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Identification of bomb-produced chlorine-36 in mid-latitude glacial ice of North America

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms

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DOI: 10.1016/S0168-583X(96)00717-3

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Abstract

In 1991, the U.S. Geological Survey collected a 160-meter (m) ice core from the Upper Fremont Glacier (43??07???N, 109??36???W) in the Wind River Mountain Range of Wyoming in the western United States [1]. In 1994-95, ice from this core was processed at the National Ice Core Laboratory in Denver, Colorado, and analyzed for chlorine-36 (36Cl) by accelerator mass spectrometry at PRIME Laboratory, Purdue University. A tritium bomb peak identified in the work by [1] was used as a marker to estimate the depth of bomb-produced 36Cl. Tritium concentrations ranged from 0 tritium units (TU) for older ice to more than 300 TU at 29 m below the surface of the glacier, a depth that includes ice that was deposited as snow during nuclear-weapons tests through the early 1960's. Maximum 36Cl production during nuclear-weapons tests was in the late 1950's; therefore, the analyses were performed on ice from a depth of 29.8 to 32 m. Calculated flux for 36Cl in ice deposited in the late 1950's ranged from 1.2 ?? 0.1 ?? 10-1 atoms/cm2 s for ice from 29.8 to 30.4 m, to 2.9 ?? 0.1 ?? 10-1 atoms/cm2 s for ice from 31.5 to 32.0 m. Ice samples from a depth of 104.7 to 106.3 m were selected to represent pre-weapons tests 36Cl flux. Calculated flux for 36Cl in this deeper ice was 4.6 ?? 0.8 ?? 10-3 atoms/cm2 s for ice from 104.7 to 105.5 m and 2.0 ?? 0.2 ?? 10-2 atoms/cm2 s for ice from 105.5 to 106.3 m. These flux calculations from the Upper Fremont Glacier analyses are the first for bomb-produced 36Cl in ice from a mid-latitude glacier in North America. It may now be possible to fully quantify the flux of 36Cl from nuclear-weapons tests archived in mid-latitude glacial ice and to gain a better understanding of the distribution of 36Cl and other cosmogenic nuclides.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Identification of bomb-produced chlorine-36 in mid-latitude glacial ice of North America
Series title:
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
DOI:
10.1016/S0168-583X(96)00717-3
Volume
123
Issue:
1-4
Year Published:
1997
Language:
English
Publisher:
Elsevier
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
First page:
287
Last page:
289
Number of Pages:
3