E2-M3A

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Project title and acronym

COMbined testing of new acoustic profilers with Biochemical Optodes in the Adriatic Sea [COMBO]

Host facility

E2-M3A

Modality of Access

MoA2 – Partially remote (the presence of the user is required at some stage, e.g. for installing and uninstalling an instrument)

Description

A new type of Acoustic Doppler Current Profiler (SeaguardII-DCP) was recently developed at Aanderaa. It has unique acoustic features including: Broadband and Narrowband, Automatic 3 beam/4 beam selection for optimal data quality and object avoidance, Simultaneous Upward and Downward profiling by connecting two acoustic sensors, Spread or Burst mode and the ability to remotely measure the top cm surface currents. This technology has not been properly evaluated in clear/oligotrophic waters, which is known to decrease the acoustic range and performance. We suggest adding one self-recording unit with two acoustic sensors to the underwater cage of E2-M3A and collecting at least one full year of data. Apart for evaluating the technology the instrument will give valuable information about seasonal dynamics of the upper mixed layer. We also suggest to add sensors to this and to another similar instruments placed close to the bottom on the Sub-surface mooring. The suggested sensors are Aanderaa optode prototypes for pH and pCO2 complemented by standard sensors for O2, Salinity, Wave/Tide, Temperature and Current. The rationale behind the deeper instrument is a better assessment of the Adriatic Deep Water formation and spreading, and how they contribute to change the deep and bottom water conditions in the entire South Adriatic, both on a short and long time-scale. Here, high frequency data of pH/pCO2/O2 will add important information about the carbon cycle, the origin and age of the dense waters flowing along the bottom into the deeper parts, which origin is attributable to local phenomena acting in the northern Adriatic. In addition, the accuracy and stability of the new sensors will be evaluated.

The sensors placed on the SeguardII-DCP, attached to the cage few meters under the sea surface, will be side-by-side compared with existing sensor for pH and pCO2 but would also open new possibilities to study rapid changes in the carbon cycle in the upper mixed layer because the optode technology can be sampled much faster than existing technologies which are power hungry and complex (e.g. pumps, equilibrators, scrubbers, reagents).

In addition to piggybacking two compact self-recording instruments to the E2-M3A observatory, we suggest to take advantage of the OGS Oceanographic Calibration Centre for pH, pCO2 and O2 to improve/verify sensor calibrations before and after the deployment.