Re-evaluating the 1257 AD eruption using annually-resolved ice core chemical analyses

Abstract:

The source of the 1257 AD volcanic eruption has recently been proposed to be Samalas in Indonesia. The eruption was one of the largest of the Holocene and has been recorded in ice cores in both hemispheres from sulfate and acidity measurements. The estimate of its sulfate load varies from 2 to 8 times that of Tambora. This is also the only volcano for which tephras have been assigned in ice cores from both Antarctica and Greenland (GISP2). Due to this unique assignment of a bipolar tephra layer in ice cores, the origins of the sulfate and tephras have been disputed and it has been proposed that at least one of the tephras was due to an additional volcanic eruption local to either Greenland or Antarctica.

We have re-evaluated the acid and tephra deposition from the 1257 AD volcano in two ice cores, one from Greenland (NGRIP. 75.1° N, 42.3° W) and one from Antarctica (RICE, Roosevelt Island. 79.36° S, -161.71° W). Annually-resolved continuous flow analysis (CFA) measurements determined relevant parameters such as melt water conductivity, sulphate and acidity. The acidity peak at RICE (~20 uM H+) is approximately double that found at NGRIP (10 uM H+). The only visible tephra layer found in the corresponding depth range was deposited at 1250 AD, 9 years before the acidity peak. The high resolution of the data offers a precise evaluation of the delay between the deposition of tephra and acid (sulfate) in each hemisphere. The comparison between poles allows some evaluation of the spread of deposition from the volcanic eruption.