The official announcement from Norges Bank is here. It states in part:

Today, the Ministry of Finance has approved the request of Deputy Governor Jon Nicolaisen to relinquish his post effective immediately because he has not received a renewed security clearance from the Norwegian Civil Security Clearance Authority.

“The Norwegian Civil Security Clearance Authority informs me that the reason that I will not receive a renewed security clearance is that my wife is a Chinese citizen and resides in China, where I support her financially. At the same time, they have determined that there are no circumstances regarding me personally that give rise to doubt about my suitability for obtaining a security clearance, but that this does not carry sufficient weight. I have now had to take the consequences of this”, says Jon Nicolaisen.

For news reports on this story, see:

Richard Milne, “Norway’s central bank deputy governor Jon Nicolaisen resigns over China ties,” Financial Times, December 4, 2020

Terje Solsvik, Nora Buli, “Norway central bank deputy chief quits after security snub over Chinese wife,” Reuters, December 4, 2020

Associated Press, “Norway’s deputy central bank chief resigns over China ties,” December 4, 2020

The Associated Press noted: “It was unclear if Nicolaisen’s wife has any ties to the Chinese government or other interests.”