Search

A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage 20.2, ∼800,000 years ago. Experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation. We assessed the general correspondence between Dansgaard-Oeschger events and their smoothed Antarctic counterparts for this Dome C record, which reveals the presence of such features with similar amplitudes during previous glacial periods. We suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records. [ABSTRACT FROM AUTHOR]

We propose that from ∼3 to 1 million years ago, ice volume changes occurred in both the Northern and Southern Hemispheres, each controlled by local summer insolation. Because Earth's orbital precession is out of phase between hemispheres, 23,000-year changes in ice volume in each hemisphere cancel out in globally integrated proxies such as ocean δ18O or sea level, leaving the in-phase obliquity (41,000 years) component of insolation to dominate those records. Only a modest ice mass change in Antarctica is required to effectively cancel out a much larger northern ice volume signal. At the mid-Pleistocene transition, we propose that marine-based ice sheet margins replaced terrestrial ice margins around the perimeter of East Antarctica, resulting in a shift to in-phase behavior of northern and southern ice sheets as well as the strengthening of 23,000-year cyclicity in the marine δ18O record. [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]

Two hypotheses have been put forward to explain the large and abrupt climate changes that punctuated glacial time. One attributes such changes to reorganizations of the ocean's thermohaline circulation and the other to changes in tropical atmosphere-ocean dynamics. In an attempt to distinguish between these hypotheses, two lines of evidence are examined. The first involves the timing of the freshwater injections to the northern Atlantic that have been suggested as triggers for the global impacts associated with the Younger Dryas and Heinrich events. The second has to do with evidence for precursory events associated with the Heinrich ice-rafted debris layers in the northern Atlantic and with the abrupt Dansgaard-Oeschger warmings recorded in the Santa Barbara Basin. [ABSTRACT FROM AUTHOR]

Uses the model-derived equilibrium line attitudes (ELA) of former tropical glaciers to examine the climate of tropical regions during glacial periods. Sensitivity tests suggesting average sea surface temperatures; Comparison of the climates in the Peruvian Andes and Papua New Guinea.

The free-air gravity trend over Canada, derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission, robustly isolates the gravity signal associated with glacial isostatic adjustment (GIA) from the longer-time scale mantle convection process. This trend proves that the ancient Laurentian ice complex was composed of two large domes to the west and east of Hudson Bay, in accord with one of two classes of earlier reconstructions. Moreover, GIA models that reconcile the peak rates contribute ∼25 to ∼45% to the observed static gravity field, which represents an important boundary condition on the buoyancy of the continental tectosphere. [ABSTRACT FROM AUTHOR]

Focuses on the process involved in the occurrence of the last interglacial. How deep-sea sediments provide information on past global climates; Information on the occurrence of the first major invasion of cool waters and icebergs into the central North Atlantic; Alternative interpretation of the Eemian demise.

The article focuses on the impact of environmental changes on civilization. Anthropological archaeologists have examined the significance of environmental influences, such as climate patterns and shoreline movements due to shifting sea level. They compared local climatic and geographical changes with concurrent societal developments in specific regions of the Persian Gulf between 15,000 and 6000 years ago. They found that early societal development was shaped by the formation of productive estuaries, the availability of ample fresh water, and the ability to transport goods over water. Climatic changes particularly the increase in aridity between 6000 and 5000 years ago play an important role in fostering the consolidation of settlements. They found that the emergence of highly organized urban society was the result of the glacial-inter-glacial cycle and related climate changes.