Heat flow from Earth's interior is generally thought to be insignificant in comparison with that from the Sun or the atmosphere, but in regions permanently blanketed by ice the heat rising from the depths of the Earth can play an important role, according to a paper just published in the journal Nature Geoscience.
A group led by researchers at the German Helmholtz Institute in Potsdam, Berlin, find that geothermal heat flux influences the internal thermal structure of the Greenland ice sheets, seen in the distribution of basal meltwater. They claim that Earth's internal heat must be accounted for when planning deep ice drilling campaigns or using ice melt data in climate reconstructions.
Earth's rocky shell, the lithosphere, varies in thickness through Greenland, for reasons that are currently not well understood. In some parts the lithosphere is very thick indeed, but in others it thins, allowing greater heat flow from the depths of Earth.
The researchers used modelling to find that the oldest and thickest part of the Greenland Ice Sheet is strongly influenced by heat flow from the deep Earth. They found that the geothermal heat flux in central Greenland increases from west to east due to thinning of the lithosphere in eastern Greenland.
The variations in thickness of the rocky Earth drive strong regional variations in basal ice conditions in Greenland. Because the lithospheric thickness is very varied across Greenland they find that in some areas there is rapid basal melting but nearby the base of the ice appears extremely cold.
Their findings demonstrate that the solid Earth structure, even at depths of many tens of kilometers, plays an important part in influencing the dynamics of surface processes.
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