Uncertainties in the atmospheric loading to ice-sheet deposition for
volcanic aerosols and implications for forcing reconstruction
Abstract
Volcanic radiative forcing reconstruction is an important part of
paleoclimate simulation and attribution efforts, and the conversion
factor used to transfer ice core-based sulfate observation into
stratospheric volcanic aerosol loading (LTD factor) is critical for such
reconstruction. A Pinatubo-based LTD was proposed and adapted in the
CMIP5 and CMIP6 volcanic forcing, under the assumption that all tropical
eruptions follow the same atmospheric transport and deposition pattern.
This study revisits the LTD factor using a large collection of polar ice
core records of Tambora deposition and a Monte Carlo sampling model. A
new set of LTDs with associated uncertainties are obtained, which is in
approximate with our previous Pinatubo-based LTD estimation in
Greenland, while corrects the bias of over-representing the west
Antarctic. The uncertainties revealed from the Monte Carlo simulation
suggest that, difference in the ice core abundance only introduce
limited uncertainty in LTD for individual eruption, once reach a certain
threshold (about 15 in Greenland and 20 in Antarctic). The comparison of
Southern Hemispheric LTD among Tambora, Agung, and Pinatubo suggests
that, the conversion factor may vary for individual eruption. Results
obtained from this study may ease our conventional proneness to use as
much ice core observations as available to estimate icecap volcanic
deposition, while emphasize the importance to build a distribution of
the LTD ideally for eruptions with different size and locations.
Meanwhile, the estimated sets of Tambora-based LTDs could serve as a
compromising choice in future volcanic forcing reconstruction work,
especially when Tambora is utilized as a reference