A bizarre thought that occurred to me as I was looking at my globe the other day.
Suppose super aliens came along and used their space bat technology to rotate the Earth ninety degrees. Let’s say that the new south pole is at zero degrees and the equator (off the shore of Ghana) and the new north pole is 180 degrees and the equator (in the vicinity of Samoa). And then they start it spinning along its new axis. Assume they’re able to do this without breaking the planet.
How long would it take before the old ice caps melt in their new tropical locations and new ice caps form in the new polar regions? Would it be relatively quick, like in a year or two? Or would the accumulation of ice last for decades or more? Would it be a relatively simultaneous event, with the new ice caps forming as the old ones melted and the overall sea level remaining constant? Or would the new caps form first or the old ice caps melt first, causing the sea level to go up or down?
The formation of ice caps is not just due to the amount of insolation the poles get, but to a complex dynamic that depends on the conformation of land near the poles in combination with ocean currents. Even with the continents in their current positions, the northern ice caps have repeatedly melted and reformed over the past million years because of cyclic changes in the Earth’s orbit. The current cycle of northern glaciations may have been triggered about three million years ago by the closure of the Isthmus of Panama, which entirely rearranged oceanic circulation.
Even on the Equator, my guess is that the ice caps, especially Antarctica, would take at least centuries and more likely millenia to melt. The presence of large masses of ice in the tropics would undoubtedly have very large and unpredictable impacts on the global climate.
Assuming the new alignment of continents and ocean currents will permit the accumulation of ice caps, this will likely take tens of thousands of years to reach similar volumes as at present. (See here for the time line of past glaciations.) The ice cap of Antarctica, however, has been accumulating in some places for tens of millions of years.
The is no qualified answer to this question other than that it would take tens if not hundreds of millennia before the climate would return to anything like a stable equilibrium.
Of course, if your hypothetical aliens have such indistinguishable-from-magic technology to change the Earth’s rotational momentum without shredding the planet into bite-sized chuncks, controlling the climate should be a non-issue.
This is just a SWAG, but I would predict that with the poles located in open ocean, as the OP postulates, no new ice caps will be able to form. The modern ice caps are due in large part to the presence of land at the South Pole, and a relatively shallow, nearly enclosed ocean around the North Pole. Both of these configurations prevent or limit the transfer of heat from equatorial to polar regions via oceanic circulation. With a greatly enhanced capacity for heat exchange through ocean currents, I would predict the new polar regions would eventually become much warmer than the present ones are.
I’m thinking centuries is much too long. At a latitude of 45 degrees in the US, we go from 0 degrees F to 100 and back every year, with an angle change of only 47 degrees.
On Antarctica, there’s about 1.4E7 km^2, an average of 1.6 km deep, or 2.24E16 m^3 of ice = 2.24E+19 kg.
It takes 334 kJ/kg to melt ice, and throw in another 60 kJ/kg or so to warm it from around 0 to 32, and you need about 9E21 kJ.
The Sun gives 1000 Watts/m^2 or 8.64E6 Joules per day to a surface perpendicular to the Sun’s rays, so Antarctica will get about 1.2E21 joules per day.
So (check my numbers!) Antarctica will receive enough energy to melt the icecap in about 7500 days, or about 20 years. Yeah, snow is white, but when it starts melting, dirt collects on the surface, makng it absorb light better. Also, the calculations don’t count energy received elsewhere on Earth and transported to Antarctica by winds.
My guess is Antarctica will melt within a decade. The North pole ice is already unstable, and I’d guess it will be gone in weeks.
At the new pole near Ghana, I’d expect ice will start forming on land from snow within a year, but the other pole is in the open ocean, so there may be enough currents to keep it ice free indefinitely.
ETA: oops, forgot to account for night. Divide the energy indicent on Antarctica by 3 or 4. I’m still thinking on the order of a decade is abut right, though.
Well, the absorption issue is even more important. I’d divide by 10 or so for light reflected off - even dirty snow is pretty reflective. You could be 600-800 years at that point.
There’s another thing to consider. Antarctica has a high elevation in many areas. In fact, Wikipedia says it has the highest average elevation of any continent. There are mountain ranges that average 5-10,000 feet and peak at around 15,000. This is enough to maintain at least some glaciers permanently on the equator (such as the ones currently in Kenya). You’d no longer have an ice cap, obviously, but the ability to maintain a permanent glacier would surely slow down the erosion of the full ice cap.
You’ve also neglected to account for cloud cover. I suspect that that a large mass of ice in the tropics would cause condensation of warm moist air moving over it from the sea and be covered by clouds much of the time, limiting the effect of solar radiation.
The actual pole off Africa as specified by the OP is hundreds of miles offshore, with free circulation of water from the new equatorial regions. Snow may fall around the Gulf of Guinea in the winter, but it’s unlikely that there would be enough net accumulation in the winter to result in an ice cap. (After all, most of the land above the Arctic Circle at present is ice-free during the summer.)
Would it be possible to estimate this based on what percentage the Antarctic ice cap shrinks in volume each summer? In other words, if X% melts in two months, then the whole thing would melt in Y years given ongoing insolation.
Also, if we get more insolation, will I need better insulation?
That’s not going to tell you that much about the what will happen if the position of the ice cap changed. First off (as ZenBeam has indicated, there will be much greater input of solar radiation due to receiving the direct rays of the sun if Antarctica were in an equatorial position. But the actual rate of melting will be influenced by how air circulates over the ice cap and by cloud formation. Meltwater also could accelerate the flow of glaciers to the sea,
Regarding Fear Itself’s post, my reading of the OP is that the alignment of Earth’s axis of rotation relative to the sun would be the same as it is now, just that the orientation of the continents relative to the axis of rotation would be different.
If the Earth had an axis of rotation with an inclination like Uranus’s, that would be another new ball game.
