New data about the connection between the Mediterranean and the Atlantic
José Pichel Andrés/DICYT Between November 2011 and January 2012, the most important oceanography research ship in the world, the Joides Resolution, sailed through Gulf of Cádiz and the coast situated in the South of Portugal searching for marine sediments which could help to explain the history of water exchanges between the Mediterranean Sea and the Atlantic Ocean through the Strait of Gibraltar, a phenomenon with numerous implications in the study of climate. Since then, scientists have been analyzing data and, as a result, the magazine Science publishes this expedition’s first results, in which José Abel Flores and Francisco Sierro, researchers of the University of Salamanca participated.
This work “confirms that the Mediterranean and the Atlantic have been connected for about less than six million years”, explains José Abel Flores to DiCYT, although the most meaningful interaction has not been established until the end of Pliocene about three million years ago. Previously, the passage was closed during several hundreds of millennia. The most significant aspect of the current between the two basins is that the Mediterranean flows a great quantity of water to the ocean, saltier and warm; and, consequently, denser, which is merged and it is compensated by the entrance of more superficial waters in opposite direction.
Thanks to the Expedition 339 of Integrated Ocean Drilling Project (IODP), Mediterranean Outflow, more details about an essential relation to understand North Hemisphere’s climate are known. The exchange that happens in the Strait of Gibraltar, which flows saltier and warm waters to the Atlantic, has influence in the circulation of oceanic currents, marked by its density, which depends precisely on salinity and temperature. This phenomenon has influence in the evaporation of oceanic waters; and, consequently, in the precipitations, which determine the river flow of the Mediterranean basin; and, in turn, it determines the discharge of waters in the Atlantic. Studying this complex equilibrium is essential to understand the climate and its evolution along millions of years.
Microscopic fossils
The contributions of the scientists of the University of Salamanca are centered in the field of Micropaleontology. In particular, Francisco Javier Sierro is a micropaleontologist and an expert in foraminifera, microscopic animals that belong to zooplankton, in addition to carrying out works in geochemistry. On his behalf, José Abel Flores is specialized in calcareous nannofossils. The work of a ship like the Joides consists in recovering sediments of the marine bottom which may be thousands of meters deep and the existing microfossil analysis is essential to date them quickly. That is, the type of fossils found in the place offers a great deal of information. “It gives an idea of ages and it may be used to characterize environments”, the researcher of the University of Salamanca points out.
Another essential aspect is that “the bottom current erodes and accumulates sediments”, José Abel Flores comments. The Mediterranean water, denser, is merged more than 1.000 meters deep, excavating the bottom and producing deep canyons. In other places, the transported material generates mountains of mud and sand. These sediments are called contourites, because the currents that produce these deposits follow the contour of marine beads and, for scientists, they are a great archive where climatic change and tectonic activity are registered, in this case, of the last 5.3 million years.
Hydrocarbons
The contourite sands phenomenon is more important than scientists expected and the sand layer reaches out about 100 kilometers from the Strait of Gibraltar. This new information is another great contribution of this research, mainly under the economic point of view, since these sands are an ideal environment for the accumulation of hydrocarbons and gas. “They are clean and porous sands capable of accumulating fluids covered by clays and can storage big volumes of hydrocarbons”, the scientist of Oceanic Geosciences Group of the University of Salamanca comments. “The Gulf of Cádiz is a reference in the definition of contourite sediments in other parts of the planet as well, places where petrol companies may be interested in making drillings, where this type of sediment is better known”, he adds. These sands are deposited in a more different way than expected, so these findings are very important for administrations and enterprises.
On the other hand, another important aspect studied by the researchers of Salamanca is the existence of sedimentation gaps or absences, which are related to events of tectonic plates. This work also helps to understand the connection between the climate, very dependent on the ocean, and the tectonic plates shifting, which may modify it.
Even though publishing this work in Science is very important, the article is only “the first touch” of the entire work. More precisely, last week, the researchers of the University of Salamanca and their partners in the expedition have participated in a scientific meeting in Tarifa, where the next publications have been planned, especially the ones related to North Hemisphere’s recent climate in the last million of years.
The University of Salamanca’s exceptional participation
35 scientists and 14 nationalities have participated of the voyage, which left the Azores and reached Lisbon after two months. The fact that the same university has contributed with two scientists in an IODP mission is exceptional and it may be explained due to José Abel Flores and Francisco Sierro’s specialization in microfossils. In addition, Javier Hernández-Molina, professor of the University of Vigo, was the leader of the expedition. The Spanish participation became complete with Francisco Jiménez-Espejo of the Sciences of the Earth Andalucian Institute (center of CSIC and the University of Granada), and Estefanía Llave Barranco of the Spanish Geological and Mining Institute (IGME), as a national waters’ observer. This is an example of an unprecedented participation of five Spanish scientists as well as others who work in France and Japan and came to represent their countries.
The scientists cooperated with their work’s diffusion through DiCYT Agency blog, 'On board a Joides', where all the participants, Spanish and from other countries, have left impressions. Besides, the boat arrival in Lisbon has been an opportunity for Salamanca’s students and professors to know the most important oceanographic research ship of the world.
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Onset of Mediterranean outflow into the North Atlantic. F. Javier Hernández-Molinaarrik A. V. Stow, Carlos A. Alvarez-Zarikian, Gary Acton, André Bahr, Barbara Balestra, Emmanuelle Ducassou, Roger Flood, José-Abel Flores, Satoshi Furota, Patrick Grunert, David Hodell, Francisco Jimenez-Espejo, Jin Kyoung Kim, Lawrence Krissek, Junichiro Kuroda, Baohua Li, Estefania Llave, Johanna Lofi, Lucas Lourens, Madeline Miller, Futoshi Nanayama, Naohisa Nishida, Carl Richter, Cristina Roque, Hélder Pereira, Maria Fernanda Sanchez Goñi, Francisco J. Sierro, Arun Deo Singh, Craig Sloss, Yasuhiro Takashimizu, Alexandrina Tzanova, Antje Voelker, Trevor Williams, Chuang Xuan. |