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Stratigraphic Analysis of a Deep Ice Core from Greenland
Authors: Langway CC
Year: 1967
Keywords: RR 77, drilling--Greenland, ice--impurities--Greenland, glaciers--age determination, snow cover--accumulation, snow cover--stratigraphy
Periodical/Journal: CRREL Research Report 77
Abstract: A deep rotary core drilling project in 1957 at Site 2 on the Greenland ice sheet (76° 59´N, 56° 04´W) provided ice core to a depth of 411 m. The vertical variation in bulk density, macroscopic structure, oxygen isotope ratios, iconic constituents, and extraterrestrial dust (black spherules) were analyzed using both field and laboratory techniques. These data permit the direct estimate of annual accumulation layers in the core. Continuous stratigraphic measurements and observations were made over the upper 100 m of the profile and detailed physical and chemical analyses were made on continuous 1.3 to 3.9 - m core increments at 100, 200, 300, and 411 - m depths. The average total ionic concentration in the ice sheet ranges between 0.65 and 1.35 mg/liter. The annual global mass deposit of black spherules as calculated from these studies varies from 2.10 X 105 metric tons in 700 year old ice to 6.57 X 105 metric tons in 12 year old firn. The oxygen isotope ratio variation provides the best means of estimating accumulation at depth. Results of the investigations indicate rates of net snow accumulation of 42.3, 34.2, 37.4, 41.1 and 41.6 g/cm2 - yr at the surface, A. D. c. 1773, c. 1513, c. 1233 and c. 934, respectively. Accumulation data and other physical and chemical evidence allow climatoological inferences to be made over the 10 - century profile. The ice core record shows that snow accumulation and temperature in A. D. 934 were similar to today, followed by a gradual decrease in accumulation to a minimum around the late 18th century and an increase in both accumulation and temperature from A. D. 1773 to 1957 and following.
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