[MCN] Mountain streams face combined climate hits?: Snow loss, and ...

[Lance Olsen]

Environmental Research Letters  Published 13 April 2016
http://dx.doi.org/10.1088/1748-9326/11/4/044015
OPEN ACCESS

Energy budget increases reduce mean streamflow 
more than snow-rain transitions: using integrated 
modeling to isolate climate change impacts on 
Rocky Mountain hydrology
Lauren M Foster, Lindsay A Bearup, Noah P 
Molotch, Paul D Brooks and Reed M Maxwell

Abstract (Open access)
http://iopscience.iop.org/article/10.1088/1748-9326/11/4/044015

In snow-dominated mountain regions, a warming 
climate is expected to alter two drivers of 
hydrology: (1) decrease the fraction of 
precipitation falling as snow; and (2) increase 
surface energy available to drive 
evapotranspiration. This study uses a novel 
integrated modeling approach to explicitly 
separate energy budget increases via warming from 
precipitation phase transitions from snow to rain 
in two mountain headwaters transects of the 
central Rocky Mountains. Both phase transitions 
and energy increases had significant, though 
unique, impacts on semi-arid mountain hydrology 
in our simulations. A complete shift in 
precipitation from snow to rain reduced 
streamflow between 11% and 18%, while 4 °C of 
uniform warming reduced streamflow between 19% 
and 23%, suggesting that changes in energy-driven 
evaporative loss, between 27% and 29% for these 
uniform warming scenarios, may be the dominant 
driver of annual mean streamflow in a warming 
climate. Phase changes induced a flashier system, 
making water availability more susceptible to 
precipitation variability and eliminating the 
runoff signature characteristic of 
snowmelt-dominated systems. The impact of a phase 
change on mean streamflow was reduced as aridity 
increased from west to east of the continental 
divide.
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"The greatest disturbances of which we are aware 
are those now being introduced by man himself. 
Since his tampering with the biological and 
geochemical balances may ultimately prove 
injurious -- even fatal -- to himself, he must 
understand them better than today."

"The acceleration in the consumption of fossil 
fuels implies that the amount of carbon dioxide 
in the atmosphere will keep climbing ...... A 
fundamental question is : What will happen over 
the next 100
or 1,000 years? Clearly the exponential changes cannot continue."

Bert Bolin. "The Carbon Cycle."
Scientific American, September 1970


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