1. Some Surface Currents

2. Latest Sea Level Pressure

3. Introduction Some surface currents influence sea level Some surface currents influence sea level –Therefore, influence coastal erosion –Am excluding tides, longshore currents, etc Currents mostly seasonal Currents mostly seasonal Related to upwelling and downwelling Related to upwelling and downwelling

4. Upwelling and Downwelling Upwelling Upwelling –Describes process of marine waters rising from some depth in the oceans Downwelling Downwelling –Opposite. Process of marine waters sinking to greater depths.

5. Ekman Transport Net water movement 90° to right of wind direction in N. Hemi.Net water movement 90° to right of wind direction in N. Hemi. Winds over H 2 O set ocean surface currents in motionWinds over H 2 O set ocean surface currents in motion Surface H 2 O is deflected 45° by Coriolis EffectSurface H 2 O is deflected 45° by Coriolis Effect In Northern Hemisphere Deflection increases with depthDeflection increases with depth

6. Upwelling and Downwelling

7. California & Western U.S. Spring & Summer Spring & Summer –Northerly wind –Promotes upwelling –Lowered sea level Winter and Summer Winter and Summer –Southerly winds –Promotes downwelling –Higher sea level Aleutian Low A semi-permanent, subpolar area of low pressure located in the Gulf of Alaska near the Aleutian Islands. It is a generating area for storms and migratory lows often reach maximum instensity in this area. It is most active during the late fall to late spring. During the summer, it is weaker, retreating towards the North Pole and becoming almost nonexistent. During this time, the North Pacific High pressure system dominates. NWS

8. Los Angeles & San Diego Average Seasonal Cycles in Sea Level

9. Divergence and Convergence ConvergenceConvergence – Wind-driven currents collide – Downwelling DivergenceDivergence – Currents move away – Upwelling Equatorial regionEquatorial region – Created by SE and NE trade winds – Divergence – Upwelling

10. Note Equatorial Upwelling

11. Peru Upwelling

12. California Upwelling Spring & Summer High Productivity Diatomaceous sediments accumulate, preserved in basins

13. Stop Here

16. Geostrophic Currents Gyres Convergence thickens surface layer – builds a domeConvergence thickens surface layer – builds a dome Circular current systems in major ocean basins: GyresCircular current systems in major ocean basins: Gyres gyre Boundary currents parallel to ocean marginsBoundary currents parallel to ocean margins

17. Pacific Currents Equatorial and boundary currents  ConvergenceEquatorial and boundary currents  Convergence – Warm currents in West Pacific – Cold currents in East Pacific i.e. Kuroshio, Australia i.e. California, Peru

18. California Current Most studied-separates from east flowing North Pacific Current Flow from shelf break to 1000km offshore Movement down to 500m, speeds to.5m\sec Interacts with sea floor Eddy produces counter current

19. California Current Colder water transported southward Changes in current strenght,position impacts sediment accumulation Changes associated with El Nino/La Nina events, glacial/interglacial period

20. Santa Barbara Basin Core-Monterey Rocks Laminated diatomaceous sediment Laminated diatomaceous sediment Changes in forams distinct at 1925 and later. More tropical-subtropical forms Changes in forams distinct at 1925 and later. More tropical-subtropical forms Low oxygen level preserve layers Low oxygen level preserve layers www.sakura.cc.tsukuba.ac.jp (c) 2005 David Field

22. Western Intensification Gyres displaced to west by Earth’s rotationGyres displaced to west by Earth’s rotation Western IntensificationWestern Intensification – Faster, narrower currents Eastern CurrentsEastern Currents – Slower, more diffuse currents

23. El Niño Year Factors producing El Niño yearFactors producing El Niño year – Warmer H 2 O moves east – Rainfall shifts from eastern to western Pacific May result from atmospheric pressure changesMay result from atmospheric pressure changes – Thermocline deepens – Trade winds weaken – Upwelling ceases along western S. America

25. El Niño Impact Leads to death of cold-water organismsLeads to death of cold-water organisms Warm-water organisms migrate north and southWarm-water organisms migrate north and south

26. Temperature Variations britannica

27. Coriolis on a Cylinder