2
$\begingroup$

I don't fully understand the mechanisms behind an ice cap that contains all the water in the oceans. Just to be specific, I have a planet that resembles Mars, i.e. desert at the equator, ice at poles. I want the equator to be hot, but the ice caps to contain the entirety of the oceans.

I really like super detailed information, so I want to know, how would the oceans migrate towards the poles and eventually get stuck there forever, with the equator still managing to be hot?

$\endgroup$
2
  • $\begingroup$ Ice sheets by their very nature have a tendency to collect water, since precipitation often does not get released back into the environment. $\endgroup$ – John Apr 20 '20 at 16:27
  • 1
    $\begingroup$ This is unlikely to work, because ice flows under pressure, and so glaciers & ice caps move. They would flow equator-wards, as for instance the ice sheets did during the last glaciation. (Leaving behind glacier-carved basins that would become the Great Lakes, Finger Lakes, &c.) The only way to keep them from flowing far enough to melt would be to have high ridges of terrain somewhere in the mid-latitudes. You might look at the Columbia Icefield for an example in miniature: ttps://en.wikipedia.org/wiki/Columbia_Icefield $\endgroup$ – jamesqf Apr 20 '20 at 18:28
1
$\begingroup$

On Mars the lack of surface water everywhere but the poles is a result of all liquid water evaporating in the low pressure atmosphere. Mars' water didn't migrate towards the poles. It would be more accurate to say that the ice at the poles is all that's left of Mars' water.

You could also get water only at the poles of a planet if your landmasses are arranged around your equator.

Keep in mind that it isn't a requirement that deserts are hot. Deserts are defined by their lack of precipitation. Antarctica is considered a desert due to the low amount of snowfall. If there is a low amount of precipitation planetwide it is plausible enough that you could have ice ant the poles and a transition to a hot desert at the equator.

$\endgroup$
1
  • 1
    $\begingroup$ I think this is a great example of how people like me overthink things sometimes. I was thinking of applying the inverse square law and calculating the average distribution of watts in a given area, or using a sinusoidal graph to figure out equatorial and polar temperatures. When I read paragraph 2 of this answer, however, I had to read it several times before I started crying in joy (not literally.) Thanks for the super simple answer that solves all my problems. $\endgroup$ – user75058 Apr 20 '20 at 19:24
0
$\begingroup$

High rotation speed (shorter days) will result in a more oblate shape. Add to it a zero axial tilt, a circular orbit (no seasons) and place the orbit just a tad closer to the star to have hotter equatorial temperatures.

  1. the more oblate shape will result in a shallow angle of incidence of light closer to the poles

  2. the lack of seasons will guarantee the establishment of a regular weather, in which the ice at poles will reflect most of the incident light (positive feedback in maintaining colder poles)

  3. a higher rotation speed almost guarantees the tectonics will happen mainly in the direction of the rotation. The fracture zones are a bit more likely to run in lines parallel with the equator and the zones of subduction along the meridians - which means mainly mountain ranges running North-South, have higher altitudes and likely deflecting a larger amount of moisture towards the poles. Pretty much the same with oceanic currents.

If you have a smaller amount of surface water, you'll get your dessert equator all water at poles soonish (in astronomical time scales)

$\endgroup$
0
$\begingroup$

Ice caps form whenever the yearly balance between solid water accumulation and water melting is shifted toward accumulation. It can happen at the poles but also on high enough mountains, where glaciers form.

In order to close the water cycle, water has to flow back to the oceans, But ice stops the water where the ice formed. Consequently if more water remains trapped as ice, there will be less returning to the ocean and the ice cover will increase.

Since this depends on the local conditions, it is perfectly plausible that local ice accumulation and a hot equator coexist on the same planet. For your info, on Earth mount Kilimanjaro has a glacier despite being located quite close to the elevator.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy