Unit 4- Physical Oceanography

Currents Ocean current- mass of ocean water that flows from one place to another Two types Surface/wind-driven Deep/density-driven

Coriolis Effect Coriolis Effect- a “deflection” of a moving object due to the fact that the Earth is rotating Moving object travels in straight line from outside reference, but Earth has moved underneath, so object appears to move in a curved path Objects are deflected to the RIGHT in the Northern Hemisphere and to the LEFT in the Southern Hemisphere No effect at the Equator and maximum effect at the poles

http://www.youtube.com/watch?v=mcPs_OdQOYU

Global Winds Winds named based on where they are coming from Northern Hemisphere winds: Polar Easteries Prevailing Westerlies NE Trade Winds Southern Hemisphere winds: Polar Easterlies SE Trade Winds

Waves Three main causes of ocean waves 1. Wind* 2. Tides 3. Seismic Activity (earthquakes, volcanoes) http://www.youtube.com/watch?v=dv_Sis0Hntk&feature=player_embedded http://www.youtube.com/watch?feature=player_embedded&v=aXuQC1qRuEM

Waves Other factors affecting wave height Distance from shoreline Latitude Water depth Nearby landmasses

Wave Energy http://www.youtube.com/watch?v=7k5r89IseEM

Tides Definition – low, earth-wide waves that cause regular rise/fall in sea level Take place every 12 hours and 25 minutes; therefore, they are predictable Vary in height (from 1-20 meters)

http://www.youtube.com/watch?v=6IyRE9azhwQ&feature=player_embedded#!

Causes of Tides 1. Gravity Moon pulls water towards it, creates bulge on moon side of earth Sun- same thing, but only about 1/3 – 1/2 the effect; responsible for extra high tides

Causes of Tides 2. Inertia (centripetal force) Things want to keep moving in straight line “Counteracts” the force of gravity from moon Causes opposite bulge on far side of earth

Two high tides & two low tides per day Time of high/low tide depends on the lunar cycle

Types of Tides Flood- when tide is coming in (change from a low to high tide) Ebb- when tide is going out (change from a high to low tide) http://oceanservice.noaa.gov/education/tutorial_tides/media/supp_tide01.html

Types of Tides Spring- very strong tides, due to alignment of Earth, sun, and moon (straight line) Neap- very weak tides, due to alignment of Earth, sun, and moon at 90° angle (effects cancel) http://oceanservice.noaa.gov/education/tutorial_tides/media/supp_tide06a.html

When would spring tides occur? When would neap tides occur? Lunar Cycle- 29.5 days When would spring tides occur? When would neap tides occur?

Lunar Cycle & Tides Spring tides- new moon and full moon Neap tides- 1st quarter moon and 3rd quarter moon Spring & Neap occur once every 14 days http://stardate.org/nightsky/moon

http://oceanservice. noaa http://oceanservice.noaa.gov/education/tutorial_tides/media/supp_tide05.html

Tidal Bore Tidal bore occurs when a river runs backwards due to incoming tide and land formation around it

Importance of Tides Mix shallow waters Move floating organisms into/from breeding areas Fisheries, ships, recreation

http://bayoffundy.com/about/highest-tides/

Tsunamis Tsunami- underwater seismic activity that transfers lots of energy into a water column Ex.- Earthquakes, volcanoes, avalanches Drawback- trough of wave reaches shore before the crest, so water along the shoreline recedes dramatically Waves slow down as they reach the shore, increasing in height http://upload.wikimedia.org/wikipedia/commons/2/2d/Propagation_du_tsunami_en_profondeur_variable.gif

Tsunamis: Coastal Impacts Not a huge breaking wave, rather a strong flood Extreme destruction Marine life washed ashore Often injuries and casualties

http://www.youtube.com/watch?v=BsRd7WQuBHc

http://www.pbs.org/teachers/connect/resources/6723/preview/

ENSO Cycle ENSO (stands for El Niño/ Southern Oscillation) Cycle: Year-to-year variations in temperature, rainfall, air pressure, circulation, etc. Occurs in the equatorial Pacific Highly irregular pattern The cycle can last anywhere from 2-10 years

El Niño Refers to the above average sea-surface temperatures that periodically develop across the east-central equatorial Pacific Represents the warm phase of the ENSO cycle Cause: equatorial easterly trade winds diminish, resulting in an eastward shift of the Pacific warm pool

How El Niño Affects Global Climate Warmer winters across the northern U.S. Gulf states cooler and wetter Increases storms on the west coast of North & South Americas Fisheries disrupted Can cause a drought in Indonesia and western Pacific

La Niña Periodic cooling of sea-surface temperatures East-central equatorial Pacific Represents the cold phase of the ENSO cycle Equatorial easterly trade winds strengthen

How La Niña Affects Global Climate La Niña has equally dramatic, often opposite effects of El Niño Could increase the number of Atlantic hurricanes Where there was drought, now turns to flooding; flooding turns to drought Abnormally mild winter now turn to abnormally harsh winter

2011 La Niña Major snowfall Extreme flooding/high river levels Severe drought in Southwest Joplin/Tuscaloosa tornados Warmer temperatures in the fall

Tropical Cyclone Huge rotating masses of low pressure Generate strong winds and torrential rain Called hurricanes in North and South America Called typhoons in Pacific Called cyclones in Indian Ocean

Hurricane Conditions Warm ocean water Warm moist air Coriolis Effect- causes hurricanes to spin Found during late summer and early fall Hurricane season: June 1- November 30

Hurricane Movement Driven by trade winds Move east to west across oceans Eye of the hurricane- winds are drawn upward, so horizontal wind speeds are low= usually calm Composed of spiral rain bands that create intense rainfall Movement over land cuts off energy source

Hurricane Destruction Caused by high winds and flooding from intense rainfall Storm surge- extremely high winds cause water to pile up higher than normal sea level Main cause of destruction

Tropical Cyclone Destruction Deadliest Storm: Great Bhola Cyclone- 1970, Bangladesh killed 500,000 people Top 30 deadliest tropical storms all occurred in Indian Ocean or western Pacific near China

U.S. Hurricanes Deadliest: Most damaging: 1. Galveston Hurricane- 1900 in Galveston, TX killed over 6,000 people Deadliest natural disaster in US history 3. Hurricane Katrina- 1000 deaths Most damaging: Hurricane Katrina- 2005, caused over $100 billion in damage Hurricane Sandy- 2012, caused $50 billion in damage

http://www.youtube.com/watch?v=YeutC1WN6dc