An upsurge is when there's a sudden rise of something's strength or size. Hordes of people walking around your town with cameras might be due to an upsurge in tourism, for example.
News shows often announce that there's an upsurge of crime or an upsurge of available jobs in public education. The noun upsurge is most often used in this figurative way, rather than to talk about something literally surging up, like stormy waves. These are more likely to be described as a surge, which is actually the root of upsurge — a surge is a "high, rolling swell of water," from the Latin surgere, "to rise."