Earlier snowmelt reduces atmospheric carbon uptake in midlatitude subalpine forests

Winchell, Taylor; Barnard, David M.; Monson, Russell K.; Burns, Sean P.; Molotch, N. P.

doi:10.1002/2016gl069769

Cited by 63 publications

(60 citation statements)

References 31 publications

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“…The results confirm previous findings in the US Pacific Northwest that the current observing network design may be insufficient in a warmer world (Gleason et al, 2017;Sproles et al, 2017). Warmer temperatures and earlier melt timing (Stewart et al, 2004) also influence the rate of meltwater production (Musselman et al, 2017), a critical determinant of streamflow (Barnhart et al, 2016), forest carbon uptake (Winchell et al, 2016), and flood hazard (Hamlet and Lettenmaier, 2007). Despite a strong negative relationship between temperature and elevation, we show a positive relationship between elevation and seasonal snowmelt rates.…”

Section: Snowmelt Response To Simulated Warmingsupporting

confidence: 79%

Snowmelt response to simulated warming across a large elevation gradient, southern Sierra Nevada, California

2017

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Abstract. In a warmer climate, the fraction of annual meltwater produced at high melt rates in mountainous areas is projected to decline due to a contraction of the snow-cover season, causing melt to occur earlier and under lower energy conditions. How snowmelt rates, including extreme events relevant to flood risk, may respond to a range of warming over a mountain front is poorly known. We present a model sensitivity study of snowmelt response to warming across a 3600 m elevation gradient in the southern Sierra Nevada, USA. A snow model was run for three distinct years and verified against extensive ground observations. To simulate the impact of climate warming on meltwater production, measured meteorological conditions were modified by +1 to +6 • C. The total annual snow water volume exhibited linear reductions (−10 % • C −1 ) consistent with previous studies. However, the sensitivity of snowmelt rates to successive degrees of warming varied nonlinearly with elevation. Middle elevations and years with more snowfall were prone to the largest reductions in snowmelt rates, with lesser changes simulated at higher elevations. Importantly, simulated warming causes extreme daily snowmelt (99th percentiles) to increase in spatial extent and intensity, and shift from spring to winter. The results offer insight into the sensitivity of mountain snow water resources and how the rate and timing of water availability may change in a warmer climate. The identification of future climate conditions that may increase extreme melt events is needed to address the climate resilience of regional flood control systems.

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Section: Snowmelt Response To Simulated Warmingsupporting

confidence: 79%

Snowmelt response to simulated warming across a large elevation gradient, southern Sierra Nevada, California

2017

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“…However, future climate predictions suggest warmer temperatures that may shift precipitation from snowfall to rain (Knowles, Dettinger, & Cayan, ; Jennings, Winchell, Livneh, & Molotch, ), cause earlier snowmelt (Stewart, Cayan, & Dettinger, ), and result in slower snowmelt rates (Musselman, Clark, Liu, Ikeda, & Rasmussen, ). Changes in the timing and rates of snowmelt have profound implications on soil moisture (Harpold et al, ; Webb, Fassnacht, & Gooseff, ), evapotranspiration (Barnhart et al, ; Winchell, Barnard, Monson, Burns, & Molotch, ), and downstream water availability (Knowles et al, ), whereas shifts in precipitation phase will affect rain‐on‐snow run‐off generation (Jennings & Jones, ; Musselman et al, ; Würzer, Jonas, Wever, & Lehning, ).…”

Section: Introductionmentioning

confidence: 99%

Hydrologic connectivity at the hillslope scale through intra‐snowpack flow paths during snowmelt

Webb

Wigmore

Jennings

et al. 2020

Hydrological Processes

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The seasonal snowmelt period is a critical component of the hydrologic cycle for many mountainous areas. Changes in the timing and rate of snowmelt as a result of physical hydrologic flow paths, such as longitudinal intra‐snowpack flow paths, can have strong implications on the partitioning of meltwater amongst streamflow, groundwater recharge, and soil moisture storage. However, intra‐snowpack flow paths are highly spatially and temporally variable and thus difficult to observe. This study utilizes new methods to non‐destructively observe spatio‐temporal changes in the liquid water content of snow in combination with plot experiments to address the research question: What is the scale of influence that intra‐snowpack flow paths have on the downslope movement of liquid water during snowmelt across an elevational gradient? This research took place in northern Colorado with study plots spanning from the rain‐snow transition zone up to the high alpine. Results indicate an increasing scale of influence from intra‐snowpack flow paths with elevation, showing higher hillslope connectivity producing larger intra‐snowpack contributing areas for meltwater accumulation, quantified as the upslope contributing area required to produce observed changes in liquid water content from melt rate estimates. The total effective intra‐snowpack contributing area of accumulating liquid water was found to be 17, 6, and 0 m2 for the above tree line, near tree line, and below tree line plots, respectively. Dye tracer experiments show capillary and permeability barriers result in increased number and thickness of intra‐snowpack flow paths at higher elevations. We additionally utilized aerial photogrammetry in combination with ground penetrating radar surveys to investigate the role of this hydrologic process at the small watershed scale. Results here indicate that intra‐snowpack flow paths have influence beyond the plot scale, impacting the storage and transmission of liquid water within the snowpack at the small watershed scale.

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“…, Winchell et al. ), we included a spatial estimate of peak annual snow water equivalent (peak SWE), which typically occurs between late March and late May in the SRME (Winchell et al. ).…”

Section: Methodsmentioning

confidence: 99%

Summer and winter drought drive the initiation and spread of spruce beetle outbreak

Hart

Veblen

Schneider

et al. 2017

Ecology

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This study used Landsat-based detection of spruce beetle (Dendroctonus rufipennis) outbreak over the years 2000-2014 across the Southern Rocky Mountain Ecoregion to examine the spatiotemporal patterns of outbreak and assess the influence of temperature, drought, forest characteristics, and previous spruce beetle activity on outbreak development. During the 1999-2013 period, time series of spruce beetle activity were highly spatially correlated (r > 0.5) at distances <5 km, but remained weakly correlated (r = 0.08) at distances >400 km. Furthermore, cluster analysis on time series of outbreak activity revealed the outbreak developed at multiple incipient locations and spread to unaffected forest, highlighting the importance of both local-scale dispersal and regional-scale drivers in synchronizing spruce beetle outbreak. Spatial overlay analysis and Random Forest modeling of outbreak development show that outbreaks initiate in areas characterized by summer, winter, and multi-year drought and that outbreak spread is strongly linked to the proximity and extent of nearby outbreak, but remains associated with drought. Notably, we find that spruce beetle outbreak is associated with low peak snow water equivalent, not just summer drought. As such, future alterations to both winter and summer precipitation regimes are likely to drive important changes in subalpine forests.

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Earlier snowmelt reduces atmospheric carbon uptake in midlatitude subalpine forests

Cited by 63 publications

References 31 publications

Snowmelt response to simulated warming across a large elevation gradient, southern Sierra Nevada, California

Snowmelt response to simulated warming across a large elevation gradient, southern Sierra Nevada, California

Hydrologic connectivity at the hillslope scale through intra‐snowpack flow paths during snowmelt

Summer and winter drought drive the initiation and spread of spruce beetle outbreak

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