Oceanographic Instrumentation

Posted Tue, 12/15/2009 - 17:31 by susan.kelly
Oceanographic Instrumentation
 
RAGES will employ a variety of oceanographic instruments that can be used in various combinations depending on the mission and objective of each deployment. The prime tool will be GIPSIE, Geochemical Instrumentation Package for Sub-Ice Exploration. Beyond GIPSIE we will have instrumentation to collect data from an oceanographic mooring at the borehole site while the SIR is operating over a larger area. The other forms of oceanographic instrumentation are long-term moorings that will be deployed during the last phase of operations when we are occupying a site. They will be left making their measurements for one year or more by relaying their data to surface recording units.
 
These instruments, owned by Northern Illinois University, are modular and components can be interchanged depending on borehole diameter and scientific data required. They can therefore take various forms, but are basically instrumented with CTD, DO meter, transmissometer, and Doppler current meter immediately below the ice
that will measure turbulent heat flux across the ice-water interface. This node is termed the basal energy balance station. Below this, on an inductive wireline, is a McLane “Ice Tethered Profiler” (CTD with an added Doppler current sensor) for documenting water column structure and currents in the sub-ice shelf cavity. The McLane profiler is a WHOI-design that has been used through sea ice deployments in the Arctic Ocean. All data are telemetered to a surface data logger. This unit can be exchanged with modular oceanographic sensors set at specific depths in the water as for a standard oceanographic mooring.
 
Various components of these instrument configurations include:
Long-Term Observatory
            Basal energy balance station
            ITP (CTD and DVS)
            Bottom node with CT and transmissometer
            Bottom DVS downward facing
 
Oceanographic mooring
There are several optional configurations of this cluster. The basic configuration is:
            Basal energy balance station
            Teledyne Sentinel DVS (500m range)
            2 CT mid-water nodes
            Bottom node with CT and transmissometer
            Bottom DVS downward facing
Other options for mid-water nodes include:
            5 node CT + 1 depth
            3 node transmissometer
            3 node current meter
Or:
            3 node CT + 1 depth
            2 node transmissometer
            3 node current meter (electromagnetic)
 
Within these two configurations there are two unique components:
 
ITP – Ice-Tethered Profiler
The ITP concept was developed at Woods Hole Oceanographic Institute (WHOI) for use in the arctic sea ice. RAGES version was constructed by McLane Research and is integrated with a Teledyne DVS current meter.
 
Basal Energy Balance Station (all inductive modem)
            4 CT nodes
            1 CTD node (Seabird16 IM) with O2 and transmissometer
            1 DVS upward facing
 
Abbreviations:
CT – conductivity and temperature
CTD – conductivity, temperature and depth
DVS - Doppler volume sampler current meter