Navigation Links
El Niño affected by global warming
Date:12/20/2007

The climatic event El Nio, literally the Baby Jesus, was given its name because it generally occurs at Christmas time along the Peruvian coasts. This expression of climatic variability, also called El Nio Southern Oscillation (ENSO), results from a series of interactions between the atmosphere and the tropical ocean. It induces drought in areas that normally receive abundant rain and, conversely, heavy rainfall and floods in usually arid desert zones. Scientists term this phenomenon a quasi-cyclic variation because its periodicity, which varies from 2 to 7 years, shows no regular time pattern. Research conducted over the past 25 years, by oceanographers, climatologists and meteorologists has much improved knowledge on the mechanisms generating an El Nio event. However, possible influence of other systems of climate variability on the ENSO regime is more difficult to fathom. More particularly, it is not known if the intensity and frequency of the event is susceptible to modification in a situation of global warming.

The research work recently published by a team of Chilean and IRD scientists sheds new light on El Nios variability. Several geochemical factors contained in a drill core sediment sampled from 80 m depth under the Bay of Mejillones, in northern Chile, were determined. Analysis of breakdown byproducts from diatoms, unicellular planktonic algae, yielded an accurate trace of this regions trends in sea surface temperature between 1650 and 2000. Data for the period 1820-1878 showed a fall of over 2C. This temperature decrease was also detected in two cores collected near the South-American coasts, over 1000 km to the North and South of Mejillones.

These samplings confirmed that the decrease in ocean temperature observed from 1820 affected the whole Pacific seaboard, from central Chile up to the North of Peru. All the oceanic area situated on the path of the Humboldt current system was therefore the scene of significant cooling during this period. This conclusion brings a paradox, seeing that the beginning of the XIXth Century coincided with the end of the Little Ice Age which came at the same time as a warming of the Earth.

Complementary analyses on certain minerals contained in the sediment samples confirmed that these minerals were transported by the winds from the continent. Therefore the reinforcement of such prevailing winds, the trade winds, would have favoured the rise of colder waters up from deeper reaches, along the Pacific coasts of South America, by pushing the ocean surface layer westwards. Confirmation of this hypothesis came from measurement of the organic carbon flux which is directly linked to growth in nutrient concentration. The increase in this flux accords with the phase of falling sea temperatures between 1820 and 1878 which proves that the rise in nutrient concentration stems from a rising up of cold water by the process of upwelling (2).

The hypothesis the researchers postulate suggests that, in a situation of climate warming like the one that followed the end of the Little Ice Age, the large continentocean temperature (and hence thermal) contrast would be responsible for this accentuation of the trade wind regime. Whereas the Atacama, a coastal-zone desert, warmed rapidly during this period, the sea surface temperature would have risen much more slowly. The long-term persistence of a substantial temperature difference between ocean and continent would have caused an intensification of the prevailing winds. Then by pushing the surface water towards the west, these winds would have induced cooling of the coastal waters, changing the normal feature of the El Nio regime which is a warming of the waters. Between the end of the Little Ice Age and the beginning of the global warming attributable to human activities the ENSO regime was modified. Historical climatology studies founded on chroniclers accounts and descriptions of floods caused by these El Nio events also showed an abrupt change, around 1820, in the ENSO system along Pacific seaboard of South America. Since the beginning of the XIXth Century, in other words the final phase of the Little Ice Age, the characteristic feature of El Nio events was abnormal rainfall, both in central Chile during the southern winter and on the northern coast of Peru during the subsequent southern summer.

These results as a whole emphasize the complexity of the interactions at work between the global-scale climate changes, the diverse behaviour of the ENSO system and regional climate changes. It remains to be determined if the extreme intensity of the two events which occurred at the end of the XXth Century, in 1982-1983, then in 1997-1998, is effectively linked to recent intensification of global warming. If that turned out to be the case, the El Nio phenomenon could become more and more intense and destructive, not only on the South American coasts, but also in other regions of the world.


'/>"/>

Contact: Gregory Flechet
fichesactu@paris.ird.fr
33-014-803-7607
Institut de Recherche Pour le Dveloppement
Source:Eurekalert

Related biology news :

1. Global climate change: The impact of El Niño on Galápagos marine iguanas
2. North Americas northernmost lake affected by global warming
3. Global Warming and the Habitability of Planet Earth, Sept. 26
4. Green skies: Engineers work may reduce jet travels role in global warming
5. Scientists in first global study of poison gas in the atmosphere
6. IEEE-USA innovation forum will help prepare US tech leaders to prosper in a global marketplace
7. Majority of Americans want local action on global warming, says poll
8. International team of scientists warns of climate changes impact on global river flow
9. Changing the global dietary environment
10. Global deal fuels QUTs world-changing research
11. NIH hosts event to launch Council of Science Editors global theme issue
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:4/26/2016)... 2016 Research and Markets has ... Market 2016-2020"  report to their offering.  , ,     ... The analysts forecast the global multimodal biometrics market ... the period 2016-2020.  Multimodal biometrics is ... as the healthcare, BFSI, transportation, automotive, and government ...
(Date:4/15/2016)... 2016  A new partnership announced today will ... decisions in a fraction of the time it ... high-value life insurance policies to consumers without requiring ... Force Diagnostics, rapid testing (A1C, Cotinine and HIV) ... pressure, weight, pulse, BMI, and activity data) available ...
(Date:4/14/2016)... AVIV, Israel , April 14, 2016 ... Behavioral Authentication and Malware Detection, today announced the appointment ... already assumed the new role. Goldwerger,s leadership ... BioCatch, on the heels of the deployment of its ... addition, BioCatch,s behavioral biometric technology, which discerns unique cognitive ...
Breaking Biology News(10 mins):
(Date:6/23/2016)... Prostate Cancer Foundation (PCF) is pleased to announce 24 new Young Investigator ... Members of the Class of 2016 were selected from a pool of 128 ... About the Class of 2016 PCF Young Investigators ... ... ...
(Date:6/23/2016)... ... June 23, 2016 , ... Supplyframe, the ... the Supplyframe Design Lab . Located in Pasadena, Calif., the Design Lab’s ... how hardware projects are designed, built and brought to market. , The Design ...
(Date:6/23/2016)... LOUISVILLE, Ky. , June 23, 2016 /PRNewswire/ ... from two Phase 1 clinical trials of its ... double-blind, placebo-controlled, single and multiple ascending dose studies ... and pharmacodynamics (PD) of subcutaneous injection in healthy ... APL-2 subcutaneously (SC) either as a single dose ...
(Date:6/23/2016)... On Wednesday, June 22, 2016, the NASDAQ Composite ... Jones Industrial Average edged 0.27% lower to finish at 17,780.83; ... has initiated coverage on the following equities: Infinity Pharmaceuticals Inc. ... NKTR ), Aralez Pharmaceuticals Inc. (NASDAQ: ARLZ ), ... more about these stocks by accessing their free trade alerts ...
Breaking Biology Technology: