Report on the Mastodon2D mooring system

Type Contract report
Date 2019-07-19
Language English
Ref. JERICO-NEXT-WP3-D3.5-190719-V1.1
Other localization
Author(s) Lazure PascalORCID1, Pairaud IvaneORCID1, Leizour Stephane1, Puillat IngridORCID1
Version 1.1

Temperature distributions on continental shelves (depth < 150m) are often complex because the many physical processes induce very high spatial (both horizontal and vertical) and temporal variability. Temporal variability extends from a few tens of minutes for solitons (internal wave), a few hours for internal tide and inertial waves to a few days for upwelling or sub mesoscale dynamics.

In the 1980s, satellites provided access to knowledge of surface temperatures. On the other hand, the internal temperature structure still requires in-situ measurements, which leads to the deployment of moorings at sea. These operations are often expensive and risky because the coastal zone is generally subject to intense activities such as fishing and sea conditions can be very harsh.

Profiling systems exist, as an example, they are either derived from the drifter ARVOR C or at the fixed location such as the WirewalkerTM. However, these systems are expensive, which limits the number of deployments and does not allow time series to be obtained in a fixed immersion with a fine time resolution (for a depth of 150m, a vertical profiler speed of 1m/s only allows the bottom temperature to be measured every 5 minutes).

Our development avoids these disadvantages by proposing the development of a system equivalent to thermistor chains at a much lower cost. The counterpart is that the fine description of the vertical profile depends directly on the number of probes on the line and will never be as fine as that provided by a profiler. On the other hand, it allows to obtain at a low cost, time series at the fixed station and at the selected immersions.

The Mastodon2D mooring (t-z, description of temperature variations over time on the water column) is an extension of the Mastodon mooring (Lazure et al., 2015) which allows to measure the temperature evolution near the sea bottom. The innovation does not lie in the measured parameter (thermistor chains have existed for decades) but in the possibility to deploy numerous moorings thanks to their low cost (<2000 €, at least 10 times less than conventional thermistor systems) and providing good quality data at high spatial resolution.

The system is described in detail and the first deployment with scientific benefits is briefly presented to illustrate the effectiveness of such development. Future developments and industrial challenges are then discussed.

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