213 research outputs found
Review article A. B. Dobrowolski - the first cryospheric scientist - and the subsequent development of cryospheric science
The origin of the term "cryosphere" has been traced to the Polish scientist A. B. Dobrowolski in his 1923 book on "The Natural History of Ice" written in Polish. This note commemorates his little recognized contribution to the science, outside of his native country, and summarizes the recent organization of cryospheric research
Methodological approaches to determining the marine radiocarbon reservoir effect
The marine radiocarbon reservoir effect is an offset in 14C age between contemporaneous organisms from the terrestrial environment and organisms that derive their carbon from the marine environment. Quantification of this effect is of crucial importance for correct calibration of the <sup>14</sup>C ages of marine-influenced samples to the calendrical timescale. This is fundamental to the construction of archaeological and palaeoenvironmental chronologies when such samples are employed in <sup>14</sup>C analysis. Quantitative measurements of temporal variations in regional marine reservoir ages also have the potential to be used as a measure of process changes within Earth surface systems, due to their link with climatic and oceanic changes. The various approaches to quantification of the marine radiocarbon reservoir effect are assessed, focusing particularly on the North Atlantic Ocean. Currently, the global average marine reservoir age of surface waters, R(t), is c. 400 radiocarbon years; however, regional values deviate from this as a function of climate and oceanic circulation systems. These local deviations from R(t) are expressed as +R values. Hence, polar waters exhibit greater reservoir ages (δR = c. +400 to +800 <sup>14</sup>C y) than equatorial waters (δR = c. 0 <sup>14</sup>C y). Observed temporal variations in δR appear to reflect climatic and oceanographic changes. We assess three approaches to quantification of marine reservoir effects using known age samples (from museum collections), tephra isochrones (present onshore/offshore) and paired marine/terrestrial samples (from the same context in, for example, archaeological sites). The strengths and limitations of these approaches are evaluated using examples from the North Atlantic region. It is proposed that, with a suitable protocol, accelerator mass spectrometry (AMS) measurements on paired, short-lived, single entity marine and terrestrial samples from archaeological deposits is the most promising approach to constraining changes over at least the last 5 ky BP
Problem of the Pliocene/Pleistocene boundary in fresh-water deposits at Mizerna, West Carpathians
TheMizerna site (Polish Western Carpathians) is one of the most important Pliocene palaeobotanic sites in Central Europe. Its fresh-water deposits, laid down in a buried river valley, were studied in detail more than half a century ago in natural exposures and shallow boreholes, prior to partial drowning of the area by an artificial lake. The deposits yielded a very rich macrofossil plant collection elaborated in detail by Szafer (1954) who claimed that they represented a continuous succession of the Pliocene through Early Pleistocene plant communities. First palynological examination of the Mizerna deposits (by Oszast) was made more than half a century ago. Re-evaluation of stratigraphic and palaeoclimatic significance of macrofossil plant remains, along with a reassessment of palaeoenvironmental and sedimentary conditions during formation of the Mizerna fresh-water deposits, is in progress. This may help elucidate the problem whether the Mizerna sediments represent both the Pliocene and Early Pleistocene or, solely, the Pliocene successions
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