Ice sheets may melt rapidly in response to distant volcanoes

This is the finding from a new research paper entitled ‘Enhanced ice sheet melting driven by volcanic eruptions during the last deglaciation.’

Another very recently published paper (‘Very large release of mostly volcanic carbon during the Palaeocene–Eocene Thermal Maximum’) says something similar:
‘The Palaeocene–Eocene Thermal Maximum [PETM], was a global warming event that occurred about 56 million years ago, and is commonly thought to have been driven primarily by the destabilization of carbon from surface sedimentary reservoirs such as methane hydrates. However, it remains controversial whether such reservoirs were indeed the source of the carbon that drove the warming…[We] identify volcanism associated with the North Atlantic Igneous Province rather than carbon from a surface reservoir, as the main driver of the PETM. This finding implies that climate-driven amplification of organic carbon feedbacks probably played only a minor part in driving the event.’

So two papers saying volcanic ash on the ice, not carbon dioxide in the air, was the main player in PETM deglaciation.
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Volcanic eruptions have been known to cool the global climate, but they can also exacerbate the melting of ice sheets, according to a paper published today in Nature Communications, says Phys.org.

Researchers who analyzed ice cores and meltwater deposits found that ancient eruptions caused immediate and significant melting of the ice sheet that covered much of northern Europe at the end of the last ice age, some 12,000 to 13,000 years ago.

“Over a time span of 1,000 years, we found that volcanic eruptions generally correspond with enhanced ice sheet melting within a year or so,” says lead author Francesco Muschitiello, who completed the research as a postdoctoral fellow at Columbia University’s Lamont-Doherty Earth Observatory.

These weren’t volcanoes erupting on or near the ice sheet, but located a thousand miles away in some cases. The eruptions heaved huge clouds of ash into the sky, and when the ash fell on the ice sheet, its darker color made the ice absorb more solar heat than usual.

“We know that if you have darker ice, you decrease the reflectance and it melts more quickly. It’s basic science,” says Muschitiello. “But no one so far has been able to demonstrate this direct link between volcanism and ice melting when it comes to ancient climates.”

The discovery comes from the cross-sections of deposits, called glacial varves, most of which had been collected in the 1980s and 1990s. Varves are the layered sediments that form when meltwater below an ice sheet routes large amounts of debris into lakes near the sheet’s edge. Like the rings of a tree, the layers of a glacial varve tell the story of each year’s conditions; a thicker layer indicates more melting, since there would have been a higher volume of water to carry the sediment.

The team also compared the varves to cores from the Greenland ice sheet, whose layers contain a record of ancient atmospheric conditions. Testing of those layers for sulfates revealed which years experienced explosive volcanic eruptions, which tend to release large amounts of ash. Matching up the ice layers with varve layers from the same time periods, the team found that years with explosive volcanic activity corresponded to thicker varve layers, indicating more melting of the northern European ice sheet.

Continued here.