OCE1001 Study Guide LECTURE 18 Air Sea Interaction Modern Oceanography 03 30 2015 How do satellites measure sea surface displacement o By detecting a signal 1 2in from a platform as much as 1000km 600 miles away Rings Eddies Dramatic examples of ocean storms speed 1 2 m s El Nino Global short term climate anomaly centered in the Pacific Effects precipitation wildlife population temperatures Increased Societal problems caused by DROUGHT FLOODING and collapse of Move water biota salt heat Long Lived up to 3 years forest fires in Indonesia food based industries Impact on Peru o Anchovy fishery lost over 90 of its catch HOT WATER COLD WATER SHIFT DEPRESSES THERMOCLINE UPWELLING NO LONGER BRINGS UP NUTRIENTS FOOD CHAIN COLLAPSES o Sea bird population plummeted guano production fell off o Flooding Impact on Philippines o Drought conditions led to collapse of coconut industry Coconut prices increase ENSO El Nino Southern Oscillation o Oceanographic part of a coupled ocean atmosphere perturbation LECTURE 19 Tides What causes Tides o Combination of gravity of Moon Sun o Orbital Motion o If Earth had no continents and a deep ocean of uniform depth there would be two bulges of high tide one on each side Why two Because Orbits are mutual Mutual Orbits The moon and the earth orbit around a common point called the barycenter The Barycenter is closer to Earth s center because the Earth is more massive A Gravitational Force of Moon Zenith Gravity is stronger closer to the moon Nadir Gravity is weaker farther from the moon B Force required to maintain orbit Centripetal center seeking Force Required to keep orbit stable is also constant C Difference Creates Tides The moons gravity is no equal to the force required for orbit at most Resultant Force The difference between moon s gravity force points on earth required for orbit Moon s gravity and force required for orbit balance each other so the orbit remains stable AT INDIVIDUAL POINTS THEY CREATE TIDES Bulge On each side Tide generating forces Components of the resultant force PARALLEL to earth s surface o Pushes water toward the ZENITH creates a TIDAL BULGE on each side Tides from the Sun Moon Tidal bulge from Moon is bigger than bulge created by the Sun Interact to produce different tide strengths FULL NEW MOON Syzygy Sun earth and moon are aligned Tidal bulges add up STRONGER CYCLE QUARTER MOON Quadrature Sun earth and moon at right angles Tidal bulges partially cancel Weaker cycle The earth is titled this means the sun and moon are not directly above the equator Angle of tilt declination Earth s axis of rotation tilts 23 5 degrees from perpendicular to the plan of the ecliptic Moon s orbit tilts 5 degrees from the plane of the ecliptic Plane of Ecliptic Where the Earth and most other planets orbit Sun Orbits are elliptical Tides are stronger when Earth is closer to moon sun Tides CANNOT keep up with Earth s rotation Tides are shallow and longer than the ocean is deep Tides are slowed by friction and blocked by continents o Tidal Bulges don t literally exist instead broken into smaller cells AMPHIDROMIC POINT tide waves rotate counterclockwise in the North Hemisphere and clockwise in the South Hemisphere in each cell Effects of Continents Two main factors that influence tides Coastline Shape and Offshore depth Shallower waters amplify tides TIDAL PATTERNS DIURNAL COMMON IN SHALLOW INLAND MARGINAL SEAS GULF SEMIDIURNAL COMMON ALONG ATLANTIC COAST OF NORTH MIXED THE MOST COMMON TIDAL PATTERN Coastal Tidal Currents Rotary move in circle in a tidal cell in the open ocean little OF MEX AMERICA friction o Where there is friction these produce REVERSING CURRENTS Flood current water rushes into a bay river estuary before high tide Ebb current Water rushes out before low tide Tides as a Renewable Energy Source Dams with turbines Underwater windmills Disadvantages only run a few times a day disturb wildlife LECTURE 20 Waves and Tides Waves Periodic time dependent motion of fluid characterized by a wavelength and an amplitude o Wavelength o Amplitude Progressive Waves Waves move away from generating source Period of the wave time from trough to trough Phase speed Speed of trough wavelength period crest o Causes winds storms Peak trough Rip Currents Surf Zone Dynamics Waves incident on a beach transport mass toward beach As surface waves move into shallower water their wavelength decreases amplitude increases o Energy transport is constant Tsunami Tidal Wave Extremely long wavelength wave generates by marine earthquakes Tsunamis can combine with refraction to attack an island LECTURE 21 Life On Earth 4 5 BYA Planet Formed 4 2 BYA Earliest non metamorphised rocks Evidence of Early Life Prokaryotes Bacteria archea Result of Prokaryote colonies Eukaryotes found after about 2 4BY Multicellular w organelles Modern communities respire with oxygen Anoxic pathways are not Issues greatly efficient Vents seldom last more than a few decades dispersal Riftia females release fertilized eggs after some development Vent Bacteria Prokaryotes Chemical structural similarity Great Oxygenation Event All iron rusted Free oxygen toxic to anaerobes Great extinction event Methane reduced iClicker Question Prokaryotes and Eukaryoes were the dominant life forms on Earth for A 3 Billion years B 300 Million years C 30 Million years Quiz will cover Homework s 10 11 03 30 2015 03 30 2015
View Full Document
Unlocking...