Modeled Antarctic Precipitation. Part I: Spatial and Temporal Variability*

Abstract

Surface snow accumulation is the primary mass input to the Antarctic ice sheets. As the dominant term among various components of surface snow accumulation (precipitation, sublimation/deposition, and snow drift), precipitation is of particular importance in helping to assess the mass balance of the Antarctic ice sheets and their contribution to global sea level change. The Polar MM5, a mesoscale atmospheric model based on the fifth-generation Pennsylvania State University-NCAR Mesoscale Model, has been run for the period of July 1996 through June 1999 to evaluate the spatial and temporal variability of Antarctic precipitation. Drift snow effects on the redistribution of surface snow over Antarctica are also assessed with surface wind fields from Polar MM5 in this study. It is found that areas with large drift snow transport convergence and divergence are located around escarpment areas where there is considerable katabatic wind acceleration. It is also found that the drift snow transport generally diverges over most areas of East and West Antarctica with relatively small values. The use of the dynamic retrieval method (DRM) to calculate precipitation has been developed and verified for the Greenland ice sheet. The DRM is also applied to retrieve the precipitation over Antarctica from 1979 to 1999 in this study. Most major features in the spatial distribution of Antarctic accumulation are well captured by the DRM results. In comparison with predicted precipitation amounts from atmospheric analyses and reanalyses, DRM calculations capture more mesoscale features of the precipitation distribution over Antarctica. A significant upward trend of ϩ1.3 to ϩ1.7 mm yr Ϫ2 for 1979-99 is found from DRM and forecast precipitation amounts for Antarctica that is consistent with results reported by other investigators and indicates that an additional 0.05 mm yr Ϫ1 is being extracted from the global ocean and locked up in the Antarctic ice sheets. While there is good agreement in this trend among all of the datasets, the interannual variability about the trend on the continental scale is not well captured. However, on the subcontinental scale, the interannual variability about the trend is well resolved for sectors in West Antarctica and the South Atlantic. It is also noted that the precipitation trend is weakly downward over much of the continent.

Multi-year record of atmospheric mercury at Dumont d'Urville, East Antarctic coast: continental outflow and oceanic influences

“…10, Hg tot concentrations increased between 600-800 and 1000-1100 km from DC in areas characterized by steeper slopes and higher snow accumulation values. Several studies reported a gradual increase in snow accumulation from DC toward the coast (Magand et al, 2007;Verfaillie et al, 2012;Favier et al, 2013), in good agreement with a gradual increase in humidity (Bromwich et al, 2004). These results suggest that the wet deposition of Hg(II) species was enhanced near the coast, resulting in elevated Hg tot concentrations in surface snow samples.…”

A Review of Antarctic Surface Snow Isotopic Composition: Observations, Atmospheric Circulation, and Isotopic Modeling*

“…These models are used to assess the Antarctic surface mass balance (Gallee et al 2001;Bromwich et al 2004;Van de Berg et al 2006), and therefore have a strong focus on moisture transport.…”

On the freshening of the northwestern Weddell Sea continental shelf

“…The results of atmospheric analyses and re-analyses products together with a dynamic retrieval method to calculate precipitation for the period 1979 to 1999 show higher amplitudes and a higher annual mean precipitation for the South Atlantic sector (65 • -75 • S, 30 • -60 • W) starting in 1988 (Fig. 16 in Bromwich et al, 2004). Considering the two peaks in 1989 and 1996, representing an increase in precipitation of 0.16 m a −1 and 0.12 m a −1 , respectively, the volume of freshwater added within one year to the surface area of 1.652×10 5 km 2 , used above to calculate the water volume on the northwestern continental shelf (<500 m), would rise to 26 × 10 9 m 3 (26 km 3 ) and 20 × 10 9 m 3 (20 km 3 ).…”