Previous GRACE-derived ice mass trends and accelerations have almost entirely been based on an assumption that the residuals to a regression model (including also semi-annual, annual and tidal aliasing terms) are not serially correlated. We consider ice mass change time series for Antarctica and show that significant autocorrelation is, in fact, present. We examine power-law and autoregressive models and compare them to those that assume white (uncorrelated) noise. The data do not let us separate autoregressive and power-law models but both indicate that white noise uncertainties need to be scaled up by a factor of up to 4 for accelerations and 6 for linear rates, depending on length of observations and location. For the whole of Antarctica, East Antarctica and West Antarctica the scale factors are 1.5, 1.5 and 2.2 respectively for the trends and, for the accelerations, 1.5, 1.5 and 2.1. Substantially lower scale-factors are required for offshore time series, suggesting much of the time-correlation is related to continental mass changes. Despite the higher uncertainties, we find significant (2-sigma) accelerations over much of West Antarctica (overall increasing mass loss) and Dronning Maud Land (increasing mass gain) as well as a marginally significant acceleration for the ice sheet as a whole (increasing mass loss).

Item Type:	Refereed Article
Keywords:	GRACE, ice mass balance, Antarctica, acceleration, stochastic modelling, confidence intervals
Research Division:	Engineering
Research Group:	Geomatic Engineering
Research Field:	Geodesy
Objective Division:	Environment
Objective Group:	Climate and Climate Change
Objective Field:	Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts)
Author:	King, MA (Professor Matt King)
ID Code:	93184
Year Published:	2014
Funding Support:	Australian Research Council (FT110100207)
Web of Science® Times Cited:	26
Deposited By:	Geography and Environmental Studies
Deposited On:	2014-07-15
Last Modified:	2017-10-24
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