In the News


Research Interests

Paleoclimatology and Paleoceanography

My research develops records of temperature and salinity variations in the ocean using chemical signatures locked in the shells of plankton known as foraminifera. Changes in the trace metal and stable isotope composition of foraminiferal shells are powerful tools to reconstruct past climatic and oceanic parameters on a multitude of timescales, depending on the marine sediments in which they are preserved. These records can reveal important information about ocean-atmosphere processes operating on periods beyond instrument-based observations and can help us fundamentally advance knowledge about the climate system. Currently, I am investigating climate variability during the Holocene and the last Ice Age by applying these geochemical tools in marine sediments from the Gulf of Mexico, Bay of Bengal, and equatorial Indian Ocean.

Sediment cores from the Bay of Bengal. This photo depicts an ash layer.

Sediment cores from the Bay of Bengal. This photo depicts an ash layer.

Hunting for corals and caves in the Solomon Islands.

Hunting for corals and caves in the Solomon Islands.

My work also focuses on building records of past climate variability using geochemistry preserved in corals and speleothems (cave deposits). Stalagmites are excellent recorders of the stable isotopic composition of precipitation and are valuable sources of information about past rainfall (or the lack of it). Corals, due to their relatively fast growth rate, can be used to reconstruct year-to-year surface-ocean variability and yield important constraints on climatic processes such as the El Niño Southern Oscillation (ENSO). I am working with stalagmites from India to investigate the history of the Indian monsoon and with corals from the southwest Pacific to understand past changes in the ENSO system.

The increasingly creeping influence of long-term warming on April heat extremes in Southeast Asia: figure from a recently published article in Nature Communications.

The increasingly creeping influence of long-term warming on April heat extremes in Southeast Asia: figure from a recently published article in Nature Communications.

Climate Change, Extremes, and Attribution

With rising levels of greenhouse gases, it is becoming increasingly clear that human activity is inducing more and more climatic extremes. A significant part of my research involves disentangling natural climate variability and long-term warming to study climatic extremes that are occurring all over the planet right now. A recent publication resulting from our work details 2016's episode of temperature extremes in Southeast Asia and attempts to quantify the contribution from 2015's El Niño versus long-term, anthropogenic warming. I am interested in applying statistical techniques on observations and climate model output to understand the exacerbation of impacts caused by natural climate variability due to global warming in the past, present, and future. 

Modeling Proxies

Foraminiferal shells from sediments beneath the Gulf of Mexico seafllor.

Foraminiferal shells from sediments beneath the Gulf of Mexico seafllor.

I am interested in statistically quantifying and modeling uncertainties in proxies. How can we best listen to what the proxies (foraminifera, corals, speleothems etc.) are telling us? I am interested in forward-modeling proxy data using instrumental data and using the results as a metric to compare paleoclimate output from general circulation models which are used to simulate global climate. How important are these proxy uncertainties for model-data comparisons? To understand the modern ecology of planktic foraminifera, in collaboration with with the USGS, I use a sediment trap in the Gulf of Mexico. This instrument collects plankton shells before they are deposited on the seafloor. Using these samples, we can calibrate the chemistry of the shells to temperature and salinity. Ultimately, the sediment trap provides better estimates for our downcore geochemical measurements. 

A schematic of a sediment trap.

A schematic of a sediment trap.

Collecting corals on Ranongga, western Solomon Islands

Collecting corals on Ranongga, western Solomon Islands

Paleogeodesy

Another line of research I am involved with is coral paleogeodesy, in collaboration with Fred Taylor. At island arcs where two plates converge at a subduction zone, earthquakes are abundant and cause uplift and subsidence. Corals, which are extremely sensitive to sea-level can be killed due to abrupt uplift and become part of the island. We can use the elevations of precisely-dated fossil corals on islands to understand earthquake history. Currently I work on corals from the western Solomon Islands.