Tammy Orilio, A Little Bit of Science…, June 18, 2011

NOAA Teacher at Sea: Tammy Orilio
NOAA Ship Oscar Dyson
Mission: Pollock Survey
Geographical Area of Cruise: Gulf of Alaska
Date: 18 June 2011

Weather Data from the Bridge:
Latitude: 52.34 N
Longitude: -167.51 W
Wind Speed: 7.25 knots
Surface Water Temp: 6.6 degrees C (~43.9 degrees F)
Water Depth: 63.53 m
Air Temp: 7.1 degrees C (~44.8 degrees F)
Relative Humidity: 101% (it’s very cloudy/foggy, but not raining)

Science & Technology Log:

The XBT Launcher mechanism.
The XBT Launcher mechanism.

Today I used the Expendable Bathythermograph (XBT) a few times. The WHAT??   The expendable part means we use it once and don’t recover it.  Let’s break down the second part into the two main roots:  bathy– which refers to depth, and thermo which refers to temperature.  This probe measures the temperature and depth of the water when it is dropped over the starboard (right) side of the ship.

“Dropping” isn’t exactly the correct phrase- we use a launcher that kind of resembles a gun.  The probe sits inside of the black tube, and after we uncap the end of the tube, we basically fling our arm out over the side of the ship to launch the probe into the water.  I can’t show you any pics of the probe, because if we take it out of the black tube, it’ll start recording data.  The probe is connected to a length of copper wire, which runs continuously as the probe falls through the water column, collecting data.  It’s important to launch the probe as far away from the ship as possible, because if the copper wire touches the metal on the ship, the data feed will be disrupted and we’d have to launch another probe.  Big waste of money and equipment! One of the survey technicians decides to cut the wire (or tells me to) when they’ve decided that a sufficient amount of data has been collected, and we can then look at a graph to see the relationship between temperature and depth.
The XBT is a quick and easy method of data collection, and can be run while the ship is in motion.  The ship does have another piece of equipment- the Conductivity, Temperature, and Depth meter (CTD)- to collect the same data, but the CTD is very big and bulky, and the ship must be stopped in order to deploy the CTD.  The CTD can also measure parameters such as dissolved oxygen concentration, current velocity, and other things (depending on the additional equipment on the meter).  The main advantage the XBT has is that it is quick and can be deployed as the ship is sailing.

from www.windows2universe.org
from http://www.windows2universe.org

Data Collected from an XBT probe today:
Latitude: 53.20 N
Longitude: -167.46 W
Water Temp at Surface: 6.7 degrees C
Water Temp at Bottom: 5.1 degrees C
Thermocline located from 0-25 meters depth

What is a thermocline, you ask?  Root word time!  We’ve already gone over thermo, and cline refers to a gradient, or where things change rapidly.  So, the thermocline is the area where you see the greatest change in temperature.  See the diagram as an example (it’s not our actual data).  Beneath the thermocline, the water temperature remains relatively constant.
Personal log:

Launching the XBT in full safety gear (minus the hardhat, it fell off)
Launching the XBT in full safety gear (minus the hardhat, it fell off)
Safety first, my friends.
Safety first, my friends.

Yesterday, as we were finally on our first transect of many, we needed to use the XBT to collect temperature and depth data.  A couple of the scientists told me that I could do it- yay, something for me to do!!  So I go to the lab room and see a ton of safety gear out- heavy coat, hardhat, gloves, soundproof earmuffs, goggles.  The survey tech tells me that I have to use all that protective gear because the XBT launcher is just like a gun- have I shot a gun before?  No!  So this is interesting.  I don the gear, and he explains what I need to do…which doesn’t seem that dangerous.  So now here I am, all geared up, and the rest of the scientists come trickling in to the lab to watch me.  That should’ve been a red light right there.  Why would they want to watch me do something so simple?  Turns out that it’s something that all the new people on the boat go through- we get all hyped up about shooting a loud gun, get loaded with gear, and then…not much.  So I basically got all dressed up in my protective gear for no other reason than the entertainment of the crew!!


Why is it important to know the temperature and/or depth of the water that we’re trawling in?

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