Glacies, Volume 1, Issue 2 (December 2024) – 3 articles

In this study, we look for a relationship between the lack of drawdown dolines and the karren formation taking place on the bare surfaces of glaciokarsts. Along the profiles, the specific width and density of the most common karren such as rinnenkarren, grikes, and pits were studied, while in three mapped areas, the depth and depth change in rinnenkarren were investigated in various environments. Mainly, carbonate dissolution of a low degree takes place at atmospheric CO₂. Therefore, in the case of carbonate dissolution taking place on the bare surfaces of glaciokarsts, the chance of cavity formation in the epikarst is analysed at karren of percolation origin (grike, pit) and at karren of flow origin (rinnenkarren). Vertical infiltration and local cavity formation are only possible at pits (the CO₂ quantity increases due to the soil effect in them). Therefore, below the bare surfaces of glaciokarsts, as a result of low dissolution capacity and infiltration of low degree, there is no cavity formation, or it is weakly developed. The piezometric surface is absent or it is local, its surface is not deflected. Drainage is not heterogeneous, but it is local, which does not favour drawdown doline development since drawdown dolines develop in the case of epikarst with well-developed, heterogeneous cavitation and deflected piezometric surface. Full article

Supraglacial melt-lakes form and evolve along the western edge of the Greenland Ice Sheet and have proven to play a significant role in ice sheet surface hydrology and mass balance. Prior methods to quantify melt-lake volume have relied upon Landsat-8 optical imagery, available at 30 m spatial resolution but with temporal resolution limited by satellite overpass times and cloud cover. We propose two novel methods to quantify the volume of meltwater stored in these lakes, including a high-resolution surface DEM (ArcticDEM) and an ablation model using daily averaged automated weather station data. We compare our methods to the depth-reflectance method for five supraglacial melt-lakes during the 2021 summer melt season. We find agreement between the depth-reflectance and DEM lake infilling methods, within +/−15% for most cases, but our ablation model underproduces by 0.5–2 orders of magnitude the volumetric melt needed to match our other methods, and with a significant lag in meltwater onset for routing into the lake basin. Further information regarding energy balance parameters, including insolation and liquid precipitation amounts, is needed for adequate ablation modelling. Despite the differences in melt-lake volume estimates, our approach in combining remote sensing and meteorological methods provides a framework for analysis of seasonal melt-lake evolution at significantly higher spatial and temporal scales, to understand the drivers of meltwater production and its influence on the spatial distribution and extent of meltwater volume stored on the ice sheet surface. Full article

The Cenozoic glaciation of Antarctica proceeded through two distinct steps around 35 and 15 million years ago. The first icing was attributed to thermal isolation due to the opening of the Drake/Tasman passages and the development of the Antarctic circumpolar current. I also subscribe to this “thermal isolation” but posit that, although the snowline was lowered below the Antarctic plateau for it to be iced over, the glacial line remains above sea level to confine the ice sheet to the plateau, a “partial” glaciation that would be sustained over time. The origin of the second icing remains unknown, but based on the sedimentary evidence, I posit that it was triggered when the isostatic rebound of West Antarctica caused by heightened erosion rose above the glacial line to be iced over by the expanding plateau ice, and the ensuing cooling lowered the glacial line to sea level to cause the “full” glaciation of Antarctica. To test these hypotheses, I formulate a minimal box model, which is nonetheless subjected to thermodynamic closure that allows a prognosis of the Miocene climate. Applying representative parameter values, the model reproduces the observed two-step icing followed by the stabilized temperature level, in support of the model physics. Full article