A new study carried out by an international team and involving the Geoma, Marine and Environmental Geology research group of the Marine Research Center of the University of Vigo (CIM-UVIGO), analyzed the chemical composition of ocean sediments to reveal widespread changes in the circulation of the Atlantic Ocean related to high-frequency climate changes over the last 25,000 years. The results obtained, now published in the journal Nature Communications, provide new insight into the interaction between ice melting, ocean circulation and climate change, which has numerous potential implications for future scenarios of change in terrestrial systems associated with global warming.
“These discoveries demonstrate the important role that ice melting processes play in the decrease in the intensity of the thermohaline circulation and this phenomenon is of particular relevance for the future due to the acceleration that ice melting processes are currently experiencing in high latitudes”, explains researcher Kais Jacob Mohamed Falcón, one of the members of the research team signing the article, led by researcher from the University of Bristol Hong Chin Ng. “In this sense, the results presented in this article can be used to analyze and verify the response of climate models to changes in the contribution of waters from ice melting and ocean circulation during these rapid climate changes”, emphasizes the researcher, member of Geoma.
Rapid and wide-ranging changes in climate
The article provides new evidence that after the last glaciation, which ended around 20,000 years ago, there were rapid and large-scale changes in climate, atmospheric carbon dioxide content and the global volume of continental ice. “One of the hypotheses explaining these changes considers that alterations in the circulation of the Atlantic Ocean played an important role as a driver of these changes, however, direct evidence of this mechanism has been difficult to find until now,” explains the researcher, adding that in this study they analyzed radioactive elements in ocean sediments in order to obtain a more precise reconstruction of the vigor of the Atlantic circulation in the past and its relationship with changes in the volume of continental ice and climate changes during the last deglaciation.
49 days aboard the oceanographic research vessel James Cook
To reach these conclusions, Kais Jacob Mohamed Falcón and the rest of the participating researchers embarked for 49 days –between October 13 and November 30, 2013- aboard the oceanographic research vessel James Cook, of the National Environmental Research Council of the United Kingdom. The campaign departed from Tenerife towards the waters near Sierra Leone, later crossing the Atlantic to Trinidad and Tobago.
Along this journey, they obtained marine sediment cores that they later analyzed. “The samples were analyzed at the University of Bristol, although a good part of these techniques are already available at our University,” explains Mohamed Falcón, while emphasizing that this has already allowed him to develop similar studies on sediments from the Interior Basin of Galicia, a submarine depression more than 3,000 meters deep that extends from north to south about 100 kilometers from the Galician coast.
Studies on the Atlantic Iberian margin
The data obtained were analyzed together with those already existing in the scientific literature on this subject and which met strict quality criteria, both from low latitudes and from mid-latitudes and subpolar. In this way, it was possible to verify a coherent behavior of the thermohaline circulation in the Atlantic, characterized by different states in the western and eastern basins, in which for latitudes below 40º N, a more vigorous circulation was observed during the last glacial maximum compared to the current one at depths of 2.5-3.5 km.
“We found that during the Heinrich Stage 1, the coldest event since the last glacial maximum, the ocean circulation suffered a slowdown in two phases associated with two episodes of ice melting, one coming from Eurasia and the other originating in North America,” emphasizes the researcher, while explaining that these findings are consistent with other studies carried out by the Geoma group on the Iberian Atlantic margin, using magnetic, sedimentological properties and strontium and neodymium isotopes.
