An extremely intense El Niño event in 1983 prompted an international surveillance programme, involving the deployment of moored or drift measurement buoys and observation satellites. This research effort is proving to be fruitful. The data obtained provide a key to understanding how the two components of the now-famous two-phase system El Niño Southern Oscillation (ENSO) -El Niño and its reverse counterpart La Niña- are generated. Forecasting models for three months in advance are quite reliable. However, the knowledge acquired comes from observations which are limited in time and therefore cannot reveal any longer-term variability in the Pacific climate. This is particularly so for ENSO prediction as its strength and phasing can vary widely over a given century or from one century to another. It is therefore difficult now to determine the impact of the present-day global warming on El Niño.
With the aim of improving climate models, research teams are studying periods of the past during which the climate was different from that of the present day. They are investigating especially the extent to which the ENSO phenomenon occurred at the time with the same frequency and intensity. IRD scientists from the Nouméa centre, in conjunction with the College of Marine Science (University of South Florida), have studied a colony of Porites (massive corals) which has been building up since the mid XVIIth century. This colony yields pure signals, by way of trace element analysis involving coupled Sr/Ca and U/Ca ratio determination, on the changes in the sea surface temperature (SST) that have occurred over 350 years.
The team focused its attention on a particularly cold period (1701-1761), which occurred in the middle of the Little Ice Age (1400 to 1850 A.D.). At this time, temperatures in temperate latitudes of the Northern Hemisphere were between 1 and 2 °C lower than average figures recorded at present. Drill-core coral samples taken from near the Amédée Lighthouse on the South-West side of New Caledonia show that the Little Ice Age also prevailed in the tropical South-West Pacific, with an average cooling of around 1°C. Was El Niño, which now manifests itself in this area of the Pacific every two to seven years by a fall in SSTs (by 0.5 to 1.5°C), reinforced by this generalized cooling? The reconstitution of a composite monthly SST record over the first 60 years of the XVIIIth century has led the researchers to some surprising observations. El Niño’s behaviour then was similar to what it is now. In spite of a decrease in average temperatures, neither the strength nor the frequency of El Niño therefore appears to have been affected, even during the very coldest period.
The New Caledonia corals have, however, recorded a much more pronounced interdecadal oscillation (a period of 15 to 20 years) than is now observed : in 1720, 1730 and 1748 in particular decreases in annual average SSTs exceeded 1°C. This is an important result. The scientific community is now considering if there is interaction between El Niño (which recurs every 2 to 7 years) and lower-frequency climatic phenomena (recurrence every 10 to 60 years). The Amédée Lighthouse corals may not have shed new light on that, but they have proved they can yield useful information on these low-frequency cycles over time.
Marie-Lise Sabrie | alphagalileo
NASA examines newly formed Tropical Depression 3W in 3-D
26.04.2017 | NASA/Goddard Space Flight Center
Early organic carbon got deep burial in mantle
25.04.2017 | Rice University
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
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...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
26.04.2017 | Materials Sciences
26.04.2017 | Agricultural and Forestry Science
26.04.2017 | Physics and Astronomy