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Rapid changes in the hydrologic cycle of the tropical Atlantic during the last glacial.

Cariaco Basin Climate Records Rapid changes in the hydrologic cycle of the tropical Atlantic during the last glacial.
Science Vol. 290, issue 4598, pp. 1947-1951, 8 December 2000

Larry C. Peterson,1 Gerald H. Haug,2 Konrad A. Hughen,3 Ursula Röhl4
1 Rosenstiel School of Marine & Atmospheric Science, Univ. of Miami, Miami, FL 33149, USA.
2 Dept. of Earth Sciences, Swiss Federal Institute of Technology,CH-8092 Zürich, Switzerland.
3 Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
4 Fachbereich Geowissenschaften, Universität Bremen, D-28334 Bremen, Germany.

Figure 1. Comparison of measured color reflectance (550 nm) (five-point moving average) of Cariaco Basin sediments from ODP Hole 1002C to d18O from the GISP II ice core. MIS boundaries in Hole 1002C are from Peterson, et al., Proc. Ocean Drill. Program Sci. Results 165, 85 (2000), and detailed age control over the upper 22m is based on AMS 14C dating of the planktic foraminifer G. bulloides. Additional visual tie points between the color reflectance and GISP d18O records are shown. The distribution of laminated intervals is indicated across the top. The presence of a semi-indurated dolomite layer in Hole 1002C at 28.3m below the sea floor resulted in minor core disturbance at this level. Deposition of dark, generally laminated sediments preferentially occurs during warm interglacial or interstadial times (numbered events), whereas deposition of light-colored bioturbated sediments was restricted to colder stadial intervals of the last glacial. Sediment color variations in the Cariaco Basin are driven by changing surface productivity, with increased organic rain leading to darker sediments and, through remineralization reactions, periods of anoxic or near-anoxic conditions in the deep basin. SMOW, standard mean ocean water.

ABSTRACT:
Sedimentary time series of color reflectance and major element chemistry from the anoxic Cariaco Basin off the coast of northern Venezuela record large and abrupt shifts in the hydrologic cycle of the tropical Atlantic during the past 90,000 years. Marine productivity maxima and increased precipitation and riverine discharge from northern South America are closely linked to interstadial (warm) climate events of marine isotope stage 3, as recorded in Greenland ice cores. Increased precipitation at this latitude during interstadials suggests the potential for greater moisture export from the Atlantic to Pacific, which could have affected the salinity balance of the Atlantic and increased thermohaline heat transport to high northern latitudes. This supports the notion that tropical feedbacks played an important role in modulating global climate during the last glacial period.
To read or view the full study, please visit the Science website.

DATA:
Download the Data from the WDC Paleo Archive.

DISCUSSION:
The color reflectance record from this core in the Cariaco Basin shows the broad geographic impact of the abrupt climate changes during the last glacial period. This record reveals climatic impacts in China synchronous with the interstadial (Dansgaard/Oeschger) events seen in ice cores from Greenland (Figure 1).

The Greenland Ice Sheet Project Two (GISP2) core data is also available on the WDC Paleo website.

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10 May 2004