NOAA Teacher at Sea Rebecca Kimport
NOAA Ship Oscar Dyson
June 30, 2010 – July 19, 2010
Mission: Summer Pollock survey
Geograpical Area:Bering Sea, Alaska
Date: June 30, 2010
What’s in your water?
After our first CTD, we completed our first Methot trawl. A Methot trawl is named after the scientist who designed the net used. Here is a picture of the methot getting hauled back on deck (please note, it does actually get dark here. I woke up in the dead of night and had to wait two hours for sunrise. Sunrise is at the “normal” time of 6:30 am and I think that’s because we are on the western edge of the time zone)
A Methot net grabs the creatures and collects them into a codend (to make it easier for us to process) at 30-40 m below the surface – our Methot collected jellies and euphausiids (also known as krill). My first duty was to sort through the “catch” to pick out jellies. Next, we measured the weight of the krill before counting a small sample. We also preserved a couple samples for use in larger studies.
Following our Methot, I assisted with the completion of an XBT (eXpenable Bathymetric Thermograph). At left, you will see that I actually “launched” the XBT overboard. The XBT is used to collect quick temperature data from the surface to the sea floor. The data are graphed at depth vs. temperature to highlight the thermocline, that is where colder water meets water warmed by the sun. Here in the Bering Sea, the thermocline is not always noticeable as the water column is subject to mixing from heavy winds and shallow depths.
Lucky for us, it was a calm day on the water and we were able to see a distinct thermocline:
Beyond the Oscar Dyson, these data are collected on every NOAA cruise that I read about and that data can be used to measure how a body of water is doing in general as well as how the water column of a specific location has changed over time. For example, longitudinal data are needed to note climate change within the Bering Sea. Pretty cool huh?
Vocabulary Note: I tried to define all the new terms I used in my entry. Did you notice a term I didn’t define? Ask me about it in the comments and I will make sure to provide you with a definition.
Thought Question: In the XBT data graph, why is the X axis labeled on the top rather than the bottom? (think about your coordinate plane)