Sea currents

The sea currents in the area of test site are influenced by the typical semidiurnal tide in the area. The velocity and direction of the current is monitored using an ADCP (Acoustic Doppler Current Profiler) belonging to PLOCAN, which is installed periodically at 30 meters deep, as shown in the following figure.

An ADCP is an instrument that is placed on the seabed, emitting sound waves and registering information on the intensity and direction of flow throughout the water column. The data are stored in an internal memory until the instrument is recovered, next they are downloaded for processing. The following image shows an ADCP in operation.

Additionally it is available modeled currents velocity and direction data at two points further away from the coast. They were obtained from the CFSR model (Climate Forecasting System Reanalysis). The CFSR model has coupled the fourth version of the ocean model MOM (Modular Ocean Model, Griffies et al. 2004) of 0.5⁰ spatial resolution and 40 vertical levels up to 4.5 km deep.

ADCP results

So far it has been completed 3 periods of measurements in the test site after installing two ADCPs, as shown in the following table.

 

  ADCP-PLOCAN ADCP-ULPGC CFSR-Model
Number of points 1 1 2
Position 28.030472⁰N, 15.37917⁰W 28.05295⁰N, 15.40611⁰W P1: 28.25⁰N 15.25⁰W
P2: 27.75⁰N 15.25⁰W
Type of data or sensor Data obtained from ADCP-RDI Instrument Data obtained from ADCP-AWAC Modeled data
Parameters Depth (m)
Current Velocity (m/s)
Current direction (degrees)
Depth (m)
Current Velocity (m/s)
Current direction (degrees)
U and V component
Depth (m) 30 25 5
Measurement period 26 jul – 4 sep 2012
14 nov – 24 nov 2013
20 oct – 4 dic 2014
15 nov 2013 – 14 jan 2014 Jan 1980 – Dic 2009
Temporal resolution Hourly Hourly Hourly
Vertical resolution 50 cm, 60 cells 50 cm, 50 cells 1 cell

The results for the period from July 26th to September 4th 2012 are shown in the following figures, where changes in direction are clearly affected by tidal in most of the water column, remaining virtually constant surface current towards the South, according to the wind direction.

 

CFSR model results

The two current simulated points obtained from the CFSR model are significantly distant from the coast and the test site. This model spatial grid has a low spatial resolution, therefore, their results are closer to an analysis of global offshore currents than the local conditions of the test site. The rose currents is shown in the following figure for the northern point, P1: 28.25⁰N 15.25⁰W, at 5 meters deep. The point in the south, P2: 27.75⁰N 15.25⁰W, do not shows differences with respect the northern point.

Additionally, the public State Ports provides currents forecast at larger scale available on their website.

References

  • Griffies, Stephen M., Matthew J Harrison, Ronald C Pacanowski, and Anthony Rosati, 2004: A Technical Guide to MOM4, GFDL Ocean Group Technical Report No. 5, Princeton, NJ: NOAA/Geophysical Fluid Dynamics Laboratory, 342 pp.