(Discussion – The Ocean in Motion: Tides) Wednesday, January 31, 2018 (Discussion – The Ocean in Motion: Tides)

Describe how a wave “breaks.” The Launch Pad Wednesday, 1/31/18 1/1 Describe how a wave “breaks.” As a wave approaches the shore, its energy is squeezed into a smaller and smaller space vertically. The water at the bottom of the wave slows down due to friction from the sea floor. Now, the water at the top of the wave is moving faster than the water at the bottom and the wave falls forward.

Remediation for Quiz 10 runs through Friday! Announcements Remediation for Quiz 10 runs through Friday!

Summative or Formative # Assignment Summative or Formative # Date Issued Gone Missing Day Last Day Accepted QUIZ 10 S1 1/26 Friday

Discussion - The Ocean in Motion Tides REMINDER: All slides regarding the oceans are on the class website in two separate PowerPoints: The Hydrosphere - Seawater and Currents The Hydrosphere - Waves, Tides, and Deep Ocean Exploration

The Ocean in Motion Tides

Tides Learning Objectives What is a tide? What are the different types of tidal patterns? What causes tides? What are the different types of tides? Where is the largest tide on Earth found? What is the Saltstraumen?

Tides are important physical forces in our ocean Gravitational interactions between the sun, moon and earth are the primary causes of tides Different positions of the sun and moon create two different types of tides: spring tides and neap tides Tides play an important role in the life cycle of many marine organisms

What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth

Tidal patterns vary around the world Some places have one low tide and one high tide per day (diurnal tides) Other places have two high and low tides per day approximately equal in size (semidiurnal tides) If the two high and low tides of a semidiurnal tide are unequal in size, they are call mixed semidiurnal tides The US has examples of semidiurnal tides (East Coast), diurnal tides (some areas of the Gulf of Mexico) and mixed tides (Pacific Coast) For complete technical accuracy, the type of day referred to in the definitions for diurnal, semidiurnal, and mixed (semidiurnal) tides is a lunar day (also referred to as a tidal day). A lunar day is 24 hours and 50 minutes compared to the typical solar day which is 24 hours. It refers to the time required for a spot on earth to make a full rotation from a specific location under the moon to the same location (under the moon). For a more in depth explanation of a lunar day, see http://oceanservice.noaa.gov/education/tutorial_tides/tides05_lunarday.html (Accessed, May 2011).

Tidal extremes: The Bay of Fundy The Bay of Fundy in Canada is known for its large tidal range (differences of over 50ft have been recorded!) Photo: NASA Photo: http://earthobservatory.nasa.gov/IOTD/view.php?id=6650; Accessed: November 2010

Tidal extremes: The Bay of Fundy The Bay of Fundy in Canada is known for its large tidal range (differences of over 50ft have been recorded!) Low tide High tide Photo: NASA Photo: http://earthobservatory.nasa.gov/IOTD/view.php?id=6650; Accessed: November 2010

What causes tides? The gravitational pull of the sun and the moon causes “bulges” on Earth that move as we rotate Gravitational pull “Bulge” of Earth Sun Earth Moon Teacher’s Note: The slide labels the gravitational pull and bulge of the Earth as you advance the slide.

What causes tides? The tide rises when coastline enters the bulge and falls when it rotates out High tide

Different types of tide Sun Earth Moon Spring tides occur when the sun and moon are in a straight line The tidal range is typically highest during spring tides

Different types of tide Earth Neap tides occur when the sun and moon form a right angle with Earth Low tides are typically higher and high tides are lower Why is the moon’s pull greater than the sun’s? Teacher’s Note: Even though the sun is larger than the moon, the moon’s pull is always greater because the moon is much closer to the earth. Sun Moon

Figure 1: Tide predictions for Dauphin Island, 3/1/11 Water Level (ft) Figure 1: Shows tidal predictions for Dauphin Island, AL 3/1/11 Local Standard Time (LST) – Data comes from station 8735180 (http://tidesandcurrents.noaa.gov/noaatidepredictions/viewDailyPredictions.jsp?Stationid=8735180) Y-axis shows water levels in feet and x-axis shows time in hourly increments over the course of a day What time does the first low tide occur? (8:00 a.m.) What time does the first high tide occur? (8:00 p.m.) How many high tides and low tides occur? (one high tide and one low tide) What type of tide do you think this is? (Diurnal) Time

Figure 1 shows a diurnal tide: one high and one low tide First high tide ~8pm Water Level (ft) Figure 1: Shows tidal predictions for Dauphin Island, AL 3/1/11 Local Standard Time (LST) – Data comes from station 8735180 (http://tidesandcurrents.noaa.gov/noaatidepredictions/viewDailyPredictions.jsp?Stationid=8735180) Y-axis shows water levels in feet and x-axis shows time in hourly increments over the course of a day What time does the first low tide occur? (8:00 a.m.) What time does the first high tide occur? (8:00 p.m.) How many high tides and low tides occur? (one high tide and one low tide) What type of tide do you think this is? (Diurnal) First low tide ~8am Time

Figure 2: Tide predictions for Woods Hole, MA, 8/25/10 Water Level (ft) Figure 2: Shows tidal predictions for Woods Hole, MA 8/25/10 Local Standard Time (LST) – Data comes from station 8447930 (http://tidesandcurrents.noaa.gov/noaatidepredictions/viewDailyPredictions.jsp?Stationid=8447930) Y-axis shows water levels in feet and x-axis shows time in hourly increments over the course of a day How many high tides are present? (2) What times do they occur? (~9:00 a.m. and ~9:00 p.m.) How many low tides are present? (2) What times do they occur? (4:00 a.m. and 4:00 p.m.) What is the tidal range (distance between high and low tide) for first high and low tide (round to nearest foot)? (2 feet) What is the tidal range for the second high and low tide (round to nearest foot)? (2 feet) What type of tide is this? (Semidiurnal – 2 high and low tides of about equal heights) Time

Figure 2 shows a semidiurnal tide: two high and low tides of equal heights First high tide ~9am Second high tide ~9pm Tidal range 2ft Tidal range 2ft Water Level (ft) Figure 2: Shows tidal predictions for Woods Hole, MA 8/25/10 Local Standard Time (LST) – Data comes from station 8447930 (http://tidesandcurrents.noaa.gov/noaatidepredictions/viewDailyPredictions.jsp?Stationid=8447930) Y-axis shows water levels in feet and x-axis shows time in hourly increments over the course of a day How many high tides are present? (2) What times do they occur? (~9:00 a.m. and ~9:00 p.m.) How many low tides are present? (2) What times do they occur? (4:00 a.m. and 4:00 p.m.) What is the tidal range (distance between high and low tide) for first high and low tide (round to nearest foot)? (2 feet) What is the tidal range for the second high and low tide (round to nearest foot)? (2 feet) What type of tide is this? (Semidiurnal – 2 high and low tides of about equal heights) Second low tide ~4pm First low tide ~4am Time

Figure 3: Tide predictions for Seattle, WA (Puget Sound), 5/1/11 Water Level (ft) Figure 3: Shows tidal predictions for Seattle, Washington (Puget Sound) 5/1/11 Local Standard Time (LST) – Data comes from station 9447130 (http://tidesandcurrents.noaa.gov/noaatidepredictions/viewDailyPredictions.jsp?Stationid=9447130) Y-axis shows water levels in feet and x-axis shows time hourly increments over the course of a day How many high tides are present? (2) What times do they occur? (~4:00 a.m. and ~6:00 p.m.) How many low tides are present? (2) What times do they occur? (11:00 a.m. and 11:00 p.m.) What is the tidal range (distance between high and low tide) for first high and low tide (round to nearest foot)? (10 feet) What is the tidal range for the second high and low tide (round to nearest foot)? (4 feet) What type of tide is this? (Mixed Semidiurnal – 2 high and low tides of unequal heights) Time

Figure 3 shows a mixed semidiurnal tide: two high and low tides of unequal heights Second high tide ~6pm First high tide ~4am Tidal range 4ft Tidal range 10ft Second low tide ~11pm Water Level (ft) Figure 3: Shows tidal predictions for Seattle, Washington (Puget Sound) 5/1/11 Local Standard Time (LST) – Data comes from station 9447130 (http://tidesandcurrents.noaa.gov/noaatidepredictions/viewDailyPredictions.jsp?Stationid=9447130) Y-axis shows water levels in feet and x-axis shows time hourly increments over the course of a day How many high tides are present? (2) What times do they occur? (~4:00 a.m. and ~6:00 p.m.) How many low tides are present? (2) What times do they occur? (11:00 a.m. and 11:00 p.m.) What is the tidal range (distance between high and low tide) for first high and low tide (round to nearest foot)? (10 feet) What is the tidal range for the second high and low tide (round to nearest foot)? (4 feet) What type of tide is this? (Mixed Semidiurnal – 2 high and low tides of unequal heights) First low tide ~11am Time

The Saltstraumen https://www.youtube.com/watch?v=Ci-uwzFIsgE The Saltstraumen has the strongest tidal current in the world. Up to 520,000,000 cu. yd. of seawater forces its way through a 1.9 mile long and 490 foot wide strait every six hours, with water speeds reaching 25 mph. Vortices known as whirlpools (or maelstroms) up to 33 feet in diameter and 16 feet in depth are formed when the current is at its strongest. The Saltstraumen has existed for about two to three thousand years. Before that, the area was different due to post-glacial rebound. The current is created when the tide tries to fill the Skjerstadfjorden. The height difference between the sea level and the fjord inside can be up to 3 ft 3 in. When the current turns, there is a period when the strait is navigable. https://www.youtube.com/watch?v=Ci-uwzFIsgE

A tide is the periodic rise and fall of a body of water. Tides Summary What is a tide? A tide is the periodic rise and fall of a body of water.

What are the different types of tidal patterns? Tides Summary What are the different types of tidal patterns? diurnal tides - one low tide and one high tide per day semidiurnal tides - two high and low tides per day approximately equal in size mixed semidiurnal tides - two high and low tides of unequal size

Tides What causes tides? Summary What causes tides? Tides are caused by the gravitational pull of the sun and the moon that cause “bulges” on Earth. The tide rises when coastline enters the bulge and falls when it rotates out

What are the different types of tides? Summary What are the different types of tides? Spring tides occur when the sun and moon are in a straight line Neap tides occur when the sun and moon form a right angle with Earth

Where is the largest tide on Earth found? Tides Summary Where is the largest tide on Earth found? The Bay of Fundy in Canada is known for its large tidal range (differences of over 50ft have been recorded!)

Tides What is the Saltstraumen? Summary What is the Saltstraumen? The Saltstraumen has the strongest tidal current in the world.