Flow re-organization of the East Antarctic ice sheet across glacial cycles




Cavitte, Marie Genevieve P.

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Constraining the stability of the East Antarctic Ice Sheet (EAIS) over glacial-interglacial timescales is important to both understand its sea level contributions in the past and predict its future contributions in a warming world. Constraining how fast the EAIS can deliver ice to the ocean is as important as how much. Total volume fluctuations can be inferred through the use of nunatak exposure ages and ice core dating as well as through ice sheet modeling reconstructions of the Antarctic Ice Sheet as a whole. However, the EAIS’s ice volume fluctuations over long timescales such as 100-kyr glacial cycles and short spatial scales such as single ice flow catchment are less well known. I establish a method for dating internal reflections from ice-penetrating radar data between the Vostok and Dome C ice core sites, and determine the associated uncertainties in depth and age. I constrain the stability of two catchments of the EAIS through the use of internal stratigraphy from ice-penetrating radar, dated using correlated ice cores, combined with 1D ice flow models to reconstruct past accumulation rates. Here, I show that the ice catchment at the South Pole was highly active during the last glacial maximum while the ice dome/divide at Dome C was fairly stable during the entire last glacial cycle. Enhanced flow reaching South Pole implies the EAIS’s interior is much more susceptible to changes than previously thought. The absence of flow re-organization at Dome C for the last glacial maximum in contrast to South Pole shows that flow re-organization can vary from catchment to catchment. In addition, the stability of the Dome C region for the last 128 kyrs is highly promising for the retrieval of 1.5 million-year-old ice. 1D inversions of the deep radar isochrones interpreted above the subglacial relief of the Little Dome C (LDC) surface dome, ~30 km south of Dome C, predict several 1.5 million-year-old ice drilling sites. However, the complicated basal radar internal stratigraphy above the LDC and the presence of subglacial lakes complicate the task of choosing an ice core drill site. The EAIS-wide internal stratigraphy from the extensive modern ice-penetrating radar data now available over the EAIS have improved our understanding of its configuration and stability on multiple scales and timescales, and provide a foundation for understanding East Antarctica’s future role in global sea level change.


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