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Author(s): Gergana Yancheva [1]; Norbert R. Nowaczyk [1]; Jens Mingram [1]; Peter Dulski [1]; Georg Schettler [1]; Jörg F. W. Negendank [1]; Jiaqi Liu [2]; Daniel M. Sigman [3]; Larry [...]

With their magnificent architecture and sophisticated knowledge of astronomy and mathematics, the Maya boasted one of the great cultures of the ancient world. Although they had not discovered the wheel [...]

A high-resolution western tropical Atlantic sea surface temperature (SST) record from the Cariaco Basin on the northern Venezuelan shelf, based on Mg/Ca values in surface-dwelling planktonic foraminifera, reveals that changes in SST over the last glacial termination are synchronous, within ± 30 to ± 90 years, with the Greenland Ice Sheet Project 2 air temperature proxy record and atmospheric methane record. The most prominent deglacial event in the Cariaco record occurred during the Younger Dryas time interval, when SSTs dropped by 3° to 4°C. A rapid southward shift in the atmospheric intertropical convergence zone could account for the synchroneity of tropical temperature, atmospheric methane, and high-latitude changes during the Younger Dryas., The Cariaco Basin, on the northern Venezuelan shelf, is a unique repository of tropical paleoclimate records (11-17). The combination of shallow sills ( 1 mm/year) has produced nearly continuous, annually [...]

In the anoxic Cariaco Basin of the southern Caribbean, the bulk titanium content of undisturbed sediment reflects variations in riverine input and the hydrological cycle over northern tropical South America. A seasonally resolved record of titanium shows that the collapse of Maya civilization in the Terminal Classic Period occurred during an extended regional dry period, punctuated by more intense multiyear droughts centered at approximately 810, 860, and 910 A.D. These new data suggest that a century-scale decline in rainfall put a general strain on resources in the region, which was then exacerbated by abrupt drought events, contributing to the social stresses that led to the Maya demise., Paleoclimatologists have developed an increasingly precise record of climate change for the past few millennia, coveting the same span of time over which literate human societies developed. Until recently, archaeologists [...]

Radiocarbon-based age-estimates of biogenic material sometimes do not agreed with true calendar age, particularly beyond the limits of radiocarbon calibration based on tree-ring data. Radiocarbon data from Cariaco basin varved sediments were used to give an accurate and continuous radiocarbon calibration for the 9-14.5 Kyr BP period. It is suggested that North Atlantic Deep Water formation stopped during the Younger Dryas period, but was replaced by alternative convection modes.

The changes in the topography of the Cariaco basin were determined through the relative reflectivity (grey scale) from the four cores of the new surfaces at the center of the basin. Records showed cores changes that mirrored surface variations, indicating that grey scale is also controlled by the yearly extent of biogenetic productivity. Records also showed that major parts of the high-latitude North Atlantic region had the same climatic variations during the last deglaciation. These variations also tied up with the changes found in the Cariaco Basin.

Arising from: G. Yancheva et al. Nature 445, 74-77 (2007) On the basis of the anti-correlation of their palaeoclimatic proxy for the strength of the East Asian winter monsoon from [...]

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., The Cariaco Basin, an anoxic marine basin on the northern shelf of Venezuela, is a highly sensitive recorder of past climates in the tropical ocean (1-4), in part because its [...]

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., Large millennial-scale air temperature oscillations first observed in the oxygen isotopic composition (Δ[sup.18]O) of Greenland ice reflect massive reorganizations of the atmosphere-ocean system during the last glacial period (1). A [...]

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., Large millennial-scale air temperature oscillations first observed in the oxygen isotopic composition (Δ[sup.18]O) of Greenland ice reflect massive reorganizations of the atmosphere-ocean system during the last glacial period (1). A [...]

Climate in the tropical North Atlantic is controlled largely by variations in the strength of the trade winds, the position of the Intertropical Convergence Zone, and sea surface temperatures. A high-resolution study of Caribbean sediments provides a subdecadally resolved record of tropical upwelling and trade wind variability spanning the past 825 years. These results confirm the importance of a decadal (12- to 13-year) mode of Atlantic variability believed to be driven by coupled tropical ocean-atmosphere dynamics. Although a well-defined interdecadal mode of variability does not appear to be characteristic of the tropical Atlantic, there is evidence that century-scale variability is substantial The tropical Atlantic may also have been involved in a major shift in Northern Hemisphere climate variability that took place about 700 years ago., Although short-term variability in Atlantic climate is thought to be relatively well understood (1), both the patterns and the mechanisms of variability on decadal to century scales are as yet [...]

Arising from: G. Yancheva et al. Nature 455, 74-77 (2007). The Asian summer monsoon has been precisely reconstructed from the high-resolution record from the speleothem1, but reconstruction of the Asian [...]

THIN ICE: Unlocking the Secrets of Climate in the World's Highest Mountains. Mark Bowen. xiv + 463 pp. Henry Holt and Company, 2005. $30. In the summer of 1997, a [...]

Author(s): Gergana Yancheva [1]; Norbert R. Nowaczyk [1]; Jens Mingram [1]; Peter Dulski [1]; Georg Schettler [1]; Jörg F. W. Negendank [1]; Jiaqi Liu [2]; Daniel M. Sigman [3]; Larry [...]

Author(s): Gergana Yancheva [1]; Norbert R. Nowaczyk [1]; Jens Mingram [1]; Peter Dulski [1]; Georg Schettler [1]; Jörg F. W. Negendank [1]; Jiaqi Liu [2]; Daniel M. Sigman [3]; Larry [...]

Author(s): Gerald H. Haug [1]; Larry C. Peterson [2] Much of what we have learned about the dynamics of Earth's climate system has come from the study of ancient climates. [...]