Today a pronounced and stable freshwater layer at the surface originating from inputs of the large Russian rivers almost completely prevents any significant deep water formation in the Arctic Ocean itself. The results of Brian Haley and colleagues from the IFM-GEOMAR now show that this was an exception rather than the rule for most of the past 15 million years.
The Kiel team made their discovery when they carried out geochemical analyses on sediments of the Arctic Coring Expedition (ACEX, Leg 302 of the Integrated Ocean Drilling Program (IODP)) and of a RV Polarstern expedition, which had been recovered near the North Pole on the Lomonosov Ridge between 1.000 und 1.200 m water depth. They reconstructed the seawater isotope ratio of the element neodymium (143Nd/144Nd) from the sediments. The Nd, which has characteristic isotope ratios in rocks as a function of their type and age, is transported to the ocean through weathering, where it provides information on the sources of water masses. To their surprise, the geochemists found that the isotope signature of the seawater was strongly different from the present day values, with the exception of the warm periods of the past 400.000 years. “It is even more surprising that this isotope signature indicated a pronounced influence of the weathering of basaltic rocks”, says Brian Haley. On the Circum-arctic landmasses such rocks, however, only exist in the form of the Siberian “Putorana flood basalts”.
From this geologically unique setting and taking into account the evolution of the continental ice sheets of the past 140.000 years, it was then possible to reconstruct the circulation history of the deep Arctic Ocean. The signature of the basalts can only have arrived at 1.000 m water depth in the central Arctic Ocean if vast amounts of new sea ice formed near the basalt areas in the Kara Sea area. How did the signature arrive at the seafloor? “During sea ice formation the salt of the sea water freezes out and is rejected, thereby forming highly saline brines, which were denser than the surrounding sea water. These brines sank and transported the dissolved Nd isotope signature of the basalts to the sea floor where the sediment cores were recovered”, explains Martin Frank, co-author of the study. Further, the obtained Nd isotope variations imply that the inflow of Atlantic waters was significantly reduced during most of the past 15 million years and during the glacial periods of the past 400.000 years. This also suggests that during these periods of time the main area of Atlantic deep water formation was not located in the Norwegian-Greenland Sea, similar to today, but further south.
The arctic IODP ACEX drilling project was coordinated by the European consortium ECORD (European Consortium for Ocean Research Drilling). This organization consists of partners from 17 European nations participating in the „International Ocean Drilling Programme“. ECORD is also responsible for the planning and coordination of special operations, for which normal drilling vessels cannot be used, as was the case for the ACEX project. For such purposes special platforms are used to achieve the scientific goals.
Andreas Villwock | alfa
Smart Data Transformation – Surfing the Big Wave
02.12.2016 | Fraunhofer-Institut für Angewandte Informationstechnik FIT
Climate change could outpace EPA Lake Champlain protections
18.11.2016 | University of Vermont
Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.
Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
09.12.2016 | Life Sciences
09.12.2016 | Ecology, The Environment and Conservation
09.12.2016 | Health and Medicine