Abstract
ABSTRACTWe present results of a regional comparative study of surface mass changes from 2004 to 2008 based on Gravity Recovery and Climate Experiment (GRACE), The Ice, Cloud and Land Elevation Satellite (ICESat) and CHINARE observations over the Lambert Glacier/Amery Ice Shelf system (LAS). Estimation of the ICESat mass change rates benefitted from the density measurements along the CHINARE traverse and a spatial density adjustment method for reducing the effect of spatial density variations. In the high-elevation inland region, a positive trend was estimated from both ICESat and GRACE data, which is in line with the CHINARE accumulation measurements. In the coastal region, there were areas with high level accumulations in both ICESat and GRACE trend maps. In many high flow-speed glacier areas, negative mass change rates may be caused by dynamic ice flow discharges that have surpassed the snow accumulation. Overall, the mass change rate estimate in the LAS of 2004–2008 from the GRACE, ICESat and CHINARE data is 5.41 ± 4.59 Gt a−1, indicating a balanced to slightly positive mass trend. Along with other published results, this suggests that a longer-term positive mass trend in the LAS may have slowed in recent years.
Highlights
Monitoring of mass changes in Antarctica has become an important research topic because melting of the Antarctic ice sheet (AIS) and the resulting discharge contribute significantly to changes in the sea level (Bamber and others, 2009b; Cazenave and Llovel, 2010; Shepherd and others, 2012; Vaughan and others, 2013)
The contribution of changes in the polar ice sheet to rising sea levels displays an accelerating trend compared with changes in the other two major contributors: continental glaciers and expansion of seawater caused by higher temperatures (Domingues and others, 2008; Chen and others, 2009; Cazenave and Llovel, 2010; Rignot and others, 2011a; Zwally and Giovinetto, 2011)
Much of the spatial noise in the surface mass change fields derived from the Gravity Recovery and Climate Experiment (GRACE) data, which are represented as north/south-oriented stripes, is caused by correlations among estimated spherical harmonics, with extra noise increasing with the spherical harmonic degree (Swenson and Wahr, 2006)
Summary
Monitoring of mass changes in Antarctica has become an important research topic because melting of the Antarctic ice sheet (AIS) and the resulting discharge contribute significantly to changes in the sea level (Bamber and others, 2009b; Cazenave and Llovel, 2010; Shepherd and others, 2012; Vaughan and others, 2013). A reconciled estimate of the ice-sheet mass balance using a variety of remote sensing and in situ observations, including GRACE and ICESat data, was reported by Shepherd and others (2012). Rignot and others (2008) used InSAR data and snow accumulation data to estimate the Antarctic mass change in 2000, while Yu and others (2010) performed another study for the LAS in 2000 based on RADARSAT images, snow accumulation and in situ observations. King and others (2012) estimated an Antarctic mass balance based on GRACE data from 2002 to 2010 using the W12a GIA model (a glacial isostatic adjustment (GIA) model), and we recalculated an estimated regional LAS trend of 36 ± 11 Gt a−1.
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