Research

Andrew Jacobson and his research group specialize in radiogenic isotope geochemistry, aqueous geochemistry, and geomicrobiology. We combine fieldwork, laboratory experiments, and modeling to quantify chemical, physical, and biological phenomena that cycle elements and their isotopes at the Earth’s surface. Many activities use isotopes to probe the compositional evolution of the Earth, at timescales spanning the geological to modern-day. Others aim to elucidate the fundamental behavior of isotopes themselves, including their distribution, transport, and possible fractionation within and between Earth’s biogeochemical reservoirs. Of prime interest is isotopically tracking the flow, transformation, and distribution of carbon under conditions of natural and anthropogenic environmental change. We especially focus on mineral weathering and precipitation reactions that participate in the carbon cycle, link inorganic and organic aspects of the Earth system, and control the geochemistry of soils, streams, aquifers, and seawater.

Current projects:

1. •Studies focusing on the elemental and isotope (Ca, Sr, and C) geochemistry of Alaskan rivers and soils with the aim of developing new proxies for tracking Arctic climate change, permafrost stability, and organic carbon export at the watershed scale (Field site: North Slope, Alaska)
   

2. •Rates and mechanisms of microbially-mediated rock weathering and their implications for the chemical evolution of Earth’s atmosphere and hydrosphere
   

3. •Ca and Mg isotope fractionation during calcite precipitation, ion-exchange, and microbial uptake
   

4. •Application of stable and radiogenic isotope tracers (Mg, Ca, Sr, and U-Th) to the study of water-rock interactions in aquifers (Field sites: Madison Aquifer, South Dakota; Wyodak-Anderson Coal Bed Aquifer, Wyoming)
   

5. •Relationship between mountain uplift, chemical weathering, and the long-term carbon cycle (Field sites: Himalaya Mountains; New Zealand Southern Alps)
   

6. •Atmospheric supply of P to seawater via dust deposition and its implications for marine productivity and paleoproductivity estimates
   

7. •Role of calcite dust in the isotopic budgets of Sr and Nd in seawater
   

Available Positions:

Ph.D. Research Opportunity in Arctic Climate Change