Earlier snowmelt periods associated with a warming climate may hinder subalpine forest regulation of atmospheric carbon dioxide (CO2), according to the results of a new University of Colorado Boulder study.
The findings, , predict that this shift in the timing of the snowmelt could result in a 45 percent reduction of snowmelt period forest carbon uptake by mid-century.
A separate study, , found that earlier, slower snowmelt reduces the amount of streamflow, a phenomenon which could have potentially drastic consequences for agriculture, municipal water supplies and recreational opportunities in Colorado and other areas of the western U.S.
Forests located in seasonally snow-covered areas represent a key terrestrial CO2 sink thanks to the natural photosynthetic processes by which trees absorb carbon. The trees鈥� carbon uptake is restrained during winter, but increases to peak capacity in spring when snowmelt provides sustained water input.
Working at the Niwot Ridge site in Colorado鈥檚 Rocky Mountains, 抖阴短视频 Boulder researchers studied 15 years鈥� worth of snowmelt and atmospheric CO2 data to study the effects of snowmelt periods. The research found that earlier snowmelt periods triggered by climate change align with colder air temperatures, reducing the forests鈥� ability to take CO2 out of the atmosphere.
鈥淭his study shows us that, counterintuitively, warming generally causes snow to melt during colder periods of the seasonal temperature cycle earlier in the year,鈥� said Taylor Winchell, a graduate researcher in the and lead author of the study. 鈥淭he colder temperatures associated with early melt reduce the trees鈥� ability to uptake carbon during the snowmelt period.鈥�
鈥淭he implications of this research are quite profound as mountains in the western U.S. are an important part of the regional cycling of carbon and water,鈥� said Noah Molotch, the director of INSTAAR鈥檚 and a co-author of both new studies. 鈥淚n this regard, earlier snowmelt will reduce carbon uptake in mountain forests, weakening the ability of forests to offset increases in CO2 associated with human burning of fossil fuels.鈥�
Snowmelt also acts as a key hydrological driver for rivers and streams across the state, providing water resources to downstream communities. Previous research has suggested that the timing and rate at which snow melts can impact the amount and quality of water available for vegetation, farming and fishing.
The researchers used a unique modeling system to study the effects of earlier snowmelt across various regions of western United States including the Cascade range, the Sierra Nevada range, the Wasatch range and the Rocky Mountains. All of these areas see significant seasonal snow accumulation and generate water resources for downstream communities.
The study results show that earlier, slower snowmelt, triggered by warmer temperatures, reduce streamflow. These slower 鈥渢rickle鈥� melts reduce percolation in hillslope soil and allow more water to evaporate, resulting in less streamflow overall.
鈥淥f all the regions we studied, streamflow from Colorado鈥檚 Rocky Mountains is most sensitive to a change in snowmelt,鈥� said Theodore Barnhart, a graduate researcher at INSTAAR and lead author of the study. 鈥淭his analysis suggests that all of the regions studied will experience a decrease in streamflow with a decrease in snowmelt rate, with some regions exhibiting more streamflow sensitivity than others.鈥�
鈥淕iven that 60 million people in the western U.S. depend on snowmelt for their water supply, the future decline in snowmelt-derived streamflow may place additional stress on over-allocated water supplies,鈥� said Molotch.
Additional co-authors of the study 鈥淓arlier snowmelt reduces atmospheric carbon uptake in midlatitude subalpine forests鈥� include David Barnard and Sean Burns of 抖阴短视频 Boulder and Russell Monson of the University of Arizona. The work was funded by NSF, the U.S. Department of Energy, the U.S. Department of Agriculture and the Niwot Ridge Long-Term Ecological Research Program.
Additional co-authors of the study 鈥淪nowmelt rate dictates streamflow鈥� include Ben Livneh of the Cooperative Institute for Research in Environmental Sciences (CIRES) at 抖阴短视频 Boulder; John Knowles and Dominik Schneider of 抖阴短视频 Boulder; and Adrian Harpold of the University of Nevada. The work was funded by NSF with additional assistance from the U.S. Department of Agriculture and a NASA Earth and Space Science Fellowship.
Contact:
Taylor Winchell, 619-933-4942
taylor.winchell@colorado.edu
Theodore Barnhart, 206-948-1487
theodore.barnhart@colorado.edu
Noah Molotch, 303-492-6151
noah.molotch@colorado.edu
Trent Knoss, 抖阴短视频 Boulder media relations, 303-735-0528
trent.knoss@colorado.edu
