Please join BAPG'S virtual student scholarship event and allow us to introduce you to our presenters! It's out membership that allows us to hold this event each year and we thank you for your continued support. This event is free and will be held virtually, but please consider registering with a donation if you're able to help support the scholarship fund for this event or become a BAPG sponsor.
Presenters: Will Russo (UB) and Eric Cicero (UB)
Will's Presentation Description
"Application of three-dimensional basis-constrained electrical resistivity tomography to visualize field-scale saline tracer."
Accurate imaging of groundwater contaminant plumes is necessary for environmental remediation efforts as well as protecting the public from contamination. Conventional direct sampling methods for tracking contaminant plumes involve drilling wells and sampling the groundwater for contamination. While direct sampling methods provide ground-truth concentration data at specific well locations, the data are spatially limited resulting in incomplete understanding of plume extent. Direct sampling methods are also invasive and can be cost prohibitive. To obtain spatially continuous data, we interpolate data from dense network of wells, which tends to disturb the very system we seek to investigate and poses contaminant mobilization risk. In contrast, indirect geophysical methods, such as electrical resistivity tomography (ERT) provide inexpensive spatially continuous data in a non-invasive manner.
Due to limited and noisy data, the reconstruction of contaminant plumes from ERT data requires prior constraints to stabilize the solution. The traditional Tikhonov inversion method has been shown from tracer test experiments to under-predict total mass of plumes and over-predict spatial distribution due to lack of process-based information in the prior constraints. The basis-constrained inversion method was developed to incorporate physics-based a priori information about the geologic setting and plume shape from training images to aid in reconstruction. The goal of this project is to use the basis-constrained inversion to reconstruct ERT data collected from a controlled field experiment at the Massachusetts Military Reservation in Cape Cod. To assess improvements in plume mass and morphology estimations, we will compare the results to reconstruction of the same plume using the traditional Tikhonov inversion method.
Eric's Presentation Description
"Detection of Firn Aquifer Draining Crevasses in Southeast Greenland."
In the near future, the massive amount of water stored as ice in Greenland Ice Sheet will have a significant impact on sea level rise. Understanding glacial hydrology is therefore critical to predicting the contribution the Greenland Ice Sheet will have. One aspect of glacial hydrology is firn aquifers. Firn aquifers are large stores of liquid water found in the porous firn layer some tens of meters below the surface of some glaciers. They are created when spring meltwater percolates down into the glacier and is kept liquid by high snowfall rates which insulate it from cold winter temperatures. With regards to the Greenland Ice Sheet, these conditions are predominantly found in its southeast region, with smaller firn aquifers found elsewhere along the coast. The water stored in these aquifers moves downstream, in the direction of ice flow, before eventually forcing its way to the bed through crevasses. This input of firn aquifer water to the bed is thought to affect how fast the glaciers will flow. It lubricates the ice sheet bed and hastens the glaciers’ flow to the sea. However, the spatial distribution of the crevasses which drain the firn aquifers and how these aquifers evolve over time is still relatively unknown.
Using a tool in GHub, a new online repository of datasets, tools, and supercomputing resources for ice sheet science, we analyzed data from the Airborne Topographic Mapper (ATM) gathered by NASA’s Operation IceBridge (OIB) from 2013 - 2018. Specifically, we find significant anomalies in the glacier surface elevation, that signify the presence of crevasses, and detect the apparent depths, widths, and locations of crevasses near known firn aquifers. We use our results to determine the spatial relationship between firn aquifers and wide crevasses may indicate surface-to-bed hydrofractures, along with how these crevasses change year to year.
We determined that wide crevasses which are thought to carry the aquifer water to the ice sheet bed are found near the downstream border of the established firn aquifers along all OIB flight lines studied. Additionally, we find that the crevasses are distributed in a pattern that seems to indicate that thinner, smaller crevasses upstream that don’t reach the bed evolve over the years to become the wider firn aquifer draining crevasses.
This research will help us further constrain our models of how meltwater reaches the ice sheet bed in these settings and will allow us to understand in greater depth glacier flow and its contribution to future sea level rise. Better understanding of glacial hydrology will allow us to more accurately predict the rate of sea level rise and allow us to prepare for the impacts it will bring.
The presentation is free, but registration is required to obtain the link.