L. Ortlieb, A. Sifeddine, D. Gutiérrez, G. Vargas, P. Tapia, D. Field, R. Salvatteci, J. Valdés, F. Velazco

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Climate variability in the SE tropical Pacific during the last few centuries: combining documentary historical evidence from Chile and Peru with high-resolution sedimentary records of the continental

1 Climate variability in the SE tropical Pacific during the last few centuries: combining documentary historical evidence from Chile and Peru with high-resolution sedimentary records of the continental margin L. Ortlieb, A. Sifeddine, D. Gutiérrez, G. Vargas, P. Tapia, D. Field, R. Salvatteci, J. Valdés, F. Velazco LOCEAN, Centre IRD Ile de France, Bondy, France Instituto del Mar del Peru, Callao, Peru Dept. Geología, Univ. de Chile, Santiago,Chile Fac. Recursos del Mar, Univ. de Antofagasta, Chili PSI XI Congress, Papeete, March 2009

2 The earliest sequence of El Niño reconstructed events for the last 5 centuries was based on documentary data from Peru (Quinn et al., 1987)

3 A later sequence proposed by Quinn & Neal (1992) and Quinn (1993) included more data from Brazil, Bolivia and Chile Significant changes with respect to the 1987 series, and additionnal events, with refined evaluated intensity

4 These El Niño sequences were critically revised, with a focus on documentary data from Peru (up to 1900 AD) (Ortlieb, 2000) Occurrence and intensity of the reconstructed EN events: Confirmed Possible Doubtful Infirmed

5 The numerous discrepancies with Quinn s El Niño reconstructions have several causes: Misinterpretation of documentary reports; Exaggeration in the significance of some informations; Lack of systematic analysis of the source reliability; Confidence rating essentially based upon the number of published sources (even when not independent); Forced correlation between climate anomalies from widely separated areas, at the continental scale; No consideration for data/interpretation inconsistencies; Additional documentary information made available; Recent reappraisal of the significance of EN/LN impacts in different regions, within Peru.

-1 0 1 2 1535 1545 1555 1565 1575 1585 1595 1605 1615 1625 1635 1645 1655 1665 1675 1685 1695 1705 1715 1725 1735 1745 1755 1765 1775 1785 1795 1805 1815 1825 1835 1845 1855 1865 1875 1885 1895 1905

6 All S- America (Quinn, 1993) Peru-S Ecuador (Ortlieb 2000 modified) Major discrepancies in the XVI- XVIII th centuries

7 Do the few well-assessed El Niño events reconstructed during the 16 th, 17 th and 18 th centuries in Peru/Ecuador reveal a different El Niño regime than in the subsequent two centuries? Or Does this situation only reflect the intrinsic limitations of the historical documentary approach for the reconstruction of climatic anomalies? Before an examination of other data sets, let s have a look to another documentary record of El Niño manifestations

8 Modern ENSO teleconnection patterns in the Southern Pacific largely control the precipitation regime in central Chile Curtis & Adler 2002 Rutllant, 2003

9 In Santiago and Valparaiso, instrumental records show that winter rainfall anomalies are closely linked to both EN and LN conditions 900 Santiago rainfall year El Niño «Normal» year La Niña Ortlieb 2002 quite favorable relationship for EN/LN reconstruction mm of precipitation

Abundant colonial documentary data from the capital of the «Reyno de Chile» was thus analyzed for ENSO reconstruction In Santiago, the «Cal y Canto» bridge built after

10 Abundant colonial documentary data from the capital of the «Reyno de Chile» was thus analyzed for ENSO reconstruction In Santiago, the «Cal y Canto» bridge built after several Mapocho River major floods (1683, 1764), suffered from other subsequent floods also related to El Niño occurrences, and was finally destroyed during the 1888 strong EN event.

11 A specific study on reconstruction of former EN and LN events was thus conducted in central Chile (Ortlieb, unpublished) 1877 Actas del Cabildo de Santiago ( ) Gay, 1846 Vicuña Mackenna, 1877

12 A new sequence of El Niño and La Niña events based on Chilean historical data, All S- America (Quinn, 1993) Peru-S Ecuador (Ortlieb 2000 modified) Chilean data: El Niño events & La Niña events

13 South America (Quinn, 1993) Peru & S Ecuador Central Chile Like for the Peruvian EN series, the Chilean sequence leads to identify less El Niño events prior to the XIX th century than afterwards

14 South America (Quinn, 1993) Peru & S Ecuador Central Chile 1817 This comparison also shows that it is only since 1817, that EN manifestations occur the same year in central Chile and in northern Peru

15 Examples of these «mismatches», prior to 1817 None of the very strong EN years defined either in N Peru or in Chile presented concordant evidence in the other country In only four instances, EN manifestations of different intensities, were recorded in both countries: 1574, 1686, 1746 and 1748 In some cases, dry years (interpreted as LN events) in central Chile correspond to wet years in Northern Peru (thus defined there as EN years): 1638, 1814 In multiple other cases, there is evidence for «normal conditions» in one country when EN manifestations are reported in the other one.

16 This situation suggests: A large-scale reorganisation of the atmospheric circulation pattern in Southern America coincident with, and probably related to, the end of the Little Ice Age conditions A major change in the ENSO teleconnection system along the eastern Pacific coast at the beginning of the 19 th century Besides, the confrontation of the historical records from Peru and Chile tends to validate the documentary approach, and hence to confirm that the frequency of EN events was actually lower in the three centuries before the XIX th century

17 o Year o grey level Sedimentary characteristics Primary Productivity 0 0 Diatom flux TOC Secondary Productivity Bones & vertebrae DBD Independent evidence from laminated sediments of the central Peruvian margin (and in a N Chile bay) supports the interpretation of a major reorganisation of the oceanclimate system around 1820 in the eastern Pacific 11.5 S 77.5 W 77.0 W 76.5 W 76.0 W 75.5 W Chancay Ancón S B13 Callao Chorrillos 12.0 S S Pucusana 12.5 S Year S Asia Cerro Azul Cañete 13.0 S S Tambo de Mora 13.5 S DBD (Gutiérrez, in press) (C g yr) # all fish scales Callao 184 m Pisco 299m 14.0 S 14.5 S Pisco Peninsula de Paracas 14.0 S B6 Bahia Independencia Morro Quemado 77.5 W 77.0 W 76.5 W 76.0 W 75.5 W 14.5 S

18 The high-resolution studies of the marine sedimentary cores, involving sedimentological, geochemical, phytoplanktonic, foraminiferal, and fish remain data, document a major environmental change at ~1820 AD. This sudden regime shift is explained by a regional-scale alteration of the biogeochemical environment of the SE Pacific, itself linked to : - a regional hydrological change onshore - and a northward latitudinal shift of the intertropical convergence zone. This ~1820 AD regional reorganization of the atmospheric circulation patterns would also account for the ENSO regime shift at the end of the Little Ice Age.

Other indicators to be considered for the reconstruction of El Niño events: Coral geochemical data Palmyra Island 1630-1700 Cobb et al.

19 Other indicators to be considered for the reconstruction of El Niño events: Coral geochemical data Palmyra Island Cobb et al., 2002 Corrège et al., 2001 δ 18 O variations in coral sequences from central and western Pacific also suggest a lower frequency of El Niño events prior to the XIX th century

The combination of documentary information,

20 The combination of documentary information, sedimentary analysis of laminated sediments, and geochemical data from coral cores, still have much to reveal about the characterization of ENSO regimes through time Coral head Laminated marine sediments from Peruvian hypoxic environment

21 Merci, Thank you

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