Abstract:
Explosive volcanic eruptions are very violent events, each with
clearly individual characteristics. Instead of looking at specific eruptions,
we focus here on the long term record of tropical explosive volcanism. To
assess the distribution of volcanic occurrences over several centuries we
employ sulfate measurements from polar ice cores. From these measurements, we
compile a binary time series
... of sulfate deposition events that left a
signature at both poles. Because of the binary nature of this problem, a
series of logistic statistical models are compared to best represent the data.
These models demonstrate the existence of a strong multi-decadal variation in
the occurrence of sulfur rich tropical eruptions. More precisely, a
combination of a trend and a cycle explains best the evolution of eruption
history. To corroborate this result with a record independent of the ice
cores, we confirm these long-term variations with the most recent Volcanic
Explosivity Index (VEI).
This data set consists of a large number of well-dated ice cores that were
compiled, and sulfate spikes present in cores from both hemispheres are
interpreted to indicate climatically important eruptions in the tropics
(30N?30S). (Please see
ftp://ftp.ngdc.noaa.gov/paleo/climate_forcing/volcanic_aerosols/amm...
tions.pdf for listing of individual eruptions) 
