Atmospheric ethane and acetylene variability over the last 50,000 years from the South Pole Ice Core (SPICEcore)
Abstract
Ethane (C2H6) and acetylene (C2H2) are non-methane hydrocarbons released from combustion processes with sources from fossil fuel use and biomass and biofuel burning. Ethane is also thought to have an additional source via natural geologic emissions. Long term records of these gases from ice cores can inform us about the variability in natural biomass burning and geologic emissions through time.
Here we present measurements of ethane and acetylene over the last 50,000 years measured in air extracted from ice cores samples from the South Pole Ice Core (SPC14). The ice core air was extracted using a wet extraction (melt) method. Glacial period (50-20 ky, [thousands of years before 1950]) acetylene levels are roughly 12 pmol mol-1 or lower, with the lowest level occurring during the 50-30 ky period (less than 5 pmol mol-1). Acetylene increases drastically across the glacial/interglacial transition with the Holocene level in the range from 23-35 pmol mol-1. This variability in Antarctic acetylene from the glacial to interglacial may be caused by climate driven biomass burning emissions. By contrast, the ethane level during the glacial period is high (up to 250 pmol mol-1) with obvious scatter that makes interpreting trends challenging. A slight decline in ethane to a more stable mean between 100 to 150 pmol mol-1 is observed during the Holocene. In ice core samples with high impurity levels from the last glacial period, acetylene and ethane exhibit positive correlations with major ions (calcium, sodium, and sulfate) at the same depth. This suggests that some in situ production of acetylene and ethane may have occurred in those samples, either within the ice core or during the melt. No correlations are observed in glacial or Holocene samples with lower levels of impurities. The acetylene and ethane atmospheric histories and the surprising differences between the variability in the two gases, have implications for the variability in biomass burning and geologic emissions over the past 50,000 years. These implications are explored using a 3-D atmospheric chemistry/transport model and simple biogeochemical box models.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C11C1292N
- Keywords:
-
- 0724 Ice cores;
- CRYOSPHERE;
- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE;
- 1616 Climate variability;
- GLOBAL CHANGE;
- 4994 Instruments and techniques;
- PALEOCEANOGRAPHY