The sea is a big place.
Societies are concerned with pollution in rivers, because the river is immediate and relatively small. So societies arrange elaborate sewerage systems to pump it out to sea, because the sea is a big place. Problem solved.
Similarly when ice melts from land, it flows into the sea. The sea level rises, but how much? If the sea is a big place and the ice melt is small, what’s the problem?
When scientists talk about sea level rises, they talk mainly about projections. This article in Nature being a prime example.
The article discusses several modelling scenarios and concludes,
In one scenario, which assumes that carbon emissions rise slightly above the goals set by the 2015 Paris climate agreement — but still see a considerable reduction — sea levels would increase by at least 0.52 metres by 2100, compared with 2006, the Arctic report says. Under a business-as-usual scenario, the minimum increase would be 0.74 metres.
While this is informative it relies heavily on the estimates, assumptions and methodologies of the modelling scenarios, none of which are explained. It can appear to the layman that the sea is a big place and that sea level rises are likely to be small.
Attempts are rarely if ever made to benchmark the models with extremes, which is a standard way of testing a model to ensure its behaviour is appropriate and results are sensible and it is something the scientists and/or media never appear to discuss or report.
For example consider a jar of 100 jelly beans on the back shelf of a car, where every time the car goes over a bump in the road jelly beans fall out. If this situation was modelled and the results showed that over a distance of 100 kilometres of simulated travel 120 jelly beans fell out, the model would clearly be inaccurate.
So what are the melting and rising limits? These can easily be assessed and presented below is the sea level rise that could be expected if the entire Greenland ice sheet melted.
The Greenland ice sheet data is taken from Weather Underground and listed below
The ice sheet covers 85% of the island of Greenland (this is all on land and therefore the ice melt is considered 100% transfer from land to sea – rather than a % conversion of sea ice to sea water)
The average height f the ice sheet is 2.3 km
The surface area of Greenland is 2,166,086 km^2
Therefore the ice sheet area is 2,166,086 x 0.85 = 1,841,173 km^2
and the ice sheet volume is 1,841,173 x 2.3 = 4,234,697 km^3
or, considering the difference in density between ice (917 kg/m^3) and sea water (1030 kg/m^3)
an equivalent of 4,234,697 x (0.917 / 1.030) = 3,770,113 km^3
The surface area water on the earth is 361,132,000 km^2
So, if one considers the equivalent volume of sea water from the Greenland ice sheet spread over the water area of Earth (ignoring the increase in water area due to coastal flooding, which is considered relatively small) Then the rise in sea level for the complete melt of the Greenland ice sheet is determined
3,770,113 / 361,132,100 = 0.010 km, or 10m
Which is about the height of the thirty foot wave which headed this article.
It is noted that Greenland is not the only place where there is land ice.
The next question about melting ice sheets, is once they start melting, what is going to stop them?