Earth’s Oceans – “The Water Planet” Unit 6 Chapters 22 - 24 Why does the Earth look mostly blue when viewed from space? Oceanography • Oceanography – is the study of the ocean using chemistry, biology, physics, geology, and other sciences. Water Molecule • Water molecule (H20) = 1 Oxygen, 2 Hydrogens • Polarity – uneven distribution of charge between H & O – Hydrogen is positive charge and Oxygen is negative charge = Dipolar molecule • H bonding - strong bond between a positively charged H atom of one molecule with a negatively charged atom of another molecule. – Hydrogen bonds determine the structure of water in solid form. _ – Arrange in “frame” with large spaces O H H + between molecules + (less dense, like ice) _ O H H + + Properties of Water • Oceans cover >70% of Earth’s surface • Density – – Salinity and Temperature affect density of seawater – Ice (solid form of water) is less dense than the liquid form because of the structure • Ice floats on water. – Salt concentration – the more salt the more dense the water is. • (Dead Sea – people float on water http://www.trekearth.com/gallery/Middle_East/Israel/Southern/ because salt water is Beer_Sheva/Dead_Sea/photo1019336.htm more dense). Seawater • Salinity – measure of dissolved salts in water. – Measure by evaporating water Freshwater freezes, leaves and weighing amount of salt salt behind in seawater. left over. – Average salinity = 35 practical salinity units (psu) or 35%. – Based on amount of fresh water entering sea. (so salinity may be different at times – also depends on climate) • Seawater liquid between -2ºC to 100.3ºC (normally water http://tvl1.geo.uc.edu/ice/Image/pretty/467-4.html is a liquid between 0ºC - 100ºC – Throw salt on sidewalk/road to melt ice. (seawater more stable than pure water) Salinity in Seawater can change • Depends on amount of freshwater coming into sea – So area with lots of freshwater coming into sea may be less than the average 35% salinity (because less salt, more freshwater) • Depends on climate – So area with hot, dry climates will evaporate water more quickly, so salinity is more than average (less freshwater, leaves more salt) – Area very cold forming ice, salt is left behind in water and freshwater freezes, so salinity would be higher here. Composition of Seawater Piles of salt, Bolivia • More than 70 elements make up seawater – Chloride ~55% – Sodium ~30.6% – Sulfate ~7.7% – Magnesium ~3.7% – All others ~3% • Important elements in seawater: http://en.wikipedia.org/wiki/File:Piles_of_Salt_Salar_de_Uyuni_Bolivia_ – Salt (Sodium Chloride= Luca_Galuzzi_2006_a.jpg NaCl) and magnesium •Salts enter ocean via: mined from seawater. - Underwater volcanoes – Calcium for hard shells (shellfish) - Erode from mineral- – Nitrogen and phosphorous rich rocks from photosynthesis. - Decomposed marine organisms. Temperature Profile of Ocean • 3 temperature zones: – Surface zone/Mixed Layer (warmed by sunlight) – Middle zone/ Thermocline (penetrated by little light, temperatures change rapidly) – Deep zone (very cold, without light) http://files.myopera.com/nielsol/blog/Thermocline_2.jpg Temperature Profile of Ocean • Surface zone/Mixed Layer – wind and waves mix heat evenly, absorbs sun’s light, home to millions of photosynthetic organisms and home to most marine life. (between 50 – 300 meters deep). • Middle zone/Thermocline – temperatures drop rapidly. (down to 1000 meters deep). • Deep water zone – cold at all depths, cold water is denser so sinks to bottom and moves http://alex.state.al.us/uploads/23942/thermocline.gif away from polar region. Ocean Life • Phytoplankton – single- celled protists, near the surface of the ocean (photosynthesis organism), base of ocean’s food chain. – Diatom – (thin shell of silica) http://www.astrographics.com/GalleryPrints/Display/GP2131.jpg • Large population can change color of water = algal bloom. • Zooplankton – microscopic animals that drift in ocean and eat phytoplankton. http://drake.marin.k12.ca.us/stuwork/rockwater/PLANKTON/zoodrawings.gif Ocean Life • Coral – sea animal fastened to rocky sea floor. • Lives in water with temperatures between 18ºC to 21ºC and generally up to 90 meters in depth (where sunlight reaches), ocean http://www.chbr.noaa.gov/categories/raim/images/coral_01.jpg currents bring their food. • Nekton – free swimming organisms (fish, reptiles, whales, squid, & jellyfish) http://biology.unm.edu/ccouncil/Biology_203/Images/Protostomes/squid.jpg Deep Ocean Life • Carbon dioxide accumulates in deep because no organisms to convert to oxygen (sunlight doesn’t reach here). Black smoker • Ocean vents provide habitat for deep water animals. • ocean floor vents: (Cold ocean water seeps through floor cracks, then its heated by hot rocks in crust) – Cracks in ocean floor release hot water (16ºC). – Smokers - 380ºC hot water from volcano-like chimney (hot water reacts with seawater and forms black iron sulfide clouds. http://whyfiles.org/coolimages/images/csi/nur04506.jpg – Hydrogen sulfide gas provides food for nearby bacteria. Bathymetry – Ch. 23 • Bathymetry – study of underwater depths Ocean Floor • Continental Shelf- shoreline out to continental slope (flat) • Continental Slope – shelf edge to where water depth increases rapidly (sediments build up temporarily, until they tumble down to form continental rise). • Continental Rise – lies on ocean crust (part of ocean basin, not continent). • Abyssal Plain – deep seafloor, flat http://cgc.rncan.gc.ca/org/atlantic/unclos_e.php Ocean Floor http://www.earthscape.org/t2/meg01/meg01c.html#margin Ch. 24 – Currents and Tides Ocean Currents Ocean Currents – any continuous flow of water along a broad path in the ocean. Types of Currents: – Surface Currents – an ocean current that generally flows in the upper 1,000 meters of the ocean and primarily driven by the wind. – Deep/Density Currents – is heavier and denser than surrounding water, and sink from the surface toward the bottom of the ocean where they circulate in the deep ocean for 500 to 2,000 years before resurfacing. Global Ocean Currents Coriolis Effect and the Currents Direction in which currents flow depends is influenced by the Coriolis Effect. • Ocean currents in Northern Hemisphere turn clockwise (to the right) • Ocean currents in the Southern Hemisphere turn counterclockwise (to the left) Warm and Cold Currents • Warm Currents flow away from equatorial region on the western side of ocean basin. – (Example: Gulf Stream in North Atlantic, begins in Caribbean Sea and follows east coast of US northward around Cape Hatteras, NC, then veers NE across Atlantic and is called North Atlantic Drift, carries warm water to Iceland and British Isles, helps give warmer climate there.) • Cold Currents flow toward the equator on the eastern side of ocean basins. – (Example: Canary Current in North Atlantic or Labrador Current flowing out of Baffin Bay past Newfoundland – carries icebergs south, also meets the Gulf stream and produces some of thickest fog in world) Winds and Ocean Currents Two sets of prevailing winds tend to form most ocean currents: Trade winds and Westerly winds • Trade winds – steady, blow from northeast in the Northern Hemisphere and from the southeast in Southern Hemisphere, in North Atlantic push North Equatorial Current westward • Westerlies – blow from southwest in Northern Hemisphere and from northwest in Southern Hemisphere, in North Atlantic push North Atlantic Drift eastward. (we live here in the westerlies) Westerlies (where we live) - push North Atlantic Drift Current eastward Trade Winds – push North Equatorial Current westward Draw the cold and warm currents in on our big ocean map Density Currents • heavier and denser than surrounding water, • sink from the surface toward the bottom of the ocean where they circulate in the deep ocean from 500-2,000 years before resurfacing, • act as global conveyor belt moving warm water to colder areas and cold water to warm areas, • move oxygen important for marine animals, • drive the deep sea currents. Upwelling Currents • vertical current, • occurs when cold deep water comes to surface, • most common on the western sides of continents where prevailing winds blow along the coastline toward the equator, • cold water rises to replace the surface water that has been moved out to sea by Coriolis Effect, • contain large amounts of nutrients that phytoplankton need to grow, • major commercial fishing areas. Ocean Tides • Tides – the periodic rise and fall of the ocean surface due to the gravitational pull of the moon and the sun. – High tide = when water reaches the highest point on the shore. – Low tide – when water reaches the lowest point on the shore. High Low High Low Ocean Tides • Spring Tide – when the sun, moon (at full or new moon phase), and Earth are all aligned. Get extreme high tides and extreme low tides. • Neap Tide – when the sun and moon (at quarter phases) are at 90 degrees from each other. High tides not very high, low tides not very low (high and low tides are very similar). Tides and Storms and the Land that Protects Us • During storms the tides will increase. • Barrier Islands protect the mainland and help reduce the size of these waves from smashing into the mainland and help prevent damage to areas inland. – Example: during a Hurricane tides will increase and you may get a storm surge. Barrier Islands act as a block and get hit the hardest, so the mainland doesn’t. Barrier Islands Add Protection for the Mainland Chesapeake Bay Estuary • Estuary – an area where fresh water and salt water are mixing – Example: Chesapeake Bay • Fresh water from the rivers (Potomac, Rappahanock, James, Susequehanna, etc) flow into the Bay while salt waters from the Atlantic Ocean flow and mix into the Bay. Chesapeake Bay Issues • Sedimentation – sediments running into the waters. • Runoff - Increased phosphorus and nitrogen in the water (from use of fertilizers). • Overfishing, crabbing, etc. Troubled Waters • Coral Reefs – provide food and shelter for about ¼ of all ocean species, unfortunately many coral reefs are being damaged. – Fish that live there are caught for salt water aquariums and coral is collected. – Tourism – boats hit coral, their fuels poison them, etc.