Activity3part2-2
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University of California, Santa Barbara *
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Geography
Date
Jan 9, 2024
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4
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Geography 3 - Ocean and Atmosphere - Fall 2023 - Prof. Tim DeVries
Activity 3: Salinity, waves, and tides (Part 2: Analysis)
Purpose
In this activity you will analyze your observations from last week, to learn more about
the variations in salinity, waves, and tides along our coastline, and what factors affect
them.
Materials
•
Optical refractometer
•
1 seawater sample (obtained last week)
•
Computer with internet connection
Part A: Salinity and density
1. Obtain an optical refractometer, and instructions on its use, from your TA. Note that
the refractometer measures specific gravity, rather than density. To obtain density,
multiply the specific gravity by the density of pure water (1000 kg/m
3
). Measure the
salinity and density of your water sample(s). Record the values below for your
samples. (Salinity in ppt, density in kg/m
3
).
33 ppt 1025 kg/m ^3
2. Why might the density value that you measured be different from the density
value
of your sample when you took it (i.e. what factors might have caused a
change in
the density of your water sample). List 2 potential causes.
The water was a lot cooler
than when we initially sampled it. Another factor could also be the wrong instruments
used to measure the total density of the water.
3. What was your sampling location (lagoon, campus point across from lagoon, or
campus point across from Anacapa housing)? Write down your group’s average
salinity and density at your sampling location on the board at the front of the class.
My sampling location was Campus Point across the lagoon
4. After everyone has written down their average salinity and density for their group’s
sampling location on the board, compare the salinity for all three locations. Which
location had the highest salinity? Which had the lowest? Is there any variability in
salinity from one location to another and if so what might be causing that?
The samples from all three locations were all the same, making there to be no
variability in any of the locations.
5. Which location had the highest density? Which had the lowest? What might be
causing variability in density from one location to another?
Geography 3 - Ocean and Atmosphere - Fall 2023 - Prof. Tim DeVries
The lagoon has the highest density because the water has more evaporation leaving
the water to become more dense.
Part B: Tides
1. Go to the NOAA (National Oceanographic and Atmospheric Administration) tide
predictions website for Santa Barbara at
https://
tidesandcurrents.noaa.gov/noaatidepredictions.html?id=9411340
. Navigate to the
date of your observations. What was the tide height at the time of your observations
last week? Was the tide coming in or going out? Were your observations accurate?
2. What was the time and water height of the highest tide on the day of your
observations? What was the time and water height of the lowest tide? What was
the range (high minus low)?
The highest was 5.25 feet at 7:48 pm. The lowest is
-0.07 ft at 1:29 am.
3. Go to the website
https://moon.nasa.gov/moon-in-motion/tides/
and view the
animations and explanations. Explain why there are two low tides and two high tides
per day (for most places on Earth, including Santa Barbara).
There are two low tides and
two high tides because tides are primarily caused by the gravitational pull of the Moon and the
Sun on Earth's oceans. The interaction between these gravitational forces and the Earth's
rotation leads to the formation of two high tides and two low tides each day in most coastal
areas. The combination of the Moon's gravitational pull, the Sun's gravitational pull, and the
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