Isaacman was first nominated for the role year ago, but President Trump withdrew his nomination months later. Then Trump renominated Isaacman last month.
Russ Vought, director of the White House Office of Management and Budget, said the National Science Foundation "will be breaking up" the National Center for Atmospheric Research in Colorado.
Although the Trump administration has taken steps to scuttle or downplay other reports about climate change, this one struck a similar tone to those from past years.
Researchers say the findings, the first documented case of rising temperatures driving genetic change in a mammal, offer a "glimmer of hope" for the Arctic species, which is facing possible extinction this century.
The comet is the third object ever confirmed to have entered our cosmic neighborhood from elsewhere in the galaxy. Space telescopes and orbiters have been documenting the rare visit.