Marla Crouch: Gumbi Marla and Setting Course, June 18, 2013

NOAA Teacher at Sea
Marla Crouch
Aboard NOAA Ship Oscar Dyson
June 8-26, 2013 

Mission: Pollock Survey
Geographical area of cruise: Gulf of Alaska
Date: June 18, 2013

Weather Data from the Bridge: as of 1900
Wind Speed 13.48 kts
Air Temperature 7.0°C
Relative Humidity 99.00%
Barometric Pressure 1,010.00.5 mb

Latitude:  54.31N   Longitude: 159.80W

Science and Technology Log

Another fashion statement – Gumbi Marla

Here I am, all zipped up in my immersion suit.
Here I am, all zipped up in my immersion suit.

I’ve donned an immersion suit, also known as a survival suit.  One of the first things I did when I came aboard was to locate this suit and my life vest, two pieces of equipment that save lives.  In the event we had to abandon ship, the survival suit would keep me both warm and afloat until rescue.  During our evacuation drill we needed to unpack and get into the suit, and be completely zipped up in 60 seconds or less.  Getting into the suit was much easier after I took my shoes off, as the soles caught on the fabric of the suit.  The suit is made of neoprene, which was invented in 1930.  SCUBA wetsuits are also made of neoprene, and even some laptop and tablet cases.

In an earlier blog I talked about the CTD being used to calibrate the sonar aboard the Oscar Dyson, but not all technologies on the Dyson are as high tech as the CTD and sonar equipment.  In fact you can build a weather station at home that is similar to some of the equipment used by the Dyson’s crew.  Below is a picture of a hygrometer.  There are actually two hygrometers aboard, one is located on each side of the bridge.  Hygrometers are used to measure relative humidity (how much moisture is in the air).   Also pictured is the wind bird which shows the direction the wind is moving.  The propeller was actually turning rapidly when the picture was taken.  The camera was able to “stop” the action.  The wind bird is mounted atop the jack staff, high above the bow.

Hygrometers are weather instruments used to measure relative humidity.
Hygrometers are weather instruments used to measure relative humidity.

Wind bird

The following link shows you how to build six instruments for monitoring the weather.

If you checked out the above link, how many snow days to you think the kids in North Dakota had?

Did you check out ship tracker?  If you did, the screen shot below will look familiar.  The blue lines in the water display the Dyson’s course.  Each segment of the course is called a transect.  Transects are numbered, enabling scientists to easily reference a location.

Oscar Dyson's course as of 6 18 13
Oscar Dyson‘s course as of 6 18 13

Are you wondering why we have traveled in rectangular patterns?  The scientists establish this course for a several reasons:

  1. Transects run perpendicular to the coast line, covering a wide range of bathymetry over the shortest distance.
  2. Regularly spaced transects (as opposed to randomly spaced or scattered) are correlated with historical data, and are the best way to describe the distribution of pollock.
  3. The combination of transects collects sufficient data to allow scientists to estimate the overall size of the pollock population with a high degree of certainty.

Does anyone have an idea about the meaning of “bathymetry” and a “leg”?  No, in this case a leg is not something you stand on.  Bathymetry is the shape and depth of the ocean floor, and a bathymetry contour line on a chart connects points of equal depth (like a topographic map).  A leg, in this context, is a segment of the overall distance covered in the survey.

The information collected during this year’s survey helps determine the number of pollock that can be caught in next year’s fishing season.

Here is the ship tracker link, you can check out the Dyson’s course and other NOAA ships as well.

Personal Log 

I want to revisit the sonar of Mystery Mix One.  In my last blog I talked about what was happening near the surface of the ocean.  This time I want to focus beneath the sea floor.

Graphic provided by NOAA
Graphic provided by NOAA

Look beneath the red, yellow, and green bands, depicting the sea floor, at the blue color, notice how the density of color changes over time.  The density of the color tells scientists about the composition of the sea bed.  The denser the color, the denser or harder the seafloor is likely to be; probably, the places with the dark, dense color are rocky areas, which attract the fish schools seen in the water above.

Looking at this graph reminds me of an experiment that my husband worked on, when he worked for Charles Stark Draper Labs, in Boston, MA.  He worked on a Gravity Gradiometer that was sent to the moon on Apollo 17.  The gradiometer measured the changes in gravity.  The changes in gravitational strength give scientists information about what lays beneath the moon surface, like the sonar provides information about the sea bed.  The Gravity Gradiometer was a very specialized version of equipment that is commonly used in prospecting for oil on Earth.  I am sharing this story because, in class, one of our foci is to take what we know and apply the knowledge to a new scenario.  Next question:  Where will what we know now, take us in the future?

Did You Know?

Some fish can see color.


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