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Global Organic Carbon Cycling Patterns from Ancient and Modern Polar Ice Cores

Ice cores are valuable entities of paleoclimate information. Atmospheric composition reconstructions and transport mechanisms during distinct climate periods are central foci of deep ice core research, with biological contributions gaining rapid acclaim from microbial assessments in extreme environments and organic matter (OM) characterizations recently used to improve our understanding of Earth’s paleoecological history. Fluorescent compositional descriptions of Northern and Southern Hemisphere ice core OM can revolutionize paleoclimate and modern global carbon (C) cycling dynamics, providing essential information of OM origin and reactive nature useful to predict the C impact of our future in a warming climate. OM quality (chemical character) and fluorescence intensity fluctuations coincided with warming and cooling events and may indicate C productivity shifts over time. More biologically reactive fluorescent OM was reported over vast spatial and temporal scales from ancient and modern environments, describing simple, low molecular weight, and less aromatic chemical species prevalent dating back to ~27.0 kyr ago. More complex, terrestrially derived fluorescent OM was only a signature of Holocene ice cores in both hemispheres, describing products of higher C productivity rates in modern environments. Coupling both bulk and molecular level OM compositional assays (fluorescence spectroscopy and ultrahigh resolution mass spectrometry) confirmed distinct OM signature shifts as a function of climate. Outspreading ice core research to routinely incorporate OM characterization is still in its infancy, but its value to other aquatic and terrestrial scientific fields and impact to better understanding disintegrating icy C stores in a warming climate will be monumental.