Influence of persistent wind scour on the surface mass balance of Antarctica

Abstract

Accurate quantification of surface snow accumulation overAntarctica is a key constraint for estimates of the Antarctic mass balance, as well as climatic interpretations of ice-core records 1,2 . Over Antarctica, near-surface winds accelerate down relatively steep surface slopes, eroding and sublimating the snow. This wind scour results in numerous localized regions (≤200 km 2 ) with reduced surface accumulation 3-7 . Estimates of Antarctic surface mass balance rely on sparse point measurements or coarse atmospheric models that do not capture these local processes, and overestimate the net mass input in wind-scour zones 3 . Here we combine airborne radar observations of unconformable stratigraphic layers with lidar-derived surface roughness measurements to identify extensive wind-scour zones over Dome A, in the interior of East Antarctica. The scour zones are persistent because they are controlled by bedrock topography. On the basis of our Dome A observations, we develop an empirical model to predict wind-scour zones across the Antarctic continent and find that these zones are predominantly located in East Antarctica. We estimate that ∼2.7-6.6% of the surface area of Antarctica has persistent negative net accumulation due to wind scour, which suggests that, across the continent, the snow mass input is overestimated by 11-36.5 Gt yr −1 in present surface-massbalance calculations.Over the interior of East Antarctica, significant spatial variability in snow accumulation results from the temperature inversion and gravity-driven katabatic winds interacting with ice surface topography 1,3,7,8 . These katabatic winds erode and sublimate both drifting snow and snow layers on the ground 1 . Extensive regions of wind-induced zero or near-zero surface mass balance (SMB) have been identified by airborne ice-penetrating radars 6 , satellite remote sensing 3 and ground traverses 1,4,[9][10][11][12][13][14] . A small fraction of the eroded snow over these regions is redeposited downslope forming dunes or infilling topographic depressions and the rest is sublimated 13,14 . Evaluating this complex deposition process over a low accumulation area such as the interior of East Antarctica is important for improving SMB estimates and annual accumulation from ice cores.Where the winds completely remove the annual snowfall over the scour zones, increased absorption of short-wave solar radiation and enhanced vapour transport facilitate grain growth and metamorphosis of the near-surface firn layers 3,[14][15][16] . In radar stratigraphy, these buried, metamorphosed layers form

Widespread movement of meltwater onto and across Antarctic ice shelves

“…Low-albedo blue ice 11,23 , nunataks and surface debris facilitate melting by increasing the absorption of solar energy 24 . Blue ice forms when snow is entirely removed by wind erosion 25 , sublimation or melt, often adjacent to nunataks 26 , because rugged terrain promotes high winds and lowalbedo rock increases air temperatures 27 . Melting and wind erosion lower the ice surface, enlarging areas of exposed rock, leading to coupling between melting, rock exposure and blue-ice formation.…”

Where to find 1.5 million yr old ice for the IPICS "Oldest-Ice" ice core

“…While such features affect the diffusive transport of gases within the top of the firn column, they do not corrupt the gas records in the ice per se. Another surface feature of the East Antarctic ice sheet is snow scouring leading to wind glazing that can be identified using satellite images (Das et al, 2013;Scambos et al, 2012). This wind scouring may cause persistent loss of snow accumulation and potentially create hiatuses in a potential Oldest-Ice ice core.…”

Influence of meter-scale wind-formed features on the variability of the microwave brightness temperature around Dome C in Antarctica

“…Glazed surfaces (Frezzotti et al, 2002a;Scambos et al, 2012), thermal cracks and irregular patches of hoar on the surface (Gow, 1969;Courville et al, 2007) can also be found at some specific points. These features affect the distribution of snow accumulation and represent one of the challenges in scaling up local surface mass balance measurements to the continent scale (Goodwin, 1990;Magand et al, 2008;Das et al, 2013). Although the size of these features is much smaller than the microwave radiometer footprint, they have an influence on the signal.…”