NOAA Teacher at Sea
Aboard NOAA Ship Rainier
September 17 — October 7, 2011
Mission: Hydrographic Survey
Geographical Area: Alaskan Coastline, the Inside Passage
Date: Thursday, September 29, 2011
Weather Data from the Bridge
Visibility: 2 Nautical Miles
Wind: 15 knots
Dry Bulb: 8.2 degrees Celsius
Barometer: 1001.1 millibars
Latitude: 55.42 degrees North
Longitude: -133.45 degrees West
Science and Technology
When we are out on a launch acquiring data there are so many beautiful shorelines to see. From far away they look inviting, but in reality there are usually numerous boat hazards lurking below or on the shoreline. I have written a lot about the hydrographic survey aspect of this mission and how it is important to ships so that they can navigate safely.
However, when we are out on a survey launch the first priority is safety of the crew, the boat, and the technology. This means that we normally do not go anywhere that is shallower than about eight meters. Consequently, this leaves areas near the shore that is not surveyed and leaves holes in the chart data. This is where shoreline verification comes in using single beam sonar. However, since the launch with the single beam is not operational at this time we have been using the multibeam instead. The Marine Chart Division (MCD) gives the Rainier specific items that need to be identified because they are considered Dangers to Navigation, or they need to be noted that they do not exist. The MCD compiles a priority list of features that come from numerous sources such as cruise ships, aircraft pilots, and other boats that have noted that there may be a danger to navigation in a certain area. Many of these charts have not been updated since they were created in the early 1900’s or never charted at all!
Before we leave the Sheet Manager and the Field Operations Officer (FOO) come up with a plan for what shoreline they want to verify for the day. A plan must be made because there is a small window to acquire the information needed to satisfy the requests of the Marine Chart Division. The shoreline verifications must be done at Mean Low or Low Water. This means that it has to be done when the average low tide of each day comes around, which has been in the early morning and afternoon for us.
Using the launches we head up to what is called the four meter curve. This curve is the limit to where we can go during meal low or low water. If we get any shallower or move closer to the shore then we will put everyone and everything in danger on the boat. We bring with us a camera to document the features, a clinometer, which allows us to document headings and angles, a laser range finder, charts that they can draw and note features on, and their computer software. Once we get underway and arrive to our first rock that we have to document, the officers make sure they maintain good communication with the coxswain, or boat driver. We make sure we circle everything in a counterclockwise motion so that he can see everything off to his starboard, or right side as we move. We can see the rock become exposed as the waves move over it, but the tricky part is getting as close to it as possible without hitting it. This is so we can get a precise location as possible for the chart. Our coxswain was very experienced so we were able to get right next to it for photos, the heading, and to drop a target, or the location, in the software.
The rest of our shoreline verification was a lot less intense as we confirmed that there was a lot of kelp around the rocks, the shoreline, and specific rocks were in the correct place. LT Gonsalves, the Hydrographer-in-Charge (HIC), showed me how he draws some of the features on his chart and makes notes about whether the features are there or not. I took photos and noted the photo numbers for the chart, as well as the range and height of various features. Shoreline verification is very important for nautical charts so that ships and their passengers know exactly where dangers to navigation lie. It takes 120 days from the final sounding for all the data to get submitted to the Hydrographic Survey Division. From there the information gets looked over by numerous agencies until about 2 years later the updated chart is available. This is quite a long time to wait for changes in dangers to navigation. To be safe, the chart stays the same even if there is not a dangerous rock lurking around at mean low or low water. It is best to just avoid the area and err on the side of caution. There is still a lot of work to be done in Alaska that will take many, many years to complete. However, it is thanks to hydrographic ships like the Rainier and its crew that get the job done.
Tonight was very special because we could actually see an aurora, or the northern lights, in the night sky. An aurora is a natural light display in the arctic and antarctic, which is caused by the collision of charged particles in the upper atmosphere. Auroras start way back about 93 million miles (or 1 astronomical unit– AU) at the sun. When the sun is active, usually due to coronal mass ejections, it releases energetic particles into space with the very hot solar wind. These particles travel very quickly over those 93 million miles until they reach the Earth’s magnetic field. Most of these energetic particles are deflected around the Earth, but some get trapped in the magnetic field and are moved along towards the polar regions until they strike the atmosphere. We knew there were possibilities to see an aurora while we were anchored, but usually it has been cloudy at night so we couldn’t see the stars. However, on the 27th Officer Manda came through saying he had seen the lights. Low and behold there was a green glow in the sky behind some clouds and a couple of times some of the energized particles made bands across the sky. If there hadn’t been so many clouds I think it would have been even more spectacular, but I was so glad I did get to see them. Very quickly, more clouds moved in and it was just a green glow on the horizon. I also was able to see the milky way in all its glory and the brightest shooting star I have ever seen. These amazing photos of the aurora were taken by Ensign Manda and I am very grateful he was willing to share.
Click HERE for a link to a neat animation of how an aurora is formed.
Student Questions Answered
Seals – species unknown
Question of the Day