Ideas and perspectives: Emerging contours of a dynamic exogenous kerogen cycle

Abstract

Growing evidence points to the dynamic role that kerogen is playing on the Earth's surface in controlling atmospheric chemistry over geologic time. Although quantitative constraints on weathering of kerogen remain loose, its changing weathering behavior modulated by the activity of glaciers, suggest that this largest pool of reduced carbon on Earth may have played a key part in atmospheric CO2 variability across recent glacial-interglacial times and beyond. 10

Fossil organic carbon utilization in marine Arctic fjord sediments

“…However, within the last two decades, several studies have investigated the availability of OC petro from different sources as a substrate for microbes, painting a more diverse picture of its bioavailability 2,7−9 . A proper assessment of OC petro bio-availability and its potential impact on global GHG concentrations becomes increasingly important as more evidence of microbes' role in releasing GHGs from OC petro into the atmosphere is discovered 10,11 .…”

“…However, considering the size 17 of the reservoir and the vulnerability of the glacial ecosystems 19 , further quantitative research into this topic is necessary. Recent studies of the environment based on both modern glacial sediments 51 and paleo CO 2 isotopic compositions 11 indicate that similar utilization of old, previously "locked up" OC may also occur on shore, indicating a larger geographical scope of OC petro utilization. Therefore, in order to fully grasp the impact of glacial retreat on global carbon budgets, studying these processes in both marine and terrestrial settings may be needed, given the IPCC projections based on the low emission RCP2.6 scenario predict global glacial mass loss of 18% in 2100 relative to 2015, suggesting long lasting effects even in the event of zero anthropogenic GHG emissions 19 .…”

“…However, within the last two decades, several studies have investigated the availability of OC petro from different sources as a substrate for microbes, painting a more diverse picture of its bioavailability 2,7−9 . A proper assessment of OC petro bio-availability and its potential impact on global GHG concentrations becomes increasingly important as more evidence of microbes' role in releasing GHGs from OC petro into the atmosphere is discovered 10,11 .Previous work focused on dissolved organic carbon (OC) from glacial runoff, showing it to be highly bioavailable, despite its old age 12,13 . Although microbial communities may play a crucial role in glacial nutrient and carbon cycling 14,15 , the extent to which the particulate OC supplied by glaciers can be utilized by microbes after its redeposition is virtually unexplored.…”

Deglacial release of petrogenic and permafrost carbon from the Canadian Arctic impacting the carbon cycle

“…One can also imagine that glacial retreat directly leads to exposure to the atmosphere of organic carbon (OC) that has been isolated for many millennia and the oxidation of which may be important for the OC-rich regions. More recently, ice-sheet retreat and the subsequent exposure of its underlying shales have received attention to explain the CO 2 increases 10 .…”

“…The above lines of evidence support rather substantial OC petro mobilization for the previously glaciated continents and imply extensive OC petro oxidation during the last deglaciation. It further raises questions, depending on the magnitude of carbon release, whether the processes are connected to the millennial-scale CO 2 increases during glacial terminations 10 .…”