Tears in Antarctic Ice (ABSTRACT)

 

Recently, due heavily to global climate change, there has been a net loss of ice on and around Antarctica. While part of the ice loss is driven by basal melting, most of it – about 75% — is driven by iceberg calving (Bassis, 2008). Iceberg calving is a process whereby large chunks of ice break off ice shelves and float away, eventually melting into the ocean. The process of iceberg calving begins with rift propagation. Rifts are tears in ice shelves that penetrate vertically through the entire ice shelf, and they start from one horizontal end of the ice shelf and lengthen towards another end.

antarctic_ice_lossFigure 1: Change in Antarctica mass variation since 2002   (source: climate.nasa.gov)

While rift propagation and subsequent iceberg calving is a frequent process, there is still a lot of uncertainty about what specific mechanism(s) drive(s) rift propagation. One study analyzed wind speeds, tidal amplitudes, and sea-ice fraction, but was unable to correlate any of those with rift propagation rates (Bassis, 2008). Yet another potential factor that could explain rift propagation is less related to climate change and more related to tectonic activities – the process of so-called “icequakes” (Heeszel, 2014).

This project focuses on the Amery Ice Shelf in East Antarctica (or the “AIS”). The AIS is a particularly valuable Antarctic ice shelf to study, as it buttresses – or physically supports – the Lambert Glacier catchment basin, which accounts for nearly 1/6 of the total mass of the East Antarctic Ice Sheet (Fricker, 2009). And the AIS is much further north than most Antarctic ice shelves (about 69 degrees South), so it is at the Antarctic forefront of global climate change (Fricker, 2009).

Antarctica_map

Figure 2: Map of Antarctica, with the Amery Ice Shelf circled in red (source: nsidc.org)

2002_Mar_09

Figure 3: Close-up view of the Amery Ice Shelf from 2002 (source: nsidc.org)

It has been a while since the AIS calved its last iceberg – likely not since around 1963 or 1964, when an iceberg the size of about 10,000 km2 calved off (Bassis, 2005). Now, however, there are some major AIS rifts that have been propagating for years, and these will be the main focus of this project. Specifically, AIS rift propagation rates will be compared against other mechanisms (mainly ocean temperatures, but also others potentially) to determine how impactful certain mechanisms are on the process of rift propagation.

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Sources:

Bassis, J.N., Coleman, R., Fricker, H.A., and Minster, J.B., 2005, Episodic propagation of a rift on the Amery Ice Shelf, East Antarctica; Geophysical Research Letters, v. 32.

Bassis, J.N., Fricker, H.A., Coleman, R., and Minster, J.-B., 2008, An investigation into the forces that drive ice-shelf rift propagation on the Amery Ice Shelf, East Antarctica: Journal of Geology, v. 54, p. 17-27.

Fricker, H.A., 2009, Mapping the grounding zone of the Amery Ice Shelf, East Antarctica using InSAR, MODIS and ICESat: Antarctic Science, v. 21.

Heeszel, D.S., Fricker, H.A., Bassis, J.N., O’Neel, S., and Walter, F., 2014, Seismicity within a propagating ice shelf rift: the relationship between icequake locations and ice shelf structure: Journal of Geophysical Research: Earth Surface, p. 731-744.

Scambos, T., J. Bohlander, and B. Raup. 1996. Images of Antarctic Ice Shelves. Amery Ice Shelf. Boulder, Colorado USA: National Snow and Ice Data Center.. http://dx.doi.org/10.7265/N5NC5Z4N.

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