Climate Mini-Exploration: Shifted Poles

Hey everyone, a short one today: Throughout these posts I've been using Earth's geography mostly just for demonstration purposes. The idea hasn't been so much to show what Earth specifically would look like under different conditions, but rather to demonstrate more generally how these conditions might influence Earth-like planets, with Earth's topography serving as a convenient point of reference. As such I generally haven't been too concerned with scenarios like Earth with a retrograde rotation or different arrangements of continents, because these don't really show any fundamental difference in the state and mechanisms of the climate independent of Earth's particular topography, and so don't often carry lessons we could carry into predicting the climates of other worlds (though where other people have already modelled retrograde Earth or climates of Earth's past I'm perfectly willing to pull their data and make climate maps, and in the future I might run some models with "toy" topography like land covering all of one hemisphere or only between certain latitudes, where we might be able to derive some general lessons on how land distribution impacts climate).

But I was recently contacted by someone who did want to see what the climate of Earth with shifted continents was like and was willing to commission me for the modelling time, and expressed a wish that the results should be made available on the blog, which is a fairly delightful task to be commissioned for. Let's take look at the results:

For the first one, I shifted the Earth's axis by 90°, placing the north pole at to sit at (0, 0) latitude and longitude, just off the African coast. Note that for these models I haven't attempted to replace the glacial topography of Greenland and Antarctica with any sort of ice-free reconstruction of the actual land surface, so they appear here with high, cool internal plateaus despite sitting near the equator, though this isn't actually too far off from what we might expect for them after isostatic rebound (and really a lot of regions would probably have substantially different topography if Earth had always had this orientation; much of the northern coastlines of Eurasia and North America have been shaped by glacial action and even long-term patterns of mantle convection and continent drift may be influenced in some way by the planet's rotational axis).

I also haven't altered any other parameters like axial tilt or CO levels from the baseline, but with no large glaciated landmasses, the overall climate is about 3 °C warmer than our Earth and there are no permanent ice caps. There are some clear winners and losers here in terms of overall hospitability and biodiversity: North America and Antarctica sport vast rainforests while Asia and South America have dried out; Australia has ended up a tad cooler and wetter; Europe sports much the same range of climates as in real life but shuffled around; and Africa has lost its arid belts but substantially cooled down, and might be expected to support a single vast boreal forest.

There are some interesting patterns over Asia I think are worth highlighting.

The large, equator-spanning continent experiences pretty strong temperature swings, which leads to large shifts in wind patterns and the tropical rain belt; a monsoon-type wind pattern, which we've seen before but usually think about in terms of drawing moisture from an equatorial ocean onto a subtropical landmass. Here, the landmass is equatorial and the ocean (the Arctic) lies to the east, but we still see a pattern of wetter summers and intensely dry winters as the winds off that ocean shift direction.

 Meanwhile, a patch of the west coast remains conspicuously wet year-round, despite appearing to lie in the rainshadow of the Himalayas if we assume generally west-blowing tropical winds; to some extent this is helped by the monsoon pattern (as it brings winds from the north and south rather than exclusively from the east across the mountains) but it's also likely a result of lee cyclogenesis; the tendency for large mountain ranges with winds blowing directly across them to form a low-pressure zone on their lee (downwind) side, which can form cyclones that draw in moisture from nearby seas.

For the second model, we were looking to see what the impact of a large polar continent would be, so placed the north pole at (45° N, 80° E) latitude and longitude, near the China-Kazakhstan border, in order to place most of Asia in the Arctic circle. Oddly enough, this one only came out a tad cooler than the last model, and despite my attempts to encourage glaciers, they haven't spread out from Tibet (a trick I've been experimenting with a bit has been to start models with 1 meter of initial global ice cover, which helps slow its initial warming; for our Earth with its true arrangement of continents this does a better job of replicating the true ice cover, but more generally there seems to be a fairly narrow range of parameters where this works without the ice just promptly melting away anyway, like here, or failing to melt at all and locking the planet into a snowball state). A more complex approach of balancing at a lower CO level first and then warming might be more successful, but I may be overthinking things here.

At any rate this has given us a rather more eclectic mix of continental and cool temperate climates, and Asia is still starkly cold; most of the continent drops to under -40 °C in winter and thaws for only 3 months, but during that brief summer temperatures can still rise to over 20 °C, allowing for a brief, intense growing season. I ponder if this might be regarded as something of a cold world, despite being similar in global temperature to the last case and warmer than Earth, simply because so much of the habitable area is near the poles. This is one of the points I've been trying to emphasize a bit across these explorations, that the nature of a world's surface environments aren't always directly linked to simple global parameters.

That'll do for today, then. I may do more mini-explorations like this in the future, for quick model runs that don't necessarily merit the deep analysis or rigor of the main explorations, but for now work continues on the next main post, on the impact of eccentricity (and I'm also still working on the main series, I'm just a bit held up by probably getting a bit too obsessive about perfecting the process for generating the topography).

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