Climate & Earth Surface Geochemistry Group
Lamont-Doherty Earth Observatory
Columbia University
The goal of our research is to provide a mechanistic understanding of the processes that shape Earth surface geochemistry in the modern, so that we can accurately interpret past records. We focus on dust, seawater, marine sediments, and modern and ancient rocks.
We are interested in answering questions such as: How much dust is transported to an ecosystem, and how does it influence the biogeochemical cycling in this location? Can variations in the composition and size of dust preserved in ice cores inform us about changes in regional climate or ice sheet extent? How does sediment sourced from retreating glaciers and permafrost degradation affect nutrient fluxes to downstream environments? Does human activity (climate and land use changes) influence the composition of metals transported to the environment?
To answer these questions, we utilize an array of geochemical and isotopic techniques along with physical measurements to inform us on the sources, sinks, formation mechanisms, nutrient content, and biogeochemical cycling of Earth surface materials. We conduct a significant amount of fieldwork depending on the project, ranging from the mountains of Southern California to Antarctica. Our work requires clean lab chemistry and isotope analysis on a variety of mass spectrometers.
Variations in dust flux and sources to polar ice sheets across glacial–interglacial cycles are tied to temperature and atmospheric circulation. The geochemistry of dust preserved in ice records aridity, land surface conditions, and prevailing wind directions. Using ice core records from the margins of the Antarctic ice sheet, we analyze dust physically and geochemically to probe regional climate during major climate transitions. We ask whether changes in dust provenance can reveal past ice sheet extent, and what role dust played in marine productivity and the carbon cycle during Earth's major climate shifts.
Glaciers in alpine and sub-Arctic regions are retreating at alarming rates due to climate change. Their outwash plains are important sources of fine-grained sediment and dust, which can influence primary productivity on land and in the ocean. We study how key nutrients behave as this sediment is transported by rivers and wind, in order to understand how biogeochemical cycling in polar regions will respond to future climate change.
Isotopes of metals such as zirconium (Zr) and titanium (Ti) are emerging tools for tracing processes from Earth's earliest crust to the modern and ancient oceans. In seawater, we measure dissolved and particulate Zr isotopes through the water column to investigate their utility as tracers of marine particle scavenging and water mass movement. Titanium isotopes fractionate distinctively for rocks formed in plume versus subduction settings, and we leveraged this observation to infer the magmatic settings of Earth’s oldest known rocks from the Acasta Gneiss Complex located in the Slave craton of northwest Canada.