Combining Geophysical Observations and Models
Glacial Geophysicist
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GT Glacier Geophysics Group

Winnie Chu

Postdoctoral Researcher at Stanford University

(Now an Assistant Professor at Georgia Insitute of Technology)

ABOUT ME

I am a geophysicist who studies ice sheets and their interrelation with our climate system. I synthesize radar sounding technique and numerical ice-sheet modeling to understand what "mechanisms" cause a glacier to accelerate. From satellite measurements of ice velocity, we know that different glaciers do not accelerate in the same way as one another under similar climate forcings. The core of my research is to better understand how glacial dynamics respond to a varying climate. I specifically focus on ice-sheet hydrology, as it is one of the most critical processes influencing glacier dynamic behavior. You can learn more about my work in the research section below.

Research

I study ice/water interactions on glaciers and ice shelves in both Greenland and Antarctica.

Ice Sheet Hydrology

Ice sheets have three hydrological systems: at the top, within the ice, and at the bottom. The interaction between these systems governs the ice-sheet water budget and controls the amount of water flushed into the oceans along the edges. Quantifying and monitoring water storage within these systems is critical to assessing how ice sheets are adjusting to climate changes and predicting their future stability. I develop and apply geophysical techniques, such as ice-penetrating radar sounding, to constrain an ice sheet's top-to-bottom water budget. One of my primary goals is to understand what controls water storage on both ice sheet and ice shelf environments in Greenland and Antarctica.

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Water Storage and Seasonal Ice Velocity

On a seasonal scale, the presence of water at the ice-sheet bed can temporarily cause glacier velocity to speed-up; however, the ice sheet can experience vastly different responses to similar meltwater forcing, with one glacier showing massive speed-up while its neighbor barely notices the presence of water at its bed. I am fascinated by the complexity of how meltwater can interact with glacier motions and have made it a central focus of my research. I investigate this phenomenon by combining hydrological modeling and radar sounding to examine how meltwater drainage within an ice sheet evolves through time. Analysis of these results in the context of seasonal velocity observations from satellites will provide a clearer picture of what governs the response of individual glaciers to changes in meltwater.

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Water and Ice Sheet Thermal Regime

Water at the ice bed interacts with the ice-sheet thermal regime to create a complex ice flow structure. Changes in melting and freezing of water at the bed of the ice-sheet interior can cause glaciers to slow-down, and in dramatic cases, large ice streams to completely shut-down. Also at the bed, ice in contact with this water can soften and deform basal ice. This interaction of water and heat with basal ice makes it very challenging to apply traditional geophysical methods to constrain the basal condition, but by combining ice-sheet thermomechanical models with these observations, I can estimate these thermal effects to overcome this barrier and enable more robust constraints on the basal thermal conditions from geophysical data.

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Bridging Observations and Modeling

In order to produce policy-relevant sea-level projections, ice-sheet modelers require real-world observations. Radar data is an excellent source of real-world observations, but the majority of models only use radar-derived measurements of ice thickness. This is limiting for predictive models because there is significantly more information that radar sounding can provide like bed-echo-strengths and internal ice layer properties. Bed-echo-strength radar values represent information about basal sliding and internal ice layer properties illustrate past glacier flow and the thermal structure of an ice sheet. I am actively engaged in developing new algorithms for assimilating all radar sounding data in ice-sheet models, which will aid in improving our understanding of glacier dynamics and sea-level prediction.

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Papers

See more on my Google Scholar Profile

Submitted / In Review

  1. Bowling,J., S.J. Livingstone, A.J. Sole, W. Chu, 2018: Distribution and activity of Greenland subglacial lakes. Nat. Comm.
  2. Schroeder, D.M., J.A. Dowdeswell, R.G. Bingham, W. Chu, E.J. MacKie, M.R. Siegfried, J.R. Emmons, K.I. Vega, and K.J.Winstein, 2018: Multi-Decadal Observations of the Antarctic Ice Sheet from Archival Radar Film. PNAS.

Published

  1. Bell R.E., K. Tinto, I. Das, M. Wolovick, W. Chu, T.T Creyts, N. Frearson, A. Abdi, J.D. Paden, 2014: Deformation, warming and softening of Greenland’s ice by refreezing meltwater. Nat. Geosci.7(7), 497–502, doi:10.1038/ngeo2179. link
  2. Chu, W., T.T. Creyts, and R.E. Bell, 2016: Rerouting of subglacial water flow between neighboring glaciers in West Greenland. J. Geophys. Res. Earth Surf..121(5), 925–938, doi:10.1002/2015JF003705. link
  3. Schroeder, D. M., H. Seroussi, W. Chu, and D.A. Young, 2016: Adaptively constraining radar attenuation and temperature across the Thwaites Glacier catchment using bed echoes. J. Glaciology.62(236), 1075–1082, 10.1017/jog.2016.100. link
  4. Chu,W., D.M. Schroeder, H. Seroussi, T.T. Creyts, S.J. Palmer and R.E. Bell, 2016: Extensive winter subglacial water storage beneath the Greenland Ice Sheet. Geophys. Res. Lett.43(24), 484–492, 10.1002/2016GL071538. link
  5. Bell, R.E.,W. Chu, J. Kingslake, I. Das, M. Tedesco, K.J. Tinto et al., 2017: Antarctic ice shelf potentially stabilized by export of meltwater in surface river. Nature.544(7650), 344–348, 10.1038/nature22048. link
  6. Livingstone S.J., W. Chu, J.C. Ely, J. Kingslake, 2017: Paleofluvial and subglacial channel networks beneath Humboldt Glacier, Greenland. Geology.45(6), 551–554, 10.1130/G38860.1. link
  7. Chu W., D.M. Schroeder, H.S. Seroussi, T.T. Creyts, and R.E. Bell, 2018: Complex basal thermal transition near the onset of Petermann Glacier, Greenland. J. Geophys. Res. Earth Surf..123(5), 985–995, 10.1029/2017JF004561. link
  8. Kendrick, A.K., D.M. Schroeder, W. Chu., T.J. Young, P. Christoffersen., J.Todd and et al., 2019: Surface Meltwater Impounded by Seasonal Englacial Storage in West Greenland. Geophys. Res. Lett, 1–8, 10.1029/2018GL079787. link
  9. Chu, W., D.M. Schroeder and M.R. Siegfried, 2018: Retrieval of Englacial Firn Aquifer Thickness from Ice-Penetrating Radar Sounding in Southeastern Greenland. Geophys. Res. Lett45, doi:10.1029/2018GL079751. link
  10. Tinto, K., L. Padman, C. Siddoway, S.Springer, H.A. Fricker, I. Das, F.C. Tontini, D. Porter, N. Frearson, S. Howard, M.R. Siegfried, Mosbeux, E. Becker, C. Bertinato, A. Boghosian, Brady, C. Burton, W.Chu and et al, 2019: Ross Ice Shelf response to climate driven by the tectonic imprint on seafloor bathymetry. Nat.Geosci, In Press.

Service

Fieldwork

Field observations are essential for my research. I have taken part in airborne and ground-based geophysics expeditions to Alaska, Greenland, and Antarctica.

Greenland

2012 Summer test-flight airborne geophysical expedition for the NSF funded ROSETTA project to western Greenland.

Antarctica

Photos from 2013-14 ROSETTA deployment to study ice/ocean/tectonic interactions on the Ross Ice Shelf, and from 2016 NASA Operation IceBridge mission.

Alaska

Photos from glaciology excursion to Kennicott Glacier as part of a summer school workshop training on deploying ground-based geophysical instruments.