Bob McDonald: Why Losing Glaciers Matters

23 05 2014


By Bob McDonald, Quirks & Quarks
The Earth is losing its ice faster than scientists have predicted. The loss of the white stuff is changing the colour of the planet, accelerating global warming, and could have serious consequences for low lying cities.
Maps of the world usually show Greenland and Antarctica as vast areas of white, which is pretty much all that explorers found when they crossed the enormous ice sheets, and what you see looking down from modern aircraft.
Now, thanks to ice-penetrating radar instruments carried by some of those planes, as well as satellite data, the geography of the land beneath the white is becoming visible. It turns out that the ice is hiding deep valleys and tall mountain peaks as rugged as the Rocky Mountains.
Some of those glacial valleys are below sea level, and that has scientists concerned.
Last week, a report described how warm ocean currents are undercutting the West Antarctic Ice Sheet, which actually lies on ground below sea level. This, scientists think, means the ice sheet has passed the point of no return and will inevitably collapse as water encroaches and tears away at the massive ice sheet that represents nearly 10 per cent of the ice on Earth.
This week another report showed that some glaciers in Greenland are also sitting in sub-sea-level valleys. So as the toes of those glaciers retreat, the sea water will follow them up the valleys, causing them to erode more quickly than if the valley floors were higher and drier.
Yet another report showed that glaciers in Alaska and British Columbia are retreating faster than predicted. In fact, all glaciers on Vancouver Island will be completely gone in just 25 years.
This loss of ice is having a multitude of effects on the entire planet.  It’s changing the colour of the Earth, or in astronomical terms, the planet’s albedo. That’s a measure of how much sunlight a planet absorbs compared to how much it reflects back into space. White reflects sunlight, so glaciers and ice sheets have been keeping the Earth  cooler than it would be otherwise.
As ice disappears, it is replaced by dark land or sea water, which absorbs sunlight and turns it into heat. This process accelerates in a feedback loop that warms  the planet faster as the area of the ice gets smaller and smaller.
This heating effect is in addition to the heating caused by our carbon emissions into the atmosphere.
Glaciers grounded on land, such as those in Greenland and Antarctica, are acting like ice cubes dropped into a glass full of water. If the glass is full to the brim, adding an ice cube will cause the water to spill over the rim because the ice came from outside the glass and is displacing the water. If there is already ice in the glass, the water level doesn’t rise as the ice melts because it’s already floating.
That’s why the melting of the ice covering the Arctic Ocean will not contribute to sea level rise, while the glaciers on land could raise the oceans many metres. (The Arctic ice does have a huge albedo effect because the area of dark sea water it covers is so vast.)
Fortunately, the rising of the seas will take decades, so coastal cities can prepare for higher waters, especially during storms.
Finally, in Canada, glaciers are the source of fresh water for many rivers such as the Bow and North Saskatchewan, which carry that water from the mountains into our agricultural areas. Their loss means we will have to rely more on ground water and aquifers, which are already being pumped heavily for irrigation and fracking natural gas.
Glaciers are more than symbols of great white wilderness. They are a planetary phenomenon, the canaries in the coal mine of climate change and warehouses of our most precious resource, water. There’s more at stake with their loss than just pretty scenery.





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