Friday, December 8, 2023

13,000 years ago, the flow of water from the Mediterranean to the Atlantic was double what it is today

About 13,000 years ago, a climatic crisis caused a thermal drop in the northern hemisphere, an episode of intense cold known as ‘Younger Dryas’ which doubled the flow of water from the eastern Mediterranean into the Atlantic Ocean through the Strait of Gibraltar, according to a study led by the University of Barcelona (UB).

The investigationwhich publishes the magazine ‘Communications Earth & Environment’, has reconstructed the changes in the Mediterranean during the climate change the most intense in the last 13,000 years and, according to its authors, could help predict the potential effects of global change in the Mediterranean at the end of the 21st century.

The work has been prepared by Sergio Trias-Navarro, Professor Leopoldo Pena and Professor Isabel Cacho, from the Consolidated Research Group (GRC) in Marine Geosciences from the Faculty of Earth Sciences of the UB, and experts from the La Sapienza University of Romefrom the University of Palermo and the Federal Polytechnic School of Zurich (ETH).

Cacho recalled that ‘Younger Dryas’ is the episode of climate change “more intense of the last 13,000 years and with the greatest repercussion on a planetary scale” and marked the beginning of the Holocene, the period interglacial current.

“During the Holocene there has also been variability climate change, such as the episodes known as the little ice agethe medieval climatic anomaly or the Roman warm period, but this climatic variability had a lower relative intensity, with different regional climatic expressions, without the capacity to generate changes at a global level”, Cacho pointed out.

The work supports the hypothesis that the increase in the contribution of salt from the Mediterranean to Atlantic waters during the ‘Younger Dryas’ was key to reactivating the circulation of the North Atlanticwhich generated rapid warming in Europe and the Mediterranean that marked the beginning of the Holocene.

“The bodies of water from the Mediterranean are one of the main sources of salt in the North Atlantic. The salinity of the waters is an important factor in oceanography because it determines the density of water masses and is a key process in the formation of deep waters in the Atlantic and the engine of global ocean circulation”, highlighted Trias-Navarro.

As in other previous GRC work in Marine Geosciences, the team has applied the technique innovative use of radiogenic neodymium isotopes as geochemical tracers to reconstruct past oceanographic conditions.

Compared with other types of geochemical tracersneodymium isotopes have the advantage that they do not interact or are affected by biological processes”, highlighted Leopoldo Pena.

“This technique allows us to go beyond time and can be applied in reconstructions oceanographic data from both the present and the past and makes it possible to know the dynamics of the ocean and reconstruct oceanography long before we could observe or measure it ourselves”, added Professor Pena.

Researchers have lamented that a good part of the studies Oceanographic studies on the Atlantic do not consider the Mediterranean and minimize the role of Mediterranean waters in the Atlantic circulation.

They have also recalled that the last report of the Intergovernmental Panel on Climate Change (IPCC) presents the ‘Younger Dryas’ as an example of the foreseeable changes in rainfall that will take place in the Mediterranean as a result of an expected reduction in the North Atlantic circulation.

“On the other hand, according to the projections By the end of the 21st century, the circulation of the Mediterranean will weaken, and consequently its contribution to the Atlantic Ocean will also weaken”, predicted Cacho, who defends that “in the current context of climate change, studies like this are more necessary to know better the sensitivity of the Mediterranean circulation with respect to different climatic situations”.

According to Cacho, “our work reveals that the change of expected aridity by the end of the century it is capable of inducing an intensification of the Mediterranean circulation, although the expected warming could counteract this effect. For this reason, it is necessary to better understand the relative weight that these two variables, temperature and humidity, have had in the evolution of the circulation of the Mediterranean”.


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