CEE 1030 1nd Edition Lecture 21 Oceans Outline of Last Lecture I Land sea boundary II Waves III Shore zones IV Wave erosion V Beaches VI Coastal features VII Wave refraction VIII Shoreline stabilization Outline of Current Lecture I Salinity II Movement of ocean water III Ocean zones IV Seawater density V Tidal currents VI Review Current Lecture I II Salinity a Salinity the concentration of dissolved salts in seawater b Ocean water has an average salinity of 3 5 c Sodium is leached out of seafloor sediments d Chloride from outgassing of underwater volcanoes e Salts leached out of terrestrial sediments by rainfall and carried to sea by runoff and groundwater f Variations in salinity i Less saline where freshwater runoff mixes with seawater ii More saline in areas with high evaporation and low precipitation and inflow Movement of ocean water a World ocean the interconnected saltwater surrounding continents and filling Earth s deepest basins b Ocean current any more or less continuous directed movement of ocean water c Forces Earth s rotation wind temperature and salinity differences d Influences shape of ocean basin seafloor topography shoreline shape etc These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute III IV V e Water at different depths often moves in different directions affected by different forces f Oceanography i Surface waters are mixed and moved by the wind tides cause differences in density ii Most deep ocean currents are driven by density differences in water Coriolis effect Ocean zones a Mixed layer surface zone of ocean warmed by the sun and mixed by wind and waves b Pycnocline the transition zone of abrupt vertical density change i Density gradient caused by difference in water temperature or salinity c Pelagic zone all open ocean not near coast or seafloor d Benthic zone water near to the coast or sea floor Seawater density a Density the mass of water per unit volume b Saltwater is denser than freshwater c Cold water is denser than warm water d Thermohaline Circulation i Deep ocean currents are driven by density differences e Downwelling water sinks because of converging currents or because surface water is denser than deep water f Upwelling deep water rises because it is less dense than surface waters or pulled up to replace surface water driven away by winds i Marked by extremely cold water temperatures and high nutrient content ii Along western coasts of continents where equatorial winds drive surface waters away Tidal currents a Gravitational pull of the moon and the sun cause alternating horizontal movement of surface water b Types i Flood current movement of water toward the shore ii Ebb current movement of water away from the shore c Daily tides i Moon s gravitational pull causes oceans to bulge simultaneously on moon s nearside and farside ii Moon s direct gravitational pull causes oceans to bulge on Earth s nearside iii Gravity decreases with distance so moon s gravitational pull is stronger on Earth s nearside iv Stretches the planet very slightly resulting in a tidal bulge on Earth s farside VI d Causes of tides i Earth rotates on its axis more rapidly than the moon s position changes ii Tidal bulges stay in place while the planet rotates through them iii Most coasts experience two high tides and two low tides each day e Tidal cycles i Spring tides highest of tidal range near time of new and full moons when gravitational forces of the moon and sun are added together ii Neap tides lowest tidal range occurs near times of first and third quarters of the moon when gravitational forces of the moon and sun are offset f Tides are influenced by the shape of a coastline topography of the ocean floor and other currents g Whirlpool swirling water produced where opposing currents meet often caused by tides h Maelstrom particularly powerful whirlpool i Eddy circular current at the ocean surface larger than a whirlpool j Gyre rotational circulation forms in ocean basins centered on subtropical highpressure region Review a Earth s rotation on its axis will cause a current going from the North Pole to the equator to be deflected west b The gyre in the South Pacific Ocean rotates counter clockwise c The greatest force driving tides in the ocean is the gravitational pull of the moon