Recent deposition of 210Pb on the Greenland ice sheet: variations in space and time

Detailed 210Pb profiles were determined for four Chernobyl dated\u27 snowpits sampled during a wide-ranging survey of the Greenland ice sheet during the 1988 season. The profiles from widely separated pits show little or no coherence; even for two pits only 40 km apart the profiles differ in detail. There does not appear to have been any seasonality in the deposition of 210Pb onto the ice sheet in the two years since the Chernobyl accident. The total deposition of 210Pb during this period (10-20 bq m-2) was about 20 times less than has been observed at mid-latitude sites in the eastern United States. The three pits west of the ice-sheet divide recorded very similar depositional fluxes, while the one eastern pit had only two-thirds the average of the others, suggesting a west-to-east gradient in the deposition of 210Pb, and perhaps other continentally-derived submicron aerosols, onto the Greenland ice sheet. -Autho

The Chernobyl Reference Horizon (?) in the Greenland Ice Sheet

Published reports of the presence of radioactive debris from the Chernobyl reactor accident in snow on the Greenland ice sheet raised the strong prospect that such debris might constitute a valuable time stratigraphic marker all over the ice sheet. Large volume snow samples to test this possibility were collected from 7 snowpits as part of a wide ranging regional snow chemistry survey conducted during 1987 and 1988. Snow “labeled” with Chernobyl derived radioactivity was detected in all of the pits. However, the total amount of radioactive debris found at the different locations varied over a 20 fold range. The variability in total fallout showed no clear large scale spatial pattern that could be related to the presumed progress of the radioactive plume over Greenland, suggesting that small scale differences in precipitation pattern and reworking of the snow by wind were predominantly responsible for the patchy preservation of the Chernobyl “layer” on the Greenland ice sheet

Beryllium-7 and Lead-210 in the atmosphere and surface snow over the Greenland ice sheet in the summer of 1989

The concentrations of 7Be and 210Pb were measured in surface air and fresh and aging snow samples from Summit (72°20′N, 38°45′W) and Dye 3 (65°10′N, 44°45′W) Greenland, during June and July 1989. The aerosol concentrations of these radionuclides showed rapid variations at both sites, but were nearly twice as high, on average, at Summit. Concentrations in the 16 fresh snowfall events that were sampled also showed wide variability, but the averages were the same at the two sites. The apparent difference in air-snow fractionation and the lack of coherence in the concentration in air time series between the two sites indicate previously unsuspected complexity in atmospheric dynamics over the ice sheet. Improved understanding of atmospheric processes, and how the results of those processes are recorded in snow and ice, is crucial for full interpretation of the information about past atmospheric chemistry and climate contained in the snow and ice of glaciers around the world