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Between
19 and 25th June 2007, the Irish research vessel
RV Celtic Explorer left Galway on a short
one week cruise to the Porcupine Abyssal
Plain (PAP) (Figure 1). The PAP site is a
long term study site where a variety of ocean
observations have been made over the past 20
years with increasing levels of intensity and
sophistication. This has produced a unique set
of time-series data from the NE Atlantic which
scientists use to monitor closely the changing
properties of the oceans and to understand
short-term variation and ecosystem dynamics,
capture episodic events such as phytoplankton
blooms and understand long-term variation and
climatic trends.
The PAP site
is part of a network of European deep ocean
observatories supported by the EUR-OCEANS FP6
Network of Excellence
http://www.eur-oceans.eu/integration/wp2.1/
A cruise
web log highlighting the aims and objectives of the
cruise for public outreach purposes can be found at:
http://www.eur-oceans.info/EN/diary/celtic_explorer/
Figure 1: PAP Location
The
purpose of the latest maintenance cruise to the
PAP site
The main
and almost exclusive objective of the cruise was
to deploy 2 moorings at the PAP site; the PAP#1
sensor mooring to replace the mooring line
destroyed by long line fishing in 2006 and to
recover and redeploy the PAP#3 sediment trap
mooring. Both moorings were successfully
deployed along with a Bathysnap time-lapse
camera system on a benthic lander.
Prior to
deployment of the PAP#1 mooring, the sensors
were calibrated by carrying out a CTD dip with
the sensors attached. In addition, water samples
were taken from CTD rosette casts for inorganic
nutrients, salts, chlorophyll-a and CO2.
These will be used to further calibrate the
in situ sensors on the PAP#1 mooring.
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PAP observatory
configuration
The main mooring (PAP#1) (Figure 2) has
a large surface buoy (Toroid type)
(Figure 3).
30 m below the surface buoy is a sensor
frame containing a package of 5
biogeochemical sensors; a SAMI (CO2),
SBE 37 Microcat (Temperature and
Conductivity), Wetlabs Fluorometer
FLNTUSB (Fluorescence and
Chlorophyll-a), ISUS and EnviroTech
NAS-3X (both nitrate) (Figure 4). In
addition, 11 Microcats (Figure 5) are
placed at various depths down to 1000
m. Figure 5 shows the mooring design
which is an “S” tether configuration to
allow the mooring to better withstand
the extremes of the North East Atlantic
environment.
The sediment trap mooring (PAP#3)
(Figure 6) has 3 sediment traps; at
3000, 3050 m and 4700 m (100 m above the
sea floor).
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Figure 3: Surface
buoy of PAP#1 sensor mooring |
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Figure 4: Deployment
of the biogeochemical sensor frame on
the PAP#1 sensor mooring which is
maintained at a nominal depth of 30 m.
NB. In this photo the sensor frame is
upside down for deployment purposes
only.
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Figure 5: SBE 37 Microcats ready
for deployment on PAP#1 sensor mooring |
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