In this work, total smooth air-water interfacial areas were measured for a series of nine natural and model sandy porous media as a function of water saturation using synchrotron X-ray microtomography. Interfacial areas decreased linearly with water satuation, while the estimated maximum interfacial area compared favorably to the media geometric surface areas. Importantly, relative interfacial area (i.e., normalized by geometric surface area) versus water saturation plots for all media collapsed into a single linear cluster (r2 = 0.93), suggesting that geometric surface area is an important, and perhaps sufficient, descriptor of sandy media that governs total smooth interfacial area-water saturation relationships. Measured relationships were used to develop an empirical model for estimating interfacial area-water saturation relationships for sandy porous media. Model-based interfacial area estimates for independent media were generally slightly higher than interfacial areas measured using aqueous-phase interfacial tracer methods, which may indicate that microtomography captures regions of the air-water interface that are not accessible to aqueous-phase interfacial tracers. The empirical model presented here requires only average particle diameter and porosity as input parameters and can be used to readily estimate air-water interfacial area-water saturation relationships for sandy porous media.

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Abstract. It is well known that during polar springtime halide sea salt ions, in particular Br-, are photochemically activated into reactive halogen species (e.g., Br and BrO), where they break down tropospheric ozone. This research investigated the role of blowing snow in transporting salts from the sea ice/snow surface into reactive bromine species in the air. At two different locations over first-year ice in the Ross Sea, Antarctica, collection baskets captured blowing snow at different heights. In addition, sea ice cores and surface snow samples were collected throughout the month-long campaign. Over this time, sea ice and surface snow Br- / Cl- mass ratios remained constant and equivalent to seawater, and only in lofted snow did bromide become depleted relative to chloride. This suggests that replenishment of bromide in the snowpack occurs faster than bromine activation in mid-strength wind conditions (approximately 10 m s−1) or that blowing snow represents only a small portion of the surface snowpack. Additionally, lofted snow was found to be depleted in sulfate and enriched in nitrate relative to surface snow.

Of critical importance for avalanche forecasting, is the ability to draw meaningful conclusions from only a handful of field observations. To that end, it is common for avalanche forecasters to not only have to rely on sparse data, but also on their own intuitive understanding of how their field-based observations may be correlated to complex physical processes responsible for structural instability within a snowpack. One such well-documented basis for mechanical instability to increase within a snowpack is that caused by the presence of a buried ice lens or ice crust. Although such icy layers are naturally formed and frequently encountered in seasonal snowpacks, very little is known about the microstructural evolution of these layers and how they contribute towards weak layer development. Furthermore, in terms of assessing the structural integrity of the snowpack, there is at the present time no consistent treatment for identifying these layers a priori as problematic or benign. To address this issue, we have created an idealized laboratory scenario in which we can study how an artificially created ice lens may affect the thermophysical and microstructural state of the interface between the ice lens and adjacent layers of snow while under a controlled temperature gradient of primarily-100 K m-1. Utilizing in situ micro-thermocouple measurements, our findings show that a super-temperature gradient exists within only a millimeter of the ice

Abstract. The brine pore space in sea ice can form complex connected structures whose geometry is critical in the governance of important physical transport processes between the ocean, sea ice, and surface. Recent advances in threedimensional imaging using X-ray micro-computed tomography have enabled the visualization and quantification of the brine network morphology and variability. Using imaging of first-year sea ice samples at in situ temperatures, we create a new mathematical network model to characterize the topology and connectivity of the brine channels. This model provides a statistical framework where we can characterize the pore networks via two parameters, depth and temperature, for use in dynamical sea ice models. Our approach advances the quantification of brine connectivity in sea ice, which can help investigations of bulk physical properties, such as fluid permeability, that are key in both global and regional sea ice models.