Moored Arrays

A mooring is a type of underwater platform which is used by oceanographers to make time series measurements of ocean variables (e.g., temperature, salinity, current speed and direction, dissolved oxygen, etc). It is characterised by a weight at the bottom to anchor it on the seabed, and a line (wire or rope) which is held upright by attached flotation. Along the line are installed various sensors to measure the parameters of interest, sampling at user-programmed rates (from <1-second intervals up to hourly or longer). Moorings can be deployed in the ocean to make measurements over extended periods of time; typically deployment durations can be from a few weeks for a short process study during a single oceanographic cruise, or up to 2 years between two oceanographic cruises (deployed on the first, and recovered on the second). Typically, the instruments installed are self-logging (they record the data onboard) and are only downloaded once the mooring is recovered onto the ship.

A high resolution mooring array

While an individual mooring can be deployed with a single sensor (a simple anchor, release mechanism, rope, sensor and float), recent applications of this technology have shown that arrays (a configuration consisting of multiple individual moorings, in a distributed configuration) can yield much more information about the ocean. These have included (from 2004) the possibility to measure the strength of the “great ocean conveyor” using an array of 10 moorings and individual latitude/longitude positions which, when combined, enable the calculation of the time-varying ocean circulation spanning the 6000 km width of the Atlantic. More recently (from 2012), nested arrays of moorings (a square of moorings inside a larger square of moorings; or a triangle of moorings inside a larger triangle of moorings) have been used to quantify processes occurring at the ocean submesoscale (1–10 km horizontal scales) and their interaction with processes at the mesoscale (10–100 km horizontal scales). The requirement for the calculation of gradients also sets the requirement for accuracy of instruments (high accuracy), and the timescales of the processes (1 day to 1 month, with seasonal fluctuations) sets the sampling rate requirements (typically hourly) and duration of the deployment (1 month to 1 year or longer).

Equipment at IfM EO

  • Acoustic releases and deck box
  • moored CTDs (e.g., Seabird microCATs)
  • moored current meters (e.g., Nortek Aquadopps)
  • moored velocity profilers (e.g., 150kHz and 75kHz ADCPs)
  • moored thermistors (e.g., RBR soloT and TR-1050)
  • PIES 6.2b (Pressure-equipped inverted echo sounder)

Publications (selected)

Moored (and other) AMOC measurements

Methods to treat drift in bottom pressure sensors

High resolution mooring arrays