Dramatic clues to North American climate change have been discovered by a team of Queen's University scientists in the bottom of 50 Arctic lakes.
Using innovative techniques that enable them to collect historic evidence from fossilized algae in lake bottom sediment, the researchers have found signs of marked environmental changes in a variety of lakes of different depths and composition, within a 750-km region bordering the northern tree-line. The changes are a signal of things to come in the rest of North America, say the Queen's paleolimnologists.
"We're seeing a significant, regional change in the ecology of these lakes over the past two centuries that is consistent with warmer conditions," says Dr. John Smol, Canada Research Chair in Environmental Change and co-head of the university's Paleoecological Environmental Assessment and Research Laboratory (PEARL). Dr. Smol conducted the study with Dr. Kathleen Rühland and student Alisha Priesnitz of Queen's Biology Department.
"Because the Arctic is a very vulnerable environment and usually the first area of the continent to show signs of environmental change – often to the greatest degree – it's considered a bellwether of what will happen elsewhere," says Dr. Rühland. "These are important signals that all of us should be heeding: the lakes' sedimentary records have tracked marked and directional ecosystem changes."
The Queen's study will be published this month in the international journal Arctic, Antarctic, and Alpine Research.
To reconstruct past environmental trends, the team used fossil markers (tiny algal cells) preserved in lake sediment. Sediment cores were collected by helicopter from the 50 lakes, in an area from Yellowknife, NWT, in the Boreal forest area towards the Bering Sea in the Arctic tundra. For each lake, they compared fossilized algae preserved in the top, most recent sediment layer with those from the bottom, pre-industrial layer dating back about 200 years.
They found that the aquatic habitat of today is much different from that of pre-industrial times. More fossils of the type that live in open water environments were found in the top (most recent) layer of sediment – an indication that these lakes have less ice cover and a longer growing season that would alter important lakewater properties such as light availability and the way lakes stratify, as a result of warming. This marked a major ecological shift in the lakes that coincides with a period of increased human industrial activities and emissions in more southern regions.
Earlier PEARL studies in the High Arctic tundra had indicated major changes in the different layers of fossils associated with climate warming. The new findings bring the effects of climate change closer to populated areas. "The logical extension was to see if tree-line lakes also show these dramatic changes, and this study confirms that the impact is even greater than previously documented," says Dr. Rühland. "We believe that the consequences of greenhouse gas emissions, in the form of climate change, are already having a notable impact on the Arctic environment."
As well as affecting plant and animal life in this region, melting permafrost and less ice cover are already beginning to have repercussions on human concerns such as transportation, housing, and even sovereignty issues.
Last year an entire Nunavik community was relocated by the Quebec government after melting permafrost caused houses to slide from their foundations. Other researchers have found evidence that ocean ice is thinning, which could have future implications for intercontinental transportation routes.
"Until recently, no one was reconstructing Arctic climates in this way, because the technology didn't exist," says Dr. Smol. "Now that we can, in essence, reconstruct the past through this indirect technique, we're filling in gaps in our knowledge and finding answers to many ecological and environmental questions that have great significance for the future."
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