HR: 0800h
AN: P31B-0980    [Abstracts]
TI: Did Dust From the 1930s US Dust Bowl Make it to Greenland?
AU: Biscaye, P E
EM: biscaye@LDEO.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Rte. 9W, Palisades, NY 10964 United States
AU: Bory, A J
EM: abory@bas.ac.uk
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Rte. 9W, Palisades, NY 10964 United States
AU: Bory, A J
EM: abory@bas.ac.uk
AF: British Antarctic Survey, High Cross, Madingly Rd., Cambridge, NJ 07675 United Kingdom
AU: * Gill, T E
EM: tegill@utep.edu
AF: Dept. of Geological Sciences, Univ. of Texas at El Paso, El Paso, TX 79968 United States
AU: Steffensen, J
EM: jps@gfy.ku.dk
AF: Dept. of Geophysics, Univ. of Copenhagen, Copenhagen, NJ 07675 Denmark
AB: The ­Dust Bowl­" phenomenon during the 1930s in the southwestern United States generated huge amounts of airborne dust with eastward transport of mineral aerosol. Amidst the normal flux of dust from China and Mongolia to the Greenland ice cap, were there any ­Dust Bowl­" years during which North American dust made significant deposits, or were even detectable? Donarummo et al. (2003) reported a possible instance of Dust-Bowl dust during 1933 from the GISP2 ice core drilled at Summit in central Greenland. Did this occur elsewhere in other years? At the NorthGRIP (75 N; 042 W) ice camp in 2001, we drilled four shallow firn cores (~ 1 m apart and 25.0 m deep) to the level of 1930 firn. We divided the cores into the four periods 1930-1945, 1945-1960, 1960-1980, and 1980-1990, and combined the appropriate intervals of all four cores in order to recover sufficient dust. If the southwestern U.S. dust were to be detected during the primary Dust-Bowl years (1930-1945 interval), we expected to see the signal return to pure East Asian characteristics over the course of the subsequent three periods. The four composite firn samples were melted, the dust extracted in the field by super-centrifugation, and returned to LDEO. Non-destructive XRD analyses for clay mineralogy preceded dissolution, chemical purification and analysis of radiogenic isotope composition (ŸONd(0) and 87Sr/86Sr) by Thermal Ionization Mass Spectrometry. The results of these analyses were compared to our samples of Chinese and Mongolian desert material, to samples of known Dust-Bowl dust, and to all the samples of ice-core and snow-pit dust from Greenland we had previously analyzed. These comparisons reveal no hint of compositional change from Asian toward Dust-Bowl characteristics. We conclude that the single possible occurrence of Dust-Bowl dust in 1933 ice reported by Donarummo et al. (2003) did not at all characterize the entire Dust-Bowl era in Greenland. We have also previously shown that the mineralogical and radiogenic isotope composition of dust in Greenland ice is the same at multiple high-altitude, interior, ice-cap locations (Bory et al., 2003), so the 300 km that separate our NorthGRIP results and the single possible result at GISP2 (Summit) is probably not significant. The answer to the question posed in the title is: ­Perhaps once, but not often, and not volumetrically significantly." References: -Bory et al., Geochem., Geophys., Geosys., v.4, 1107,doi:10.1029/2003GC000627, 2003 -Donarummo et al., Geophys. Res. Let. 30(6):1269, , doi:10.1029/2002GL016641, 2003
DE: 9350 North America
DE: 3319 General circulation
DE: 1040 Isotopic composition/chemistry
DE: 0305 Aerosols and particles (0345, 4801)
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting