Drained lake holds record of ancient Alaska





Mountain lake is telling an interesting story about the Alaskan climate
Mountain lake is telling an interesting story about the Alaskan climate

Not too long ago, a lake sprung a leak in the high country of the Wrangell-St. Elias Mountains. The lake drained away, as glacier-dammed lakes often do, but this lake was a bit different, and seems to be telling a story about a warmer Alaska.



The lake, known as Iceberg Lake to people in McCarthy, about 50 air miles to the north, had been part of the landscape for as long as people could remember. Pinched by glacial ice, the three-mile-long, one-mile-wide lake on the northern boundary of the Bagley Icefield was remote but notable enough that it was the cover photo for a recent book about hiking Wrangell-St. Elias National Park.



When McCarthy guide Richard Villa visited the area with a client in the summer of 1999, he was stunned to see the lake, which had lost much of its water. Villa later told Mike Loso, a Kennicott resident part of the year and now a professor at Alaska Pacific University in Anchorage.



Loso flew to the lake the next summer with Bob Anderson and Dan Doak, scientists who also reside in McCarthy for part of the year. The men saw a muddy lakebed where Iceberg Lake had sat for so long. Streams of meltwater had cut though the mud, making sharp canyons. Loso, Anderson, and Doak hiked into the gullies and saw on the walls many layers of the former lake bottom. They knew that each two layers of sediment–a thinner layer of fine-grained deposits that settled in winter and coarser sand forced in with summer runoff–represented a year in the life of the lake.



“We eyeballed these layers and said ‘Wow, there’s at least 1,000 of these things,'” Loso said.



Scientists often pull plugs of sediment from the bottom of lakes to find an ancient record of pollen, dust, ash, and other things that have drifted, or flowed in over the years, but their records usually don’t go back farther than the Little Ice Age, a cold period from about 1600 to 1850 when many glaciers advanced. Those glaciers plowed over most of the landscape, but Iceberg Lake seemed to have escaped the gradual assault.


“(Iceberg Lake) is pinned between these two glaciers just far enough away that it didn’t get overrun by the Little Ice Age (glaciers),” Loso said.



So instead of having a record of just the last few hundred years, the floor of Iceberg Lake held a continuous record from 1998 back to A.D. 442, a span of more than 1,500 years.



That record is unique in that it seems to preserve a time of warmer temperatures called the Medieval Warm Period that happened before the Little Ice Age.



“It’s the most recent time period warm enough to be comparable to the present,” Loso said.



When Loso and his colleagues used the thickness of layers (called “varves”) to interpret warmth in the area of Iceberg Lake, they found that summer temperatures in that part of the state were warmer in the late 20th century than they were during the Medieval Warm Period.



Not only that, they saw that Iceberg Lake had never drained during the Medieval Warm Period. Since the catastrophic leakage in 1999, the lake has drained of meltwater every year except for 2001. With such erratic behavior after centuries of stability, Iceberg Lake might be saying that Alaska has been warmer recently than it has been in a long, long time.

Lake Mead Could Be Dry by 2021





A map of the Colorado River basin.
A map of the Colorado River basin.

There is a 50 percent chance Lake Mead, a key source of water for millions of people in the southwestern United States, will be dry by 2021 if climate changes as expected and future water usage is not curtailed, according to a pair of researchers at Scripps Institution of Oceanography, UC San Diego.



Without Lake Mead and neighboring Lake Powell, the Colorado River system has no buffer to sustain the population of the Southwest through an unusually dry year, or worse, a sustained drought. In such an event, water deliveries would become highly unstable and variable, said research marine physicist Tim Barnett and climate scientist David Pierce.



Barnett and Pierce concluded that human demand, natural forces like evaporation, and human-induced climate change are creating a net deficit of nearly 1 million acre-feet of water per year from the Colorado River system that includes Lake Mead and Lake Powell. This amount of water can supply roughly 8 million people. Their analysis of Federal Bureau of Reclamation records of past water demand and calculations of scheduled water allocations and climate conditions indicate that the system could run dry even if mitigation measures now being proposed are implemented.



The paper, “When will Lake Mead go dry?,” has been accepted for publication in the peer-reviewed journal Water Resources Research, published by the American Geophysical Union (AGU), and is accessible via the AGU’s website (see instructions below).



“We were stunned at the magnitude of the problem and how fast it was coming at us,” said Barnett. “Make no mistake, this water problem is not a scientific abstraction, but rather one that will impact each and every one of us that live in the Southwest.”



“It’s likely to mean real changes to how we live and do business in this region,” Pierce added.



The Lake Mead/Lake Powell system includes the stretch of the Colorado River in northern Arizona. Aqueducts carry the water to Las Vegas, Los Angeles, San Diego, and other communities in the Southwest. Currently the system is only at half capacity because of a recent string of dry years, and the team estimates that the system has already entered an era of deficit.


“When expected changes due to global warming are included as well, currently scheduled depletions are simply not sustainable,” wrote Barnett and Pierce in the paper.



Barnett and Pierce note that a number of other studies in recent years have estimated that climate change will lead to reductions in runoff to the Colorado River system. Those analyses consistently forecast reductions of between 10 and 30 percent over the next 30 to 50 years, which could affect the water supply of between 12 and 36 million people.



The researchers estimated that there is a 10 percent chance that Lake Mead could be dry by 2014. They further predict that there is a 50 percent chance that reservoir levels will drop too low to allow hydroelectric power generation by 2017.



The researchers add that even if water agencies follow their current drought contingency plans, it might not be enough to counter natural forces, especially if the region enters a period of sustained drought and/or human-induced climate changes occur as currently predicted.



Barnett said that the researchers chose to go with conservative estimates of the situation in their analysis, though the water shortage is likely to be more dire in reality. The team based its findings on the premise that climate change effects only started in 2007, though most researchers consider human-caused changes in climate to have likely started decades earlier. They also based their river flow on averages over the past 100 years, even though it has dropped in recent decades. Over the past 500 years the average annual flow is even less.



“Today, we are at or beyond the sustainable limit of the Colorado system. The alternative to reasoned solutions to this coming water crisis is a major societal and economic disruption in the desert southwest; something that will affect each of us living in the region” the report concluded.



The research was supported under a joint program between UC San Diego and the Lawrence Livermore National Laboratory and by the California Energy Commission. The views expressed here do not necessarily represent the views of the California Energy Commission, its employees, or the state of California.

Do Hydroelectric Dams Pose A New Threat To Lake Victoria?





Two hydroelectricity dams appear to be threatening the health of Lake Victoria -- and of the people living along its shores who depend on the lake for food.
Two hydroelectricity dams appear to be threatening the health of Lake Victoria — and of the people living along its shores who depend on the lake for food.

Two hydroelectricity dams appear to be threatening the health of Lake Victoria — and of the people living along its shores who depend on the lake for food. A new study┬╣ suggests that the dams’ systematic overuse of water has decreased the lake level by at least two meters between 2000 and 2006 — and that this drop was not influenced by weather.



The two dams, both located at the outlet of Lake Victoria in Uganda, have been using water at a rate of 20 to 50 percent above the allowable discharge agreed by Uganda and Egypt in 1957. Meanwhile, the dramatic drop in water level has dried the papyrus wetlands fringing the lake, resulting in an 80 percent collapse in tilapia fisheries recruitment – the juvenile fish using the wetlands as a refuge.



A key staple of the local population living along the lake’s shores, this loss of the tilapia fish threatens the food security of people depending on the lake in Uganda, Kenya and Tanzania. In the long term, the commercially fished Nile Perch, which feeds on smaller fish such as tilapia, could also be affected.



Additional impacts of the drop in water level include increased eutrophication* and algal blooms. When submerged, the surrounding papyrus wetlands previously buffered the lake from excess levels of nitrogen and phosphorus; they could absorb about half of the nitrogen, and a quarter of the phosphorus, which flows into the lake. With the wetland now much drier, much of this function has been lost.



If overdrawing of water leads to permanent drying of these wetlands, the implications could be far-reaching, with large-scale eutrophication of the lake, exacerbation of invasion by the non-native water hyacinth, and accelerated global warming as the dried papyrus and its peat are burned to claim land for agriculture, duplicating the disastrous forest and peat fires in Indonesia.



In the authors’ view, “the future of Lake Victoria and its people is very closely related to the future of its papyrus wetlands.” They are calling on the states along the lakeshores, Kenya, Uganda and Tanzania, to urgently address the issue of managing the lake level in a way that involves all stakeholders.



Journal reference: Kiwango YA, Wolanski E (2008). Papyrus wetlands, nutrients balance, fisheries collapse, food security and Lake Victoria level decline in 2000-2006. Wetlands Ecology and Management (DOI 10.1007/s11273-007-9072-4)



The study was authored by Yustina Kiwango of Tanzania National Parks and Eric Wolanski of James Cook University in Australia.



*Eutrophication: the process by which a body of water becomes enriched in dissolved nutrients that stimulate the growth of aquatic plant life usually resulting in the depletion of dissolved oxygen.

Exploration Of Lake Hidden Beneath Antarctica’s Ice Sheet Begins





The exploration of sub-glacial Lake Ellsworth. Seismic charges (blue) send waves down through the ice. Waves are reflected back to the surface and analyzed (red). (Credit: Image courtesy of British Antarctic Survey)
The exploration of sub-glacial Lake Ellsworth. Seismic charges (blue) send waves down through the ice. Waves are reflected back to the surface and analyzed (red). (Credit: Image courtesy of British Antarctic Survey)

A four-man science team led by British Antarctic Survey’s (BAS) Dr Andy Smith has begun exploring an ancient lake hidden deep beneath Antarctica’s ice sheet. The lake — the size of Lake Windermere (UK) — could yield vital clues to life on Earth, climate change and future sea-level rise.



Glaciologist Dr Smith and his colleagues from the Universities of Edinburgh and Northumbria are camped out at one of the most remote places on Earth conducting a series of experiments on the ice. He says,



“This is the first phase of what we think is an incredibly exciting project. We know the lake is 3.2km beneath the ice; long and thin and around 18 km2 in area. First results from our experiments have shown the lake is 105m deep. This means Lake Ellsworth is a deep-water body and confirms the lake as an ideal site for future exploration missions to detect microbial life and recover climate records.


“If the survey work goes well, the next phase will be to build a probe, drill down into the lake and explore and sample the lake water. The UK could do this as soon as 2012/13.”



This ambitious exploration of ‘subglacial’ Lake Ellsworth, West Antarctica, involves scientists from 14 UK universities and research institutes, as well as colleagues from Chile, USA, Sweden, Belgium, Germany and New Zealand. The International Polar Year* project Principal Investigator is Professor Martin Siegert from the University of Edinburgh. He says,



“We are particularly interested in Lake Ellsworth because it’s likely to have been isolated from the surface for hundreds of thousands of years. Radar measurements made previously from aircraft surveys suggest that the lake is connected to others that could drain ice from the West Antarctic Ice sheet to the ocean and contribute to sea-level rise.”



Professor Siegert is already planning the lake’s future exploration. He continues, “Around 150 lakes have been discovered beneath Antarctica’s vast ice sheet and so far little is known about them. Getting into the lake is a huge technological challenge but the effort is worth it. These lakes are important for a number of reasons. For example, because water acts as a lubricant to the ice above they may influence how the ice sheet flows. Their potential for unusual life forms could shed new light on evolution of life in harsh conditions; lake-floor sediments could yield vital clues to past climate. They can also help us understand the extraterrestrial environment of Europa (one of the moons of Jupiter).”