I remember reading Eric Newby's book The Last Grain Race in which he reports some of the conversation of the Scandinavian crew. It struck me strongly at the time that phonetically it sounded very similar to Geordie.
There's lots of Norse in Geordie, which you don't find in more Southern English generally but may find in place names: Wor - Our (Norse Vor), Bairn - Child, Laik - Play, Laithe - Barn; Beck, Foss, Scar and Fell are found throughout the North, especially the North East. Simple fact is that Old Norse and Old English were similar enough that with familiarity and care Norseman and Englishman could understand each other, and as the Norse settled amongst the English intermediate forms of the language would have sprung up. Indeed, one of the main differences was the noun case endings, which like in Latin and modern Icelandic and Russian could do the work done in Modern English by prepositions. As the case endings differed, more use was made of prepositions so the mixing of Old English and Old Norse may have contributed to the breakdown of the case system of Old English and a move to greater use of prepositions and word order to take their place as in Middle and Modern English. It doesn't surprise me that some of the cadence and phonology of Old Norse survives in both modern Scandinavian languages and North Eastern English dialects.
Talk of Geordies stationed in Iceland being able to understand Icelandic are however bunk; modern Icelandic and even the deepest Geordie dialect are nothing like similar enough for that; Geordie is more like Icelandic than standard English is, but it's still way closer to standard English than it is to Icelandic!
But I digress.