NOAA Teacher at Sea
Aboard NOAA Ship Fairweather
July 9 – 20, 2018
Mission: Arctic Access Hydrographic Survey
Geographic Area of Cruise: Point Hope, Alaska and Vicinity
Date: July 10, 2018 at 5:30pm
Weather Data from the Bridge
Latitude: 64° 29.691′ N
Longitude: 165° 26.276′ W
Wind: 5 knots SW, gusts up to 12 knots
Barometer: 99.9 kPa
Visibility: 10+ nautical miles
Temperature: 16.0° C
Sea Surface Temperature: 11.9° C
Weather: Cloudy, no precipitation
Science and Technology Log
I arrived in Nome on Saturday, July 7th around 7:30pm. The weather was a beautiful 65° F with just a few clouds in the sky! By the time I settled in my stateroom (bedroom) and unpacked my belongings, it was raining! According to the Western Regional Climate Center (WRCC), Nome receives and average of 16″ of rainfall each year and 60″ of snow. Despite this fairly low rainfall total, precipitation is a frequent
occurrence in Nome. Usually, the precipitation falls as more of a light drizzle in the summer, so the accumulation over the course of a year is very small.
I am here in Nome to join NOAA Ship Fairweather on a Hydrographic Survey of the vicinity of Point Hope, Alaska. Nome is the northernmost city in Alaska with a deep enough draft dock and facilities (such as sewage disposal and fresh water) for a ship. Therefore, we will start and end our trip in Nome. The ship has been experiencing some technical difficulties, so we were not able to go underway on our scheduled day of July 9. Over the weekend, engineers discovered a leak in the exhaust from one of the ship’s engines. Left untreated, black smoke could escape into the ship and personnel could be exposed to the unhealthy fumes. As of today, the exhaust pipe has been fixed, but there are a few parts that need to be shipped to Nome to finish the job. Hopefully NOAA Ship Fairweather will be underway later this week.
Once we are underway, the trip to Point Hope will take approximately 22 hours. That means we must reserve a full day on each end of the leg (another name for the trip) for travel. In order to maximize our limited time near Point Hope, NOAA Ship Fairweather will deploy up to four 28′ boats to work at the same time. There are also enough personnel onboard to allow data to be collected on the small boats for up to 24 hours per day. Two of the four 28′ boats are shown below.
So what are these boats all doing anyways? As previously mentioned, NOAA Ship Fairweather and its small boats are designed for hydrographic research. “Hydro” is a prefix meaning “water”, and “graph” is a root word meaning “to write”. The boats will map the sea floor (i.e. – “write” about what is under the water) and any of its contents with sonar devices. Sonar is an acronym that stands for SOund Navigation And Ranging. The main sonar device used on this ship is a multibeam echosounder (MBES for short), which can be found on the underside of the ship as seen below. Sound waves are emitted from the front of the device, known as the transmitter. The sound waves travel through the water column, bounce off the sea floor, and then get picked up by a receiver adjacent to the transmitter.
There is a lot of math involved both before and after sound wave data is collected! The photo below is a CTD instrument, which stands for conductivity, temperature, and depth. Conductivity is a measure of how well an object conducts electricity. This instrument is lowered through the water column, collecting data on all three parameters listed above. The speed of sound varies based on conductivity and temperature, so the sonar data can be adjusted based on the results. For each individual data point collected along the sea floor, the actual speed of sound is multiplied by half of the time it took the sound wave to travel from transmitter to receiver. Using the equation distance = rate x time, one can find the distance (i.e. – depth) of each point along the sea floor. Put a bunch of those results together, and you begin to see a map!
Sea floor maps use color to show different depths. The most shallow areas are colored with red, while the deepest areas are colored with blue. The remaining colors of the rainbow form a spectrum that allows us to see slopes. Today, we took a small boat out and surveyed the harbor where NOAA Ship Fairweather is docked. The harbor was very shallow, so every large rock in the harbor showed up as red on the map. The deeper areas showed up as blue. Hence my blog title! In my next blog, I will include pictures of maps that have recently been completed! Stay tuned!
Living on a ship that is docked in a tiny town with little to no cell phone service is fairly challenging. However, everyone on the ship finds creative solutions to keep themselves and others entertained. It is not uncommon for groups to form in the conference room to watch a movie on the big projector screen or to host a game night. There is also a fitness room onboard with plenty of exercise options! The Bering Sea and a long beach are a short, five minute walk from the ship. We had a campfire with marshmallows the first night that everyone returned to the ship from their time off. One person in our group found a whale bone on the beach! See the picture below. I spent some time walking the water line looking for sea glass. I actually found a few pieces, in
addition to a couple of rocks I thought were quite pretty! Sea glass is made from containers, bottles, and other glass objects that end up in the ocean. Over time, these objects break into smaller pieces, and the sandy and/or rocky sea floor erodes them. By the time they reach the beach, the pieces of glass have smooth edges and a translucent color. They are fun to collect as they come in many different colors, shapes, and sizes!
Did You Know?
Ocean water has a high conductivity, or ability to conduct electricity, because of all of the dissolved salts in sea water. The ions that form from dissolved salts cause ocean water to be about 1,000,000 times more conductive than fresh water!
Question of the Day
If a CTD determined that the speed of sound in an area was 1,504 m/s and the time it took for the sound wave to travel from the ship’s transmitter to receiver was 0.08 seconds, how deep was the water in that specific area? Make sure to use proper units, and remember that the total time is two ways and not just one way!
(Answer in the next blog post)