Abstract
Quantifying the mass balance of the Antarctic Ice Sheet (AIS), and the resulting sea level rise, requires an understanding of inter-annual variability and associated causal mechanisms. Very few studies have been exploring the influence of climate anomalies on the AIS and only a vague estimate of its impact is available. Changes to the ice sheet are quantified using observations from space-borne altimetry and gravimetry missions. We use data from Envisat (2002 to 2010) and Gravity Recovery And Climate Experiment (GRACE) (2002 to 2016) missions to estimate monthly elevation changes and mass changes, respectively. Similar estimates of the changes are made using weather variables (surface mass balance (SMB) and temperature) from a regional climate model (RACMO2.3p2) as inputs to a firn compaction (FC) model. Elevation changes estimated from different techniques are in good agreement with each other across the AIS especially in West Antarctica, Antarctic Peninsula, and along the coasts of East Antarctica. Inter-annual height change patterns are then extracted using for the first time an empirical mode decomposition followed by a principal component analysis to investigate for influences of climate anomalies on the AIS. Investigating the inter-annual signals in these regions revealed a sub-4-year periodic signal in the height change patterns. El Niño Southern Oscillation (ENSO) is a climate anomaly that alters, among other parameters, moisture transport, sea surface temperature, precipitation, in and around the AIS at similar frequency by alternating between warm and cold conditions. This periodic behavior in the height change patterns is altered in the Antarctic Pacific (AP) sector, possibly by the influence of multiple climate drivers, like the Amundsen Sea Low (ASL) and the Southern Annular Mode (SAM). Height change anomaly also appears to traverse eastwards from Coats Land to Pine Island Glacier (PIG) regions passing through Dronning Maud Land (DML) and Wilkes Land (WL) in 6 to 8 years. This is indicative of climate anomaly traversal due to the Antarctic Circumpolar Wave (ACW). Altogether, inter-annual variability in the SMB of the AIS is found to be modulated by multiple competing climate anomalies.
Highlights
The Antarctic ice sheet (AIS) is the largest reservoir of fresh water on Earth and has a potential to raise global sea level by 58 m in the worst case, which is if it were to melt completely [1]
Fluctuations associated to El Niño Southern Oscillation (ENSO) are usually quantified using the Southern Oscillation Index (SOI), which provides a measure of the strength of the related events [45]
Apart from the influence of the ENSO, regions in the Pacific sector are subject to other climate drivers, such as the Southern Annular Mode (SAM) and the Amundsen Sea Low (ASL) [62,63]
Summary
The Antarctic ice sheet (AIS) is the largest reservoir of fresh water on Earth and has a potential to raise global sea level by 58 m in the worst case, which is if it were to melt completely [1]. Similar anomalies were detected in surface mass and elevation change estimated from space-borne geodetic techniques which had a periodicity of 4 to 6 years and circle the AIS in 9 to 10 years [14]. These anomalies may be attributed to ENSO contributions over the AIS or the Antarctic circumpolar wave (ACW), a large scale covarying oceanic and atmospheric anomaly propagating eastward across the Southern. Global observations of water and ice mass redistribution in the Earth system at monthly to decadal time scales from GRACE missions played a critical role in understanding the climate system and investigating its changes [27].
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