Warm-Up: 3/4-3/5 Name 4 properties of water that you remember from biology/ES.

Chapter 4 Water, Waves, and Tides

Key Concepts The polar nature of water accounts for many of its physical properties. Seawater contains a number of salts, the most abundant being sodium chloride. Salts are constantly being added to and removed from the oceans. The exchange of energy between oceans and the atmosphere produces winds that drive ocean currents and weather patterns.

Key Concepts The density of seawater is mainly determined by temperature and salinity. Vertical mixing of seawater carries oxygen to the deep and nutrients to the surface. Waves are the result of forces acting on the surface of the water. The gravitational pull of the moon and the sun on the oceans produces tides.

Table 4-1 Physical Properties of Water

Nature of Water Marine organisms are 70 – 80% water by mass. Terrestrial organisms are approximately 66% water by mass! Physical properties of water excellent solvent high boiling point and freezing point denser in its liquid form than in its solid form supports marine organisms through buoyancy provides a medium for chemical reactions necessary for life

Nature of Water Structure of a water molecule 2 H atoms bonded to 1 O atom polar - different parts of the molecule have different electrical charges the oxygen atom carries a slight negative charge the hydrogen atoms carry a slight positive charge

Nature of Water Freezing point and boiling point polar water molecules- Hydrogen bonds high boiling point reflects energy needed to overcome attractive forces of hydrogen bonds relative high freezing point (0oC) of water is a result of less energy needed to fix molecules into position to form solid

Figure 4-1 (b) Water Molecules.

Figure 4-1 (c) Water Molecules.

Nature of Water Water as a solvent polar nature keeps solute’s ions in solution water cannot dissolve non-polar molecules, e.g., oil and petroleum products

Figure 4-1 (d) Water Molecules.

(a) Polar nature of water molecule Hydrogen bond (b) Hydrogen bonding of water molecules due to its polarity Salt (c) Structure of water molecules in a solid state (ice) Stepped Art (d) Salt crystals dissolving in water Fig. 4-1, p. 70

Nature of Water Cohesion, adhesion, and capillary action hydrogen bonds cause water molecules to be cohesive, i.e., stick together, accounting for high surface tension adhesion - attraction of water to surfaces of objects that carry electrical charges, making them “wet” adhesion also accounts for water’s capillary action - the ability of water to rise in narrow spaces

Figure 4-3 Adhesion And Capillary Action.

Nature of Water Specific heat (Thermal capacity) Water and light water has a high specific heat (amount of heat energy needed to raise 1 g 1o C) due to hydrogen bonds ocean can maintain relatively constant temperature Water and light much light reflected into the atmosphere different wavelengths (colors) of light penetrate to different depths

Nature of Water Chemical properties of water acids release H+ atoms in water bases bind H ions and remove them from solution pH scale measures acidity/alkalinity pH of pure water is 7, considered neutral ocean’s pH is slightly alkaline (average 8) owing to bicarbonate and carbonate ions organisms’ internal and external pH affect life processes such as metabolism and growth

Increasing alkalinity pH paper Increasing acidity 1 2 3 4 5 6 Gastric juice Vinegar Urine Rain water Neutral Human saliva 7 Blood Increasing alkalinity 8 9 10 11 12 13 14 Egg white Seawater Great Salt Lake Liquid soap Oven cleaner Stepped Art pH scale Fig. 4-4, p. 72

Salt Water Composition of seawater most salts present in seawater are present in their ionic form 6 ions make up 99% of dissolved salts in the ocean: sodium (Na+) magnesium (Mg2+) calcium (Ca2+) potassium (K+) chloride (Cl-) sulfate (SO42-) trace elements - present in concentrations of less than 1 part per million

Table 4-2 Major Ions In Seawater.

Salt Water Salinity seawater = 3.5% salt, 96.5% water expressed as in g per kg water or parts per thousand (ppt) salinity of surface water varies as a result of evaporation, precipitation, freezing, thawing, and freshwater runoff from land between 10o N-10o S of equator = low salinity (due to heavy rainfall) areas around 30o N and 30o S = high salinity (evaporation > precipitation) from 50o = low salinity (heavy rainfall) poles = high salinity (freezing – removes water from sea)

Figure 4-5 Ocean Salinity.

Hydrogen sulfide (H2S) Chlorine (Cl2) Sulfur Chloride (Cl–) Precipitation Chloride (Cl–) Sulfate (SO42–) Hydrogen sulfide (H2S) Chlorine (Cl2) Volcano Sulfur Sea spray removes salts Salts removed when organisms are caught for food River discharge Carbonate (CO32–) Calcium (Ca2+) Sulfate (SO42–) Sodium (Na+) Magnesium (Mg2+) Calcium (Ca2+) Magnesium (Mg2+) Potassium (K+) Rock on the seafloor Clay particles adsorb Organisms die Bottom sediments Precipitation Stepped Art Fig. 4-6, p. 75

Salt Water Gases in seawater gases from biological processes oxygen is a by-product of photosynthesis release of CO2 from respiration oxygen-minimum zone – located just below sunlit surface waters solubility of gases in seawater seawater has more O and CO2 but less N than the atmosphere relative solubility in seawater: CO2 > O > N affected by temperature, salinity and pressure

Table 4-3 Gases Found in Seawater

Figure 4-7 (a) Gases In Seawater.

Salt Water role of bicarbonate as a buffer bicarbonate formed from the solution of CO2 buffer - a substance that can maintain the pH of a solution at a relatively constant point bicarbonate’s buffering action helps maintain the pH of seawater at a constant value, providing a stable environment for marine organisms

Figure 4-7 (b) Gases In Seawater.

Ocean Heating and Cooling Earth’s energy budget energy input sun’s radiant energy heats earth’s surface energy decreases with latitude (seasons) energy output Absorbed energy is released into atmosphere Greenhouse (CO2, Mthane) gasses trap energy

Greater angle Less solar energy per unit area Tropic of Cancer Right angle More solar energy per unit area Equator Tropic of Capricorn Greater angle Less solar energy per unit area Stepped Art Fig. 4-8, p. 77

Figure 4-9 The Earth’s Energy Budget.

Winds and Currents Winds result from horizontal air movements caused by temperature, density, etc. as air heats, its density decreases and it rises; as it cools, density increases and it falls toward earth wind patterns: upper air flow from the equator towards the north and south

Figure 4-11 North-South Air Flow.

Winds and Currents Winds Coriolis effect a point rotating at the equator moves faster than a point at a higher latitude path of air mass appears to curve relative to the earth’s surface—to the right in the Northern Hemisphere, left in the Southern

Figure 4-12 (a) The Coriolis Effect.

Figure 4-12 (b) The Coriolis Effect.

Winds and Currents Surface wind patterns 3 convection cells in each hemisphere: northeast & southeast trade winds westerlies polar easterlies areas of vertical air movement between wind belts Doldrums (at equator) horse latitudes (at 30o N & S)

Figure 4-12 (c) The Coriolis Effect.

Figure 4-13 Surface Wind Patterns.

Winds and Currents Ocean currents surface currents driven mainly by trade winds (easterlies and westerlies) in each hemisphere Coriolis effect currents deflected to the right of the prevailing wind direction in the Northern Hemisphere, to the left in the Southern Hemisphere deflection can be as much as 45-degree angle from wind direction gyres—water flow in a circular pattern around the edge of an ocean basin

Figure 4-14 (a) Gyres.

Figure 4-14 (b) Gyres.

Winds and Currents Classification of currents western-boundary currents: fastest, deepest currents that move warm water toward the poles in each gyre (e.g. Gulf Stream) eastern-boundary currents: slow moving, carry cold water toward the equator transverse currents: connect eastern- and western-boundary currents in each gyre biological impact western-boundary currents not productive, carry little nutrients, but increase oxygen mixed in water eastern-boundary currents productive, nutrient-rich

Figure 4-15 Major Ocean Currents.

Winds and Currents Currents below the surface energy transferred from winds to surface water is transferred to deeper water deeper-water currents are deflected by the Coriolis effect, down to about 100 m friction causes loss of energy, so each layer moves at an angle to and more slowly than the layer above, creating an Ekman spiral Ekman transport—net movement of water to the 100-m depth

Figure 4-16 Ekman Spiral.

Ocean Layers and Ocean Mixing Density—the mass of a substance in a given volume, usually measured in g/cm3 density of pure water = 1 g/cm3 density of salt water = 1.0270 g/cm3 Density increases when salinity increases Density increases when temperature decreases

Figure 4-17 Effect OF Temperature And Salinity On The Density Of Seawater.

Ocean Layers and Ocean Mixing Characteristics of ocean layers depth 0-100 m (330 feet): warmed by solar radiation, well mixed 100-1,000 m: temperature decreases thermocline – zone of rapid temperature change halocline: salinity increases 0-1,000 m pycnocline: 100-1,000 m, where changes in temperature and salinity create rapid increases in density seasonal thermoclines

Figure 4-18 (a) Changes In Temperature, Salinity, And Density Of Seawater With Depth.

Figure 4-18 (b) Changes In Temperature, Salinity, And Density Of Seawater With Depth.

Figure 4-18 (c) Changes In Temperature, Salinity, And Density Of Seawater With Depth.

Figure 4-19 Seasonal Changes And Vertical Mixing.

Water column stabilizes Fall Air temperature cools Surface water cools, displaces less dense water Colder denser water Summer Warm surface water Thermocline Isopycnal Wind Winter Water column unstable Spring Air temperature warms Surface water warms Colder denser water Thermocline Water column stable Storms drive surface water deeper Water column stabilizes Stepped Art Fig. 4-19, p. 86

Ocean Layers and Ocean Mixing Horizontal mixing higher density causes water at 30o N to form a curved layer that sinks below less-dense equatorial surface water and then rises to rejoin the surface at 30o S even denser water curves from 60o N to 60o S below other surface waters winter temperatures and increased salinity owing to freezing result in very dense water at the poles, which sinks toward the ocean floor

Ocean Layers and Ocean Mixing Vertical mixing vertical overturn results when denser water at the top of the water column sinks while less-dense water rises isopycnal—stable water column that has the same density from top to bottom vertical mixing allows water exchange between surface and deep waters nutrient-rich bottom water is exchanged for oxygen-rich surface water

Figure 4-20 Vertical Overturn.

Ocean Layers and Ocean Mixing Upwelling and downwelling equatorial upwelling water from currents on either side of the equator is deflected toward the poles, pulling surface water away to be replaced by deeper, nutrient-rich water coastal upwelling Ekman transport moves water offshore, to be replaced by deeper, nutrient-rich water coastal downwelling coastal winds force oxygen-rich surface waters downward and along the continental shelf

Figure 4-21 Upwelling And Downwelling Zones.

Ocean Layers and Ocean Mixing Deepwater circulation differences in density, not wind energy, cause water movement in deep oceans densest water of all is Antarctic Bottom Water, mostly formed in winter in the Weddell Sea dense Antarctic water sinks to the bottom and moves slowly toward the Arctic some North Atlantic Deep Water moves into the North Atlantic via a channel east of Greenland high-salinity Mediterranean Deep Water flows through the Strait of Gibraltar into the Atlantic Ocean

Waves Wave formation wave: a flow of energy or motion, not a flow of water generating force: a force that disturbs the water’s surface, e.g., wind, geological events, falling objects, ships restoring force: the force that causes the water to return to the undisturbed level surface tension for capillary waves gravity for gravity waves

Figure 4-22 Characteristics Of Waves.

Waves Types of waves Progressive (forced) waves are generated by wind and restored by gravity, progress in a particular direction forced waves are formed by storms, which determine their size and speed free waves, no longer affected by the generating force, move at speeds determined by the wave’s length and period swells are long-period, uniform free waves which carry considerable energy and can travel for thousands of km

Waves Types of Waves (con’t) deepwater and shallow-water waves deepwater waves—waves that occur in water that is deeper than ½ of a wave’s wavelength breakers deepwater waves become shallow-water waves when they move into shallow water surf zone—area along a coast where waves slow down, become steeper, break, and disappear breakers form when the wave’s bottom slows but its crest continues at a faster speed

Figure 4-23 Breakers.

Waves Types of Waves (con’t) Tsunamis (large seismic sea waves) seismic sea waves are formed by earthquakes tsunamis have long wavelengths, long periods and low height compression of the wave’s energy into a smaller volume upon approaching a coast pr island causes a dramatic increase in height

Figure 4-24 Tsunami.

Tides Tides: periodic changes in water level occurring along coastlines Why tides occur tides result from the gravitational pull of the moon and the sun though smaller, the moon is closer to earth, so its gravitational pull is greater water moves toward the moon, forming a bulge at the point directly under it the centrifugal force opposite the moon forms another bulge areas of low water form between bulges

Figure 4-25 Tides.

Tides Spring and neap tides during spring tides, the times of highest and lowest tides, the earth, moon and sun are in a line and act together creating highest and lowest tides when the sun and moon are at right angles, the sun’s pull offsets the moon’s, resulting in neap tides, which have the smallest change between high and low tide

Figure 4-26 Spring And Neap Tides.

Tides Tidal range diurnal tide: one high tide and one low tide each day semidiurnal tide: two high tides and two low tides each day (most common) mixed semidiurnal tide: high and low tides are at different levels flood tides are rising; ebb tides are falling tidal currents are associated with tidal cycle slack water occurs during the change of tides

Figure 4-27 (a, b & c) Tidal Patterns.

Figure 4-27 (d) Tidal Patterns.