Learning About Beaches

1. Learning About Beaches Maia McGuire, PhD University of Florida Sea Grant Extension Program

2. Only one ocean… • There is one ocean with many ocean basins, such as the North Pacific, South Pacific, North Atlantic, South Atlantic, Indian and Arctic. • The ocean is the dominant physical feature on our planet Earth — covering approximately 70% of the planet’s surface.

3. Florida Beaches • 667 miles of beaches • 1197 miles of shoreline • More than half of Florida’s shoreline is beaches

4. Ocean sciences • Second grade will be studying beach LIFE, however it is important to understand some of the physical and chemical aspects of the ocean as these affect the beach biology…

5. Ocean circulation http://www.windows2universe.org/earth/Water/circulation1.html http://msx4.pha.jhu.edu/ssip/asat_int/ocean.html

6. Focus on the North Atlantic • Clockwise circulation (surface currents) • Gyre (Sargasso Sea) in the center

7. Longshore Current Source: Hayes & Michel, 2008

8. What makes water move? • Water moves because of currents • Temperature can make water move • The earth’s rotation makes water move • “Coriolis effect” results in clockwise circulation in northern hemisphere and counterclockwise in the southern hemisphere

9. Zooming in on Florida • Gulf has wide continental shelf • Loop Current • Atlantic has narrow shelf • Gulf Stream • Longshore currents

10. Continental shelf….? http://www.unfalumni.org/?p=139

11. Back to the ocean…. • We generally cannot see currents sometimes we can see the boundary along the edge of a current (“weed line”) http://www.safmc.net/Library/Sargassum/tabid/414/Default.aspx

12. What about tides? • Tides are the result of gravitational pull of the moon and sun, in combination with the rotation of the earth. Source: Hayes & Michel, 2008

13. Tides in Jacksonville • Two high and two low tides each day; about 6 hours apart (alternating high and low). Actual time of low tide varies along the coastline. Data are for Mayport. Difference between high and low tide (feet): February 2nd: 4.6 to 5.2 (new moon) February 11th: 3.2 to 3.3 February 18th: 6.2 to 6.4 (full moon)

14. Waves • Most commonly caused by wind blowing on the ocean’s surface.

15. Activity • Wind and waves (Monterey Bay Aquarium) • Waves in a bottle

16. A very little ocean chemistry • The sea is salty • Where do the salts come from? • The salinity of the Atlantic Ocean is about 36 parts per thousand (ppt or ‰) or 3.6 %. • These salts contain minerals which are often used by marine plants and animals to make skeletons, etc. • Most marine animals need oxygen, just like land animals, however they breathe oxygen that is dissolved in the sea water (they cannot breathe in air).

17. Salt water is different from fresh water • It is heavier • Things float better in salt water • We cannot tell fresh water from salt water by looking at it

18. Moving onshore…. • The Atlantic coast of Florida is influenced by many factors…some natural, and some human.

19. Effect of Climate on Shorelines • Wind patterns and off-shore storms affect wave size and direction • Presence or absence of major rivers (amount of precipitation) • Chemical and mechanical weathering (erosion) that produces sediments • Effects of extreme weather (cold and heat)

20. Hydrodynamic Regime • The interaction of water in motion with the coastal sediments • Commonly expressed as the ratio of the wave energy to the tidal energy • Used to classify depositional shorelines

21. Where does our sand come from? Southeastern U.S. – 100 m.y.ago Source: Hayes & Michel, 2008

22. Major Rivers of the SE U.S. Coast Source: Hayes & Michel, 2008

23. Longshore Current http://www.uwsp.edu/geo/faculty/ritter/images/lithosphere/coastal/beach_drift_USGS.jpg

24. Longshore transport of sand

25. Global Avg. Sea Level Observations:20th century rate: 1.7 ± 0.5 mm/yr1993 to 2003 rate: 3.1 ± 0.7 mm/yr thermal expansion 1.6 ± 0.5 mm/yr changes in land ice 1.2 ± 0.4 mm/yr “There is high confidence that therate of sea level rise accelerated between the mid-19th and the mid-20th centuries based upon tide gauge and geological data.” Sources: IPCC 2007 WG1-AR4 , Ch. 5, Fig. 5-13 & Tech. Summary section TS3.3.3 Annual averages of the global mean sea level (mm). The red curve shows reconstructed sea level fields since 1870; the blue curve shows coastal tide gauge measurements since 1950 and the black curve is based on satellite altimetry. Error bars show 90% confidence intervals.

26. Inlets modify the local sand flow Source: Hayes & Michel, 2008

28. Beach nourishment

30. The beach slope changes with season http://www.scielo.br/img/revistas/bjoce/v56n4/a01fig03.gif

31. Sediment Supply • Source material affects composition of beach sediments • Volcanic sands • Calcareous (shell) materials • Quartz sand • Heavy minerals

32. Sediment Classification Source: Hayes & Michel, 2008

33. Beach sediments • Coarser sediments on-shore, with finer sediments off-shore (role of waves) • Beach sand can vary from high to low tide and up and down the beach.

34. Activity • Secrets of Sand

35. Most Florida beaches are sandy… • But we do have some rocky beaches nearby, where the Anastasia formation (coquina rock) is exposed. • The Anastasia formation extends from St Johns County to Palm Beach and consists of whole or broken shells, cemented together by calcium carbonate or iron oxide; formed when the sea level was 25 feet higher than present

36. Cross-section of a beach