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

Jeremy Fyke,Jan T M Lenaerts,Hailong Wang

doi:10.5194/tc-11-2595-2017

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.

Highlights

Precipitation of snow is the means by which the Antarctic Ice Sheet (AIS), currently the largest contiguous ice complex on the planet, gains mass
This value is lower than recent historical mean CESM/RACMO2.3 precipitation assessed in Lenaerts et al (2016) and (Van Wessem et al, 2014; 2428/2829 Gt yr−1), due to the significant positive trend in historical CESMsimulated integrated Antarctic precipitation combined with an overall negative CESM precipitation bias
Stemming from the similarity between sea level pressure (SLP) and Z500 composite differences (r = 0.91) we focus our attention on the relationship of moisture flux changes to Z500 variability, which provides a consistent metric of atmospheric circulation both at sea level and over the elevated ice sheet topography (Genthon et al, 2003)

Summary

Introduction

Precipitation of snow is the means by which the Antarctic Ice Sheet (AIS), currently the largest contiguous ice complex on the planet, gains mass. Previous studies have leveraged Gravity Recovery and Climate Experiment (GRACE) output, satellite altimetry and/or regional modeling to highlight strongly heterogeneous spatial patterns of temporal variability in surface mass balance (SMB; e.g., Mémin et al, 2015; Martín-Espanõl et al, 2016; Shepherd et al, 2012; Boening et al, 2012). Complementing these remotely sensed observations, longer time series of SMB from ice cores (e.g., Frezzotti et al, 2013; Thomas et al, 2017, and references therein) suggest the presence of heterogeneous regional patterns of precipitation variability. Historical climate reanalysis (Dee et al, 2011) as well as regional models driven by this reanalysis (e.g., Van Wessem et al, 2014) further confirm the presence of spatial heterogeneity in recent historical Antarctic precipitation variability signals (Genthon et al, 2003; Genthon and Cosme, 2003; Wang et al, 2016)

Methods

Results

Discussion

Conclusion