Basin-scale heterogeneity in Antarctic precipitation and its impact on surface mass variability

Abstract

Abstract. Annually averaged precipitation in the form of snow, the dominant term of the Antarctic Ice Sheet surface mass balance, displays large spatial and temporal variability. Here we present an analysis of spatial patterns of regional Antarctic precipitation variability and their impact on integrated Antarctic surface mass balance variability simulated as part of a preindustrial 1800-year global, fully coupled Community Earth System Model simulation. Correlation and composite analyses based on this output allow for a robust exploration of Antarctic precipitation variability. We identify statistically significant relationships between precipitation patterns across Antarctica that are corroborated by climate reanalyses, regional modeling and ice core records. These patterns are driven by variability in large-scale atmospheric moisture transport, which itself is characterized by decadal- to centennial-scale oscillations around the long-term mean. We suggest that this heterogeneity in Antarctic precipitation variability has a dampening effect on overall Antarctic surface mass balance variability, with implications for regulation of Antarctic-sourced sea level variability, detection of an emergent anthropogenic signal in Antarctic mass trends and identification of Antarctic mass loss accelerations.

The Signature of Ozone Depletion in Recent Antarctic Precipitation Change: A Study With the Community Earth System Model

“…Additional features in the spatial pattern of precipitation change are associated with regional foci of ozone-depletion-forced atmospheric circulation changes. Most clearly, ozone depletion-driven Amundsen-Bellingshausen Sea Low strengthening (England et al, 2016) favors more/less frequent intrusions of moisture-loaded air over the eastern/western WAIS (Fyke et al, 2017), resulting in the prominent WAIS precipitation change dipole. Another foci of lower DJF pressure at ∼140 ∘ E promotes a snowfall response dipole in east/west Wilkes Land (East Antarctica Ice Sheet, EAIS), with the separation between the poles well represented by the north/south trending ice sheet divide at ∼135 ∘ E. Finally, a region of insignificant pressure change in the deep EAIS interior promotes two local minima in precipitation change westward of the Dome Argus and Dome Fuji ice divides.…”

“…Antarctic ice dynamics are not represented. Previous studies (Fyke et al, 2017;Lenaerts et al, 2016) have described a reasonable CESM representation of Antarctic precipitation spatial distribution, mean climatology, and natural variability relative to regional models and direct observations. This is confirmed by comparison of P − E (precipitation minus evaporation) between CESM and reconstructed values based on ice cores and the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) atmospheric reanalysis (see section 2.2), shown in supporting information Figure S1.…”

“…Owing to its large surface area, even small changes in Antarctic precipitation can impact global sea-level variability and trends (Boening et al, 2012;Shepherd et al, 2012). Antarctic precipitation exhibits high and often counteracting spatiotemporal variability (Boening et al, 2012;Fyke et al, 2017;Mémin et al, 2015) that is regulated by internal climate variability arising from polar climate dynamics (Marshall, 2003) and lower-latitude coupled climate processes (Yuan et al, 2018). Underlying this variability are forced signals from greenhouse gas and stratospheric ozone-depleting substance (ODS) changes.…”

Four decades of Antarctic surface elevation changes from multi-mission satellite altimetry

“…Rignot et al (2008) observed no significant mass changes in this region between 1992 and 2006 using the input-output method. Gardner et al (2018) compared present-day ice flow velocities to measurements from 2008. They obtain a slightly reduced ice discharge in DML (which would support the hypothesis of a dynamic thickening), while they observe a small increase in discharge for Enderby Land.…”

Observing and Modeling Ice Sheet Surface Mass Balance

“…Although the mean (grounded) AIS SMB is almost six times higher than the GrIS SMB (~2,150 vs. ~365 Gt/year), its absolute interannual variability is actually smaller (~100 Gt/year, or ~5% of the mean). This can be explained by (1) only precipitation variability contributing to AIS SMB variability, in the general absence of surface runoff, and sublimation being about ten times smaller and with low interannual variability, and (2) a larger surface area of the AIS, where negative precipitation anomalies in some regions are compensated by positive anomalies elsewhere (Fyke et al, ).…”