Chapter 16 Outline

Chapter 16 Outline - Chapter 16 The Oceans Coastal...

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Chapter 16 – The Oceans, Coastal Processes, and Landforms Global Oceans and Seas Chemical Composition of Seawater Water universal solvent- dissolves ~57/92 elements in nature; most ntrl elements exist as solutes- seawater= solution, conc of dissolved solids by volume= salinity ; ocean ~homogeneous- ratio of indv salts ~doesn’t change; seawater chem. has varied over time w/in narrow range- consistent w/changes in sea-floor spreading rates, volcanism, sea lvl; ocean reflects conditions in earth’s envt Ocean Chemistry Result of exchanges btwn seawater-atmos-minerals-bottom sedmts-living orgms; plus flows of mineral –rich water enter ocean thru hydrothermal (hot-water) vents in ocean floor- black smokers; seawater uniformity due to complementary chem. rxns/cont’s mixing; 7 elements=>99% solvents in seawater: Cl - , Na + , Mg 2+ , SO 4 2- , Ca 2+ , K + , Br - ; also dissolved gases eg. CO 2 , N 2 , O 2 , suspended/dissolved organic matter, trace elements Average Salinity: 35% Expressed: 3.5% (% parts/100), 35,000 ppm (parts/mil), 35,000 mg/l, 35 g/kg, 35% (% parts/1000); worldwide, varies 34-37% due to atmos conditions above water/vol of freshwater inflows; equat’l water= grt precip= diluted salinity 34.5% ; subtrop= grt evap rates= conc’d, higher salinity 36% Brine - water exceeding avg 35% salinity; brackish - water lower than 35% salinity; oceans lower in salinity near landmasses b/c of freshwater runoff/river discharges; deep pockets/brine lakes vry hi sal’y Physical Structure of the Ocean Lyred;4 key aspects- avg temp, salinity, dissolved CO 2 , dissolved O 2- vary w/incr’g depth; surface lyr warmed by Sun, wind-driven; variations in water temp/solutes blended in mixing zone (only 2% of oceanic mass); below it= thermocline transition zone - 1+ km-deep reg of decr’g temp gradient w/o: Motion of surface; friction here dampens effect of surface currents & colder water temps at lower margin=>no convective movements; deep cold zone = 1-1.5 km depth to ocean floor=>~uniform temp/salinity; temps near 0°C but no freezing due to salinity, intense pressures; coldest water at bottom Coastal System Components Inputs to the Coastal System Most coastlines ~new; cont’s change; dynamic equilb btwn wave/tide/wind/current energy, supply of materials, slope of coastal terrain, fluctuation of relative sea lvl=>diff erosional/depositional features; inputs to coastal envt occur w/influence of gravity fr Earth, Moon, Sun; inputs incl: o Solar energy input drives atmos, hydrosphere; conversion of insolation kinetic energy=> winds, wthr sys’s, climate o Atmospheric winds =>ocean currents, waves- key inputs to coastal envt o Climatic regimes due to insolation, moisture; influence coastal geomorphic processes o Coastal geomorphology (rock type, landforms, tectonic activity)’s nature impt to determine rates of erosion/sedmt production o Human activities The Coastal Environment and Sea Level
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Chapter 16 Outline - Chapter 16 The Oceans Coastal...

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