Abstract
Abstract. Volcanic eruptions are an important cause of natural climate variability. In order to improve the accuracy of climate models, precise dating and magnitude of the climatic effects of past volcanism are necessary. Here we present a 2000-yr record of Southern Hemisphere volcanism recorded in ice cores from the high accumulation Law Dome site, East Antarctica. The ice cores were analysed for a suite of chemistry signals and are independently dated via annual layer counting, with 11 ambiguous years at 23 BCE, which has presently the lowest error of all published long Antarctic ice cores. Independently dated records are important to avoid circular dating where volcanic signatures are assigned a date from some external information rather than using the date it is found in the ice core. Forty-five volcanic events have been identified using the sulphate chemistry of the Law Dome record. The low dating error and comparison with the NGRIP (North Greenland Ice Core Project) volcanic records (on the GICC05 timescale) suggest Law Dome is the most accurately dated Antarctic volcanic dataset, which will improve the dating of individual volcanic events and potentially allow better correlation between ice core records, leading to improvements in global volcanic forcing datasets. One of the most important volcanic events of the last two millennia is the large 1450s CE event, usually assigned to the eruption of Kuwae, Vanuatu. In this study, we review the evidence surrounding the presently accepted date for this event, and make the case that two separate eruptions have caused confusion in the assignment of this event. Volcanic sulphate deposition estimates are important for modelling the climatic response to eruptions. The largest volcanic sulphate events in our record are dated at 1458 CE (Kuwae?, Vanuatu), 1257 and 422 CE (unidentified).
Highlights
Understanding natural causes of climate variability is vital to evaluate the relative impacts of human populations, and, of all the natural causes, volcanic eruptions and solar variation are the two most important (Gao et al, 2007)
Annually resolved ice core record from Law Dome, we have identified and dated 45 volcanic signatures over the past 2000 yr
A comparison with volcanic horizons from the NGRIP ice core, on the well-dated GICC05 timescale, shows Law Dome to be in good agreement, with the age difference between global volcanic horizons of ±3 yr or better
Summary
Understanding natural causes of climate variability is vital to evaluate the relative impacts of human populations, and, of all the natural causes, volcanic eruptions and solar variation are the two most important (Gao et al, 2007). Ice cores dated via accurate layer counting, independent of previously reported volcanic event dates – such as Law Dome – are key to producing high accuracy volcanic chronologies, and improving the dating of events recorded during the first millennium CE, which offers the opportunity to improve correlations between ice cores, as well as better constraining the timing of past volcanic eruptions. Precipitation events at Law Dome occur on average with sufficient frequency to preserve signals at monthly resolution (McMorrow et al, 2001) This allows for high-resolution sampling and this study provides an independently dated, seasonally resolved trace chemistry record spanning the past 2000 yr
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