One of the causes of the Antarctic melting is climate change, although the specific mechanism is not well known. In 2002, the collapse of the Larsen B ice shelf took glaciologists by surprise, making it a starting point to try to better understand this phenomenon. Understanding these mechanisms can help scientists predict the future of the ice and what role climate change might play in ice melting and breakup.
To understand these mechanisms, it requires methods to observe surface and subsurface melting. For example, the collapse of the Larsen B Ice Shelf in 2002 was preceded by a well-developed surface expression of meltwater, but the collapse of the Wilkins Ice Shelf in 2008 was preceded by water below the surface that enabled hydrofracture.
The objective of these methods was to determine if the ice-shelf flexure/fracture response was associated with surface water ponding and drainage, and to discover what seismic signals are associated with the water ponding and movement. To do that, scientists took seismograms over a 3-year period from 2015 to 2017, and conducted a ground-based study of surface meltwater features on the ablating portion of the McMurdo Ice Shelf (McMIS), Antarctica.
The scientists discovered a diurnal cycle of seismicity, consisting of hundreds of thousands of small ice quakes in an area where there is substantial subsurface melting. This cycle can be explained by thermally induced bending and fracture of a frozen surface supported by solar radiation, penetration and absorption.
These results suggest by studying seismic waves may be useful in monitoring subsurface melting in a manner that complements other ground-based methods, as well as remote sensing. As a cycle of seismicity occurs, the scientists can test it, idealizing a thermal model of the ice shelf and simulating the development of subsurface partial melt layers and thus predict the ice’s future.
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Source: MacAyeal, D. R., Banwell, A. F., Okal, E. A., Lin, J., Willis, I. C., Goodsell, B., & MacDonald, G. J. (2018). Diurnal seismicity cycle linked to subsurface melting on an ice shelf. Annals of Glaciology, 1-21. doi: 10.1017/aog.2018.29
Author: Hugo Guímaro
