What if the ice were to melt ?

The melting of the Antarctic ice is a topic of conversation that every now and then becomes front-page news. We are talking here of the ice of the continental glacier, not the marine ice which, when it melts, does not bring about any variation in sea level (the Archimedes principle).

The fear of seeing cities like London, Hamburg, New York, Antwerp or Amsterdam disappear under the dual effect of the melting of the polar ice and the rise in the global level of the oceans has never been shared by scientists...

It must be said that the gradual warming of the climate that everybody is talking about today is not of a kind to calm the fears of those who already imagine that the ice continent is in the process of melting and that the oceans are in the process of invading the lower areas of Earth and of inundating some of the largest metropolises of the world: London, Hamburg, New York, Antwerp and Amsterdam. This alarmist view of affairs has never been shared by scientists.

What are the reports saying ?

They have in the first instance explained that the first visible effect of the warming, even minimal, of the atmosphere would be a significant increase in the concentration of the latter's water vapour and perhaps of overall precipitation. Which would lead ipso facto to an increased snow cover on the Antarctic continental glaciers and therefore, instead of melting, they would in fact become thicker.

They have then estimated, from simultaneous analysis of the published data from climatology, hydrography and glaciology in the course of the century, that, if the level of the sea has effectively risen during this period, (for a centimetre value between 10 and 25) there is nothing to indicate that this was as result of the melting of the Antarctic or Greenland continental glaciers. In the latest report of the IPCC (Intergovernmental Panel on Climate Change, 1995), a comparative table (1) shows that if scientific forecasts effectively predict an average rise in sea level from now to the year 2100 of about 60 centimetres (between 26 and 80 according to the various studies) the contributing factors to this are distributed as follows (taking 66 centimetres of elevation as the departure hypothesis) :

To what is the negative role attributed?

To the fact that there is no efficient method in existence at this time for calculating what glaciologists call the mass balance of the continent. By that they mean that in the current state of research, including deep boreholes, one can only affirm that the contribution of snowfall may or may not counterbalance the melting of a part of the glaciers.

What the report does mention, however - and this is going in the direction of the alarmists - is a certain instability in the western ice cap; the movement of the glaciers would seem be quicker there than elsewhere, the ice shelves would be for the most anchored on rock piles, the area of contact between the ice and the earth's surface (the bedrock) would be wet and the seeping of the glaciers into the Ross Sea would be occurring in a more continuous manner.

This view of things is however not shared by all and a polemic opposes the people who claim that this instability could, in the event of a significant warming of the climate, become even more accentuated and finish by provoking the overall fractionising of the western ice cap, and the people that rely on other figures (such as the growth of certain glaciers, for example,) to say that the western ice cap will never ever dislocate itself to go and melt in the water and increase the level of the ocean. Let those that fear the worst be reassured: the melting of the Antarctic ice and the disappearance of cities like Tokyo or New York are events that should be catalogued in the series of improbable catastrophic scenarios.

 

(1) IPCC : Intergovernmental Panel on Climatic Change, 1995, p 381