My research focuses on global climate change and the use of isotope geochemistry to understand climatic and atmospheric processes. I am interested in the parameters and mechanisms that control paleotemperature proxies; in particuler, my group develops and uses the novel proxy carbonate clumped isotopes. We examine biological parameters that affect clumped isotopes and develop its use in new archive materials; we study the effect of non equilibrium processes on clumped isotopes and oxygen isotopes. We apply clumped isotpes to reconstruct paleotemperature and paleo-rainfall in different time periods during the Cenzoic. I am also interested in the use of isotopes to understand the modern carbon cycle and the effect of the biosphere of atmospheric chemistry.
What is clumped isotopes geochemistry?
Analysis of an isotopic composition is a measurement of the relative abundance of a heavy, rare, isotope within a group of molecules. The term ‘clumped isotopes’ refers to the natural abundance of molecules containing two heavy isotopes, such as 13C18O16O, and is a measure of the preference of two heavy isotopes to clump together into a chemical bond. This preference is temperature dependent with the isotopes distributed randomly among all molecules at very high temperatures and are clustered together into a more ordered system at low temperatures.
This results in an isotopic parameter, ∆47, that can record the temperature in which these bonds were formed. ‘Clumped isotopes’ measurements are currently applied for 13C-18O bonds in CO2 molecules that are extracted either from carbonate minerals or from the atmosphere. In carbonates ‘clumped isotopes’ are used to determine the formation temperature of the mineral with most applications associated with reconstruction of past climatic conditions. In atmospheric CO2 it is used as a tracer for partitioning and quantifying the different CO2 sources and sinks of the global carbon cycle.
Climate Change affects the terrestrial biosphere, while changes in the biosphere feedback and affect the climate system. Understanding these complex interactions is important at these times of Global Change.
Related research in our lab track the respiration in soils, and the internal CO2 movement and recycling within forest trees. In addition, we explore the engagement of the Alternative Oxidase in natural ecosystems. These research directions are based on high accuracy measurements of O2 concentrations and stable isotopes.
Other research projects focus on developing the use of oxygen stable isotopes of phosphate for tracking phosphorus in dust and its biogeochemical cycling in soil. This research is based on field work, remote-sensing and lab work. These approaches could help evaluate the effects of changing climate on the terrestrial phosphorus cycle, which is an important limiting factor for plant growth.
Finally, lately we have developed in collaboration with Prof. Amrani, from my institute, an approach to measure the sulfur isotopes of carbonyl sulfide (COS) and used this to determine its isotopic composition in the atmosphere in plant uptake, and in seawater. Our continued research in this field will help to better constrain global scale photosynthesis
My research has been focused on geochemical and biogeochemical processes at and near natural interfaces such as between water (saline/fresh) and rocks (or sediments or particles) and water-atmosphere boundaries. The research covers a wide-scale variety of geological environments. I have studied fluid inclusions within crystals, microgradients between seawater and electrode surfaces, stromatolites (microbial mats), coral reefs, porewaters within corals and sediments, floods and the open sea water column. A brief description of the research activities:Sr isotopes in ground waters as tracers of the calcite-calcite and calcite-dolomite transformations; Fluid inclusions in halite and the reconstruction of the chemical evolution of the oceans during the geological history; Diagenesis of reef corals and the distribution of trace elements (proxies for paleo-oceanographic conditions) between coralline aragonite and seawater; The fate of manganese in the soil-aquifer treatment of a sewage reclamation system; Isotopic effect of CO2 influx across brine-atmosphere interface induced by intense photosynthesis; 14C fluxes into marine sediments, across freshwater seawater interface, flood water and radiocarbon budgets; Carbon, oxygen and nutrients variations in coral reefs emphasizing the role of bioeroders, the decrease in reef calcification due to eutrophication, and suggesting that reefs will stop to grow on atmospheric CO2 doubling; Nutrients budget of the northern Gulf of Aqaba, Red Sea that enable to determine the role of fish farming in the eutrophication of that oligotrophic basin; Using the disequilibrium in the U-Th series, the cosmogenic isotopes 14C and 10Be for identifying atmospheric exchange, flood intensity, fluxes into porewater and water dating and analyzing the open system effect on dating corals by the U-Th method and studying water fluxes and adsorption/desorption kinetics. 4)
As a marine biogeochemist, my interest revolves around the interactions between organisms and their environment, with emphasis on trace metal bioavailability to phytoplankton and redox transformations. I am intrigued by the fact that microorganisms, striving to acquire nutrients and protect themselves from external stressors, actively modify their chemical milieu and in turn influence the biogeochemical cycles of trace and major elements in the ocean. I study fundamental processes and mechanisms by combining field and laboratory measurements and experiments.
Ongoing and future projects:
Dust as a source of iron to Trichodesmium, a globally significant phytoplankton