A global warming primer

GLACIERS AND ICE CAPS

There are two kinds of ice mass in the world, alpine type glaciers, the 'rivers of ice', and ice caps or ice sheets, mainly those of Greenland and Antarctica. The climate alarmists have a false model for both!

Basically they believe that the ice is sliding downhill, lubricated by meltwater. With global warming there is more meltwater and the ice slides ever faster. James Hansen even claimed that all the ice sheets could slide into the sea in a few decades!

Alpine glaciers do not slide on a lubricated base. This was the idea of De Saussure in 1779, but experiments with sticks across a glacier by Agassiz and Forbes in 1845 showed the middle flows faster than the edges. They were clear that this shows we do not have a rigid mass of ice sliding on its base. In reality the lower part flows plastically carrying a rigid upper part that cracks up making crevasses.

Ice caps cannot possibly slide into the sea because they are in kilometres-deep basins and would have to 'slide' uphill. Furthermore the deep ice cores show a succession of annual layers of snow accumulation back to 760,000 years. In all that time there has been no melting at the surface, despite times when the temperature was higher than that of today.

But the weight of the icecap eventually becomes sufficient to exceed the yield stress of ice, and the lower part of the ice starts to flow, assisted by geothermal heat. This is in no way related to the temperature at the surface, and of course not related in any way to CO₂.

In Greenland the icecap ice flows out through gaps in the mountain rim, and the outflow glaciers have many of the properties of alpine glaciers.

Antarctica has similar behaviour, though more complex. Remember Antarctica is about 50% bigger than Europe, and there are some mountain ranges under the ice.

Also note that the Greenland icecap is about 3 million years old and the Antarctic icecap is about 33 million old. They are not simply responding in unison to global temperatures.

Glaciers and icecaps have a budget, with accumulation, flow and melting or breaking off (icebergs). It takes hundreds or thousands of years for ice to flow from source to end, so the position of the end today is not just the result of today's climate, but of precipitation long ago.

Every break-up of an ice shelf to produce an ice berg is treated by the alarmists as a signal of global warming. But for glaciers that reach the sea this is the normal process at the terminus. The icecaps never did just flow for ever until they reached the equator!

Tourists flock to see the Hubbard Glacier in Alaska where frequent breaking at the ice front produces icebergs the size of a 7-story building. It seems an impressive loss, but the Hubbard glacier has been advancing at 25 metres per year since it was first measured in 1895. In 1999 it was even reported to be advancing at 2m per day.

Today the icecaps are increasing in thickness, and many glaciers are advancing, though some are in retreat. The pattern is complex and certainly not a simple response to global warming or man-made carbon dioxide since 1945..