Plio-Pleistocene history of the Antarctic ice sheets

Due to current climate trends and the high probability that average global temperatures will continue to rise, it is of scientific and societal importance to understand how ice sheets have responded to climate change in the past.  Among extant ice sheets, the Greenland and West Antarctic ice sheets are considered the most sensitive to atmospheric warming.  Debate surrounds the sensitivity of the larger East Antarctic Ice Sheet (EAIS), which likely exhibits complex and spatially non-uniform response to climate warming; some areas might exhibit melting and recession whereas others experience ice growth via increase snowfall.  To understand better the potential complex response of the EAIS, numerous glacial records are required from the ice sheet periphery.  Moraines from outlet glaciers that pass across the Transantarctic Mountains (TAM) are particularly important as they reflect both regional-scale fluctuations as well as coeval changes in the level of the interior EAIS.

My research has focused on documenting Plio-Pleistocene changes in outlet glaciers that drain Taylor Dome on the periphery of the East Antarctic Ice Sheet (EAIS). Chronologic control comes from 3He and 21Ne cosmogenic-nuclide analyses of boulders sampled from drifts and moraines deposited by these outlet glaciers in the Quartermain and Wilkness Mountains.  In an article in review, I (along with co-authors) present a sequence of eight moraines that span the last 3.1 Myr and call for stepped ice recession since a local highstand during the mid-Pliocene.

Cold-desert weathering processes

Cosmogenic exposure ages of surface boulders in the McMurdo Dry Valleys are some of the oldest in the world.  Geomorphologists use cosmogenic nuclides to quantify both maximum erosion rates and to date surface deposits (such as moraines).  Some of the slowest erosion rates ever recorded are found in the ice-free regions of Antarctica.  An important aspect of my of my ongoing research is to study cold-desert weathering processes and quantify erosion rates in the McMurdo Dry Valleys. To this end we are coupling cosmogenic-nuclide techniques with in-situ field experiments designed to quantify present-day rates of 1) thermal fracture, 2) frost wedging, 3) wind abrasion and 4) salt weathering (pit formation).

Climate in the McMurdo sound region and cosmogenic exposure dating

We propose to investigate the impact of earth surface processes on the application of cosmogenic exposure dating in Antarctica by combining cutting-edge multi-nuclide techniques (3He, 10Be, 14C, 26Al, 36Cl and 53Mn), detailed field experiments, rock-mechanic studies, and climate modeling.  We propose to analyze cosmogenic-nuclide inventories for a suite of six alpine-moraine systems in the inland, high-elevation region of the McMurdo Dry Valleys.  Our proposed work thus has two specific goals:

1)To evaluate the effects of episodic (e.g., non-uniform) geomorphic events in modulating cosmogenic inventories in surface rocks in polar deserts and

2) To generate an alpine glacier chronology that will serve as a robust record of regional climate variation over the last several million years.

For the former, we will use a combined multi-nuclide and field-based approach to quantify better the role of nuclide inheritance, complex burial histories, and non-uniform erosion processes (such as episodic thermal fracture) in modulating cosmogenic inventories.   A key objective is to produce a unique sampling strategy that yields consistent exposure-age results by minimizing the effects of episodic geomorphic events that obfuscate cosmogenic-nuclide chronologies.  For the second goal, we will link our new moraine chronology with regional-scale atmospheric models developed by our collaborators at University of Massachusetts Amherst. Model output will report local temperature and precipitation during “times of interest” (e.g., moraine formation).

Buried glacier ice: role in permafrost processes and potential climate archive

Buried ice is ubiquitous across polar and alpine regions and represents an important (and often overlooked) source of environmental information. Comprising ancient glacial ice preserved under a protective layer of sediments, as well as segregation ice formed by the refreezing of groundwater, buried ice deposits contain a record of past hydrologic, climatic, and glaciologic conditions.  Buried glacial ice, specifically, represents a new and potentially far-reaching archive of atmosphere on Earth that could extend as far back as the late Miocene in the hyper-arid, cold highland regions of Antarctica.  In addition, buried ice deposits in Antarctica are potential analogs for similar deposits on Mars, where recent ground and satellite investigations have demonstrated the presence of near-surface water-ice.

My studies of buried ice deposits in Antarctica have focused on investigating the age, origin and modification of buried glacier ice by integrating stable isotopic, meteorologic, sedimentologic, and shallow seismic data.  In a recent article published in Geomorphology, I (along with co-authors) demonstrated that ice-cored lobes alongside extant alpine glaciers contain ~130,000-year-old glacial ice, associated with a glacial advance during MIS 5.5. In addition, I have been involved in studying the modification of multi-million-year-old glacier ice in the high-elevation mountains of Antarctica, as part of a long-term project aimed at ice-core drilling and geomorphic-process modeling.