BIT index provides insight into global carbon cycle
Understanding natural variability in the global carbon cycle in the past can help us better interpret the variability occurring today, including the impact of anthropogenic emissions of carbon dioxide. The Netherlands Institute for Sea Research (NIOZ) extended upon previous research using core samples from the ocean floor to shed light on carbon cycling during the Quarternary period. The 6C project, which was supported by the Energy, Environment and Sustainable Development Programme, targeted organic material transported by icebergs. The institute scientists looked beyond traditional carbon indices, such as total organic carbon (TOC) and the relative measurement of the proportion of C13 to C12, d13C of TOC (d13Corg), to glycerol dialkyl glycerol tetraethers (GDGTs). Sediment cores from the floor of the Atlantic Ocean were analysed for GDGTs stretching back 30,000 years before present. They focussed on branched GDGTs and crenarchaeol, a marine isoprenoid GDGT, which they combined into a Branched isoprenoid tetraether (BIT) index. The BIT index compared well with d13Corg indications of elevated organic transport via ice rafting. These phenomena, known as the Heinrich events, were more prevalent during glacial periods, though significant variation was evident during the rapid changes in the Earth's climate. Carbon dating also confirmed the existence of older than expected materials in the deposits. Further to the encouraging results with the BIT index, NIOZ and its 6C partners published articles in relevant scientific journals. Efforts were also planned to use the index to quantify carbon transfer prior to the Quarternary period.
