Oceanography Course Outline - PDF

Oceanography Course Outline on Oceanography 1. Introduction 2. Properties of Water 3. Crust-Ocean Interactions 4. Currents 5. Tides 6. Waves 7. Marine Ecosystems 8. Effects of Movements on Biota 9. Effects of Global Warming Passing- 60% Chapter 1. Introduction Oceanography Study of processes in ocea...

Oceanography Course Outline on Oceanography 1. Introduction 2. Properties of Water 3. Crust-Ocean Interactions 4. Currents 5. Tides 6. Waves 7. Marine Ecosystems 8. Effects of Movements on Biota 9. Effects of Global Warming Passing- 60% Chapter 1. Introduction Oceanography Study of processes in oceans and seas Involves interlinked aspects: physical, chemical, biological and geological The branch of science that deals with the physical and biological properties and phenomena of the sea. Oceanography (from the greek words Ωκεανός meaning Ocean and γράφω meaning to write), also called oceanology or marine science, is the branch of Earth science that studies the ocean. Covers: 1. marine organisms and ecosystem dynamics; 2. ocean currents, waves, and geophysical fluid dynamics; 3. plate tectonics and the geology of the sea floor; 4. fluxes of various chemical substances and physical properties within the ocean and across its boundaries. Multiple disciplines Understanding of processes within it: biology, chemistry, geology, (meteorology), and physics. Seas - close to land, - much shallower than oceans - plant and animal life to thrive on a sea bed because of presence of light. Ocean beds - much deeper, support only very basic life forms like bacteria and shrimp that feed on them. - absence of light - high pressure Ocean Approximately 71% of the Earth's surface (an area of some 361 million square kilometers) Continuous body of water divided into several principal oceans and smaller seas. More than half is over 3,000 meters (9,800 ft) deep. Salinity is around 35 ppt (3.5%), and nearly all seawater has a salinity in the range of 30 to 38 ppt. Sea is part of an ocean that is partially surrounded by land; called an inland sea if totally surrounded Ocean is a body of salt water with no boundaries and limitless volume. Ocean is enormous and larger than sea. Largest sea is Mediterranean with area of 965,000 mi2 which is much smaller than the smallest ocean in the world the Arctic at 5,427,000 mi2. Five oceans - Pacific, Atlantic, Indian, Southern and Arctic. Seas are found on the margins of the ocean and are partially enclosed by land. Here, you can see that the Bering Sea is part of the Pacific Ocean. Four branches: Biological oceanography, or marine biology, is the study of the plants, animals and microbes (biota) of the oceans and their ecological interaction; Chemical oceanography, or marine chemistry, is the study of the chemistry of the ocean and its chemical interaction with the atmosphere; Geological oceanography, or marine geology, is the study of the geology of the ocean floor including plate tectonics; Physical oceanography, or marine physics, studies the ocean's physical attributes including temperature-salinity structure, mixing, waves, internal waves, tides and currents. Of particular interest is the behaviour of sound (acoustical oceanography), light (optical oceanography) and radio waves in the ocean. Genesis of an ocean Continental drift has reconfigured the Earth's oceans, joining and splitting ancient oceans to form the current oceans. Panthalassa - one vast world ocean Pangaea - supercontinent surrounded by Panthalassa Ocean Area (square miles) Average Depth (ft) Deepest depth (ft) Pacific Ocean 64,186,000 15,215 Mariana Trench, 36,200 ft deep Atlantic Ocean 33,420,000 12,881 Puerto Rico Trench, 28,231 ft deep 13,002 Java Trench, 25,344 ft deep Indian Ocean 28,350,000 Southern Ocean 7,848,300 sq. miles 13,100 - 16,400 ft deep the southern end of the South (20.327 million sq km ) (4,000 to 5,000 meters) Sandwich Trench, 23,736 ft (7,235 m) deep Arctic Ocean 5,106,000 3,953 Eurasia Basin, 17,881 ft deep Gulf and bay - arm of an ocean or sea. A bay has a wide mouth but a shallow inlet, A gulf has an inlet which is longer than the width of its mouth. A large bay may be called a gulf, cove, sound or bight. A narrow bay may also be called a fjord if its sides are relatively steep. Any bay may be adjacent to other bays. Gulf and bay - arm of an ocean or sea. A bay has a wide mouth but a shallow inlet, A gulf has an inlet which is longer than the width of its mouth. A large bay may be called a gulf, cove, sound or bight. A narrow bay may also be called a fjord if its sides are relatively steep. Any bay may be adjacent to other bays. Straits and channels A strait can be defined as a naturally formed narrow strip of water between two continents, islands or two larger bodies of water. It is usually used for navigational purposes and is sometimes referred to as a channel when it is found between two land masses. A channel is a wide strait or waterway between two landmasses that lie close to each other. A channel can also be the deepest part of a waterway, or a narrow body of water that connects two larger bodies of water. Ocean Regions: Blue Water Characteristics 65 percent is considered blue water (open ocean) -waters that lie beyond the coastal shallows (coastal ocean) Oceanic life is divided into two major categories: benthic environment (the sea floor) pelagic environment (the ocean waters). The pelagic environment is further divided based on water depth. The neritic zone is the first 200 meters (656 feet) of ocean water, which includes the seashore and most of the continental shelf. The oceanic zone extends from 200 meters (656 feet) deep all the way down to the bottom of the ocean, which can be thousands of meters deep. Littoral Zone - Characteristics The word "littoral" is derived from the Latin noun litus, litoris, meaning "shore". The littoral zone is the part of the ocean closest to the shore. The littoral zone is from the shoreline to 600 feet (183 meters) out into the water and is divided into three zones -supralittoral zone -intertidal zone -sublittoral zone. The supralittoral, or spray, zone is only underwater during unusually high tides or during storms. It starts at the high-tide line and goes toward dry land. The intertidal zone is between the high-tide and low-tide lines. The sublittoral zone extends from the low-tide line out to 200 meters. Littoral zone shallow well lighted subject to fluctuating temperatures and erosion of shore materials through wave action coarse bottom sediment which is especially evident near unprotected shores inhabited by rooted aquatic vegetation; sometimes wave action is so great that large aquatic angiosperms are absent and only algae, attached and streaming in the currents or growing as benthic mats, are present great diversity and high annual production set this community apart from the benthos in deeper areas Littoral zone Parts of the ocean Horizontal zonation Intertidal/littoral zone – zone between high and low tides Neritic zone (near shore) – shallow water zone ont eh continental shelf Oceanic zone – region of the open ocean beyond the continental shelf Vertical zonation Bathyal zone – region of the continental slope and rise Abyssal zone – area of ocean deep formed by abyssal plain Hadal zone – zones formed by trenches Euphotic zone – zone where photosynthesis is greater than respiration Transition zone – zone where gross photosynthesis is less than respiration Aphotic zone – zone where total darkness prevails Sublittoral zone– extends lakeward from the littoral. sediments are finer grained dimly lighted lacking a benthic macroflora well oxygenated contains fewer species than the littoral assemblage old shells of gastropods and pelecypods that inhabit the littoral zone are found accumulated in the sublittoral zone serves as a cemetery of some littoral species Profundal zone deep cold region light is much reduced temperature is nearly uniform O2 is scanty and CO2 abundant hydrogen ion concentration is high because of the presence of carbonic acid characterized by decay rather than organic matter production sediments are fine particles largely made up of material produced within the lake benthos tells something of the conditions in the hypolimnetic water and ultimately a great deal about the nature of the lake TERRAIN-FORCED THUNDERSTORMS These storms usually occur in the afternoon and can cause wind shear, heavy rain, hail and high winds. They are a danger to airborne operations and can hurt communications and the ability to move around the land. OFFSHORE WIND Winds blowing off the shore can travel at speeds of 4 to 6 knots and extend 5 to 10 nautical miles. These winds, which can carry smoke, fog and dust offshore, can reduce visibility and hurt coastal operations. ONSHORE WIND Winds can blow from the ocean onto the shore at speeds of 8 to 14 knots and extend as much as 5 to 10 nautical miles. They can make the waves taller and, if coastal hills are present, create clouds as the moist sea air is lifted over the hill. These winds make periscope and mine detection harder and can block inland targets as the waves become higher. TERRAIN-FORCED WIND Features on land can disrupt the wind's flow. For example, the wind patterns above a mountain can differ from the wind patterns around the mountain. This creates wind shear. Wind shear happens when wind flows in different directions or at different speeds over a short amount of space. How does this affect the Navy? Think about aircraft flying in low to drop parachutes or gliders or helicopters flying in to drop off or pick up soldiers. The wind shear could cause turbulence, which would make these missions dangerous. RIVER DISCHARGE Where a river meets the ocean, fresh water flows into salty water. The colder river waters are often less dense than the warmer ocean waters. The density differences can create distinct layers in the relatively shallow waters. A submarine or diver operating in this environment would have to alter its buoyancy to adjust to the density changes. Also, a river flowing into the ocean often brings a load of sediment into the ocean. This can alter in the shape of the ocean bottom, which would create problems for submarines and divers. REEFS, BARS & CHANNELS Reefs are usually found in shallow tropical waters, but bars and channels can form almost anywhere. Bars and channels are known to change slowly with the turn of the seasons or daily with tides and currents. Boats, submarines, swimmers and torpedoes must all take care when approaching any of these. SHIPWRECKS Most shipwrecks occur near shore. They can be a problem to avoid, or they can help submarines, which can linger close to them and avoid being spotted. BIOLUMINESCENCE Some organisms that float on the surface can produce their own light. This ability is called bioluminescence. Swimmers, periscopes, boats and submarines must all be careful when traveling along the water's surface. Disturbances cause the bioluminescent organisms to glow. Because of these glowing organisms, a ship's wake may be visible for 6 nautical miles! INTERNAL WAVES Tides or currents may disturb water, which is separated into distinct layers because of density. These disturbances can change the depth of the thermocline. LITTORAL MARINE LIFE Dangerous marine life (e.g., jellyfish, scorpion fish, saltwater crocodiles) may be present, and typically there is more marine life present than in near-surface open ocean. BEACH PROFILE Sand profiles change seasonally and often after a storm. Beaches with sandbars often have rip currents. Equipment-laden troops can drown in the deep trough in between a sandbar and the shore. COASTAL CURRENTS Coastal currents are caused by the wind, tides and sea surface slope and can travel at speeds greater than 4 knots. These currents can change rapidly, making charts of the currents useless. LAND-FAST ICE Sea ice attached to the coast can extend on top of waters with 2 to 25 meters (6.5 to 82 feet) depth, sometimes up to 100 to 200 kilometers (62.1 to 124.2 miles) depth around offshore islands. The ice, which can be 2 to 3 meters (6.6 to 9.8 feet) thick, can completely block or severely restrict channels and bays. The ice also changes the salinity of the water. Ocean Floor - Continental Margin & Rise Surrounding nearly all continents is a shallow extension of that landmass known as the continental shelf. This shelf is relatively shallow, tens of meters deep compared to the thousands of meters deep in the open ocean, and extends outward to the continental slope where the deep ocean truly begins. Sediment from the erosion of land surfaces, washed into the sea by rivers and waves, nourishes microscopic plants and animals. Larger animals then feed upon them. These larger animals include the great schools of fish, such as tuna, menhaden, cod and mackerel, which we catch for food. The continental shelf regions also contain the highest amount of benthic life (plants and animals that live on the ocean floor). The continental slope connects the continental shelf and the oceanic crust. It begins at the continental shelf break, or where the bottom sharply drops off into a steep slope. It usually begins at 430 feet (130 meters) depth and can be up to 20 km wide. The continental slope, which is still considered part of the continent, together with the continental shelf is called the continental margin. Submarine canyons cut through many of the continental margins. Some of these have been carved by turbidity currents, which are bottom currents that carry lots of sediment. Past the continental slope, we find the continental rise. As currents flow along the continental shelf and down the continental slope, they pick up and carry sediments along and deposit them just below the continental slope. These sediments accumulate (gather) to form the large, gentle slope of the continental rise. Ocean Floor - Deep Ocean Basin The deep ocean basin, which is about 2.5 to 3.5 miles deep, covers 30 % of Earth's surface and has features, such as abyssal plains, deep-sea trenches and seamounts. The abyssal plain is the flat, deep ocean floor. It is almost featureless because a thick layer of sediment covers the hills and valleys of the ocean floor below it. Deep-sea trenches are the deepest parts of the ocean. The deepest one, the Marianas Trench in the South Pacific Ocean, is more than 35,000 feet (10,668 meters), or almost 6.6 miles (10.6 kilometers) deep. A Navy-owned submarine, the Trieste, still holds the record for diving to the bottom of the deepest part of the Marianas Trench, the Challenger Deep, on January 23,1960. Ocean Floor - Mid-Ocean Ridge The mid-ocean ridge is two chains of mountains separated by a large depression (or rift valley) that form at a spreading center (or where two plates are drifting apart). The mountain ranges can have peaks as high as 12,000 feet (2,500 meters meters) and some even reach above the ocean's surface. Iceland, along the mid-Atlantic Ridge, is an example of this. In the rift valley, which can be 15 to 30 miles (24 to 48 kilometers) wide, new oceanic crust is being made, which means lots of seismic activity is happening. Hydrothermal vents were discovered in rift valleys. The plates are spreading at a rate of 2.5 centimeters a year. This means that every thousand years or so the plates spread and grow about 25 meters. Most seamounts began life as volcanoes formed over hot spots in the ocean floor. After the crust moves off the hot spot, the volcanic activity stops. Seamounts are usually 25 miles (40 kilometers) in diameter and can be 10,000 to 15,000 feet (3000 to 4500 meters) tall. In fact, some are so tall that their peaks pierce the ocean surface forming a volcanic island or, if there are more than one seamount, a volcanic island chain (think of the Hawaiian Islands). Seamounts whose peaks have eroded and become a flat surface are called guyots. Coral reefs sometimes grow around seamounts that rise above the ocean waters. As the seamount sinks or its peak erodes, the seamount will disappear beneath the water leaving the coral ring. This is called an atoll.