Technical Description This grant will support the use of the δDwax proxy as a stratigraphic guide and as an indicator of past changes in aridity for sediments from the recently-drilled Dead Sea Deep Drilling Project (DSDDP). The results will be used to refine the core stratigraphy, which must be achieved before further analyses are conducted. The project will produce a preliminary 200ka δDwax record from the Dead Sea DSDDP core that will provide critical stratigraphic control on the DSDDP core, aiding the interpretation of major climatic events such as the desiccation of the Dead Sea during the last interglacial period, and insights into changes in past aridity in the Levant region, including the state of hydroclimate during glacial periods, around which there is much debate. The stratigraphic utility of δDwax derives from its clear ability to track Marine Isotope Stages, enabling relative comparisons between δDwax and other proxies in the core that can be interpreted in the context of global marine isotope stratigraphy. The development of these δDwax data will play a critical role in the international progress of the DSDDP project as the dating results will allow other proxies and core description work to be put into temporal context.
Non-Technical Description This research will investigate the apparent discordance between results from local cave stalagmites, which indicate long droughts during the last glacial cycle (approx. 100,000 years) and the apparent intermittent high levels of the Dead Sea during this time (known to scientists as the much larger Lake Lisan, which was ~250m deeper, and extended all the way North to the Sea of Galilee/Lake Tiberias, and South to 150km beyond the current shoreline).
The research will support an early career researcher, a technician, and an undergraduate intern recruited through the Northeastern University cooperative education program. The PI will also facilitate local outreach efforts by hosting motivated high school students in her lab through the Falmouth Academy Internship program, an ongoing collaboration between Falmouth Academy and WHOI. These students will participate in aspects of the Dead Sea project and learn about the effects of climate change on the Levant region. International collaboration with colleagues from Germany, Israel and Japan will be facilitated.
The Levant region in the Middle East is a very dry region that may become drier under anthropogenic climate change. However, some of the fundamental ways in which Levant climate and environment respond to changes in global temperatures are still not completely understood. Paleoclimate research - the study of past climate change - is the key to understanding how climate in this geopolitically-important region varies and how it might respond to future climate change. In 2011, the Dead Sea Deep Drilling Project, funded by the National Science Foundation and Israel National Science Foundation, collected the longest sediment core from the Dead Sea to date. This exceptional core is half a kilometer long, and contains information about Dead Sea climate and environment going back 200,000 years. One of the exciting preliminary findings was the presence of a pebble layer, dating to about 110,000 years ago. This suggests that at that time, the shore of the Dead Sea was near the coring site, 300 meters below the current lakewater surface and 730 meters below sea level. The climate must have been very dry at that time to cause this remarkable dry down. This particular NSF project, "RAPID: Analyzing dDwax in the Dead Sea DSDDP Core as an Indicator of Aridity and a Stratigraphic Aid", was designed to very quickly analyze the sediment from the Dead Sea for a relatively novel indicator - the deuterium/hydrogen content of leaf waxes (dDwax) - and gain new insights into past aridity in the region. The dD of leaf waxes records the dD of rainfall in the region, which is controlled by the amount of rain. Hence, dDwax is a good indicator for aridity. In addition, the isotopes of rainfall on long timescales track large changes in global climate. This is because when glaciers grew during past ice ages, they locked proportionally more of the lighter water isotopes (normal hydrogen and oxygen-16) into the ice, leaving the ocean (and rainfall that ultimately comes from the ocean) relatively enriched in the heavier isotopes (deuterium and oxygen-18). This causes all past isotopic records to vary in accordance with the ice ages. These global changes give us a way to correlate climate events across different locations on Earth. dDwax therefore allows us to compare the timing of climate events in the Dead Sea to the rest of the world, and generally improve the stratigraphy - the correlation of sedimentary events to known events in time - of the DSDDP core. Due to the importance of this measurement and the fact that these data will be used by multinational team of researchers studying the new core, they needed to be done relatively quickly and early on in the development of the DSDDP project. Hence, this project commenced in early 2014 and lasted for only a year. This project was highly successful. The data generated did, as expected, improve the dating of the Dead Sea core. We were able to determine, for example, that the emergence of the shoreline and the accompanying hiatus in sedimentation lasted no longer than 8,000 years. We also saw very large changes in dDwax, indicating big shifts in the hydroclimate of the Levant region during the last 200,000 years. We will build upon this initial work in the future in order to better understand what causes these large changes, how they are related to global changes in temperature, and what these past changes reveal about future climate change in the Levant region.
