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
As sea level rises, much of Honolulu and Waikiki vulnerable to groundwater inundation
29.03.2017 | University of Hawaii at Manoa
Researchers discover dust plays prominent role in nutrients of mountain forest ecoystems
29.03.2017 | University of Wyoming
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
29.03.2017 | Materials Sciences
29.03.2017 | Physics and Astronomy
29.03.2017 | Earth Sciences