Climatic fluctuations close to the equator show a different pattern to climate change in the Arctic and Antarctic. In the tropics distinct 11500 year fluctuations between wet and dry periods can be clearly identified which do not occur in temperature reconstructions of polar ice cores.
The investigations of the climate of the last 25000 years in tropical Africa show that dry phases prevailed during lower solar radiation in March and September, which caused the following rain period to be less intensive.
This emphasises the significance of hydrological variations in regional climate change, as was formulated by a European consortium of earth scientists under the direction of Professor Dirk Verschuren (University of Gent, Belgium) in the latest issue of the science magazine "Nature" (Vol. 462, 7273).
Seasonally recurring rain periods are the decisive feature of the tropical climate, and are of existential importance for the life of the people there. In order to determine the reasons for the fluctuations in the intensities of the rain periods, the European research team examined the climate of equatorial East Africa on long-time scales. "To date there has been hardly any data on climate change in the tropics. Variations in the temperature do not a play a major role in comparison to hydrological changes", explains Achim Brauer from the GFZ German Research Centre for Geosciences: His working group, together with his European colleagues, analyses the deposits in the Challa-Lake, a crater lake at the eastern foot of the Kilimandscharo.The GFZ scientists retrieved, for the first time in this region, annually laminated sediment cores from the lake bottom, down to depths of 21 meters. "With this, the sediment core covers the last 25000 years" explains Achim Brauer. "Detailed microscopic and geochemical investigations of the individual sediment layers deliver climatic information on a very exact time scale". This world-wide first long profile of such lake deposits in the tropics is further supplemented with modern high-resolution geophysical data.
The results show that the changes from wet to dry phases vary on the same temporal sample as fluctuations in the solar radiation, which are caused by cyclic changes in the Earth's orbit around the sun. In particular the rotating of the Earth's axis at a rhythm of 23000 years becomes obvious, which consequently leads to an alternating maximum solar radiation every 11500 years in the southern tropics and in northern tropics. These radiation maxima in turn steer the position and the intensitiy of the inner-tropical convergence zone(ITCZ), the rain-rich cloud belt close to the equator. The ITCZ is strongest there, where the radiation is intense and evaporation is high.
It can, thus, be proven that Earth's orbit around the sun and associated regional fluctuations of solar radiation, even if these are relatively weak, have a large influence on the climate at the equator. The question as to whether these tropical climatic fluctuations have influenced the global climatic history still remains open.
This research work was supported within the framework of the ESF-EuroCORES Programme "EuroCLIMATE", with national funding through the DFG, FWO Flandern, NWO and NERI.
Photos of Challa-Lake can be found here: http://www.gfz-potsdam.de/portal/-?$part=CmsPart&docId=2517120
F. Ossing | EurekAlert!
NASA sees the end of ex-Tropical Cyclone 02W
21.04.2017 | NASA/Goddard Space Flight Center
New research unlocks forests' potential in climate change mitigation
21.04.2017 | Clemson University
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...
Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.
A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
21.04.2017 | Physics and Astronomy
21.04.2017 | Health and Medicine
21.04.2017 | Physics and Astronomy