Recent climate anomalies and their impact on snow chemistry at South Pole, 1987-1994

Three 2-m deep snowpits sampled at South Pole in 1994 provide detailed (2-cm resolution) profiles of the concentrations of soluble ionic species for the period 1987 - 1994. The most prominent feature is a large concentration spike of SO4= in snow deposited in 1992 reflecting fallout from the eruptions of Pinatubo and Hudson in 1991. Concentrations of MSA and values of the MSA/(non-sea-salt SO4=) ratio are elevated for about three years centered on the prominent volcanic signal. These changes appear to be due to the extended 1991 - 1993 El Nino. The overlapping effects of the volcanic eruptions and El Nine circulation preclude partitioning the enhanced deposition of SO4= into volcanic and biogenic fractions. Nitrate concentration profiles show no relation to the severity of O-3 depletion in the Antarctic stratosphere during the period of record. Rather, the profiles show a progressive decline of the annual peak concentrations over the top 0.5 - 1.0 m of each pit. This behavior is attributed to post-deposition loss of NO3-, presumably by re-emission of HNO3 into the atmosphere.