Oceans Unit 3 Introduction The land oceans play

Oceans Unit 3

Introduction • The land oceans play a major role for life on • Regulate temperatures, shape weather & climate patterns, cycle elements through the biosphere • Life on Earth originated in the oceans

Introduction • Understanding of the oceans have advanced greatly, but we still know very little about them https: //www. facebook. com/search/top/? q=h ow%20 deep%20 the%20 ocean%20 is

Ocean Structure & Composition • Different layers with different properties • Pressure increases with depth • More water on top pressing down • Pressure doubles every 10 meters down

Ocean Structure & Composition • Epipelagic=sunlight zone 1 st 200 meters below surface • Warm • Mixed by winds & waves • Only 2% of all ocean water •

Ocean Structure & Composition • @ 200 meters, Continental Shelf slopes sharply down • Mesopelagic=twilight zone • Temp fall to less than 5 degrees Celsius at 1, 000 meters below • • Thermocline=inhibits vertical mixing of water with different densities 18% of ocean water

Ocean Structure & Composition • Bathypelagic=midnight zone Below 1, 000 meters • Uniformly cold (4 degrees Celsius) • No sunlight • Pressure @ bottom of zone=5, 880 lb/in 2 •

Ocean Structure & Composition • Abyssopelagic=abyssal zone • Below 4, 000 meters to bottom • Little life exists here • Abyssal & midnight zones contain 80% of all ocean water

Ocean Structure & Composition • Deep ocean trenches occur where 2 ocean plates collide & one subducts below the other • Deepest trench is Marianas Trench near the Philipines (10, 000 meters deep) Highly specialized life can survive down here • Fish, shrimps, sea cucumbers, microbes •

Ocean Structure & Composition • Movements of plates generates earthquakes & tsunamis 2011 earthquake off the coast of japan was 9. 0 • 40. 5 m (133 ft) tsunami that traveled 10 km (6 mi) inland • Killed almost 16, 000 people, 6, 000 injuries, 2, 500 missing people, 230, 000 people without a home • • Many ocean trenches are along the Fire” “Ring of

Ocean Currents • Mixing is vital for the oceans Exchanges heat between surface/deep waters • Redistribute heat from low to high latitudes • Carry nutrients from deep to surface waters • Shape coastal climates •

Ocean Currents • Forces that cause ocean mixing Winds cause waves & surface currents • Deep ocean water is mixed due to differences in density • • • Salty & cold is denser than fresh and warm Along coastlines, warm surface water is blown away and deep cold water rises • upwelling

Ocean Currents • Upwelling surface brings nutrient rich water to the • Circular currents, gyres, occur at 25 -30 degrees latitudes. Counter-clockwise in northern • Clockwise in southern •

Ocean Currents • Ocean currents redistribute heat from high to low latitudes by moving warm water from the equator towards the poles. • As currents flow, they warm or cool the atmosphere • Upwelling will cause the atmosphere to cool

Ocean Currents • Ocean waters are warmest in the tropics and coldest at the poles • Angle of the sun’s rays • Oceans respond to temp changes slower than the atmosphere Water has high specific heat capacity • It takes more energy to increase temp •

Thermohaline Circulation • Global conveyor belt • Current rivers has a flow equal to 100 Amazon

Thermohaline Circulation • Driven by buoyancy differences due to temperature & salinity differences • Higher temps & salinity @ equator Direct sunlight @ equator • More evaporation @ equator leaves salt behind in water •

Thermohaline Circulation • The • ice melting at the poles lowers salinity Human driven climate change is increasing polar ice melting • If the conveyor belt slows, temperatures fall • If it increases, temperatures rise

Ocean Circulation and Climate Cycles • Monsoons arise when land & water heat up at sharply different rates • Hot air masses over land in the summer create low-pressure zones, bringing in moist ocean air • When the moist air is lifted by mountains, it condenses

Ocean Circulation and Climate Cycles • In the winter, land cools quicker than water • Warm air over water rises & draws winds from the continents producing clear weather over land • Southwestern US= Summer Monsoons from July-September

Ocean Circulation and Climate Cycles • Hurricanes occur from June-November in Atlantic & May-November in Pacific • Typical season has 11 named storms, 6 becoming hurricanes, 2 being major

Ocean Circulation and Climate Cycles • El Nino Southern Oscillation= every 3 -7 years • Normally Pacific • When a large gyre sits over southern it is strong enough, winds blowing are strong enough to pile warm water in the western pacific

Ocean Circulation and Climate Cycles • The movement of warm water causes an upwelling of cold nutrient rich water • • In Supports fisheries near coast of South America an El Nino year, everything flips into reverse

Ocean Circulation and Climate Cycles • The reversal of weak equatorial winds and warm water to South and Central America and California causes warm moist air to rise • North & South American coasts get heavy rains and landslides • Indonesia and Asia get droughts

Ocean Circulation and Climate Cycles • La Nina= unusually intensive reverse phase • Produces very wet weather in Asia and dryer than normal conditions in U. S. A • Full La Nina/ El Nino cycle lasts 5 years

Biological Activity in the Upper Ocean • Most organisms in the oceans are nourished directly or indirectly by plankton • Oceans account for nearly half to the world’s energy output • Nearly all of it is in the thin upper layer of the oceans

Biological Activity in the Upper Ocean • Phytoplankton, foundation of marine food chains, are microscopic • 2 types are the two most abundant organisms on Earth • 500, 000 cells per m. L of sea water

Biological Activity in the Upper Ocean • Producers water • in oceans work best in clear Phytoplankton can work as deep as 110 meters • Turbid coastal waters=only 20 meters deep • Pollution & dredging reduce biological productivity

Biological Activity in the Upper Ocean • If waters are mixed, phytoplankton can be dent down and not be as productive • If nutrients (C, N, P, Si, Fe) run out for phytoplankton, productivity lessens • Grazers also effect the productivity

Biological Activity in the Upper Ocean • If there is optimal light, temp, nutrients, and low numbers of grazers a bloom occurs • Blooms can color the oceans red, brow, or yellow-green • Blooms can deplete oxygen levels when the plankton die & decompose

Biological Activity in the Upper Ocean • Lack of oxygen can be dangerous to other sea life • Some blooms produce neurotoxins that are dangerous to humans and fish

Biological Activity in the Upper Ocean • Blooms can be triggered by runoff from fertilizers or chemicals or storms mixing oceans and bringing up nutrients • Usually occur in spring with rising temps and longer days • Most blooms are beneficial to ocean life

Biological Activity in the Upper Ocean • Climate cycles have a major impact on productivity in oceans • During El Nino, fewer plankton growth reduces food for anchovies and sardines, reducing food for tuna, sea lions and birds

The “Biological Pump” • Deep waters must have nutrients for plankton in the upper ocean • Nutrients are carried down in a rain of particles called marine snow • Fecal pellets, shells of dead plankton, and other dead/dying microorganisms

The “Biological Pump” • Most are too light to sink, but when they stick together they sink • It can take days/weeks to get to the ocean floor • Bottom-dwellers consume the “snow” • Other bits are oxidized and recycled into usable nutrients • The rest is buried in sediments, forming oil and gas deposits

The “Biological Pump” • The biological pump is also important to the global carbon cycle • Plankton take up carbon from the atmosphere and cycle it down through the “snow” to the bottom of the ocean • Without the biological pump, the concentrations of CO 2 would be much higher