TRASNA Blog – Day 2

TRASNA Blog – Day 2

Written by:
Peter Macintosh
Earth scientist
Undergraduate at Memorial University

May 13, 2016
2227 UTC
Wind SW @19 Kts
Air Temperature 8°C
Sea State 2m

We started today by conducting a XBT or (Expendable Bathythermograph test) this is a single use test that can be preformed while the boat is still moving. The test consists of shooting a torpedo into the water that will read temperature and depth as it sinks to the sea floor. We use this test rather than a CTD (conductivity temperature depth test) because it is quicker and saves time. Knowing the ocean temperature is very important because it is directly proportional to the density of the ocean. Different densities of the ocean can cause errors in our multibeam bathymetric readings.  The changing densities in the ocean cause the outer beams of the multi beam to travel different distances than the inner beams. This leads to readings showing higher topography areas of sea floor along the outer edges of the multibeam and shallower lower topographies in the center if the multibeam map. These errors can be easily fixed by inputting the recorded temperature data into a logarithm which the multi beam can read and then correct for these discrepancies. During our test we discovered the average temperature of the ocean to be 3.8°C.

Scientist conducting an XBT test at the rear of the boat


Accompanying reading associated with XBT test

As the day continued we entered a low pressure system that forecasted some moderate winds. However, the forecast was slightly incorrect.  The low pressure system created hurricane force winds and 8-10 meter swells. The winds and waves caused interference with our mapping equipment resulting in suspension of data collection until conditions improved. The wind was so strong that the captain stated that the wind was pushing us backwards from our desired course at a rate of 3 knots. The next 12 hours consisted of attempting to walk around the deck without falling. While making no progress towards our final destination. The forecast shows that the winds should begin to subside around 6am tomorrow.