SOCIB activities in the Saildrone ATL2MED mission

SOCIB participated to the Saildrone ATL2MED mission, a public-private partnership between SAILDRONE and 12 research institutions from seven countries. The mission started in November 2019 in Cape Verde, where two saildrones (Fig. 1) were deployed, collecting biogeochemical, ecological and physical measurements. The SOCIB-saildrone mission was carried out in the Western Mediterranean, South of the Balearic Islands, from 17 to 29th of March 2020 (Fig. 2), an ocean area of specific scientific interest since it is a highly energetic area, characterised by mesoscale eddies and is also a well known hotspot of biodiversity. The impact of climate change and human pressure in the islands on the ecosystem are complementary topics that will be also explored in this project.

As a result, the main initial objectives of the SOCIB-saildrone experiment were:

  • Monitoring (sub-)mesoscale features (e.g. Algerian anticyclonic eddies, shelf-slope exchanges) to better understand the processes involved in the ocean circulation and variability, as well as their potential impacts on the marine ecosystem and sea-turtle trajectories in particular.
  • Collecting ocean data to complement the observational network, filling spatial and temporal gaps, in particular monitoring and connecting the open ocean and the coastal area, including the Cabrera National Park.
  • Providing data for satellite calibration and validation of altimeter missions in the area: (1) Sentinel-3A/3B, Jason3 that aim to characterize the fine-scale variability (2) SWOT that will be launched in 2022 to provide daily high-resolution sea surface height.

SOCIB-Saildrone project

SOCIB experiments, led by Mélanie Juza and Joaquín Tintoré, had three distinct phases:

  1. Phase 1 concentrated on observing an intense mesoscale eddy, located south of Ibiza, including sea turtle tracking in the southern part of the eddy in collaboration with Dr. David March from University of Exeter.
  2. Phase 2 included the eddy monitoring in its northern boundary -by one of the saildrones- and transitioning both platforms until reaching the Marine Protected Area of the Cabrera Archipelago Maritime-Terrestrial National Park.
  3. Phase 3 focused on the self-slope monitoring south of Mallorca and Menorca Islands, including a detailed monitoring of the southern waters of Cabrera, from Southwest to Northeast, in collaboration with Cabrera Island National Park. Phases 1 and 2 open sea monitoring are a SOCIB contribution to EuroSea EU funded project, while the coastal component off Cabrera Island is a contribution to JERICO-S3 EU funded project. 

Accordingly, phase 1 of the experiment started on 17 March 2020, in the southwest of the large anticyclonic eddy south of Ibiza (0.5ºE, 37.5ºN), and finished on 29 March 2020 East of Menorca Island (4.8ºE, 39.7ºN) (see saildrone trajectories in Fig. 2). While SD-1053 navigated along the southern edge of the eddy to join the tagged sea turtle and sample its neighbour (Fig. 3), SD-1030 flowed north-eastward to monitor the eddy crossing its centre (Fig. 4).

After having navigated north-eastwards and reached the south of Mallorca, the two saildrones started together phase 3, with a detailed and intense sampling of the upper ocean conditions in the Cabrera Archipelago Maritime-Terrestrial National Park (Fig. 5) in order to understand the shelf-slope exchange processes in this hotspot of biodiversity. Finally, the saildrones monitored the oceanographic conditions along the southern continental shelves of the eastern Balearic Islands, which are privileged places for the marine life.

This mission was subject to difficult atmospheric and oceanographic conditions (intense contrary winds, ocean currents, waves, and turtle tracking) requiring a continuous adaptation of the sampling, and also to the COVID19 context confining the involved personal. We warmly thank the great SOCIB and SAILDRONE teams to having carried out this mission.

Saildrone data

The saildrones are innovative unmanned surface vehicles combining wind-powered propulsion technology and solar-powered meteorological and oceanographic sensors to collect high-resolution atmospheric, surface and sub-surface ocean data. The two saildrones, which have been deployed during the mission, are equipped with atmospheric and oceanographic sensors (see details in Fig. 6). More specifically, the saildrone SD-1030 is equipped with an ADCP and SD-1053 with an echo-sounder.

Very high-resolution oceanographic data were collected in the SOCIB-Saildrone mission:

  • 1-minute resolution: sea water temperature, sea water conductivity, sea water salinity, chlorophyll concentration, oxygen concentration and saturation.
  • 5-minute resolution: sea water current, significant wave height, wave dominant period, acoustic measurements.

Note that the echo-sounder is a very high energy-consuming sensor. Consequently, it was switched on during the phases 1 and 3, and turned off during then transitioning phase 2.

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