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Despite improvements in ambient air quality in the US in recent decades, many people still experience unhealthy levels of pollution. At present, national‐level alert‐day identification relies predominately on surface monitor networks and forecasters. Satellite‐based estimates of surface air quality have rapidly advanced and have the capability to inform exposure‐reducing actions to protect public health. At present, we lack a robust framework to quantify public health benefits of these advances in applications of satellite‐based atmospheric composition data. Here, we assess possible health benefits of using geostationary satellite data, over polar orbiting satellite data, for identifying particulate air quality alert days (24hr PM_2.5 > 35 μg m⁻³) in 2020. We find the more extensive spatiotemporal coverage of geostationary satellite data leads to a 60% increase in identification of person‐alerts (alert days × population) in 2020 over polar‐orbiting satellite data. We apply pre‐existing estimates of PM_2.5exposure reduction by individual behavior modification and find these additional person‐alerts may lead to 1,200 (800–1,500) or 54% more averted PM_2.5‐attributable premature deaths per year, if geostationary, instead of polar orbiting, satellite data alone are used to identify alert days. These health benefits have an associated economic value of 13 (8.8–17) billion dollars ($2019) per year. Our results highlight one of many potential applications of atmospheric composition data from geostationary satellites for improving public health. Identifying these applications has important implications for guiding use of current satellite data and planning future geostationary satellite missions.

 

Numerical ice sheet models use sliding laws to connect basal shear stress and ice velocity to simulate ice sliding. A sliding‐law parameterβ²is used to control Weertman's sliding law in numerical ice sheet models. Basal reflectivity derived from ice‐penetrating radar also provides information about frozen or thawed conditions underneath glaciers. To assess whether basal reflectivity can be used to constrainβ², we carry out statistical experiments between two recently published datasets:β²inferred from three numerical ice sheet models (ISSM, Úa and STREAMICE) and airborne radar‐derived relative basal reflectivity from the AGASEA‐BBAS mission over Thwaites Glacier (TG). Our results show no robust correlation between theβ²–relative reflectivity pair. Pearson's correlation coefficient, a test of linearity, ranges from −0.26 to −0.38. Spearman's correlation coefficient, which does not require a linear assumption, is also modest (∼−0.35). We conclude thatβ²and relative basal reflectivity underneath TG do not infer similar basal conditions.

 

Abstract. Among the most important challenges faced by ice flow models is how to represent basal and rheological conditions, which are challenging to obtain from direct observations. A common practice is to use numerical inversions to calculate estimates for the unknown properties, but there are many possible methods and not one standardised approach. As such, every ice flow model has a unique initialisation procedure. Here we compare the outputs of inversions from three different ice flow models, each employing a variant of adjoint-based optimisation to calculate basal sliding coefficients and flow rate factors using the same observed surface velocities and ice thickness distribution. The region we focus on is the Amundsen Sea Embayment in West Antarctica, the subject of much investigation due to rapid changes in the area over recent decades. We find that our inversions produce similar distributions of basal sliding across all models, despite using different techniques, implying that the methods used are highly robust and represent the physical equations without much influence by individual model behaviours. Transferring the products of inversions between models results in time-dependent simulations displaying variability on the order of or lower than existing model intercomparisons. Focusing on contributions to sea level, the highest variability we find in simulations run in the same model with different inversion products is 32 %, over a 40-year period, a difference of 3.67 mm. There is potential for this to be improved with further standardisation of modelling processes, and the lowest variability within a single model is 13 %, or 1.82 mm over 40 years. While the successful transfer of inversion outputs from one model to another requires some extra effort and technical knowledge of the particular models involved, it is certainly possible and could indeed be useful for future intercomparison projects. 

Thwaites and Pine Island Glaciers as well as other ice streams in West Antarctica have been changing dramatically over the past decades. Although changes in ocean conditions are likely the primary driver of these changes, it remains unclearwhereother processes could cause more mass loss. By employing Automatic Differentiation and two independent ice‐sheet models, we construct maps of the sensitivity of the volume above floatation to changes in ocean‐induced melt rates, ice rigidity, basal friction, and surface mass balance. We find that changes in basal melt close to the grounding lines and along shear margins have a larger impact on the glaciers' final volume. The glaciers are sensitive to changes in basal friction on regions close to the grounding lines, while changes in ice rigidity has a larger impact along the shear margins of Pine Island. The sensitivity to surface mass balance is uniform over grounded ice.

 

Using three independent ice‐flow models and several satellite‐based datasets, we assess the importance of correctly capturing ice‐shelf breakup, shelf thinning, and reduction in basal traction from ungrounding in reproducing observed speed‐up and thinning of Thwaites Glacier between 1995 and 2015. We run several transient numerical simulations applying these three perturbations individually. Our results show that ocean‐induced ice‐shelf thinning generates most of the observed grounding line retreat, inland speed‐up, and mass loss, in agreement with previous work. We improve the agreement with observed inland speed‐up and thinning by prescribing changes in ice‐shelf geometry and a reduction in basal traction over areas that became ungrounded since 1995, suggesting that shelf breakups and thinning‐induced reduction in basal traction play a critical role on Thwaites's dynamics, as pointed out by previous studies. These findings suggest that modeling Thwaites's future requires reliable ocean‐induced melt estimates in models that respond accurately to downstream perturbations.