Saildrones and SOCIB: Extending In Situ Observation in the Balearic Islands

The Mediterranean Sea is one of the most thoroughly studied bodies of water in the world thanks to its geopolitical importance since the early days of human civilization. It is considered to be a small-scale ocean in which many of the processes found throughout the world’s oceans occur, making it especially interesting for physical, climatic, and environmental studies. During the 2020 Saildrone Atlantic to Mediterranean (ATL2MED) mission, two saildrones will perform a series of sub-missions, each focused on a critical aspect of this extremely energetic basin.

In partnership with the Balearic Islands Coastal Observing and Forecasting System (SOCIB), the saildrones collected oceanographic and biogeochemical data in the vicinity of the Balearic Islands to improve understanding of mesoscale and sub-mesoscale variability, their interaction with general circulation in the Mediterranean Basin, and potential impacts of climate change on the marine ecosystem.

Mallorca, Ibiza, Menorca, and Formentera are the largest and most well-known of the Balearic Islands, but there are many minor islands and islets that are part of the archipelago. The islands are located in the Atlantic/Mediterranean transition area about 370 nautical miles northeast of the Strait of Gibraltar, the only natural connection between the Mediterranean Sea and the global ocean. This region is a “hot spot” of biodiversity where mesoscale and submesoscale dynamics are of particular relevance. 

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The southern area of the Western Mediterranean (the Algerian Basin) is characterized by the intense Algerian Current flowing eastward along the African coast, and persistent mesoscale eddies generated by instability within the current. The Balearic Islands sub-mission will look at eddy formation and propagation and associated vertical exchanges and how they interact with general circulation.

“The saildrone mission is a great opportunity in the southern Balearic Islands, which is a historically undersampled oceanic region and significantly impacted by climate change and human pressure,” said Prof. Joaquin Tintoré of SOCIB and the Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB) and the sub-mission’s principal investigator. 

SOCIB is a multi-platform distributed and integrated system that collects in situ data in the Western Mediterranean Sea using moorings, gliders, surface drifters, Argo floats, HF radar, sea turtles, and research vessels, contributing knowledge to European Union-funded initiatives and projects. “This multi-platform approach is needed to understand ocean variability at the mesoscale, where the maximum kinetic energy is observed,” explained Tintoré.

One of the sub-mission’s objectives is to assess how the Saildrone platform can complement the existing observational network. “This survey will complement and increase the observational network, filling spatial and temporal gaps, in particular, monitoring and connecting the open ocean and the coastal area, including the shelf-slope area of Cabrera National Park,” said Dr. Mélanie Juza, co-PI of the sub-mission.

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Cabrera Archipelago Maritime-Terrestrial National Park, located on Cabrera Island south of Mallorca and extending southward and eastward along the continental slope, is home to numerous species of birds and a wide variety of endemic plants and its coastal landscape is considered one of the best-preserved areas of the Spanish coast.

Oceanographic turtles equipped with satellite transmitters in collaboration with the Save the Med Foundation contribute a wealth of information about marine diversity and dynamic ocean management, as well as improve understanding of marine species. The ATL2MED saildrone equipped with an echo sounder monitored oceanographic conditions in the area of a tagged turtle, which was navigating near the strong anticyclonic eddy south of Ibiza.

The saildrones could also provide data for calibration and validation of the many satellites that regularly pass over the region—Sentinel-3A, Sentinel-3B, Jason-3, and others—to characterize fine-scale variability. The Surface Water & Ocean Topography (SWOT) satellite altimeter mission, expected to launch in 2022, will provide daily high-resolution sea surface height in selected areas of the global ocean, including around the Balearic Islands. Data about ocean currents collected by Saildrone is expected to be especially valuable in the areas that will be covered by the SWOT satellite.

ATL2MED is a collaboration between Saildrone and more than two dozen oceanographic research institutions from seven countries to address a variety of scientific objectives. The saildrones sail next toward Nice, where they will study air-sea carbon flux between France and Corsica, and then into the Tyrrhenian Sea off the west coast of Italy where they will continue to study carbon near fixed-point observatories and biogeochemical variability between fixed stations. The mission will conclude in Trieste, Italy, in the Adriatic Sea.