Nobody has to convince UNBC masters student Lyssa Maurer our climate is changing rapidly in northern B.C.
She's got the core samples to prove it.
Maurer has proven the hunch of UNBC geography professor Brian Menounos, that after 10,000 years of expansion, Castle Creek Glacier near McBride would provide compelling evidence the glacier abruptly stopped advancing early in the 20th century.
As part of her year-long study, the 26-year-old native of Prince George joined a team of university researchers from UNBC, Calgary, Western Ontario and Simon Fraser University to focus their attention on a lake at the foot of the glacier, which revealed in its sediment when the glacier advanced and when it started to retreat. They have determined the glacier remained close to its Little Ice Age limit for close to 1,600 years before it began to melt.
The small lake, named On-Off Lake by the researchers, is at the base of a hydrological divide, 330 metres from where the glacier advanced to its maximum reaches. That ridge of deposited glacial till, also known as a ground moraine, provided the key in establishing timelines.
When the glacier grew large enough to clear the crest of the hill it dumped fine glacial silt and clay deposits into flowing meltwater which eventually settled at the bottom of the lake. When the ice retreated beyond the barrier, the glacial melt flowed down Castle Creek, rather than into the lake, which received only organic deposits at that time.
The differences in the lake's material deposits over the years were obvious to the researchers in three core samples taken for the study while the lake was frozen. The inorganic glacial material appears light in colour, while the organic plant and animal material is dark.
"The first time the glacier got over the hydrological divide was 2,700 years ago, and we could see that in the lake sediment," said Maurer. "Then it retreated slightly behind this lip and so it accumulated the organic material in the lake. It advanced again 1,600 years ago and stayed past that hydrological divide until the early 20th century.
"What's really interesting about this site is with the divide we can tell in the last 1,600 years the glacier was within 300 metres of its most expansive position [until the early 1900s]."
Without the presence of the lake, typically the only way for scientists to determine the extent of a glacier's reach would be to carbon-date fossilized trees killed and left behind by the advancing ice.
"We have a great way of quantifying how large the glacier was in the past, and that's one thing we've not been able to do," said Menounos. "The main reason for that is that through the last 12,000 years the glaciers have gotten progressively larger, so they tend to override and destroy former evidence like moraines, these big piles of rubble. Often we're just left with the last advance, a couple hundred years ago, and we often have no idea how far down the valley the glacier went as it was getting bigger.
"This glacier was parked for a long time and it really wasn't until the 20th century that it dramatically pulled back."
The study was published in July in the Quaternary Science Reviews journal.
Satellite imagery and aerial photos provided by the province gave Menounos clues the Castle Creek area would be a hotspot for research. As Maurer learned early in the study, much of the preliminary site searching could be accomplished in her living room.
"We use Google Earth quite often, it is a fantastic tool and with the resolution we have now, you able to fly around the world and find places that look interesting," said Maurer. "You can see landforms from what you would assume to be ground level. Now that I know what to look for it makes more sense, but at the beginning it felt like [Menounos] was pulling things out of thin air."
There are obvious longterm concerns about the retreat of the earth's glaciers and ice caps and how that will affect the world's water supply, as well as how much our changing climate is being caused by greenhouse gas emissions. Maurer says science is just beginning to scratch the surface trying to find those answers.
"Studies like this shed a lot of new light on the situation, so it's important for us to continue studies to narrow our scope so we can really see what glaciers were doing in the past," said Maurer. "We know how fast they retreat because we can physically see it, but we can't definitively say how fast they retreated in the [distant] past, so we need that comparison to be able to determine how bad things are today."
Now based in Vancouver while writes her summary of a study of glaciers in Patagonia, Maurer predicts water worries will become a huge global issue.
"I'm a strong advocate for reducing our impact on the world in every way possible but with climate there are so many factors that come into play," said Maurer. "The most important thing for us to to conserve until we know for sure. This is something that affects all people, but there are very few people studying it."
"It's something we all need to be concerned about," she said. "The world won't be fighting about oil for much longer, we'll be fighting about water."
