On interannual to decadal time scales tropospheric Antarctic circulation is driven by three forces: ENSO (El Niño Southern Oscillation), AAO (Antarctic Oscillation or Southern Annular Mode), and potentially ACW (Antarctic Circumpolar Wave) but there is widespread disagreement on their relative influences and temporal robustness.We present high resolution records from three snow pits from the McMurdo Sound region (Victoria Lower Glacier, Evans Piedmont Glacier and Mt Erebus). The snow pits are dated using annual layer counting and represent up to ~50 years. Water chemistry (major ion Ca, K, Mg, Na & Cl, NO3, SO4, trace elements Al, Fe, Mn, P, S, Si, Sr), isotopic ratios (oxygen, deuterium, and d-excess data), dust concentration, and density fluctuations are presented. The ice core proxies were calibrated to meteorological (AWS) data using transfer functions.Our data support the concept of a double-sided ENSO effect in the Ross Sea Region, but show that the ENSO forcing is non-linear and non-stationary. We suggest a new mechanism that could explain a teleconnection with positive feedbacks between ENSO and AAO. Furthermore, we present data from a firn core from Victoria Lower Glacier representing the last millennium. The core has been dated using volcanic benchmarks found in the non-seasalt SO4 signal. The isotope record indicates a reoccurring pattern of rapid changes between cooler and warmer climate modes, suggesting that the relative influence of ENSO and AAO and possibly ACW has varied through time.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL6-Earth climate variability since the Pliocene