Ice sheet stability in a warming world, East Antarctica
How will the massive East Antarctic Ice Sheet (EAIS) respond to continued warming of the climate system? Will it collapse into the ocean, raising sea level by as much as 55 m globally, or will it prove impervious to warming on the scale anticipated for the coming centuries? Perhaps the ice sheet might even grow as snowfall increases. Each of these is a fascinating and pertinent hypothesis, yet difficult to test in the absence of robust geologic data, from Antarctica itself, to show how the EAIS behaved during previous periods of warmer-than-present climate. Our goal is to provide those data.
The 'How' and 'Why' of climate change, including its impact on society, landscapes, and ecosystems, are the broad foci of my research interests. Of particular concern to me are the tropics, which are both the central heating system of Earth's climate and home to the majority of all life. The tropics play a key role in ice ages and the global transmission of abrupt climate signals. Thus, deciphering both the timing and true nature of past events at low latitudes is fundamental to our understanding of the role of the tropics in climate. At the other end of the latitudinal scale, I'm also embroiled in establishing the response of Antarctica's ice sheets to warmer-than-present climate. The East Antarctic Ice Sheet, for example, is the largest chunk of ice on the planet, with the potential to raise sea level by at least 50 metres. Yet current projections for its evolution in a greenhouse world - and what this means for sea level - are highly disparate, ranging from collapse to growth (and everything in between). My role in this debate is to provide real, geologic data from the continent itself. Finally, my work in the boreal mid latitudes involves reconstructing the terrestrial impact of abrupt climate change events (e.g., Heinrich stadials) in the North Atlantic Basin. After all, only once we have established when and how such events occurred will we be able to say why the climate system behaves in this way.
Much of my work involves glacial geology, cosmogenic surface-exposure dating, snowline reconstruction, and palaeoecologic proxies. I rely heavily on field work and data collection in some of the world's most spectacular environments, and I'm always happy to hear from prospective students whose interests overlap with my own. So, if you are considering graduate school and are serious about field-based geology, don't hesitate to get in touch.
Testing the role of CO2 in the last glacial termination, Andes
We know carbon dioxide is a greenhouse gas, but projecting the impact of anthropogenic CO2 on future climate is complicated by uncertainties surrounding climate sensitivity. To help address those uncertainties, we are comparing the geologic record of tropical temperature change to high-resolution CO2 data from the new West Antarctic ice core to assess the relationship between the two. Our focus is the last glacial-interglacial transition (or 'termination'), as this was the highest-magnitude natural global warming of the last 100,000 years. And our laboratory for this investigation is the tropics, where glaciers clinging to the highest peaks of Colombia and Peru serve as exquisite palaeothermometers taking the temperature of the tropical troposphere. After all, as the tropics go so goes the world.
Blowing Hot or Cold? Assessing the terrestrial impact of North Atlantic stadials and abrupt climate change
What drives abrupt climate change? With continued population growth, increasing pressure on natural resources, and rising CO2 concentrations, understanding the causes and effects of abrupt climate change poses one of the greatest challenges to 21st Century climatology. Thus developing our knowledge of past perturbations is key to minimising the risk of future 'climate shock'. This project, which began in 2010, utilises a geologic approach to resolve the terrestrial expression of past abrupt climate change in the North Atlantic region, which is widely held as a central player – if not the driver – of abrupt change, to help identify the mechanisms driving these potentially catastrophic phenomena. Of particular interest are Heinrich stadials 1 and 0, and the abrupt transitions associated with them.
Fire and Ice in the Central Volcanic Zone
Causative links between deglaciation and magmatism have long been hypothesised and, along divergent plate boundaries (i.e., Iceland), quantified to varying degrees. But what happens along convergent margins when large amounts of ice are suddenly removed from atop volcanoes? What is the effect of such unloading on magma chamber evolution? Quite simply, we don't know, yet the question is increasingly important as our planet warms and the glaciers and ice caps mantling active and dormant volcanoes worldwide continue to shrink. This new investigation combines geomorphology and geochemistry to explore the impact of rapid deglaciation on the internal workings of volcanic systems in the Pacific Ring of Fire.