Chapter 15 Oceanography Study of Earth’s oceans including the creatures that inhabit its waters, its physical and chemical properties, and the effects of humans activities.

Oceanography Vocabulary CREST – highest point of a wave. TROUGH- lowest point of a wave.

BREAKER – collapsing wave that forms when a wave reaches shallow water and is slowed by friction with ocean bottom. UPWELLING – upward movement of ocean water that occurs when winds push surface water aside and it is replaced with cold, deep water that originates on the ocean bottom.

TIDE – periodic rise and fall of sea level caused by the gravitational attraction among Earth, the Moon, and the Sun SEA LEVEL – level of the ocean’s surfaces, which is presently rising1 to 2mm per year due to the melting glaciers.

TEMPERATURE PROFILE – plots changing ocean water temperatures with depth, which varies depending on location and season. THERMOCLINE – Transitional ocean layer that lies between the relatively warm, sunlit layer and the colder, dense bottom layer and is characterized by temperatures that decrease rapidly with depth.

SURFACE CURRENT – wind driven movement of ocean water that primarily affects the upper few hundred meters of the ocean. SALINITY – measure of the amount of salts dissolved in seawater, which is 35 ppt on average or 3.5% DENSITY CURRENT – movement of ocean water that occurs in depths too great to be affected by surface winds and is generated by differences in water temperature and salinity.

What created Oceans? Two Hypothesis: Volcanoes & Comets After the earth’s formation, violent volcanism took place over million of years releasing Huge amounts of water vapor and gases. As the earth cooled, the water vapor condensed Into oceans. Comets contain 50% frozen water so the theory is that comets collided with the earth releasing enough water to fill the oceans. ( compared to dirty snowballs )

Distribution of Water 97% of water found in Oceans 3% is freshwater – 2 % ice caps of Greenland and Antarctica, the rest in groundwater, lakes, etc.

Blue Planet 71% of the surface of the Earth is covered by Oceans 71% of the surface of the Earth is covered by Oceans 61% Northern hemisphere covered by water 61% Northern hemisphere covered by water 81% Southern hemisphere covered by water 81% Southern hemisphere covered by water

5 Oceans Pacific – largest, half of Earth’s seawater Atlantic Indian Arctic Antarctic (also called The Southern Ocean) (Arctic & Antarctic covered with ice in the winter but breaks up in summer. Ice is less dense so it floats)

Chemical Properties The dissolved gases are oxygen, nitrogen, and carbon dioxide

Variations in Salinity Subtropics salinity is higher (37ppt) – evaporation rates are higher than precipitation Polar regions (32ppt) – diluted by melting ice Lowest salinity is where large rivers empty into the oceans.

How did Oceans get salty? Volcanic gases (CL, water vapor and SO 2 ) dissolve in water and form the chlorine and sulfate ions of seawater (salt) Weathering of crustal rocks adds in the sodium, calcium, & potassium. These ions flush into the river system and are transported into the oceans)

Removal of Sea salts Precipitate Droplets are picked up by wind and deposited inland Marine organisms remove ions to build their shells, bones, and teeth. When they die their parts accumulate on the seafloor.

Physical Properties Seawater is denser then Freshwater (1.00g/cm3) and will vary on levels of salinity Seawater is denser then Freshwater (1.00g/cm3) and will vary on levels of salinity Temperature – cold water is denser than warm water Temperature – cold water is denser than warm water Water absorbs light Water absorbs light – Penetrates upper 100m, below that it is dark

Ocean Layering – due to density differences Temperature ranges -2 degrees Celsius to 30 degrees Celcius, average 15 degrees Celcius Decline with depth 3 layers – density differences 1.Surface layer - warm, sunlit, 100m 2.Thermocline – rapidly decreasing temp w/depth 3.Bottom layer - Cold and dark, freezing

Deep Water Masses The bottom layer of the ocean is near freezing even at the equator. The Gulf Stream carries salt into the North Atlantic where the water cools. The cooling and the added salt cause the waters to sink in the Norwegian Sea. This is the formation of Atlantic Deep Water.  Antarctic Intermediate Water  North Atlantic Deep Water  Antarctic Bottom Water

In a wave, water moves in a circular pattern that decreases in size with depth. Only the energy moves forward. Only the energy moves forward.

Tides Periodic rise and fall of sea level 2 High Tides/day – highest level to which water rises 2 Low Tides/day – lowest level Tidal range – difference between high tide and low tide Cycles - 24 hours and 50 minutes

Cause of Tides Gravitational Attraction with the earth, moon, and sun Gravitational Attraction with the earth, moon, and sun Bulges are aligned with the moon tides Bulges are aligned with the moon tides tides

Sun’s Influence on Tides Sun’s influence is smaller than that of the moon Spring tides – large tidal ranges; moon is either full or new High tides are higher, low tides are lower Neap tides – small tidal ranges; first and quarter moon High tides are lower, low tides are higher

Gyres Continents deflect ocean currents to the north and south so that closed circular current systems develop. North Pacific, North Atlantic, South Pacific, South Atlantic, Indian Ocean Due to the Coriolis effect the gyres move: Counterclockwise in Southern Hemisphere Clockwise in Northern Hemisphere

Gyres can have numerous currents within them Ocean Currents Gyres