NOAA Teacher at Sea
Aboard NOAA ship Gordon Gunter
March 17 – April 2, 2015
Mission: Winter Plankton Survey
Geographic area of cruise: Gulf of Mexico
Date: April 1, 2015
Weather Data from the Bridge
Date: 3/31/2015; Time 2000; clouds 25%, cumulus and cirrus; Wind 205° (SSW), 15 knots; waves 1-2 ft; swells 1-2 ft; sea temp 23°C; air temp 23°C
Science and Technology Log
You’re not going to believe what we caught in our neuston net yesterday – a giant squid! We were able to get it on board and it was 23 feet long! Here’s a picture from after we released it:
April Fools! (sorry, couldn’t resist) The biggest squid we’ve caught are about a half inch long. Image from http://www.factzoo.com/.
Let’s talk about something just as exciting – navigation. I visit the bridge often and find it all very interesting, so I got a 30 minute crash course on navigation. We joked that with 30 minutes of training, yes, we would be crashing!
From the bridge, you can see a long way in any direction. The visible range of a human eye in good conditions is 10 miles. Because the earth is curved, we can’t see that far. There is a cool little formula to figure out how far you can see. You take the square root of your “height of eye” above sea level, and multiply that by 1.17. That gives you the nautical miles that you can see.
So the bridge is 36 feet up. “Really?” I asked Dave. He said, “Here, I’ll show you,” and took out a tape measure.
OK, 36 feet it is, to the rail. Add a couple of feet to get to eye level. 38 feet. Square root of 38 x 1.17, and there we have it: 7.2 nautical miles. That is 8.3 statute miles (the “mile” we are used to using). That’s assuming you are looking at something right at sea level – say, a giant squid at the surface. If something is sticking up from sea level, like a boat, that changes everything. And believe me, there are tables and charts to figure all that out. Last night the bridge watch saw a ship’s light that was 26 miles away! The light on our ship is at 76 feet, so they might have been able to see us as well.
If you can see 7.2 nautical miles in any direction, what is the total area of the field of view? It’s a really amazing number!
Back to navigation
Below are some photos of the navigation charts. They can be zoomed in or out, and the officers use the computer to chart the course. You can see us on the chart – the little green boat.
In the chart above, you’ll see that we seem to be off course. Why? Most likely because of that other ship that is headed our direction. We talk to them over the radio to get their intentions, and reroute our course accordingly.
When we get close to a station, as in the first picture above, the bridge watch team sets up a circle with a one mile radius around the location of the station. See the circle, upper center? We need to stay within that circle the whole time we are collecting our samples. With the bongos and the neuston net, the ship is moving slowly, and with the CTD the ship tries maintain a stationary position. However, wind and current can affect the position. These factors are taken into account before we start the station. The officer on the bridge plans out where to start so that we stay within the circle, and our gear that is deployed doesn’t get pushed into or under the boat. It’s really a matter of lining up vectors to figure it all out – math and physics at work. But what is physics but an extension of common sense? Here’s a close-up:
How do those other ships appear on the chart? This is through input from the AIS (Automated Information System), through which we can know all about other ships. It broadcasts their information over VHF radio waves. We know their name, purpose, size, direction, speed, etc. Using this and the radar system, we can plan which heading to take to give the one-mile distance that is required according to ship rules.
As a backup to the computer navigation system, every half hour, our coordinates are written on the (real paper) navigation chart, by hand.
There are drawers full of charts for everywhere the Gunter travels!
Below is our radar screen. There are 3 other ships on the screen right now. The radar computer tells us the other vessels’ bearing and speed, and how close they will get to us if we both maintain our course and speed.
If the radar goes down, the officers know how to plot all this on paper.
Below is Dave showing me the rudder controls. The rudder is set to correct course automatically. It has a weather adjustment knob on it. If the weather is rough (wind, waves, current), the knob can allow for more rudder correction to stay on course. So when do they touch the wheel? To make big adjustments when at station, or doing course changes.
These are the propulsion control throttles – one for each propeller. They control the propeller speed (in other words, the ship’s speed).
And below is the Global Maritime Distress and Safety System (GMDSS). It prints out any nautical distress signal that is happening anywhere in the world!
And then, of course, there is a regular computer, which is usually showing the ships stats, and is connected to the network of computers throughout the ship.
In my post of March 17, I described the gyrocompass. That is what we use to determine direction, and here is a rather non-exciting picture of this very important tool.
As you can see, we have two gyrocompasses, but since knowing our heading is probably the most important thing on the ship, there are backup plans in place. With every watch (every 4 hours), the gyro compass is aligned the magnetic compass to determine our declination from true north. Also, once per trip, the “gyro error” is calculated, using this nifty device:
The reading off of the alidade, combined with the exact time, coordinates, and some fancy math, will determine the gyro error. (Click on a picture to see full captions and full size pictures.)
You can see that we have manual backups for everything having to do with navigation. We won’t get lost, and we’ll always know where we are!
Back to Plankton!
These past two days, we have been in transit, so no sampling has been done. But here are a couple more cool micrographs of plankton that Pam shared with me.
Interesting Fish Facts
Our main fish of interest in the winter plankton sampling are the groupers. There are two main species: gag groupers and red groupers. You can learn all about them on the NOAA FishWatch Website. Groupers grow slowly and live a long time. Interestingly, some change from female to male after about seven years – they are protogynous hermaphrodites.
In the spring plankton research cruise, which goes out for all of May, the main species of interest is the Atlantic bluefin tuna. This species can reach 13 feet long and 2000 lbs, and females produce 10 million eggs a year!
The fall plankton research focuses on red snapper. These grow up to about 50 pounds and live a long time. You can see from the map of their habitat that it is right along the continental shelf where the sampling stations are.
The NOAA FishWatch website is a fantastic resource, not only to learn about the biology, but about how they are managed and the history of each fishery. I encourage you to look around. You can see that all three of these fish groups have been overfished, and because of careful management, and research such as what we are doing, the stocks are recovering – still a long way from what they were 50 years ago, but improving.
I had a good question come in: how long before the fish larvae are adults? Well, fish are interesting creatures; they are dependent on the conditions of their environment to grow. Unlike us, fish will grow throughout their life! Have you ever kept goldfish in an aquarium or goldfish bowl? They only grow an inch or two long, right? If you put them in an outdoor pond, you’ll see that they will grow much larger, about six inches! It all depends on the environment (combined with genetics).
“Adult” generally means that they are old enough to reproduce. That will vary by species, but with groupers, it is around 4 years. They spawn in the winter, and will remain larvae for much longer than other fish, because of the cooler water.
I’ve used up my space in this post, and didn’t even get to tell you about our scientists! I will save that for next time. For now, I want to share just a few more pictures of the ship. (Again, click on one to get a slide show.)
Terms to Learn
What is the difference between a nautical mile and a statute mile? How about a knot?
Do you know what I mean when I say “invertebrate?” It is an animal without a backbone. Shrimp and crabs, are invertebrates; we are vertebrates!