Articles | Volume 13, issue 5
Research article
24 May 2017
Research article |  | 24 May 2017

A 21 000-year record of fluorescent organic matter markers in the WAIS Divide ice core

Juliana D'Andrilli, Christine M. Foreman, Michael Sigl, John C. Priscu, and Joseph R. McConnell

Abstract. Englacial ice contains a significant reservoir of organic material (OM), preserving a chronological record of materials from Earth's past. Here, we investigate if OM composition surveys in ice core research can provide paleoecological information on the dynamic nature of our Earth through time. Temporal trends in OM composition from the early Holocene extending back to the Last Glacial Maximum (LGM) of the West Antarctic Ice Sheet Divide (WD) ice core were measured by fluorescence spectroscopy. Multivariate parallel factor (PARAFAC) analysis is widely used to isolate the chemical components that best describe the observed variation across three-dimensional fluorescence spectroscopy (excitation–emission matrices; EEMs) assays. Fluorescent OM markers identified by PARAFAC modeling of the EEMs from the LGM (27.0–18.0 kyr BP; before present 1950) through the last deglaciation (LD; 18.0–11.5 kyr BP), to the mid-Holocene (11.5–6.0 kyr BP) provided evidence of different types of fluorescent OM composition and origin in the WD ice core over 21.0 kyr. Low excitation–emission wavelength fluorescent PARAFAC component one (C1), associated with chemical species similar to simple lignin phenols was the greatest contributor throughout the ice core, suggesting a strong signature of terrestrial OM in all climate periods. The component two (C2) OM marker, encompassed distinct variability in the ice core describing chemical species similar to tannin- and phenylalanine-like material. Component three (C3), associated with humic-like terrestrial material further resistant to biodegradation, was only characteristic of the Holocene, suggesting that more complex organic polymers such as lignins or tannins may be an ecological marker of warmer climates. We suggest that fluorescent OM markers observed during the LGM were the result of greater continental dust loading of lignin precursor (monolignol) material in a drier climate, with lower marine influences when sea ice extent was higher and continents had more expansive tundra cover. As the climate warmed, the record of OM markers in the WD ice core changed, reflecting shifts in carbon productivity as a result of global ecosystem response.

Short summary
Climate-driven trends in fluorescent organic matter (OM) markers from Antarctic ice cores revealed fluctuations over 21.0 kyr, reflecting environmental shifts as a result of global ecosystem response in a warming climate. Precursors of lignin-like fluorescent chemical species were detected as OM markers from the Last Glacial Maximum to the mid-Holocene. Holocene ice contained the most complex lignin-like fluorescent OM markers. Thus, ice cores contain paleoecological OM markers of Earth’s past.