The pair managed to slip away for their romantic rendezvous without being photographed and enjoyed a front row seat to the Northern Lights.
"He first went there in 2011 and he saw the Northern Lights," Nicholl tells ET. "He made a pledge then that he would always go back, and when he went back, he would take someone special with him."
In addition to the Northern Lights, the couple enjoyed a number of other winter-themed activities on their arctic adventure, including whale watching and an expedition in search of a polar bear sighting!
On Jan. 7, Markle posted a photo of a snowy cabin on her lifestyle Instagram page, The Tig, along with the caption, "#Nature is #magic."
"I'm told the chalet they stayed in wasn't cheap. It was about $400 a night," Nicholl says. "There was an outside Jacuzzi spa, so they could sit and watch the Northern Lights from the comfort of their own Jacuzzi. I'm told they didn't just stay in the lodge, however. Apparently they spent one night in a tepee."
This overseas getaway has some people thinking wedding bells, and Nicholl says that all signs point to a possible engagement in 2017.
"I've spoken to Harry's close friends. They are seriously thinking there could be an engagement sometime later this year," she says. "They're planning to take a skiing holiday, and there is talk that he's going to take her to the wedding of his best friend, Tom Inskip. That wedding will be taking place in March. It's happening in Jamaica. I'm sure Meghan would love the opportunity to go and have some time in the sun. "
Amid Harry and Markle's lovey-dovey trip, the Suits actress' half-sister, Samantha Grant, opened up to ET about new drama brewing in the family. Grant tells ET that reports of Harry meeting their father are not true and that Markle has changed her phone number and ceased contact with the paternal side of her family.
When ET visited Grant in November, she was hopeful of her sister becoming a princess.
"I think it will absolutely be a royal wedding," she said. "And I think she'll love that, because she'll be honored and happy, and that will be her moment."