Is Pine Island Glacier the Weak Underbelly of the West Antarctic Ice Sheet?

Guest post by Mauri Pelto

AntarcMapPeltoIt is popularly understood that glaciologists consider West Antarctica the biggest source of uncertainty in sea level projections. The base of the 3000-m thick West Antarctic Ice Sheet (WAIS) – unlike the much larger East Antarctic Ice Sheet – lies below sea level, and it has been recognized for a long time that this means it has the potential to change very rapidly. Most of the grounded West Antarctic ice sheet drains into the floating Ross and Ronne-Filchner ice shelves, but a significant fraction also drains into the much smaller Pine Island Glacier. Glaciologists are paying very close attention to Pine Island Glacier (“PIG” on map, right) and nearby Thwaites Glacier. In the following guest post, Mauri Pelto explains why.

In science there are instances when a specific mechanism is understood and a hypothesis posed based on an understanding of the processes involved, prior to the initiation or observation of the those processes. An excellent example is the determination by Molina and Rowland (1974) that CFC’s will lead to losses in stratospheric ozone. The full truth of their understanding of the process was not revealed until the Antarctic ozone hole was reported in 1985 by Farman et al.

A different example, from the same time period, was the 1978 publication by the late John Mercer, Ohio State U., who argued that a major deglaciation of the West Antarctic Ice Sheet (WAIS) may be in progress within 50 years. This conclusion was based on the fact that the WAIS margin was ringed with stabilizing ice shelves, and that much of the ice sheet is grounded below sea level. The loss of ice shelves — Mercer proposed — would allow the ice sheet to thin, grounding lines to retreat and the ice sheet to disintegrate via calving. This is a much faster means of losing mass than melting in place. Mercer further commented that the loss of ice shelves on the Antarctic Peninsula, as has since been observed, would be an indicator that this process of ice sheet loss due to global warming was underway.

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