Intro to the Ocean

Learning About BeachesMaia McGuire, PhDUniversity of Florida Sea Grant Extension Program

Play Only one Ocean (Banana Slug String Band)1Only one oceanThere 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 planets surface.

Contrary to what you may have learned in school, marine educators are now trying to emphasize the connectivity between the ocean basinsinstead of calling them different OCEANS, we now refer to one ocean, with several basins.2Florida Beaches667 miles of beaches1197 miles of shorelineMore than half of Floridas shoreline is beaches

Ocean sciencesSecond 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 biologyOcean circulation

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

Water moves around the ocean for various reasons. Melting ice water in the North Atlantic ocean sinks to the ocean floor because it is cold (more dense than surface water). Deep ocean water currents circulate water from the N. Atlantic to S Atlantic, to Indian, then Pacific Ocean basins. The water warms along the way, and eventually makes its way back from the northern Pacific to the N Atlantic. The earths circulation in conjunction with prevailing wind directions creates surface currents, shown in the lower left. Many of these currents have deeper water countercurrentsif you move water from one place to another, water will come from somewhere else to fill in the gap5Focus on the North AtlanticClockwise circulation (surface currents)Gyre (Sargasso Sea) in the center

This graphic shows the primary surface water currents in the North Atlantic Ocean. You will see that they form a clockwise rotation, and may also notice that there are no currents running through the center of the N. Atlantic. In essence, the central portion of the ocean is a bit like the center of a whirlpool (or toilet bowl!)floating objects accumulate there. We call this area a gyre. You may have heard about the trash gyre in the eastern Pacific Ocean where large amounts of plastics are accumulating.6Longshore CurrentSource: Hayes & Michel, 2008

What makes water move?Water moves because of currentsTemperature can make water moveThe earths rotation makes water moveCoriolis effect results in clockwise circulation in northern hemisphere and counterclockwise in the southern hemisphere

8Zooming in on FloridaGulf has wide continental shelfLoop CurrentAtlantic has narrow shelfGulf StreamLongshore currents

Florida is influenced by three major currentsthe Loop Current in the Gulf of Mexico flows north from Central America, into the Gulf of Mexico, then loops around and flows southwards to the Florida Keys, where it becomes the Florida Current. As the water continues to flow around the southern tip of Florida, it becomes the Gulf Stream. You should be aware that the absolute position of each of these currents varies from day to day. The Gulf Stream is very close to shore in southern Florida, but is further offshore (e.g. 50 miles) by the time it reaches Jacksonville. The solid line is the 200 meter depth line, which essentially is the edge of the continental shelfnote that the shelf is very wide on the Gulf coast of Florida compared to the Atlantic coast.As we mentioned with the ocean circulation slide, when you move water in one direction, water will flow to fill the gap created, so we also have what we call longshore currentson the Atlantic coast, these generally run quite close to shore from north to south.9Continental shelf.?http://www.unfalumni.org/?p=139

Heres a graphic to show what the ocean floor looks like as we move offshore. There is a gently-sloping continental shelf which varies in width from location to location. The steep portion that connects the continental shelf to the deepwater continental rise is called the continental slope. The deepest sea floor area is called the abyssal plain.10Back 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.aspxOK, getting back to the watery side of things We cant see the currents themselves, although we can sometimes see the edge of a current because floating stuff tends to accumulate there. Fishermen are familiar with the weed line in the western Atlanticthis marks the edge of the Gulf Stream and is a good fishing spot 11What 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, 2008Were not going to spend much time on tides, but I do want to make you aware that tides result from gravitational pull of the moon and sunwhen the moon and sun are in line with the earth, we have higher ranges of tides (spring tides); when the moon is at 90 degrees to the sun, we have the lowest ranges (neap tides). There are other factors that affect the absolute range of the tides, but in general, the phase of the moon affects the range of the tides.12Tides in JacksonvilleTwo 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)

Here are tide data for Mayport. You will see that there are two low tides (in blue) and two high tides (in red) each day. If we look at the difference between high and low tides for three different dates, you will see that there are bigger ranges at the new and full moon compared to the week in between. Tide height is given relative to mean low water levelsometimes the low tides are above that point (positive values) and sometimes they are below it (negative values).13WavesMost commonly caused by wind blowing on the oceans surface.

Waves can be caused by a variety of factors, including tectonic activityearthquakes and volcanoes. However, the most common wave-producing force is wind.The graphic shows the parts of a waveyou dont need to worry about the terminology, but the shape should be familiar

14ActivityWind and waves (Monterey Bay Aquarium)Waves in a bottle

A very little ocean chemistryThe sea is saltyWhere 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).The key piece of ocean chemistry for your students is to know that the ocean is salty. Anyone who has had sea water in their mouth will know this! In fact, the ocean is about 3.6 percent salt, although we measure saltiness (salinity) in parts per thousand, not parts per hundred. These salts are important to the plants and animals that live in the ocean. Most plants and animals that live in the ocean cannot live in fresh water.The other key piece of ocean chemistry is the knowledge that oxygen from the air can become dissolved in water (just like salt can!). Most ocean animals cannot breathe in air, but they require dissolved oxygen in order to survive.16Salt water is different from fresh waterIt is heavierThings float better in salt waterWe cannot tell fresh water from salt water by looking at it

Apart from one being salty and the other being fresh, there are several differences between salt and fresh water. We cannot tell these differences by looking at two water samples, but we may be able to tell the difference by performing some simple tests on the water.17Moving onshore.The Atlantic coast of Florida is influenced by many factorssome natural, and some human.

Effect of Climate on ShorelinesWind patterns and off-shore storms affect wave size and directionPresence or absence of major rivers (amount of precipitation)Chemical and mechanical weathering (erosion) that produces sedimentsEffects of extreme weather (cold and heat)Hydrodynamic RegimeThe interaction of water in motion with the coastal sedimentsCommonly expressed as the ratio of the wave energy to the tidal energyUsed to classify depositional shorelines

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

Major Rivers of the SE U.S. CoastSource: Hayes & Michel, 2008Longshore Current

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

Longshore transport of sand

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.Sources: IPCC 2007 WG1-AR4 , Ch. 5, Fig. 5-13 &Tech. Summary section TS3.3.3Global Avg. Sea Level Observations:20th century rate: 1.7 0.5 mm/yr1993 to 2003 rate: 3.1 0.7 mm/yrthermal expansion 1.6 0.5 mm/yrchanges in land ice 1.2 0.4 mm/yrThere is high confidence that therate of sea level rise acceleratedbetween the mid-19th and themid-20th centuries based upon tidegauge and geological data.

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

Beach nourishment

The beach slope changes with season

http://www.scielo.br/img/revistas/bjoce/v56n4/a01fig03.gifSediment SupplySource material affects composition of beach sedimentsVolcanic sandsCalcareous (shell) materialsQuartz sandHeavy mineralsSediment ClassificationSource: Hayes & Michel, 2008

Beach sedimentsCoarser 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.

ActivitySecrets of Sand

Most Florida beaches are sandyBut 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 presentCross-section of a beach