Introduction

While the deep waters of the open ocean move under the influence of the global heat engine, the shallow waters of the estuary and continental shelf respond quickly to local and regional winds, to freshwater discharge from rivers, and to the interaction of the tide with the complex shape of the bottom topography. The circulation of the estuary depends, in particular, on the mixing of fresh and salt water, mixing from turbulent motion created by the tide and the winds. Some of the key circulations in the estuary and on the continental shelf can be simulated with simple laboratory experiments. The real estuary and shelf can be observed with instruments and sonars placed on buoys or on the ocean bottom. Scientists, Dr. Bill Boicourt, explained how Coastal Ocean Observing Systems, such as the Chesapeake Bay Observing System (CBOS; www.cbos.org) can relay data and information back to users via the Internet in real-time. Teachers can use information from field experiments and real-time data from observing systems to compare data taken from shipboard (discrete) with those posted on the internet from observing systems (continuous) to assess vertical and horizontal movement in estuaries. Effects of the ocean on local weather can investigated through activities designed for the classroom.

Introduction Activity - Discrete vs. continuous data comparison

J. McDonnell
http://www.coolclassroom.org/cool_projects/lessons/miniunits/lesson1

Focal question: How do scientists measure circulation?

Objective: Students will be able to explain the difference between discrete vs. continuous data.

Background

How we collect and use information is changing. Ocean scientist used to go out on ships and take data points at specific locations and extrapolate to a larger scale, both in time and space. Meteorologists would study day-old weather maps to predict storms such as hurricanes or tornados. Today, scientist have the added benefit of information that's no more than a few seconds old (e.g. real-time) and is telecast via satellite to computers and posted on the Internet.

On the Internet, real-time doesn't always mean data available the moment they are collected. Rather, real-time data are updated on a regular basis and frequently changes. For example, weather satellite images updated every hour are still referred to as "real-time data." At first, the distinction among real-time data, near real-time data and archived data may not be clear. However, as you continue to explore these resources, this difference will be become easier to understand.

The purpose of this activity is to help you explain to your students the difference between discrete (snapshots) and continuous and real time data.

Materials

Computers with Internet access
Projector (optional)
Student hand-outs

Procedure

1. Access the COOL Classroom Web site at http://www.coolclassroom.org/cool_projects/lessons/miniunits/lesson1.html
2. Take a look at the series of photographs and attempt to determine what has happened based on the information available to you.
3. Have students complete student worksheet.
4. Discuss results with the class.

Worksheet: Discrete and Continuous Data

1. Write a description (frame by frame) of what you think the girl in the pictures is doing.
2. Watch the video clip and write a description of what the girl actually did.
3. Does the story you deduced from the still photographs match what happened in the video?
4. Which method gave you more information about what she was doing?
(circle one)    A. Photographs    B. Video

Science Overview

Topic: Motion in the Coastal Ocean: Freshwater, Winds, and Tides

Dr. William Boicourt Education: 1973, Ph.D., The Johns Hopkins University, Physical Oceanography 1969, M.A., The Johns Hopkins University, Physical Oceanography 1966, B. A., Amherst College, Physics Position: Professor What I do: Investigate physical circulation in coastal waters

Classroom Activities

Local Weather and the Ocean
L. Murray

Objective: Participants will be able to assess how the ocean affects local weather patterns

Focal Question: How do coastal ocean movements affect local weather patterns?

1. Go to NOAA's NOWCAST    http://nowcoast.noaa.gov/

2. Click on map. Find the Select menu and choose:

- Mid-Atlantic under Location
- Meteorological under Information
- Air Temperature under Variable
- Under the Map Layer icon, activate the air and sea surface temperatures.
(Note: be sure to enable pop-ups on your computer)

3. Find air temperatures for the following locations:

4. Which area's air temperature was the closest to the ocean temperature in the mid-Atlantic region?

5. Now find yesterday's air temperature for the three cities from www.weather.com. Enter the city and state
Click on yesterday's weather.

7. Which city had the greatest change in temperature?

8. What affect does the ocean have on local temperatures?

9. What differences might be expected in winter?

10. Explain why the ocean affects local weather patterns.

Classroom Activities

Density-Driven Currents
L. Murray, W. C. Boicourt and A. Kelley

Objective: To demonstrate density differences in ocean and coastal waters, and how these differences drive currents

Powerpoint - The Coastal Ocean: Estuaries and Continental Shelves

Background

Circulation in estuaries and oceans depends in part on differences in density of the waters. Water with more salt is heavier and sinks while fresher water is lighter and "floats" on the surface. These buoyancy differences result in the separation of water into layers (stratification) within an estuary or coastal ocean. Stratification can be disrupted by heating and cooling of surface waters and/or by wind-generated water movement like waves and currents. The primary source of fresh water in estuaries and coastal oceans is from rivers coming from land with a rating of 0-5 practical salinity units (PSU), while salt water is from the open oceans and has a rating of 32-35 PSU. In this simulation we will observe what happens when simulated river water (clear) is mixed with simulated ocean water (dyed blue).

Materials

Glass or clear plastic tank (example 10 gallon aquaria)
Blue food coloring
Water
Salt (kosher salt works best)
Straw
Worksheet

Procedure

Part 1

1. Measure 1 liter of tap water (to simulate river water) into a beaker or similar vessel.
2. Repeat this step, except to this second beaker, add blue dye (to simulate ocean water) and add 10 grams of table salt.
3. Set up tank with a divider in the middle (see below for instructions). The divider should be cut to fit the width of the aquarium. Use ¼ inch durable plastic or glass.
4. Slowly pour the "river" water into one side of the demonstration tank and the ocean water (blue) to the other side. Fill tank about half full and remove the divider. Observe.
5. Record observations on the worksheet.

Part 2

1. Blow on the surface of the water through a straw.
2. Record observations on the worksheet.
(For directions on tank construction and full CD-ROM on this lesson, please email us at: murray@hpl.umces.edu )

Worksheet: Density-Driven Currents

Part 1
After adding the fresh and salty water to the tank:
1) Which water had a higher density?
2) What happened to the two water masses?

Part 2
After blowing on the surface of the water through a straw:
3) What happens to the two layers of water?
4) What happens when the wind stops?
5) How does this apply to the real world in coastal waters?

Field Trip

Is the Water Moving?
Testing the Horizontal Water Movement
L. Murray, A. Kelley, L. Spence

Objective: Students will analyze horizontal water movement in an estuary using drifters.

Materials

- Access to water
- Method of marking off given distance (e.g. on land or boat)
- Bottle drifters with string attached (e.g. Pop bottle with filled with sand so that the bottle floats just below the surface of the water)
- Student worksheets

Procedure

1. Measure a known distance along a stationary location (e.g. shoreline, anchored boat). Select a starting point and mark it as point A. Measure a know distance along a parallel axis to the water to point B (should be at least 15 meters). Record distance.
2. Drop bottle drifter with attached string in the water at Point A.
3. Use timing device to record time it takes for the bottle to move to point B.
4. Use the worksheet to determine the speed of the current.

Worksheet -  Drifter Track Data

Station:
Team:
Date:

Field Trip

Density: Vertical water movement

Objective: Participants will investigate first-hand the vertical mixing of waters in an estuary.

Background

Estuaries and oceans are natures examples of how different water densities separate. When scientists conduct vertical profiles through a water column, they can determine if there is mixing of top water and bottom water through analysis of temperature, salinity and oxygen readings through the vertical gradient. If these parameters are the same throughout the depth of the water column, then the water is well mixed. However, if there are differences (e.g. more dense, cooler higher salinity, water toward the bottom) from top to bottom, then the water column is termed stratified, or not well mixed. Whether or not the water column is mixed or not has strong implications for organisms living in this environment. For example, the main source of oxygen to bottom water is from mixing with surface water, which is in direct contact with the air. If there is no mixing, oxygen is depleted from the bottom water and organisms will either move or die.

The purpose of this field investigation is to determine if estuarine water is mixed or stratified through vertical measurements of temperature, salinity and oxygen. In a companion activity (Density Webquest), we will compare these field data with those data from observing systems (Discrete vs. continuous data comparison) and assess the advantages and disadvantages of the two methods of data collection.

Materials

Boat
YSI instrument
Data sheet
Internet connection

Procedure

1. Select a station in a coastal waterway (Choptank River) with a depth of at least 15 meters and record latitude and longitude. Observe weather conditions and record on data sheet.
2. Using an instrument that measures salinity, temperature and oxygen, lower the probe through the water column taking measurements at 2 meter intervals.
3. Record salinity, temperature and oxygen in the data sheet provided.

Questions

1. Was the water column mixed or stratified?
2. Explain your answer.

Data Sheet for Vertical Mixing Field Trip

Station:___________________________
Latitude:__________________________
Longitude: _______________________
Weather: _________________________
Group: ___________________________
Date: ____________________________

Classroom Extension Activities

Density Webquest
L. Murray and J. McDonnell

Objective: Students will determine vertical mixing in coastal waters from observing system data.

Materials

Computers with internet connection

Procedure

1. At your computer, go to the website: http://www.chesapeakebay.net/status/wquality/interpolator/do/gallery.htm

2. Click on "salinity gallery" and then click on "make selection: and choose the latest salinity profile summary (e.g. July 2006).

3. View the bottom panel for differences in top and bottom salinities along the Chesapeake Bay.
Is there a difference in surface and bottom salinity measurements?
What are these differences?

4. Repeat the above for spring (March) and fall (October).
Are the differences less pronounced or more pronounced?
Explain your answer.

5. Now compare these estuarine salinity data to real-time data from the Gulf of Maine. Go to http://gomoos.org/
Click on "Hourly Data". Select a station near shore (e.g. Station D) and click on it. On the right side of the screen click on "all data being measured" and scroll down to temperature and then to salinity. Record your observations.
surface salinity ___________________________________________
surface temperature ______________________________________
bottom salinity __________________________________________
bottom temperature _____________________________________

6. What other information can you obtain from the observing system?

Comparison of results from the field trip to real time data available from Observing Systems.

1. Which method of data acquisition provided a more comprehensive view of vertical mixing/stratification at the time of sampling?

2. Which method provided a better long term analysis of mixing/stratification over time?

3. Which method would you use if:
a. You wanted to know if the water in the estuary was stratified at a certain depth?
b. You wanted to predict if there was going to be a turn-over event in the river?
c. You wanted to see if there might be a fish kill caused by low oxygen bottom

4. Can you think of at least one advantage and one disadvantage of the observing sites continuous data collection?
Advantage
Disadvantage

5. Can you think of at least one advantage and one disadvantage of the discrete data collection from the field?
Advantage
Disadvantage