A glimpse into deep ocean-floor structures
The objective of the upcoming expedition of the Research Vessel SONNE in January is a critical location for climate studies in the Indian Ocean. Dr. Gabriele Uenzelmann-Neben of the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI) is the chief scientist for Expedition SO272. Scientists from MARUM – Center for Marine Environmental Sciences at the University of Bremen will also be participating.
The target site for the SONNE is the region of the Kerguelen Plateau, located in the middle of the Indian Ocean. The plateau is one of the world’s many Large Igneous Provinces, areas composed of massive magmatic rocks.
The magma here was extruded through the Earth’s crust and deposited between 50 and 110 million years ago, primarily in the form of flood basalts. These flood basalts release immense amounts of greenhouse gases into the atmosphere and can lead to increases in global temperature. There is no question that Large Igneous Provinces have a significant impact on climate. But researchers still do not fully understand how these kinds of provinces and plateaus are formed.
But it is more important for the team on board the Research Vessel SONNE to learn how the topography of the plateau affects deep-sea currents, and how it has affected them over the past millions of years. The primary focus is on the Antarctic Circumpolar Current and the Antarctic Bottom Water, as viewed in a global context. These water masses flow with the Earth’s rotation and connect the Atlantic, Pacific, and Indian Oceans. The Kerguelen Plateau stands like a gigantic barrier in the path of the most powerful currents on Earth. With an area of more than 1.2 million square kilometers, it is about twice the size of France.
“The plateau acts as an obstacle to the currents. They are diverted by the plateau and form characteristic sediment structures in the subsurface. We map these structures and analyze their changes through time. We thus obtain information about the activity of the currents,” explains chief scientist Gabriele Uenzelmann-Neben of AWI.
The paths of the water have changed in strength over the past 70 million years, but also due to tectonic changes. But most importantly, the region of the Kerguelen Plateau is situated in a key position with regard to global climate changes. This is an excellent area to study the climatic interactions and changes between Antarctica as compared to regions in the lower latitudes. Changes in structures such as drift sediments are documented at very high resolution in the area of the Kerguelen Plateau. This means that during this time a large volume of sediments was deposited. This high-resolution geological climate archive is the target of the expedition and it will be sampled by gravity coring. As the primary focus of the cruise, seismic studies will provide a deep insight into the structures hidden beneath the sea floor. However, important findings from the newly acquired data should also help to encourage further international research projects in this key climatic region.
"In order to better assess these global interactions of climate, we have to reconstruct the history of the complex Earth System as accurately as possible at key points," explains Dr. Thomas Westerhold of MARUM. “The SO272 cruise to the Kerguelen Plateau, in combination with further planned research expeditions, will serve to achieve a better understanding of the dynamic processes in the high latitudes, which react very sensitively to global changes.”