In the News
- Giant Snails’ Century-Old Shells Recorded Monsoon Rainfall - Eos, American Geophysical Union
- Improving Our Understanding of El Niño in a Warm Climate - Eos, American Geophysical Union
- Trace metals and thrash metal with Kaustubh Thirumalai - Forecast (Podcast); Michael White, Nature
- Climate change causes killer heatwaves - Climate News Network
- Scientists just linked another record-breaking weather event to climate change - The Washington Post
- South-east Asia smashes temperature records for its hottest month - International Business Times
- Scientists Unravel How El Niño and Global Warming Combine to Cause Record-Breaking Heat in Southeast Asia - University of Texas at Austin
- Bat Guano: A Possible New Source for Paleoclimate Reconstructions - Eos, American Geophysical Union
- Climate scientists trained to be on hot seat - Minnesota Public Radio
- Climate Change: The Beginning - Generation Anthropocene (Podcast); Stanford University
- Man-made warming may have started decades earlier - CBS News
- Tapping Coral for Evidence of Earthquakes - University of Texas at Austin
- Oceans warming 20x faster than they cooled in past millennium - University of Maryland
- 1.8kyr Cooling Trend Results from a Series of Volcanic Eruptions - Nature World News
- Coral Reefs and Earthquake History: Tale is There - Nature World News
- Catch a Falling Sediment - The University of Texas at Austin
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.
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.
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.
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.
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.