Glaciers and ice sheets play key roles in the long story of Earth’s climate and landscapes.
Today, changes in the cryosphere also impact society on local and global scales. These changes ultimately depend on how climate variations are filtered through ice dynamics. My research focuses on these interactions. I use computational models, theoretical models, and data analysis to investigate how glaciers and ice sheets respond to climate forcing and other environmental changes. My goal is to improve how we account for ice dynamics and climate variability when interpreting observed glacier changes, or when calibrating models for projections into the future.
Check out some specific research areas below:
Ice sheets and outlet glaciers
The massive glaciers draining the Greenland and Antarctic Ice sheets are sensitive to both atmospheric and oceanic changes, with dynamics operating on many timescales. Ice flow is also highly sensitive to geometry and properties of the subglacial landscape. Much of my research attempts to untangle these climatic, topographic, and dynamical factors using model experiments.
For example:
How do fast and slow ice dynamics compare for changes driven by the ocean vs. the atmosphere? (paper)
How can we quantify anthropogenic effects vs. natural variability in driving rapid and/or unstable glacier retreats? (paper)
Under what conditions does sediment deposition help stabilize ice streams? (paper coming soon)
Mountain glacier dynamics
Mountain glaciers are simpler than marine-terminating outlet glaciers, but there are thousands of them, spanning a huge range of geometries and climate settings around the world. So, it’s important to understand how basic principles translate from one setting to another.
One such principle is a glacier’s response time, which governs how fast it adjusts to climate variations. Typical response times (10—100 years) mean that glaciers are lagging recent climate change and are therefore out of equilibrium. Unfortunately this means additional “committed” ice loss already baked in to current warming levels. This is a consequence of basic glacier dynamics (paper here). However, glaciers with different geometries have different response times, so the disequilibrium may vary widely. A case study on the Washington Cascades explores differences in the dynamic state of glaciers throughout a region, simply due to their different shapes and sizes (paper here).
Climate variability and glacier mass balance
Glaciers depend on a balance between winter snowfall and summer melt to maintain an equilibrium. Warming temperatures shift this balance, but year-to-year variability obscures trends on multi-decade timescales. However, we can use climate data to trace the origins of this short-term variability in atmospheric and ocean fluctuations. This helps to clarify the long term trends, and can also inform the regional picture of mass-balance changes.
Here’s one paper on North American glaciers, and another (led by Dave Bonan) on glaciers in Scandinavia.
Radioglaciology
Radar is a powerful tool for observing the structure and evolution of glaciers and ice sheets. I’ve joined several field expeditions, from the North Cascades to Antarctica, with colleagues from UW and also USGS. We’ve used radar to measure ice velocity and snow accumulation in the Washington Cascades. Additionally, I went to Hercules Dome, Antarctica to help with radar surveys of the subglacial topography and internal ice layers. These help us understand past states of the ice sheet, and will help inform a future ice core drilled at this site.