Debbie Stringham, July 9, 2005

NOAA Teacher at Sea
Debbie Stringham
Onboard NOAA Ship Fairweather
July 5 – 15, 2005

Mission: Hydrographic Survey
Geographical Area: North Pacific, Alaska
Date: July 9, 2005

Debbie Stringham pulling lines for bottom sampling
Debbie Stringham pulling lines for bottom sampling

Weather Data 

Location: Eagle Harbour, Shumagin Islands, AK
Latitude: 55 06.8’ N
Longitude: 160 06.9’ W
Visibility: 10 nm.
True Wind Speed: 16 kts.
True Wind Direction: 340
Sea Wave Height: 1 ft.
Swell Wave Height: none
Swell Wave Direction: none
Sea Water Temperature: 12.0 C
Sea Level Pressure: 1011.5 mb
Sky Description: Partly Cloudy
Dry Bulb Temperature: 15.5 C
Wet Bulb Temperature: 12.5 C

Science and Technology Log 

Today, I was assigned to go on a bottom sampling launch. The purpose of these launches is to collect floor samples to determine the nature of the sea floor. The instrument used is called a bottom sampler and looks like a large heavy metal pipe about a foot in length and four inches in diameter. There is a large metal spring attached to the top of it along with a scooping mechanism that clamps shut when it hits the sea floor. On the other end, is an O-ring where a line can be strung through and attached to a pulley.

Bottom Sampling Device
Bottom Sampling Device

First, the designated sampling locations are decided by where they lie in relation to the coast. There are collection standards that regulate where sampling can occur and how often. If the region is deemed anchorage, then samples may be taken 1200 meters apart. If the region is not considered anchorage, then the samples need to be spaced 2000 meters apart. Using a Digital Terrane Model (DTM), the survey technician chooses an arbitrary point and fans out from there, choosing collection locations in accordance with the regulations above.

Once the bottom sampling is underway, the boat will use a Global Positioning System (GPS), to locate where a sample will be taken from. The survey technician will open the scooping mechanism and lower it over the side of the boat. When the bottom sampler hits the bottom, it will be brought back to the surface where the sample, if any, will be analyzed and recorded. If no sample is retrieved after three attempts, then the sea floor is recorded as hard. Survey technicians use abbreviated terms to describe the bottom samples. For example: crs S = coarse sand, brk Sh = broken shells, gy M = gray mud, med P = medium pebbles.

Question of the Day 

Why is looking at the nature of the seafloor material important?

Answer from Previous Day 

In the early days of sailing, the steering board (eventually to become starboard) was on the right hand side of the ship. And the side of the ship that was usually tied up to port was the left hand side. Sailors began calling the right side of the ship (when facing front) the starboard side and the left hand side of the ship port.

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