The narrator gives us insight into the character by butting into the action and telling us what the main character's "trouble" is before we even have time to form an opinion ourselves. Modern creative writing teachers would probably poo-poo something like this today, but in London's time, it wasn't all that out of the ordinary to tell rather than show every once in a while.
The man wears the stuff he needs in order to survive in the cold. He has mittens, a jacket, and boots with moccasins on underneath them. He wishes he had a nose strap to protect his nose and cheeks; but for the most part, he seems to know what he's doing in the department of arctic fashion, so that tells us he's not a complete rube.
We learn a lot about the man through his actions. He shows that he's cautious (and a little selfish) when he forces the dog walk ahead of him on the ice on Henderson Creek. Of course he also tries to kill this dog in order to save himself later in the story. But he also tries to help clear ice from the dog's toes, and takes off his mittens to do so.
At this early point in the story, he is surprised by how quickly his fingers go numb, suggesting that he is not fully prepared for the cold. He stays calm and builds a second fire when he goes through the ice himself, and even though he's annoyed, he knows it's the right thing to do. Only when his hands totally freeze does he really start to panic.
Toward the end, he starts running for the camp, even though it's clear he'll never make it. After he calms down, he resigns himself to die with dignity. This all suggests that the man is a pretty rock-solid fella. He's just bitten off more than he can chew by hiking alone in such cold weather.
The names in this story are significant because, well, there are none (except for one mention of the name "Bud"). We have the unnamed man, the wolf dog, the "boys" at the camp, and the old-timer at Sulphur Creek. The lack of names makes the characters somewhat archetypal and impersonal, even while London describes his main character in very vivid terms. This shows that identity can be lost in the white abyss of the north. After all, names are part of human civilization, which has little place in the arctic tundra.
The man is nine hours away from the camp he's heading toward, which means he must be quite confident in his hiking ability. He's alone because he has voluntarily separated from the rest of his group, which also shows a confidence that borders on recklessness.
It is unclear what the man's occupation is, but it is not unreasonable to think that he has some stake in the mining claim he's heading toward. He's new to the profession, but confident in his abilities.
The man has a red beard that suggests his fiery toughness and hearty temper. The frozen chewing tobacco on his chin also indicates that he isn't totally out of place in this harsh wilderness. But the fact that he keeps forgetting that his face is frozen suggests that he doesn't pay enough attention to his body or surroundings.
The man carries a bundle of biscuits pressed to his bare chest and some birch bark in his pockets, which indicates that even though he is new to the wilderness, he's pretty well-prepared and resourceful.
The man's lack of concern about the cold is apparent at the beginning of the story. Only slowly does he seem to realize how dangerous the day is, as his fingers slowly go numb and his fire is put out by falling snow. The waning of his confidence is very gradual, and it's only after things have gone too far that he even entertains the possibility that he might die. He thinks of losing fingers and toes without any real concern, suggesting that he's tough as nails. But there's a thin line between tough and ignorant, and sometimes the man crosses it.