Adding continental landmass at Arctic/Reduce Antarctica size - What would happen?

Question

So, I am developing a fictitious world that is very similar to our earth. Generally, most of the continents stay the same way they are (Maybe North America is split in two smaller continents), with slight alteration in shape and size. However, these are the major changes I am considering to add.

• First, there is a landmass the size of Australia slap into where Arctic Ocean is, right at the north pole.
• Second is Antarctica's landmass at the south pole is reduced to half of its size (Or remove as much as the landmass that Arctic gains, so it doesn't affect sea level significantly).

How would this affect climate overall? I heard that with landmass at the pole would make ice cap being able to form larger, so would an "Arctic continent" cause North America and Eurasia to become colder at the top from the bigger, more firmed ice cap?

And with smaller Antarctica, would that make southern hemisphere warmer due to more water surface area and less ice cap?

Answer 1

It depends a lot on what the geologic history of your world is.

On the one hand, the climatic history of the Cenozoic is almost entirely dependent on the history of Antarctica. You have a large landmass positioned directly over the South Pole where ice can build up on it, then you have the continent lose its connections to Australia and South America so there is a current circling around it (the circum-Antarctic current) to produce a natural cooling effect.

On the one hand, a smaller Antarctica by itself would mean that the ice age would not be as severe because there is less space for ice to build up on Antarctica. It also depends on how it separates from Australia/South America. If it's 50% the size, does it separate earlier, or does this mean it's positioned more northernly so the separation still happens in the Eocene and thus the continent may not be on top of the South Pole (and thus no circum-Antarctic current).

On the other hand, if there's a landmass at the North Pole, it means the same thing that happened IRL to Antarctica might happen there instead. It depends on if there is enough space for a circum-Arctic current to form around this new landmass, which would potentially cause an early ice age, which in turn would really change the evolutionary history of Earth.

Answer 2

The Northern hemisphere landmasses around the Arctic would likely be a bit warmer. Antarctica would still be largely unchanged, possibly slightly colder.

The climate is primarily driven by the sun and the atmosphere. The amount of energy being received by the planet isn't changing and neither is the composition of the atmosphere or the planet, thus the outcome is really that not much changes. There might be a slight increase in the planet's albedo (that's how reflective it is) if snow is more permanent in the north which would result in a slight increase in heat loss to space, but it's unlikely to make any notable difference as the region is reflective most of the time currently.

However, Antarctica is particularly cold because:

• It's high up and high altitude air is cold
• It's surrounded by water which stores a lot of thermal energy
• The angle of the incoming sunlight is very shallow

If none of these change, Antartica's cold climate also stays the same. It may get a little colder if it's surrounded by even more thermal storing water.

Meanwhile in the north, a continent the size of Australia would punch a pretty big chunk out of the Arctic ocean. The Arctic is currently cold, but not that cold, because:

• It's basically at sea level
• The angle of the incoming sunlight is very shallow
• It's surrounded by land, which will instead be providing heat rather than trying to take it

If you remove the thermal "battery" that is the arctic ocean, more energy that would've been stored up in that water will instead be in the land resulting in slightly higher temperatures there.