A Yukon glacier is slowly advancing towards an Alaskan river, setting the stage for an awesome collision of natural forces.

If the glacier that originates near Mount Logan in the Yukon continues advancing at its current rate, it could block access to a fiord in Alaska and "strongly impact" the nearby ecosystem. 

New research from the University of Kansas suggests the Hubbard Glacier could permanently dam the entrance to Russell Fiord, on the Gulf of Alaska, within 25 years. 

The timeline is the "best guess" of assistant professor Leigh Stearns, whose research builds on decades of previous studies on the Hubbard Glacier. The glacier, which originates in the St. Elias Mountains of southwest Yukon, has been widely studied because of its enormous size and its proximity to the Alaskan community of Yakatat.  

Hubbard Glacier map

Researchers from the University of Kansas say the Hubbard Glacier could pinch off the opening to the Russell Fjord as early as 2040. The fiord could then overflow into the Situk River. (Google)

Water in Situk River could increase 50-fold

Experts say the main impact of the Russell Fjord closure will be on the Situk River, which originates from a lake of the same name.

David Williams, project manager of the Yakatat watershed study for the U.S. Army Corps of Engineers, estimates it would take about a year for water levels in the dammed fiord to rise 40 metres, at which point glacial meltwater would overflow into the Situk River. 

"It will be catastrophic for those who presently fish the Situk under its present conditions because it will change the conditions drastically."

The river is heavily used by commercial fishers in Yakatat, which has a population of about 650 people. 

Hubbard Glacier, Russell Fjord

The Hubbard Glacier is the world's largest non-polar tidewater glacier, which means it's big. In the distance is Russell Fjord. (Gordon Hamilton/University of Maine)

"When you have a river that's running relatively low flow and you increase [it] by anywhere between 20 and 50 times, it's not going to leave the bed of the river or the banks the same," says Williams.

He says the lower part of the river river would likely get colder, have more channels and will be full of logs jams because of upstream erosion. Not only will this change dynamics for fish and wildlife in the area, it could make it difficult and dangerous for fishers to access the river. 

Williams predicts the overflow would be mostly freshwater, because the denser salt water will remain on the bottom of the fiord.

Glacier increases in size 

Leigh Stearns

Leigh Stearns measures water velocity in the narrow gap between Disenchantment Bay and Russell Fjord. (Gordon Hamilton/University of Maine)

Stearns says the Hubbard Glacier is unusual because it has been steadily advancing for more than 100 years despite warmer temperatures. The glacier is accumulating mass near its origin faster than it's losing it in the ocean. 

"It would need to warm a lot for Hubbard to start retreating, is what we're finding. Whereas, a lot of the neighbouring glaciers — it only has to warm a little bit for them to become unstable." 

Russell Fjord has been temporarily blocked by the Hubbard Glacier twice in recent history but the closures did not last long enough to overflow the fjord. The longest closure, in 1986, lasted about five months and caused fiord levels to rise 25 metres, according to Williams.

A sight to see 

There could be short term benefits to the closure. Reggie Kirkovich, who owns a fishing charter company in Yakatat, says the last time it happened, every room in town was booked by news outlets, environmental groups and tourists wanting to visit the glacier and see the marine life trying to escape the freshwater fiord. 

"The folks that were here said it was an absolute bonzana."  

Williams says the Situk River would eventually stabilize enough so fishers could access it again and says it could even increase the fish yield in the long run by creating more spawning habitat. 

He says they won't know for sure until it happens.