Extreme wind‐ice interaction over Recovery Ice Stream, East Antarctica

Abstract

Surface snow accumulation over East Antarctica is an important climate indicator but a difficult parameter to constrain. Surface mass ablation dominates over persistent wind‐scour zones as near‐surface katabatic winds accelerate over locally steeper ice surface topography, and sublimate and redistribute snow. Here we quantify ablation rates and downwind redeposition of snow over wind‐scour zones in the upper Recovery Ice Stream catchment. Airborne radio echo‐soundings show a gradual ablation of ~16–18 m of firn, corresponding to ~200 years of accumulation, over these zones and ablation rates of ~54 kg m−2 a−1 (54 mm water equivalent a−1). We conclude that mass loss is dominated by sublimation and mass is transported downwind as water vapor, because snow redeposition downslope of the wind‐scour zones constitutes only a small fraction (<10%) of the cumulative mass loss.

Annual Greenland accumulation rates (2009–2012) from airborne snow radar

“…Assuming uncorrelated and normally distributed errors between density, age and layer picking the mean accumulation-rate uncertainty is 14 %, with a range of 13 % for the highest accumulation rates and 27 % for the lowest accumulation rates. This relative uncertainty is similar to previous studies by Medley et al (2013) and Das et al (2015) for radar-derived accumulation rates.…”

“…For example, in the centralnorthern GrIS, there is a strongly reflecting layer varying be- tween 15 and 18 m that cannot be dated with the radar data alone. If ice cores were drilled to identify the age of this layer, techniques similar to those developed by MacGregor et al (2015) or Das et al (2015) could be used to determine multiannual accumulation rates in additional regions of the GrIS and extend the snow radar record. Further deconvolution processing of these data, currently ongoing, will likely also resolve additional deeper layers in the snow radar data.…”

“…Hence, the numerator is the mass in kg m −2 to depth z, a is age of the layer in years from the date of radar data collection and ρ w is the density of water in kg m −3 (e.g. Medley et al, 2013;Das et al, 2015). Depth z is calculated using the radar two-way travel time (TWT), the snow/firn density (ρ) and the Looyenga (1965) dielectric mixing relationship as follows:…”

“…Medley et al (2013) and Das et al (2015) showed that accumulation rates could also be derived using density from a regional ice-core ensemble. Density end members are used to derive uncertainty limits, and the derived regional density profile is sufficient for radar studies of accumulation and SMB (Das et al, 2015). Additionally, Medley et al (2013) showed that snow radar is capable of resolving annual layer in high accumulation regions where such layers were well preserved.…”

Annual Greenland accumulation rates (2009–2012) from airborne Snow Radar

“…Hence, the two primary methods used to generate large-scale (hundreds of kilometers) accumulation-rate patterns are model outputs and radar-derived accumulation rates (Koenig et al, 2015). High-resolution, near-surface radar data have shown good fidelity at mapping spatial patterns of accumulation over ice sheets at decadal and annual resolutions from both airborne and ground-based radars (Kanagaratnam et al, 2001(Kanagaratnam et al, , 2004Spikes et al, 2004;Arcone et al, 2005;Anshütz et al, 2008;Müller et al, 2010;Medley et al, 2013;Hawley et al, 2006;2014;de la Peña et al, 2010;Miège et al, 2013). Radars detect the lateral persistence of isochronal layers within the firn.…”