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Urmia Lake in NW Iran was the world’s second largest hypersaline lake until three decades ago, when it began to lose ~ 90% of its surface area due to dwindling water input and enhanced evaporation. To help discern the role of natural vs anthropogenic factors in the rapid demise of Urmia Lake, we present a high-resolution, multi-proxy reconstruction of climate, and hydrological variability from the lake’s sediments. We identify several episodes of wet and dry conditions over the past 11,300 years, and an atmospheric teleconnection between the climate of the interior of West Asia and the North Atlantic region. Estimates of mean annual precipitation based on chemical weathering indices range between 174 and 401 mm year−1 during the Holocene. A combination of geochemical proxies, pollen reconstruction, and the absence of any evaporite horizons throughout the Holocene period point to the prevailing role of human impact on the current vanishing of Urmia Lake. [ABSTRACT FROM AUTHOR]

During the last glacial period, the North Atlantic regionexperienced pronounced, millennial-scale alternations between cold, stadial conditions and milder interstadial conditions-commonly referred to as Dansgaard-Oeschger oscillations-as well as periods of massive iceberg discharge known as Heinrich events. Changes in Northern Hemisphere temperature, as recorded in Greenland, are thought to have affected the location of the Atlantic intertropical convergence zone and the strength of the Indian summer monsoon. Here we use high-resolution records of sediment colour-a measure of terrigenous versus biogenic content-from the Cariaco Basin off the coast of Venezuela and the Arabian Sea to assess teleconnections with the North Atlantic climate system during the last glacial period. The Cariaco record indicates that the intertropical convergence zone migrated seasonally over the site during mild stadial conditions, but was permanently displaced south of the basin during peak stadials and Heinrich events. In the Arabian Sea, we find evidence of a weak Indian summer monsoon during the stadial events. The tropical records show a more variable response to North Atlantic cooling than the Greenland temperature records. We therefore suggest that Greenland climate is especially sensitive to variations in the North Atlantic system-in particular sea-ice extent-whereas the intertropical convergence zone and Indian monsoon system respond primarily to variations in mean Northern Hemisphere temperature. [ABSTRACT FROM AUTHOR]

Tonle Sap Lake, Cambodia, possesses one of the most productive inland fisheries in the world and is a vital natural resource for the country. The lake is connected to the Mekong River via the Tonle Sap River. Flow in the Tonle Sap River reverses seasonally, with water exiting the lake in the dry season and entering the lake during the summer monsoon. This flood pulse drives the lake's biological productivity. We used Sr, Nd, and Pb isotopes and elemental concentrations in lake sediment cores to track changes in the provenance of deposits in Tonle Sap Lake. We sought to determine when the lake first began to receive water and sediment input via the Mekong River, which initiated flood pulse processes. The transition from a non-pulsing lake to the Mekong-connected system is marked by shifts to values of Sr/Sr, ε, and Pb/Pb that are characteristic of Mekong River sediments. In addition, magnetic susceptibility increased and sediment elemental composition changed. Elemental (P) measures point to enhanced phosphorus loading and C/N and isotope ratios of bulk organic matter indicate a shift to greater relative contribution of organic material from aquatic versus terrestrial environments, coinciding with the initiation of flood pulse processes. On the basis of radiocarbon dating in two cores, we estimate the initiation of the annual flood pulse occurred between ~4,450 and 3,910 cal year BP. [ABSTRACT FROM AUTHOR]

The Asian–Australian monsoon is an important component of the Earth’s climate system that influences the societal and economic activity of roughly half the world’s population. The past strength of the rain-bearing East Asian summer monsoon can be reconstructed with archives such as cave deposits, but the winter monsoon has no such signature in the hydrological cycle and has thus proved difficult to reconstruct. Here we present high-resolution records of the magnetic properties and the titanium content of the sediments of Lake Huguang Maar in coastal southeast China over the past 16,000 years, which we use as proxies for the strength of the winter monsoon winds. We find evidence for stronger winter monsoon winds before the Bølling–Allerød warming, during the Younger Dryas episode and during the middle and late Holocene, when cave stalagmites suggest weaker summer monsoons. We conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone. Similar migrations of the intertropical convergence zone have been observed in Central America for the period ad 700 to 900 (refs 4–6), suggesting global climatic changes at that time. From the coincidence in timing, we suggest that these migrations in the tropical rain belt could have contributed to the declines of both the Tang dynasty in China and the Classic Maya in Central America. [ABSTRACT FROM AUTHOR]

Presents research which used radiocarbon data from varved sediments in the Cariaco basin, southern Caribbean Sea, to construct a radiocarbon calibration for the period nine to 14.5 kyr BP. Temporal variations in atmospheric concentration of radiocarbon; Radiocarbon dating through tree-ring data; Previous research; North Atlantic Deep Water formation during Younger Dryas period.

Replying to: De’er Zhang & Longhua Lu 450, doi:10.1038/nature06338 (2007)Zhang and Lu argue that Chinese historical climate records contradict certain of our interpretations based on Lake Huguang Maar sediment records. Interpreting these records as an indicator for winter monsoon winds and Chinese cave records as an indicator for summer monsoon rainfall, we observed an inverse relationship between winter and summer monsoons on a millennial timescale over the past 16,000 yr. In sediments deposited during the period of Classical Chinese dynastic history, we found evidence for a temporal coincidence between winter monsoon strengthening and the terminations of important dynasties. Extrapolating the inverse monsoon relationship to these multidecadal timescales, we suggested that reduced summer rainfall contributed to dynastic terminations, including that of the Tang (ad 618–907). Zhang and Lu challenge the validity of the summer/winter monsoon relationship on the grounds that historical records indicate that relatively cold winters tended to be associated with relatively wet summers over the period they considered. They argue that the Tang dynasty decline was associated with cold winters, in agreement with our findings, but they find no evidence for rainfall changes having contributed to the decline of the Tang. [ABSTRACT FROM AUTHOR]

The article focuses on the works and achievements of Nicholas Shackleton, a climatologist. He studied physics at Clare College in Cambridge, England and graduated in 1961. Shackleton developed a mass spectrometer that could analyze the oxygen isotope ratios in small numbers of foraminifera. He made a fundamental discovery that the dominant ice-volume cycle revealed by the oxygen isotopes lasted roughly 100,000 years. Shackleton died on January 24, 2006.