A professor of environmental history at Tech and author of the soon-to-be-released book “Sustaining Lake Superior,” Langston spoke on the impact of climate change on Lake Superior at a Keweenaw Climate Community event this week at the Orpheum Theater in Hancock.

Average annual air temperatures have increased by 1 degree Fahrenheit in recent years. Over the same time, water temperature has risen twice as much.

Temperatures are changing in different ways at different times of the year. Early fall temperatures are increasing at greater rates than average, she said.

“You can swim a little bit longer in the fall, but that also really changes what happens with ice cover,” Langston said.

Despite occasional spikes, such as the “polar vortex” winter of 2013-14, ice cover has declined by 79 percent over the past few decades. Some projections forecast Lake Superior losing all ice cover by the end of the century. That could have implications on Lake Superior fisheries and on cultural practices such as ice fishing.

Snow patterns are also shifting. The Keweenaw isn’t seeing less snow — and won’t for a long time, Langston said. But the first snow and the snows that stick around are coming later.

“We’re seeing a lot of frozen soils before we have snow cover, which actually can have some profound effects for soil microbial ecology, for all the life in the soil we can’t see,” she said. “That really matters for forests and other parts of the ecosystem.”

Storms are also becoming more intense, taxing infrastructures designed according to milder historical norms. A 2012 storm in Duluth dumped 10 inches of rain on the city in 24 hours, twice the record. 

The warming climate has also become more hospitable to a host of invasive species, as well as pests such as ticks. That has led to greater moose mortality in winter, as the ticks cause hair loss, causing more moose to freeze to death.

Over the next few decades, the number and intensity and storms are projected to increase more. That could increase raw sewage overflow by up to 70 percent, according to Environmental Protection Agency models.

Other projections show temperature increases under high-emissions scenario. Average temperatures under high-emissions forecasts could rise from 5 to 6 degrees.

The warming could also change the mix of trees in forests at an accelerated rate. With no climate change, the Minnesota North Shore climate is expected to have a spruce-fir mix. With warming, that would change to aspen, oak and northern hardwoods.

“It’s not like all the trees are going to die,” Langston said. “We will still have forests in our lifetimes, in your lifetimes. But the composition of those forests may change pretty dramatically. And that means forest managers now have to make some pretty challenging decisions.”

As a cold lake, Superior has acted as a sink for numerous chemicals of concern that have come from out-of-basin sources. The overall impact is unknown. Changing currents could lead to a difference in how much gets transferred to Lake Superior; whether that change is positive or negative remains to be seen.

The lake, the world’s largest by surface area, holds 12 percent of the world’s fresh water. The Great Lakes Compact prohibits lake water being transferred to drought-plagued states such as Arizona.

However, Langston said, drought problems elsewhere could end up bringing thousands of new residents to Michigan.

You can read much more about Professor Langston's research at her website here.

http://www.sustaininglakesuperior.com