Variability in the SO ]-and C 1-time series for the 1980 s from 12 shallow snow

Variability in the SO]and C1time series for the 1980s from 12 shallow snow pits a•ross the Greenland ice sheet is used to ewlua, te the record of the 1982 E1 Chich6n eruption •nd the potential for recording • moderate northern equatorial eruption in • single Greenland ice core. Composition of volcanic glass found in spring 1983 snow in one of the pits in the Summit region m•tches that from E1 Chich6n glass, thereby verifying the deposition of m•teri•l from the eruption. High N• + •nd C1concentrations in this s•me l•yer probably represent deposition of the ree•ction products of h•lite •nd H2SO4 as observed in the stratosphere following the eruption. These findings •nd the presence of • C1signal in five of the other pits indicate that the C1a•rosol component of some eruptions has the potential to remain •loft for •t least I year Mter the eruption. Some of these •erosols m•y be adsorbed onto tephm p•rticles. Distinct SO• 2pe•ks that c•n be confidently linked to E1 Chich6n were found in only 50% of the records developed through subseasonal s•mpling. However, in several other pits •n elewted baseline, thought to represent more lengthy periods of E1 ChichSn aerosol deposition as opposed to deposition from • single snowfall event, were observed. Smoothing of the original d•t• by the c•lcul•tion of •nnu•l SO]flux resulted in the presence ofhigh flux v•lues between 1982 •nd 1984 (years thought to be •ffcctcd by E1 Chich6n aerosol deposition) in 9 of the 12 pits. These results suggest hat • single ice core from •nywhere in Greenland m•y record • signal from • northern equatorial eruption of m•gnitude similar to that of E1 Chich6n •bout 75% of the time; this is despite the overall high levels of SO]deposition from •nthropogenic sources that now m•ke identification • d qu•ntific•tion ofthe volcanic SO• 2portion of the record more difficult th•n obtaining the s•me d•t• for preindustri•l volcanism. Nevertheless, composite records from •ll the pits s•mpled yielded stmtospheric loading (-,•20 Mt) and optical depth (r: 0.13) estimates imilar to stratospheric and satellite-based measurements following the eruption. Equally high SO• 2concentration and flux values in snow from 1980 to 1982 reflect deposition from the series of middle to high northern latitude volcanic eruptions 1979-1981.