ES 106 2006 May 5, Dynamic Ocean I. Surface Circulation A. Related to general circulation of atmosphere B. Pattern of ‘gyres’ 1. include poleward warm current, and equatorward cool current 2. North Pacific Gyre, South Pacific Gyre, North Atlantic Gyre, South Atlantic Gyre, Indian Ocean Gyre 3. ‘Coriolis Effect’ deflects current to right in northern hemisphere, to left in southern hemisphere 4. important named currents: Gulf Stream, California Current, Kuroshio Current, equatorial currents, West Wind Drift C. effect on climate: about ¼ of worldwide heat transfer by ocean currents 1. transfer of heat apparent in cold months in mid-latitudes 2. cold currents apparent in tropics, and in mid-latitudes in warm months D. upwelling—vertical movement of water 1. winds blow surface water away from continent 2. deep nutrient-rich water rises from deep ocean: phosphates, nitrates II. Deep Ocean Circulation—thermohaline circulation A. Cold, saline polar waters sink B. Moves on sea floor 500 to 200 years C. Rises in upwelling areas to be warmed and moved poleward III. Shoreline— A. interface of sea and land, B. affected by sea level changes, erosion, and tectonic vertical movements IV. Coastal Zone A. Shoreline, shore, coast, coastline: terms overlap in distinction B. Beach: accumulation of sediment along landward margin of ocean 1. foreshore from low tide to high tide, includes beach face 2. backshore only wetted in storm events, includes berm 3. nearshore has wave-bottom turbulence 4. offshore out of wave influence V. Waves—ocean energy generated by wind on surface A. Terminology: wavelength, crest, trough, wave height, wave period B. Water movement orbital in nature, dies out at about ½ wavelength below surface C. Surf zone where the wave energy touches bottom, oversteepens, breaks VI. Wave Erosion—hydraulic power of water, and abrasion of sedimentVII. Sand Movement on Beach—‘River of Sand’ A. Low energy waves move sand up beachface, water soaks into sand B. High energy waves has less infiltration, backwash erodes sand from beachface C. Wave refraction— 1. headlands have waves slow first, bay areas slow later 2. curves in wave crests at shoreline D. Longshore transport: beach drift and longshore currents 1. Angle of water onto shoreline influences swash, 2. water goes back downslope perpendicular to water edge, 3. zigzag pattern of sand VIII. Shoreline Features A. Erosional features 1. cliffs and platforms 2. arches and stacks B. depositional features 1. spits, bars, tombolos by beach drift 2. barrier islands may be flooded remnants of coastal dunefields C. evolution of a shoreline—straightens over time IX. Stabilizing the Shore—attempts to retain sand A. Groins, breakwaters and seawalls (Hard Stabilization) B. Alternatives to hard stabilization include 1. Beach Nourishment and 2. Relocation X. Coastal Classification A. Emergent coasts— 1. changes in elevation or sea level 2. characterized by cliffs and terraces B. Submergent coasts— 1. mostly changes in sea level 2. characterized by estuaries—flooded river
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