Thanks to the samples taken in a paleoceanographic expedition, a team of researchers carried out the first analysis of high temporal resolution of the sediments of the place, which allowed them to determine the variability in the flow of the Antarctic Circumpolar Current. The results were published in the scientific journal Paleoceanography and Paleoclimatology.
Andrea Navarro, IDEAL Center. Its waters are considered the stormiest of the planet. However, it is not only known for the strong winds and frequent storms that hit ships trying to cross it, but also because it separates America from the white continent. The Drake Passage is a narrow passage through which the Antarctic Circumpolar Current flows, which is driven by the West Winds and constitutes the largest system of currents on the planet, connecting the main ocean basins.
In 2016, an international and multidisciplinary team of scientists participated in the expedition PS97 “PaleoDrake”, organized by the Alfred Wegener Institut (AWI) and led by Dr. Frank Lamy. After spending more than 50 days aboard the German icebreaker Polarstern, the researchers collected various samples from ocean environments that are poorly studied because they are difficult-to-access climate systems. In that campaign, 30 sediment cores were collected, which were obtained approximately 300 meters from the seabed of the Drake Pass.
With one of these witnesses, scientists from German and Chilean institutions, among them the Center for Dynamic Research on High Latitude Marine Ecosystems (IDEAL) of the Austral University of Chile (UACh) and the COPAS Sur-Austral Oceanographic Center of the University of Concepción (UdeC), made the first long-standing, high temporal resolution record of the Antarctic Circumpolar Current at the Drake Passage. To date, the longest record did not exceed 65,000 years.
The research, recently published in the scientific journal Paleoceanography and Paleoclimatology, addressed the 1.3 million-year-old analysis, the most extensive historical sediment record to date in the area. Thanks to it, the scientists determined that the flow of the Antarctic Circumpolar Current through the Drake Passage varies on a glacial – interglacial scale: During cold periods it flows slower and in warm periods faster.
The results of the work come from samples obtained in the Subantarctic Front, which were laboratory analysed and dated. Through the X-ray scanner, its sedimentological properties and finally its relationship with other environmental variables were determined.
“The Drake Passage is approximately 800 kilometers wide, it is the narrowest point of the Antarctic Circumpolar Current and it acts as a bottleneck with the flow of it. This research shows that the temporal changes of this important current occur following climatic variations on a global scale,” explains the geologist and PhD student of the UdeC, María Toyos, leader of the study.
The study is especially relevant given that it is the first time that there is a high-resolution, long-time scale record of current variations in the sub-Antarctic area, and where there are few geological studies given the difficulty of accessing it. To date, in the Southern Ocean, there were only two other investigations of a similar time scale: one east of New Zealand (1.2 million years) and another east of the Kerguelen Islands (500 thousand years.)
Variations in the flow of the Antarctic Circumpolar Current, which connects all the oceans and, therefore, distributes polar properties (such as oxygen, nutrients, and salinity,) can affect the global circulation pattern.
Recent studies have shown that wind stress has strengthened significantly in recent decades and is expected to continue to do so in the future. This could produce an increase in the transport of the Antarctic Circumpolar Current through the Drake Passage and with it an increase in the inter-ocean basin exchange. The data obtained in this new research could help feed models and improve predictions of future climate change scenarios.
Read the scientific study here.