Research
The Earth system is a complex and coupled energetic engine.
Understanding that system requires understanding the dynamics and interactions of its constituents: the atmosphere, oceans, land, and cryosphere.
I aim to understand the mechanisms by which Earth’s climate system evolves through time. This understanding will be built on the compilation and objective analysis of diverse geochemical records of past climate, and careful synthesis with climate-system modeling.
Research Interests
Geochemistry
My interest in geochemical systems is primarily through the lens of environmental proxies and understanding how the Earth’s climate is imprinted upon natural archives. Ive worked extensively on ice core records, stable isotope ratios of water in particular, making laboratory and in-the-field measurements, as well as developing numerical models to aid interpretation.
Paleoclimate
The value of paleoclimatology is two-fold. First, we can uncover the unique history of the Earth’s climate system. Second, we can illuminate the processes by which the Earth system operates. The array of climate states that have occurred in the past provide important out-of-sample cases through which to test basic theories in climate dynamics.
Climate Dynamics
While my interests are broad, two questions stand out to me as critical to understanding the Earth’s past and future. First, how do coupled interactions between components of the climate system drive internal variability, particularly on long timescales? Second, what are the fundamental processes driving polar amplification?
Some Recent Projects
What controls dust in the high latitudes?
The amount of dust landing on the polar ice sheets changed by orders of magnitude over glacial cycles. Why?
It has long been thought that changes in aerosol source strength are the primary driver. I don’t think that is right. I think changes in the hydrological cycle dominate variability in dust, and other aerosols like sea salt, over a range of time scales.
Atmospheric teleconnections during DO events.
A series of abrupt Northern Hemisphere warming events punctuated the climate of the last glacial period. By reinterpreting the deuterium-excess water isotope parameter in Antarctic ice cores, I found evidence for shifts in the southern westerly winds, near synchronous with the abrupt warming events on the other side of the globe. Both atmospheric and oceanic teleconnections link the high and low latitudes during abrupt climate change in the past.
In a subsequent, related study, lead by Christo Buizert, we showed that these wind-driven changes can be seen all around Antarctica. (This study showed a few other neat things too! You should read it.)
What controls inter-annual to decadal variability in the high latitudes?
This was an awesome study, lead by Tyler Jones at CU Boulder, that I was pleased to be a part of. Using a ridiculously high resolution water isotope record form WAIS Divide (sub annual for tens of thousands of years!) we investigate how inter-annual and decadal variability changes during the transition out of the last ice age. We find that all variability was something like 30% higher during the ice age, but that inter-annual variability (e.g. that associated with things like ENSO) was even stronger, doubled in fact! Why was this? Based on some GCM modeling, we think it was due to the presence of the Laurentide Ice Sheet in the opposite hemisphere, which alters the strength of the teleconnection between the tropics and the high-latitude Southern Hemisphere. I know, it’s wild!
Plus my photo made the cover!
