Climate Change: Shorter Arctic Winters & The California Water Shortage
As I've mentioned, published scientific studies run in cycles. Here are two more about the subject of climate change that support the last post on this blog.
- "Winter" in the Arctic 24 Days Shorter than 1950
- The Water Supply for California the Lowest in a Decade
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Arctic Winter 24 Days Shorter than in 1950Research, sponsored by the European Space Agency (ESA) and published in The Cryosphere, also reveals that climate change has dramatically affected the thickness of lake ice at the coldest point in the season: In 2011, Arctic lake ice was up to 38 centimetres thinner than it was in 1950.
Click on image
"We've found that the thickness of the ice has decreased tremendously in response to climate warming in the region," said lead author Cristina Surdu, a PhD student of Professor Claude Duguay in Waterloo's Department of Geography and Environmental Management. "When we saw the actual numbers we were shocked at how dramatic the change has been. It's basically more than a foot of ice by the end of winter."
The study of more than 400 lakes o the North Slope of Alaska, is the first time researchers have been able to document the magnitude of lake-ice changes in the region over such a long period of time.
"Prior to starting our analysis, we were expecting to find a decline in ice thickness and grounded ice based on our examination of temperature and precipitation records of the past five decades from the Barrow meteorological station," said Surdu "At the end of the analysis, when looking at trend analysis results, we were stunned to observe such a dramatic ice decline during a period of only 20 years."
The research team used satellite radar imagery from ESA to determine that 62 per cent of the lakes in the region froze to the bottom in 1992. By 2011, only 26 per cent of lakes froze down to the bed, or bottom of the lake. Overall, there was a 22 per cent reduction in what the researchers call "grounded ice" from 1992 to 2011.
Researchers were able to tell the difference between a fully frozen lake and one that had not completely frozen to the bottom, because satellite radar signals behave very differently, depending on presence or absence of water underneath the ice.
Radar signals are absorbed into the sediment under the lake when it is frozen to the bottom. However, when there is water under the ice with bubbles, the beam bounces back strongly towards the radar system. Therefore, lakes that are completely frozen show up on satellite images as very dark while those that are not frozen to the lake bed are bright.
Researchers used the Canadian Lake Ice Model (CLIMo) to determine ice cover and lake ice thickness for those years before 1991, when satellite images are not available.
Winter 24 Days Shorter in the Arctic
The model simulations show that lakes in the region froze almost six days later and broke up about 18 days earlier in the winter of 2011 compared to the winter of 1950. Shorter ice-cover seasons may lead to shifts in lake algal productivity as well as thawing of permafrost under lake beds.
"The changes in ice and the shortened winter affect Northern communities that depend on ice roads to transport goods," said Surdu. "The dramatic changes in lake ice may also contribute to further warming of the entire region because open water on lakes contribute to warmer air temperatures, albeit to a lesser extent than open sea water."
California Water Supply Lowest in a Decade
Satellite data show that California's Sacramento and San Joaquin River basins are at near decade-low water storage levels. These and other findings on the State's dwindling water resources were documented in an advisory report released today from the UC Center for Hydrologic Modeling (UCCHM) at the University of California, Irvine.
Responding to Governor Jerry Brown's recent declaration of a drought emergency in California, a team of UCCHM researchers has updated its research on the state's two largest river basins, and the source of most its water. The region also encompasses the Central Valley, the most productive agriculture region in the country. The Central Valley depends entirely on the surface and groundwater resources within the river basins to meet its irrigation needs and to produce food for the nation.
Using satellite data from NASA's Gravity Recovery and Climate Experiment (GRACE) mission, the researchers, led by UCCHM Director and UC Irvine Professor Jay Famiglietti, found that as of November 2013, total water storage in the river basins -- the combination of all of the snow, surface water, soil moisture and groundwater, and an integrated measure of basin-wide water availability -- had declined to its lowest point in nearly a decade. GRACE data for the record-dry 2013-2014 winter months were not yet available for analysis.
The data show particularly steep water losses between November 2011 and November 2013, the early phase of the current drought. Famiglietti and fellow UCCHM researchers estimate that the basins have already lost 10 cubic kilometers of fresh water in each of the last two years -- equivalent to virtually all of California's urban and household water use each year. "That's the steepest decline in total water storage that we've seen in California since the GRACE mission was launched in 2002," Famiglietti said.
Researchers noted that snow pack, surface water and soil moisture storage in the river basins were all at their lowest points in nearly a decade, illustrating a growing threat to groundwater supplies in the Central Valley, and highlighting the urgent need to manage them sustainably. Groundwater is typically viewed as a strategic reserve that supplements sparse surface water supplies in times of drought.
By combining their satellite-based estimates of 10 years (October 2003 -- November 2013) of Central Valley groundwater storage changes with long-term estimates of groundwater losses from the U. S. Geological Survey, the researchers noted that steep declines in groundwater storage are typical during droughts, when Central Valley farmers are forced to rely more heavily on groundwater to meet irrigation demands.
The advisory report underscores that the rates of declining groundwater storage during drought almost always outstrip rates of groundwater replenishment during wet periods, and raises fears about the impact of long-term groundwater depletion on sustaining a reliable water supply in the current, record-setting drought. The team's previous 2011 study estimated that the Central Valley lost 20 cubic kilometers of groundwater during the 2006-2010 drought.
Communities on track to run out of water within months
Historically, drought conditions and groundwater depletion in the Central Valley are responsible for widespread land subsidence, reductions in planted acreage, higher food costs and ecological damage.
Famiglietti notes that if the drought continues "Central Valley groundwater levels will fall to all-time lows." Stephanie Castle, a UCCHM researcher who contributed to the report, believes that groundwater supplies should be more actively managed. Castle states that "the path of groundwater use that we are on threatens the sustainability of future water supplies for all Californians." She noted that several communities within the state are on track to run out of water within the next few months.
* * * * *Story Sources:
- Based on materials provided by University of Waterloo. Journal Reference: C. M. Surdu, C. R. Duguay, L. C. Brown, D. Fernández Prieto. Response of ice cover on shallow lakes of the North Slope of Alaska to contemporary climate conditions (1950–2011): radar remote-sensing and numerical modeling data analysis. The Cryosphere, 2014
- Based on materials provided by UC Center for Hydrologic Modeling. "Satellites show 'total' California water storage at near-decade low." ScienceDaily.