Final answer:
The seafarers who disrupted Charlemagne's empire were the Vikings, skilled navigators from Scandinavia who raided northern Europe for wealth and slaves.
Step-by-step explanation:
The seafarers who shattered the stability of Charlemagne's empire were known as the Vikings. These Norse seafarers expanded from Scandinavia (Norway, Sweden, and Denmark) and used their exceptional maritime skills to navigate Europe's waterways. They not only engaged in trade but also conducted numerous raids across northern Europe, targeting monasteries and settlements in search of wealth, particularly silver, and slaves. In response to the Viking threat, Charlemagne himself took measures to protect his empire by constructing fortifications and expanding naval defenses.