Abstract18 – University of Copenhagen

Primary aerosol (sea salt and soil dust) deposited in Greenland ice during the last climatic cycle: Comparison with East Antarctic records.

Journal of Geophysical Research, Vol. 102, No. C12, p. 26,681-26,698, 1997

M. De Angelis, M. Legrand
Laboratoire de Glaciologie et de Geophysique de l'Environnement, Centre National de la Recherche Scientifique St. Martin d'H&eacuteres, France.
J.P. Steffensen, H.B. Clausen and C.U. Hammer
Departement of Geophysics, The Niels Bohr Institute of Astronomy, Physics and Geophysics, University of Copenhagen .

Ion chromatography data of Ca, Mg, Cl and Ca and Coulter counter particle measurements are used to study the cycle of marine and continental primary aerosol reaching Greenland in relation to climatic changes over the last 150 kyr. A detailed comparison between Greenland (Dome Summit) and Antarctic (Vostok) records provides new insight on a potential link between northern and southern patterns. Ca is a good indicator of continental input and is mainly emitted as CaCO3. An attemp is made to estimate the contribution of aluminosilicates using the concentration of insoluble particles greater than 0.5 µm in diameter. The relative abundance of non-sea-salt Mg and Ca and of aluminosilicate shows that the calcium content of continental background aerosol over Greenland was much higher during the glacial age. The neutralization capacity of carbonaceous aerosol is estimated. The inverse relationship between δ18O and continental input as well as the response of this input to the rapid climatic variations that have occured during the second part of the glacial age are discussed in terms of source and transport modification in relation to the presence and the extent of the great Laurentide ice cap. The corresponding Vostok profiles strongly suggest that some of the phenomena observed at high northern latitudes are of global concern. The marine component of Na is a good tracer of sea-salt aerosol. Similarly to continental input, it shows an inverse but more linear relationship with δ18O. The sensitivity of Greenland and Antarctic marine input to climate variations of small and large amplitude is compared, and a corresponding estimation is made for the aeolian contribution. The respective influence of atmosopheric circulation and the water vapor cycle is discussed. The chlorine to marine sodium weight ratio increases with temperature from values very close to the bulk seawater ratio during the last glacial maximum (18-20 kyr B.P.) to values significantly higher during the Holocente and warm Eemian. The corresponding excess of chloride (HCl) is discussed in terms of atmospheric transport, taking into account the role of atmospheric acidity on sea-salt fractionation processes. Owing to postdepositional phenomene, similar Vostok data must be considered cautiously. Nevertheless, aerosol fractionation seems to have been more important over the Vostok site, except during glacial extrema.