نتایج جستجو برای: glacial cirques
تعداد نتایج: 11417 فیلتر نتایج به سال:
Air trapped in glacial ice offers a means of reconstructing variations in the concentrations of atmospheric gases over time scales ranging from anthropogenic (last 200 yr) to glacial/interglacial (hundreds of thousands of years). In this paper, we review the glaciological processes by which air is trapped in the ice and discuss processes that fractionate gases in ice cores relative to the conte...
—The blue-spotted salamander (Ambystoma laterale) has the northern-most distribution of any North American salamander and primarily occurs in areas that were once covered by the southern Laurentide Ice Sheet during the last glacial maximum. We examine the phylogeography of this primary post-glacial invader of northern North America. Mitochondrial DNA sequence data indicate a clade comprised of ...
Previous predictions of sea-level change subsequent to the last glacial maximum show significant, systematic discrepancies between observations at Tahiti, Huon Peninsula, and Sunda Shelf during Lateglacial time (approximately 14,000 to 9000 calibrated years before the present). We demonstrate that a model of glacial isostatic adjustment characterized by both a high-viscosity lower mantle (4 x 1...
Using an ocean-atmosphere climate model we demonstrate that stochastic resonance could be an important mechanism for millennial-scale climate variability during glacial times. We propose that the glacial ocean circulation, unlike today's, was an excitable system with a stable and a weakly unstable mode of operation, and that a combination of weak periodic forcing and plausible-amplitude stochas...
The local last glacial maximum in the tropical Andes was earlier and less extensive than previously thought, based on 106 cosmogenic ages (from beryllium-10 dating) from moraines in Peru and Bolivia. Glaciers reached their greatest extent in the last glacial cycle approximately 34,000 years before the present and were retreating by approximately 21,000 years before the present, implying that tr...
We present new Holocene and glacial dO data measured on planktonic foraminifera Neogloboquadrina pachyderma and benthic foraminifera Cibicidoides species from the Atlantic and Pacific sectors of the Southern Ocean in order to better understand its glacial hydrography. Combined with previously published data, the latitudinal dO distributions of these foraminifera show no appreciable difference d...
Based on genetic studies and palaeoecological surveys, the main Korean mountain range, the socalled “Baekdudaegan” (BDDG), has been recently suggested to be a major glacial refugium at the Last Glacial Maximum (LGM) for the boreal and temperate flora of northeastern Asia. On the basis of its shared role as a glacial refugium, and on a series of striking similarities in floristic richness and or...
Based on the data of temperature changes revealed by means of various palaeothermometric proxy indices , it is found that the magnitude of temperature decrease became large with altitude in the equatorial regions during the Last Glacial Maximum. The direct cause of this phenomenon was the change in temperature lapse rate, which was about ( 0 . 1 ± 0 . 05) 't: / 100 m larger in the equator durin...
Organic carbon buried under the great ice sheets of the Northern Hemisphere is suggested to be the missing link in the atmospheric CO2 change over the glacial-interglacial cycles. At glaciation, the advancement of continental ice sheets buries vegetation and soil carbon accumulated during warmer periods. At deglaciation, this burial carbon is released back into the atmosphere. In a simulation o...
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