Abstract
AbstractWe investigated the evolution of two major rifts cutting across Mertz Glacier Tongue, East Antarctica, using a combination of satellite images and 60 day sets of GPS data from two stations deployed either side of the western rift in 2007. The eastern rift began to open in the early 1990s, and the western rift initiated in 2002 in conjunction with the collision of a large iceberg with the tongue. Velocity time series derived from the 2007 GPS data exhibited strong variations at tidal periods modulated by sea-surface height and sea-surface slope and reproduced here with a conceptually simple model. We found that opening of the western rift in 2002 leads to a dramatic change in behavior of the tongue as the large range in velocity (700–2400 m a−1) observed in 2000 was largely reduced (1075–1225 m a−1) in 2007. Opening of the western rift decoupled the glacier from the transverse loading on the tongue driven by east–west tidal circulation. This loading previously induced time-varying lateral drag, which caused the large velocity range. Our results suggest changes in the mechanical behavior of an ice tongue impact the dynamics of the outlet glacier system and should be considered in longer-term mass-balance evaluations.
Highlights
In order to assess the mass budget of the Antarctic ice sheet into the future, the role of ice shelves in regulating the discharge from the ice sheet must be addressed, in addition to the processes that influence the evolution of those ice shelves and the associated ice streams (De Angelis and Skvarca, 2003; Rignot and others, 2004; Scambos and others, 2004)
In the case of Mertz Glacier Tongue, we previously investigated the evolution of the main rift leading up to the calving that occurred in February 2010, using GPS measurements acquired during the November 2007 field program (Lescarmontier and others, 2012)
The western ice stream bends left as it crosses the grounding line into Mertz Glacier Tongue and retains the orthogonal orientation of the features all the way to Mertz Glacier Tongue front
Summary
In order to assess the mass budget of the Antarctic ice sheet into the future, the role of ice shelves in regulating the discharge from the ice sheet must be addressed, in addition to the processes that influence the evolution of those ice shelves and the associated ice streams (De Angelis and Skvarca, 2003; Rignot and others, 2004; Scambos and others, 2004). The bathymetry of the continental shelf near Mertz Glacier is characterized by the presence of a deep valley running parallel to the coast, known as George V Basin, where the water depth reaches 1000–1400 m. Icebergs typically ground in the shallow waters, around 300 m deep, over the continental shelf near Mertz Glacier Tongue. Southeast and east of the George V Basin, icebergs often ground near the coast and may cause calving of ice shelves due to impact with ice tongues. These icebergs may originate from local sources or from as far east as the Ross Sea
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