Columbus was almost certainly not aware of the Norse voyages to North America. Nor, for that matter, were any of his contemporaries. Columbus's surviving writings, as well as his personal library, have been extraordinarily well studied. There are zero references to any such voyages in his surviving writings, and none of Columbus's reading material had anything to say on the matter. His geographic opinions were a hodgepodge of late medieval travel tales and more learned discussions of Greco-Roman geography.

So, why didn't Columbus know anything about the Norse voyages? In the fifteenth century, almost nobody outside of Iceland would have known (or frankly cared) about the Norse discovery of a land they called "Vinland." Our major historical evidence for this discovery comes from two Icelandic sagas: Grænlendinga saga ("Saga of the Greenlanders") and Eiríks saga rauða ("Saga of Erik the Red"). Both works describe events of the 10th century, but were only written down in the 13th century. During the Middle Ages, they didn't enjoy any wide circulation outside of Iceland, and weren't available in any other language. Even today, the Grænlendinga saga survives in only one 14th-century manuscript, and Eiríks saga rauða in only two (14th and 15th century). Given the low availability of these sagas, chances were low that any western European, even a well-read Latinate intellectual, would have read much about the Norse exploits in North America.

Apart from these sagas, there is only one medieval text ( to my knowledge) that narrates the Norse trips to North America. You can find it in Adam of Bremen's Gesta Hammaburgensis ecclesiae pontificum ("Deeds of the Bishops of Hamburg"), written ca. 1070s. In a long and interesting discussion of Scandinavia, Adam drops this interesting anecdote:

"[The King of Denmark Svend Estridson] has also reported one island discovered by many in that ocean, which is called Vinland, for the reason that grapevines grow there by themselves, producing the best wine. Unsown crops also abound on that island, as we have ascertained not from fabulous reports but from the trustworthy relation of the Danes. Every place beyond it is full of impenetrable ice and intense darkness . . The very well-informed prince of the Norwegians, Harold, lately attempted this sea. After he had explored the expanse of the Northern Ocean in his ships, there lay before their eyes at length the darksome bounds of a failing world, and by retracing his steps he barely escaped in safety the vast pit of the abyss" (Gesta 4.38).

To my knowledge, this is the earliest European reference to the North America (and the only one in medieval Latin)! That said, it clearly sits at quite a remove from the events it describes. Any reader of the Gesta will find themselves at the far end of a long game of telephone, with Adam of Bremen, his informants, King Sven Estridson, and his informants standing between us and the Norse voyagers who actually made landfall to North America.

In his research about trade routes to East Asia, Columbus had no reason to seek out a high medieval Latin church chronicle from northern Germany. And even if he had, it's very unlikely that this brief report of Vinland -- in Adam's recounting, just another far-flung Atlantic island -- would have been cause for surprise.

For Adam of Bremen's Gesta, see Bernhard Schmeidler (ed.), Scriptores rerum Germanicarum in usum scholarum separatim editi 2: Adam von Bremen, Hamburgische Kirchengeschichte (Magistri Adam Bremensis Gesta Hammaburgensis ecclesiae pontificum) (Hanover, 1917). For a translation in English, see Francis J. Tschan (tr.), 2002.