## Lab 5.2 – What is the relationship between temperature, salinity, and density?

The major water masses of the Atlantic Ocean.

Estimated time to complete: 30-60 minutes
Materials needed: None

There is a complex relationship between temperature, salinity, and density. Water stratification is when water masses with different properties form layers that act as barriers to water mixing. These layers are arranged according to density, with the less dense water masses sitting above the more dense layers. In this activity you will analyze the relationship between temperature, salinity, and density during the months of April and October in the North Atlantic.

Below you are able to see a dataset of temperature and salinity at the Coastal Pioneer Array for the months of April and October. You can interact with the data by:

• Select the month to view from the “Select Month” menu below the graphs
• Clicking the profile and hovering your mouse over the profile to view temperature (left) and salinity (center) variables with depth
• Predicting the corresponding density profile (right) by clicking on the small blue circles on the dashed line and changing the corresponding density
• Checking your prediction by clicking the button at left of “Show Density” below the density profile.

Before comparing your prediction to the calculated density profile, answer the Quick Check Questions and Interpretation Questions 1 and 2.

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### Interpretation Questions:

1. From 0 to 100 dbar, should the density profile look more like the temperature profile or the salinity profile for the month of April? October? Explain your answer choices.
2. Beginning at 100 dbar, should density increase or decrease with depth for both months? Explain your answer choice.
3. Describe the approach or steps you took in predicting the shape of the density profile you “drew”.
4. How do the density profiles you drew differ from the calculated density profile for each month?
5. What is the depth range (in dbar) of the pycnocline in October?

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