GEO-SCI 103 Lecture 21Outline of Current Lecture: Sea Level Rise and Coastal Hazards (pgs. 250-257)I. Storm Surge and Tsunami: Coastal HazardsII. Global Warming and the Ocean SystemIII. Sea-level Rise and Shoreline RetreatCurrent LectureI. Storm Surge and Tsunami: Coastal Hazards- Coastline can be altered dramatically in a matter of hours with severe stormstrikes to the shore- Erosion bound to occur (mounds of sand)- The intensity of a storm surge can reach over dunes on a beach, causing widespread erosion and property destructionA. Storm Surgea) Water pushed strongly landward by winds and the forward direction of storm trackb) Surface of water is doomed up under intense low pressure of stormc) Danger further compounded if landfall coincides with high tide d) Strong onshore flow to the right eye= area of greatest danger/threat of storm surge e) Where winds are pushing on the shore, increasing the energy of the advancing waterf) Associated with extra tropical storms that form on the outside tropics like the nor’easters that occur along the East coast during winterg) Water and waves can breach the barrier dunes causing sand to be deposited in washover fans on the landward side of the dunes h) Pushes beach landward as it adjusts to sea level changes and all other coastal environments retain their original position relative to the beach as they move gradually farther inland B. Tsunamia) Large waves generated by major earthquakesb) Associated with subduction of oceanic crustThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.c) Long wavelength (L>200 km)d) Height at outset is low, but because of long wavelength they move fast e) Height increases and speed slows as they move away from epicenter C. Hurricanea) Large, powerful tropical cyclone (feeds on heat of ocean)b) Intense low atmospheric pressure (circulation is counterclockwise in theN. Hemisphere, clockwise in the S. Hemisphere)c) Strong sustained windsd) Bands of heavy rain. II. Global Warming and the Ocean SystemA. Sea Level Risea) As temperature warms, polar ice caps will meltb) Volume of ocean will expand as the temperature of the water increasesB. The ocean conveyora) Global climate is dependent upon the movement of surface and thermohaline currentsb) Changes in the temperature or salinity of sea water could have major effects upon the world climate systemC. Ocean Chemistrya) About half of the carbon dioxide that the industrial revolution pumped into the atmosphere has disappeared (dissolved in ocean)b) CO2+H20H2CO3H*+CHO3 (carbon dioxide III. Sea Level Rise and Shoreline Retreat: A real ThreatA. Coastal Environments with Rising Sea Levela) Along gently sloping coastlines, even a small rise in the sea level can have a major effect on the landward migration of the coastlineb) Small rise of sea level across a low lying coastal plain translates into a significant advance of the sea or retreat of the shorelinec) Coastal environments retain their original profile as they role landward with rising sea leveld) With rising sea level, sand washes over the dunes and buries the marshes and mudflats, and eventually fills in the bays/lagoons as the shoreline retreats and the beach and dunes migrate landwardIV. Options in the Face of Rising Sea LevelA. Hard Stabilizationa) Armoring of the coast with rocks and mammade structures, is designed to protect the coast from erosion, trap sand or redirect wave energyb) Seawallssolid walls of rock, timbers, concrete built parallel to the shore with intent to protect buildings from washing into sea. They can collapse during storms, increasing both the amount of erosion resulting property damage. c) Jettieslong structures build perpendicular to the shore. Protects harbor or channel inlet from incoming swell. Sand accumulates on the updrift side and a sand split will develop at the end of the jetty to prevent the inlet from being filled with sand d) Groinsshort structures built perpendicular to the shore, art way across the surf zone. Traps sand from longshore transport system and widen an eroding beach. Sand will accumulate on the updrift side and cause erosion on the down drift side e) Breakwatersrigid structures built a short distance from and parallel to the shore. Provides quieter water for boat anchorage. Disrupts incoming swell which provides the energy to move sand via longshore drift; sand accumulates in quieter water behind the breakwater, must be dredged. B. Soft Stabilizationa) Beach nourishment intended to replace the sand that has been lost from the longshore transport systemC. Relocationa) Movement of structures is an option that will preserve the natural character of the