Two of the more frightening predictions scientists make about climate change have just taken a step closer to becoming reality. Question: what do current sea levels and Europe's mild climate have in common? Answer: they both may depend on Greenland's huge ice mass staying where it is.
Unfortunately, Greenland's ice is on the move, and no longer at a glacial pace. One large glacier has tripled its flow rate over the last year or so, and its neighbors are not far behind. If the scientists watching this are right, we might see a lot more fresh water getting dumped in the North Atlantic a lot sooner than expected.
This could be very bad. More details below the flip.
Dr. Gordon Hamilton,
speaking this week at the
American Geophysical Union Fall meeting, discussed what is believed might be
the fastest moving glacier on the planet:
Kangerdlugssuaq Glacier on the east coast of Greenland has been clocked using GPS equipment and satellites to be
flowing at a rate of 14km per year.
It is also losing mass extremely fast, with its front end retreating 5km back up its fjord this year alone.
The glacier "drains" about 4% of the ice sheet, dumping tens of cubic km of fresh water in the North Atlantic.
This gives it significant influence not just on global sea level rise but on the system of ocean circulation which drives through the Arctic.
"We've seen a 5km retreat of the terminus, we've see an almost 300% acceleration in the flow speed and we've seen about a 100m thinning of the glacier - all occurring in the last one or so years," said Dr Gordon Hamilton, of the Climate Change Institute at the University of Maine.
"These are very dramatic changes."
Changes which, unfortunately, are not confined to Kangerdlugssuaq:
Helheim Glacier, just to the south of Kangerdlugssuaq, is exhibiting similar changed behaviour. It is flowing only slightly slower at 12km per year - the equivalent of half a football field a day.
Hamilton thinks a couple of factors may be triggering the quick melt.
The observed recent increase in summer surface melting on the Greenland Ice Sheet is producing large quantities of liquid water which, if it percolates down to the base of the glacier, can lubricate its flow over rocks towards the ocean.
And if that same warming is bringing higher-temperature sea waters into contact with the front of Kangerdlugssuaq and Helheim, this could explain their rapid retreat.
If other large glaciers in the region are seen to go the same way, it could begin to "pull the plug" on Greenland, said Dr Hamilton.
"The model predictions for sea level rise do not include the effects of rapid changes in ice dynamics," he added.
"We're seeing now that this component might be extremely important. And what it suggests is that the predictions for both the rate and the timing for sea level rise in the next few decades will be largely underestimated."
Hamilton is not the only one concerned about Greenland's ice:
In 2001 NASA scientists published a major study based on observations by satellite and aircraft.
It concluded that the margins of the Greenland ice-sheet were dropping in height at a rate of roughly one metre a year.
Now, amid some of the most hostile conditions anywhere on the planet, Carl Boggild [Danish scientist with the Geological Survey of Denmark and Greenland] and his team have recorded falls as dramatic as 10 metres a year - in places the ice is dropping at a rate of one metre a month.<snip>
Dr Boggild and his colleagues, studying the physics of how the air and ice relate, conclude that as much as 55% of the melting is attributable to warming in the air.<snip>
"We can say for certain that the rate of melting has increased and we can say for certain that the height of the ice-sheet is falling, even allowing for increased ice-flow.
"There is no doubt that something very major is happening here."
So why is this so important? Most people rarely even think about Greenland - a desolately cold place with a tiny population that doesn't exactly project a heavy presence on the world stage. However, as any climatologist could tell you, Greenland is incredibly important.
First, Greenland has a LOT of ice. 85% of Greenland is covered by ice, which is up to two miles thick in places. Its ice sheet is one of the two great ice bodies on Earth, the other being on Antarctica. The melting of Greenland's ice sheet would raise oceans by 7 meters (23 feet), swamping cities like Los Angeles, New York, London and many others. But even partial melting, resulting in less than a meter rise, could do damage that would make New Orleans after Katrina seem like the good old days. Large parts of Bangladesh would be underwater, for example, and many oceanic islands would cease to be inhabitable or cease to exist altogether. The small South Pacific nation of Tuvalu has already formally asked Australia and New Zealand to accept its people as they evacuate their sinking home.
In addition to having a lot of ice, Greenland is strategically positioned in the North Atlantic. I will take a minute to explain why its location is so important.
The global ocean circulation known as the conveyor belt is driven by the sinking of cooled water off Greenland's southeast coast. Basically, warm, salty water is carried northwards from the Gulf of Mexico by the Gulf Stream, cooling as it travels. Once this water reaches the North Atlantic off of Greenland, it cools further and sinks (since cold salty water is denser than both warm salty water and cold but slightly fresher water). This sinking water is the main driving force behind the conveyor belt circulation, which cycles through all the Earth's oceans (except the Arctic) before it returns to the North Atlantic. As it returns, it carries warm water up along the coast of Africa and ends up back where it started, where water sinks and the cycle begins anew. The combination of the Gulf stream and the conveyor belt (which are interdependent) makes the North Atlantic warmer than it would be otherwise, which warms winds heading towards Europe and keeps sea ice from encroaching as far south as it would otherwise. For this reason, this circulation system is widely credited for helping keep the North Atlantic and NW Europe 9 C warmer than the average for their latitudes. As a tangible illustration, just look at a map and note that Milan is roughly at the same latitude as Montreal, and Paris as Newfoundland.
Now, back to why Greenland's position is important. The sinking water which drives the global conveyor belt depends on the salty water sinking, and this occurs right off Greenland's coast. If this salty water becomes significantly diluted with fresh water, say from Greenland's rapidly melting ice cover, scientists predict that it could fail to sink. If this happens, this global circulation system could slow down or even shut off. This, in turn, could result in Europe being plunged into a much colder climate in just decades or less, and also have climatic repercussions in other areas of the world. A weakening in this circulation system is already in evidence.
Now, climatologists will be the first to tell you that they are not certain whether or when this might occur. However, most agree that a dramatic change in the global conveyor belt is a very serious concern and a real possibility.
And if Greenland's ice mass begins to pour into the ocean at a much faster rate than anticipated, the possibility of submerged coastlines and an icy Europe may be a lot closer than previously thought.