Search

The reliability of Arctic climate predictions is currently hampered by insufficient knowledge of natural climate variability in the past. A sediment core from Lake El'gygytgyn in northeastern (NE) Russia provides a continuous, high-resolution record from the Arctic, spanning the past 2.8 million years. This core reveals numerous "super interglacials" during the Quaternary; for marine benthic isotope stages (MIS) 11c and 31, maximum summer temperatures and annual precipitation values are -4° to 5°C and ~300 millimeters higher than those of MIS 1 and 5e. Climate simulations show that these extreme warm conditions are difficult to explain with greenhouse gas and astronomical forcing alone, implying the importance of amplifying feedbacks and far field influences. The timing of Arctic warming relative to West Antarctic Ice Sheet retreats implies strong interhemispheric climate connectivity. [ABSTRACT FROM AUTHOR]

Whether cooling occurred in the Southern Hemisphere during the Younger Dryas (YD) is key to understanding mechanisms of millennial climate change. Although Southern Hemisphere records do not reveal a distinct climate reversal during the late glacial period, many mountain glaciers readvanced. We show that the Puerto Bandera moraine (5005), which records a readvance of the Southern Patagonian Icefield (SPI), formed at, or shortly after, the end of the YD. The exposure age (10.8 ± 0.5 thousand years ago) is contemporaneous with the highest shoreline of Lago Cardiel (49°S), which records peak precipitation east of the Andes since 13 thousand years ago. Absent similar moraines west of the Andes, these data indicate an SPI response to increased amounts of easterly-sourced precipitation—reflecting changes in the Southern Westerly circulation—rather than regional cooling. [ABSTRACT FROM AUTHOR]

Laterally extensive black shales were deposited on the São Francisco craton in southeastern Brazil during low-latitude Neoproterozoic glaciation ∼740 to 700 million years ago. These rocks contain up to 3.0 weight % organic carbon, which we interpret as representing the preserved record of abundant marine primary productivity from glacial times. Extractable biomarkers reflect a complex and productive microbial ecosystem, including both phototrophic bacteria and eukaryotes, living in a stratified ocean with thin or absent sea ice, oxic surface waters, and euxinic conditions within the photic zone. Such an environment provides important constraints for parts of the "Snowball Earth" hypothesis. [ABSTRACT FROM AUTHOR]

The direct and secondary effects of rapidly changing climate caused large rivers draining the Atlantic passive margin to incise quickly into bedrock beginning about 35,000 years ago. Measured in samples from bedrock fluvial terraces, 10-beryllium shows that both the Susquehanna and Potomac Rivers incised 10- to 20-meter-deep gorges along steep, convex lower reaches during the last glacial cycle. This short-lived pulse of unusually rapid downcutting ended by 13,000 to 14,000 years ago. The timing and rate of downcutting are similar on the glaciated Susquehanna and unglaciated Potomac Rivers, indicating that regional changes, not simply glacial meltwater, initiated incision. [ABSTRACT FROM AUTHOR]

Presents a study which demonstrated that a marine sediment core from the Iberian margin was affected by cooling and advection of arctic water masses during some Heinrich events in the North Atlantic region as of August 2000. Implications of high-resolution paleoclimatic records to glacial climate; Influence of Heinrich events.

Discusses the ice record provided by the Guliya ice cap on the Qinghai-Tibetan Plateu. The information about the regional climatic conditions over the last glacial cycle; The development of a time scale for the interpretation of the paleoclimatic information; The evidence for old ice; Abrupt climate changes.

The article cites a report within the issue regarding climatology research by J. Schmitt and colleagues that provides carbon isotopic data that may help explain changes in atmospheric greenhouse gas carbon dioxide (CO2) beginning 24 thousands years ago. Topics include an explanation of changes in CO2 concentrations during ice age cycles, the challenges of obtaining consistent patterns in CO2 concentrations, such as a lack of detailed and precise ice core isotopic measurements, and how Schmitt and colleagues overcame these challenges to produce what is reportedly the best record thus far of the glacial to interglacial variations in stable carbon isotopes of CO2.

The article discusses the causes of glacial cycle in earth. It has been stated according to the Milankovitch theory that the changes of insolation is the cause of ice age cycle. Insolation is described as the exposure of the earth's surface to the rays of the sun. It varies on time scales of thousands of years as a result of regular changes in earth's orbit around the sun, in the tilt of earth's axis, and in the direction of earths axis of rotation. An example has been cited that between 3 and 1 million years before present, glacial oscillations follows a 41,000-year cycle and that these oscillations correspond to insolation changes driven by obliquity changes. Other information related to the topic are discoursed in the paper.

Provides information on the Younger Dryas (YD) period. Hypotheses on the effect of YD; How to identify oceanic and atmospheric teleconnections that linked regional climates during glacial-interglacial cycles; Climate indicators from both South and North America that reveal climatic reversals of glacial-interglacial transition.

The article discusses research by paleoclimate modeler Ayako Abe-Ouchi of the University of Tokyo and colleagues in a 2013 issue of "Nature" magazine that linked a type of global climate model used to forecast global warming with a complex model of the northern ice sheets to study how slight changes in Earth's orbit could have driven the great ice ages. The team's discovery of two processes that they believe are key to a realistic glacial cycle are discussed.

The article focuses on the deglaciation during Pleistocene epoch. A compiled evidence suggests that the sea levels would fluctuate by 30 to 40 meters during the start of warm intervals. This occurrence will confirm the variability of relative elevations of deposits in Greek shoreline. Information to determine the sample ages using U/Th dating found out that the sea level will drop twice precipitously between 136,000 and 135, 000 years in Red Sea and Papua, New Guinea. These results will constrain the timing of sea-level rise during the penultimate deglaciation.

This article presents views of paleoclimatologists about Earth's climate. Indeed, the revival of the Snowball Earth hypothesis almost 7 years ago has bogged down of late, as paleoclimatologists have failed to turn up unequivocal evidence that ice enrobed the planet. A group of geochemists offers a new snowball marker: the element iridium, which continually rains down on us from space. They say they found so much iridium deposited at the end of a glaciation 635 million years ago that the planet must have been frozen pretty much solid for 12 million years straight.