Kathy Virdin, July 20, 2004

NOAA Teacher at Sea
Kathy Virdin
Onboard NOAA Ship Rainier

July 20 – 28, 2004

Mission: Hydrographic Survey
Geographical Area:
Eastern Aleutian Islands, Alaska
July 20, 2004

Time: 2:20 p.m.
Latitude: 55 degrees 39.4 N
Longitude: 158 degrees 00.3 W
Visibility: 10 nautical miles (nm)
Wind direction: Northwest
Wind speed: 7 kts
Sea wave height: 0-1 ft.
Swell wave height:2-3 ft.
Sea water temperature:13.3 degrees Celsius
Sea level pressure:1010.1mb.
Cloud cover:3/8 partly cloudy

Science and Technology Log

Today we reached the point where we would begin our surveys. I watched the survey technicians lower a Seabird (sound velocity profile unit) into the water, then raise it back up and hook it into a computer, where they could download the information. This will give them the salinity (salt content), temperature and pressure of the water. They lowered the Seabird 117 meters down into the water, before retrieval. At the same time, from the hull of the ship, a transducer sound wave emitter is sending sound waves to the bottom and measuring the time it takes for their return. From this information, they will calculate the distance to the floor of the ocean. They use this data from the Seabird to help them make corrections in the sound wave speeds from the transducer. The salinity, temperature and pressure will cause variations in the speed of sound, so they need to correct for this effect to gain an accurate depth measurement.

This information is being processed and viewed by cartographers (map designers) who will take what data the RAINIER gives them to update old maps or develop new maps and charts. These maps are used by fishermen, geologists or anyone who navigates through these Alaskan waters. We are headed for the Shumagin Islands where we will send out launches (smaller boats) to measure depths in places where the Rainier might not otherwise go. I found it interesting to note that environmentalists would also use this information, since they know where certain species of fish are likely to live, and they can decide how best to protect them if they are endangered. We will go back and forth three times in one plotted line to make sure our data is accurate and complete. When we send out a launch in more shallow water, they will use a different sonar device, called a Reson. It emits higher sound waves which will give a more accurate reading. For middle to deep depth measurement, they will use the Elac sonar and a vertical beam echo sounder which goes straight down that can be used for shoreline measurements. Because Alaska has such rough terrain, it’s important to get accurate measurements for those who use her waters.

Personal Log

I am amazed by how specific the data is that the survey technicians collect and how well everyone knows their job. This is truly a finely tuned, professional organization. Everyone has been so kind to answer my many questions even though I’m sure I’ve gotten in their way. I’ve spent a lot of time in the Plot room, where the data is logged into the computers and then interpreted by the technicians. Outside, it’s a beautiful, sunny day, which is the first pretty weather we’ve had. We saw a pod of whales, recognizable by the blow of water coming from their nostrils. I could see them really well through the high-powered binoculars that belong to the ship. I am working on a list of questions that I will use to interview different members of the crew, as well as the scientists so I can take this information back to my students, as they learn what the roles are on a NOAA vessel. Someday, I want my students to be the next generation of scientists that use the knowledge we are gaining today to frame the discoveries they will make in the future.

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