absolutely pure water and putting a tablespoon of salt in a mixing it up the salt dissolves into the water it becomes part of the solution then you have salt water so a solution
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is made up of two components with uniform molecular properties throughout such as water or sweet tea the solvent which is usually a liquid is more abundant and the solutes often a solitary gas in the case of salt water salt or in cases of TV channel gas in there often a solid or gas and they are the less abundant component now solutions are different from mixtures alright a mixture in a mixture the components retain their separate identities so it's not uniform
2:38
think of soup like like vegetable soup it's a mixture of different things all retain their identity their separate identities a compound is a substance that contains two or more different elements and a very fixed proportion like h2o we have two hydrogen atoms one oxygen atom very specific proportions to different elements making up a compound and element then as a substance composed of identical particles are all the same atoms of oxygen is all oxygen atoms and
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those atoms cannot be chemically broken down into smaller substances molecule is a group of atoms held together by chemical bonds other ionic or covalent and atoms are the particles that make up elements so a water molecule is composed of two hydrogen atoms in one oxygen atom held together by a covalent bond it makes it a polar molecule having a positive and a negative side a molecule is a group of atoms held together by chemical bonds so those chemical bonds
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the energy relationships between Adams and hold them together are formed when electrons a tiny negatively charged particles found toward the outside of an atom are shared between atoms or removed from one to the other now in the electrons are shared as they are in the water molecule it's a very strong covalent bond when the Adams move from one to another it's a question of opposites attracting and negative and positive atoms attract
4:12
making an ionic bond in ionic bond is not nearly as strong so in the case of your hydrogen atom know which is right here this is hydrogen Adam we have the nucleus in one electron now electrons move around nucleus is the nuclei and shells in the first shell can contain two electrons in hydrogen release contains 12 second shell as we see here with the oxygen atom can contain up to six electrons and each subsequent cell can contain eight
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electrons in each subsequent gel can contain eight electrons when two hydrogen atoms come toward one oxygen atom they share this electron this electron gets into this show that election gets into that shell and then when you have is the one proton at each hydrogen atom the one proton of the oxygen the two inner electrons in the two inner shell of the oxygen and then 12345678 electrons in that second shell the oxygen atom and the hydrogen atom
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are sharing this electron they're sharing that electron and because of the positive nature of hydrogen the negative nature of oxygen that opposites attract and you get this very specific 105 degrees symmetry between hydrogen atoms creating this molecule that is a polar molecule meaning negative on one side and positive on the other side and looks a lot like Mickey Mouse alright what holds water molecules to each other hydrogen bonds form when the positive end of one water molecule bonds the
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negative and have another water molecules so the positive hydrogen and connects and bonds to the is attracted to make an ionic bond with the negative end of the oxygen so that is the hydrogen bond is a very very strong bond so what are the two most important properties of a water molecule well its cohesion and adhesion and it's because of this hydrogen bond the hydrogen bond allows cohesion the ability of water molecules to stick to each other that
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creates surface tension take a drop of water put it on the table it doesn't spread out to one thin layer of 11 molecule sick water on the table it stays in a little you know little drop the surface tension holding out water together the same as if you have a drop of water hanging on the tip your fingers you got hanging upside down that water molecule hangs there because of surface tension will adhesion is the other important property of water is the tendency of water molecules to stick to other
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substances and because of those adhesives properties in the polar nature of the molecule it makes it an excellent solve it so what is the difference between heat and temperature we talked about that at the very beginning of the of the election he is energy produced by the random vibrations of atoms or molecules all atoms or molecules moved even in a solid they may be rotating or vibrating in a gas they're sitting around in the air and the atmosphere or
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whatever containing the gas inlet with a move by each other squishy and all equity alright so all molecules and atoms moved in maybe zipping around they may be vibrating the may be rotating the hotter the molecule the atom is the more they vibrate and move and the colder the molecule the less they vibrate and the temperature is an object's response to the input or removal of heat meaning when you input heat into a substance those molecules begin to move more
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quickly and that change in movement is the temperatures of the temperature is a measure of the average speed of molecules now heat is all of the motion of the molecules in a substance and temperature is the measure of the average speed of those molecules heat capacity is a measure of the heat required to raise the temperature of one gram of a substance by one degree Celsius natty capacity comes in the form of a calorie it takes one calorie a heat
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to raise one gram of pure water by one degree Celsius me see that on the Chartered heat capacities a common substances pure liquid water requires one calorie program water has a very high heat capacity takes a great deal of heat input to change the temperature of water it also requires a great deal of heat removal to lower the temperature of water so the relationship here between density in the temperature of pure water so over
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here at a rate but nineteen twenty degrees twenty degrees Celsius here we're at 10 beware at 3.98 every specific temperature Celsius that is a maximum density of water one g/cm cubic centimeter that is one little cuba of of water when the cinema to white cube of water and then the density of water drops rapidly as it chills in the drop significantly as ago some liquid water here at C two solid water addy so here you have very warm water with a very low density and as it gets colder
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and colder and colder the density increases that makes sense right density is the volume the amount of a substance divided by its volume so the density of a square of styrofoam is significantly less than the same size square of LED there's way more molecule stuffed in that same size square of leaded has a higher density mass divided by volume and as the mass increases in the same volume when you get higher and higher density as the mass decreases in the
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same body me get lower and lower density so what do all substances do when they get cold they contracted the contraction of water causes it to become more dense right 3.98 degrees Celsius there's a maximum density of water pure water one g/cm then as it continues to chill toward freezing the molecules of water begin to arrange themself more in a lattice formation the hexagon that we think of as a snowflake and they take up more room inside the volume increases
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and the density goes down this is still liquid water appoint 999999 g/cm once it freezes the density of water goes down 2.9 17 so you can see that density of frozen water significantly less than a density of warm water or even cold water and that's why ice floats when the water freezes is the density of that same amount of water is much less and the ice floats so the lattice structure of a nice CRISIL showing the hexagonal arrangement that's
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the hexagon of the six sides of the snowflake that's your hexagon during the transition from liquid to the solid-state the bond angle between oxygen and hydrogen atoms in the water wines from 105 109 degrees because the change in temperature this change allows the hydrogen bonds in ice to form a crystal 3d lattice that's how you get that hexagon in a 3d lattice now at this point these are all individual water molecules the space taken up by 24 wall
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of water molecules in solid lattice could be occupied by 27 or significantly denser amount of water molecules in a liquid state so solid water is less dense its 9 percent less dense and because of that again I saw Liz floats alright so let's talk about those states of matter I referred to the phase at one point phase or a state of matter there are three states of matter you have a gas or liquid and solid now some say that plasma is a fourth state of matter
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and that's very true but in this case of physical signs were gonna these three states of matter gas leak would in a solid so a gas is a substance that can expand to fill any empty container atoms or molecules of a gasser high-speed motion is a move in random directions they moved just about any different way a liquid is a substance that flows freely in response to unbalanced forces if you got a glass of water it sitting here probably still if you tip the water
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over it now you have an unbalanced force in that water will flow freely because of that unbalanced force but it does have a free upper surface in the container of it doesn't feel that container so gas bills in a container that you put if you have two hydrogen water molecules water vapor in a container that he'll still up and Tara container water will not fill the entire container it will have its own upper boundary and that's one big difference in saving gas and liquid all rights
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atoms or molecules in a liquid move freely pass one another as individuals or small groups liquids compressed only slightly under pressure gases and liquids are both classified as fluids because they both flow easily a solid is a substance resist changes shape of Iowa solid can typically withstand stresses like you can press on the table and it won't just move a bed and a solid usually brake suddenly on earth water can occur in all three states which
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makes it very very unique in here is the change in state going from a a solid piece of ice at 40 degrees below celsius to i sad 0 degrees Celsius to ice transitioning from ice to water and then heating up from zero degrees Celsius to 100 degrees Celsius the boiling point of water and then vaporizing into the air and what we see here these flat areas this is where we have additional heat is input case that we've won this very very cold ice from 42 below 20 degrees
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Celsius and we wanted a little bit of shit in it and do it this is the heat of the bottom calories now we get to this frozen ice it takes a tremendous amount of heat with no change in temperature to melt it then we add heat again just a little bit of the time water warms up it warms up to 100 degrees Celsius but then it takes a tremendous amount of heat input to get that water to turn into gas and the reason why that is is because in order to get this ice to turn into a liquid you've got a break
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down the the bonds the bond between the molecules they're very very well-structured very very tight very well mound and a solid see a tremendous amount of energy into that sought to break those those bonds and turn it into a liquid now have a liquid up to 100 degrees Celsius and get that liquid to turn to a gas again you have to put a tremendous amount of heat energy into that liquid to break the bonds the liquid the water molecules are legally
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bound together but tremendous amount of heat input and those water molecules a break apart become a water vapor and so lots and lots of of energy is required to turn liquid water and developer interestingly enough when water vapor then condenses goes from vapor to a liquid its gonna release all that energy and then win water those from a liquid to a solid it's also going to release energy significantly less but it will release energy so what we learn
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from that is that it takes energy into go from a nice to a liquid by removing energy and the environment to causes that nice to go to a liquid you literally kill the environment the same thing happens when you go from a liquid to a gas when evaporation occurs it takes energy to go into the delinquent for to evaporate thereby chillin the environment but the opposite occurs when you go from a vapor to liquid condensation you release heat and
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therefore condensation is woman process and when you go from a liquid to a nice you also release heat in again a global scale that change right there that warming and when you turned to ice and cooling when you melt actually helps a moderate the world's a temperature keeps it from being too extreme one way or the other alright so the energy input or output associated with water in the three states of matter we have to add 80 calories if he to change a gram of ice
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to liquid to get a gram of ice to turn to a liquid we have to add 80 calories if he woulda said he'd come from it comes from the environment has to take it out of the environment so if you have ice in water and causing the ice to melt it literally chills the water ice in your tea rice and you're so do you so does warm UT's warm you put ice in it the melting of the ice requires 80 calories of sheet where does he get the heat from it gets it from the soda off the tee thereby killing
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the team another way to look at this is going to the beach with a case of warm soda or beer whatever it is you so did you cooler be destroyed in the cooler you've got away but if you put water and that ice and caused that I smelt it will chill those cans of soda or beer much more quickly because the heat energy required to break down the bonds of the ice will be pulled out of that warm soda or beer same thing happens you go from a liquid to a to a vapor and this is
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basically just evaporation liquid to vapor it takes 540 calories to break the bonds of the liquid to turn it into a vapor and so evaporation is cooling process is a really great example take water put any armed let it evaporate it'll feel cool when you sweat the point of sweating is not the liquids what to make you feel cooler but for the sweat to evaporate off your body and end in requiring 540 grams 540 calories per gram of water in your body and it pulls
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that that heat energy those calories out of the atmosphere around you cooling the air around you evaporation or evaporation of sweat is cooling process so condensation is heating process evaporation is grueling process conversation is heating process in evaporation is a growing process ice to water cools the environment around it I schools the water of the tea that it's sitting in water to a vapor evaporation cools the air around it it requires C to break those bonds in the opposite occurs
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when we go from the vapor to liquid we release heat we go from a liquid to a nice we also will release heat latent heat is a very interesting thing is the latent heat the latent heat of evaporation or the latent heat of condensation it's the heat that's required to break the bonds is hidden within the water molecule and when the water molecule goes to a liquid or to a nice it releases that heats its late need evaporation late heat of condensation Laden again meaning invisible
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says an interesting properties of water this is your book you can read through it its ability to dissolve waters known as the universal solvent its density surface tension its ability conduct heat it's a ticket as you can read about all that in the book lots more properties of water lately diffusion latent heat of vaporization that's led to freezing and melting la conchita vaporizing heated conversation and again there is a shin in conversation the highest heat
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required of all substances so the condensation of water vapor in the clouds releases tremendous amounts of heat in the atmosphere so think about water at the equator evaporating into the atmosphere of the Equator getting move north as water vapor and and being in condensing in the clouds over northern England it releases tremendous amounts of heat over northern England is this latent heat of vaporization condensations one of the
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ways we moved here in north and south from the equator alright and because of his unique properties of water water moderate temperatures meaning it takes a great deal of heat warming up takes a great deal of heat removal to cool it off and what that tells us is that if you're near very very large body of water in your temperatures are going to be much more moderate than they will be if you're far away so let's take this is an example between San Francisco and
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north but much better example just consider Seattle here in the North Dakota here Seattle may not get all that cold in the winter but it also may not get all that warm in the summer that's because it's very close to the Pacific Ocean where we know that North Dakota gets extremely cold in the winner and quite a bit warmer in the summer because it's far away from any of the moderating impacts of water so water moderate temperatures this summer static properties of water
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at those properties ACTA moderate its change in temperature heat capacity late fusion and air and ocean currents they all cause large bodies of water to moderate temperatures are moderate climate and we talked about how the melting or the freezing of ice i the releases heat or requires heat so it takes a great deal of heat to melt the ice and so when ice is melting around the Arctic in this summer time it takes heat out the
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environment actually cools environment keeps the environment from warming up too quickly and more ice melting in the opposite happens and it's very very cold in the winter time and ice begins the form that formation of ice releases heat again that serves to moderate temperatures on a global scale and we can see how currants do the same thing ocean currents and atmospheric currents move heat from the tropics of the polar latitudes ocean currents move warm
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tropical water North Lake the Gulf Stream here's the gulf stream it comes out of the Caribbean goes up in the Gulf of Mexico struggles around and he goes out of florida straits and up the eastern seaboard then moves Crosstour Western Europe at Gulfstream bringing that one water over western Europe is the reason why the UK will not warm is certainly more than at the same latitude over here in Canada so atmospheric circulations move even more heat higher
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latitudes by the mass movement of water vapor you evaporate all this water down by the equator and you move it north in condensation occurs it releases that he has condensation water vapor clouds occurred higher latitudes tremendous amounts of late need released the warning process of condensation water is also a powerful solvent to the polar nature of water it makes a great solving it will eventually dissolve literally anything you put anything water long enough to dissolve that we think is
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table salt and that's actually sodium chloride so you put sodium NaCl into water the positively charged hydrogen into the polar water molecules attracted to the negatively charged chlorine ion an alien charged oxygen is attached to the positive charge sodium and so it literally pulls the chlorine and sodium apart so water is a polar molecule and then polls other polar molecules apart while oil is not a polar molecule oil that does not have that poll in nature
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and that's why I watered can dissolve oil the tool sort of separate when water comes in contact with compounds whose elements are held together by the attraction of opposite electrical charges like most salt the polar water molecule separate that compounds elements one another water dissolves the compound the compounds elements can move easily through water by diffusion the random movement of materials through a solution which means that you take water very Stillwater and drop a tablespoon salt
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into the water the water of the glass diffusion will call that will cause a higher concentration of salt at the bottom of the glass to eventually randomly move throughout the entire glass of water eventually the entire blossom water become salty thats diffusion when no more of a compound will dissolve water is said to have reached saturation the rate at which molecules of the soldiers are being designed dissolves now equals the rate
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at which the reform in the crystal so essentially to put a whole bunch of salt into water and you start to stew stirred up the salt crystals will dissolve in dissolving dissolve the become a point when no more of that water can hold salt crystals and then anymore and dissolution or dissolving assaults were acquired that some salts recrystallized so it's sort of the recycling process for some of the crystals are dissolving and some of the crystals are reforming
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the reforming of a solo in a solution into a crystal that process I just mentioned is known as precipitation and it happens in the air as well you have air look at the in front of you it has water vapor in its just not completely saturated if you to saturate that Aaron trying to do well in condensation would occur when condensation occurs the water vapor molecules in the solution of air are reforming into water molecules that's known as precipitation so NaCl
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sodium chloride is not exist as a salt and sand and sea water so you don't have like salt in sea water what you have is its component elements that are separated by the water molecules and still tastes like salt because voters are there but they're actually broken apart into the solution now if you evaporate the water that NaCl then recrystallized and what will be left over is the salt salinity is the total quantity of dissolved inorganic solids the water so salinity
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how much salt in the ocean water is not just how much salt table salt sodium chloride but the total quantity of dissolved inorganic solids in water the average salinity is about 3.5 percent most of the dissolved solids are salts have been separated into ions are basically the weathering of rocks on the countenance a weathering whether its chemical weathering a physical weathering breaks down Roxana much much smaller pieces eventually getting them
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down to just their ions those ions flow downstream and end up in the the ocean that's how we've sulphides the ocean so sodium and chloride are the most abundant ions and see what about you can see there's lots of others well as obviously oxygen hydrogen but there's sodium sulfate magnesium calcium potassium bicarbonate which creates carbonic acid which makes the attic but any of those any of those major constituents can wreak resizer magnesium
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can literally recrystallized in the ocean as magnesium and calcium camp to calcium carbonate that's free get the shells of animals that's what animals mullis in different sea life sentence phytoplankton and zooplankton still take the carbon dioxide and the calcium out of water in the make a calcium carbonate shell and corals did the same thing
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the soil you see what's in nearly every element present in the crust and the atmosphere is also president the ocean so all the elements in the crust of the earth and all the elements that are in the atmosphere eventually break down and get mixed into the ocean quitting the cells at 3.4 for brands that almost 3.5 percent if you take that three point four 4 grams and break that down mostly it's chloride done a lot of sodium sulfate magnesium carbonate calcium and
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others right and this is the process by which they became salty this process that regulates the major constituents of seawater I under added to see what about rivers running off Trussell rocks + excess volatile from volcanic activity around water that's how you get some of those ions hydrothermal vents give you some of the ions and cold springs and the decay of one's living organism gives you ions ions are removed from the ocean by chemical and trap as water percolates
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through the mid-ocean ridge meaning as one goes back down into the rocks of the of the ocean crust some those ions are pulled out and then lost to the crust an awesome different places like see males and underwater volcanoes seaspray will take some of those irons out you get up take my living organisms that are held in organisms carbon dioxide and calcium out to make their shells incorporation in the sediment some of those things are held in the sentiment in a Minnesota man
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is buried in ultimately were settlement that just gets abducted back down into the cross and that's how those major constituents are basically held in a uniform proportions that that cycle so the principal principal concert portions say the salinity of various samples of seawater may vary but the made the region ratio the major salters constants are you may have slightly more assailing or slightly less sailing sea water but the ratio of those salt is always
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constant this litany has a total amount of dissolved materials and one kilogram of water measure with this sailing a meter the ocean is always in keep the chemical equilibria and proportion in the amounts of dissolved solids remains constant that's that's a principal consummate portions I enjoy being added to remove from the ocean the same rate the proportion amounts of dissolved solids remains constant and is known as a steady-state ocean Selanne like season like this landlocked seas were just
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continually have more ions pumped into them from rivers flying off this season the Dead Sea or the Great Salt Lake and they just become saltier insulting and saltier answering denser and denser processes that add salt such as weathering of rocks are balanced the process of moving salts such as the burials sediment residence time is the average length of time in elements pins in the ocean all right there are conservative constituents and non-conservative
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constituents are conservative constituency where are those who situated occur in constant proportions conservative elements have long residence time the most abundant non-conservative constituents have short residence times usually associate with seal seasonal or biological or short geologic cycles have a big algae bloom and the algae bloom is gonna suck up all the oxygen in the water see our or our cause other things to happen so
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sometimes biological events or seasonal events or short geologic cycles like a lot of a clock and ISM may change that is not conserved constituents gases in seawater most gases in the air dissolve readily into seawater at the ocean surface of the ocean in contact with the atmosphere you get lots of great dissolution or dissolving of those gases in sea water plants and animals live in the ocean need those dissolved gases to survive nitrogen oxygen carbon
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dioxide are all found in seawater the proportion of dissolved gases in the oceans different for the proportion in the atmosphere significantly different amounts of carbon dioxide in the ocean is in in the atmosphere significant amounts of oxygen as well and those differences are largely due to the ability of gas to dissolve in water and air unlike solids gases dissolved more readily in cold water if you take a solid salt sugar and you put it in warm water it's Canada's all very quickly if
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you ever taken a big teaspoon of sugar and put in cold iced tea is very difficult to get it to dissolve but the opposite in water and gases dissolved very very easily in cold water because ions in seawater react with each other and was watering complex ways they modify the physical properties of pure water these are called the ecology of properties the heat capacity of water decreases its ability to hold he decreases with increasing soledad eat
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less heat is required to raise the temperature sea water than fresh water as salinity increases freezing point decrease sea ice forms at lower temperatures in fresh water so it takes colder air colder water to form sea ice then it does fresh water ice as salinity increases evaporation slows dissolved salts tend to attract water molecules so it's very difficult for evaporation have increased tapping into a salty water and the osmotic pressure increases as
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salinity increases the reference osmosis the pressure on a biological membrane increases as the salinity of the environment increases nature trails achieve equilibrium said you've got some biological membrane separating two reservoirs of seawater one is more sailing in the other two pressure pushes that that's literally across the membrane and tries to get equilibrium between the two entities so gases dissolve readily in seawater nitrogen
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which is a conservative component meaning it's always in the same proportion makes up about 48% of the dissolved gases in seawater the upper layers are saturated with it all life needs it but interestingly enough most organisms including human beings can actually use dissolved nitrogen has to be fixed in the nitrates we can use by other organisms specifically bacteria certain types of oxygen makes up 36% now of of the other gases forced vital for animals it comes from photosynthesis
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and dissolve in the atmosphere it's a non-conservative component it can change depending on biological activity there's one hundred times more in the ocean oxygen that is in the atmosphere and there is sixty times more carbon dioxide in the ocean than in the atmosphere ocean is considered the great carbon sink where carbon dioxide can be sequestered in held and kept out of the atmosphere of course carbon oxides used info to send a sister plants and it
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comes also from respiration or we take in oxygen and then we breathe out carbon dioxide co2 and other animals in the ocean it's also dissolve from the atmosphere and it's also a non-conservative component it can change depending on what's happening in the ocean at the time alright the carbon cycle which is actually a fascinating in this illustration does a tremendous job of breaking it down but it's very very complex and the carbon cycle and how carbon certain migrates to the cycle can
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have a huge impact on global climate in part of the reason why over very vast geologic spans of time global climate change so the carbon carbon dioxide combines readily with sea water to form carbonic acid carbonic acid can then lose a hydrogen ion and become a bicarbonate ion or to hydrogen ions to become a carbonate ion some bicarbonate ions break down to form carbonate ions which combined with calcium ions in seawater so carbonate ions are you get from from to hydrogen
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ions becoming a carbonate ion or bicarbonate breaking down and when you have these carbon ions they combined with calcium to form calcium carbonate and calcium carbonate is is hard it's it's like limestone or it's like the shells of sea creatures or the hard Skelton's of sea creatures or electoral so when those creatures died those structures may fall to the seabed as carbonate sediments eventually 23 dissolve and in turn into carbon dioxide and water again or sometimes are buried
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and compacted a little fight in turning the carbonate rock like limestone like I said that as the carbon cycle and as the double arrow indicates all these reactions can go in either direction so carbon cycles through the atmosphere into the ocean and then into calcium carbonate which can dissolve or be buried and then sometimes very little fighting in Iraq sometimes deducted sometimes coming out in a whole different part of the world and bottom
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line is there's a massive carbon cycles very complex but it can have a profound impact on the global climate so this is how we see the different gases oxygen and carbon dioxide dissolving in sea water oxygen is abundant near the surface because of the photosynthetic activity of marine plants all those plants at the surface taking advantage of sunlight are partaking in carbon dioxide and spitting out oxygen said Israel carbon dioxide close to the
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surface in a great deal of oxygen close to surface now oxygen concentration decreases below the sunlit later because of the respiration and rain animals and bacteria meaning that animals are breathing out carbon dioxide but taking in oxygen in those lower layers layers money to send it later that's a thousand meters down or four thousand feet down and and has no plans said that lower layers no plans to give off more oxygen so you have oxygen being consumed but no
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oxygen being given off by plans and then oxygen is consumed as well by the decay of tiny dead animals slowly sinking to the area so in contrast plants use carbon dioxide during photosynthesis service levels of co2 of a low because photosynthesis cannot take place in the dark CEO to give enough animals and battery tends to build up at depths below the sunlit layer so co2 also increases with depth but because its solubility increases as pressure increases in temperature decreases so it's it's all
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complex that you can see that there's way more oxygen to servicing carbon dioxide and then carbon dioxide is going to increase as you go down because biological animals are down in that dark layers so those biological animals are going to give off co2 M&A gonna take up oxygen talk a little about ocean surface conditions average surface temperature and salinity for the world ocean as you would expect temperatures are lowest the
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polar regions and highest at the equator heavy rainfall in the equatorial region refreshes the ocean near the equator where the hot dry conditions in the subtropics results in higher surface salinity meeting at the equator you have a lot of fresh water from the sky sea of lower salinity but at about 30 degrees north and south latitude those who were the world's deserts are because the global atmospheric circulation thinking here there much rain and so you have
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high salinity in those areas said the salinity changes at the surface based on essentially the atmospheric conditions and climate sea surface temperatures and during the Northern Hemisphere summer of 83 c4 exactly what you'd expect in the warmer at the equator and in colder at the polls variations in temperature salinity and density are usually confined to the uppermost 2000 metres the deep ocean is nearly as salty called intense as the
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equator then as it is also the difference in salinity and temperature that occurs at the surface when you get deep down there's not a lot of changes in salinity and temperature and there you see service average synergies in parts per thousand his highest ladies about 30 degrees north and south latitude in the lowest ones they're very close to the equator alright let's talk a little about acid and base solutions and asset is a substance that releases a
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hydrogen ion in solution in a base is a substance that combines with hydrogen ion in solution in say you get alkaline solutions a solution that is basic and the new have aesthetic solutions so acid or alkalinity is measured on the pH scale and you probably heard about the pH scale most your life couple different views the pH scale so an acid is a substance that releases a hydrogen ion and HD+ in solution excess hydrogen ions makes it ascetic basis a substance that
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combines of the hydrogen ion service solution containing a base is called alkaline they typically have excessive wage plus so city Rockland and he is measuring the pH scale with neutral pH basis above seven in assets below 70 the higher get above seven the more basic you are late drain cleaner from pneumonia and dangerous stuff soap and the further you get below seven the more acidic you get such as like tomatoes and then lemons and then eventually you get
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to hydrochloric acid very acidic solution and so the bottom line to all this is the pure water is right at seven pure water is it seven that salt water is more acidic like milk is being a city that is slightly acidic and rainwater slightly acidic as well the more carbon dioxide in the water the more acidic that water is going to be so excess carbon dioxide in the ocean acidified the ocean so the oceans had time to adjust to any increase in acidity
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laments that pretty much carbon dioxide he also just
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as a result their timing acidic faster than they have for millions of years
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the force creatures will suffer will be the coral make up the world's great reefs their skeletons can't form of the water becomes to a city
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if the oceans continue to a certified their current rate could eventually disappear from our oceans
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with the coral would go all the other like that depends on them intimately connected with the conditions that these changes in the certification continues call would be just the beginning phytoplankton are also vulnerable to increasing acidity in the sea
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in the long term this could endanger one of the main sources of oxygen on the planet but what about the short term but will these changes in the oceans mean for us for millions of years we are heading into so we really do implications
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what we do know is that the oceans are fundamental
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ultimately the survival and every creature on the planet depends on the oceans remaining healthy the difference in temperature is the difference in salinity was adept causes the ocean have density differences there's a complex relationship between temperature salinity and the density of seawater the density of water is mainly a function of the differences in temperature and salinity and you can see by the chart with temperature on the left and salinity the temperatures going
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to the Y access the x-axis across across a horizontal and the lines of blue those represent density levels one point zero to four one point zero to five g/cm you can have the same density with different or varying amounts of temperature or salinity but as the ocean becomes density stratified with least dense on top in the dense as water below you get this disarray specifically layered set up to the ocean structure it causes the ocean to be divided into three densities
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owns the surface own designer Klein and the deep south on the surface owners the uppermost layer or the mixed layer that has the least dense water is the warmest and it's the least sailing an up-and-down mixing vertical mixing to the waves and currents keeps the temperature in the salinity pretty constant in that first 150 meters making up about 2% of the ocean volume and in the next zone down more dances the zone in which density increases with depth
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containing by 18 percent of the water this extends from about 150 meters to about a thousand metres and this layer separates the surface water from the dense as water below in this this layer represents a rapid density increased water is becoming colder and saltier in the in the air density is increasing now the deep zone contains about 80% of all ocean water this very little change in density throughout this layer and the general cause of the increase in density
44:57
certainly is slight so many differences but it's it's mainly through the deep layer the difference in those temperatures are with the warmest temperatures the top of the ocean in the air service zone having the least dense water and this coldest temperatures and even having them the most dense water alright so in most of the ocean a surface on the mixed layer relatively warm low-density water over lies the psyche psychic line and the density rapidly increases with
45:27
deaths in the second line below that lies it deep zone of cold dense water the rapid density increase in cyclic line is mainly due to a decrease in temperature with death so in that area that rapid decreases because of a decrease in temperature and some regions in shallow waters near rivers see that that's a decline may develop in which the density increases with depth is due to vertical variations in salinity so we talked about it being due to temperature
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mainly but if you have a lot of fresh water than it could be that you have the freshest lot of the top and more salty water below it and that's what creates decided Klein and in that situation have Halo climb which is changing salt also when precipitation evaporation is lots and lots of rain but not much evaporation cooler climates are also you get fresh water to service in that case you gonna have the the halo clients so typically that middle zone that site
46:25
decline that rapid increase in density with depth is a function of a temperature drop the thermocline the drop from warm waters at the surface to call the waters below but sometimes there is a drop in or a change in increase in salinity and that's the halo Klein so the site to climb is is a combination of former client halo Klein just different regions have different physical selves so here's a typical typical temperature profile at the polar
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tropical and middle latitudes the polars in blue with very little temperature difference from the surface to the CD player the the tropical or have a significant temperature decrease from the surface waters down to the deep zone in the the temperate areas the middle latitudes where you don't have as much more pronounced change so there is no thermocline in the polar waters it's all available and it's all a salinity difference that keeps that water and the polar regions density stratified so
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water masses have characteristic temperatures seventies in densities layering of the water masses made in C traps dense water masses at great depths the site decline effectively cut off eighty percent of world ocean the 20% involved in service circulation density stratification usually prevents vertical water movement large volumes of vertical water movement only occur where there is little density difference between the surface water in the deep water at the
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ocean's depths so here's another view of that showing the difference in the polar which is going to be at either end of this chart to the temperate regions in mid-latitudes in the in the equatorial regions reconsider very warm water creates that pronounced temperature difference with depth next move to talk about how light and sound moves through the ocean waters very interesting the attacks here light is a form of electromagnetic radiation or radiant energy it travels
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as a wave-like travels as a way through space into air and water sunlight does not travel well in the ocean scattering occurs when light is mount between air and water molecules dozen other objects so as the Sun light travels the atmosphere about half of it is either scattered or selected away the Ford strikes the surface and then absorption occurs when the lights electromagnetic energy is converted into heat in sea water molecules so in the light strikes to service the ocean and
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heated up then there's some absorption of electromagnetic radiation so there is a thin film of lighted water at the top of the circus that's called the photic zone because of the scattering of light by water molecules in an air molecules and because the absorption of electromagnetic radiation of light by water molecules there's only a thin film of lighted water at the top of the surface soon and that thin films called the photic zone so sound and light both traveling waves and because they
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traveling waves they can be retraction or reflection or scattering absorption is a said refraction is the bending of waves light waves and sound waves can both be dead and that occurs when waves travel from one medium to another specifically mediums of different densities are here you have other white light of cell a traveling through the less dense air and then you can see it strikes I whether some see spread as a lot of water vapor in the air and it
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literally bins that those light rays because it's a more dense medium incidentally bends low rates so the refractive index is a ratio that expresses how much light is refracted from one medium to the other and the refractive index of water increases with increasing salinity says a study goes up comes more dance the reflectivity of water increases as well so that's its ability to bend light waves or sound waves so what're transmits blue light
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more efficiently than red light so if you take all the sunlight we refer to that as white light all the visible light from the Sun it's between about three hundred and eight hundred micrometers of wavelengths that the literally that the length of the waves between one question the other and so the blue light travels through water most easily so only a thin layer of surface seawater is illuminated by the Sun acceptor light generated by other
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living organisms mostly ocean lies in blackness absorption of light by different wavelengths by seawater can be seen here where much of the Reds are absorbed a lot of oranges violence but a lot of the blue is allowed to trends transmitted into the ocean and that of course is the reason why does look blue now sound travels in the ocean and there's a real relationship between the water depth and the velocity the sound moves so sounds philosophy in the atmosphere some
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of chain 1475 and 1,500 meters per second once it goes into the ocean as it gets deeper and deeper there is a higher sound velocity initially and then the sound velocity drops to a minimum and then again at great depth that sound velocity will begin to increase so sound can travel for a much greater distances in water than in light so the reason why sound can travel greater distances is because the water molecules are touching
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each other and so the compression nature of those sound waves moose the water more easily of course he put down to the desk and knock on your desk you know that sound moves most easily through solids so the speed of sound in seawater increases as temperature and pressure increases the speed of sound increases with increase pressure but it also increases with increase in temperatures in interesting thing where you see a a drop in temperature and a
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drop in speed with death and then as you get much much deeper the increase in pressure causes the velocity of the sound to increase against a very interesting curve there relating the speed of sound who water with the depths of the ocean refraction bends light and sound and it also bans winds waves ocean waves so this is in analogy for a fraction we talk about the density differences if you have pavement in San and have a marching band marching along I'm going to consider the pavement
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to be less dense and Benjamin walking through san is more difficult than walking across basement so the ranks of marches represent the light or sound waves the pavements and represents different media the marchers can walk faster they stand the pavement if they wanted this annex the highway the sand is denser so the marchers head off the pavement at an angle other than 90 degrees there Pathol been wracked as they hit the sand because the people
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walking in the sand initially will slow down and that will cause and the slowdown caused in order for the the line to catch up to me straight again the people on the outside had to speed up and that causes that that that waived if end if they marched straight off the pavement the ranks which has slowed down but they won't bend so this difference in density is what dens or roof racks sound waves are lightweights think all day so far layer which is this sound fixing and ranging later in which
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sound waves travel at their slowest speed sound transmission is particularly efficient that is heard from great distances because refraction tends to keep the sound waves within that layer so that that that that layer of minimum speed the difference in a density to above and below causes the sound waves to bend back into that layer that so far later that sound mixing in ranging layer and and so the Desi difference below the density difference above causes the
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sound waves are bent into that one channel which means that sound transmission is very efficient at that level can we talk about listening within the ocean if you put listening stations down at that level that thousand meter level three thousand-plus field level you can hear literally in the ocean from all around the world because sound travel so efficiently in that so far lower alright and so looking at the the last slide here for the lecture lecture
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6 this is basically looking at Sonar as in-house seminars work a sonar system it a sound wave in Soundwave goes down and reflects off of an object in the sonar listens for the reflection come back so principal active sonar pulses of high-frequency sound irradiated from the SRA of this inning vessel some of the energy of this thing that omission of high-frequency sound reflects from the submarine returns to the sinking vessel and the echoes analyzed position Summary
55:17
pretty pretty standard stuff we talked about that earlier in the semester we're talking about how we determine the depth of the ocean was chapter 6 water and oceans structure next we'll be taking a look at chapter 7 I'll be on atmospheric circulations and the global circulations the atmosphere
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