Collapse of the Greenland Glaciers
The Greenland glaciers that cover the island contain enough water to raise sea level twenty feet, or seven meters. It was once thought (and that was only six years ago) that the glaciers would be self-sustaining even in a warming world because of size and so on.
We now know that 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.
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.
When this happens much of this mountain of water will flow into the sea. 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.
It would seem we are on the verge of a major tipping point in climate change, if we have not already reached it. 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. Where now 6 billion people? See Footprints #3.
One reason is that 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 Antarctica’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.
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.
And elsewhere… a few typical examples
As oceans warm so the area covered by nutrient-poor water increases, making the oceans less friendly for algae or plankton. This reduces the amount of carbon the seas can absorb. The threshold for the almost complete failure of algae is about 500 ppm of carbon. At our present rate of growth we will reach this level in about 40 years.
Reduction in Antarctic sea ice contributed to the 80% decline in krill since 1970. Krill is the foundation of the southern food chain. A temperature rise of 1.8°F would cause extensive coral bleaching. This will destroy critical fish nurseries in the Caribbean and Southeast Asia.
The glaciers of the Tibetan plateau are vanishing by 50% every decade. They contain a sixth of the world's total ice and feed many of Asia's greatest rivers - including the Yangtze, the Indus, the Ganges, the Brahmaputra, the Mekong and the Yellow River. Such ice loss has profound implications for China, India and Pakistan which are dependant on rivers fed by them that will turn into trickles. Drinking and irrigation water will disappear. A billion people will be affected from the drying up of the rivers, increased droughts and sandstorms.
In 1983 the five main glaciers in Columbia were expected to last at least 300 years. Recent measurements suggest they may disappear within 15, denying cities water and putting populations and food supplies at risk in these desert areas.
Snow and rainfall in South America and the Caribbean are becoming less predictable and more extreme. The 2005 drought in the Amazon basin was the worst since records began.To the top