Thread: Two questions about arctic areas

1) I have heard that it never snows in Antarctica (very, very rarely actually). The snow that does fall, never melts.
What if it did actually snow frequently in Antarctica? I guess that every water molecule on earth would eventually get to that area, and it would snow and never melt. So Antarctica would be building up enormous ice and eventually taking up all the water in the world.
2) If Pangaea was located mostly in the arctic or antarctic areas (say the center of it was in the north or south pole), how would that have affected the evolution of life on earth up to today?
I wonder about this.

1) "What if" can be fun questions to think about. If all the water was getting locked up in a polar ice sheet I think it would eventually get to the point it would stop doing it.

Try not to waste too much time thinking about this one.
2) Our ancestors would have been much hairier than we are.

Snow and ice sublimate, which explains the shrinking ice cubes in an unused ice tray.

sublimate
v.
to cause to change directly from a solid to a gas, or from a gas to a solid, without becoming a liquid

To answer your first question, it snows an average of 6 in. a year in Antarctica. But is it not quite true that it never melts. The its sheer weight compresses and pushes the ice sheet out to the Ice shelves which float on the ocean. Ice breaks off these shelves forming ice bergs which float into warmer waters and melt. The snow that does fall in Antarctica is slowly returned to the ocean.

So, if it snowed more in Antarctica, this would be offset by faster growth in the ice shelves until the iceberg formation once again balanced things out.

The volume of sea water is approximately 13 billion cubic kilometeres. The area of Antarctica is approximately 14 millions square kilometres. Ignoring compression the snow would have to be almost 100 kilometres high on the continent to empty the oceans. It is obvious why that would be impossible, so the hypothetical problem - like the snow - evaporates¹.


1. I am well aware that snow does not evaporate, but - as jrmonroe has pointed out - it sublimes. However, I insist upon misusing the words because of the elegance of the resulting phrase².

2. Some of you will rightly point out that it is still ridiculous to talk about evaporation of snow. All that means is that we are going from the sublime to the ridiculous.

The sublimation rate would be proportional to the surface area. If you just piled the snow higher and deeper, that wouldn't increase the surface area, so I agree with the iceberg explanation.

Originally Posted by Harold14370

The sublimation rate would be proportional to the surface area. If you just piled the snow higher and deeper, that wouldn't increase the surface area, so I agree with the iceberg explanation.

But the relative scarcity of H2O molecules outside the icemass would change the vapour pressure differential and that should limit the process.

You would also soon hit the point where the weight of the ice would be more than the bearing strength of the ice and it would yield. It would creep outwards to escape the pressure and the surface area would increase.

Originally Posted by dan hunter

Originally Posted by Harold14370

The sublimation rate would be proportional to the surface area. If you just piled the snow higher and deeper, that wouldn't increase the surface area, so I agree with the iceberg explanation.

But the relative scarcity of H2O molecules outside the icemass would change the vapour pressure differential and that should limit the process.

Surely if there is less moisture in the atmosphere that should increase the sublimation rate.

Originally Posted by John Galt

Surely if there is less moisture in the atmosphere that should increase the sublimation rate.

I thought that was obvious, but yes, and that should limit the process of ice accumulation.

Sorry if I tend to be too brief in my comments.

Yes, brevity in this case created a grammatical flow in which sublimation was the process. Thank you for clarifying. (I like brevity, but I also like precision, )

So, does anybody else have anything to say about my second question?

2) If Pangaea was located mostly in the arctic or antarctic areas (say the center of it was in the north or south pole), how would that have affected the evolution of life on earth up to today?
I wonder about this.

Pangaea could not possibly have been located "mostly" at either of the poles. Just look at the relative sizes of those areas versus the continents you're thinking of.

The World	57,308,738 Sq. Miles (148,429,000 Sq. Km)	100%
Asia (including the Middle East)	17,212,000 Sq. Miles (44,579,000 Sq. Km)	30.0%
Africa	11,608,000 Sq. Miles (30,065,000 Sq. Km)	20.3%
North America	9,365,000 Sq. Miles (24,256,000 Sq. Km)	16.3%
South America	6,880,000 Sq. Miles (17,819,000 Sq. Km)	12.0%
Antarctica	5,100,000 Sq. Miles (13,209,000 Sq. Km)	8.9%
Europe	3,837,000 Sq. Miles (9,938,000 Sq. Km)	6.7%
Australia (plus Oceania)	2,968,000 Sq. Miles (7,687,000 Sq. Km)	5.2%

The 4 largest land masses add up to 78% of the total land mass, while Antarctica is less than 9%. The Arctic Ocean is much the same size as Antarctica, barely 5 & 1/2 million sq miles. So it also is equivalent to about 9% of the total land mass.

The best comparison for these purposes is North America. Large parts of Canada and Alaska are within the Arctic circle, above 66 degrees of latitude. While Mexico City is a mere 19 degrees of latitude above the equator.

Quite enough scope for evolution of just about anything and everything from polar bears to tropical frogs.

Most of the Antarctic ice is not moving towards the sea at all, but simply accumulated to such a high elevation that the air is too cold and thin to hold water vapor sufficient for snowfall. If there is mass escaping from the center of the cap it's probably mostly from melting and sub-ice river systems near the bottom.

Central Antarctica also has high winds that cause erosion.

http://www.amnh.org/education/resour...tic_winds.html

Thanks for your response. I actually suspected that was the case, adelady. So, if the center of gravity of pangaea was located at the north or south pole, the super-continent would have been large enough so the coast would be 30 degrees away from the equator, or even closer. So the most extreme thing is that everything living in the center of pangaea was arctic animals and life, and as you got closer to the coast, the climate was warmer and was represented so by the life. That actually sounds quite neat. Makes me kind of wish that was true. Is that what you meant by "Quite enough scope for evolution of just about anything and everything from polar bears to tropical frogs. "?

Is that what you meant by "Quite enough scope for evolution of just about anything and everything from polar bears to tropical frogs. "?

Near enough.

One mus also consider the Permian climate, which was in general warming from the end Carboniferou s iceage, and which resulted in warming and drying of the Pangean interior. https://en.wikipedia.org/wiki/Permian#Climate

The continental crusts are (most likely) constantly growing at the expense of the oceanic crust. So, comparing pangea to the present continents is a bit of a stretch.
true?
(literally and figuratively)

Not true. You are forgetting the major influence of erosion on continental mass.

Whether the total land mass was higher or lower back then doesn't matter much; it is clear that Pangaea was far too large to be located mostly in an arctic region.

Climate systems are generally more complex than that. For instance, one immediate problem with an entirely ice-covered supercontinent is that there are a severely limited number of viable carbon sinks, so over relatively short periods of time the climate will warm to the point where the ice melts.

Remember that there have been a number of times throughout geological time when there was no ice at the poles.

Originally Posted by drowsy turtle

Remember that there have been a number of times throughout geological time when there was no ice at the poles.

Even during cold periods there is still meltwater under the ice because the earth itself generates heat too.

Originally Posted by John Galt

we are going from the sublime to the ridiculous.

Groan.