Pictured in the top picture are the remains of what had a few days earlier been some of the ice rings discussed in an earlier blog. The sharp edges of the discrete portions of the ice-ring debris have all but melted away and the relic rings are barely discernible from the surrounding ice. That the ice sheet has experienced repeated cycles of warming and cooling is evident from the interesting star shaped feature at the background of this picture. The radial cracking from what had been a small circular hole is typical of the tensile crack patterns associated with the hoop tensile stress concentrations experienced around a hole when a sheet undergoes cooling. With the cracks filling with water and partially turning to ice these radial cracks would not be closed during the subsequent warming phase. Having undergone repeated cycles of cooling and warming these radial cracks have grown to become characteristic features of the ice sheet. Another example is shown in the lower picture.
Similar thermal ratchet cracking can be observed in sheets of asphalt pavement, and related morphologies and mechanism have been described for the development of periglacial features at high latitudes and altitudes and especially in regions of permafrost. But I will return to some of these possibly analogous forms of behaviour in later blogs.
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