Novel about a group of scientists crossing the Atlantic on a frozen Earth [duplicate]

Question

I'm trying to identify a novel I have read in the 90s, but possibly date back to the 70s, 60s, or even earlier.

The Earth is entirely covered with ice and snow, and people live in an underground city somewhere in North America. The story starts with a group of scientists and scholars being banished from the city to the surface. I don't remember why, but it was political, they broke a taboo or something (and it may have been for trying to communicate with the outside) Before leaving, they are allowed to take tools and food with them. They decide to trek across the frozen Atlantic ocean, toward Europe. They encounter several difficulties: I remember at some point they fight wolves, and later primitive tribesmen trying to steal their stuff.

In the end, they meet a British patrol. Then some members of the patrol admit they were sent to intercept and kill them before they reach under-London. I think the final twist was something like this: there are several cities of survivors across the globe, each thinking they're the last remnant of civilization, and the leaders want their respective population to keep thinking that because it makes them easier to control.

Answer 1

Sounds like Time of the Great Freeze (1964) by Robert Silverberg.

This review offers a good summary of the plot:

The years is 2650 A. D. Three hundred and fifty years earlier a New Ice Age covered large portions of the globe with ice. Most people trekked south or died as food ran out and towns were overcome. Those that remained in New York and the other great cities of America were able to construct underground cities before the ice covered them over. The societies underground have become increasingly isolated and insular with repressive governments. Food comes from hydroponics facilities and nuclear reactors provide the heat and energy. The cities regulate births inorder to control population due to the limited resources at hand. Sadly, Silverberg devotes only a few pages to the life in underground New York — the most interesting concept in the book. And, there’s news that the ice might be slowly melting!

The narrative follows a group of characters, and our young interchangeable hero Jim, who have made radio contact with London, also an underground city. The group is soon aprehended by New York’s authorities and after a shame trial the aged mayor sentences them to expulsion. Fortunately, they were planning an expedition to the surface anyway to make contact with London. Unfortunately, they have only 12 hours to prepare before they are kicked out of the city. Due to the time constant they still manage to deck out their expedition perfectly with powered sleds, weapons, food, everything! Yes, a gigantic plot hole. At NO point in the narrative do the intrepid explorers realize that they forgot something, or need particular tool, etc. After 300+ years underground I suspect most societies would completely forget how to equipped a trans-Antarctic sort of expedition!

Regardless, our heroes encounter a variety of challenges on their way to make contact with London including primitive inland societies (remnants of peoples who didn’t go underground and didn’t journey south) which wander the ice hunting animals, fierce sea peoples (think vikings), dangerous animals, brittle ice, and the like.