El Niño Southern Oscillation. Pressure systems over Darwin Australia and Tahiti Oscillate Typically occurs every 4-7 years

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1 El Niño Southern Oscillation Pressure systems over Darwin Australia and Tahiti Oscillate Typically occurs every 4-7 years 1

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3 What is it? Normal Conditions... What is it? During El Niño. 3

4 Local Effects of El Niño Capitola Hotel, 1926 Venetian Courts (Capitola),

5 El Niño February, Venetian Courts, Capitola El Niño February, Ocean front property. 5

6 Mean weaning weights for Elephant Seal pups during were at an all time low 75% first-year mortalities for marine mammals (seals, sea lions) was reported Monterey was inundated by starving marine mammals El Niño Impacts on Coastal California 6

7 Monterey Bay Whale Abundance During El Niño Courtesy of B. Marinovic Monterey Bay as a Biological Refuge? Distance from sore Distance from shore During El Niño events ( , ), plant production was reduced by approximately 50% inside Monterey Bay, and >95% outside the Bay Source: Chavez et al. Prog. Oceanog

8 The Pacific Decadal Oscillation The Pacific Decadal Oscillation Oscillates between cool-wet and warm-dry conditions Averages about years Cool-wet PDOs make La Niñas more intense Warm-dry PDOs make El Niños more intense The PDO seems to have shifted between , amplifying both the El Niño and La Niña! 8

9 North North Atlantic Atlantic Oscillation Oscillation North Arctic Atlantic Oscillation 9

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11 90-day (ending 4 Feb. 2007) % of average precipitation In any given year, the global patterns of climate anomalies and events are a combination of random chance, short- and long-term oscillations, and (potentially) global warming. Because the Earth is not homogenous (not all water, for example), it s very difficult to tease apart the factors. 11

12 Santa Cruz temperatures Waves General Considerations Definitions - Mathematical - Classification Generating Waves -Wind generated - Storm surge - Whitecaps - Tsunamis - Swell - Internal Waves Wave-Shore Interactions 12

13 Waves A wave is the transmission of energy through a medium this is true for all types of waves! The particles of the medium stay in the same general area (there are no sound particles ) 3 Types of waves: Wave Types Transverse (side to side) Longitudinal (up-down) Orbital (circular movement) 13

14 For Simplicity, we will assume that ocean waves are Sine Waves (this isn t actually true!) 14

15 Net motion is up and down (bobbing) NOT a sine wave, so a slight forward motion as well 15

16 Mathematical Description Height (H) = crest to trough distance 16

17 Height (H) = crest to trough distance Wavelength (L) = crest to crest distance Height (H) = crest to trough distance Wavelength (L) = crest to crest distance Steepness = H/L 17

18 Period (T) = time for one wavelength Speed (C) = L/T Frequency (f) = 1/T, or C = L x f Wave Classification 18

19 Deep-Water Waves Classification Water depth (d) Deeper than L>2 C = L/T, but it s hard to measure L C = gt / 2π, --> C = 156 x T (m/s) Particles move in a circular pattern Classification Shallow-Water Waves (long waves) Water depth (d) < 1/20 of L C = ( g x d ) 1/2 --> 3.1 x (d) 1/2 Therefore, as depth shallows, wave slows Particles move elliptically, almost horizontally 19

20 Classification Transitional waves Length is > 2x but less than 20x depth (d) Properties are somewhere between deepwater and shallow-water waves Wave Relations 20

21 Wind-Driven Waves Capillary Waves --> Gravity Waves (Chop) --> White Caps --> Swell Can be Deep or Shallow waves Restoring Force: the source of energy dispersion that destroys a wave 21

22 Wind-Wave Formation Waves increase energy by : 1) Wind Speed 2) Duration 3) Fetch More Definitions Sea: local waves formed by wind events Confused Sea: local irregular waves of many periods and from many directions Fully developed Sea: the waves that form when fetch, wind speed, and duration are maximal Wave Train: waves that have left the windy region and are sorted by period 22

23 Sorted by wavelength (and therefore speed) this is wave dispersion Wave Trains These become swell Individual waves appear to be moving faster (2x) than the group velocity Interference Patterns All waves can be combined algebraically They combine in 3 patterns: Constructive (phases match up) Destructive (phases are exactly out of alignment) Mixed (most common somewhere in between) 23

24 Rogue Waves 24

25 Rogue Waves Can exceed 100 ft ship-killers Wave Trains 25

26 Not really a wave (we can t apply our mathematical descriptions to it) Storm Surge Hurricanes pile up water in the right front quadrant Tsunamis: Harbor Wave Caused by a seismic disturbance Most common in the Pacific Harmless until they hit the coast 26

27 Internal Waves Caused by changes in pycnocline Doesn t require much energy to get them going The Surf Zone Primary source of energy dissipation for swell When deep-water waves reach the shore, they form breakers as H/L > 1/ 7 27

28 Refraction, Diffraction, Reflection Refraction: waves feel bottom and will turn (or get dragged) towards headlands Refraction, Diffraction, Reflection Diffraction: waves can move around obstacles because energy is propagated in all directions 28

29 Refraction, Diffraction, Reflection Reflection: two waves of same wavelength, but moving in opposite directions, interact to form a standing wave. There is NO circular motion! Seiches (Standing Waves) 29

30 Second Node Standing Waves 30