Holocene Secular Variability and 200-Year Dipolar Oscillations in the Atmospheric Circulation Over Antarctica Deduced From ice Core Dust Records

Variability in atmospheric circulation over Antarctica reflects the character of exchanges with the surrounding southern ocean and the complexity of the coupled atmosphere-sea-ice-ocean system. We compared sub-centennial resolution dust records (~1 sample every 50 years) from two 600 km distant East Antarctic ice cores from Vostok and EPICA Dome C, over a period encompassing a large part of the Holocene period. The relative chronology of the two records is well constrained (about +/- 33 years) .by continuous electrical loggings and volcanic markers. The relative proportion of the of coarse or fine aeolian dust transported to the East Antarctic Plateau is taken as a proxy for the atmospheric transport. Based on the size distribution changes observed during volcanic events from distant sources recorded in Antarctic ice, our hypothesis stands that the aeolian dust is differently graded en route according to the altitude of the pathway. The fine-size dust would be associated to the relative contribution from high level air masses subsidence while the coarse-size dust to advection of low troposphere air masses. The two records of the dust size parameters display apparently asynchronous structured variations at secular and millennial frequency. However, the records share common band frequency and one around 200 years. The tighten chronologies allow to built stacked composite records to enhance the signal-to-noise ratio. The stacked row-data composite-sum contains most of energy between 130 and 500 years. Conversely the stacked composite-difference signal displays a prominent 200-yr band oscillation. In the 200-yr band, Vostok and Dome C dust series display a clear correlation but are in opposite phase over the 6 kyr studied period. We suggest the spectrum of the composite-sum represents the variability of the overall meridional atmospheric transport to Antarctica, or the strength of the Antarctic Oscillations coupled to the atmosphere-sea-ice-ocean system. On a other hand, we interpret the 200-yr opposite variations between Vostok and Dome C records as persistent seesaw phenomenon or a dipole in air advection/ subsidence over the two locations, that we associate to the secular variations of the eccentricity of the Antarctic vortex. The marked 200 years band frequency hints to the possible solar influence.