Holocene secular variations in dust transport to east Antarctica (Vostok and Dome-C): a response to solar forcing?
Two Holocene sections from EPICA-Dome C and Vostok ice cores have been analysed at high temporal resolution (1 sample per 40 and 50 yrs respectively) for continental dust concentration and size distribution. A new Holocene record of the cosmogenic isotope 10Be has also been obtained from the Vostok ice core, and the chronologies of all three records are tightly linked by stratigraphic markers. Both dust records of size distribution, good proxy for the efficiency of atmospheric dust transport to the Antarctic plateau, clearly show secular oscillations in the 200-year band that are opposite in phase between the two sites. This suggests a secular variability in the efficiency of dust advection to East Antarctica and a regional character of dust transport. The combined dust record and the 10Be record appear highly coherent in the 200-year band, but the atmospheric response to solar forcing seems lagged by about 50 years. We speculate an amplification by the Southern Ocean: sea ice can interact with atmospheric circulation both responding to atmospheric conditions and modifying the cyclonic behaviour and sea ice itself. We performed a sensitivity test with the LMDz atmosphere-only general circulation model with present-day and modified sea-surface conditions, and the model response evidence that Antarctic ocean surface temperature anomalies propagate vertically to high levels in the troposphere, likely affecting dust advection. Such an amplification of solar frequencies by the Southern Ocean can allow a combination of them and originate the millennial-scale oscillations also present in EPICA dust record.
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003