Magnitude and frequency of wet years under a megadrought climate in the western Great Basin, USA

Hatchett, Benjamin J.; Boyle, Douglas P.; Garner, Christopher B.; Kaplan, Michael L.; Putnam, Aaron E.; Bassett, Scott

doi:10.1016/j.quascirev.2016.09.017

Cited by 26 publications

(19 citation statements)

References 36 publications

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“…Changes in precipitation extremes are among the most concerning facets of climate change today, yet much uncertainty remains as to how these changes will impact hydrology and landscape evolution in any particular region (Pfahl et al, 2017). In the western USA, paleoclimate records (Hatchett et al, 2015(Hatchett et al, , 2016, climate models (Flint and Flint, 2012;Warner et al, 2015;Swain et al, 2018), and measured rising incidence of landfalling atmospheric-river storms (Russo et al, 2013;Gershunov et al, 2017) indicate that megadroughts separated by years in which large storms cause greater winter precipitation than normally occurs todaythe situation that unfolded in California between 2012 and 2017is likely to define the regional climatic scenario in future decades. Here we examine and synthesize the fluvial and coastal response of the San Lorenzo River to extreme hydroclimatic conditions that have been suggested as part of the 'new normal' for future US West Coast climate.…”

Section: Discussionmentioning

confidence: 99%

A regime shift in sediment export from a coastal watershed during a record wet winter, California: Implications for landscape response to hydroclimatic extremes

East

Stevens

Ritchie

et al. 2018

Earth Surf Processes Landf

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Small, steep watersheds are prolific sediment sources from which sediment flux is highly sensitive to climatic changes. Storm intensity and frequency are widely expected to increase during the 21st century, and so assessing the response of small, steep watersheds to extreme rainfall is essential to understanding landscape response to climate change. During record winter rainfall in 2016–2017, the San Lorenzo River, coastal California, had nine flow peaks representing 2–10‐year flood magnitudes. By the third flood, fluvial suspended sediment showed a regime shift to greater and coarser sediment supply, coincident with numerous landslides in the watershed. Even with no singular catastrophic flood, these flows exported more than half as much sediment as had a 100‐year flood 35 years earlier, substantially enlarging the nearshore delta. Annual sediment load in 2017 was an order of magnitude greater than during an average‐rainfall year, and 500‐fold greater than in a recent drought. These anomalous sediment inputs are critical to the coastal littoral system, delivering enough sediment, sometimes over only a few days, to maintain beaches for several years. Future projections of megadroughts punctuated by major atmospheric‐river storm activity suggest that interannual sediment‐yield variations will become more extreme than today in the western USA, with potential consequences for coastal management, ecosystems, and water‐storage capacity. The occurrence of two years with major sediment export over the past 35 years that were not associated with extremes of the El Niño Southern Oscillation or Pacific Decadal Oscillation suggests caution in interpreting climatic signals from marine sedimentary deposits derived from small, steep, coastal watersheds, to avoid misinterpreting the frequencies of those cycles. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

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Section: Discussionmentioning

confidence: 99%

A regime shift in sediment export from a coastal watershed during a record wet winter, California: Implications for landscape response to hydroclimatic extremes

East

Stevens

Ritchie

et al. 2018

Earth Surf Processes Landf

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“…This warming is expected to produce wetter, stronger atmospheric rivers [12], that in turn will contribute to shallower snowpacks and a greater potential for rain-on-snow events and flooding [9,10,54,55]. These changes also may limit drought recovery during occasional wetter years that occur during persistent droughts [65]. Warming background temperatures combined with changes from snow to rain leads to decreased water availability in spring and throughout the warm season [4,[66][67][68].…”

Section: Discussionmentioning

confidence: 99%

Winter Snow Level Rise in the Northern Sierra Nevada from 2008 to 2017

Hatchett

Daudert

Garner

et al. 2017

Water

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Abstract:The partitioning of precipitation into frozen and liquid components influences snow-derived water resources and flood hazards in mountain environments. We used a 915-MHz Doppler radar wind profiler upstream of the northern Sierra Nevada to estimate the hourly elevation where snow melts to rain, or the snow level, during winter (December-February) precipitation events spanning water years (WY) 2008-2017. During this ten-year period, a Mann-Kendall test indicated a significant (p < 0.001) positive trend in snow level with a Thiel-Sen slope of 72 m year −1 . We estimated total precipitation falling as snow (snow fraction) between WY1951 and 2017 using nine daily mid-elevation (1200-2000 m) climate stations and two hourly stations spanning WY2008-2017. The climate-station-based snow fraction estimates agreed well with snow-level radar values (R 2 = 0.95, p < 0.01), indicating that snow fractions represent a reasonable method to estimate changes in frozen precipitation. Snow fraction significantly (p < 0.001) declined during WY2008-2017 at a rate of 0.035 (3.5%) year −1 . Single-point correlations between detrended snow fraction and sea-surface temperatures (SST) suggested that positive SST anomalies along the California coast favor liquid phase precipitation during winter. Reanalysis-derived integrated moisture transported upstream of the northern Sierra Nevada was negatively correlated with snow fraction (R 2 = 0.90, p < 0.01), with atmospheric rivers representing the likely circulation mechanism producing low-snow-fraction storms.

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“…This combination of decreased moisture transport from the south-west and stronger northerly meridional winds is consistent with other modeling studies investigating hydroclimatic variability in western North America at other times. Namely, reduced moisture transport from the south-west, possibly due to fewer atmospheric river storms, may have driven megadrought conditions in the Walker Lake Basin during the Medieval Climate Anomaly (Hatchett et al, 2016). Likewise, models robustly predict drying northerly winds will influence south-western North America in global warming scenarios (Simpson et al, 2016).…”

Section: R I V I N G M E C H a N I S M S O F M I D -H O L O C E N Ementioning

confidence: 99%

Spatial patterns and driving mechanisms of mid‐Holocene hydroclimate in western North America

Hermann

Oster

Ibarra

2018

J Quaternary Science

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Mid‐Holocene paleoclimate proxy records from drought‐sensitive western North America suggest widespread aridity in areas dominated by winter precipitation. We present spatial comparisons of a diverse network of moisture‐sensitive proxies with 12 global circulation model simulations from the Paleoclimate Model Intercomparison Project to determine the most important atmospheric drivers behind observed mid‐Holocene aridity in this region. Although model‐proxy agreement is low for most models, in part reflecting small mid‐Holocene precipitation anomalies, three show relatively strong agreement by successfully simulating arid conditions across the Pacific Northwest. The model that shows the strongest spatial agreement with the proxy network reveals an anticyclonic wind anomaly that is similar to but weaker than anomalies noted during west‐wide drought episodes of the past 500 years. This model suggests increased transient upper level ridging that reduced winter water vapor transport from the south‐west during the mid‐Holocene. These mechanisms are similar to those suggested to have supported megadrought conditions in western North America during the Medieval Climate Anomaly and which are also simulated in anthropogenic warming scenarios. Future work on quantitative proxy records to enhance temporal and spatial coverage, and explicitly address issues of seasonality, will improve the quality of future climate model–data comparison studies.

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Magnitude and frequency of wet years under a megadrought climate in the western Great Basin, USA

Cited by 26 publications

References 36 publications

A regime shift in sediment export from a coastal watershed during a record wet winter, California: Implications for landscape response to hydroclimatic extremes

A regime shift in sediment export from a coastal watershed during a record wet winter, California: Implications for landscape response to hydroclimatic extremes

Winter Snow Level Rise in the Northern Sierra Nevada from 2008 to 2017

Spatial patterns and driving mechanisms of mid‐Holocene hydroclimate in western North America

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