OC201_Desha,Lab4_Drifter_Circulation
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Oregon State University, Corvallis *
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201
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Geography
Date
Dec 6, 2023
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OC 201, Oceanography
Lab 4: Using Drifters to Study Ocean Surface Circulation
Part 1: North Pacific Gyre Circulation
Since the dawn of human civilization, people have thrown objects into the
water to see where the currents would take them (the old “note-in-a-bottle
trick”). We continue to do the same thing with more sophisticated, high-tech
tools called “drifters.”
The figure below shows an example of a surface
drifter. They are released into the ocean by ships or planes, float with the
surface currents, and take measurements of the water with built-in
instruments. They are tracked by satellites and transmit data several times a
day. The floats on the drifter keep it at the surface and hold an antenna for
sending data to the satellite. Metal vanes extend below the surface and
cause the drifter to move with the surface currents instead of the wind.
Figure 1. Surface drifter.
Open the Excel file called “OC201_W2022_Lab4_DrifterData.xlsx” found on
Canvas in week 4.
This file contains “fix” data from 3 separate drifters:
#12410, #15022 and #22217.
A fix is when a satellite receives a particular
transmission and relays it to a land-based data center. Shown are the date of
a “fix”, the time between successive fixes in days, and seconds, the latitude,
and longitude of the fix.
1.
Use the latitude and longitude data in the file to plot the position of each
buoy location during the year on Figure 2. Then connect the locations with
lines and draw an arrow to show the direction of motion. (You can use the
Draw function of Word to do this or the Paint app on your computer)
(12pts – 4 pts per drifter)
Remember that by convention, “East” longitudes are given positive values
and “West” longitudes are given negative values (e.g., drifter 15022 is in
the western Pacific).
Don’t
worry about getting the exact location of the
fixes – we’re just looking for general patterns.
NOTE: West longitudes are to the right of the red 180-degree line.
East lines are to the left.
Longitudes are positive
Date line
Longitudes are negative
Figure 2. Map of the North Pacific Ocean for plotting buoy data.
2.
Refer to a map of surface currents (in lecture notes or on the web). What
are the names of the surface currents that moved the drifters whose
paths you plotted? (6 pts – 2 pts each)
Buoy 12410: California
Buoy 15022: North Equatorial
Buoy 22217: Alaska
3.
The currents plotted above are all part of the North Pacific Gyre, a
clockwise-moving current in the North Pacific. (6 pts – 3 pts each)
a.
What is the name of the current that moves past the Oregon coast?
North Pacific & California
b.
Do you think it carries warm or cold water past our coast?
Why?
Cold because the water is coming from the North.
4.
Now open the web site
http://www.gpsvisualizer.com/calculators
You will be using the second part of this app to calculate great circle
distances between your drifter data “fixes”.
Go to the section that says,
“Calculate the great circle distance between two points.”
Enter in the first
fix (30.1, -123.7) in the upper box and the second fix (27.5, -121.8) in the
lower box and press distance.
Repeat to fill in the tables. Then, calculate
the average speed for each drifter (note: you will need to perform unit
conversions in excel to make sure your units are consistent).
Round your
speed to 1 decimal place. (18 pts)
Using Excel, calculate the average speed in cm/s for each drifter.
To do this
you’ll need to convert distance traveled from km to cm. Recall that there are
1000 m/km and 100 cm/m.
It is easy to do this in Excel.
Copy and paste the average drifter speed for each drifter and the average
for all three below.
You will also hand in your excel spreadsheet with
your lab report.
Average speed for buoy 12410: 18.25
Average speed for buoy 15022: 29.93
Average speed for buoy 22217: 10.61
Mean speed for all three buoys: 19.59
5.
Now describe how the speeds vary (8pts)
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a)
along each of the drifter tracks
The speeds vary between the buoy 12410, as It seems to be the most
average between the three drifters. We see it slowly pick up and slow
down throughout its time, however it never reaches past 28 cm/s. It
fluctuates steadily between 12 – 21 then sparks up to 27 and drops as
low as 9. This could tells us that there was a storm.
For buoy 15022, this was the highest speed as it went all the way up to
59. We see this is a lot faster than all the other buoys. It stays pretty
high throughout its time other then a significant drop to 8.n
Lastly, we see buoy 22217, with an average speed pf 10.61, this was the
slowest speed out of the three as it stayed between 8-20 cm/s
throughout its course.
b)
between the drifters
The speeds vary between the buoy 12410, as It seems to be the most average between the three
drifters. We see it slowly pick up and slow down throughout its time, however it never reaches
past 28 cm/s. It fluctuates steadily between 12 – 21 then sparks up to 27 and drops as low as 9.
This could tells us that there was a storm.
For buoy 15022, this was the highest speed as it went all the way up to 59. We see this is a lot
faster than all the other buoys. It stays pretty high throughout its time other then a significant
drop to 8.n
Lastly, we see buoy 22217, with an average speed pf 10.61, this was the slowest speed out of the
three as it stayed between 8-20 cm/s throughout its course.