Tuesday, January 05, 2016
Greenland icecap discovery
I don't know much about glaciology but nor do glaciologists, it seems. Ice lenses (isolated masses of ice) are familiar in rock and soil but glaciologists seem to have discovereed only recently that they exist in glacial firn (semi-compacted snow) as well. And they have figured a way to see that as promoting the Greenie scare of sea-level rise, as they would of course. That's a great basis for a big juicy new research grant.
Most interesting, however is their discovery that ice lenses are becoming more massive in firn. But what does that tell us? What makes water into ice? COLD, low temperatures. So if more ice is forming lately that means that it must be getting colder at the site concerned. Have they discovered global cooling? Seems like it!
I like the last sentence below
The rate at which water is released from the Greenland ice sheet is accelerating, according to a multinational team of scientists.
Studying the upper layers of snow on the island's glaciers, they found the compacted snowy frosting on the ice cap, called firn, is losing its ability to absorb meltwater.
This is due to the formation of 'ice lenses' beneath the surface, indicating that the sponge-like ability of the firn to soak up melting surface water is being lost.
Experts fear this could lead to increased release of the meltwater into the oceans.
Firn can be up to 260ft (80 metres) thick and is an integral part of the Greenland ice sheet, which is second only to Antarctica in size and is up to 14,000ft (4.3km) thick.
It contains ice formed up to 100,000 years ago, created by snow that gradually built up and compacted.
Snow is regularly deposited on top of the ice cap, and previous studies have shown that snowfall is increasing as a result of climate change.
The new study, from a team of Danish, American, and Swiss scientists, shows that current atmospheric warming is changing the firn layer and allowing meltwater to be released faster than previously seen.
'Basically our research shows that the firn reacts fast to a changing climate,' said Horst Machguth, lead author of the study by the University of Zurich.
'Its ability to limit mass loss of the ice sheet by retaining meltwater could be smaller than previously assumed.'
The researchers travelled to Greenland to investigate the impact of recent atmospheric warming on the structure of near-surface snow and ice layers.
Over the course of three expeditions, they mapped the structure of firn layers with a radar unit and drilled 66ft-deep (20 metre) cores into the top layers of ice, including sites where cores had been drilled 15 to 20 years ago.
Earlier research has shown that the firn layer acts similar to a sponge.
It stores meltwater seeping down from the surface in what are referred to as 'ice lenses’ - pockets between soil and rock.
Comparison of the new and old cores revealed substantially more ice lenses than in the past, the study published in Nature Climate Change explained.
Cores at lower elevations showed 'exceptional amounts' of meltwater which formed a 'surprisingly massive' ice layer close to the surface.
‘It appears that the intensive and repeated entry of meltwater formed numerous ice lenses, which ultimately hindered percolation of further meltwater’, said Dirk van As, a co-author of the study from the Geological Survey in Denmark and Greenland.
As a result, many small lenses join into an ice layer several metres thick, acting like a lid beneath the surface of the snow.
This means that surface meltwater is diverted into new rivers at or just below the surface, travelling to the sea more quickly and contributing to sea level rise.
Mike MacFerrin of the University of Colorado at Boulder said: 'In contrast to storing meltwater in porous firn, this mechanism increases runoff from the ice sheet.'
He said the process has never been seen before in Greenland and that 'the total extent of this ice lid capping the ice sheet firn remains unknown.'
'For this reason, the amount of additional ice sheet runoff associated with this newly observed process cannot yet be quantified.'
Posted by John J. Ray (M.A.; Ph.D.).