water Archives - Woodwell Climate

June 29, 2022— When Susan Tessier and her husband, Tim, went out for the day, they had a lake on their Native allotment. When they came back, It was gone.

“My husband Tim and I left home in the morning and when we came back around 8:00 in the evening the whole lake had drained,” she writes in a post on the Local Environmental Observation Network site— a citizen science website where observers can report unusual changes in their local environment. “There was a hole that had blown out and it had drained into the ocean… It looked like it was blown up with dynamite.”

Water is the ecosystem engineer in the Arctic. The lowland tundra landscape is a network of lakes and streams, mosaicked across an expanse of frozen ground riddled with wedges of ice. The freezing, thawing, moving, eroding dynamics of these features shape the larger landscape, and determine the habitats of fish, birds, plants, mammals—and, of course people—living in the Arctic.

Abrupt lake drainage, like Tessier described, is just one way that changes in water and ice can influence the landscape, but a recent review paper conducted by University of Florida Postdoctoral Associate, Dr. Elizabeth Webb, and Woodwell Climate Associate Scientist, Dr. Anna Liljedahl, indicates events like this may become more common as the climate warms— overtaking lake expansion and slowly drying out the Arctic tundra.

Evidence of lake drainage across the literature

This new paper comes on the heels of a 2022 study that Drs. Webb and Liljedahl also authored, which came to the same conclusion: despite the processes of lake expansion and drainage continuing simultaneously across the Arctic, net lake area is trending downward. The Arctic is getting dryer.

The review complements the strengths of the previous study, compensating for some of the limitations of using geographically coarse remote sensing data. Synthesizing data from 139 sites across the Arctic, pulled from 57 different studies, Drs. Webb and Liljedahl were able to corroborate their own past findings.

“Lake size can vary from one season to the next in response to factors like precipitation or evaporation, so if you’re only looking at a limited set of remote sensing images, that can influence a trend analysis,” explains Dr. Webb. “It’s actually really exciting from a scientific rigor perspective to have two completely different remote sensing methods showing the same result.”

The review also adds weight to the idea that permafrost thaw is the primary driver in the loss of Arctic lakes. A large portion of Arctic soil is ice-rich, perennially frozen ground called permafrost, and as the climate heats up, it has begun to thaw and destabilize. That thawing can both create new ponds, and help drain them. The review indicates that decreases in size and number of Arctic lakes are more prevalent than expected, dominating the dynamic in some areas.

This contradicts another leading theory that changes in precipitation and evaporation rates— called the “water balance hypothesis” — are driving changes in lake area. Prior to Drs. Webb and Liljedahl’s investigations, the prevailing thought was that lake creation would outpace drainage rates, for at least the next several decades.

Climate Change is Opening Drainage Channels in the Permafrost

It works like this: most Arctic lakes form when wedges of ice in permafrost melt, leaving behind a depression that fills with water. The water absorbs and holds more heat, slowly thawing and eroding surrounding permafrost, growing from puddle to pond to lake over the years.

Drainage can happen in one of two ways. The first is vertically, which occurs when the permafrost beneath the lake thaws down to the unfrozen ground beneath, allowing the water to seep out the bottom. This can take hundreds or thousands of years, depending on how deep the permafrost is.

The second way is horizontally, through what Dr. Liljedahl calls “capillaries”. Ice wedges are common across the Arctic, connected by an underground network of ice that pushes the soil above them upwards as they grow, creating ridges that impede water flow. But when the tops of these wedges melt, the ridged ground above them subsides, forming narrow channels between lakes and ponds. When an expanding lake meets one of these capillary channels, the lake can drain in a matter of hours, as if the plug has been pulled on a bathtub drain.

“The formation of lateral drainage channels can interrupt this lake expansion process at any time, and I think that’s what’s making it override expansion and cause the net drying effect,” Dr. Liljedahl says. “The lake that took millenia to grow can be gone in a couple of hours.

Fewer Arctic Lakes Leave Communities in the Lurch

So what does an Arctic with fewer lakes mean? In terms of carbon, the picture isn’t clear. Since lake expansion— a common source of methane emissions— and lake drainage are happening concurrently, the net effect is not easy to discern.

“With lake drainage, it’s much less clear what the carbon consequences are. The current thinking is that lake expansion releases orders of magnitude more carbon than lake drainage, but because it’s complicated, we’re not quite sure,” says Dr. Webb. “It’s definitely an open research question.”

Dr. Liljedahl notes that there is also documentation of permafrost recovering and re-growing in drained lake beds. “Over decades, they could develop new ice-wedges and vegetation on the surface. Lake beds could experience net carbon accumulation for at least a couple of decades after drainage,” Dr. Liljedahl says.

However, the ecological consequences of fewer Arctic lakes are more certain. Fish and other aquatic species will have the size of their habitat reduced and their freedom of migration restricted, as lakes drain and connecting streams dry up. Species that feed on fish or rely on wetland vegetation, like muskrats, will also be impacted.

Small lakes are an important source of freshwater for Arctic communities. Tessier wrote in her post about the lake drainage she witnessed, “We are sad to lose the lake because in winter, after it froze up, we used to go cut ice chunks for drinking water. It has really clear water. If we get enough snow we can use snow water instead, but it is not as good.”

As more lakes drain, clean freshwater could become harder to access. Combined with the destabilization of the ground itself as permafrost thaws, Arctic communities are facing massive changes.

Dr. Liljedahl hopes that refining our understanding of water dynamics in the Arctic will aid adaptation measures. She has been awarded a three year NSF grant to continue studying the ice wedge capillary network and its role in the Arctic hydrological system. She’ll use remote sensing to quantify the distribution of the ice-wedges contributing to increased drainage. She also plans to pull data from field measurements to figure out how permanent the capillaries are, since vegetation feedback loops could help permafrost recover and return the surface to its original elevation.

“We have more to do before we can feel like the models are representing a realistic scenario. We need to better understand what is happening at the sub-meter scale with water, because the presence or absence of surface water will have a major impact on how the landscape evolves,” Dr. Liljedahl says.

Salt marshes across Buzzards Bay, in Southern Massachusetts, are experiencing significant stress from climate-change driven sea level rise, but also a range of other factors including tidal restrictions and nitrogen pollution. A recent report, “Buzzards Bay Salt Marshes: Vulnerability and Adaptation Potential,” released today by the Buzzards Bay Coalition, Buzzards Bay National Estuary Program, Woodwell Climate Research Center, and the U.S. Geological Survey assessed the loss and degradation of twelve salt marsh sites in Westport, Dartmouth, Fairhaven, Mattapoisett, Marion, Wareham, Bourne and Falmouth. Using regular field monitoring alongside remote sensing data, the report reveals the widespread loss of salt marshes – in some places measuring up to 20-percent over an 18-year period.

Buzzards Bay Coalition and Buzzards Bay National Estuary Program began field monitoring salt marsh vegetation and elevation four years ago.

“We knew that salt marshes face a number of stressors, and we’d heard from our members that marshes in their neighborhoods were changing, but there was no consistent monitoring to track the health or stability of these critical ecosystems around Buzzards Bay,” explains lead author Dr. Rachel Jakuba, Buzzards Bay Coalition’s vice president for bay science.

Salt marshes are important ecosystems that filter nutrients, store carbon, provide critical habitat for fish and birds, and protect coastal properties from storm surge. Salt marshes – existing at the interface of the land and sea – are adapted to a fluctuating environment with plants capable of tolerating regular inundation with salt water; however, salt marshes’ natural ability to adapt has limits, which this report documents.

“Looking at remote imagery of salt marshes all around Buzzards Bay, we documented how the marshes changed over a couple of decades. Marshes with low elevation appear most vulnerable to sea level rise and showed the greatest loss,” said co-author Dr. Joe Costa, executive director of the Buzzards Bay National Estuary Program.

Co-author Neil Ganju of the U.S. Geological Survey added, “We’ve applied one of the tools used in this report up and down the East Coast. Marshes in the region are facing the same issues as in Buzzards Bay, and researchers are working hard to better understand marsh loss and ways to mitigate it.”

The news is not all bad though, as these iconic features of the Buzzards Bay coast are resilient and have the potential to migrate landward.

“While the headline of salt marsh loss is sobering, these are remarkable ecosystems that, when given the room to adapt, can continue to flourish. This makes the protection of adjacent lands all the more important,” said co-author Linda Deegan of the Woodwell Climate Research Center.

Scientists conducted the analysis to better understand and document salt marsh change, and the Buzzards Bay Coalition produced this report with the hope that it will be used by municipalities faced with zoning and permitting decisions near salt marshes; by natural resource agencies capable of undertaking direct marsh restoration strategies such as runneling, thin-layer deposition, ditch management and others; and by private landowners, who might consider preserving the uplands that they own adjacent to salt marshes to allow marshes to migrate — unimpeded by seawalls, roads and buildings — in the future.

“While much of this loss is attributable to climate change-driven sea level rise, some is due to legacy effects from human-made alterations like the creation of drainage ditches and marshes being altered for development and agriculture. We’re hoping that this research will be useful to planners, policymakers, and resource managers trying to mitigate the future impacts of both of those drivers,” said co-author Dr. Alice Besterman, assistant professor at Towson University.

Buzzards Bay Coalition and Buzzards Bay National Estuary Program began field monitoring salt marsh vegetation and elevation four years ago.

The news is not all bad though, as these iconic features of the Buzzards Bay coast are resilient and have the potential to migrate landward.

Drought in the Western U.S. has plunged the largest reservoir in the country into alarming shortage conditions that have rippling impacts for the region. Lake Mead, formed by the construction of the Hoover Dam on the Colorado River, delivers water and hydroelectric power to 25 million residents in the Southwest. But its viability has been pushed to the brink by intensifying drought, exacerbated by climate change, triggering emergency measures to conserve water in the basin.

The region has been in a “megadrought” since 2000, but recently, Lake Mead’s water levels have been breaking ever lower lows, unearthing old shipwrecks and other long-forgotten debris and leaving a “bathtub ring” around the reservoir’s edges. The drought signals a larger trend of dwindling snowfall and longer summers brought on by the growing climate crisis.

New water scarcity measures enacted

Water usage on the Colorado River operates on a tier system. When water levels in a reservoir drop below a certain point, usage by neighboring states is restricted. Lake Mead hit Tier 1 in August 2021 after the elevation of the reservoir dipped below 1,075 feet, leading to a reduction in water supplies that largely impacted agricultural users across counties.

This was the first time a shortage condition has been implemented on Lake Mead. The Tier 2 decision was announced in August of 2022—stating that the water level would fall below 1,050 by the end of the year, triggering a more intense shortage.

This emergency declaration for Lake Mead is part of a plan to increase the water levels in Lake Powell— an upstream reservoir and the second largest in the United States behind Mead. Dealing with shortages in the Colorado River Basin has required officials to weigh the needs of one region over another. The Bureau of Reclamation has indicated that at present, keeping water levels up in Lake Powell supersedes the requirements of Lake Mead. The generators at Powell have a total capacity of 1,320 megawatts and the reservoir is considered a ‘bank account’ for the region to draw on in times of drought—which are anticipated to worsen with climate change.

According to the US Drought Monitor, extreme droughts were rare in the historical climate—a 5.5% likelihood. In 2022 however, nearly all of the watersheds in the Colorado River experienced extreme drought. In a world warmed by 2 degrees C, the likelihood of 12 or more months of extreme drought in the Colorado River Basin becomes as high as 40%.

Meeting water needs in dry times

But Lake Mead also serves a massive population in the lower basin, and filling demand for water even during shortages means some major cities have to turn to reservoirs on other river systems. Arizona, suffering some of the steepest cuts in their allotment of Colorado River water (21%) , will draw from the Salt and Verde rivers. Other strategies include pumping groundwater and implementing more aggressive conservation and re-use strategies, which have so-far helped to spare Las Vegas from the worst effects of the shortage.

The Southern Nevada Water Authority also began using its low lake level intake in 2022, which allows the state to draw water even when the elevation of the lake falls below “dead pool” status— the point at which downstream water releases are no longer possible. But this is only a temporary solution, as the water in the reservoir keeps falling.

The next significant threshold for Lake Mead would be a drop to Tier 3 (1,025 feet) which some experts say could come as soon as 2024. At 950 feet, the reservoir would be considered an “inactive pool”, meaning the dam’s generators can no longer run. Energy shortages could kick off a vicious cycle, requiring backfilling with fossil fuels that would exacerbate the climate crisis and warming-driven drought conditions.

Reversing the drought in the Colorado River Basin will ultimately depend on snowfall in the Rocky Mountains, which will ultimately depend on getting the climate crisis under control. Experts estimate there would have to be several consecutive heavy snow years in the mountains to make back the current deficits further downriver. 2023 is currently experiencing above average snowpack, but if temperatures keep rising, that will be a less likely annual occurrence. Water rights and resource usage will have to adapt rapidly to support residents as reservoir levels continue to drop, but pulling out of emergency scarcity measures for good will require curbing the greater impacts of global climate change.

What’s New?

Recent research has quantified the cumulative impact of dams on Brazil’s native savanna ecosystem, the Cerrado. The study created an index of the direct and indirect impacts of constructing hydroelectric facilities on both the rivers being dammed and the surrounding ecosystem.

While often offered as a cleaner alternative to fossil fuels, dams can have severe environmental impacts ranging from deforestation to obstruction of fish migrations, water pollution, and even direct greenhouse gas emissions resulting from inundation of the surrounding area. This study assessed these effects cumulatively, weighting them more heavily if multiple dams were present in a single watershed.

“For freshwater systems, there’s not the equivalent of a deforestation rate. We don’t have an easy metric of ecosystem damage. So this study was one way of building a method for assessing the unintended consequences of installing a dam in a Cerrado watershed,” says Woodwell Water program director Dr. Marcia Macedo, who collaborated on the paper.

The study puts forward a new Dam Saturation Index (DSI) for the region to approximate the environmental impacts of existing dams. High-saturation watersheds were concentrated in the central and western portions of the biome, and most planned dams are located in sensitive areas of native vegetation with little protection.

Understanding hydropower in Brazil

Hydropower is big in Brazil—66% of the country gets some or all of their energy from it. Harnessing the power of a river is often the easiest means of electricity production in rural and remote areas. However, large hydroelectric plants are more often used as a means of infrastructural support for extractive industries like mining, rather than to expand access to electricity for rural citizens. Conflicts have already arisen between communities and hydroelectric plants.

Conflict over water usage in the Cerrado is expected to increase as the region continues to get hotter and dryer due to human-caused climate change. Land use change in the biome has accelerated the impacts of climate change, removing the cooling and moisture-retaining effects of natural vegetation.

“There are a lot of dams already, and many more planned, and it’s only going to get more contentious as climate change continues,” Dr. Macedo says. “In the northern and eastern part of the Cerrado, it’s already quite dry. We’re already seeing conflict over water and these reservoirs could just make that worse as upstream locations are able to withhold water from those downstream.”

What this means for the Cerrado

The Cerrado has historically not garnered as much attention, or as many demands for its protection, as the neighboring Amazon rainforest. Less than 10% of the Cerrado is considered protected, and many of those protections are biased toward terrestrial habitats and species. Lack of research into the full impact of hydropower on the watersheds of the Cerrado has left the region vulnerable to unchecked development. Some dams have even been built in areas otherwise strictly protected. Dr. Macedo hopes this study will encourage a different attitude towards freshwater resources.

“There is a question of how we can innovate thinking about protecting freshwater systems, especially under climate change. They’re so important, and there are so many resources—fisheries and clean water and more—that come from these systems,” Dr. Macedo says.

This study focused on large hydroelectric dams, but Dr. Macedo notes that there are many more small dams, built to serve individual farms, that also impact the flow of headwater streams. Ongoing research is focused on understanding the cumulative impacts of dams of all sizes on tropical watersheds.

As the planet warms, drought is an increasing threat in many regions. Research led by Woodwell Research Assistant Isabelle Runde, modeled the frequency of drought across the globe, analyzing drought changes in forest, food, and energy systems as temperatures surpass 2, 3, and 4 degrees Celsius.
Models show that unlike in a stable climate, unreliable water resources and increasing temperatures make drought more likely in many places. For every increase of 0.5 degrees C, an additional 619 million people could become exposed to extreme drought 1 in every 4 years. This is in addition to the 1.7 billion people (nearly a quarter of today’s global population) who are already exposed to these conditions in a world that has warmed by a little more than 1 degree C.

2 Degrees of Warming Risks Damaging our Best Forest Carbon Sinks

Tropical forests are one of the planet’s key natural climate solutions— able to prevent 1 degree of warming through both carbon sequestration and regional cooling effects. Deforestation, fragmentation and degradation from things like fire, and disease threaten to turn these forests from a vital sink to a source of emissions.

In recent years, the Amazon has been a net carbon source due to increased extreme drought and deforestation, leaving the Congo rainforest as the world’s last remaining stable tropical forest carbon sink.

As warming surpasses 2 degrees, the annual likelihood of drought in the Congo rainforest begins increasing faster than in the Amazon. Drought can make a forest more susceptible to further degradation, such as fire or disease, and reduces carbon sink capacity by stressing or killing trees and placing the ecosystem under stress.

Productivity is Threatened in the Breadbaskets of Mediterranean, Mexico, China

Global crop production is highly concentrated in key breadbasket regions— nearly 72% of the world’s maize, wheat, rice, and soy are produced in just 5 countries. Extreme drought can reduce the productivity levels of these staple crops, among others, potentially triggering widespread food insecurity, hunger and economic disruption.

By 2 degrees of warming, the probability of drought in the breadbasket regions of both China and the United States will be greater than 50% — meaning an extreme drought roughly every other year.

Disruption will be much higher in countries where jobs in agriculture comprise a large segment of the economy. In Mexico, one of the world’s top 10 producers of maize, 12% of the workforce is in agriculture and at 1 degree, the country already has among the greatest areas of cropland exposed to drought. 90% probabilities—indicating near-annual drought—begin to emerge in some parts of the country at 2 degrees of warming.This kind of recurrent extreme drought will stress water resources for agriculture.

The Mediterranean also is a drought hotspot. Drought probability in Mediterranean croplands will increase rapidly between 2 and 3 degrees of warming, rising from just 10% to over 50% of cropland affected by drought in 3 out of 4 years.

Drying Rivers Will Plunge Hydro-dependent Countries into Energy-Shortages

Hydroelectricity supplies a sixth of global energy demand, and is a low-cost, low-emission alternative to fossil fuels. The overwhelming majority of new hydropower plants since 1990 have been constructed in fast-growing, developing nations.

High dependence on hydropower makes countries like Brazil and China vulnerable to energy disruption during periods of drought. Brazil draws nearly two thirds of its energy from hydroelectric resources. During a three year drought between 2012 and 2015 in Brazil, hydroelectric generation declined by 20% each year. If warming exceeds 3 degrees C, more than half of Brazil’s hydroelectric capacity will experience a likelihood of annual drought greater than 50%.

Extreme drought can also be counterproductive to reducing carbon emissions. During years of drought, expensive fossil fuel based energy is often brought in to fill demands. In addition, droughts often coincide with extreme heat events, when electricity demand peaks to run air conditioners. Beyond 3 degrees of warming, more than a third of the planet’s hydroelectric capacity will likely be exposed to extreme drought every other year.

Projections of a Dryer World

Current international climate goals aim to limit warming to between 1.5 and 2 degrees C, but without urgent intervention, we are on track to push past that limit to at least 2.5 degrees C. Projections past 2 degrees of warming show a future where extreme drought is common, exposing already-vulnerable people, places, and economies to greater water shortages, while making it even harder to curb emissions. In order to guard water resources and the systems that depend on them, emissions need to be cut rapidly. And places already feeling the impacts of warming will need to brace to adapt to a hotter, dryer version of the world.

Recent study shows widespread patterns of loss, upending scientists’ previous projections

The Arctic is no stranger to loss. As the region warms nearly four times faster than the rest of the world, glaciers collapse, wildlife suffers and habitats continue to disappear at a record pace.

Now, a new threat has become apparent: Arctic lakes are drying up, according to new research published in the journal Nature Climate Change. The study, led by University of Florida postdoctoral researcher Dr. Elizabeth Webb in collaboration with Woodwell Associate scientist, Dr. Anna Liljedahl, flashes a new warning light on the global climate dashboard.

Research reveals that over the past 20 years, Arctic lakes have shrunk or dried completely across the pan-Arctic, a region spanning the northern parts of Canada, Russia, Greenland, Scandinavia and Alaska. The findings offer clues about why the mass drying is happening and how the loss can be slowed.

The lake decline comes as a surprise. Scientists had predicted that climate change would initially expand lakes across the tundra, due to land surface changes resulting from melting ground ice, with eventual drying in the mid-21st or 22nd century. Instead, it appears that thawing permafrost, the frozen soil that blankets the Arctic, may drain lakes and outweigh this expansion effect, says Dr. Webb. The team theorized that thawing permafrost may decrease lake area by creating drainage channels and increasing soil erosion into the lakes.

These lakes are cornerstones of the Arctic ecosystem. They provide a critical source of fresh water for local Indigenous communities and industries. Threatened and endangered species, including migratory birds and aquatic creatures, also rely on the lake habitats for survival.

“Our findings suggest that permafrost thaw is occurring even faster than we as a community had anticipated,” Dr. Webb said. “It also indicates that the region is likely on a trajectory toward more landscape-scale drainage in the future.”

If accelerated permafrost thaw is to blame, that’s unwelcome news. The Arctic permafrost is a natural warehouse of preserved organic matter and planet-warming gasses.

“Permafrost soils store nearly two times as much carbon as the atmosphere,” Dr. Webb said. “There’s a lot of ongoing research suggesting that as permafrost thaws, this carbon is vulnerable to being released to the atmosphere in the form of methane and carbon dioxide.”

According to Dr. Liljedahl, this study shifts the perspective on prior research—there is still more to learn when it comes to how climate change is altering the Arctic landscape.

“This work shows that we are “living the future” already,” said Dr. Liljedahl. “Or if you look at it from the other perspective, the current models used to project future surface water coverage and permafrost thaw across the Arctic are “off”. They are not capturing key processes. We have already seen reduced lake coverage happening over the previous two decades.”

There is a silver lining in the researcher’s findings. Previous models of lake dynamics predicted lake expansion, which thaws the surrounding permafrost. But because lakes are drying, near-lake permafrost is likely not thawing as fast.

“It’s not immediately clear exactly what the trade-offs are, but we do know that lake expansion causes carbon losses orders of magnitude higher than occurs in surrounding regions,” Dr. Webb said. “So it should mean that we won’t see quite as much carbon emitted as previously thought, because lakes are drying and not wetting.”

The research team used a machine-learning approach to examine the climate change mechanisms responsible for lake area change. By harnessing large ensembles of satellite images to assess patterns of surface water loss, they were able to analyze decades of data across the Arctic. The data is available on the Permafrost Discovery Gateway (PDG), a project that Dr. Liljedahl leads, the goal of which is to make permafrost data broadly accessible to encourage Arctic change research.

“We made the pan-Arctic dataset, including both long-term trend analysis and individual years, accessible on the PDG so that anyone with internet access can interact with the dataset. We are still building the PDG visualization and analysis tools so more options to enable discovery will become available in the coming two years,” said Dr. Liljedahl

The best way to curtail the lakes’ demise and protect permafrost is to
cut fossil fuel emissions and limit global temperature rise.

“The snowball is already rolling,” Webb said, stating that we need to act now to slow these changes. “It’s not going to work to keep on doing what we’re doing.”