TL;DR Boy rides an iceberg south and discovers boobies. And the sun. But his heart is with the boobies.
"Flow" by Arlan Andrews, Sr. is basically a travelogue and feels like it is probably part of a larger bildunsgroman. (There has been at least one previous story published in Analog.)
Rist lives in the cold north where it is perpetually cloudy and they harvest icebergs and send them down a river to the Warm Lands. Rist is accompanied by Crusher, who is entirely too helpful unless he has been paid by Rist's dad to keep him out of trouble. (And if he has been paid, he should return the money.) Cruthar acts as a tour guide to show Rist the wonders of the Warm Lands.
This is a post-apocalyptic world. People are smaller than they used to be (particularly Rist's people) and most technology has been lost so people generally live in fairly primitive conditions.
The first wonder that Rist encounters is the Sun and his Mind is Blown! Shortly after they arrive at God's Port which is much larger than anything Rist has ever seen. The Warm Landers have also managed to salvage some old tech including some monomolecular wire.
Rist and Cruthar disembark the iceberg and head into town where Rist encounters his next wonder: Women have boobies! His mind is blown! (and he's also really attracted to them despite never having seen them before.) Then Cruthar takes Rist to church and His Mind is Blown! Well, until the priest asks him to tithe and to bring him a chicken for a sacrifice.
Anyway, you remember when I said Cruthar ought to return the money he got for looking after Rist? That's because he helps Rist steal some of that monomolecular wire, despite knowing that they will be searched when they leave God's Port and if they are caught they will be burned at the stake. This made absolutely no sense. Why does Cruthar help him? He won't get a benefit from the theft. It's just sort of "Ok, you want some wire, let's go steal some." It would have been a lot better if Rist had stolen it on his own.
Predictably, the priests are on to Rist and he escapes in a boat that was arranged for him by Cruthar. He rides it down the river until he hits some waterfalls and realizes there is another city at the base. He decides to rappel down using the monomolecular wire.
This is a competently written piece and the world building is generally good. Where the story falls down is that the worldbuilding isn't interesting enough to carry the story. Rist isn't very interesting and not much happens until Risk steals the wire.
One of the techniques Andrews uses to show change from the apocalypse is language drift. Unfortunately one of the changes is women are called "wen" for wench. Though it's a bit apt in that all the women in the story are prostitutes. (well there's a mention of Rist's mother.) Otherwise, it's entirely a man's world.