UK weather forecast: Britain to be hit with torrential rain for THREE more days
At least it isn’t snow.
I’ve been continuing with the development of my glaciation simulation model. It’s a model of heat flow up a geological column from the hot centre of the Earth through its surface and out into space. At the surface of the Earth the heat flows are very low: only about 70 milliWatts per square metre. But over many thousands of years this small heat flow adds up to sufficient heat to melt overlying sheets of snow and ice several kilometres deep.
I’ve now extended the model to have 18 radial geological columns at 5 degree intervals from the equator to the north pole.
And I’ve then been having snow fall continuously on all these continental geological columns at the same rate (about 10 centimetres per year) for tens of thousands of years.
The sequence of images below show the build-up of snow on the surface of the Earth at all latitudes from 0 to 90ºN over a period of 280,000 years, and the gradual heating of the surface rocks beneath the snow, and the consequent melting of the overlying snow. In the equatorial regions where snow doesn’t settle, the surface rocks cool slowly.
In this sequence snow never settles for long south of about latitude 30ºN, but at higher latitudes the snow settles and deepens quite rapidly. Surface rock temperatures rise highest beneath the deepest snow. Maximum snow depth at 90ºN reaches about 1200 metres.
The snow at the base of all these snow sheets is continually slowly melting, but because there’s snow continually falling on top of the snow sheets, they initially gradually get deeper, until the surface rocks beneath the snow have warmed up enough to melt the overlying snow faster than the rate at which new snow is being added, at which point the snow sheets begin to slowly thin.
So over 280,000 years the snow sheets first grow, and then dwindle back down to almost nothing. And that is the same sort of order of magnitude as the last 100,000 year long ice age, that only ended 12,000 years ago.
The snow sheets in this model extend as far south as 30ºN, which is the latitude of Cairo in Egypt. Most discussions of past northern hemisphere glaciations seldom show them extending further south than about 50ºN in Europe. Evidence of these ice sheets is found in unstratified gravel produced by the friction of ice sheets on rocks beneath. But there must need to be a considerable depth (several kilometres) of ice for this to happen, and it’s unlikely that relatively thin layers of snow will produce similar moraines and drumlins, or indeed any of them at all. And in my model the snow is mostly only about 100 metres deep between latitudes of 30ºN to 50ºN.
I’ve been wondering whether these relatively shallow snow sheets extended over the entirety of Europe, as well as Spain and Italy and Greece, and that the reason human civilisation first emerged in Egypt and Mesopotamia and only later in Greece and Rome is that for a long time the latter remained under snow as the glaciers gradually retreated northwards.
I’m hoping next to get almost all the snow to melt and produce an almost completely snow-free interglacial period during which the hot surface rocks gradually cool back down, eventually allowing a new period of glaciation to commence.
In the meantime I’m hoping that all the CO2 that’s being added to the Earth’s atmosphere will raise air temperatures enough to forestall the re-glaciation of the northern hemisphere any time soon. It’s one of my future projects to try to find out if CO2 can do this.