Interpreting Rainfall Changes as a result of the 8.2 ka Event through δ2H ratios in the El Junco Lake, Galapagos

Abstract

The most recent major climate perturbation, the “8.2 ka BP Event,” was a result of a mass influx of meltwater from the drainage of Lakes Agassiz and Ojibway into Hudson Bay. An influx of this magnitude has the potential to disrupt the Atlantic Meridional Ocean Circulation (AMOC) and likely also the behavior of the Inter Tropical Convergence Zone (ITCZ). Previous data indicated that the ITCZ shifted south in response to this event. The position of the ITCZ can be resolved from rainfall, which can be measured using the ratio of hydrogen isotopes (δ2H ). δ2H was recorded in several molecular biomarkers collected from marine lake sediments in El Junco Lake, Galapagos Islands, which lies upon the southern edge of the ITCZ. These molecular biomarkers were Hexadecenoic Acid (Palmitic Acid, C16:0); Octacosanoic Acid (Montanic Acid, C28:0); dinosterol, a sterol produced by dinoflagellates, and C34 botryococcene, a sterol unique to Botryococcus Braunii, a form of green algae. δ2H values increase around the time of the 8.2 ka event in dinosterol and botryococcene, which indicates a decrease in precipitation. The concentrations of botryococcene and dinosterol are characteristic of a period of drying. This implied decrease in precipitation, while not statistically significant does not coincide with previous data implying a southward shift of the ITCZ.