scholarly journals Uncertainties in the atmospheric loading to ice-sheet deposition for volcanic aerosols and implications for forcing reconstruction

2021 ◽  
Author(s):  
Ya Gao ◽  
Chaochao Gao
Keyword(s):  
Monte Carlo ◽  
Radiative Forcing ◽  
Conversion Factor ◽  
Ice Core ◽  
Monte Carlo Sampling ◽  
Polar Ice ◽  
West Antarctic ◽  
Atmospheric Loading ◽  
Paleoclimate Simulation ◽  
Volcanic Aerosols

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 combing observations of nuclear tomb test debris in Greenland and volcanic sulfate aerosols in Antarctic was derived and widely applied in the CMIP5 and CMIP6 simulations. This study revisits the LTD factor, by using 58 polar ice core records of volcanic depositions and a Monte Carlo sampling model. A set of Tambora-based LTDs with associated uncertainties are obtained, which corrects the bias of over-representing the west Antarctic. New LTDs for Pinatubo and Agung are calculated using 18 and 24 Antarctic ice core observations, respectively, and the uncertainties are evaluated against the Monte Carlo characterization with varying ice core numbers. The comparison of Southern Hemispheric LTD among Tambora, Pinatubo and Agung suggests that, the conversion factor may vary significantly among different eruptions. Even larger uncertainty is revealed when compare the ice-core-based conversion factor with the model results. Both results suggest systematic and stochastic causes that are difficult to anticipate, and call for precaution when single conversion factor is used for reconstruction.

scholarly journals Multi-model comparison of the volcanic sulfate deposition from the 1815 eruption of Mt. Tambora

2017 ◽  
Author(s):  
Lauren Marshall ◽  
Anja Schmidt ◽  
Matthew Toohey ◽  
Ken S. Carslaw ◽  
Graham W. Mann ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Model Comparison ◽  
Ice Core ◽  
Ice Cores ◽  
Sulfate Aerosol ◽  
Polar Regions ◽  
Polar Ice ◽  
Climatic Effects ◽  
Sulfate Deposition ◽  
Ice Core Records

Abstract. The eruption of Mt. Tambora in 1815 was the largest volcanic eruption of the past 500 years. The eruption had significant climatic impacts, leading to the 1816 Year Without a Summer and remains a valuable event from which to understand the climatic effects of large stratospheric volcanic sulfur dioxide injections. The eruption also resulted in one of the strongest and most easily identifiable volcanic signals in polar ice cores, which are widely used to reconstruct the timing and atmospheric sulfate loading of past eruptions. As part of the Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP), four state-of-the-art global aerosol models simulated this eruption. We analyse both simulated background (no Tambora) and volcanic (with Tambora) sulfate deposition to polar regions and compare to ice core records. Background sulfate deposition is of similar magnitude across all models and compares well to ice core records. However, volcanic sulfate deposition varies in timing, spatial pattern and magnitude between the models. Mean simulated deposited sulfate on Antarctica ranges from 19 to 264 kg km−2, and on Greenland from 31 to 194 kg km−2, as compared to the mean ice core-derived estimates of roughly 40–50 kg km−2, for both Greenland and Antarctica. The ratio of the hemispheric atmospheric sulfate aerosol burden after the eruption to the average ice sheet deposited sulfate varies between models by up to a factor of 15. Sources of this inter-model variability include differences in both the formation and the transport of sulfate aerosol. Our results highlight the uncertainties and difficulties in deriving historic volcanic aerosol radiative forcing of climate, based on measured volcanic sulfate in polar ice cores.

scholarly journals Improved estimates of preindustrial biomass burning reduce the magnitude of aerosol climate forcing in the Southern Hemisphere

2021 ◽  
Vol 7 (22) ◽  
pp. eabc1379
Author(s):  
Pengfei Liu ◽  
Jed O. Kaplan ◽  
Loretta J. Mickley ◽  
Yang Li ◽  
Nathan J. Chellman ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Radiative Forcing ◽  
Ice Core ◽  
Ice Cores ◽  
Terrestrial Ecosystems ◽  
Rapid Expansion ◽  
Past Century ◽  
Fire Emissions ◽  
The Past ◽  
Fire Activity

Fire plays a pivotal role in shaping terrestrial ecosystems and the chemical composition of the atmosphere and thus influences Earth’s climate. The trend and magnitude of fire activity over the past few centuries are controversial, which hinders understanding of preindustrial to present-day aerosol radiative forcing. Here, we present evidence from records of 14 Antarctic ice cores and 1 central Andean ice core, suggesting that historical fire activity in the Southern Hemisphere (SH) exceeded present-day levels. To understand this observation, we use a global fire model to show that overall SH fire emissions could have declined by 30% over the 20th century, possibly because of the rapid expansion of land use for agriculture and animal production in middle to high latitudes. Radiative forcing calculations suggest that the decreasing trend in SH fire emissions over the past century largely compensates for the cooling effect of increasing aerosols from fossil fuel and biofuel sources.

scholarly journals Refining Estimates of Polar Ice Volumes during the MIS11 Interglacial Using Sea Level Records from South Africa

2014 ◽  
Vol 27 (23) ◽  
pp. 8740-8746 ◽  
Author(s):  
Florence Chen ◽  
Sarah Friedman ◽  
Charles G. Gertler ◽  
James Looney ◽  
Nizhoni O’Connell ◽  
...  
Keyword(s):  
South Africa ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Sea Level Change ◽  
Polar Ice ◽  
Level Change ◽  
Isostatic Adjustment ◽  
West Antarctic ◽  
Numerical Predictions

Abstract Peak eustatic sea level (ESL), or minimum ice volume, during the protracted marine isotope stage 11 (MIS11) interglacial at ~420 ka remains a matter of contention. A recent study of high-stand markers of MIS11 age from the tectonically stable southern coast of South Africa estimated a peak ESL of 13 m. The present study refines this estimate by taking into account both the uncertainty in the correction for glacial isostatic adjustment (GIA) and the geographic variability of sea level change following polar ice sheet collapse. In regard to the latter, the authors demonstrate, using gravitationally self-consistent numerical predictions of postglacial sea level change, that rapid melting from any of the three major polar ice sheets (West Antarctic, Greenland, or East Antarctic) will lead to a local sea level rise in southern South Africa that is 15%–20% higher than the eustatic sea level rise associated with the ice sheet collapse. Taking this amplification and a range of possible GIA corrections into account and assuming that the tectonic correction applied in the earlier study is correct, the authors revise downward the estimate of peak ESL during MIS11 to 8–11.5 m.

Monte Carlo Sampling with Hierarchical Move Sets: POSH Monte Carlo

2009 ◽  
Vol 5 (8) ◽  
pp. 1968-1984 ◽  
Author(s):  
Jerome Nilmeier ◽  
Matthew P. Jacobson
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Sampling
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