A 4‐decade record of elevation change of the Amery Ice Shelf, East Antarctica

Abstract

[ 1 ] We report on long-term surface elevation changes of the central Amery Ice Shelf (AIS) by comparing elevation records spanning 4decades . We use elevation records acquired with the following methods: optical leveling (1968)(1969); ERS radar altimetry (1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003); GPS (1995GPS ( -2006; and Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry (2003)(2004)(2005)(2006)(2007). We compute multidecadal elevation trend ( dh/ dt)v alues at crossovers between the leveling route and each of the GPS and ICESat tracks as well as shorter-period dh/ dt at ERS-ERS, GPS-GPS, and ICESat-ICESat crossovers. At GPS-leveling crossovers the mean long-term dh/ dt is 0.003 ma 1 ,and at ICESat-leveling crossovers the mean dh/ dt is +0.013 ma 1 ;n either trend is significantly different from zero. The data do, however,e xhibit variable trends: near-zero change between 1991 and mid-1996, then thickening to 2003, followed by thinning [2003][2004][2005][2006][2007], with 5y ear dh/ dt averages exceeding ±0.1 ma 1 .T he changes in dh/ dt pattern in mid-1996 and again in 2003 occur with unexpected speed. The ice shelf exhibits different dh/ dt patterns than does the surrounding grounded ice, suggesting that surface mass balance variations or longer-term variations in firn densification processes are unlikely to be major causes. We conclude that these observed multiyear elevation changes must be due to currently unexplained or presently poorly quantified phenomena involving surface or basal processes and/or ice dynamics. With the multidecadal stability of the AIS established, the short-term fluctuations that we observe suggests that for other ice shelves, observed strong dh/ dt signals over short time periods do not necessarily indicate ice shelf instability.

Validation of satellite altimetry by kinematic GNSS in central East Antarctica

“…With the help of such profiles Richter et al (2014a) have shown that the surface elevation around Vostok Station has been stable over the last decade, confirming the results of permanent GNSS observations (Richter et al, 2008(Richter et al, , 2014a. Such profiles acquired on snowmobiles provide accuracies of only a few centimetres (see also King et al, 2009;Siegfried et al, 2011) and are thus well suited for precise studies on local elevation and elevation changes. However, due to logistic reasons they usually cover only a very limited area and are therefore not considered here.…”

“…A comparison between kinematic GNSS profiles and satellite altimetry products requires consistency in the reference system used (King et al, 2009). ICESat (Schutz and Urban, 2014) and CryoSat-2 (Schrama et al, 2010) refer to ITRF08.…”

Antarctic Ice Sheet and Radar Altimetry: A Review

“…However, some discrepancies between studies in some places may be explained by the limitation of retrieving height variations due to the penetration of the altimetric radar wave in the snow pack. Such effect has been pointed out in the Amery ice shelf [112]. Densification processes yield also to critical error because it directly acts on the height surface and indirectly via change in snowpack characteristics.…”

“…For instance, altimeter observations from 1992 to 2001 over the Larsen ice shelf suggested a thinning of 0.27 m/yr [111]. Now, longer time series analysis, for instance over the Amery ice shelf, exhibit short-term fluctuations so that one cannot conclude that short time period signal necessarily indicates ice shelf instability [112].…”

Antarctica-to-Western Australia Liquid Freshwater Shipments Using Stauber Bags in a Paternoster-Like Transfer System: Inaugurating a Southern Ocean Antidrought Action Sea-Lane

“…Figure 2) will be converted to basal meltwater, whereas ,50% will be converted to calving icebergs from the Amery Ice Shelf's edge at the head of Prydz Bay, ultimately entering the Southern Ocean (Barbara et al, 2010;King et al, 2009;Lei et al, 2010;Vaz and Lennon., 1996). The Amery Ice Shelf's estimated net ice mass loss, approximately 14.2 billion tonnes in the form of icebergs (Williams, Warner, and Budd, 2002), could markedly increase during the 21st century.…”