Regional variability of ice core dust composition and provenance in Greenland

Abstract

[1] Mineralogical and isotopic composition (Sr and Nd) of six dust samples, obtained from six widely spread ice-coring sites in Greenland, were analyzed in order to investigate the regional geographic variability of dust provenance. We show that long-range transport from eastern Asian deserts provides mineral dust with essentially the same composition to all elevated interior sites (Dye 3, Site A, GRIP, and NorthGRIP), while most material deposited at sites located closer to the edge and at lower altitude (Hans Tausen and Renland) derives from proximal source regions. No contribution from other sources is apparent at any of the interior sites from the mineralogical and isotopic composition of the dust samples, each of which represents several decades of dust deposition during the 17th-18th century. These results provide additional evidence that African and North American deserts do not play a significant role in the dust deposited over Greenland, which has implications for ice core record interpretation and atmospheric dust transport model validation.

The influence of regional circulation patterns on wet and dry mineral dust and sea salt deposition over Greenland

“…3a). Ca 2+ in Greenland ice cores predominately derives from mineral dust and the strongest of the associated circulation patterns is in agreement with findings from several sites on the interior GrIS showing dust sources in central Asia (Bory et al 2002(Bory et al , 2003. Easterly flow towards the ice core sites in northeastern Greenland indicated by both the second strongest circulation pattern for Ca 2+ (Fig.…”

“…This also means that there must be some (Asian) dust present in the air masses over the GrIS. This is not unreasonable given that the dust deflated from the Takla Makan Desert, West China, which is thought to be the source supplying most if not all of the mineral particles during the dusty spring season to Greenland, is usually entrained to elevations >5,000 m before being transported by the westerly jet stream over the remote North Pacific Ocean (Sun et al 2001;Bory et al 2002Bory et al , 2003. It can thus be assumed that the comparatively small dust particles arriving at high altitudes over the GrIS region will lead to relatively homogeneous background dust concentrations in the lower atmospheric layers over the Arctic in spring.…”

“…7a) in the dry snow zone of the GrIS. An altitude dependence would be expected for regional dust sources, as seen in Bory et al (2003), because much of the dust mass is progressively deposited when transported from low altitude sources onto the ice sheet. Unlike Ca 2+ , Na + concentrations clearly show this dependency, consistent with its source in the neighbouring seas (Fig.…”

“…Previous research indicated that the dominant fraction of mineral dust deposited over Greenland originates almost exclusively from desert areas in Asia (Bory et al 2002(Bory et al , 2003. The EOF2 Y (NE-Ca) pattern (Fig.…”

Particle shape accounts for instrumental discrepancy in ice core dust size distributions

“…As 30 found for the central Greenlandic ice cores, the glacial RECAP dust comes from central Asia (Biscaye et al, 1997). However, the Holocene dust, like in the old Renland core (Bory et al, 2003), is dominated by a local East Greenlandic source (Bory et al, 2003). The volume mode of the glacial dust is 2 µm, while it is 20 µm for the Holocene dust, due to the increased transport induced size fractionation for the glacial dust (Ruth et al, 2003).…”