NOAA Teacher at Sea
Aboard NOAA Ship Rainier
June 3 – 14, 2019
Mission: Kodiak Island Hydrographic Survey
Geographic Area of Cruise: Kodiak Island, Alaska
Date: June 6, 2019
Time: 2000 hours
Location: Underway to Isthmus Bay, Kodiak Island
Weather from the Bridge:
Latitude: 57°39.2266’ N
Longitude: 152°07.5163’ W
Wind Speed: 11.6 knots
Wind Direction: NW (300 degrees)
Air Temperature: 11.37° Celsius
Water Temperature: 8.3° Celsius
Science and Technology Log
Today I went out on a launch for the first time. The plan was to survey an area offshore and then move nearshore at low tide, with the water at its lowest level on the beach of Kodiak Island. Survey Techs, Carl Stedman and Christina Brooks, showed me the software applications used to communicate with the coxswain and collect data. To choose the best frequency for our multibeam pulse, we needed to know the approximate depth of the area being surveyed. If the water is deeper, you must use lower frequency sound waves, since higher frequency waves tend to attenuate, or weaken, as they travel. We chose a frequency of 300 kilohertz for a 60 meter depth. Periodically, the survey techs must cast a probe into the water. The Sea-bird SeaCAT CTD (Conductivity, Temperature, Depth) measures the characteristics of the water, creating a sound velocity profile. This profile can tell us how quickly we should expect sound waves to travel through the water based upon the water’s temperature, salinity, and pressure.
Using the sound velocity profile allows the computer’s Seafloor Information System (SIS) to correct for changes in water density as data is being collected. Once the profile was transmitted to SIS, we were ready to begin logging data.
Imagine that you are mowing your lawn. To maximize efficiency you most likely will choose to mow back and forth in relatively straight paths, overlapping each new row with the previous row. This is similar to how the offshore survey is carried out. As the boat travels at a speed of about 7 knots, the Kongsberg EM2040 multibeam sonar transducer sends out and receives pulses, which together create a swath. The more shallow the water, the wider the base of the swath.
After lunch we changed to a nearshore area closer to Kodiak Island between Sequel Point and Cape Greville. It was important to wait for low tide before approaching the shore to avoid being stuck inshore as the tide is going out. Even so, our coxswain was very careful to follow the edges of the last swaths logged. Since the swath area extends beyond the port and starboard sides of the boat, we could collect data from previously uncharted areas without driving directly above them. In this way we found many rocks, invisible to the naked eye, that could have seriously damaged an unlucky fisherman!
Career Focus – Able Seaman
Our coxswain driving the boat today was Allan Quintana.
As an Able Seaman, Allan is part of the Deck Department, which functions primarily to keep track of the ship, manage the lines and anchoring, and deploy and drive the launches. Allan started out working for the Navy and later transitioned to NOAA. A Miami native, he told me how he loves working at sea, in spite of the long stretches of time away from his friends and family back home.
If you have never been on a boat before, it is a unique experience. Attempts have been made by poets, explorers, scientists, naturalists, and others throughout history to capture the feeling of being at sea. Although I’ve read many of their descriptions and tried to imagine myself in their shoes, nothing compares to experiencing it first-hand.
Standing on the bow of the anchored ship, looking out at the water, my body leaning to and fro, rising and falling, I am a sentient fishing bobber, continuously rocking but not really going anywhere. My head feels somehow both heavy and light, and if I stand there long enough, I just might fall asleep under the spell of kinetic hypnosis. The motion of the launch is different. A smaller boat with far less mass is bullied by the swells. For a new crew member like me, it’s easy to be caught off guard and knocked over, unless you have a good grip. I stand alert, feet apart, one hand clasping a rail, as the more experienced crew move about, casually completing various tasks. I wonder how long it would take to become accustomed to the boat’s rising and falling. Would my body gradually learn to anticipate the back and forth rocking? Would I eventually not feel any movement at all?
Word of the Day
draft – the vertical distance between the waterline and the hull of a boat, a.k.a. the draught
The draft of NOAA Ship Rainier is 17 feet.