PORTAGE GLACIER, Alaska — As she marveled at the site of a shrinking Alaska glacier, the newly installed leader of the Environmental Protection Agency said Monday that the president told her that fighting climate change should be her primary focus

“The president’s main priority for me was to recognize when I was coming in here that this is going to be a significant challenge and one in which the administration was going to begin to tackle,” said EPA Administrator Gina McCarthy.

While the Portage Glacier has been in a long retreat, the National Climate Assessment links the accelerated melting of glaciers and Arctic sea ice to global warming caused by human activity. Worldwide, most glaciers are losing mass and some are disappearing altogether.

McCarthy is visiting Alaska in one of her first trips since the Senate confirmed her as EPA chief last month.

“Here it’s a beautiful sight,” she said after taking a boat tour to the face of the glacier near Anchorage. “But in other areas, the melting of ice pack is a significant issue, primarily for drinking water.”

Limiting the greenhouse gas emissions from America’s power plants is the centerpiece of President Barack Obama’s climate change plan, which he laid out this summer. He instructed the EPA to figure out the specifics.

McCarthy said Monday that the agency is working on how to lower carbon emissions and make the nation’s infrastructure better able to deal with global warming

“The climate is changing and we need to adapt to that change and make sure communities are prepared,” she said.

A trip to Iowa two weeks ago highlighted the issues, she said.

“There was no question in discussions with both farmers and ranchers the climate change impacts we’re seeing right now are severe,” she said. “We’re having drought and floods in the same state at the same time.”

McCarthy’s path to the EPA’s top job was rocky. Senate Republicans held up her nomination for more than four months before she was confirmed July 18. They used Obama’s choice of McCarthy to highlight complaints about the agency’s environmental regulations and the president’s agenda. McCarthy was previously head of the EPA’s air pollution office.

Alaska’s senators were divided over her confirmation. Democratic Sen. Mark Begich voted for McCarthy, while Republican Sen. Lisa Murkowski opposed her, although she did not support a filibuster attempt. Murkowski, the top-ranking Republican on the Senate energy committee, did not return a message Monday about the new EPA leader.

“Sen. Murkowski agrees that climate change should be addressed, but remains concerned about the administration circumventing Congress to impose costly and unpopular regulations,” her spokesman, Robert Dillon, said in an email.

Senate Minority Leader Mitch McConnell, R-Ky., has characterized Obama’s climate change plan as a war on jobs, particularly targeting the coal industry,

McCarthy said Monday she wants to hear from officials in Alaska and the other states on out how to combat climate change in a way that gives them flexibility.

“How do we make a response to this climate challenge work in a way that’s healthy to the economy as well as addressing what is perhaps the greatest threat we have to the environment,” she said.

McCarthy next plans to visit the Bristol Bay region of Alaska, where the EPA is considering blocking the gigantic Pebble Mine project. The open pit mine is proposed for an area that produces half the world’s wild red salmon. McCarthy said she wants to hear from mine developers and local residents who would be affected.

“Right now we’re in a fact-finding mode to make sure we get the science correct and we understand the impacts in that area,” she said. “Then we will work on what that means for decisions.”