Argemino Barro, a New York-based journalist, interviewed Kristin Poinar for El Ágora, the first Spanish-speaking media entirely devoted to water and climate change. His article is about the future of the Greenland Ice Sheet.
We had our first and only in-person lab meeting of Spring 2021. It was a brisk spring day on UB’s South Campus, where none of us had ever spent much time. We took a walk around and even spied the Mackay Tower, where a pair of peregrine falcons make their nest. (UB has a webcam — UB Falcon Cam — highly recommended viewing in April through the end of May.)
Jeremy Stock gave a short talk at the Buffalo Association of Professional Geologists, as part of a Scholarship Event, in spring 2020. The BAPG was prescient and kind enough to share the presentations on the web. Take it away, Jeremy!
Jeremy Stock successfully defended his MS thesis, “Modeled Patterns of Crevassing Induced by Supraglacial Lake Drainage in Western Greenland”, and turned in a very nice dissertation this May. Congratulations, Jeremy!
The Greenland Ice Sheet is expected to contribute substantially to global sea level rise over the next century in response to climate change. As increasing volumes of surface meltwater are delivered to the glacier bed via moulins during supraglacial lake drainage events, it has been hypothesized that new crevasses may form upflow, causing a cascade of lake drainages. This upflow expansion could alter ice sheet dynamics, leading to ice sheet instability and even greater sea level rise contributions. To investigate this hypothesis, we applied an analytical ice-flow model (Gudmundsson, 2008) to calculate surface strain rates and infer the pattern of crevassing induced by a modeled rapidly drained lake. We calibrate the model using data collected during a lake drainage event in the summer of 2011 in the Pakitsoq region of Western Greenland. The patterns and extent of crevassing we see in our model results are highly dependent on the bed topography, basal sliding ratio, dimensions of the slipperiness patch, and the seasonal timing of the drainage event. Our model results show evidence of considerable crevassing occurring within 3-5.5 km upstream of the modeled lake drainage, with crevassing enhanced by a factor of 5-6 within a 3 km radius of the rapidly drained lake. Because lakes in this area are spaced by roughly 2-4 km, our results support the hypothesis for cascading lake drainage. This research improves our understanding of how meltwater may affect ice sheet dynamics, which are a major factor in how much the Greenland Ice Sheet will contribute to sea level rise in the future.
G. H. Gudmundsson. Analytical solutions for the surface response to small amplitude perturbations in boundary data in the shallow-ice-stream approximation. The Cryosphere, 2(2):77–93, 2008. http://doi.org/10.5194/tc-2-77-2008
Modeled Patterns of Crevassing Induced by Supraglacial Lake Drainage in Western Greenland
A few figure excerpts:
“Meltwater On, In, & Under the Greenland Ice Sheet”
I was fortunate to be invited to give a public lecture at the Carnegie Science Institute in Washington, DC as part of their Carnegie Capital Science evening lecture series. It was a fantastic experience!
Each summer, a volume of water equivalent to 10 Chesapeake Bays melts off of the Greenland Ice Sheet. Much of this meltwater reaches the ocean, but its path is neither direct nor simple. On its way, the meltwater interacts with the glacier itself in ways that can affect ice flow and further sea-level rise. Dr. Poinar uses numeric models and remotesensing observations to understand the water-ice interactions that affect the glacier’s long-term behavior. She will discuss her analyses of water systems — including large meltwater lakes and rivers that form on top of the ice, aquifers within the ice, deep crevasses that move water from these systems through the glacier to its base, and the water flow networks that develop under the glacier — that change the flow speed and patterns of the ice on its slow, or sometimes not-so-slow, journey to the ocean. Ultimately, Dr. Poinar wants to discover: how much is the Greenland Ice Sheet likely to raise sea levels and how fast will it happen?
A top-notch video recording of the lecture is available at https://carnegiescience.edu/greenland.
Though the total carbon content of the mantle is largely unknown, the isotopic signatures of its sources and sinks suggests much about how the mantle operates. Together, geochemical and mineralogical analyses of a new diamond, a compendium of studies of the magnitude of carbon fluxes into and out of the mantle, and a simple geophysical model suggest that the mantle acts as two interacting reservoirs of carbon: (1) subducting slabs (the reservoir for depleted carbon) descend deep into (2) the bulk mantle (the enriched-carbon reservoir) to possibly as deep as the core-mantle boundary. These reservoirs mix to a small degree; that degree is a function of the isotopic composition of the bulk mantle (δ13C from -8 to -3.5 parts per thousand) and the residence time of carbon in the mantle (1-10 Gyr). The residence time is a function of the net flux out of the mantle, which is itself a sum of seafloor spreading rates, oceanic sediment deposition rates, calcium carbonate precipitation rates, and arc volcanism fluxes. This paper summarizes many studies of these fluxes to estimate those above quantities relevant to mantle convection.
We visited the Eternal Flame, a methane seep at a local waterfall, on a beautiful fall Saturday. Eternal Flame Falls is a short hike from a huge parking lot at Chestnut Ridge County Park, outside Buffalo. We also explored the rest of the park on our hike and met a local mushroom photography expert on the trail!
This month, I had the pleasure to be a guest at Canisius Conservation Conversations, a student-produced podcast at the Institute for the Study of Human-Animal Relations at Canisius College, Buffalo. It was a great experience!
I like the paper “Distortion of isochronous layers in ice revealed by ground-penetrating radar” by Vaughan, Corr, Doake, and Waddington (1999), Nature, 398(6725), 323–326, doi:10.1038/18653. The paper describes the field discovery of a Raymond Bump. The online Supplement, however, is not so good. (Thanks, Nature.) I wanted to be able to read it without squinting and scratching my head, so I rewrote it. Maybe it will prove useful to someone out there at some time. See link at end of page.
If you don’t know what a Raymond Bump is, you should learn about it from Jesse Johnson’s page.
And finally… the Supplement of Vaughan et al. (1999)… rewritten!