Ice Core Archives of Mineral Dust - Mineral Dust: A Key Player in the Earth System - page 466

Fig. 18.5 Profiles of oxygen isotope ratios (• 18 O), sodium (representing sea salt inputs) and
calcium (representing dust inputs) in a snow pit from NEEM site in northwestern Greenland.
The regular seasonal deposition of sodium (winter peak) and calcium (spring peaks) is clearly
demonstrated. The red curve shows non-sea salt calcium while the black curve shows total calcium.
Modified after Kuramoto et al. ( 2011 )

During glacial times the seasonal arrival of dust to Greenland is more difficult
to trace, but the dust generally expresses an annual cycle, and high dust levels are
clearly visible in the visual stratigraphy of the ice (Fig. 18.2 ). Together with records
of chemical impurities in the ice that also show a pronounced annual cycle, the dust
signal has been applied for annual layer counting and dating of the Greenland ice
(Andersen et al. 2006 ; Rasmussen et al. 2006 ).

18.3.2.2 Northern Hemisphere Glaciers

Few dust records are available for the lower latitudes of the northern hemi-
sphere. Those regions where reliable ice core records are available include Mount
Kilimanjaro in Africa and the Himalayas and Tibetan Plateau of central Asia. A 1 ka
dust record from Dasuopu glacier in Tibet (Thompson et al. 2000 ) shows variability
driven by changes in Asian monsoon intensity, in addition to a steady rise due to
anthropogenic activity after 1900. The increase of dust due to anthropogenic activity
has recently been questioned, based on a high-resolution dust record from Mount
Everest (Kaspari et al. 2009 ). Older records from the Dunde ice cap (Thompson
et al. 1989 ) demonstrate higher dust concentrations during the glacial, between 10
and 25 ka ago, approximately double the average Holocene dust level. Ice cores
from Kilimanjaro, Tanzania (Thompson et al. 2002 ), demonstrate distinct periods
of high dust fluxes over the past 12 ka, particularly during the “First Dark Age”
approximately 4 ka ago.