Notes: Tides
Tides occur due to the interaction of Earth, moon and sun.
Gravity is the force that causes the tides to occur on the Earth’s surface.
Gravity is the attraction of 1 body (mass) for another.
Tidal bulges (high tide) occur on the side of the Earth facing the moon. The water is pulled toward the moon. On the side of the Earth opposite the moon, a bulge occurs due to the water left behind. Between the budges is low tide. As the Earth rotates, different places on the Earth’s surface pass through areas of tidal bulges.
Daily Tidal cycles-high tides occur 12 hours and 25 minutes apart. The farther west you travel, the later the high tides along a coastline. The height of tides depends on landforms such as capes, peninsulas, and islands.
Monthly tidal cycles-changes in the Earth, moon and sun affect the height of tides.
Spring tides (Old English “springen” meaning to jump) Occur twice a month, at new moon and full moon when the Earth, moon, and sun line up. Spring tides show the greatest difference between high and low tide.
Neap tides occur at the 1st and 3rd quarters of the moon when the moon is at a right angle to the sun. Neap tides show the least difference between high and low tides.
Energy from Tides
A few places on Earth (must be at least 4 to 5 meters difference in the tides) are positioned so that tides coming in are trapped by gates. Water escapes through tunnels by gravity back to the ocean. As it flows back it drives turbines which produce electricity.
Water Chemistry
Salinity- the total amount of dissolved salts in the water. (desalination-removal of salt from water)
Concentration- the amount of 1 substance dissolved in a volume of another substance.
NaCl concentration range is 34ppt-37ppt.
Dissolved Salts in Ocean Salinity varies by depth. It increases with depth.
30.6% sodium (Na) Rain, snow, etc make more fresh at surface.
55.0% chlorine (Cl) Mouths of rivers are more fresh.
7.7% sulfate (SO4) Climate dictates salinity, ex Red Sea, a hot, dry
3.7% magnesium (Mg) climate promotes evaporation of water, so more
1.2% calcium (Ca) salty. At the poles, salt is left behind when water
1.1% potassium (K) freezes, so water is more salty.
0.7% other (P, N)