Anomalous accumulation rates in the Vostok ice‐core resulting from ice flow over Lake Vostok

Abstract

The accumulation rate of snow is crucial to the development of accurate age-depth models for ice-cores. The dating of the Vostok ice-core assumes that accumulation rates generally vary linearly between the core site and the ice divide 250 km to the west [Jouzel et al., 1996; Lorius et al., 1985; Petit et al., 1999], an assumption which impacts the timing of prominent climatic transitions. We present evidence for a local accumulation rate anomaly at the ice surface above the western shoreline of Lake Vostok. A significant thickening between isochronous layers results from this geographically fixed high accumulation zone which can be stratigraphically traced to a depth of 820-1100 m in the Vostok ice-core, a portion known for its high accumulation rates and paleoclimate records that deviate from other Antarctic ice-core records. This non-climatic accumulation anomaly in the Vostok ice-core impacts the flow dependent age models and subsequent interpretations of sequencing of global climate shifts during the last glacial. Additional unrecognized accumulation anomalies are likely present at other depths in this and other cores. These previously unreported geographically fixed accumulation rate anomalies are introduced into ice-cores drilled away from ice domes (e.g., Byrd and Vostok) and should be considered in age depth models.