Ice caps

Ice caps are masses of ice covering up to 50,000 km2 of land, usually, but not always, on top of mountains.

Anything larger is called an ice sheet and we are most familiar with those at the poles.

At school we were told that the poles are cold because of the angle of the Earth's orbit around the sun that keeps each pole in shadow for half the year. And when the sun does shine for almost perpetual summer days the rays are oblique and low in energy.

As a consequence polar ice varies in size with the seasons. The issue for climate change is the long-term trend.

Arctic ice at the North Pole forms over the Arctic Ocean and can be 4m thick where it does not melt in summer. National Snow and Ice Data Centre in the US claims a recent decadal decline in Arctic ice of 4.2%.

Antarctic ice at the South Pole forms over the Antarctic continent covers 146 million km2 and contains roughly 70% of the earth's fresh water.

This large ice mass has increased slightly over recent decades.

Climate change effects

The logic is that a warming world will see ice melting thanks to more energy, more heat and less cold.

Unfortunately the complexities of energy transfers in the atmosphere and oceans confound such simple explanations.

The Arctic is moving to a cooler cycle even if the seasonal summer melts are larger in volume and extent.

Ice is accumulating in Antarctica at the same time as some mountain ice sheets are shrinking.

It will take major warming to overturn a planetary phenomenon where the sun is weak at the poles.

So the polar ice will stay with us for some time yet.


Ice caps are a good example of how climate change can be spun.

It is easy enough to point to melting, especially in the summer months, as being evidence for global warming and then to stretch this to  evidence for abrupt climate change.

Except that when ice melts and creates meltwater flows this can be both catastrophic and essential. A large proportion of the worlds irrigated agriculture relies on meltwater. So for this effect melting is good so long as it happens slowly.

And this is true for many climate change effects. The drama of them can hide advantageous effects and even opportunity

The reality is that none of the climate change impacts are truly catastrophic. They are disruptive and locally can be acute but with thought and foresight, adaptation options eist for all of them. Even sea level rise.

What happens to ice is the same. 

There will be problems that will require significant mitigation and adaptation effort to fix, but they are fixable — we can look at flood prevention measures, plan not to build in low lying districts and think carefully about how we grow crops on the back of meltwater.

Stopping the ice from melting in the first place is another thing entirely.

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