NOAA Teacher at Sea
Aboard NOAA Ship Oscar Dyson
June 8-26, 2013
Mission: Pollock Survey
Geographical area of cruise: Gulf of Alaska
Date: June 8, 2013
Weather Data from the Bridge: as of 1900
Wind Speed 9.57 kts
Air Temperature 6.84°C
Relative Humidity 81.00%
Barometric Pressure 1,030.5 mb
Latitude: 53.52N Longitude: 166.34W
Science and Technology Log
The Oscar Dyson is harbored in Captains Bay and there is much to do aboard before we set sail on our cruise. Some equipment needs to be off loaded and stored while other equipment needs to be loaded and secured. The Science Team checks their berth (room) assignments, drop off their gear, and begin the task of readying the equipment.
“What are the properties of sea water?” Are you thinking liquid? There are three properties that scientists routinely check, they are temperature, salinity and density. The Dyson’s crew deploys an instrument referred to as the CTD. The CTD contains sensors which continuously measure the Conductivity, Temperature and Depth of the water. The CTD is sent to the bottom to create a profile of the temperature and salinity (as measured by how well the water conducts electricity or its ‘conductivity’) and then is brought back to the surface. On the way back up water samples are collected at per determined depths, in the grey bottles. The collected water samples are measured to calibrate the sensors on the CTD. This information is then used to calibrate the sonar.
Sonar uses sound waves called pings that bounce off objects creating echoes. The echoes are recorded and used to create pictures of the sea floor and other object, such as schools of fish. To calibrate the sonar a round shiny ball that reflects the pings is submerged beneath the ship. The scientists know the expected strength of the echo from the sphere given the water temperature and salinity, allowing them to calibrate the sonar. Sometimes fish interfere with the calibration process. Fish are curious creatures and want to investigate the shiny sphere, getting in the way of the pings and slowing down calibration.
When the calibrations have been completed we set sail. As the Dyson sailed out of Captains Bay, we encountered dolphins jumping out of the water and whales surfacing. Perhaps they were feeding on the large school of fish seen in the sonar.
Before leaving Seattle, I was told my luggage might not be on the same flight as I was on into Dutch Harbor. The airport in ‘Dutch’ has a short runway and is serviced by turbo prop aircraft that seat 33 passengers. When I checked in, I was asked for my weight and any carry-on. The airline uses the total loaded weight of the aircraft to calculate how much runway is needed to take off and how much fuel is needed to reach the next refueling point. Upon boarding the plane, the passengers were told that 87 pounds of luggage would not make the flight and more than likely the bags would be on tomorrow morning’s freighter– weather and volcanic activity permitting! I kept my fingers crossed that my bag was in the cargo hold. A little over an hour into the flight, we landed in King Salmon for refueling. Shortly after landing, we were once again airborne for the 1 ½ hour flight to Dutch Harbor. In route along the volcanic chain of Aleutian Islands, you can see peaks visibly venting steam and Mt. Pavlof’s snowy surface is blackened with fresh ash. The Oscar Dyson will sail past several of these active volcanoes. Looks like I’ll be adding a volcanic eruption to my list of “want to see” while aboard the Dyson. I am also hoping to see the Aurora Borealis and pods of Humpback and Orca whales. Landing at Dutch Harbor I realized why weather is a crucial factor for safe touch downs. A section of Mt. Ballyhoo has been blasted away to make room for the runway. Peering out the window, one gets the feeling that the tip of the wing is barely whisking past the face of the cliff. On the other side of the runway is the water of Iliuliuk Bay. Good news, my luggage and I landed at the same time!
Dutch Harbor attracts many bird watchers, as bald eagles, puffins, rock ptarmigans and other birds are abundant here. Juvenile bald eagles are dappled brown and white and blend into the rocky shore and crags of the steep cliffs. This time of year, signs warning of nesting eagles are also abundant. As birds tend to use me for target practice I am very mindful of the warnings.
Before boarding the Oscar Dyson I visited the Museum of the Aleutians. The exhibits feature information about life and culture in the Aleutians and how WWII impacted the people. One of the displays featured several handmade parkas constructed from the gut (intestine) of seals and walruses. The material is both light weight and water proof.
Just south of the museum is Bunker Hill towers above Dutch Harbor, and one can still see the zigzag pattern of the WWII trenches etched into the landscape. There is a trail to the bunker atop the hill; I think I’ll go for a walk. Almost to the top of Bunker Hill about 700 feet above Dutch Harbor the panoramic vistas of Captains Bay, Dutch Harbor and the City Unalaska are spectacular.
Did You Know?
The Gulf of Alaska helps to generate much of the seasonal rainfall along the west coast of British Columbia, Washington, and Oregon. The strong surface currents, as high as 1.7kph (1.9mph) in the southern reaches combine with the cold arctic air to create these weather systems that affect our weather and climate.