In her caption she wrote that Fredinburg was "one of my favorite human beings on Earth. He was one of the great loves of my life. He was one of my truest friends."
The "Chicago P.D." star went on to encourage her 1.5 million followers to appreciate and hug their friends and family. "Please tell those you love that you do," she wrote. "Right now. This very minute. And please send a kiss to the sky for my friend Dan."
Fredinburg was climbing Mount Everest when the 7.8 magnitude earthquake triggered an avalanche, which killed at least 17 climbers. The Google executive's sister confirmed his death in an Instagram post on Saturday.
Fredinburg and Bush split in February 2014, but their breakup wasn't publicly announced until August.