National Aeronautics and Space Administration

Sea Level Rise Seminar
Speaker: Emily Glazer (Columbia/LDEO)
Title: Impacts of Temperature- and Stress-Dependent Rheology on Ice-Shelf-Front Bending

This is an on-line, virtual presentation only. Please consult with event host Patrick Alexander for connection details.

Abstract:
Classical treatments of ice-shelf bending suggest that shelf fronts should bend downwards due to the distribution of hydrostatic water pressure. However, lidar data show several instances of upward-bending ice-shelf fronts. While this phenomenon is often attributed to a buoyant force from a submerged ice bench, recent work suggests that vertical variations in ice viscosity, driven by temperature gradients, can induce an internal bending moment that causes uplift even in the absence of a bench. Comparing models of this novel bending mechanism with observations can help constrain the parameters describing ice rheology, and improve predictions of ice-shelf calving and sea-level rise.


We present the first two-dimensional, viscoelastic models of ice-shelf bending with temperature- and depth-dependent ice softness. Using a standard Glen's flow law (n = 3), our results confirm that an ice-shelf front can bend upwards with a sufficiently cold surface temperature and strong temperature dependence of viscosity. We extend this idea by incorporating more realistic ice rheology that combines two viscous creep mechanisms: grain-boundary sliding (n = 1.8) and dislocation creep (n = 4). Analytic results and preliminary 2D models show that this more complex rheology still produces a positive bending moment, and may even do so at warmer surface temperatures than the simpler model predicted.

Our models confirm that internal viscosity gradients alone can drive upward bending, and that the resulting edge deflection actually outpaces the thin-plate prediction due to a two-dimensional "bulge" effect. We also find that this uplift mechanism produces shorter flexural wavelengths than the submerged bench mechanism, providing a way to distinguish between causes of upward bending in lidar data. Sonar measurements of the ice-shelf-front shape may also help test this mechanism and place new constraints on ice rheology.

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Historical and Paleoclimate Aerosol Radiative Effects Workshop

Abstract:
Constraining uncertainty in past radiative effects for non-CO2 components like dust and other aerosols play a critical role in understanding climate feedbacks and effective climate sensitivity, yet their contributions remain poorly quantified. Paleoclimate reconstructions reveal that natural aerosol emissions, including wildfire and dust, varied from the Last Glacial Maximum through the preindustrial era to today, and these variations are not captured in the latest CMIP6 simulations. This discrepancy between observations and model estimates of aerosol changes challenges the common assumption in many climate models that historical and paleoclimate aerosol preindustrial emissions are well-constrained. Consequently, current model-based estimates of aerosol radiative forcing and climate sensitivity likely underestimate uncertainty by neglecting the uncertainty in emissions. In this workshop, we seek to bring together experts in paleoclimate, aerosol radiative forcing, and climate sensitivity to develop coordinated strategies to assess observational and modeling constraints on past emissions and to characterize the resulting radiative forcing uncertainties.

[ Close ]

Historical and Paleoclimate Aerosol Radiative Effects Workshop

Abstract:
Constraining uncertainty in past radiative effects for non-CO2 components like dust and other aerosols play a critical role in understanding climate feedbacks and effective climate sensitivity, yet their contributions remain poorly quantified. Paleoclimate reconstructions reveal that natural aerosol emissions, including wildfire and dust, varied from the Last Glacial Maximum through the preindustrial era to today, and these variations are not captured in the latest CMIP6 simulations. This discrepancy between observations and model estimates of aerosol changes challenges the common assumption in many climate models that historical and paleoclimate aerosol preindustrial emissions are well-constrained. Consequently, current model-based estimates of aerosol radiative forcing and climate sensitivity likely underestimate uncertainty by neglecting the uncertainty in emissions. In this workshop, we seek to bring together experts in paleoclimate, aerosol radiative forcing, and climate sensitivity to develop coordinated strategies to assess observational and modeling constraints on past emissions and to characterize the resulting radiative forcing uncertainties.

[ Close ]

Historical and Paleoclimate Aerosol Radiative Effects Workshop

Abstract:
Constraining uncertainty in past radiative effects for non-CO2 components like dust and other aerosols play a critical role in understanding climate feedbacks and effective climate sensitivity, yet their contributions remain poorly quantified. Paleoclimate reconstructions reveal that natural aerosol emissions, including wildfire and dust, varied from the Last Glacial Maximum through the preindustrial era to today, and these variations are not captured in the latest CMIP6 simulations. This discrepancy between observations and model estimates of aerosol changes challenges the common assumption in many climate models that historical and paleoclimate aerosol preindustrial emissions are well-constrained. Consequently, current model-based estimates of aerosol radiative forcing and climate sensitivity likely underestimate uncertainty by neglecting the uncertainty in emissions. In this workshop, we seek to bring together experts in paleoclimate, aerosol radiative forcing, and climate sensitivity to develop coordinated strategies to assess observational and modeling constraints on past emissions and to characterize the resulting radiative forcing uncertainties.

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