Ice Core Dust Research Articles

Possible solar influences on the dust profile of the GISP2 Ice Core from central Greenland

The Greenland Ice Sheet Project 2 (GISP2) ice core dust profile in glacial (Wisconsinan) ice from Central Greenland has been measured using Laser‐Light Scattering (LLS) from ice. This data exhibits considerable high frequency variability. By applying appropriate running averages to the data, certain regularities emerge. Thus, for example, when the data was smoothed with rectangular 4 and 5 year running averages, ∼11 year dust modulations of considerable amplitude were revealed. In this paper, we show how further smoothing of the data causes very large, longer period dust modulations centered at ∼91 years in a Gaussian distribution to emerge. We believe that this corresponds to the 80–90 year modulation of the 11 year sunspot cycle first suggested by Gleissberg. We also show how adjacent 11 year dust periods can combine in a unique way to generate a 22 year (Hale) period of dust modulation. The way this occurs is similar to that by which a 22 year modulation of the measured terrestrial neutron flux is generated from two 11 year periods. Taken together with our observation of a ∼200 year (Suess) dust modulation period, these observations strengthen our claim that the dust modulations we measured in GISP2 ice are solar induced and suggest a mechanism for their production.

Characteristics of modern atmospheric dust deposition in snow on the Penny Ice Cap, Baffin Island, Arctic Canada

We evaluated the concentration, size and distribution of insoluble dust microparticles in snow-pits on the Penny Ice Cap (PIC), Baffin Island, to define (1) the characteristics of modern atmospheric dust deposition at the site (2) the relative contributions of proximal and distal dust sources, and (3) the effects of summer melting on depositional signals in snow. The mean concentration (143 µg/kg −1 ), flux (4.8 µg cm 2 yr −1 ) and diameter (2.3 µm) of dust deposited on the PIC are similar to those observed in remote Arctic sites such as central Greenland, implying that dust is primarily supplied through long-range transport from far-removed source regions (at least 10 2 –10 3 km distant). There is evidence for two seasonal maxima of dust deposition, one in late winter-early spring and one in late summer-early fall, although seasonal signals can not always be resolved in the snowpack due to some post-depositional particle migration with summer melt. However, ice layers appear to limit the mobility of particles, thereby preserving valuable paleoclimatic information in the PIC ice core dust record at a multi-annual to decadal temporal resolution. DOI: 10.1034/j.1600-0889.1998.t01-1-00008.x

Late Pleistocene Climatic Variations at Achenheim, France, Based on a Magnetic Susceptibility and TL Chronology of Loess

New field investigations of the Achenheim sequence (Alsace, France) allow for the characterization of variations in the low-field magnetic susceptibility over most of the last climatic cycle, i.e., the past 130,000 yr. New stratigraphic data and thermoluminescence measurements permit reassessment of the previous chronological interpretation of the Upper Pleistocene at Achenheim. A high-resolution analysis of magnetic susceptibility discloses the occurrence of a fine-grained “marker” horizon which was also found recently in another section. This horizon is interpreted as a small-scale dust layer deposited prior to the main interval of loess deposition. The horizon, deposited at the marine isotope stage (MIS) 5/4 boundary, has been found in other loess sequences and is especially prevalent in central Europe. It is characterized by low susceptibility values and a grayish color. New thermoluminescence dates indicate that the loess deposition took place after the MIS 5/4 boundary, i.e., after 70,000 yr. These results are consistent with the Greenland GRIP ice-core dust record which also demonstrates a dusty atmosphere after 72,000 yr ago. On a more regional scale, the Achenheim loess sequence demonstrates a reliable correlation between the western side of the Eurasian loess belt and the dust record of the Greenland ice cores.

Characteristics of modern atmospheric dust deposition in snow on the Penny Ice Cap, Baffin Island, Arctic Canada

We evaluated the concentration, size and distribution of insoluble dust microparticles in snow-pits on the Penny Ice Cap (PIC), Baffin Island, to define (1) the characteristics of modern atmospheric dust deposition at the site (2) the relative contributions of proximal and distal dust sources, and (3) the effects of summer melting on depositional signals in snow. The mean concentration (143 μg/kg-1), flux (4.8 μg cm2 yr-1) and diameter (2.3 μm) of dust deposited on the PIC are similar to those observed in remote Arctic sites such as central Greenland, implying that dust is primarily supplied through long-range transport from far-removed source regions (at least 102–103 km distant). There is evidence for two seasonal maxima of dust deposition, one in late winter-early spring and one in late summer-early fall, although seasonal signals can not always be resolved in the snowpack due to some post-depositional particle migration with summer melt. However, ice layers appear to limit the mobility of particles, thereby preserving valuable paleoclimatic information in the PIC ice core dust record at a multi-annual to decadal temporal resolution.

Patagonian origin of glacial dust deposited in East Antarctica (Vostok and Dome C) during glacial stages 2, 4 and 6

The source area of continental dust deposited at both Vostok and Dome C sites (East Antarctica) during the glacial stages (stage 2: ∼ 18 ka (Last Glacial Maximum), stage 4: ∼ 60 ka and stage 6: ∼ 160 ka) of the last two climatic cycles has remained constant. The isotopic composition ( 87Sr 86Sr and 143Nd 144Nd ) of the ice-core dust has been compared with the isotopic composition of the potential source areas: Antarctica, New Zealand, Southern Africa, Australia and South America. This comparison reveals the southern South American provenance of the dust for all three glacial periods, as has already been shown for the LGM [1]. We show that the Patagonian loess and the marine shelf sediments from the Argentine continental shelf, which was variably emerged during glacial periods, display different isotopic compositions and that the composition of the Patagonian loess best matches the signature of the ice-core dust. The identification of the Patagonian region as the source of the windblown dust deposited over East Antarctica during all the latest glacial periods permits a better understanding of paleo-atmospheric circulations of the last climatic cycles and a better constraint on the parametrization of dust sources for paleoatmospheric general circulation models.