NOAA Teacher at Sea
Aboard NOAA Ship Rainier
August 16 – September 5, 2014
Mission: Hydrographic Survey
Geographical Area of Survey: Woody Island Channel, Kodiak, Alaska
Date: August 22, 2014
Temperature & Weather: 11.5° C (53° F), Cloudy, Rainy
Science & Technology Log
Today was ‘Day 4’ of surveying in the Woody Island Channel next to Kodiak, Alaska. The Woody Island Channel is a very busy waterway leading ships, boats, and vessels of all sizes into Kodiak. The problem at the moment is that much of the Woody Island Channel has shoals (shallow areas) and rocks. This can be very dangerous, especially since the channel has not been surveyed or mapped since the 1940’s! At that, in the 40s, surveyors were using Lead Lines to map the ocean floor. Lead Lines were long ropes, marked with measurements, and with a weight at the end, that were thrown out to measure the depth of the water. Lead Lines were considered very accurate for their time. The problem with Lead Lines is that there was no way for surveyors to map the entire ocean floor–the lead line only gave a measurement of depth in one location (point) at a time.
Today, NOAA Hydrographers use Multibeam Echosounders. A Multibeam Echosounder uses sonar to send out hundreds of sound pulses and measures how long it takes for those pulses to come back. The multibeam echosounder is attached to the hull, or bottom, of the survey launches. To find out how deep the ocean floor is in an area, depths are generated by measuring how much time it takes for each of hundreds of sound pulses to be sent out from the echosounder, through the water to the ocean floor and back again. The sound pulses are sent out from the echosounder in an array almost like that of a flashlight.
The deeper the water, the wider the swath (band of sound pulses). The more shoal (shallow) the water, the smaller the swath. Basically, a wider area can be surveyed when the water is deeper. This means that surveying near shore, near rocky areas, and near harbors can be very time consuming. These surveys do need to be completed, however, if they are in navigationally significant areas, like the Woody Island Channel that Rainier is surveying right now.
Technological advances over the years have made it more efficient and more accurate to survey the oceans.
Using multibeam sonar, the Rainier has surveyed thousands of linear nautical miles of ocean in the past couple of years. In 2012 the Rainier was away from its home port in Newport, Oregon for 179 days–surveying 605 square nautical miles and 9,040 liner nautical miles. In 2013 Rainier was away from its home port for 169 days – surveying 640 square nautical miles and 7,400 linear nautical miles. It is NOAA’s goal to get 10,000 linear nautical miles surveyed each field season between all four of its Hydro ships: Rainier, Fairweather, Thomas Jefferson, and Ferdinand R. Hassler. Several years, the Rainier has come close to this on its own!
I have spent the last four days out on the survey launches, gathering data, with a bunch of amazing people. I have had the opportunity to drive a launch several times, with skilled Coxwain and Able Seaman Jeff Mays supervising me and helping me adjust to the differences in driving/steering a heavy boat versus driving my car at home. Jeff always took back over when we got to a rocky area or area that was shoaling up quickly. I am grateful to him, however, for the opportunity. As with any skill that needs to be practiced, I got a little better each time I drove. (Trying to steer in a straight line/path on the water when dealing with wind, water currents, waves, wakes from other boats, and the boats themselves is tough! At least for me. Coxwains Dennis Brooks and Jeff Mays make it look easy, and always kept me feeling safe aboard the launch boats!)
For My Students
Below is an update on my Alaskan Wildlife sightings. Remember, these are all animals I have been within 20 feet of (except for the bear). Along with the wildlife in the graph below, I have also seen hundreds of birds from a distance and several romp of otter (large groups).
Can you help me identify the pictures below? It can be quite difficult to identify creatures and “stuff” in the dark ocean waters.