oa Using Individual Late Eluting Brgdgt Isomers to Reconstruct Salinity in European Lakes

As anthropogenic climate change progresses, total global precipitation is expected to increase. However, this will not be evenly distributed, and insights into how hydrological systems have responded to past climate variation are crucial for understanding its future effects on precipitation.

Lacustrine sediments are a key archive of past terrestrial climate change, and record past shifts in precipitation/evaporation as variation in past salinity. Reconstructing such changes, then, is a crucial step towards modelling past climate. However, current proxies for palaeosalinity are imperfect and there lacks a method to quantitatively reconstruct past shifts across the whole range of lacustrine salinities (fresh-hypersaline).

Using brGDGTs, bacterial membrane lipids, we have developed a novel proxy for reconstructing past lacustrine salinity by separating the IIIa and IIa late-eluting isomers (IIIa and IIa) into 5 distinct isomers. Using statistical methods, we have used their fractional abundance to develop a strong proxy ratio, applicable across the complete salinity range (r = 0.88). This proxy shows promise as a new tool in palaeoclimate studies, and may serve to allow for more accurate calibrations of current palaeoclimate proxies (e.g. MBT’5Me).