Using the deuterium isotope composition of permafrost meltwater to constrain thermokarst lake contributions to atmospheric CH4 during the last deglaciation
Dates
Year
2012
Citation
Brosius, L. S., Walter Anthony, K. M., Grosse, G., Chanton, J. P., Farquharson, L. M., Overduin, P. P., and Meyer, H., 2012, Using the deuterium isotope composition of permafrost meltwater to constrain thermokarst lake contributions to atmospheric CH4 during the last deglaciation: Journal of Geophysical Research.Biogeosciences, v. 117, no. 1, n/a p.
Summary
Thermokarst lakes are thought to have been an important source of methane (CH4) during the last deglaciation when atmospheric CH4 concentrations increased rapidly. Here we demonstrate that meltwater from permafrost ice serves as an H source to CH4 production in thermokarst lakes, allowing for region-specific reconstructions of ?DCH4 emissions from Siberian and North American lakes. ?DCH4 reflects regionally varying ?D values of precipitation incorporated into ground ice at the time of its formation. Late Pleistocene-aged permafrost ground ice was the dominant H source to CH4 production in primary thermokarst lakes, whereas Holocene-aged permafrost ground ice contributed H to CH4 production in later generation lakes. We found that Alaskan [...]
Summary
Thermokarst lakes are thought to have been an important source of methane (CH4) during the last deglaciation when atmospheric CH4 concentrations increased rapidly. Here we demonstrate that meltwater from permafrost ice serves as an H source to CH4 production in thermokarst lakes, allowing for region-specific reconstructions of ?DCH4 emissions from Siberian and North American lakes. ?DCH4 reflects regionally varying ?D values of precipitation incorporated into ground ice at the time of its formation. Late Pleistocene-aged permafrost ground ice was the dominant H source to CH4 production in primary thermokarst lakes, whereas Holocene-aged permafrost ground ice contributed H to CH4 production in later generation lakes. We found that Alaskan thermokarst lake ?DCH4 was higher (?334 ± 17[per thousand]) than Siberian lake ?DCH4 (?381 ± 18[per thousand]). Weighted mean ?DCH4 values for Beringian lakes ranged from ?385[per thousand] to ?382[per thousand] over the deglacial period. Bottom-up estimates suggest that Beringian thermokarst lakes contributed 15 ± 4 Tg CH4 yr?1 to the atmosphere during the Younger Dryas and 25 ± 5 Tg CH4 yr?1 during the Preboreal period. These estimates are supported by independent, top-down isotope mass balance calculations based on ice core ?DCH4 and ?13CCH4 records. Both approaches suggest that thermokarst lakes and boreal wetlands together were important sources of deglacial CH4.