400,000 years ago Greenland’s massive continent-covering glacier vanished in a global warming event that tracks the course of the Earth’s present day climate heating event. Once the earth cooled again, Greenland’s ice sheet returned—until now.
Greenland is melting once again. When Greenland’s melting glaciers lose large chunks of ice, it’s a violent process. Last year, for instance, scientists documented that gigantic glacial earthquakes are triggered by the rolling and tumbling of billion-ton icebergs as they break away and hit the glaciers to which they once belonged – hard.
But large masses of ice falling into the waters of Greenland’s fjords do something else, too. Depending on the mass of ice lost and the particular configuration of the water and the fjord into which it surges, these events can also create destructive waves, some 50 meters (164 feet) in height.
Researchers measuring this massive wave suggested “This is like a bulldozer at 30 meters a second, going into this water, and pushing it forward”.
Greenland’s 200 or so outlet glaciers have always calved and lost ice, so what makes this behavior noteworthy?
Over the last few years, things have been speeding up—and rapidly so. The edges of glacier faces are melting fast due to warmer temperatures. This melting of the edges facilitates large-facing sheets of ice to build up before calving off, hence the massive waves. But there is an even bigger problem. Not only are the edges melting fast, but the surface melt is seeping through the ice to lubricate the junction between the glacier and the rock underneath. This is the unexpected factor that has turned scientific attention onto this escalating problem, seen as both massive waves and new rivers of fresh melt water cutting through the glacier.
It appears that the Greenland ice is shot through with crevices, tunnels and faults through which the melting upper surface can penetrate right through the glacier, and threaten to break the attachment between the ice and the rock base.
Already twenty-one of the great glacial masses are moving seawards eight times faster than ten years ago and disintegrating three times faster than in the preceding five years, often triggering earthquakes and ‘tsunami’ sized waves in the process.
The latest US Navy survey suggests there will be no sea ice left in the Arctic summer by 2016. This has been unprecedented within the entire record of human species.
Is this the date we have to look forward to?
The Greenland, Alaskan and West Antarctic ice sheets together hold about 25% of the fresh water on the planet. The effects of the collapse of either ice sheet would be huge. Once you lost one of these ice sheets, there’s no putting it back for thousands of years, if ever.
If they disintegrate, sea level could rise nearly 20 meters, possibly in only one decade. This would swamp most cities and ports, as well a much of the best agricultural land.
Arctic temperatures are increasing at an average of 0.66°C per decade. If the global average is 2°C, then the arctic will be 4°C, and more over Greenland. The final deglaciation of Greenland will be triggered above 2.7°C local. In less than 30 years, there has been a 40% loss of arctic sea ice.
Similarly the western Antarctic’s mass is disappearing at about 240 cubic kilometers per year. Depletion of ozone is adding to this problem for it has encouraged hotter winds to flow across the Antarctic, and this is already impacting on the Larsen ice mass.
The global impact of 2°C rise in the graph shows a 55 meter rise. This is more than occurred in the Pliocene Era 3 million years ago when the northern hemisphere was up to 8 degrees hotter and the southern a couple of degrees colder.
The rate accelerated in 2004. It holds 70% of Earth’s freshwater.
The consequences of sea-level rise
If the seas rise a modest 400mm 22% of coastal wetlands will be lost, and more when we include the likely human reaction to that change. A one meter sea-level rise would affect 6 million people in Egypt, with some 15% of agricultural land lost, 13 million in Bangladesh with 16% of the national rice production lost, and 72 million in China with tens of thousands of hectares of agricultural land. See Footnotes #2.
The anticipated 7 meter sea rise will be far worse, and will directly affect 300-1,000 million people, some 15% of the world’s population. The ricochet will be far-reaching and incalculable.
Sea Level Rise over last century The decline of ice around the north pole seems to have sharply accelerated since 2003, raising fears that the region may have passed one of the major tipping points. As the warmer weather melts the ice it drives temperatures higher because the dark water absorbs nearly all the sun’s radiation. This could make global warming quickly run out of control.