A more southerly jet stream is behind an ongoing decline in the size of glaciers throughout western North America, a team of scientists led by a University of Northern British Columbia professor has concluded.
The outcome stems from the first comprehensive assessment of glaciers from California to the Yukon. Results from the study were published Tuesday in Geophysical Research Letters.
"Our work provides a detailed picture of the current health of glaciers and ice outside of Alaska than what we've ever had before," said UNBC geography professor Dr. Brian Menounos, the lead author of the paper and a Canada research chair in glacier change.
"We determined that mass loss dramatically increased in the last 10 years in British Columbia's southern and central Coast mountains, due in part to the position of the jet stream being located south of the US-Canada border."
The jet stream is an area of fast flowing upper winds that can steer weather systems over mountains and nourish glaciers with precipitation, mostly in the form of snow that builds up over time and later becomes ice.
The team used archives of high-resolution satellite imagery to create over 15,000 digital elevation models covering glaciers from California to the Yukon.
These models were then used to estimate total glacier mass change from 2000 to 2018, and found glaciers in western North America lost 117 gigatonnes of water or about 120 cubic kilometres - enough water to submerge an area the size of Toronto by 10 metres each year.
Compared to the first decade of the 21st century, the rate of ice loss increased fourfold over the last 10 years, the team also found.
Other UNBC scientists involved in the study were assistant geography professor Dr. Joseph Shea, and two PhD students, Ben Pelto and Christina Tennant.
The team also included scientists at the University of Washington, NASA's Jet Propulsion Laboratory, Ohio State University and the Université de Toulouse in France.
"Frequent visitors to America's glacierized national parks can attest to the ongoing glacier thinning and retreat in recent decades. We can now precisely measure that glacier loss, providing a better understanding of downstream impacts," said co-author Dr. David Shean of the University of Washington.
"It's also fascinating to see how the glaciers responded to different amounts of precipitation from one decade to the next, on top of the long-term loss."
