Climate Change on Lake of the Woods: It's Getting Hot Out Here!
This week's annual Rainy-Lake of the Woods Watershed Forum provided many lessons in watershed and local climate science. Many challenges lie ahead for Kenora and the Lake of the Woods region, and as lake people, we have very strong incentives to ensure carbon emissions are curbed as rapidly as possible.
What does climate change look like in my backyard?
Climate change is always on my mind, and mostly I focus on high-level actions to improve national and global conditions. Climate policy discussions are all about striving to limit global warming to no more than 1.5C by 2100 in hopes of giving us a better than random chance of preventing the very worst impacts of climate change from ravaging the planet. My colleagues and I talk about carbon budgets, climate tests, policy instruments that we need to develop and implement to ensure we ratchet down our emissions rapidly and keep ourselves and our fellow creatures on Earth safe.
But rarely do we talk about the daily face of climate change at home.
Climate change is still an abstraction for most of us. But this week, the ice road went out at a record early date, and thinking back to the start of winter, many of us were wondering if people would still be boating to camp at Christmas. Still, beyond the shortened winter, many people don’t notice that too much else has changed and it’s easy to shrug climate change off as someone else’s problem. Sea levels rise and glaciers melt and droughts and wildfires ravage distant lands, but Kenora seems to remain more or less untouched.
This week, the annual Rainy - Lake of the Woods Watershed Forum debunked this myth of security and it tackled local climate change head on. Hosted by the Lake of the Woods Water Sustainability Foundation, and held in International Falls, MN, this was the 13th year for this important international science conference. A full one-third of this year’s program was devoted to focusing on climate change impacts on Lake of the Woods and the watershed. It was a sobering, at times frightening, report on the past, present and future state of the basin. Here are some of the main concerns highlighted during the climate change session.
1) Temperatures are Increasing
The March 9 closing of the ice road this year isn’t just a freakish anomaly, though it is positioning us to beat the current early ice-out record of April 7, 2000.
Over the past century, as Dr. Brian Cumming of Queen’s University’s PEARL lab told us, meteorological data reveal that the annual mean temperature at Kenora has increased 1.5°C since 1900. This temperature increase hasn’t happened uniformly across all seasons: the summers are still relatively the same as they were in pre-industrial times, but our winters have become much warmer. The mean winter temperature has increased by 2.3°C over that same time period.
Warmer winters mean fewer days of ice cover on the lake. Since the 1960s, we’ve seen a rate of decrease in ice cover of about 4 days per decade, so that we now have a full month less ice cover on Lake of the Woods than when I was born.
Less time with ice cover has huge implications for the ecology of the lakes, as I’ll explain below.
2) Light Infiltration Drives Lake Warming
The implications of these physical changes to winter conditions are staggering. With no ice cover, sunlight is able to penetrate deeply into the lake. It is light, rather than air temperature, that drives warming in lakes, so if sunlight is hitting the water for an extra month each year, the temperature of the lakes is correspondingly rising.
3) Algae Blooms Proliferate
Warmer water with more light makes for great conditions for plants to grow, especially algae. As a result, algae blooms like the one seen in the IJC photo below, occur earlier in the season now, and last longer.
Environmental consultant Dr. Brian Kotak discussed the rise in toxic blue-green algae in Lake of the Woods, and mentioned a handful of dog deaths and human poisonings that happened in 2015 following exposure to microcystin and anatoxin-a, respectively potent liver and neurotoxins, found in blue-green algae blooms. While it’s still not entirely clear what starts blue-green algae outbreaks, nor what causes some to be toxic while others are relatively safe, the science is pointing to a complex interaction between historical phosphorus pollution from industrial mill and sewage effluent dumping in the 20thC and a range of climate change effects.
4) Fish Are Struggling to Survive
Warmer lakes and algal blooms change the chemistry and biology of the lakes. As we heard from USGS hydrologists Dr. Erik Smith and Dr. Richard Kiesling, with the level of greenhouse gas emissions forecast to the end of this century, we are on track to see between 4.5C and more than 8.5C of warming at Lake of the Woods. The USGS has robust and well-tested lake / climate models that suggest that about half the boreal lakes in northern Minnesota will cease to support cold water fish by about 2050 because the fish will no longer have suitable cold water habitat remaining in most of the region’s lakes.
Dr. Scott Higgins, a senior research scientist at the IISD-Experimental Lakes Area, called this loss of optimal habitat the “Goldilocks problem” for lake trout: the zone of cool, nutrient–rich water between the hot surface and the oxygen-depleted depths becomes too small to support the survival of a population of fish. Dr. Higgins said that in the ELA lakes, lake trout size and condition is already declining, suggesting that the fish are struggling under the 2.3C warming that has happened over the past century. His expectation is that before long, their abundance will also decline until we no longer have lake trout this far south in Northwestern Ontario.
5) Climate Change is Altering Wind Patterns
One of the more surprising concepts presented this week was that as planetary warming is altering atmospheric wind patterns on a continent-wide scale, this is having profound impacts on Lake of the Woods and other boreal freshwater lakes.
Dr. Cumming showed an image similar to this one, and explained that in the past, our region was predominantly under the influence of the Pacific air wedge. But in recent years, these massive air currents have begun to shift as the atmosphere warms, and now the Pacific air wedge, the Tropical airstream, and the Arctic airstream converge directly over the Lake of the Woods, where they create some wild weather and stronger and more frequent winds.
The Pacific air wedge has long been the dominant air current at Lake of the Woods where winds typically blow from west to east, causing a sheer stress over the lake surface that helps to mix the water column. Periodic strong winds are important for distributing nutrients throughout the water column, churning up lake sediments. Especially in the wide open, shallow Big Traverse part of the Lake wind churns up massive amounts of phosphorous that’s fallen out of the water column and into the mud at the bottom. This physical mixing from wind helps keep phosphorus biologically available to algae and is a confirmed major driver of algal blooms.
Wind also determines if a lake stratifies or not. Under calm conditions, a typical boreal lake will settle into different temperature layers called a thermocline: warm at the surface, and cold at the bottom. The light-shading presence of undisturbed dissolved organic carbon (DOC) - the stuff that gives lake water a brown colour like tea - near the surface ensures deep water remains cold.
Under windy conditions, water mixes more thoroughly, disrupting and mixing in the DOC through the whole water column. With no surface DOC screen to filter light, sunlight penetrates more deeply, warming the whole lake while the wind also mechanically mixes water to a more uniform temperature. When it’s windy, no deep water cold zone forms. For this reason, more wind leads to less lake trout habitat.
As little as a few hours of wind at more than 10 miles per second will disrupt the thermocline and in 2015, the summer was exceptionally windy on Lake of the Woods, a condition that is expected to continue as atmospheric wind currents jostle high in the warming skies overhead.
6) History tells some alarming stories, but the future remains uncertain
History can often provide insights about how ecosystems might be expected to function under different physical conditions. At the Forum, there were several talks that looked to the paleolimnological record (the stories told through ancient lake sediments) to see how the local climate has changed through time, and to see if it might be possible to make inferences about how we can expect the current climate change period to alter our landscape.
Historical data taken from lake sediment core samples, like the one seen in this photo from the Minnesota Pollution Control Agency, has allowed researchers to piece together climate profiles for the region over the last 10,000 years. What they’ve found is that while history has seen some warming periods in the past, they don't compare well to the present and so we can’t predict very well what we should expect over the next hundred years. The rate and type of warming we currently see is on a scale that is orders of magnitude faster than anything recorded in our last 10,000 years and we can only make very general estimates of what might be in store.
The Paleohistory of Lake of the Woods
From 10,000 to about 9,350 years ago, glacial Lake Agassiz was shrinking and the north end of Lake of the Woods was much deeper than at present. The Big Traverse likely didn’t exist as a lake basin until the end of this period. It is difficult for researchers to tease out ecological impacts that could be attributed to a changing post-glacial climate versus isostatic rebound, the process by which land springs back after being compressed under the massive weight of glaciers.
The so-called Holocene warm period lasted for thousands of years, from about 8600 years ago to 4500 years ago, and represented a period that was significantly drier and was 2-3C warmer than period that preceded or followed it. In its midst, around 7630 years ago, a massive shift happened in the biological communities that are represented in the sediment cores from Lake of the Woods. Lakes dried up, and what water remained became extremely eutrophic – or algae filled. The boreal forest was more open, with more shrubs, herbs, and deciduous trees represented. Forest fires were far more common. The species represented in the lakes changed, with many diatoms and small invertebrates dying off and being replaced by other dominant species. Some lakes show signs of heavy bacterial action, suggesting that there was a lot of decay happening, rather than healthy productivity.
Following the Holocene warm period, conditions cooled and became wetter. Since about 2500 years ago, the climate has stabilized to our modern, pre-industrial conditions.
However, in the 1920s, biological indicators started showing climate change shifting again. This really took off in the 1970s, with massive changes in lake diatom, invertebrate, and plant species. Over the past century, we have seen an amount of warming equivalent to what took place across the entire 4,000-year expanse of the Holocene warm period.
Given the impacts that 2-3C warming caused thousands of years ago, scientists are predicting that we are in for massive species changes in the lakes, much drier and drought-ridden conditions, and lots of forest fires over the coming century. All the more alarming is that right now, if we manage to curb emissions by 2100, we are still locked into about 4.5C in warming in our area. And if we do nothing to curb carbon emissions, Lake of the Woods will see more than 8.5C warming by the end of the century.
What Can You Do?
Though the future is always full of uncertainty, it is also a space for opportunity. One way to amplify the impact of your actions is to join with others who share your concerns. Join TIK, take action to fight climate change, and come help us protect our watershed!