Investigating Water Temperature

Research Question: How does temperature affect ocean water? Specifically, how does the temperature of a purple solution (hot vs. cold) affect the movement of the purple solution through room temperature water?

In our quest to better understand ocean currents, we investigated the effects of temperature on the motion of fluids through water. Students set up and performed a controlled experiment that tested the movement of hot vs. cold potassium permanganate solution (aka, "purple stuff") in columns of room temperature water. Watch as one group of students performs a trial (hot on the left, cold on the right):

Based on the experiment, ponder the following questions:

• How does temperature affect ocean water?
• How does temperature affect the way water moves?
• Which is more dense, hot water or cold water? What evidence from the experiment do you have to support your answer?
• How might uneven solar heating of the Earth (equator vs. poles) cause ocean currents?
• How do you think ocean currents affect global weather and climate?

To better appreciate how and why scientists monitor and study ocean circulation, explore NASA's Aquarius Mission website, which has many excellent animations such as the one below:

Tracking Ocean Currents

NOAA Global Drifter Program: Drifter Buoy

The task is simple: "Your job is to design and draw a device to track ocean currents."

As we've been studying different aspects of ocean currents — causes, movement, etc. — it's a worthwhile endeavor to think about the instruments used to track ocean currents. A major component of How Science Works includes gathering data, and I think it is important for students to consider the myriad challenges scientists face when tasked to collect a particular type of data, such as ocean currents. I, therefore, ask students to design a device that could track ocean currents and share their design with the class (How Science Works, "publication," "discussion with colleagues," and "feedback and peer review").

The designs are always innovative, creative, thoughtful, and reasonably practical. The best part of this activity is comparing student designs with actual ocean tracking devices used by NOAA and seeing the overlap.

NOAA's Global Drifter Program utilizes drifter buoys to track ocean currents around the world:

"The modern drifter is a high-tech version of the "message in a bottle". It consists of a surface buoy and a subsurface drogue (sea anchor), attached by a long, thin tether. The buoy measures temperature and other properties, and has a transmitter to send the data to passing satellites. The drogue dominates the total area of the instrument and is centered at a depth of 15 meters beneath the sea surface."

Students are delighted to see that many of the ideas they developed in class are actually used in the drifter program. We discuss similarities and differences between their designs and NOAA's drifters to better understand the challenges and limitations involved in measuring ocean currents.

The design activity is followed up with a tracking activity that uses data from NOAA's drifter buoys to track the flow of global ocean currents. Students discover that currents in the Pacific Ocean flow in a giant, clockwise gyre at a fairly slow, but steady rate; in the process, large quantities of heat are redistributed around the planet.

It's easy for a teacher to have students just learn factual information about currents from a textbook, but that's like eating processed junk food—it provides little in the way of long-lasting nutritional value (i.e., shallow learning). US science organizations such as NOAA, NASA, and USGS provide valuable data and information that is perfect for an inquiry-based science classroom. These organizations are the primary sources of science discovery and exploration on planet Earth, and we should be leveraging their expertise in the classroom to engage our students in How Science Really Works.

---

A sampling of student designs for ocean tracking devices:

Oceanography Questions

Image Credit: Pics4Learning

I frame our science learning in terms of questions—learning goals, laboratory research questions, daily warm-up questions, one-on-one student conversations, etc. Questions stimulate thinking and conversation; the more questions, the better. I am famously known for never giving students "the right answer," but always asking them that one additional question. Of course, my favorite question is, "Why?"  :)

Throughout the school year, I will share some of the questions we ponder as we engage in the process of science. Here is a sampling of some of the "big idea" questions that I pose during our study of physical oceanography:

Water Cycle

• How is water distributed on planet Earth?
• How does water cycle through the Earth system?

Ocean Structure and Composition

• What are the structures and physical characteristics of Earth's oceans?
• How far does each ocean zone extend?
• What are the temperatures like in each ocean zone?
• How does color change as you descend deeper in the ocean?
• How far below the surface does light penetrate?
• How does pressure change with ocean depth?
• How do scientists create maps of the ocean floor?
• What is the composition of ocean water?
• What is the average salinity of the world's oceans?
• What are the factors that cause changes in salinity?
• How do scientists measure salinity?
• What factors affect the density of ocean water?

Ocean Circulation

• How does density affect ocean circulation?
• How and why does ocean water circulate?
• How do scientists measure ocean circulation?
• What types of ocean waves occur?
• What are the causes of different types of ocean waves?
• How do tsunami waves form?
• How do scientists track tsunami waves and inform the public?
• How do tidal waves work?

---

For more information about effective questioning:

Ivan Hannel, Insufficient Questioning, Phi Delta Kappan, Vol. 91, No. 3, November 2009, pp. 65-69. In this article, author Ivan Hannel discusses how highly effective questioning can keep students interested and improve their learning.

Bathymetry in 3D

NOAA Portsmouth Harbor Bathymetry

Using depth data collected from sonar measurements, oceanographers create bathymetric charts showing physical features of the ocean floor. During our physical oceanography studies, students create both two-dimensional and three-dimensional bathymetric charts using depth data collected from "mystery boxes" containing models of various ocean features. During the lab activity, students complete the following tasks:

• Collect depth data in rectangular grid patterns across the mystery boxes
• Draw and colorize isobaths (lines of equal depth) to delineate areas of similar depth
• Identify names of the ocean features found inside the mystery boxes
• Create 3D surface charts from the data to finally "see" what's inside the mystery boxes

At the beginning of the lesson, students are rather daunted when I tell them they will be creating a 3D bathymetric chart. By the end of the lesson, they are quite proud of their accomplishments.

To create the final 3D bathymetric chart, students enter their data into Microsoft Excel and use the surface chart option to visualize a realistic model of their original mystery box. Just as we cannot lift the ocean to see the features below, students may never open the mystery boxes to see what's inside—they are reliant upon their data and 3D models to "see" the ocean floor.

The process for creating a 3D surface chart in Microsoft Excel (2007 and 2010 versions) is outlined as follows:

1. Type in all of the bathymetry data (including grid numbers) and select it
2. Go to Insert tab on the ribbon
3. Click "Other Charts" and select "3D Surface Chart"
4. Move Chart to "New Sheet"
5. Right-click the vertical (value) axis and choose "Format Axis"
• Change Maximum to "Fixed" and enter the maximum data value
• Change Minimum to 0 (sea level)
• Change Major Unit to "Fixed" and enter a value of 5.0 (the isobath interval)
• Check the "Values in Reverse Order" box
• Close
6. Right-click the horizontal (category) axis and choose "Format Axis"
• Check the "Categories in Reverse Order" box
• Close
7. Right-click the chart and choose "3-D Rotation"
• Use the arrows and options to adjust the chart to a nice view
• Close
8. Click the entire legend ONCE to select it. Then click ONCE on an individual color in the legend to select it by itself.
• Right-click that color and choose "Format Band"
• Experiment with either the Solid Fill or the Gradient Fill to create a nice blend of colors from deep to shallow
• Close
9. Format the rest of the chart as necessary to include items such as a descriptive title, axis labels, and a well-written caption
10. Add clip art and images to create a unique, eye-catching final style for the 3D chart

See the results below...

---