Linking the Antarctic tephra record across the continent and beyond

Abstract:

Individual ice cores in Antarctica contain a wealth of paleoclimate and volcanological information that requires robust chronology, one aspect of which is cross-correlation between cores using tephra layers. An array of analytical techniques (SEM, EMPA and LA-ICP-MS) allows for the eruption dynamics and tephra transport to be better understood. Tephra layers analyzed from ice cores and blue ice sites in West Antarctica are dominantly of trachytic composition and derived from local volcanoes in Marie Byrd Land (Mt. Berlin and Mt. Takahe) and Northern Victoria Land (Mt. Melbourne and the Pleiades). Although many tephra from these volcanoes are likely to be widely distributed, a number are only identified in a single core or blue ice site. For instance, the distinctive 8.2ka tephra layer, correlated to Mt. Takahe, can be found as a visible layer in the WAIS and Siple Dome ice cores and in a blue ice area at Mt. Waesche, but, surprisingly, is absent from the RICE core. In some cases, two ice cores only 100m apart may have slightly different tephra records, suggesting non-uniform preservation of tephra. Some of these tephra layers are found in multiple cores and blue ice sites, providing insight into the tephra distribution pattern and precise chronological links between multiple climate records. One prominent regional tephra layer, with a WAIS age of 1252C.E., is found in East (Taylor Dome (Dunbar, 2003) and Talos Dome (Narcisi et al., 2012)) and West (WAIS, Siple Dome (Dunbar and Kurbatov, 2011) and RICE) Antarctic ice cores. This layer, linked to the Pleiades, provides a widespread and unambiguous tie point and exhibits a complex range of trace element composition that may provide information about travel direction of the ash cloud through the duration of the eruption. Many important marker layers are extra-continental tephra from South America and New Zealand and have more distinctive chemistry than the local alkaline volcanoes. One layer is the recently identified Oruanui tephra in the WAIS Divide ice core. This layer is well dated in New Zealand by ¹⁴C (25,360 ±160 cal. yrs B.P) (Vandergoes et al., 2013) and is statistically the same as the modeled ice core age (25,318±380 yrs). Correlations like the Oruanui tephra can now provide links between the terrestrial, marine and ice sheet climate records from Antarctica to New Zealand.