Chapter 4 Unit Objectives: Unit Objectives cont: Nature of Water ...
11/9/11
Unit Objectives: Chapter 4 Water, Waves, and Tides
Unit Objectives cont: • Explain the relationship between density, temperature, and salinity. • Understand the movement of oxygen and nutrients through the water column.
• Explain how the polar nature of water accounts for many of its physical properties. • Understand that salts are constantly being added to and removed from the oceans. • Explain the relationship between the ocean and the atmosphere and global weather patterns.
Nature of Water • 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
1
11/9/11
Nature of Water • Freezing point and boiling point – hydrogen bonds—weak attractive forces between slightly positive H atoms of one molecule and slightly negative O ends of nearby molecules – responsible for low freezing/high boiling points
Nature of Water • Water as a solvent – polar nature keeps solute’s ions in solution – water cannot dissolve non-polar molecules
Nature of Water • Cohesion, adhesion, and capillary action – cohesive H bonds = high surface tension – adhesion—attraction of water to surfaces of objects that carry electrical charges, which allows it to make things wet – capillary action—the ability of water to rise in narrow spaces, owing to adhesion
2
11/9/11
Nature of Water • Specific heat – Heat is a measure of molecular motion – water has a high specific heat – ocean can maintain relatively constant temperature
• Latent Heat of Fusion – Amount of energy needed to change water from a solid to a liquid (takes 80 cal to convert 1g at 0o C) – Allows oceans to cool gradually In winter
Nature of Water • Evaporation – Releases heat and water vapor into the atmosphere – H bonds are broken enabling molecules to escape
• Latent Heat of Vaporization – The amount of heat lost during evaporation. (considerably greater amount of heat loss than latent heat of fusion) 540 cal/g evaporated sea water at 0o C
Electromagnetic Spectrum of Sunlight
Nature of Water • Water and light – much light reflected into the atmosphere – different wavelengths (colors) of light penetrate to different depths – About 65% of total light is absorbed within a depth of 1m
Nature of Water • Chemical properties of water
http://www.whoi.edu/oceanus/viewFlash.do? fileid=2323&id=2371&aid=2472
– acids release H+ atoms in water – bases bind H ions and remove them from solution – pH scale measures acidity/alkalinity – 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
3
11/9/11
Salt Water • Composition of seawater – 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
Salt Water • Salinity – seawater = 3.5% salt, 96.5% water – expressed as in g per liter water or parts per thousand
Ways to measure salinity
Salt Water • Salinity continued…
Salinometer:
electrically measures the conductivity of water
Refractometer:
refraction of light through a prism
– salinity of surface water varies as a result of evaporation, precipitation, freezing, thawing, and freshwater runoff from land – 10o N-10o S = low salinity (heavy rainfall) – areas around 30o N and 30o S = high salinity (evaporation) – 50o N and 50o S - low salinity (heavy rainfall) – poles = high salinity (freezing)
4
11/9/11
Salt Water • Cycling of sea salts – sea salt originally from earth’s crust – ocean composition has remained the same owing to balance between addition through runoff and removal – salts removed in many ways: • sinking or depositing on land by sea spray • evaporites • concentration in tissues of organisms harvested for food • adsorption—process of ions sticking to surface of fine particles, which sink into sediments
Salt Water • Gases in seawater – gases from biological processes • oxygen is a by-product of photosynthesis • most organisms use O, release CO2 • just below sunlit surface waters is the oxygenminimum zone (500 to 1000 meters)
– solubility of gases in seawater • seawater has more O and CO2 but less N than the atmosphere • solubility: CO2 > O > N • affected by temperature, salinity and pressure
5
11/9/11
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 a stable environment for marine organisms
Ocean Heating and Cooling • Earth’s energy budget – energy input • sun’s radiant energy heats earth’s surface • spherical shape + presence of the atmosphere cause the amount of radiant energy reaching earth’s surface to decrease with increasing latitude
Ocean Heating and Cooling • Earth’s energy budget – energy output • excess energy absorbed by the earth is transferred to the atmosphere by evaporation and radiation • accumulation of greenhouse gases can prevent heat energy from radiating back to space
Ocean Heating and Cooling • Sea temperature – daily • affected by: – energy absorption at the surface – loss by evaporation – transfer by currents – warming/cooling of atmosphere – heat loss through radiation
– seasonally • variations in the amount of solar radiation reaching the earth, especially between 40o and 60o N and S
6
11/9/11
Winds and Currents • Winds – result of horizontal air movements caused by temperature, density, etc. – wind patterns: upper air flow from the equator towards the north and south
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 – http://www.classzone.com/books/earth_science/terc/content/ visualizations/es1904/es1904page01.cfm?chapter_no=visualization
– http://www.wiley.com/college/strahler/0471480533/animations/ ch07_animations/animation2.html – http://www.teachersdomain.org/resources/ess05/sci/ess/watcyc/ oceancur/index.html
Winds and Currents – surface wind patterns • 3 convection cells in each hemisphere • winds are designated by the direction from which they are coming – northeast trade winds – southeast trade winds – westerlies – polar easterlies
• areas of vertical air movement between wind belts – doldrums – horse latitudes
7
11/9/11
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
• gyres—water flow in a circular pattern around the edge of an ocean basin
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—carry cold water toward the equator • transverse currents—connect eastern- and western-boundary currents in each gyre – biological impact » western-boundary currents not productive and carry little nutrients » eastern-boundary currents productive, nutrientrich
8
11/9/11
Ocean Layers and Ocean Mixing • Density—the mass of a substance in a given volume, usually in g/cm3 – pure water’s density = 1 g/cm3 – salt water’s density = 1.0270 g/cm3
• Density increases when salinity increases • Density increases when temperature decreases
9
11/9/11
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
Ocean Layers and Ocean Mixing • Deepwater circulation – differences in density, not wind energy, cause water movement – densest water of all is Antarctic Bottom Water, mostly formed in winter in the Weddell Sea – dense Antarctic water sinks to the bottom and creeps very 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
10
Unit Objectives: Chapter 4 Water, Waves, and Tides
Unit Objectives cont: • Explain the relationship between density, temperature, and salinity. • Understand the movement of oxygen and nutrients through the water column.
• Explain how the polar nature of water accounts for many of its physical properties. • Understand that salts are constantly being added to and removed from the oceans. • Explain the relationship between the ocean and the atmosphere and global weather patterns.
Nature of Water • 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
1
11/9/11
Nature of Water • Freezing point and boiling point – hydrogen bonds—weak attractive forces between slightly positive H atoms of one molecule and slightly negative O ends of nearby molecules – responsible for low freezing/high boiling points
Nature of Water • Water as a solvent – polar nature keeps solute’s ions in solution – water cannot dissolve non-polar molecules
Nature of Water • Cohesion, adhesion, and capillary action – cohesive H bonds = high surface tension – adhesion—attraction of water to surfaces of objects that carry electrical charges, which allows it to make things wet – capillary action—the ability of water to rise in narrow spaces, owing to adhesion
2
11/9/11
Nature of Water • Specific heat – Heat is a measure of molecular motion – water has a high specific heat – ocean can maintain relatively constant temperature
• Latent Heat of Fusion – Amount of energy needed to change water from a solid to a liquid (takes 80 cal to convert 1g at 0o C) – Allows oceans to cool gradually In winter
Nature of Water • Evaporation – Releases heat and water vapor into the atmosphere – H bonds are broken enabling molecules to escape
• Latent Heat of Vaporization – The amount of heat lost during evaporation. (considerably greater amount of heat loss than latent heat of fusion) 540 cal/g evaporated sea water at 0o C
Electromagnetic Spectrum of Sunlight
Nature of Water • Water and light – much light reflected into the atmosphere – different wavelengths (colors) of light penetrate to different depths – About 65% of total light is absorbed within a depth of 1m
Nature of Water • Chemical properties of water
http://www.whoi.edu/oceanus/viewFlash.do? fileid=2323&id=2371&aid=2472
– acids release H+ atoms in water – bases bind H ions and remove them from solution – pH scale measures acidity/alkalinity – 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
3
11/9/11
Salt Water • Composition of seawater – 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
Salt Water • Salinity – seawater = 3.5% salt, 96.5% water – expressed as in g per liter water or parts per thousand
Ways to measure salinity
Salt Water • Salinity continued…
Salinometer:
electrically measures the conductivity of water
Refractometer:
refraction of light through a prism
– salinity of surface water varies as a result of evaporation, precipitation, freezing, thawing, and freshwater runoff from land – 10o N-10o S = low salinity (heavy rainfall) – areas around 30o N and 30o S = high salinity (evaporation) – 50o N and 50o S - low salinity (heavy rainfall) – poles = high salinity (freezing)
4
11/9/11
Salt Water • Cycling of sea salts – sea salt originally from earth’s crust – ocean composition has remained the same owing to balance between addition through runoff and removal – salts removed in many ways: • sinking or depositing on land by sea spray • evaporites • concentration in tissues of organisms harvested for food • adsorption—process of ions sticking to surface of fine particles, which sink into sediments
Salt Water • Gases in seawater – gases from biological processes • oxygen is a by-product of photosynthesis • most organisms use O, release CO2 • just below sunlit surface waters is the oxygenminimum zone (500 to 1000 meters)
– solubility of gases in seawater • seawater has more O and CO2 but less N than the atmosphere • solubility: CO2 > O > N • affected by temperature, salinity and pressure
5
11/9/11
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 a stable environment for marine organisms
Ocean Heating and Cooling • Earth’s energy budget – energy input • sun’s radiant energy heats earth’s surface • spherical shape + presence of the atmosphere cause the amount of radiant energy reaching earth’s surface to decrease with increasing latitude
Ocean Heating and Cooling • Earth’s energy budget – energy output • excess energy absorbed by the earth is transferred to the atmosphere by evaporation and radiation • accumulation of greenhouse gases can prevent heat energy from radiating back to space
Ocean Heating and Cooling • Sea temperature – daily • affected by: – energy absorption at the surface – loss by evaporation – transfer by currents – warming/cooling of atmosphere – heat loss through radiation
– seasonally • variations in the amount of solar radiation reaching the earth, especially between 40o and 60o N and S
6
11/9/11
Winds and Currents • Winds – result of horizontal air movements caused by temperature, density, etc. – wind patterns: upper air flow from the equator towards the north and south
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 – http://www.classzone.com/books/earth_science/terc/content/ visualizations/es1904/es1904page01.cfm?chapter_no=visualization
– http://www.wiley.com/college/strahler/0471480533/animations/ ch07_animations/animation2.html – http://www.teachersdomain.org/resources/ess05/sci/ess/watcyc/ oceancur/index.html
Winds and Currents – surface wind patterns • 3 convection cells in each hemisphere • winds are designated by the direction from which they are coming – northeast trade winds – southeast trade winds – westerlies – polar easterlies
• areas of vertical air movement between wind belts – doldrums – horse latitudes
7
11/9/11
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
• gyres—water flow in a circular pattern around the edge of an ocean basin
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—carry cold water toward the equator • transverse currents—connect eastern- and western-boundary currents in each gyre – biological impact » western-boundary currents not productive and carry little nutrients » eastern-boundary currents productive, nutrientrich
8
11/9/11
Ocean Layers and Ocean Mixing • Density—the mass of a substance in a given volume, usually in g/cm3 – pure water’s density = 1 g/cm3 – salt water’s density = 1.0270 g/cm3
• Density increases when salinity increases • Density increases when temperature decreases
9
11/9/11
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
Ocean Layers and Ocean Mixing • Deepwater circulation – differences in density, not wind energy, cause water movement – densest water of all is Antarctic Bottom Water, mostly formed in winter in the Weddell Sea – dense Antarctic water sinks to the bottom and creeps very 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
10
