OC 201e – Introduction to Oceanography
1 of 7
Lab 3 – Density, mixing and stratification
In this lab you will explore on a small scale the influence of temperature, salinity and mixing on
seawater stratification. The
...
OC 201e – Introduction to Oceanography
1 of 7
Lab 3 – Density, mixing and stratification
In this lab you will explore on a small scale the influence of temperature, salinity and mixing on
seawater stratification. These same processes operate in the ocean over much larger scales and
have far-ranging physical, chemical and biological implications.
Spring 2020: I realize that some of you may not be able to get to the grocery store for the
supplies need for this lab. Therefore, I will provide you with pictures and videos of the activities
described below. They can be found on my science Instagram account @oceans_past
You will need to log in with either a Facebook or Instagram account.
Now, if you can get the supplies please try these activities/experiments. There is no pressure
now so it should be fun, especially if you involve the people you live with.
HINTS:
1. Density is controlled by temperature and salinity. Cold salty water is more dense than
warm, fresh water.
2. A stable water column (i.e., stable stratification) is less dense water over more dense
water.
Lab Supplies: Table salt (lots), food coloring/dye, eyedropper, spoon, 2 large clear water
glasses, and ice cubes made from both plain and dyed freshwater.
Lab Set-up: Make your own saltwater by mixing salt into water – you don’t need to be
delicate with this because the saltier it is the better it will perform in the lab.
Approximately 2 tablespoons of salt in 1 liter of water will give you “typical” seawater
(i.e., a salinity of 35). You will need at least 2 liters of saltwater, but I suggest making
extra. Also, for some of the experiments you require cold salt water (the colder the
better). I would place at least 1 liter of salt water in the freezer for about 20 minutes
before you try Activity 4.
Activity 1: Salt water with dye (6 pts)
In this activity, you will explore the role of mixing on water mass interaction.
Materials: Freshwater at room temperature, cold saltwater and food dye
Preparation: Fill a large glass with the room temperature freshwater.
In a separate container add food dye to a small amount of cold saltwater.
Part 1 – Answer part “i” below before doing the following:
Using an eyedropper, drop a single drop of dyed saltwater into the freshwater at a time.
Try from very near the surface so that the drop does not enter the water going fast.
Next, try from higher up. Observe the mixing
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