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Sulfate concentrations from continuous biyearly sampling of the GISP2 Greenland ice core provide a record of potential climate-forcing volcanism since 7000 B.C. Although 85 percent of the events recorded over the last 2000 years were matched to documented volcanic eruptions, only about 30 percent of the events from 1 to 7000 B.C. were matched to such events. Several historic eruptions may have been greater sulfur producers than previously thought. There are three times as many events from 5000 to 7000 B.C. as over the last two millennia with sulfate deposition equal to or up to five times that of the largest known historical eruptions. This increased volcanism in the early Holocene may have contributed to climatic cooling., Volcanic aerosols have an important role in the Earth's climate, beginning with their contribution to the development of the primordial atmosphere (1). More recently, much interest has focused on the [...]

High-resolution, continuous multivariate chemical records from a central Greenland ice core provide a sensitive measure of climate change and chemical composition of the atmosphere over the last 41,000 years. These chemical series reveal a record of change in the relative size and intensity of the circulation system that transported air masses to Greenland [defined here as the polar circulation index (PCI)] and in the extent of ocean ice cover. Massive iceberg discharge events previously defined from the marine record are correlated with notable expansions of ocean ice cover and increases in PCI. During stadials without discharge events, ocean ice cover appears to reach some common maximum level. The massive aerosol loadings and dramatic variations in ocean ice cover documented in ice cores should be included in climate modeling., During the last glaciation, the North Atlantic region experienced major changes in climate relative to the Holocene (the most recent 10,000 years). The most obvious and dramatic of these changes [...]

Analysis of ice from Dye-3, Greenland, has demonstrated that the transition between the Younger Dryas and Holocene climate periods occurred over a 40-year period. A near annually resolved, multiparameter record of the transition recorded in the GISP2 core from Summit, Greenland, shows that most of the transition occurred in a series of steps with durations of about 5 years. Some climate proxies associated with mid-latitude sources appear to have changed about 15 years before climate proxies associated with more northern regions. Changes in atmospheric water vapor are likely to have played a large role in the climate transition., The Greenland Ice Sheet Project II (GISP2) and Greenland Ice Core Project (GRIP) ice cores were collected at the summit of the Greenland ice sheet at locations selected to obtain [...]

Glaciochemical time series developed from Summit, Greenland, indicate that the chemical composition of the atmosphere was dynamic during the Holocene epoch. Concentrations of sea salt and terrestrial dusts increased in Summit snow during the periods 0 to 600, 2400 to 3100, 5000 to 6100, 7800 to 8800, and more than 11,300 years ago. The most recent increase, and also the most abrupt, coincides with the Little Ice Age. These changes imply that either the north polar vortex expanded or the meridional air flow intensified during these periods, and that temperatures in the mid to high northern latitudes were potentially the coldest since the Younger Dryas event., Our ability to predict the environmental consequences of anthropogenic emissions first requires a thorough understanding of natural atmospheric and climatic variability. Records from Summit, Greenland, ice cores reveal that climate [...]

A depth-age scale and an accumulation history for the Holocene have been established on the Greenland Ice Sheet Project 2 (GISP2) deep core, providing the most continuously dated record of annual layer accumulation currently available. The depth-age scale was obtained with the use of various independent techniques to count annual layers in the core. An annual record of surface accumulation during the Holocene was obtained by correcting the observed layer thicknesses for flow-thinning. Fluctuations in accumulation provide a continuous and detailed record of climate variability over central Greenland during the Holocene. Climate events, including 'Little Ice Age' type events, are examined., The GISP2 ice core was drilled from surface to bedrock to obtain a paleoclimatic history spanning the last 200,000 years. The summit drilling site is located at 72.6N, 38.5 ° [...]

The results of the Greenland ice core GISP2 showing that snow accumulated within one to three years from the Younger Dryas event to the subsequent Preboreal interval is reported. It is well-known that the warming at the end of the last glaciation was punctuated by shifts to glacial climate, of which the 50-year-long Younger Dryas event is the most well-known. The extreme rapidity of climate change indicated by the GISP2 data is remarkable because it suggests that events in the last glaciation may have been a response to a sudden trigger in the North Atlantic climate system.

Comparative studies of the GRIP and GISP2 deep ice cores from Central Greenland show that the small diameters of the cores and the absence of highly reliable stratigraphic data prevent confirmation of the instability of the Eemian record. Some core structures higher than the Eemian are larger than the core diameter and represent inverted strata. Moderate simple-shear deformation is observed in both cores with z-shaped folds and overturned limbs smaller than the core diameter.