CE17-01 Celtic Sea Front

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Celtic Sea Front - WC Section
RV Celtic Explorer Cruise CE17-01
Chief Scientist: Kevin Sheehan, MI
July 22nd to August 6th 2017

John E. Hughes Clarke
Anand Hiroji
Jose Cordero Ros
Center for Coastal and Ocean Mapping
University of New Hampshire

Overview:

As part of this cruise, the viability of tracking the thermocline undulations, using EK60 or EM2040/302 water column was being investigated. In reality, however, the centre of the Celtic Sea is an area of regionally uniform thermocline development and thus it was suspected to be reasonably clearly defined. The only suspected variability is the seasonal growth and decay, and the tidally driven internal wave modulations.

The more challenging region for sound speed occurs where the transition from a stratified to a mixed watermass occurs . This happens with increasing tidal velocities and decreasing depth. The classic transition (over which the phenomena was first described and modeled (Simpson and Bowers, DSR, 1981)) is the Celtic Sea front.


GEBCO bathymetry with CE17-01 navigation superimposed rotated white box is the registration section for the transit MB-WC data.	Sea Surface Temperature Map (archived from summer 1999)

While this region was not a specifically targeted investigation of this cruise, the outbound transit actually did cross this front. At the time, both EM systems and the 4 channels of the EK60 were being already being logged (although with variable synchronization). Alas no MVPs were being collected at his point. The results are shown below.

As can be seen, the transition from homogenized water to stratified watermasses can clearly be seen. Unfortunately the planned survey areas off Wexford for the RV Celtic Voyager this summer lie directly over the transitional watermasses where the greatest spatial variability in sound speed is to be expected.

All data is presented from the NW (left) to the SE (right)
transiting from Dublin to the CE17-01 survey area.

EK60 - false colour - red-18 - green -38 - blue 120

18 kHz

38 kHz

120 kHz

EK-60 200 kHz

EM2040 watercolumn (200 kHz mode).

EM302 watercolumn (30 kHz)

page composed offshore -- JEHC