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Southward Migration of the Intertropical Convergence Zone Through the Holocene.

Cariaco Basin metal concentrations (Fe, Ti)

Fig. 2.
Cariaco Basin metal concentrations (Fe, Ti) versus core depth (m) in ODP Site 1002 (data smoothed by a 3-point running mean). Arrows indicate the position of AMS 14C dates converted to calendar years before the present (BP). Inset: Depth-age plot showing sedimentation rates over the time period of this study.

Southward Migration of the Intertropical Convergence Zone Through the Holocene.
Vol 293, Issue 5533, 1304-1308 , 17 August 2001

Gerald H. Haug1, Konrad A. Hughen,2 Daniel M. Sigman,3 Larry C. Peterson,4 Ursula Röhl5

1 Department of Earth Sciences, Eidgenössische Technische Hochschule-Zentrum, CH-8092 Zürich, Switzerland.
2 Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
3 Department of Geosciences, Princeton University, Princeton, NJ 08544, USA. 4 Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149, USA. 5 Fachbereich Geowissenschaften, Universität Bremen, D-28334 Bremen, Germany.

Titanium and iron concentration data from the anoxic Cariaco Basin, off the Venezuelan coast, can be used to infer variations in the hydrological cycle over northern South America during the past 14,000 years with subdecadal resolution. Following a dry Younger Dryas, a period of increased precipitation and riverine discharge occurred during the Holocene "thermal maximum." Since ~5400 years ago, a trend toward drier conditions is evident from the data, with high-amplitude fluctuations and precipitation minima during the time interval 3800 to 2800 years ago and during the "Little Ice Age." These regional changes in precipitation are best explained by shifts in the mean latitude of the Atlantic Intertropical Convergence Zone (ITCZ), potentially driven by Pacific-based climate variability. The Cariaco Basin record exhibits strong correlations with climate records from distant regions, including the high-latitude Northern Hemisphere, providing evidence for global teleconnections among regional climates.
To read or view the full study, please visit the Science website.

Download the Data from the WDC Paleo Archive.

Fig. 3.
Bulk Ti content of Cariaco Basin sediments from ODP Site 1002 versus age, spanning (a) the last 14 ky (3-point running mean); (b) the last 5 ky (3-point running mean); and (c) the last 1.2 ky (raw data and 3-point running mean). Higher Ti content reflects greater terrigenous input from riverine runoff and is interpreted to indicate greater precipitation and a more northerly mean latitude of the ITCZ.

This high resolution record of titanium in a sediment core from the Cariaco Basin off the coast of Venezuela show the broad impact of the Younger Dryas and subsequent climate events. Titanium, which is a proxy for precipitation and land runoff, provides a record of the strong cooling and abrupt warming of the Younger Dryas (Figure 3a). Part b of the figure also reveals an increase in variability in the El Niño-Southern Oscillation system around 3,800 years ago, similar to results of Sandweiss et al. (1996) and Moy et al. (2002). Part c provides the finest temporal resolution and shows a generally warm period during the "Medieval Warm Period" and the stronger cooling during the Little Ice Age.

References cited:
Moy, C.M., G.O. Seltzer, D.T. Rodbell, and D.M. Anderson. 2002.
Variability of El Niño/Southern Oscillation activity at millennial timescales during the Holocene epoch.
Nature, 420, 162-165. Click for data from the WDC Paleo archive.

Sandweiss, D.H., J.B. Richardson III, E.J. Reitz, H.B. Rollins, and K.A. Maasch. 1996.
Geoarchaeological Evidence from Peru for a 5000 Years B.P. Onset of El Niño.
Science. 273: 1531-1533.

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10 May 2004