Chemical and Physical Features of Seawater and the World Ocean If there is magic on this planet, it is contained in water. Loren Eiseley Well, me dont swim too tough so me dont go in the water too deep. Bob Marley What is Water ? Introduction the stuff covers 70% of the Earth Brainstorming activity Chemical & Physical Properties of Water Categorization activity Defend your categories If time permits why the answer to life is 104.5 Chemical & Physical Properties Physical property properties that describe a substance without changing the identity of the substance. Physical change change that does not result in the production of a new substance, only the appearance of the substance Physical change change that does not result in the production of a new substance, only the appearance of the substance Chemical property properties that describe how a substance changes into a completely different substance Chemical change change that results in the production of another substance Chemical change change that results in the production of another substance Common Properties of Water Physical Properties Chemical Properties Cohesion/Surface tension Found in all three states on the earth Universal Solvent dissolves more substances than any other common liquid Conduction of heat highest of all liquids (except for mercury) pH water dissociates into anions (OH - ) and cations (H + ) Latent heat of vaporization highest of all common substances Polarity water has positive and negative ends Latent heat of fusion high for a molecule of its size (melting/freezing) Hydrophobic effect Heat capacity highest of all common solids & liquids Density max at 4C for pure water Viscosity relatively low for a liquid References Castellano, A. (2006) Victoria Beach Castro, P. & M.E. Huber (2005) Marine Biology, 5 th ed. McGraw-Hill Higher Education, Boston, MA. Chemical Properties of Water PlanetWater.au.com Retrieved on Feb 3, 2007 from floating water 5 (2006) wester Lower, S. (2007) H 2 O a gentle introduction to the structure of water. Retrieved on Feb 3, 2007 from Nybakken, J.W. & M.D. Bertness (2005) Marine Biology, An Ecological Approach, 6 th ed. Pearson Education, Inc., San Francisco. Perlman, H. (2006) Water properties Water Science for Schools. USGS. Retrieved on Feb 3, 2007 from Petrucci, R.H. (1982) General Chemistry Principles and Modern Applications, Macmillan Publishing Co. Inc., New York. The Water Molecule Two hydrogen atoms, one oxygen atom H atoms form 105 angle This angle produces an asymmetrical dipole. Slight (+) charge on the H atoms and slight (-) charge on the O atoms. O HH 105 The Water Molecule These slight charges cause the (+) H atoms of one water molecule to attract the (-) O atoms of other water molecules. These weak bonds are called hydrogen bonds. Water can hydrogen bond with other substances aside from itself. O H H O HH O HH Why does ice float? Density-Temperature Relationship Background Temperature is a measure of kinetic energy (K E ). As K E decreases, hydrogen bonds stay formed and break less. Water molecules stay closer together until Explanation As the temperature approaches 4C, less dense ice clusters begin to form in the liquid. At 0C when all water molecules become locked in the rigid ice lattice, the hydrogen bonds actually hold molecules farther apart than at 4C. This creates spaces making the water less dense. Why does ice float? Density-Temperature Relationship Graph The cohesion or mutual attraction of water molecules creates a flexible barrier on the surface of water. This helps support aquatic insects such as water striders (Halobates sp.) How can water bugs stride across water without breaking the surface? How can water bugs stride across water without breaking the surface? Surface tension and cohesion Why do fish not get electrocuted when lightning strikes the ocean? Conductivity Explanation Conductivity is a property that measures the ability of a substance to transmit heat, electricity, or sound. Pure water is not a good conductor of electricity. Its conductivity is about 20 dS/m. (Compare with silver the highest conductivity with 63 x 10 6 S/m) In addition, the electrical charge of lightning usually spreads instantaneously along the surface of the water from the location of the strike and to a lesser degree below the surface at the strike site. Fish in other areas are not affected. Background Heat energy of molecular motion Water can absorb or give up heat by conduction (molecular exchange of heat) or convection (mixing) Explanation Water can hold heat longer and release heat more slowly than land. Temperature differential between land and ocean will cause uneven heating of air masses which drive winds and moderate any drastic temperature changes. Why do coastal areas have slower temperature changes than inland areas? Why do coastal areas have slower temperature changes than inland areas? Heat capacity Off-shore breeze On-shore breeze Fats and oils are nonpolar molecules. These compounds do not have slight regions of charge like water does. These compounds do not have slight regions of charge like water does. Therefore water molecules are not attracted to nonpolar molecules and actually can be repelled by them. Basis for cell membranes and the water repellency of marine mammals and birds. Basis for cell membranes and the water repellency of marine mammals and birds. Why dont fats and oils dissolve in water? Why dont fats and oils dissolve in water? Polarity Because water is polar, it dissolves most substances, especially other polar molecules and compounds composed of ions, atoms or molecules that carry an electrical charge. These ionic compounds are often called salts. NaCl (salt) most common dissolved salt in ocean. There are many others. Seawater is a solution of these salts. Why does water dissolve more substances than any other common liquid? Why does water dissolve more substances than any other common liquid? The Universal Solvent Salt crystal Seawater Sources of salts and dissolved solids: Erosion of rocks and soil Breakdown of organisms Condensation of rain from the atmosphere Releases from hydrothermal vents Seawater is 96.5% water 3.5% dissolved compounds Salinity Measured in parts per thousand (ppt) Grams of salt left behind when 1000g of water evaporate Grams of salt left behind when 1000g of water evaporate Average value 35 ppt or 35 Range from 0 near river mouths to 40% in the dead sea. Globally, seawater salinity remains constant. Rule of constant proportions states that the percentage of various ions in seawater remains constant. Total amount of dissolved salts in seawater. Surface Salinities of the Oceans Dissolved compounds in seawater Inorganic substances (salts, nutrients) Dissolved gases Organic compounds (fats, oils, vitamins, amino acids, proteins) Nitrates and phosphates (usually in excess as pollution) Pollution (DDT, PCBs, chlorinated hydrocarbons that are synthetic) Dissolved Gases Primarily nitrogen, carbon dioxide, oxygen N 2 biologically inert. CO 2 needed for photosynthesis and pH buffering. O 2 required for respiration.stories/s htm Factors that Affect Salinity Salinity increases due to freezing of seawater. freezing of seawater. evaporation. evaporation. Salinity decreases due to melting of icebergs and sea ice. melting of icebergs and sea ice. precipitation. precipitation. run-off from rivers. run-off from rivers. pH The amount of hydrogen ions in a substance is referred to as pH. pH = (pondus hydrogeni or power of hydrogen pH = (pondus hydrogeni or power of hydrogen pH = -log 10 [H+] pH = -log 10 [H+] Scales ranges from 0 to 14. Scales ranges from 0 to 14. Therefore, a pH of 14 means that the water is very alkaline (basic) while pH 1 means it is acidic. A pH of 7 is neutral. Seawater pH The carbonic acid bicarbonate carbonate system keeps seawater at a pH value between 7.5 and 8.4. The oceans are an enormous sink for atmosphere CO 2 The Carbon Buffering System Seawater has an unusually large capacity to absorb CO 2. CO 2 + H 2 O H 2 CO 3 (carbonic acid) H 2 CO 3 H + + HCO 3 (bicarbonate ion) H 2 CO 3 H + + HCO 3 (bicarbonate ion) HCO 3 H + + CO 3 2- (carbonate ion) HCO 3 H + + CO 3 2- (carbonate ion) Work Cited Kreger, Chris. "Acid Mine Drainage: Alkalinity." Exploring the Environment: Water Quality Wheeling Jesuit University. 2 Oct Lower, Stephen. "A gentle introduction to water and its structure." H2O Oct "October 2006 Archives." [Weblog The Marine Electronics Weblog] Oct Panbo. 1 Oct Water Conductivity Lenntech Water Treatment & Purification B.V.. 1 Oct Woodruff, Steve W.. "Water & Weather." Los Angeles Pierce College Weather Station. 1 Oct 2008. The Salinity-Temperature-Depth Relationship in the World Oceans Part One Depth Profiles Seawater General Trends Temperature and salinity determine the density of seawater. Colder water is more dense; therefore, it sinks. Colder water is more dense; therefore, it sinks. Saltier water is more dense; therefore, it sinks. Saltier water is more dense; therefore, it sinks. Which is more variable on the earth? Temperature or salinity? Which would have a greater effect on the density of seawater? Temperature or salinity? Global Sea Surface Temperature This image shows the temperature of the ocean water at the surface. Measurements were taken from August 6-11, The temperature scale is in Celsius. Cold temperatures are shown in pink to purple, moderate temperatures in aqua to green and warm temperatures in yellow to red. This particular data set was taken by the NOAA-16 satellite. NOAA-16 is part of the TIROS series of polar-orbiting, environmental satellites. Image courtesy of The National Oceanic and Atmospheric Administration (NOAA) The National Oceanic and Atmospheric Administration (NOAA)The National Oceanic and Atmospheric Administration (NOAA) Surface Salinities of the Oceans Biogeographical Zones Based on sea surface temperature, four major biogeographical zones emerge: Polar Polar Cold temperate Cold temperate Warm temperate (subtropical) Warm temperate (subtropical) Tropical (equatorial) Tropical (equatorial) Global Sea Surface Salinity Depth Profiles Graph that shows a specific ocean variable plotted against depth. Usually drawn upside down with increasing depth on the Y-axis and the variable across a top X-axis so that the graph represents an ocean profile. Usually drawn upside down with increasing depth on the Y-axis and the variable across a top X-axis so that the graph represents an ocean profile. For any specific location, a depth profile can be understood as a vertical snapshot of a column of water or water column. For any specific location, a depth profile can be understood as a vertical snapshot of a column of water or water column. Increasing variable 0 Increasing depth (m) Depth Profiles Which one represents temperature? salinity? National Oceanic and Atmospheric Association (NOAA) Depth Profiles How do temperature and salinity contribute to density? National Oceanic and Atmospheric Association (NOAA) Salinity-Temperature-Depth Profile Lamont-Doherty Earth Observatory Thermocline the depth zone of the most rapid temperature decline Halocline the depth zone of the most rapid salinity change Pycnocline the depth zone of rapid density change Other Profiles What might the depth profile look like for the following variables? Dissolved oxygen Dissolved oxygen Transparency of light Transparency of light Pressure Pressure Light Transparency This diagram offers a basic illustration of the depth at which different colors of light penetrate ocean waters. Water absorbs warm colors like reds and oranges (known as long wavelength light) and scatters the cooler colors (known as short wavelength light). Image courtesy of Kyle Carothers, NOAA-OE Light Transparency Sunlight is composed of colors with different wavelengths ROY G BIV Longer wavelengths (red/orange) have lower energy than shorter wavelengths (violet/indigo) E = hc/ E = hc/ where E = energy, h = Plancks constant, c = speed of light, and = wavelength where E = energy, h = Plancks constant, c = speed of light, and = wavelength Light Transparency General trends: Longer wavelengths are absorbed at the surface. Shorter wavelengths can penetrate to depths of approximately 1000m in clearest waters. Extent of light attenuation defines photic zone Euphotic zone surface to approx. 200m max. sufficient sunlight for photosynthesis Euphotic zone surface to approx. 200m max. sufficient sunlight for photosynthesis Disphotic zone variable m, usually m insufficient sunlight for photosynthesis (less than 1% of sunlight penetrates) Disphotic zone variable m, usually m insufficient sunlight for photosynthesis (less than 1% of sunlight penetrates) Aphotic zone below disphotic zone no light Aphotic zone below disphotic zone no light Pattern can vary with suspended/dissolved substances. More suspended/dissolved substances less light penetration Dissolved Oxygen Oxygen (ml per L) Depth (m) Change in dissolved oxygen with depth in eastern tropical Pacific Ocean (red line) and the tropical Atlantic Ocean (orange line). Modified from Oceanography: An Introduction, D.E. Ingmanson & W.J. Wallace, 1973. Oxygen non-conservative low solubility in seawater only 5.4 ml/L at 35 ppt and 20C (8 ml/L at 0C) more soluble in colder water less soluble in saltier water oxygen minimum zone usually 500 to 1000m depth Dissolved Oxygen Oxygen Minimum Zone depth in open ocean waters at which oxygen concentration approaches zero usually between 200 and 1000m Why there? Inputs of O 2 to the oceans wave action, storms, surface mixing, photosynthesis Depletion of O 2 from the oceans respiration, decomposition At this depth, consumption of O 2 by organisms for respiration consumes all of the oxygen, without suitable replacement by photosynthesis or surface mixing. Pressure Pressure (atm) Depth (m) Surface 1 atmosphere of air (1kg/cm 3 or 14.7 lbs./in. 2 or 1 bar) pushing down at sea level With Depth water more dense than air each 10m of depth increases pressure by an additional atmosphere linear relationship What is significance for marine organisms? What is significance for marine research and exploration? References Castro, Peter, and Michael E. Huber. Marine Biology. 5th. Boston: McGraw Hill Higher Education, Davidson, M.A., Abramowitz, M., Olympus America, Inc., and Florida State University, (2003 Aug 1). Optical Microscopy Primer. Retrieved February 21, 2007, from Molecular Expressions Web site:Enchanted Learning.com, (2007). Twilight Ocean (Disphotic) Zone Animal Printouts. Retrieved February 21, 2007, from Biomes-Habitats Web site:Naik, Naomi. "Plot the Temperature Profile." Climate Kids Corner. Lamont-Doherty Earth Observatory. 19 Feb 2007 National Oceanic and Atmospheric Association (NOAA) (2007 Feb 12). Deep Light. Retrieved February 21, 2007, from Ocean Explorer Web site:National Oceanic and Atmospheric Association (NOAA). "NOAA/NESDIS Edge Image Display." Windows to the Universe LUniversity Corporation for Atmospheric Research (UCAR). 19 Feb Nybakken, James W., and Mark D. Bertness. Marine Biology: An Ecological Approach. 6th. San Francisco: Pearson Education, Inc., photic zone. (2007). In Encyclopdia Britannica. Retrieved February 20, 2007, from Encyclopdia Britannica Online: Quiz Tomorrow Salinity-Temperature-Depth Relationships Depth Profiles Thermocline Thermocline Halocline Halocline Pycnocline Pycnocline Light Light DO DO Pressure Pressure Stratification (three layers) Stability Overturn Global Thermohaline Circulation The Salinity-Temperature-Depth Relationship in the World Oceans Part Two The Three-Layered Ocean and the Great Conveyor Belt The oceans are three-dimensional Horizontally from north to south/ east to west (geographic changes) Horizontally from north to south/ east to west (geographic changes) Vertically depth Vertically depth Which dimension has the biggest influence on living conditions? DEPTH this third dimension is controlled by density What two variables have the greatest effect on density? TEMPERATURE & SALINITY Stratification Less dense water (warmer/less salty/or both) floats at the surface Denser water (colder/saltier/or both) tends to sink Creates stratification essentially causes layers to form in the ocean. essentially causes layers to form in the ocean. imparts vertical stability to the ocean imparts vertical stability to the ocean The Three-Layered Ocean Surface layer surface to approx. 200m surface to approx. 200m also called the mixed layer, because it is mixed by wind, waves, currents, & storms also called the mixed layer, because it is mixed by wind, waves, currents, & storms may be the only layer found in shallow coastal waters over the continental shelf may be the only layer found in shallow coastal waters over the continental shelf seasonal thermoclines may form here seasonal thermoclines may form here Intermediate layer bottom of surface layer to approx. 1,500m bottom of surface layer to approx. 1,500m main thermocline can be found here main thermocline can be found here Deep & bottom layers below 1,500m below 1,500m uniformly cold (less than 4C) uniformly cold (less than 4C) Deep & bottom layers Depth (m) Intermediate layer Surface layer Stability Stability likelihood that a water column in the ocean will remain stratified. High stability large density difference between deep and shallow water keeps water column stratified Low stability slight density difference between deep and shallow water relatively easy to mix the two layers Overturn Instability (unstable) surface layer becomes more dense than deep layer surface layer becomes more dense than deep layer surface water sinks resulting in downwelling surface water sinks resulting in downwelling process known as overturn process known as overturn What might a depth profile look like when downwelling occurs?What might a depth profile look like when downwelling occurs? Straight Line Profiles Straight Line Profiles What climate conditions might cause downwelling?What climate conditions might cause downwelling? Occurs in temperate/polar regions in winter when surface water cools Occurs in temperate/polar regions in winter when surface water cools once water sinks, its temperature and salinity do not change since the processes that change them are surface phenomena once water sinks, its temperature and salinity do not change since the processes that change them are surface phenomena becomes a signature for the water massbecomes a signature for the water mass oceanographers can follow these water masses as they circulate throughout the oceansoceanographers can follow these water masses as they circulate throughout the oceans Global Thermohaline Circulation Gets its name from fact that it is driven by density differences in water masses which are in turn caused by temperature and salinity differences. It acts as a giant conveyor belt. Importance: Extends throughout ocean depths Regulates the Earths climate Transports heat and nutrients throughout globe Chemically mixes the worlds oceans Brings oxygen-rich surface water to the deep sea Great Ocean Conveyor A Critical Look IPCC Intergovernmental Panel on Climate Change The Great Ocean Conveyor Water sinks Norwegian Sea (North Atlantic Deep Water NADW) Norwegian Sea (North Atlantic Deep Water NADW) Forms due to heat loss and high salinityForms due to heat loss and high salinity Labrador Sea Labrador Sea Deep convectionDeep convection Weddell Sea (Antarctic Bottom Water ABW) densest Weddell Sea (Antarctic Bottom Water ABW) densest Forms mostly because of low temperatureForms mostly because of low temperature and returns to surface. Indian Ocean Indian Ocean North Pacific Ocean North Pacific Ocean Both due to warming by equatorial temperatures and the parting of ocean water by equatorial tradewinds.Both due to warming by equatorial temperatures and the parting of ocean water by equatorial tradewinds. An oceanic roundabout. As warm ocean currents in the subpolar gyre gradually cool, they warm Europe and may trigger seesaws in climate (McCartney et al., 1996, Oceanus, 39, 19-23) Main Currents in the North Atlantic The thermohaline circulation "conveyor belt". Purple arrows indicate cold, deep ocean currents. Red arrows show shallow, warm water circulation patterns. Credit: Image courtesy CLIVAR (after W. Broecker, modified by E. Maier-Reimer)CLIVAR Thermohaline Circulation in 3D! Role of THC in Climate Change Brings warmth from the tropics to higher latitudes Particularly in the North Atlantic Particularly in the North Atlantic Has shut off in recent geologic past (12,800 years ago - the Younger Dryas) (12,800 years ago - the Younger Dryas) Evidence Evidence Oxygen isotope and carbon dioxide isotopes in ice coresOxygen isotope and carbon dioxide isotopes in ice cores Foraminifera and glacial deposits in sediment coresForaminifera and glacial deposits in sediment cores Low latitude glaciologyLow latitude glaciology LDEO - Abrupt Climate Change - Younger Dryas ExplanationLDEO - Abrupt Climate Change - Younger Dryas ExplanationLDEO - Abrupt Climate Change - Younger Dryas ExplanationLDEO - Abrupt Climate Change - Younger Dryas Explanation SATELLITES SEE GULF STREAM WARM WATERS This is a NASA satellite image of the warm waters of the Gulf Stream running up the U.S. eastern seaboard. The Gulf Stream shows up as a winding rope of orange and yellow (indicating warm waters) against the cooler green and blue waters. Credit: MODIS Ocean Group NASA/GSFC SST product by U. Miami References Castro, Peter, & Michael E. Huber. Marine Biology. 5 th. New York: The McGraw-Hill Companies, Inc., Hoffman, Jennifer. Science 101: Ocean Science. Irvington, NY: Harper Collins Publishers, Inc., Kunzig, Robert. "In deep water." Discover Dec 1996: Naik, Naomi. "2: What scientific evidence do we have that abrupt climate change has happened before?." Abrupt Climate Change Lamont Doherty Earth Observatory of Columbia University. 3 Mar Russell, Randy. "Transfer and Storage of Heat in the Oceans." Windows to the Universe. 6 June The Regents of the University of Michigan. 3 Mar