Towards an understanding of dynamics of blue-ice moraines: A case study in the Grove Mountains, East Antarctica

Abstract

Knowledge regarding former behavior of the East Antarctic Ice Sheet (EAIS) is crucial for assessing global sea-level change and understanding the global climate system. Yet, it remains challenging to examine pre-Last Glacial Maximum (LGM) glacial histories of the EAIS due to the limitations of the traditional geologic records. Recent studies suggest that blue ice areas (BIAs) and associated deposits (e.g. supraglacial moraines) have a potential to overcome this problem. However, the relationship between blue-ice evolution and climate changes is not yet well examined. In this study, we investigate two types of BIAs in the Grove Mountains, EAIS, on the basis of surface exposure dating of erratic boulders and cobbles on blue-ice moraines at Mount Harding and Escarpment. Here, we present 27 new ages, including single (¹⁰Be; n = 10) and paired (¹⁰Be and ²⁶Al, n = 17) exposure-ages. The newly-obtained ages, along with previously-published ¹⁰Be data (n = 40), indicate that the studied BIAs have been relatively stagnant since the LGM, and that blue-ice moraines formed in a closed system are much older than those built in the absence of a barrier. Also, the compilation implies multiple phases of pre-LGM ice flow that corresponded to global cold periods. We suggest that there was likely a response of blue-ice evolution to Antarctic glaciations on orbital timescales.