As an artificer, you use tools when you cast your spells. When
describing your spellcasting, think about how you’re using a tool to
perform the spell effect. [...] If you cast cure wounds using
tinker’s tools, you might have a miniature mechanical spider that
binds wounds
[...]
The same principle applies when you prepare your spells. As an
artificer, you don’t study a spellbook or pray to prepare your spells
[...]
Such details don’t limit you in any way or provide you with any
benefit.
So for the skill Arcane turret :
At 3rd level you learn how to create a magical turret. With your
smith's tools in hand you can take an action to magically summon a
Medium turret [...]
As an artificier you are not a wizard who can cast spells but you craft something that can cast spell. In this way you can probably use Dispel Magic or interrupt the process, like you could with spiritual weapon.
Whenever you wonder whether a spell’s effects can be dispelled or
suspended, you need to answer one question: is the spell’s duration
instantaneous? If the answer is yes, there is nothing to dispel or
suspend. Here’s why: the effects of an instantaneous spell are brought
into being by magic, but the effects aren’t sustained by magic
The turret :
With your smith's tools in hand you can take an action to magically
summon a Medium turret
It also use a spellslot after the one free, keep being a "magic turret" that you activate as a bonus action at distance and disappear when the spell end. So I really tend toward think dispel should work (but do not abuse about it, it would be no fun for the artificier)
Anyway keep in mind that :
Dispel magic has no effect on something that isn't a spell. But if a
DM rules otherwise, this works.
cf https://twitter.com/JeremyECrawford/status/811638194097655808