Postglacial changes in El Niño and La Niña behavior

Makou, Matthew; Eglinton, T. I.; Oppo, Delia W; Hughen, Konrad A

doi:10.1130/g30366.1

Cited by 65 publications

(68 citation statements)

References 26 publications

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“…5b-d; Graham et al, 2007Graham et al, , 2010Trouet et al, 2009;Makou et al, 2010;Pages-News, 2011;Cobb et al, 2003;Richter et al, 2009;Norgaard-Pedersen and Mikkelsen, 2009;Jenny et al, 2002). This would explain in part why we observe such a large positive hydroclimatic anomaly in the southernmost PdT basin during a large fraction of the MCA.…”

Section: What Has Driven the Long-term Hydrological And Ecological Dymentioning

confidence: 72%

Hydroclimate variability in the low-elevation Atacama Desert over the last 2500 yr

et al. 2012

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Abstract. Paleoclimate reconstructions reveal that Earth system has experienced sub-millennial scale climate changes over the past two millennia in response to internal/external forcing. Although sub-millennial hydroclimate fluctuations have been detected in the central Andes during this interval, the timing, magnitude, extent and direction of change of these events remain poorly defined. Here, we present a reconstruction of hydroclimate variations on the Pacific slope of the central Andes based on exceptionally wellpreserved plant macrofossils and associated archaeological remains from a hyperarid drainage (Quebrada Maní, ∼21 • S, 1000 m a.s.l.) in the Atacama Desert. During the late Holocene, riparian ecosystems and farming social groups flourished in the hyperarid Atacama core as surface water availability increased throughout this presently sterile landscape. Twenty-six radiocarbon dates indicate that these events occurred between 1050-680, 1615-1350 and 2500-2040 cal yr BP. Regional comparisons with rodent middens and other records suggest that these events were synchronous with pluvial stages detected at higher-elevations in the central Andes over the last 2500 yr. These hydroclimate changes also coincide with periods of pronounced SST gradients in the Tropical Pacific (La Niña-like mode), conditions that are conducive to significantly increased rainfall in the central Andean highlands and flood events in the low-elevation watersheds at inter-annual timescales. Our findings indicate that the positive anomalies in the hyperarid Atacama over the past 2500 yr represent a regional response of the central Andean climate system to changes in the global hydrological cycle at centennial timescales. Furthermore, our results provide support for the role of tropical Pacific sea surface temperature gradient changes as the primary mechanism responsible for climate fluctuations in the central Andes. Finally, our results constitute independent evidence for comprehending the major trends in cultural evolution of prehistoric peoples that inhabited the region.

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Section: What Has Driven the Long-term Hydrological And Ecological Dymentioning

confidence: 72%

Hydroclimate variability in the low-elevation Atacama Desert over the last 2500 yr

et al. 2012

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“…Sedimentary sterol concentrations in marine sediment off the Peru coast (Makou et al, 2010) suggest the MCA coincides with a reduction in El Niño activity, with both El Niño and La Niña activity increasing from the late MCA onwards. Based on a range of North American proxies, Graham et al (2007) conclude that the MCA was characterised by arid conditions in western North America consistent with a La Niña-like state, followed by a wetter LIA.…”

Section: Discussionmentioning

confidence: 99%

Was the Little Ice Age more or less El Niño-like than the Medieval Climate Anomaly? Evidence from hydrological and temperature proxy data

2017

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Abstract. The El Niño-Southern Oscillation (ENSO) is the most important source of global climate variability on interannual timescales and has substantial environmental and socio-economic consequences. However, it is unclear how it interacts with large-scale climate states over longer (decadal to centennial) timescales. The instrumental ENSO record is too short for analysing long-term trends and variability and climate models are unable to accurately simulate past ENSO states. Proxy data are used to extend the record, but different proxy sources have produced dissimilar reconstructions of long-term ENSO-like climate change, with some evidence for a temperature-precipitation divergence in ENSO-like climate over the past millennium, in particular during the Medieval Climate Anomaly (MCA; AD ∼ 800-1300) and the Little Ice Age (LIA; AD ∼ 1400-1850). This throws into question the stability of the modern ENSO system and its links to the global climate, which has implications for future projections. Here we use a new statistical approach using weighting based on empirical orthogonal function (EOF) to create two new large-scale reconstructions of ENSOlike climate change derived independently from precipitation proxies and temperature proxies. The method is developed and validated using model-derived pseudo-proxy experiments that address the effects of proxy dating error, resolution, and noise to improve uncertainty estimations. We find no evidence that temperature and precipitation disagree over the ENSO-like state over the past millennium, but neither do they agree strongly. There is no statistically significant difference between the MCA and the LIA in either reconstruction. However, the temperature reconstruction suffers from a lack of high-quality proxy records located in ENSO-sensitive regions, which limits its ability to capture the large-scale ENSO signal. Further expansion of the palaeo-database and improvements to instrumental, satellite, and model representations of ENSO are needed to fully resolve the discrepancies found among proxy records and establish the long-term stability of this important mode of climatic variability.

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“…S1) at 9.6 ka 16 and increased influence of glacial melt and precipitation in Maxwell Bay 13 . This warmth was concomitant with the last influence of orbitally-forced deglaciation 5,15 and ENSO-sensitive proxy records from the Peru margin and Ecuador 5,17 that indicate a persistent warm, mean La Niña-like state (relative to mean El Niño-like conditions).…”

mentioning

confidence: 90%

“…1a). This increase reflects continued atmospheric warming when the ENSO pattern was strong and La Niña was enhanced, especially relative to El Niño during the period between 2.0-1.0 ka 5 . A late Holocene link between La Niña and WAP SST via oceanic forcing has been suggested beginning 1.7 ka 3 , however, this is based on comparisons with a proxy ENSO record that is insensitive to variations in the strength of La Niña 20 and the reconstructed high SSTs from 1.7 ka are inconsistent with diatom assemblage and concentration data that show evidence for extensive sea ice, cooler SSTs and reduced spring sea icemelt water stratification at this time 4 (Fig.…”

mentioning

confidence: 94%

“…We interpret this decrease as increasing glacial ice discharge rather than frontal melting because the persistent presence of warm UCDW in Palmer Deep ended at c. 3.6 ka 18 and diatom concentration and assemblage data indicate cooler SSTs and less spring sea ice melt-induced stratification after this time 4,22 . Increased glacial ice discharge was driven by atmospheric warming of the WAP and increased moisture delivery as a result of two forcing mechanisms; maximum Holocene ENSO frequency from c. 2.2 ka 5,17,20 (Fig. 1c-e) and increased La Niña intensity 23 (Fig.…”

mentioning

confidence: 99%

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