scholarly journals Stable isotopic evidence of El Niño-like atmospheric circulation in the Pliocene Western United States

2012 ◽  
Vol 8 (5) ◽  
pp. 5083-5108 ◽  
Author(s):  
M. J. Winnick ◽  
J. M. Welker ◽  
C. P. Chamberlain
Keyword(s):  
United States ◽  
North America ◽  
El Niño ◽  
El Nino ◽  
Storm Track ◽  
Western United States ◽  
Western North America ◽  
Late Pliocene ◽  
Future Warming ◽  
Isotopic Anomalies

Abstract. Understanding how the hydrologic cycle has responded to warmer global temperatures in the past is especially important today as concentrations of CO2 in the atmosphere continue to increase due to human activities. The Pliocene offers an ideal window into a climate system that has equilibrated with current atmospheric pCO2. During the Pliocene the Western United States was wetter than modern, an observation at odds with our current understanding of future warming scenarios, which involve the expansion and poleward migration of the subtropical dry zone. Here we compare Pliocene oxygen isotope profiles of pedogenic carbonates across the Western US to modern isotopic anomalies in precipitation between phases of the El Niño Southern Oscillation (ENSO). We find that when accounting for seasonality of carbonate formation, isotopic changes through the late Pliocene match modern precipitation isotopic anomalies in El Niño years. Furthermore, isotopic shifts through the late Pliocene mirror changes through the early Pleistocene, which likely represents the southward migration of the westerly storm track caused by growth of the Laurentide Ice Sheet. We propose that the westerly storm track migrated northward through the late Pliocene with the development of the modern Cold Tongue in the East Equatorial Pacific, then returned southward with widespread glaciation in the Northern Hemisphere – a scenario supported by terrestrial climate proxies across the US. Together these data support the proposed existence of background El Niño-like conditions in Western North America during the warm Pliocene. If the Earth behaves similarly with future warming, this observation has important implications with regard to the amount and distribution of precipitation in Western North America.

scholarly journals Stable isotopic evidence of El Niño-like atmospheric circulation in the Pliocene western United States

2013 ◽  
Vol 9 (2) ◽  
pp. 903-912 ◽  
Author(s):  
M. J. Winnick ◽  
J. M. Welker ◽  
C. P. Chamberlain
Keyword(s):  
United States ◽  
North America ◽  
El Niño ◽  
El Nino ◽  
Storm Track ◽  
Western United States ◽  
Western North America ◽  
Late Pliocene ◽  
Future Warming ◽  
Isotopic Anomalies

Abstract. Understanding how the hydrologic cycle has responded to warmer global temperatures in the past is especially important today as concentrations of CO2 in the atmosphere continue to increase due to human activities. The Pliocene offers an ideal window into a climate system that has equilibrated with current atmospheric pCO2. During the Pliocene the western United States was wetter than modern, an observation at odds with our current understanding of future warming scenarios, which involve the expansion and poleward migration of the subtropical dry zone. Here we compare Pliocene oxygen isotope profiles of pedogenic carbonates across the western US to modern isotopic anomalies in precipitation between phases of the El Niño–Southern Oscillation (ENSO). We find that when accounting for seasonality of carbonate formation, isotopic changes through the late Pliocene match modern precipitation isotopic anomalies in El Niño years. Furthermore, isotopic shifts through the late Pliocene mirror changes through the early Pleistocene, which likely represents the southward migration of the westerly storm track caused by growth of the Laurentide ice sheet. We propose that the westerly storm track migrated northward through the late Pliocene with the development of the modern cold tongue in the east equatorial Pacific, then returned southward with widespread glaciation in the Northern Hemisphere – a scenario supported by terrestrial climate proxies across the US. Together these data support the proposed existence of background El Niño-like conditions in western North America during the warm Pliocene. If the earth behaves similarly with future warming, this observation has important implications with regard to the amount and distribution of precipitation in western North America.

scholarly journals The Climatology of Synoptic-Scale Ascent over Western North America: A Perspective on Storm Tracks

2012 ◽  
Vol 140 (6) ◽  
pp. 1761-1778 ◽  
Author(s):  
Neil P. Lareau ◽  
John D. Horel
Keyword(s):  
United States ◽  
North America ◽  
Storm Track ◽  
Western United States ◽  
Storm Tracks ◽  
Western North America ◽  
Synoptic Scale ◽  
Regional Patterns ◽  
Mean Values ◽  
The Mean

Abstract The position and variability of storm tracks across western North America are examined during the October–April cool seasons spanning 1989–2010. The location and intensity of storms are represented by strong synoptic-scale ascent, which is diagnosed by the alternative balance omega equation applied to ECMWF Re-Analysis Interim data. This dynamically filtered method removes poorly resolved updrafts arising from subsynoptic-scale phenomena such as convection and mountain waves. The resulting vertical motions are illustrated for the case of a strong storm traversing the western United States. Summary statistics of synoptic-scale ascent are compiled over months, seasons, and the entire 21-yr period. Locations exhibiting high mean values of ascent are deemed to represent storm tracks. The climatological-mean storm track exhibits a sinusoidal shape across the eastern Pacific and western North America. The composite evolution of strong storms moving along specific segments of the storm track show regional differences (e.g., storms poleward of 50°N tend to result from progressive low-amplitude troughs progressing through the mean planetary ridge, while storms over the western United States are initiated by digging troughs that temporarily suppress the mean ridge). Seasonal shifts in the storm track are pronounced and exhibit coherent regional patterns. Interannual variations in synoptic-scale ascent indicate meridional shifts in position as well as changes in the degree of amplification within the dominant sinusoidal storm track. These changes in structure are related to the phase of ENSO: El Niño (La Niña) winters favor zonal (amplified) and southern (northern) storm tracks.

scholarly journals AN ASSESSMENT OF LATE PLEISTOCENE TO MIDDLE HOLOCENE LAKE LEVEL FLUCTUATIONS IN SURPRISE VALLEY, CALIFORNIA

2018 ◽  
Author(s):  
Daniel Enrique Ibarra
Keyword(s):  
United States ◽  
North America ◽  
Late Pleistocene ◽  
General Circulation ◽  
Lake Level ◽  
Basin And Range ◽  
Future Climate ◽  
Western United States ◽  
Western North America ◽  
Ocean General Circulation

Knowledge of Earth’s climate history and sensitivity, combined with modeling past and future climate, are central to informing policy decisions regarding future climate change. The hydrologic response to future warming scenarios due to increased anthropogenic CO2 emissions remains uncertain. Freshwater availability in the arid western United States is projected to decrease in availability as increased agricultural, urban and industrial uses continue to stress supplies. Motivated by the potential for dramatic future hydrologic changes, studies recording the abrupt transitions between different equilibrium states of natural past climate variability shed light on our understanding of the modern climate system.The presence of pluvial lakes in the Basin and Range Province, in the western United States, during the late Pleistocene (40 to 10 ka) indicates far greater moisture availability during the Pleistocene glacials. This study investigates the timing and magnitude of the most recent pluvial lake cycle that filled Surprise Valley, California using geophysical, geochemical and geochronologic tools. Spanning 31.2 to 4.6 ka, this new lake level record places the highest lake level, at 180 meters above present day playa, at 13.9 ± 1.2 ka. This age appears to be nearly synchronous with highstands of Lake Lahontan to the south and the Chewaucan Basin to the north. Additionally, most of the Basin and Range lake highstands, including Lake Surprise, follow peaks in precipitation minus evapotranspiration (P-ET) by 8-10 kyr. By compiling a diverse set of paleoclimate data available for western North America, I found that the timing and geographic distribution of lake highstands is inconsistent with increased precipitation in response to shifting westerly winds, the current model for the genesis of large lakes in western North America. Rather, lakes levels are more strongly correlated with changes in summer insolation, suggesting that lake highstands were likely facilitated by colder temperatures and increased humidity due to the presence of continental ice sheets and increased atmospheric convergence. I compared the constraints from lake and soil-based records to Atmosphere-Ocean General Circulation Model simulations from the Paleoclimate Model Intercomparison Project 2. Based on model-proxy intercomparison, the Atmosphere-Ocean General Circulation Models, the same models used to also assess future climatic changes, poorly predict hydrologic quantities for the Last Glacial Maximum.

scholarly journals The impact of bark beetle infestation on monoterpene emissions and secondary organic aerosol formation in Western North America

2012 ◽  
Vol 12 (11) ◽  
pp. 29763-29800 ◽  
Author(s):  
A. R. Berg ◽  
C. L. Heald ◽  
K. E. Huff Hartz ◽  
A. G. Hallar ◽  
A. J. H. Meddens ◽  
...  
Keyword(s):  
United States ◽  
British Columbia ◽  
North America ◽  
Bark Beetle ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Western United States ◽  
Mortality Data ◽  
Western North America ◽  
The Impact

Abstract. Over the last decade, extensive beetle outbreaks in Western North America have destroyed over 100 000 km2 of forest throughout British Columbia and the Western United States. Beetle infestations impact monoterpene emissions through both decreased emissions as trees are killed (mortality effect) and increased emissions in trees under attack (attack effect). We use 14 yr of beetle mortality data together with beetle-induced monoterpene concentration data in the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM) to investigate the impact of beetle mortality and attack on monoterpene emissions and secondary organic aerosol (SOA) formation in Western North America. Regionally, beetle infestations may have a significant impact on monoterpene emissions and SOA concentrations, with up to a 4-fold increase in monoterpene emissions and up to a 40% increase in SOA concentrations in some years (following a scenario where the attack effect is based on observed lodgepole pine response). Responses to beetle attack depend on the extent of previous mortality and the number of trees under attack in a given year, which can vary greatly over space and time. Simulated enhancements peak in 2004 (British Columbia) and 2008 (US). Responses to beetle attack are shown to be substantially larger (up to a 3-fold localized increase in SOA concentrations) when following a scenario based on bark-beetle attack in spruce trees. Placed in the context of observations from the IMPROVE network, the changes in SOA concentrations due to beetle attack are in most cases small compared to the large annual and interannual variability in total organic aerosol which is driven by wildfire activity in Western North America. This indicates that most beetle-induced SOA changes are not likely detectable in current observation networks; however these changes may impede efforts to achieve natural visibility conditions in the national parks and wilderness areas of the Western United States.

Using High-Resolution Reanalysis Data to Explore Localized Western North America Hydroclimate Relationships with ENSO

2017 ◽  
Vol 30 (14) ◽  
pp. 5395-5417 ◽  
Author(s):  
Joshua P. Heyer ◽  
Simon C. Brewer ◽  
Jacqueline J. Shinker
Keyword(s):  
High Resolution ◽  
North America ◽  
El Niño ◽  
El Nino ◽  
Reanalysis Data ◽  
Tropical Pacific ◽  
Series Data ◽  
Western North America ◽  
Surface Precipitation ◽  
Sst Variability

Many studies have used observational data to explore associations between El Niño–Southern Oscillation (ENSO) and western North America (NA) hydroclimate at regional spatial scales. However, relationships between tropical Pacific sea surface temperature (SST) variability and western NA hydroclimate at local scales using reanalysis data are less understood. Here, the current understanding of relationships between large-scale tropical Pacific SST variability and western NA hydroclimate is extended to localized headwaters. To accomplish this, high-resolution reanalysis data (i.e., monthly mean surface precipitation rate, 2-m temperature, 850-mb specific humidity, and 500-mb omega) were used for gridpoint correlation analyses with Niño-3.4 SST and El Niño Modoki indices. Reanalysis time series data were provided by the National Centers for Environmental Prediction North American Regional Reanalysis (NARR) product. To validate the accuracy of NARR surface data, observational Livneh precipitation and temperature data were used. Resulting correlations between tropical Pacific indices and NARR surface precipitation and 2-m temperature are consistent with previous research both spatially and temporally, indicating that the strongest correlations occur primarily over southwestern NA during the winter (DJF). The results herein demonstrate the potential of high-resolution reanalysis data to reveal distinct correlations over topographically complex watersheds in the U.S. Intermountain West (IMW) over the recent record, 1979–2015. The use of the high-resolution NARR product as a viable option to explore western NA hydroclimate is demonstrated here.

Contributions of Downstream Eddy Development to the Teleconnection between ENSO and the Atmospheric Circulation over the North Atlantic

2012 ◽  
Vol 25 (14) ◽  
pp. 4993-5010 ◽  
Author(s):  
Ying Li ◽  
Ngar-Cheung Lau
Keyword(s):  
North America ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
El Niño ◽  
North Pacific ◽  
El Nino ◽  
Storm Track ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific

Abstract The spatiotemporal evolution of various meteorological phenomena associated with El Niño–Southern Oscillation (ENSO) in the North Pacific–North American–North Atlantic sector is examined using both NCEP–NCAR reanalyses and output from a 2000-yr integration of a global coupled climate model. Particular attention is devoted to the implications of downstream eddy developments on the relationship between ENSO and the atmospheric circulation over the North Atlantic. The El Niño–related persistent events are characterized by a strengthened Pacific subtropical jet stream and an equatorward-shifted storm track over the North Pacific. The wave packets that populate the storm tracks travel eastward through downstream development. The barotropic forcing of the embedded synoptic-scale eddies is conducive to the formation of a flow that resembles the negative phase of the North Atlantic Oscillation (NAO). The more frequent and higher persistence of those episodes during El Niño winters contribute to the prevalence of negative NAO conditions. The above processes are further delineated by conducting a case study for the 2009/10 winter season, in which both El Niño and negative NAO conditions prevailed. It is illustrated that the frequent and intense surface cyclone development over North America and the western Atlantic throughout that winter are associated with upper-level troughs propagating across North America, which in turn are linked to downstream evolution of wave packets originating from the Pacific storm track.

scholarly journals The Effect of El Niño on Flood Damages in the Western United States

2019 ◽  
Vol 11 (3) ◽  
pp. 489-504 ◽  
Author(s):  
Thomas W. Corringham ◽  
Daniel R. Cayan
Keyword(s):  
United States ◽  
Extreme Events ◽  
El Niño ◽  
Southern California ◽  
El Nino ◽  
Southern Oscillation ◽  
Western United States ◽  
Opposite Pattern ◽  
Flood Damages ◽  
Insured Losses

Abstract This paper quantifies insured flood losses across the western United States from 1978 to 2017, presenting a spatiotemporal analysis of National Flood Insurance Program (NFIP) daily claims and losses over this period. While considerably lower (only 3.3%) than broader measures of direct damages measured by a National Weather Service (NWS) dataset, NFIP insured losses are highly correlated to the annual damages in the NWS dataset, and the NFIP data provide flood impacts at a fine degree of spatial resolution. The NFIP data reveal that 1% of extreme events, covering wide spatial areas, caused over 66% of total insured losses. Connections between extreme events and El Niño–Southern Oscillation (ENSO) that have been documented in past research are borne out in the insurance data. In coastal Southern California and across the Southwest, El Niño conditions have had a strong effect in producing more frequent and higher magnitudes of insured losses, while La Niña conditions significantly reduce both the frequency and magnitude of losses. In the Pacific Northwest, the opposite pattern appears, although the effect is weaker and less spatially coherent. The persistent evolution of ENSO offers the possibility for property owners, policy makers, and emergency planners and responders that unusually high or low flood damages could be predicted in advance of the primary winter storm period along the West Coast. Within the 40-yr NFIP history, it is found that the multivariate ENSO index would have provided an 8-month look-ahead for heightened damages in Southern California.

scholarly journals The impact of bark beetle infestations on monoterpene emissions and secondary organic aerosol formation in western North America

2013 ◽  
Vol 13 (6) ◽  
pp. 3149-3161 ◽  
Author(s):  
A. R. Berg ◽  
C. L. Heald ◽  
K. E. Huff Hartz ◽  
A. G. Hallar ◽  
A. J. H. Meddens ◽  
...  
Keyword(s):  
United States ◽  
British Columbia ◽  
North America ◽  
Bark Beetle ◽  
Tree Mortality ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Western United States ◽  
Western North America ◽  
The Impact

Abstract. Over the last decade, extensive beetle outbreaks in western North America have destroyed over 100 000 km2 of forest throughout British Columbia and the western United States. Beetle infestations impact monoterpene emissions through both decreased emissions as trees are killed (mortality effect) and increased emissions in trees under attack (attack effect). We use 14 yr of beetle-induced tree mortality data together with beetle-induced monoterpene emission data in the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM) to investigate the impact of beetle-induced tree mortality and attack on monoterpene emissions and secondary organic aerosol (SOA) formation in western North America. Regionally, beetle infestations may have a significant impact on monoterpene emissions and SOA concentrations, with up to a 4-fold increase in monoterpene emissions and up to a 40% increase in SOA concentrations in some years (in a scenario where the attack effect is based on observed lodgepole pine response). Responses to beetle attack depend on the extent of previous mortality and the number of trees under attack in a given year, which can vary greatly over space and time. Simulated enhancements peak in 2004 (British Columbia) and 2008 (US). Responses to beetle attack are shown to be substantially larger (up to a 3-fold localized increase in summertime SOA concentrations) in a scenario based on bark-beetle attack in spruce trees. Placed in the context of observations from the IMPROVE network, the changes in SOA concentrations due to beetle attack are in most cases small compared to the large annual and interannual variability in total organic aerosol which is driven by wildfire activity in western North America. This indicates that most beetle-induced SOA changes are not likely detectable in current observation networks; however, these changes may impede efforts to achieve natural visibility conditions in the national parks and wilderness areas of the western United States.

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