The Effects of Glacial Melting on Precipitation Patterns in Jellyfish Lake, Palau Derived from Hydrogen Isotopes in Algal Lipids

Abstract

A meltwater-induced disruption of the Atlantic Meridional Overturning Circulation (AMOC) 8.5- 8 kyr impacted climate globally, with evidence from around the continental Pacific suggesting large perturbations to rainfall patterns. Modeling indicates a southward shift of the tropical rainbands during this time. However, this is largely untested due to a lack of paleoclimate data where the Intertropical Convergence Zone (ITCZ) is well defined. In this project, I analyze hydrogen isotopic data (2H/1H) from well-dated sediment cores taken from Jellyfish Lake, Palau that imply a southward shift of the ITCZ during this time. Due to this lake being a uniquely undisturbed area with a high rate of sediment accumulation, the isotopic composition of dinosterol in these sediments can provide a detailed reconstruction of past rainfall in the tropics. Dinosterol is an organic compound produced exclusively by dinoflagellates, a taxa of photosynthetic microalgae. Through this “molecular fossil,” I can reconstruct the 2H/1H ratio of the lake water and its salinity, both of which are directly tied to rainfall in Palau. To identify and purify the dinosterol found in sediment core samples, I use High-Performance Liquid Chromatography (HPLC), Gas-Chromatography-Mass Spectrometry (GC-MS), and Gas Chromatography-Flame Ionization Detection (GC-FID) instruments. Using Gas Chromatography- Isotope Ratio Mass Spectrometry (GC-IRMS), I found large and systematic fluctuations in the 2H/1H ratios of dinosterol. Thus, the preliminary data demonstrate a trend toward a drier climate in Palau at the time of the glacial meltwater pulse into the North Atlantic 8,200 years ago, consistent with a southward shift of the ITCZ. Over the past century, there has been a substantial increase in glacial melting due to anthropogenically-induced climate change. This paleoclimatic data has important implications in furthering our understanding of how drastic alterations in ocean circulation could affect climate on a global scale.