Tahoe Environmental Research Center

Incline Village, NV, United States

Tahoe Environmental Research Center

Incline Village, NV, United States

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News Article | May 23, 2017
Site: news.yahoo.com

In this April 4, 2017 photo provided by UC Davis Tahoe Environmental Research Center, Scott Hackly, a researcher at the University of California, Davis, collects algae samples from a boulder in Lake Tahoe just south of Lake Tahoe Nevada State Park's Sand Harbor in Incline Village, Nev. Algae growth fueled by air pollution and contaminants in storm-water runoff have contributed to the loss of the lake's historic clarity. (Brant Allen, UC Davis Tahoe Environmental Research Center via AP) CRYSTAL BAY, Nev. (AP) — Climate change is causing Lake Tahoe to warm sooner in the spring than it has historically, disrupting the normal mixing of shallow and deep water and undercutting gains made in reversing the loss of clarity of the cobalt mountain lake, scientists say. "Climate change is impacting not only Lake Tahoe's water quality, but also the health of its forests and its recreation-based economy," said Joanne Marchetta, executive director of the Tahoe Regional Planning Agency, which regulates the lake covering 191 square miles (495 sq. kilometers) along the Nevada-California border. Until recently, the climatological cycles affecting Tahoe's clarity had remained fairly constant since 1968, when experts first dropped a white disk into the lake to measure how far down it remained visible. Back then, it was more than 102 feet (31 meters) compared to an average of about 69 feet (21 meters) now. Dry years resulted in clearer water. Storm-water runoff carrying soils and contaminants during wet years made it worse. " You didn't need a Ph.D. to understand it," said Geoff Schladow, director of the University of California Davis Tahoe Environmental Research Center. But the pattern seems to be breaking down, he said. "What we are learning is that climate change isn't just a one-size-fits-all thing," he said in an interview. "It's not just warmer air temperatures or more extreme winters or droughts. It's a combination of all of these things." Average annual clarity for 2016 was about 4 feet (1.2 meters) worse than the 73 feet (22 meters) recorded in 2015, but better than the worst-recorded average of 64 feet (19 meters) in 1997. Marchetta says the improvements are a testament to the more than $1 billion spent by federal, state and local entities the past two decades to slow the flow of pollutants into the lake and restore shoreline marshes and wetlands. But for the second year in a row, on the heels of a five-year drought, the data show continuation of the worrisome trend that started eight years ago. The 2015 data showed that Tahoe's average surface temperature had risen faster over the previous four years than any time on record — 15 times faster than the long-term warming rate over the past half century. In 2016, the temperature was again at record levels, and the lake stratified — or separated into distinct layers — at close to the earliest time of year ever. "We get less mixing of the lake in the summer," Schladow said. Less mixing means tiny particles of algae remain near the surface longer, gathering sunlight and collecting nutrients that spur their growth and reduce clarity. As a result, the 2016 numbers tell a tale of two lakes. Average winter clarity was 83 feet (25.3 meters), the clearest since 2012. But summer clarity averaged 56 feet (17 meters), about 16 feet (4.9 meters) worse than 2015. The summer declines were so big they outweighed the winter improvements — something scientists didn't anticipate. Despite 2016's decline, the data indicate Tahoe's long-term trend of clarity loss ended about 15 years ago. Since then, it's hovered around 71 feet (22 meters) but with significant variability. In fact last Jan. 25, the disk was visible at an "astounding" 95 feet (29 meters), Schladow said. "The exciting thing is this is confirming that the bottom of the lake — probably 90 percent of the water in the lake — is still crystal clear."


News Article | May 23, 2017
Site: hosted2.ap.org

(AP) — Climate change is causing Lake Tahoe to warm sooner in the spring than it has historically, disrupting the normal mixing of shallow and deep water and undercutting gains made in reversing the loss of clarity of the cobalt mountain lake, scientists say. "Climate change is impacting not only Lake Tahoe's water quality, but also the health of its forests and its recreation-based economy," said Joanne Marchetta, executive director of the Tahoe Regional Planning Agency, which regulates the lake covering 191 square miles (495 sq. kilometers) along the Nevada-California border. Until recently, the climatological cycles affecting Tahoe's clarity had remained fairly constant since 1968, when experts first dropped a white disk into the lake to measure how far down it remained visible. Back then, it was more than 102 feet (31 meters) compared to an average of about 69 feet (21 meters) now. Dry years resulted in clearer water. Storm-water runoff carrying soils and contaminants during wet years made it worse. " You didn't need a Ph.D. to understand it," said Geoff Schladow, director of the University of California Davis Tahoe Environmental Research Center. But the pattern seems to be breaking down, he said. "What we are learning is that climate change isn't just a one-size-fits-all thing," he said in an interview. "It's not just warmer air temperatures or more extreme winters or droughts. It's a combination of all of these things." Average annual clarity for 2016 was about 4 feet (1.2 meters) worse than the 73 feet (22 meters) recorded in 2015, but better than the worst-recorded average of 64 feet (19 meters) in 1997. Marchetta says the improvements are a testament to the more than $1 billion spent by federal, state and local entities the past two decades to slow the flow of pollutants into the lake and restore shoreline marshes and wetlands. But for the second year in a row, on the heels of a five-year drought, the data show continuation of the worrisome trend that started eight years ago. The 2015 data showed that Tahoe's average surface temperature had risen faster over the previous four years than any time on record — 15 times faster than the long-term warming rate over the past half century. In 2016, the temperature was again at record levels, and the lake stratified — or separated into distinct layers — at close to the earliest time of year ever. "We get less mixing of the lake in the summer," Schladow said. Less mixing means tiny particles of algae remain near the surface longer, gathering sunlight and collecting nutrients that spur their growth and reduce clarity. As a result, the 2016 numbers tell a tale of two lakes. Average winter clarity was 83 feet (25.3 meters), the clearest since 2012. But summer clarity averaged 56 feet (17 meters), about 16 feet (4.9 meters) worse than 2015. The summer declines were so big they outweighed the winter improvements — something scientists didn't anticipate. Despite 2016's decline, the data indicate Tahoe's long-term trend of clarity loss ended about 15 years ago. Since then, it's hovered around 71 feet (22 meters) but with significant variability. In fact last Jan. 25, the disk was visible at an "astounding" 95 feet (29 meters), Schladow said. "The exciting thing is this is confirming that the bottom of the lake — probably 90 percent of the water in the lake — is still crystal clear."


News Article | May 22, 2017
Site: hosted2.ap.org

(AP) — Climate change is causing Lake Tahoe to warm sooner in the spring than it has historically, disrupting the normal mixing of shallow and deep water and undercutting gains made in reversing the loss of clarity of the cobalt mountain lake, scientists say. "Climate change is impacting not only Lake Tahoe's water quality, but also the health of its forests and its recreation-based economy," said Joanne Marchetta, executive director of the Tahoe Regional Planning Agency, which regulates the lake covering 191 square miles (495 sq. kilometers) along the Nevada-California border. Until recently, the climatological cycles affecting Tahoe's clarity had remained fairly constant since 1968, when experts first dropped a white disk into the lake to measure how far down it remained visible. Back then, it was more than 102 feet (31 meters) compared to an average of about 69 feet (21 meters) now. Dry years resulted in clearer water. Storm-water runoff carrying soils and contaminants during wet years made it worse. " You didn't need a Ph.D. to understand it," said Geoff Schladow, director of the University of California Davis Tahoe Environmental Research Center. But the pattern seems to be breaking down, he said. "What we are learning is that climate change isn't just a one-size-fits-all thing," he said in an interview. "It's not just warmer air temperatures or more extreme winters or droughts. It's a combination of all of these things." Average annual clarity for 2016 was about 4 feet (1.2 meters) worse than the 73 feet (22 meters) recorded in 2015, but better than the worst-recorded average of 64 feet (19 meters) in 1997. Marchetta says the improvements are a testament to the more than $1 billion spent by federal, state and local entities the past two decades to slow the flow of pollutants into the lake and restore shoreline marshes and wetlands. But for the second year in a row, on the heels of a five-year drought, the data show continuation of the worrisome trend that started eight years ago. The 2015 data showed that Tahoe's average surface temperature had risen faster over the previous four years than any time on record — 15 times faster than the long-term warming rate over the past half century. In 2016, the temperature was again at record levels, and the lake stratified — or separated into distinct layers — at close to the earliest time of year ever. "We get less mixing of the lake in the summer," Schladow said. Less mixing means tiny particles of algae remain near the surface longer, gathering sunlight and collecting nutrients that spur their growth and reduce clarity. As a result, the 2016 numbers tell a tale of two lakes. Average winter clarity was 83 feet (25.3 meters), the clearest since 2012. But summer clarity averaged 56 feet (17 meters), about 16 feet (4.9 meters) worse than 2015. The summer declines were so big they outweighed the winter improvements — something scientists didn't anticipate. Despite 2016's decline, the data indicate Tahoe's long-term trend of clarity loss ended about 15 years ago. Since then, it's hovered around 71 feet (22 meters) but with significant variability. In fact last Jan. 25, the disk was visible at an "astounding" 95 feet (29 meters), Schladow said. "The exciting thing is this is confirming that the bottom of the lake — probably 90 percent of the water in the lake — is still crystal clear."


News Article | May 22, 2017
Site: hosted2.ap.org

(AP) — Climate change is causing Lake Tahoe to warm sooner in the spring than it has historically, disrupting the normal mixing of shallow and deep water and undercutting gains made in reversing the loss of clarity of the cobalt mountain lake, scientists say. "Climate change is impacting not only Lake Tahoe's water quality, but also the health of its forests and its recreation-based economy," said Joanne Marchetta, executive director of the Tahoe Regional Planning Agency, which regulates the lake covering 191 square miles (495 sq. kilometers) along the Nevada-California border. Until recently, the climatological cycles affecting Tahoe's clarity had remained fairly constant since 1968, when experts first dropped a white disk into the lake to measure how far down it remained visible. Back then, it was more than 102 feet (31 meters) compared to an average of about 69 feet (21 meters) now. Dry years resulted in clearer water. Storm-water runoff carrying soils and contaminants during wet years made it worse. " You didn't need a Ph.D. to understand it," said Geoff Schladow, director of the University of California Davis Tahoe Environmental Research Center. But the pattern seems to be breaking down, he said. "What we are learning is that climate change isn't just a one-size-fits-all thing," he said in an interview. "It's not just warmer air temperatures or more extreme winters or droughts. It's a combination of all of these things." Average annual clarity for 2016 was about 4 feet (1.2 meters) worse than the 73 feet (22 meters) recorded in 2015, but better than the worst-recorded average of 64 feet (19 meters) in 1997. Marchetta says the improvements are a testament to the more than $1 billion spent by federal, state and local entities the past two decades to slow the flow of pollutants into the lake and restore shoreline marshes and wetlands. But for the second year in a row, on the heels of a five-year drought, the data show continuation of the worrisome trend that started eight years ago. The 2015 data showed that Tahoe's average surface temperature had risen faster over the previous four years than any time on record — 15 times faster than the long-term warming rate over the past half century. In 2016, the temperature was again at record levels, and the lake stratified — or separated into distinct layers — at close to the earliest time of year ever. "We get less mixing of the lake in the summer," Schladow said. Less mixing means tiny particles of algae remain near the surface longer, gathering sunlight and collecting nutrients that spur their growth and reduce clarity. As a result, the 2016 numbers tell a tale of two lakes. Average winter clarity was 83 feet (25.3 meters), the clearest since 2012. But summer clarity averaged 56 feet (17 meters), about 16 feet (4.9 meters) worse than 2015. The summer declines were so big they outweighed the winter improvements — something scientists didn't anticipate. Despite 2016's decline, the data indicate Tahoe's long-term trend of clarity loss ended about 15 years ago. Since then, it's hovered around 71 feet (22 meters) but with significant variability. In fact last Jan. 25, the disk was visible at an "astounding" 95 feet (29 meters), Schladow said. "The exciting thing is this is confirming that the bottom of the lake — probably 90 percent of the water in the lake — is still crystal clear."


News Article | May 15, 2017
Site: www.chromatographytechniques.com

To outer space and the deep ocean, add “beneath the ice” to the list of rarely charted frontiers of science exploration. There have been very few expeditions where robots dived beneath polar ice shelves to characterize and measure them. UC Davis engineering professor Alexander Forrest recently returned from one of them. Forrest led a six-member robotics team in Antarctica on the Western Ross Sea and Terra Nova Bay as part of an international expedition, LIONESS, led by the Korea Polar Research Institute. That stands for Land-Ice/Ocean Network Exploration with Semiautonomous Systems. The team spent nearly two months in January and February aboard the South Korean icebreaker R/V Araon. Their mission? Deploy two robots, or autonomous underwater vehicles (AUV) —  one to dive beneath the sea ice to map the bottom of the Nansen ice shelf, from which two Manhattan-sized icebergs broke last year. The other, a glider with wings named Storm Petrel, to patrol the front of the ice shelf for 10 days, looking for evidence of freshwater and capturing change over time. Why? Ultimately, to better predict how — and when — ice shelves collapse. “Ice shelves are melting,” Forrest said. “We know this. But we don’t know how fast they’re melting. To actually make on-site measurements is the next step. We’re trying to get a baseline understanding of what changes are happening in the Antarctic. As a global community, we don’t really understand what we’re losing.” From one pole to the other This July, the team will head in the opposite direction, to the Arctic’s Milne Fjord, where Forrest and colleagues plan to study the last epishelf lake in Canada. Epishelf lakes form when meltwater flowing off a glacier is trapped behind a floating ice shelf. As ice shelves in the Arctic disappear, so do the epishelf lakes dammed behind them. While Canada may soon be epishelf-free, others remain in Greenland and Antarctica. The research is intended to better explain time scales, as ice shelves are melting faster than scientists earlier predicted. “It comes down to understanding how this environment is now so we can understand how potential future climate scenarios will drive these systems in Greenland and Antarctica, as well,” Forrest said. When not swimming alongside polar ice, the Storm Petrel glider trades the ocean for freshwater. It’s currently settling in to its new home at Lake Tahoe, which stretches across the California and Nevada borders. The UC Davis Tahoe Environmental Research Center plans to deploy it in the lake early this summer. The plan is for the glider to take continuous measurements, provide real-time information to TERC’s network of instrumented buoys, chase storm events, and ultimately help round out the picture of the processes and impacts affecting Lake Tahoe. “Lakes are highly variable, both spatially and in time,” said Geoffrey Schladow, director of the UC Davis Tahoe Environmental Research Center. “Conventional measurements cannot capture this dynamism. But with a glider operating for weeks at a time, from the surface to the very bottom, we finally have the appropriate tool.” Lake Tahoe is getting “smarter” all the time with its network of nearshore sensors, NASA buoys and good old-fashioned manual sampling from TERC’s research vessel. But the glider can do something those other tools cannot: Move around the lake in bad weather and rough conditions. And, as nearly everyone who studies freshwater lakes can attest, bad weather — with its mixing, churning, swelling and upwelling — is when everything really interesting happens in a lake. Be it at the poles, or in a California lake, the data these robots collect are helping to shape the picture of how aquatic environments are changing, and what might be expected in the years to come.


News Article | May 15, 2017
Site: www.futurity.org

An iceberg off the inlet of Jang Bogo Station in Terra Nova Bay, Antarctica. (Credit: Damien Guihen/University of Tasmania) A teal ribbon of water flows on top of a glacier at Inaccessible Island, an extinct volcano and protected wildlife reserve in the South Atlantic Ocean. An uncommon sight, the researchers were unsure whether the ocean was rising over the ice, or whether freshwater was melting and flowing downward in this shot. The small black dots to the right of the teal green water are seals basking in the sun. (Credit: Damien Guihen/University of Tasmania) Adélie penguins live only in Antarctica. They are seen here with a seal in the background. Alex Forrest was amazed by Antarctica’s wildlife. He said that, unlike in the Arctic, wildlife in Antarctica have few predators, so they had little fear of humans. (Credit: Danielle Haulsee/University of Delaware) The underwater glider Storm Petrel makes its maiden voyage. After this initial round, the team processed the data and then sent it out again for its full 7-day mission. (Credit: Damien Guihen/University of Tasmania) Engineers Alex Forrest from UC Davis and Nathan Kemp (in orange) from Blue Ocean Monitoring ballast the autonomous underwater vehicle Gavia, testing its stability in calm water for later deployment in Terra Nova Bay in Antarctica. (Credit: Damien Guihen/University of Tasmania) UC Davis engineering professor Alex Forrest with the recovered underwater glider after its seven-day mission diving in Terra Nova Bay, Antarctica. (Credit: Damien Guihen/University of Tasmania) UC Davis engineering professor Alex Forrest, in orange jacket, and Nathan Kemp from Blue Ocean Monitoring out of Perth, Australia, do field repairs on the autonomous underwater vehicle (AUV) glider, Gavia. Much of their time was spent preparing and debugging the robots, which also included an AUV with wings, named “Storm Petrel.” (Credit: Damien Guihen/University of Tasmania) Fishing for a glider: Damien Guihen with the University of Tasmania and Xian Wei Wang, from New York University in Abu Dhabi, retrieve the autonomous underwater vehicle. (Credit Cassie Bongiovanni/University of New Hampshire) The R/V Araon, a South Korean icebreaker, moves through ice and ocean just offshore Jang Bogo Station in Antarctica. This shot was captured with an unmanned aerial vehicle. (Credit: Damien Guihen/University of Tasmania) A team of scientists is using robots to measure and map ice shelves in Antarctica, hoping to deepen our understanding of how the shelves collapse and change under the pressure of climate change. Alexander Forrest led a six-member robotics team in Antarctica on the Western Ross Sea and Terra Nova Bay as part of an international expedition, LIONESS, led by the Korea Polar Research Institute. That stands for Land-Ice/Ocean Network Exploration with Semiautonomous Systems. The team spent nearly two months in January and February aboard the South Korean icebreaker R/V Araon. Their mission: Deploy two robots, or autonomous underwater vehicles (AUV)—one to dive beneath the sea ice to map the bottom of the Nansen ice shelf, from which two Manhattan-sized icebergs broke last year. The other, a glider with wings named Storm Petrel, to patrol the front of the ice shelf for 10 days, looking for evidence of freshwater and capturing change over time. Why? Ultimately, to better predict how—and when—ice shelves collapse. “Ice shelves are melting,” says Forrest, an engineering professor at the University of California, Davis. “We know this. But we don’t know how fast they’re melting. To actually make on-site measurements is the next step. We’re trying to get a baseline understanding of what changes are happening in the Antarctic. “As a global community, we don’t really understand what we’re losing.” This July, the team will head in the opposite direction, to the Arctic’s Milne Fjord, where Forrest and colleagues plan to study the last epishelf lake in Canada. Epishelf lakes form when meltwater flowing off a glacier is trapped behind a floating ice shelf. As ice shelves in the Arctic disappear, so do the epishelf lakes dammed behind them. While Canada may soon be epishelf-free, others remain in Greenland and Antarctica. The research is intended to better explain time scales, as ice shelves are melting faster than scientists earlier predicted. “It comes down to understanding how this environment is now so we can understand how potential future climate scenarios will drive these systems in Greenland and Antarctica, as well,” Forrest says. When not swimming alongside polar ice, the Storm Petrel glider trades the ocean for freshwater. It’s currently settling in to its new home at Lake Tahoe, which stretches across the California and Nevada borders. The UC Davis Tahoe Environmental Research Center (TERC) plans to deploy it in the lake early this summer. The plan is for the glider to take continuous measurements, provide real-time information to TERC’s network of instrumented buoys, chase storm events, and ultimately help round out the picture of the processes and impacts affecting Lake Tahoe. “Lakes are highly variable, both spatially and in time,” says Geoffrey Schladow, director of TERC. “Conventional measurements cannot capture this dynamism. But with a glider operating for weeks at a time, from the surface to the very bottom, we finally have the appropriate tool.” Lake Tahoe is getting “smarter” all the time with its network of nearshore sensors, NASA buoys, and good old-fashioned manual sampling from TERC’s research vessel. But the glider can do something those other tools cannot: Move around the lake in bad weather and rough conditions. And, as nearly everyone who studies freshwater lakes can attest, bad weather—with its mixing, churning, swelling, and upwelling—is when everything really interesting happens in a lake. Be it at the poles, or in a California lake, the data these robots collect are helping to shape the picture of how aquatic environments are changing, and what might be expected in the years to come.


News Article | May 22, 2017
Site: hosted2.ap.org

(AP) — Climate change is causing Lake Tahoe to warm sooner in the spring than it has historically, disrupting the normal mixing of shallow and deep water and undercutting gains made in reversing the loss of clarity of the cobalt mountain lake, scientists say. "Climate change is impacting not only Lake Tahoe's water quality, but also the health of its forests and its recreation-based economy," said Joanne Marchetta, executive director of the Tahoe Regional Planning Agency, which regulates the lake covering 191 square miles (495 sq. kilometers) along the Nevada-California border. Until recently, the climatological cycles affecting Tahoe's clarity had remained fairly constant since 1968, when experts first dropped a white disk into the lake to measure how far down it remained visible. Back then, it was more than 102 feet (31 meters) compared to an average of about 69 feet (21 meters) now. Dry years resulted in clearer water. Storm-water runoff carrying soils and contaminants during wet years made it worse. " You didn't need a Ph.D. to understand it," said Geoff Schladow, director of the University of California Davis Tahoe Environmental Research Center. But the pattern seems to be breaking down, he said. "What we are learning is that climate change isn't just a one-size-fits-all thing," he said in an interview. "It's not just warmer air temperatures or more extreme winters or droughts. It's a combination of all of these things." Average annual clarity for 2016 was about 4 feet (1.2 meters) worse than the 73 feet (22 meters) recorded in 2015, but better than the worst-recorded average of 64 feet (19 meters) in 1997. Marchetta says the improvements are a testament to the more than $1 billion spent by federal, state and local entities the past two decades to slow the flow of pollutants into the lake and restore shoreline marshes and wetlands. But for the second year in a row, on the heels of a five-year drought, the data show continuation of the worrisome trend that started eight years ago. The 2015 data showed that Tahoe's average surface temperature had risen faster over the previous four years than any time on record — 15 times faster than the long-term warming rate over the past half century. In 2016, the temperature was again at record levels, and the lake stratified — or separated into distinct layers — at close to the earliest time of year ever. "We get less mixing of the lake in the summer," Schladow said. Less mixing means tiny particles of algae remain near the surface longer, gathering sunlight and collecting nutrients that spur their growth and reduce clarity. As a result, the 2016 numbers tell a tale of two lakes. Average winter clarity was 83 feet (25.3 meters), the clearest since 2012. But summer clarity averaged 56 feet (17 meters), about 16 feet (4.9 meters) worse than 2015. The summer declines were so big they outweighed the winter improvements — something scientists didn't anticipate. Despite 2016's decline, the data indicate Tahoe's long-term trend of clarity loss ended about 15 years ago. Since then, it's hovered around 71 feet (22 meters) but with significant variability. In fact last Jan. 25, the disk was visible at an "astounding" 95 feet (29 meters), Schladow said. "The exciting thing is this is confirming that the bottom of the lake — probably 90 percent of the water in the lake — is still crystal clear."


Acosta M.,University of Granada | Anguita M.,University of Granada | Fernandez-Baldomero F.J.,University of Granada | Ramon C.L.,University of Granada | And 3 more authors.
Environmental Modelling and Software | Year: 2015

This work evaluates the implementation of a nested Cartesian grid in a 3D semi-implicit hydrodynamic model with synthetic and real examples. The outer model provides all the values needed by the governing equations of the nesting (inner) subdomain at the boundary (including tangential velocities). A 3D flux relaxation scheme is applied to prevent mass and energy drift. The influence of tangential velocities in the solution is evaluated, showing a substantial reduction on the results' quality when they are considered negligible and lateral circulation exists. The inner/outer coupling implemented achieves a simulation time equal to the inner execution time and allows a transfer step equal to the inner time-step, removing time interpolation errors. This coupling makes feasible the 3D relaxation implemented. A dramatic improvement in memory requirements and simulation time is achieved, that allows the use of low-cost low-power consumption platforms in the simulations. © 2014 Elsevier Ltd.


News Article | August 1, 2016
Site: www.techtimes.com

Lake Tahoe has had a record-breaking year — and not in a good way. A team of scientists from the University of California, Davis (UC Davis) has revealed in a new study that Lake Tahoe is getting warmer at a rate that is 15 times faster than its historic average. In a new State of the Lake report, researchers say Lake Tahoe's rising water temperatures are threatening the lake's iconic clarity by affecting many features of its ecology. Professor Geoffrey Schladow says the incidence of rising air temperatures at the lake has been known for many years now, as well as the warming waters. But what's different this time is that scientists are seeing more aspects of Lake Tahoe's internal physics changing. "[T]hat is bound to alter the ecology," says Schladow, who is the director of the Tahoe Environmental Research Center (TERC). When researchers began keeping records of the lake's water temperature in the 1970s, the lake had an average of 50.3 degrees Fahrenheit (10.17 degrees Celsius) year round. In 2015, Lake Tahoe averaged 53.3 degrees Fahrenheit (11.83 degrees Celsius), the report says. Although the increase may appear statistically insignificant, scientists say much of the warming happened in the past decade and a half. This sign has left experts concerned. The increasing water temperatures may likely be linked to shifting air temperatures. Scientists have detected a daily air temperature increase of 4.3 degrees Fahrenheit on the northwest shore of Lake Tahoe since 1916. Waters with different temperatures mix deep in the lake during the winter. This mixing often leads to a clearer view. However, Lake Tahoe did not mix at its maximum depth this year, which scientists blame on the warmer influx of water. Water clarity dropped to 73.1 feet in 2015 — almost a 5-foot decrease in recent years. Furthermore, swimmers have observed algal blooms spread on the lake in previous years. Experts say longer algal blooms have been associated with climate change because algae likes warmer water. What is happening at Lake Tahoe is not only alarming for tourists who use the lake for recreation, but also for those concerned about the impacts of climate change to the beauty of natural resources, researchers say. Lake Tahoe is unique, but scientists explained that the forces and processes that affect it are the same as those that act in most natural ecosystems. Because of that, Lake Tahoe is a microcosm of other natural systems in the Western United States and around the world. How can residents and tourists keep the iconic lake as healthy as possible? Experts say attention to the lake's natural filtration systems as well as stormwater collection may help prevent harmful substances that accelerate the growth of algae such as phosphates out of Lake Tahoe. Darcie Goodman Collins, director of the League to Save Lake Tahoe, believes not much can be done to manipulate global warming. "But we can influence the lake's health," Goodman Collins added. Meanwhile, the UC Davis "Tahoe: State of the Lake" report can be read and downloaded (PDF) from the university's website. © 2016 Tech Times, All rights reserved. Do not reproduce without permission.


Sahoo G.B.,Tahoe Environmental Research Center | Forrest A.L.,University of Tasmania | Schladow S.G.,Tahoe Environmental Research Center | Reuter J.E.,Tahoe Environmental Research Center | And 2 more authors.
Limnology and Oceanography | Year: 2015

Using water column temperature records collected since 1968, we analyzed the impacts of climate change on thermal properties, stability intensity, length of stratification, and deep mixing dynamics of Lake Tahoe using a modified stability index (SI). This new SI is easier to produce and is a more informative measure of deep lake stability than commonly used stability indices. The annual average SI increased at 16.62 kg/m2/decade although the summer (May-October) average SI increased at a higher rate (25.42 kg/m2/decade) during the period 1968-2014. This resulted in the lengthening of the stratification season by approximately 24 d. We simulated the lake thermal structure over a future 100 yr period using a lake hydrodynamic model driven by statistically downscaled outputs of the Geophysical Fluid Dynamics Laboratory Model (GFDL) for two different green house gas emission scenarios (the A2 in which greenhouse-gas emissions increase rapidly throughout the 21st Century, and the B1 in which emissions slow and then level off by the late 21st Century). The results suggest a continuation and intensification of the already observed trends. The length of stratification duration and the annual average lake stability are projected to increase by 38 d and 12 d and 30.25 kg/m2/decade and 8.66 kg/m2/decade, respectively for GFDLA2 and GFDLB1, respectively during 2014-2098. The consequences of this change bear the hallmarks of climate change induced lake warming and possible exacerbation of existing water quality, quantity and ecosystem changes. The developed methodology could be extended and applied to other lakes as a tool to predict changes in stratification and mixing dynamics. © 2015 Association for the Sciences of Limnology and Oceanography.

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