See larger image here.
The melt season in Greenland starts every spring or early summer. The melting white snow and ice that accumulated on the ice sheet surface over the winter transforms to a blue meltwater. The melt season also exposes the old snow and ice, darkening the ice sheet surface. This old ice can be as much as 30 percent less reflective than younger snow and ice. This dark ice absorbs more energy from the sun, which leads to even more melting and a further darkening of the Greenland ice sheet surface. This is called the albedo effect, a feedback loop, and it threatens the world’s coast lines with sea level rise.
See larger image here.
NASA’s Earth Observatory reports:
“This year we had some really early season melt events that kick-started things,” said Allen Pope, a scientist at the National Snow & Ice Data Center (NSIDC). According to an NSIDC blog post, the ice sheet saw three extreme spikes in melt by June 19. As a result, the pace of melting so far is ahead of the past three seasons, but behind the record melt year of 2012.
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Surface melt can directly contribute to sea level rise via runoff. It can also force its way through crevasses to the base of a glacier, temporarily speeding up ice flow and indirectly contributing to sea level rise. Also, ponding of meltwater can “darken” the ice sheet’s surface and lead to further melting.
“All these processes tend to accelerate further melting through so-called positive feedback mechanisms,” Tedesco said. “The more melting you have, the more melting will increase in a way that melting feeds on itself. I call this melting cannibalism.”
Not every melt season follows the same progression. Pope notes that almost no lake water was present in mid-June in 2014 and 2015, then volumes of meltwater peaked each year by mid-July.
Melt ponds and rivers that form on the ice surface are not only indicators of melting, but they also can provide a glimpse of how fast glaciers will calve ice into the ocean. These melt ponds drain via a Moulin ( a vertical shaft through miles deep ice to the bedrock) or a crevasse. Once the water gushes to the bottom it flows between the ice and the bedrock lubricating the base of the glacier, allowing it to flow more smoothly over the land surface and to shed ice more quickly at the coasts. It is not simple melting from climate change that puts the Greenland ice sheet in danger, it is that climate change causes the dynamics of the ice sheet to change allowing it to flow rapidly to the sea.
Climate News Network has a fascinating article unveiling new research showing that melting in Greenland is also accelerating due to waves crashing on the coastline.
The waves that crash on the coastline send tiny seismic shudders through the rock, and seismic wave velocity changes with rock density. So the reasoning is that changes in the mass of ice pressing down on the rocks could be revealed by changes in the speed of the waves through the rock.
Ocean waves generate signals that sensors can pick up continuously, and Dr Prieto says: “They happen 24 hours a day, seven days a week, and they generate a very small signal, which we generally don’t feel. But very precise seismic sensors can feel these waves everywhere in the world. Even in the middle of continents, you can see these ocean effects.”
The scientists recorded seismic data from a small network of sensors on Greenland’s west coast between January 2012 and January 2014, and could detect changes in wave velocity of as little as 1%.
They recorded very large slowdowns in 2012, compared to 2013, and these matched satellite observations of abnormally large melting that year, which suggests that climate science now has another way of looking at changes in the ice.
The article states that ice is accumulating in the center of the island. The center is at higher altitude and it stays far below freezing point. The article notes that 40% of the ice cover rarely experiences melting.
Thom Hartmann interviews Dr. Jason Box, who urges caution on a methane meltdown. Although a methane meltdown is high risk, the data does not support it at this time.
From Climate Denial Crock of the Week:
There is indeed reason for concern, and nobody is more concerned than scientists like Dr. Box who follow the issue, and importantly, have children.
Yes, large amounts of methane are frozen in undersea arctic permafrost, and a large release of that powerful greenhouse gas would indeed mean, as Dr. Box famously tweeted two years ago, that we would be “effed”. Indeed, methane seeps have been observed in the arctic ocean, but the area has not been well enough studied to tell how many, over what area, and whether these are new, or background phenomena that have been ongoing for some time.
But, data does not show a Methane melt-down currently in progress, despite what you may have seen on various heavy breathing you-tubes and websites from the “imminent human extinction” crowd. Still, the risk is real, and represents a possible global high impact event that needs more study, which it is starting to get, with serious resources being deployed by several Arctic nations, as Dr. Box relates above.