Meet Kristin Poinar
I am a second-year grad student in glaciology, and I'm interested in how the Greenland and Antarctic ice sheets are responding to climate change. In Greenland, will the warming affect how quickly the slippery, melting ice sheet slides into the sea? In Antarctica, will the warming oceans shrink the ice shelves so much that they will stop propping up the huge amount of ice that's perched on the continent? I try to answer these questions on the computer, with numeric models.
Since the Greenland and Antarctic ice sheets are so different, I'm working on a separate modelling project for each of them. I'm grateful to the National Science Foundation for the Graduate Research Fellowship that gives me the freedom to do this.
How much will surface melt affect the motion of the entire Greenland ice sheet?
Recent observations of higher temperatures, increased surface melt, and accelerated outlet glacier flow strongly suggest that Greenland may contribute significantly and rapidly to sea level rise in the coming decades, in response to climate change. Catastrophic drainage events are occurring regularly, every summer, in the ablation zone. Pools of meltwater collect on the ice sheet, and the weight of the water eventually shatters the ice. The water flushes to the bottom of the ice sheet, lubricates the bed, and thus accelerates the ice flow locally. The photo of my adviser and his field team shows the aftermath of one of these lake drainage events - a moulin, essentially a 3000-foot waterfall beneath these researchers' feet.
In Greenland's warming climate, the spatial extent of these drainage events is expected to expand toward the interior of the ice sheet. Right now, the lakes are forming only in areas where the ice sheet's bottom is already melted. My concern is whether the lakes can, in the near future, reach areas where the ice sheet is frozen to the bed. A lake drainage here would change the basal velocity regime - these slow-moving, frozen areas would now slide much more quickly over a wet bed, permanently enhancing the ice sheet's contribution to sea level rise.
Greenland's basal temperatures and its temperate ice thickness have been modeled only coarsely (40km resolution) compared to the area of one drainage event (5km). I am modelling the ice sheet's basal temperatures and the thickness of temperate ice (ice that is at its melting point), which complicates the thermodynamics of the problem. My results will qualitatively predict the ice sheet's large-scale flow response, in the form of basal velocity regime changes, to the expansion of meltwater lakes into the interior of the Greenland ice sheet.
Josh Carmichael, another graduate student, is working on understanding just what happens under the ice sheet.
How are warming oceans affecting ice flow in West Antarctica?
After I finish my model for Greenland, I'll turn more attention toward the Amundsen Coast in West Antarctica, where six large glaciers have been accelerating at rather alarming rates. Since all glaciers over this large area are behaving similarly, it's thought that the ocean (which they all terminate into) is the cause. Each glacier here has an ice shelf which acts as an ice flow "cork" - just as a cork pushing against the sides of a bottleneck creates a strong plug, the ice shelf which is jammed into a large area of rugged coastline exerts a strong force against the glacier flowing into the ocean.
As the Southern Ocean warms, the size of the ice shelves decreases, and the corking mechanism weakens. Glaciologists are concerned that this could lead to a huge amount of ice being unleashed from the West Antarctic Ice Sheet, which would make for considerable sea level rise -- up to 8 feet if the entire Amundsen Coast region drained. For this project, I use finite element (three-dimensional) ice sheet models to understand how changes at the grounding line (ice shelves) are felt upstream. I force the models with large sets of data, such as surface velocity, and inferred quantities, such as temperature and basal shear stress.
I came to glaciology from Case Western Reserve University in Cleveland, Ohio, where I studied physics and English. In physics, I worked on the Cryogenic Dark Matter Search, an experiment that looks - and is still looking - for the invisible matter that makes up most of our universe. In English, I read a lot of books and was extremely happy. Clearly, I haven't always known I wanted to study glaciers.
At the University of Washington, I'm in the Department of Earth and Space Sciences. I'm also a member of the Program on Climate Change, a collection of graduate students and faculty that learn about the mess we humans have gotten ourselves into, what we can expect the earth to do in response, and how we might possibly begin to deal with it all.
For fun in Seattle, I run, ride my bike, swim, garden, throw pottery, read, and do jigsaw puzzles. With the exception of jigsaw puzzles, I am not very good at any of my hobbies.