scholarly journals Holocene climate and oceanography of the coastal Western United States and California Current System

2021 ◽  
Author(s):  
Hannah M. Palmer ◽  
Veronica Padilla Vriesman ◽  
Caitlin M. Livsey ◽  
Carina R. Fish ◽  
Tessa M. Hill
Keyword(s):  
United States ◽  
Pacific Northwest ◽  
Fire History ◽  
Variable Interval ◽  
Sea Surface ◽  
Western United States ◽  
Human Populations ◽  
Holocene Climate ◽  
California Current System ◽  
The Holocene

Abstract. To understand and contextualize modern climate change, we must improve our understanding of climatic and oceanographic changes in the Holocene (11.75 ka–present). Climate records of the Holocene can be utilized as a “baseline” from which to compare modern climate and can also provide insights into how environments and ecosystems experience and recover from environmental change. However, individual studies on Holocene climate in the literature tend to focus on a distinct geographic location, a specific proxy record, or a certain aspect of climate (e.g., upwelling or precipitation), resulting in localized, record-specific trends rather than a comprehensive view of climate variability through the Holocene. Here we synthesize the major oceanographic and terrestrial changes that have occurred in the Western United States (bounded by 30° N to 52° N and 115° W to 130° W) through the most recent 11.75 ka and explore the impacts of these changes on marine and terrestrial ecosystems and human populations. This three-tiered systematic review combines interpretations from over 100 published studies, codes and geospatially analyzes temperature, hydroclimate, and fire history from over 50 published studies, and interprets nine representative time series through the Holocene. We find that the early Holocene is characterized by warming relative to pre-Holocene conditions, including warm sea surface conditions, a warm and dry Pacific Northwest, a warm and wet Southwest, and overall spatial and temporal stability. In the mid Holocene, these patterns reverse; this interval is characterized by cool sea surface temperatures, a cool and wet Pacific Northwest and warm and dry Southwest. The late Holocene is the most variable interval, both spatially and temporally, and a novel spatial trend appears in terrestrial climate with warmer coastal areas and cooler inland areas. Human communities interacted with the environment throughout the entire Holocene, as evidenced in archeological and paleoenvironmental records, yet the recent era of colonization (1850–present) represents an unprecedented environmental interval in many records. Overall, our analysis shows linkages between terrestrial and oceanographic conditions, distinct environmental phases through time, and emphasizes the importance of local factors in controlling climate through the dynamic Holocene.

Identification of Resistance to Powdery Mildew in Publicly Available Male Hop Germplasm

2018 ◽  
Vol 19 (3) ◽  
pp. 258-264
Author(s):  
David H. Gent ◽  
Briana J. Claassen ◽  
Megan C. Twomey ◽  
Sierra N. Wolfenbarger
Keyword(s):  
United States ◽  
Powdery Mildew ◽  
Pacific Northwest ◽  
Western United States ◽  
R Genes ◽  
Sources Of Resistance ◽  
Department Of Agriculture ◽  
Breeding Programs ◽  
The Pacific ◽  
The U.S

Powdery mildew (caused by Podosphaera macularis) is one of the most important diseases of hop in the western United States. Strains of the fungus virulent on cultivars possessing the resistance factor termed R6 and the cultivar Cascade have become widespread in the Pacific Northwestern United States, the primary hop producing region in the country, rendering most cultivars grown susceptible to the disease at some level. In an effort to identify potential sources of resistance in extant germplasm, 136 male accessions of hop contained in the U.S. Department of Agriculture collection were screened under controlled conditions. Iterative inoculations with three isolates of P. macularis with varying race identified 23 (16.9%) accessions with apparent resistance to all known races of the pathogen present in the Pacific Northwest. Of the 23 accessions, 12 were resistant when inoculated with three additional isolates obtained from Europe that possess novel virulences. The nature of resistance in these individuals is unclear but does not appear to be based on known R genes. Identification of possible novel sources of resistance to powdery mildew will be useful to hop breeding programs in the western United States and elsewhere.

scholarly journals Seasonal Precipitation Influences Streamflow Vulnerability to the 2015 Drought in the Western United States

2019 ◽  
Vol 20 (7) ◽  
pp. 1261-1274
Author(s):  
Christopher P. Konrad
Keyword(s):  
United States ◽  
Pacific Northwest ◽  
Summer Precipitation ◽  
Western United States ◽  
Order Model ◽  
First Order ◽  
The Pacific ◽  
Critical Issues ◽  
Desert Southwest ◽  
Normative Models

Abstract Streamflow was exceptionally low in the spring and summer of 2015 across much of the western United States because of a regional drought that exploited the sensitivity of both snow- and rain-dominant rivers. Streamflow during 2015 was examined at 324 gauges in the region to assess its response to the amount, form, and seasonal timing of precipitation and the viability of using spatially aggregated, normative models to assess streamflow vulnerability to drought. Seasonal rain and spring snowmelt had the strongest effects on runoff during the same season, but their effects persisted into subsequent seasons as well. Below-normal runoff in the spring of 2015 was pervasive across the region, while distinct seasonal responses were evident in different hydroclimatic settings: January–March (winter) runoff was above normal in most snow-dominant rivers and runoff in all seasons was above normal for much of the desert Southwest. Summer precipitation contributed to summer runoff in both the Pacific Northwest and desert Southwest. A first-order model that presumes runoff is a constant fraction of precipitation (the precipitation elasticity of runoff, E = 1) could be used for assessing and forecasting runoff responses to precipitation deficits across the region, but runoff generally is more vulnerable to drought (E > 1) than predicted by a first-order model. Uncertainty in spring and summer precipitation forecasts remain critical issues for forecasting and predicting summer streamflow vulnerability to drought across much of the western United States.

scholarly journals Predictive Contributions of Snowmelt and Rainfall to Streamflow Variations in the Western United States

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Xiaohui Zheng ◽  
Qiguang Wang ◽  
Lihua Zhou ◽  
Qing Sun ◽  
Qi Li
Keyword(s):  
United States ◽  
Pacific Northwest ◽  
Climate Models ◽  
Coastal Areas ◽  
Snow Accumulation ◽  
Western United States ◽  
Lead Times ◽  
Wet Season ◽  
Mountain Areas ◽  
Southeastern Pacific

This study used long-term in situ rainfall, snow, and streamflow data to explore the predictive contributions of snowmelt and rainfall to streamflow in six watersheds over the Western United States. Analysis showed that peak snow accumulation, snow-free day, and snowmelt slope all had strong correlation with peak streamflow, particularly in inland basins. Further analysis revealed that the variation of snow accumulation anomaly had strong lead correlation with the variation of streamflow anomaly. Over the entire Western United States, inner mountain areas had lead times of 4–10 pentads. However, in coastal areas, nearly all sites had lead times of less than one pentad. The relative contributions of rainfall and snowmelt to streamflow in different watersheds were calculated based on the snow lead time. The geographic distribution of annual relative contributions revealed that interior areas were dominated by snowmelt contribution, whereas the rainfall contribution dominated coastal areas. In the wet season, the snowmelt contribution increased in the western Pacific Northwest, whereas the rainfall contribution increased in the southeastern Pacific Northwest, southern Upper Colorado, and northern Rio Grande regions. The derived results demonstrated the predictive contributions of snowmelt and rainfall to streamflow. These findings could be considered a reference both for seasonal predictions of streamflow and for prevention of hydrological disasters. Furthermore, they will be helpful in the evaluation and improvement of hydrological and climate models.

scholarly journals Uncertainty in surface-fire history: the case of ponderosa pine forests in the western United States

2001 ◽  
Vol 31 (7) ◽  
pp. 1205-1226 ◽  
Author(s):  
William L Baker ◽  
Donna Ehle
Keyword(s):  
United States ◽  
Forest Structure ◽  
Ponderosa Pine ◽  
Fire History ◽  
Pine Forests ◽  
Western United States ◽  
Surface Fire ◽  
Population Mean ◽  
Ponderosa Pine Forests ◽  
Fire Scar

Present understanding of fire ecology in forests subject to surface fires is based on fire-scar evidence. We present theory and empirical results that suggest that fire-history data have uncertainties and biases when used to estimate the population mean fire interval (FI) or other parameters of the fire regime. First, the population mean FI is difficult to estimate precisely because of unrecorded fires and can only be shown to lie in a broad range. Second, the interval between tree origin and first fire scar estimates a real fire-free interval that warrants inclusion in mean-FI calculations. Finally, inadequate sampling and targeting of multiple-scarred trees and high scar densities bias mean FIs toward shorter intervals. In ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) forests of the western United States, these uncertainties and biases suggest that reported mean FIs of 2-25 years significantly underestimate population mean FIs, which instead may be between 22 and 308 years. We suggest that uncertainty be explicitly stated in fire-history results by bracketing the range of possible population mean FIs. Research and improved methods may narrow the range, but there is no statistical or other method that can eliminate all uncertainty. Longer mean FIs in ponderosa pine forests suggest that (i) surface fire is still important, but less so in maintaining forest structure, and (ii) some dense patches of trees may have occurred in the pre-Euro-American landscape. Creation of low-density forest structure across all parts of ponderosa pine landscapes, particularly in valuable parks and reserves, is not supported by these results.

Seasonal Cycle Shifts in Hydroclimatology over the Western United States

2005 ◽  
Vol 18 (2) ◽  
pp. 372-384 ◽  
Author(s):  
Satish Kumar Regonda ◽  
Balaji Rajagopalan ◽  
Martyn Clark ◽  
John Pitlick
Keyword(s):  
United States ◽  
Pacific Northwest ◽  
Snow Water Equivalent ◽  
Warming Trend ◽  
Winter Precipitation ◽  
Western United States ◽  
Temperature And Precipitation ◽  
The Pacific ◽  
Snow Water ◽  
Northwest Region

Abstract Analyses of streamflow, snow mass temperature, and precipitation in snowmelt-dominated river basins in the western United States indicate an advance in the timing of peak spring season flows over the past 50 years. Warm temperature spells in spring have occurred much earlier in recent years, which explains in part the trend in the timing of the spring peak flow. In addition, a decrease in snow water equivalent and a general increase in winter precipitation are evident for many stations in the western United States. It appears that in recent decades more of the precipitation is coming as rain rather than snow. The trends are strongest at lower elevations and in the Pacific Northwest region, where winter temperatures are closer to the melting point; it appears that in this region in particular, modest shifts in temperature are capable of forcing large shifts in basin hydrologic response. It is speculated that these trends could be potentially a manifestation of the general global warming trend in recent decades and also due to enhanced ENSO activity. The observed trends in hydroclimatology over the western United States can have significant impacts on water resources planning and management.

First Report of Powdery Mildew of Magnolia Caused by Microsphaera magnifica (Erysiphe magnifica) in the Pacific Northwest

2003 ◽  
Vol 4 (1) ◽  
pp. 37
Author(s):  
Dean A. Glawe
Keyword(s):  
United States ◽  
North America ◽  
Powdery Mildew ◽  
Pacific Northwest ◽  
Western United States ◽  
First Report ◽  
Landscape Plant ◽  
First Finding ◽  
The Pacific ◽  
First Time

Magnolia liliiflora Desrousseaux in Lamarck (orthographic variant: M. liliiflora), a species thought to have originated in China (3), is used as a landscape plant in North America. In August 2002, Microsphaera magnifica U. Braun was collected from three plants of M. liliiflora in the Magnolia collection at the Washington Park Arboretum, University of Washington, Seattle. This report documents for the first time a powdery mildew disease of a Magnolia species in the Pacific Northwest, and the first finding of M. magnifica in the western United States. Accepted for publication 14 April 2003. Published 12 May 2003.

Holocene fire history of the southern Lake Baikal region

2021 ◽  
Author(s):  
Marianne Vogel ◽  
Chéïma Barhoumi ◽  
Hanane Limani ◽  
Sébastien Joannin ◽  
Odile Peyron ◽  
...  
Keyword(s):  
Lake Baikal ◽  
Baikal Region ◽  
Fire History ◽  
Fire Frequency ◽  
Human Populations ◽  
Pinus Sibirica ◽  
The Holocene ◽  
The Past ◽  
Lake Baikal Region ◽  
History Of

<p><strong>Holocene fire history of the southern Lake Baikal region</strong></p><p>The catastrophic fire years that have taken place during the last decade in Siberia and in the boreal forests in general, directly linked to global warming, have had dramatic repercussions on the human populations of these regions. Past fire reconstruction studies are currently the only way to study the past dynamics of these fires and to understand their link with climate, vegetation and human activities. However, few studies of the dynamics of these fires are available in Siberia, and none have been carried out on the scale of the Holocene. This study aims to present the first reconstruction of the fire history during the Holocene based on sedimentary charcoals from two lakes localised on the southern shore of Lake Baikal, in Siberia. Two lakes have been sampled, Lake Ébène and Lake Jarod. The results showed a similar trend between the two lakes,with severe and intense crown fires during the early Holocene and less severe surface fires after 6 500 cal. yr BP. According to pollen reconstructions carried out near the studied lakes, a vegetation transition occurred at the same time. Picea obovata was dominant during the early humid Holocene. After 6 500 cal. yr BP, conditions were drier and Pinus sylvestris and Pinus sibirica became the dominant species. Over the past 1 500 years, the greater presence of human populations has firstly resulted in an increase of the fire frequency, then probably in its maintenance after 600 cal. yr BP in lake Ébène and to finish, in its suppression after 900 cal. yr BP in Lake Jarod. The decrease of fire frequency at the end of the 20th century could be explained by new fire management policies.</p>

Interannual Variability of the Cyclonic Activity along the U.S. Pacific Coast: Influences on the Characteristics of Winter Precipitation in the Western United States

2009 ◽  
Vol 22 (21) ◽  
pp. 5732-5747 ◽  
Author(s):  
Boksoon Myoung ◽  
Yi Deng
Keyword(s):  
United States ◽  
Interannual Variability ◽  
Pacific Northwest ◽  
Pacific Coast ◽  
Storm Track ◽  
Winter Precipitation ◽  
Western United States ◽  
Cyclonic Activity ◽  
The Pacific ◽  
The U.S

Abstract This study examines the observed interannual variability of the cyclonic activity along the U.S. Pacific coast and quantifies its impact on the characteristics of both the winter total and extreme precipitation in the western United States. A cyclonic activity function (CAF) was derived from a dataset of objectively identified cyclone tracks in 27 winters (1979/80–2005/06). The leading empirical orthogonal function (EOF1) of the CAF was found to be responsible for the EOF1 of the winter precipitation in the western United States, which is a monopole mode centered over the Pacific Northwest and northern California. On the other hand, the EOF2 of the CAF contributes to the EOF2 of the winter precipitation, which indicates that above-normal precipitation in the Pacific Northwest and its immediate inland regions tends to be accompanied by below-normal precipitation in California and the southwestern United States and vice versa. The first two EOFs of CAF (precipitation) account for about 70% (78%) of the total interannual variance of CAF (precipitation). The second EOF modes of both the CAF and precipitation are significantly linked to the ENSO signal on interannual time scales. A composite analysis further reveals that the leading CAF modes increase (decrease) the winter total precipitation by increasing (decreasing) both the number of rainy days per winter and the extremeness of precipitation. The latter was quantified in terms of the 95th percentile of the daily rain rate and the probability of precipitation being heavy given a rainy day. The implications of the leading CAF modes for the water resources and the occurrence of extreme hydrologic events in the western United States, as well as their dynamical linkages to the Pacific storm track and various atmospheric low-frequency modes (i.e., teleconnection patterns), are also discussed.

Three Recent Flavors of Drought in the Pacific Northwest

2010 ◽  
Vol 49 (9) ◽  
pp. 2058-2068 ◽  
Author(s):  
Karin A. Bumbaco ◽  
Philip W. Mote
Keyword(s):  
United States ◽  
Pacific Northwest ◽  
Summer Precipitation ◽  
Winter Precipitation ◽  
Western United States ◽  
Hydropower Generation ◽  
The Past ◽  
The Pacific ◽  
Hydrologic Impacts ◽  
Precipitation Events

Abstract In common with much of the western United States, the Pacific Northwest (defined in this paper as Washington and Oregon) has experienced an unusual number of droughts in the past decade. This paper describes three of these droughts in terms of the precipitation, temperature, and soil moisture anomalies, and discusses different drought impacts experienced in the Pacific Northwest (PNW). For the first drought, in 2001, low winter precipitation in the PNW produced very low streamflow that primarily affected farmers and hydropower generation. For the second, in 2003, low summer precipitation in Washington (WA), and low summer precipitation and a warm winter in Oregon (OR) primarily affected streamflow and forests. For the last, in 2005, a lack of snowpack due to warm temperatures during significant winter precipitation events in WA, and low winter precipitation in OR, had a variety of different agricultural and hydrologic impacts. Although the proximal causes of droughts are easily quantified, the ultimate causes are not as clear. Better precipitation observations in the PNW are required to provide timely monitoring of conditions leading to droughts to improve prediction in the future.

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