How does the ice sheet surface mass balance relate to snowfall? Insights from a ground-based precipitation radar in East Antarctica

Abstract

Abstract. Local surface mass balance (SMB) measurements are crucial for understanding changes in the total mass of the Antarctic Ice Sheet, including its contribution to sea level rise. Despite continuous attempts to decipher mechanisms controlling the local SMB, a clear understanding of the separate components is still lacking, while snowfall measurements are almost absent. In this study, the different terms are quantified at the Princess Elisabeth (PE) station in Dronning Maud Land, East Antarctica. Furthermore, the relation between snowfall and accumulation at the surface is investigated. To achieve this, a 5 unique collocated set of remote sensing instrumentation (Micro Rain Radar, ceilometer, Automatic Weather Station, among others) was established operating for an unprecedented time period of 37 months. Snowfall originates mainly from moist and warm air advected from lower latitudes associated with cyclone activity. However, snowfall events are much more common than accumulation events. During 38 % of the snowfall cases observed, the freshly-fallen snow is ablated by the wind during the course of the event. Generally, snow storms of longer duration have a higher chance to attain for accumulation at the local scale, 10 while shorter events usually attain for ablation (on average 17 and 12 hours respectively). As such, SMB records cannot be considered a good proxy for snowfall at the local scale. Accumulation and ablation also occur during non-snowfall conditions. A large part of the accumulation at the station takes place when preceding snowfall events were occurring in upstream coastal areas. This fresh snow is easily picked up and transported in shallow drifting snow layers to more inland locations, even when wind speed is relatively low (< 7 ms −1 ). Ablation events are mainly related to katabatic winds originating from the Antarctic 15 plateau and the mountain ranges in the south. These dry winds are able to remove snow and lead to a decrease in the local SMB. This work highlights that, even though observations are local, the SMB is strongly influenced by synoptic upstream conditions.

Thermally induced icequakes detected on blue ice areas of the East Antarctic ice sheet

“…On the other hand, in winter, the snow surface temperature is primarily controlled by longwave radiation and turbulent fluxes which do not depend on the ground albedo. However, both longwave radiative and turbulent fluxes vary strongly with the alternation of cold katabatic and warm synoptic regimes affecting both the snow and BIAs (Thiery and others, 2012; Gorodetskaya and others, 2013; Souverijns and others, 2018). Our analysis at Svea (Fig.…”

“…The wind would have an effect on the observations by lowering the signal-to-noise ratio, thus decreasing the total number of detected events. Additionally, at PEA, annual mean wind speed is relatively low compared to most places in Antarctica (Thiery and others, 2012; Gorodetskaya and others, 2013; Souverijns and others, 2018). For the time period considered here, the mean wind speed is 4.5 m s −1 with a slight increase to 5.0 m s −1 during the winter period.…”

A New Regional Climate Model for POLAR‐CORDEX: Evaluation of a 30‐Year Hindcast with COSMO‐CLM2 Over Antarctica

“…A cold high pressure system is located over the continent, feeding the katabatic flows from the interior plateau toward the escarpment of the coast (van Lipzig, Turner, et al,). Apart from the katabatic flow, the large‐scale flow at the coastal margins of the AIS is dominated by the circumpolar vortex, that is, cyclonic activity near the coast of the AIS allowing for the transport of moisture and air from midlatitudes to the AIS at high wind speeds (Gorodetskaya et al, ; Souverijns et al, , ).…”

“…However, other processes also play a role in (local) SMB. Wind‐driven snow transport is an important process in redistributing snow over the ice sheet (Souverijns et al, ) and in the creation of blue ice zones (Takahashi, ). But integrated over the ice sheet, the importance of snow removal by erosion is estimated to be 2 orders of magnitude smaller than surface sublimation (Déry & Yau, ).…”

CCN measurements at the Princess Elisabeth Antarctica research station during three austral summers

“…The basic meteorological parameters (near-surface air temperature, pressure, relative humidity, wind speed and wind direction) were measured by means of an automatic weather station (AWS; Gorodetskaya et al, 2013;Souverijns et al, 2018) which was located 300 m east of PE. The snowfall rates (S) were derived from Metek's Micro-Rain-Radar (MRR-2) effective reflectivities (Z), applying an Z-S relationship derived specifically for the PE location .…”