Coherent isotope history of Andean ice cores over the last century

Hoffmann, G.; Ramírez, Edson; Taupin, Jean-Denis; Francou, Bernard; Ribstein, Pierre; Delmas, Robert J.; Dürr, Hans H.; Gallaire, Robert; Simões, Jefferson Cárdia; Schotterer, U.; Stiévenard, M.; Werner, Martin

doi:10.1029/2002gl014870

Cited by 135 publications

(138 citation statements)

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“…The observed influence of precipitation on the oxygen signal is in line with climate-model results (9,14), and with observations on the relationship between δ 18 O prec and (amount of) precipitation in the Amazon (10,14). Our results thus support the idea that glacier and other oxygen isotope records in the Andes or subtropical Brazil (33) should primarily be interpreted as a precipitation record (18,20,21), and are much less a proxy for temperature. The strong similarity between our record and those from Andean ice cores (Fig.…”

Section: Resultssupporting

confidence: 78%

“…Additional support for a dominant influence of the soil-water signal on δ 18 O tr comes from a comparison of the tree-ring record with δ 18 O from Andean glaciers (15,17), which have primarily been interpreted as indicators of δ 18 O in atmospheric water vapor from the Amazon basin (21). We find a relatively strong correlation with the Quelccaya and Huascarán ice core records (Quelccaya, 1963(Quelccaya, -1984, r = 0.77; Huascaran, 1963-1992, r = 0.68), and somewhat lower correlation with the Sajama ice core record , r = 0.44).…”

Section: Resultsmentioning

confidence: 99%

“…Observations of the isotopic composition of meteoric precipitation over South America show that isotopic composition is indeed closely associated with the amount of precipitation along the air parcel path (10), which suggests that oxygen isotopes in precipitation are predominantly a proxy for the large-scale atmospheric component of the basin-wide hydrological cycle (9,14). However, the interpretation of results from paleoclimatic studies of oxygen isotopes in ice cores (15)(16)(17), lake sediments (18), and speleothems (19,20) remains disputed, and proxies have been interpreted variously as indicators of temperature (17), basin-wide rainfall (18)(19)(20)(21), or a combination of both (22). Despite numerous oxygen paleorecords from the Andes, there are no such proxies from within the Amazon basin itself.…”

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confidence: 98%

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Oxygen isotopes in tree rings are a good proxy for Amazon precipitation and El Niño-Southern Oscillation variability

Brienen

Helle

Pons

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

175

145

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We present a unique proxy for the reconstruction of variation in precipitation over the Amazon: oxygen isotope ratios in annual rings in tropical cedar (Cedrela odorata). A century-long record from northern Bolivia shows that tree rings preserve the signal of oxygen isotopes in precipitation during the wet season, with weaker influences of temperature and vapor pressure. Tree ring δ 18 O correlates strongly with δ 18 O in precipitation from distant stations in the center and west of the basin, and with Andean ice core δ 18 O showing that the signal is coherent over large areas. The signal correlates most strongly with basin-wide precipitation and Amazon river discharge. We attribute the strength of this (negative) correlation mainly to the cumulative rainout processes of oxygen isotopes (Rayleigh distillation) in air parcels during westward transport across the basin. We further find a clear signature of the El Niño-Southern Oscillation (ENSO) in the record, with strong ENSO influences over recent decades, but weaker influence from 1925 to 1975 indicating decadal scale variation in the controls on the hydrological cycle. The record exhibits a significant increase in δ 18 O over the 20th century consistent with increases in Andean δ 18 O ice core and lake records, which we tentatively attribute to increased water vapor transport into the basin. Taking these data together, our record reveals a fresh path to diagnose and improve our understanding of variation and trends of the hydrological cycle of the world's largest river catchment.climate change | dendrochronology | plant physiology T he Amazon basin is a major center of atmospheric convection and precipitation (1), and at the same time the world's largest drainage basin. The Amazon's river discharge accounts for ∼17% of the annual global discharge to the oceans (2); its hydrological cycle is tightly linked with the carbon cycle of the Amazon rainforest (3), which itself is one of the largest terrestrial biomass carbon pools. Changes in the hydrological cycle of the Amazon may therefore significantly affect atmospheric dynamics and global climate by changing atmospheric CO 2 concentration. Two particularly severe droughts occurred within the last decade (4), and long-term river records of the Amazon show a steady increase in discharge over the last century (5), indicating that the system may start to undergo some changes. It has been suggested that these changes are a result of anthropogenic warming, but they may also be part of longer-term, natural climatic variability. To clarify such a globally important issue, long-term, accurate records of the hydrological cycle of the Amazon basin are needed. However, meteorological data are only reliable for the last 50-60 y (6), and annually resolved long-term proxies for the hydrological cycle from within the Amazon basin itself are very scarce (7).A commonly used diagnostic for strength and functioning of the water cycle is the isotopic composition of precipitation. Although variation of oxygen isotope ratios in precip...

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Section: Resultssupporting

confidence: 78%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 98%

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Oxygen isotopes in tree rings are a good proxy for Amazon precipitation and El Niño-Southern Oscillation variability

Brienen

Helle

Pons

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

175

145

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“…), the great difference between these past Atlantic SSTs and modern Atlantic SSTs must have forced a very large increase (decrease) in southern (northern) tropical South American precipitation, relative to modern, during the North Atlantic cold events. Large precipitation increases in the southern tropics of South America synchronous with cold events in high northern latitudes have been observed at multi-decadal to millennial time scales in lake and ice-core paleoclimate records from the Altiplano of Peru and Bolivia (Baker et al 2001a,b, 2005, Hoffmann et al 2003, speleothem records from the exit region of the South American summer monsoon (Cruz et al 2005, Wang et al 2006 and from the Nordeste (Wang et al 2004), and paleoceanographic records of discharge offshore of the Nordeste (Arz et al 1998, Jennerjahn et al 2002. Precipitation decreases during North Atlantic cold events have been observed in northern tropical South America in the records from the Cariaco Basin (Black et al 1999, Haug et al 2001, Peterson et al 2000, Peterson and Haug 2006.…”

Section: Introductionmentioning

confidence: 99%

The Nature and Origin of Decadal to Millennial Scale Climate Variability in the Southern Tropics of South America: The Holocene Record of Lago Umayo, Peru

Baker

Fritz

Burns

et al. 2009

Developments in Paleoenvironmental Research

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This paper serves two purposes: to review current ideas about the nature and forcing of decadal to millennial scale precipitation variation in the southern tropics of South America during the late Quaternary and to present a new methodology for the reconstruction of precipitation as applied to a Holocene stable isotopic record of carbonate sediments in a tropical Andean lake, Lago Umayo, Peru. The basic thesis of the first part of the paper is that, although modern instrumental records suffice for deducing climate variability at decadal and shorter time scales, these records cannot adequately characterize the nature and forcing of lower-frequency climate variation. Understanding the nature of multi-decadal to millennial-scale climate variation and the mechanisms of large abrupt climate change is best derived from paleoclimatic time series. Tropical Atlantic sea-surface temperature variation is a significant control on tropical South American paleoclimate at these longer time scales. In the second part of the paper, an original method is presented for quantitatively reconstructing precipitation. This method utilizes the well-known relationship between the stable isotopic composition of precipitation and the amount of precipitation, a relationship that is highly significant in many tropical locales. Due to many simplifying assumptions, the reconstruction should be considered to be tentative.A ~12% increase in precipitation (~570 to 650 mm a -1 ) at 4750 cal year BP is consistent with the 6% increase in summer insolation at this latitude over the same period. However, the increase in precipitation was neither unidirectional nor gradual. Instead, every 240 years on average, precipitation increased or decreased by at least ~8% for periods lasting on average 100 years. The largest of these events had ~15% positive or negative departures from the long-term mean precipitation. These southern tropical wet events apparently coincided with periods of low sea-surface temperatures in the high-latitude North Atlantic, supporting a hypothesis of a tropical North Atlantic b a k e r e t a l . i n p a s t c l i m a t e v a r i a b i l i t y i n s o u t h a m e r i c a (2009) 302sea-surface temperature control on tropical South American precipitation at decadal to millennial scales.

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“…This cancelling then leads to a clearer relation of S18~,,,.ec to local climate parameters. For example, the decadal signal-to-noise ratio of Andean isotope records was shown to be extremely favourable, and the resulting mean Andean isotope signal was demonstrated to be controlled by large-scale displacements of the Hadley-Walker circulation, probably triggered by ENS0 variability in the Central Pacific (Bradley et al, 2003;Hoffmann, 2003;Hoffmann et a l , 2003).…”

Section: Discussionmentioning

confidence: 99%