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
World’s oldest known oxygen oasis discovered
18.01.2018 | Eberhard Karls Universität Tübingen
A close-up look at an uncommon underwater eruption
11.01.2018 | Woods Hole Oceanographic Institution
On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.
We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
22.01.2018 | Life Sciences
22.01.2018 | Power and Electrical Engineering
22.01.2018 | Power and Electrical Engineering