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Oceanography in a Conch Shell Arcadia HS OSB History Just research the crucial accomplishment of the notable figures. There are three major stages in the history of ocean research: • Ocean exploration was the period when people explored the ocean boundaries. Notable explorers include: The Phoenicians, Pytheas, The Polynesians, Herodotus, the Vikings, Bartholomew Diaz, Vasco de Gama, Ferdinand Magellan and Sebastian del Cano. • Early scientific investigations began when people began to describe the ocean. Notable scientists include: James Cook, Matthew Fontaine Maury, Charles Darwin, C. Wyville Thomson, and Fridtjof Nansen. Also Alfred Wegener. • Modern oceanography (oceanology) began in the twentieth century with interdisciplinary oceanic research and use of complex scientific instruments. Continental margin Planet and Basins • • • • • • Ocean basin: large portion of oceanic floor that lies deeper than 2000 meters. The Earth’s internal spheres: inner core, outer core, mantle (mesosphere + asthenosphere), crust (lithosphere) 3 bathymetric provinces: continental margins, deep-ocean basins, midocean ridges. (See figures right) Types of rock: granite (land), basalt (ocean), andesite (mix) Isostasy: principle of mass balance; why landmasses and basins exist. Important concepts: continental drift (Pangaea), sea-floor spreading (magnetic anomalies, subduction zones), plate tectonics Deep-ocean basin Midocean ridge Sediments • • • • Classification by grain size: colloid, mud (clay & silt), sand, gravel Classification by formation: terrigenous, biogenic (calcareous & siliceous), authigenic (ferromanganese nodules, phosphorite), volcanogenic, cosmogenous Factors that control sedimentation include particle size and the turbulence of the depositional environment. Processes include bulk emplacement (slumps, slurries, turbidity currents) • • As wind moves across the water, collision of air molecules with water molecules inefficiently transfers energy from the air to the water (water moves 3-4% of wind speed). Coriolis deflection: Earth’s rotation causes moving objects relative to the ground to be deflected to the right in the Northern hemisphere and to the left in the Southern hemisphere. Seawater • • • • • • • Properties: high heat capacity, solvent power, covalent bond, salinity (average 35 ppt, saltier termed brine). Seawater most dense at 4 degrees C, freezes at -2. Also pH (acidic, basic, buffers). Concentration of solute in seawater measured in ppt (parts per thousand, also ppm, ppb). There are major constituents, nutrients, gases, and trace elements. Residence time: average time ion remains in solution in oceans. Principle of Constant Proportion Gradients: thermoclines (temperature), haloclines (salinity), pycnoclines (density) Anoxic: no dissolved oxygen (no photosynthesis/respiration, rather anaerobic bacteria). Desalination: distillation, freezing, reverse osmosis, electrodialysis, salt absorption Hydrologic cycle (evaporation, condensation, etc.) Circulation (Find diagrams, difficult concepts) • • Winds are created by fluids flowing from zones of high to low pressure (pressure gradient) Wind direction indicates what direction the wind comes from. • • • • • • • Global wind circulation Ekman Spiral: flow pattern driven by Coriolis effect and frictional drag on water column varying with depth. Net transport (Ekman transport) 90 degrees to right/left of wind. Upwelling: rising of bottom water; downwelling: sinking of surface water. Langmuir circulation is a complex horizontal helical (spiral) motion that extends parallel to the wind. Geostrophic currents: steady flow resulting from a dynamic balance between pressure gradient and Coriolis deflection. Because Earth rotates from west to east, water pressed up against western sides of ocean basins cause western boundary intensification. Warm and cold-core rings: large swirling eddies circulating clockwise and counterclockwise, to the west and east of the Gulf Stream. Deep-ocean currents, or thermohaline circulation, is a result of density differences. • No need to memorize specific global currents at this stage, but here they are: http://www.jochemnet.de/fiu/GlobalCurrent.jpg • • Waves • Progressive waves: move in a direction; standing waves: oscillate back and forth. Wave base: depth of ½ wavelength; if water deeper than this then deep-water wave; else if depth greater than 1/20 of wavelength intermediate-water wave; else shallow-water wave. Waves are the undulatory motion of a water surface. Wave Parameters (missing T, wave period) Celerity (wave speed) = L/T • • • • • • Wave Spectrum Capillary waves: smallest, water restored by surface tension; seiche: standing wave; tsunami: seismic sea waves Wind-generated waves controlled by 4 factors: wind velocity, wind duration, fetch (area wind blows over), and original sea state. Fully developed sea: name says what it means; significant wave height: average of top 1/3. • • • Wave orbitals Constructive interference: crests coincide; may lead to rogue waves. Destructive interference: crests and troughs coincide. Dispersion: process of wave separation In shallow-water, waves slow down, wavelengths decrease, heights increase, period remains constant. Refraction: bending of waves so they hit shoreline orthogonally. When H/L (steepness of wave) reaches 1/7, the wave collapses as a breaker. The three types of breakers are spilling, plunging, and surging. Standing waves diagram below: • are progressive, 3. Water always in equilibrium with tidegenerating forces. Accurate model termed dynamic model of tides. Budges become rotary waves (like water swirling in cup) in an amphidromic system (tide rotates about fixed node). • Flood currents transfer water toward coast, ebb currents away. Tides • • • • • • Tides: waves with very long wavelengths that cause the sea level to rise and fall daily. Tidal range: vertical distance between high tide (crest) and low tide (trough). Tides can be diurnal (period: 1 day, actually 24 hr 50 min) or semidiurnal (recur twice daily, 12 hr 25 min), or mixed When tidal amplitude greatest, it’s called spring tide; when lowest, it’s called neap tide. Tides originate from gravitational attraction (mainly Moon) and centrifugal force Left bulge from centrifugal, right from moon Equilibrium (simplified) model of tides assumes: 1. Earth completely covered with water of infinite depth, 2. Tidal waves Shorelines • • • Coastal Zone Longshore currents: in surf zone, flow parallel to shoreline. Rip current: a narrow, swift, seaward flowing current along show that drains water from surf zone. Sand budgets: estimates of sand sources and losses; inputs: longshore transport in, river supply, cliff erosion, and onshore • • • • • transport; outputs: longshore transport out, offshore transport, wind transportation into dunes; balance: accretion, erosion, steady-state. Barrier islands: large deposits of sand separated from the mainland. Barrier islands are created in many ways including: sand ridges isolated by rising sea level, sand spits breached during a storm, and the vertical growth and emergence of longshore sand bars. Storm surge: extraordinary high water level that floods and erodes shore. Estuary: partially enclosed body of water where freshwater is mixed with salt-water. They form through various processes (drowned river valley, fjords, bar-built, tectonic) and can be categorized into salt-wedge, partially mixed, and well-mixed. A delta is an accumulation of sediment deposited at the mouth of a river as it flows into a standing body of water. They can be river-dominated (Mississippi), wave-dominated (San Francisco), or tide-dominated (Colorado, Ganges-Brahmaputra). Human coastal engineering structures include groins, jetties, breakwaters, and seawalls. • There are also the light zones: photic, dysphotic (twilight), and aphotic. Coastal Habitats Coral reefs Habitats Continental shelf Open ocean Deep-sea bottom Estuaries – crossroads between freshwater rivers and saltwater oceans; low species diversity but high carrying capacity, very fertile. Salt marshes – plant-covered, intertidal fringes of coastlines; very productive, serve as nursery grounds Mangrove swamps – dense tree growths of tropical and subtropical shorelines; mangrove is a large woody, tree-like plant with thick partially exposed network of intertwined roots; detritus food chain. Organic, wave-resistant rock (largely calcium carbonate / limestone) structures created by carbonate-secreting animals and plants, covered with living veneer; spectacular biodiversity. Hermatypic corals and zooxanthellae have a mutualistic relationship. Types: fringing reef barrier reef atoll. Relatively fertile, neritic (waters) and sublittoral (shelf bottom) zones Nutrient poor, sparse life; however, diverse biota. No light, very cold, high hydrostatic pressure, sparse food; life still exists everywhere. Biota • Classified by lifestyle: plankton – drifters; nekton – active swimmers; benthos – attached/move on seafloor. Plankton Biozones Algae (mostly phytoplankton) form 90% of ocean plants and photosynthesize. Nekton Benthos Diatoms are encased by frustrules, consisting of the epitheca and hypotheca, and cause diatom blooms. As swimmers fish must overcome surface drag + form drag + turbulent drag (tuna’s shape minimizes all three). Speed of fish proportial to shape of caudal (tail) fin. Aspect ratio of fin = H^2/A. Swimming specialties: cruising, maneuverability, and rapid acceleration. Arranged in vertical zonation, consist of epifauna (live on top of floor) and infauna (live inside substrate). Deposit feeders process mud to get mixed in organics. • • Humans • • • • For a taxonomic table of marine organisms and pictures, see pages 5-17 of: www.eos.ubc.ca/courses/eosc112/S07/Lec/EOSC112_BO_2007. pdf Ecology • • • • • • In ecosystems, temperature is the single most important regulator. Salinity necessitates osmoregulation (research how freshwater and saltwater fish handle differing salinities) Hydrostatic pressure (weight of water column) also causes adaptations such as gas-filled deep-ocean inhabitants. Very general knowledge of following terms assumed: ecosystem, autotroph, heterotroph, trophic levels (10% energy passed to each level above), herbivore, carnivore, omnivore, food chain/web, photosynthesis (takes CO2, produces oxygen), respiration (inverse of photosynthesis), grazer, predators, scavengers, filter feeders, deposit feeders, decomposers. Net primary productivity: amount of carbon fixed by photosynthesis minus amount demanded by respiration. Compensation depth: depth below which there is no photosynthesis; do not confuse with Carbon compensation depth (CCD): depth below which material composed of calcium carbonate is dissolved and does not accumulate on the sea). Least to most productive: open ocean, continental shelves, upwelling areas/deep estuaries, shallow estuaries/coral reefs. El Niño: episodic (3-5 years) war current that usually appears around Christmas off the coasts of Ecuador and Peru which decimates the indigenous organism populations. • • Pollutants concentrate in three primary areas: seafloor, pycnoclines, and the surface neuston layer. Hydrocarbons (oil spills), industrial effluents (sewage, metals, and artificial biocides such as DDT and PCBs) Ocean dredging and mining are two examples of human exploitation of the oceans. Bioaccumulation: process of chemical substance building up in an organism; biomagnification: accumulation and amplification of chemical substances over succeeding trophic levels; bioremediation: use of organisms (such as bacteria) to clean up an oil spill. Eutrophication: process whereby water becomes anoxic because it is choked with decomposing organic matter (such as that in sewage). Additional Reading For those of you who really want to give former OSB members a run for their money ;) http://www.amscopub.com/free_downloads.html?CID=11 covers marine biology more in depth. This will not be emphasized though.