Could nuclear fallout melt the ice caps and cause an accelerated sea level rise?

Question

I'm writing a story where a total nuclear WWIII occurs in the early 21st century. in a matter of minutes all of the world's nuclear powers unleashed their entire arsenals on each other in an event known as the Second Wave. Although it caused an unbelievable amount of damage in the short term (crop failure, a nuclear winter, annihilating our biggest cities, etc.), the biggest impact of it all came far after the end of the war.

After the initial nuclear blasts scattered fallout into our atmosphere, much of it fell on top of our ice caps as snow in the nuclear winter that followed. Over the course of the next 50 years, the radiation it created heated up the snow and ice; destabilizing the ice caps and accelerating sea level rise to levels that (at our current rate) we thought we wouldn't see until a few hundred years from now (most of the Earth's original coastlines are submerged, the Midwest is severely flooded by the expanded Mississippi River, the entire Florida peninsula is completely gone from the map, etc.).

Could a scenario like this really occur, and if so, how much damage could an event like this actually cause?

Answer 1

No. There's nothing like enough energy in nuclear fallout to melt the ice caps.

Answer 2

No.

as Mike Scott already answered there's simply not enough energy in the nuclear materials in the fallout to make a dent in the temperature or entire ice masses.

It would be hard to provide numbers even if the number of warheads and amount of nuclear materials weren't classified, since it's very hard to predict how much of which radioactive isotope would end up where.

But to make a rough guess, let's start with the percentage of ice on the planet surface, thanks to NASA:

Global sea-ice coverage averages approximately 25 million km2, the area of the North American continent, whereas ice sheets and glaciers cover approximately 15 million km2, roughly 10% of the Earth's land surface area.

And the total volume of ice on the location that would cause the highest sea level rise:

The Antarctic Ice Sheet contains 30 million cubic kilometers (7.2 million cubic miles) of ice.

That's a lot of ice, especially if only 10% of the fallout lands on it (we're being generous here, or some missile command decided to target Antarctica instead of cities). Unfortunately, there are quite a few nuclear weapons in the world, about 15,000 between the US and Russia.

So the fallout of each nuclear weapon would need to melt 20,000 cubic kilometers of ice to melt all of Antarctica. Converting to mass, it's slightly less than $ 20,000 km^{3} * 1,000,000,000 (km^{3} -> m^{3}) * 1,000 kg/m^{3} = 20 * 10^{15} kg $.

That's 20 Quadrillion kilograms of ice.

At this point I could guesstimate the energy needed to melt that mass of ice and probably express it in megatons of TNT. My feeling is that even if most of the warheads were detonated right on Antarctica and magically converted into heat aimed at the ice, that still would barely scratch the surface.

But the question is not about the nuclear explosions, but about the heat from radioactive decay released by the fallout. The pre-detonation contents of the nuclear weapons is likely just as radioactive as the fallout. And those warheads seem to be just fine inside their silos and nuclear subs.

So if the nuclear warheads are not melting their casings, do you think they can melt 20 Quadrillion kilos of ice (that's twenty Million Billion kilos) each?

Answer 3

There is a concept of a "Nuclear Summer" (also here). Wiki says that it is far less scientifically supported than nuclear winter, however.

Some content from one of the sources (pdf link) reads as follows:

Nuclear winter might give way to a nuclear summer. The high temperatures of the nuclear fireballs could destroy the ozone gas of the middle stratosphere. The result would be an increase in ultraviolet radiation on the surface of the earth, affecting both plant and animal life.

Answer 4

Actually if there was an all out nuclear war the amount of radiation released would raise global ocean temperatures that will eventually lead to the melting of all ice on earth