Abstract
AbstractEthane levels were measured in air extracted from Greenland and Antarctic ice cores ranging in age from 994 to 1918 Common Era (C.E.) There is good temporal overlap between the two data sets from 1600 to 1750 C.E. with ethane levels stable at 397 ± 28 parts per trillion (ppt) (±2 standard error (s.e.)) over Greenland and 103 ± 9 ppt over Antarctica. The observed north/south interpolar ratio of ethane (3.9 ± 0.1, 1σ) implies considerably more ethane emissions in the Northern Hemisphere than in the Southern Hemisphere, suggesting geologic ethane sources contribute significantly to the preindustrial ethane budget. Box model simulations based on these data constrain the global geologic emissions of ethane to 2.2–3.5 Tg yr−1 and biomass burning emissions to 1.2–2.5 Tg yr−1 during the preindustrial era. The results suggest biomass burning emissions likely increased since the preindustrial period. Biomass burning and geologic outgassing are also sources of atmospheric methane. The results place constraints on preindustrial methane emissions from these sources.
Highlights
Ethane (C2H6) is the most abundant nonmethane hydrocarbon in the atmosphere and is an important atmospheric pollutant
During the mid-1700s, atmospheric methane levels began increasing primarily due to the emergence of new anthropogenic sources which emit ethane [Etheridge et al, 1998; MacFarling Meure et al, 2006]
This study presents the first preindustrial atmospheric ethane record based on ice core measurements
Summary
Ethane (C2H6) is the most abundant nonmethane hydrocarbon in the atmosphere and is an important atmospheric pollutant It is removed from the atmosphere via oxidation with the hydroxyl radical (OH) yielding a global average lifetime of roughly 2 months [Xiao et al, 2008]. The major sources of atmospheric ethane today are the production, processing, transmission and use of oil and natural gas, and burning of biofuels, with total global emissions estimated at 11–15 Tg yrÀ1 [Rudolph, 1995; Xiao et al, 2008; Etiope and Ciccioli, 2009; Simpson et al, 2012]. Ethane sources emit methane (CH4), an important atmospheric pollutant and one of the largest contributors to global warming [Hartmann et al, 2013]. Atmospheric ethane variability can be used to constrain methane emissions from nonbiogenic sources [Aydin et al, 2011; Simpson et al, 2012]
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