scholarly journals Pacific North American circulation pattern links external forcing and North American hydroclimatic change over the past millennium

2017 ◽  
Vol 114 (13) ◽  
pp. 3340-3345 ◽  
Author(s):  
Zhongfang Liu ◽  
Yanlin Tang ◽  
Zhimin Jian ◽  
Christopher J. Poulsen ◽  
Jeffrey M. Welker ◽  
...  
Keyword(s):  
North America ◽  
North American ◽  
Circulation Pattern ◽  
Sea Surface ◽  
Pacific North American ◽  
The Past ◽  
Decadal Scale ◽  
Instrumental Record ◽  
Hydroclimatic Change ◽  
Past Millennium

Land and sea surface temperatures, precipitation, and storm tracks in North America and the North Pacific are controlled to a large degree by atmospheric variability associated with the Pacific North American (PNA) pattern. The modern instrumental record indicates a trend toward a positive PNA phase in recent decades, which has led to accelerated warming and snowpack decline in northwestern North America. The brevity of the instrumental record, however, limits our understanding of long-term PNA variability and its directional or cyclic patterns. Here we develop a 937-y-long reconstruction of the winter PNA based on a network of annually resolved tree-ring proxy records across North America. The reconstruction is consistent with previous regional records in suggesting that the recent persistent positive PNA pattern is unprecedented over the past millennium, but documents patterns of decadal-scale variability that contrast with previous reconstructions. Our reconstruction shows that PNA has been strongly and consistently correlated with sea surface temperature variation, solar irradiance, and volcanic forcing over the period of record, and played a significant role in translating these forcings into decadal-to-multidecadal hydroclimate variability over North America. Climate model ensembles show limited power to predict multidecadal variation in PNA over the period of our record, raising questions about their potential to project future hydroclimatic change modulated by this circulation pattern.

scholarly journals Indigenous impacts on North American Great Plains fire regimes of the past millennium

2018 ◽  
Vol 115 (32) ◽  
pp. 8143-8148 ◽  
Author(s):  
Christopher I. Roos ◽  
María Nieves Zedeño ◽  
Kacy L. Hollenback ◽  
Mary M. H. Erlick
Keyword(s):  
North American ◽  
Human Impacts ◽  
Fire Regimes ◽  
Human Populations ◽  
The Past ◽  
Fire Use ◽  
Decadal Scale ◽  
Fire Activity ◽  
Prairie Fire ◽  
Past Millennium

Fire use has played an important role in human evolution and subsequent dispersals across the globe, yet the relative importance of human activity and climate on fire regimes is controversial. This is particularly true for historical fire regimes of the Americas, where indigenous groups used fire for myriad reasons but paleofire records indicate strong climate–fire relationships. In North American grasslands, decadal-scale wet periods facilitated widespread fire activity because of the abundance of fuel promoted by pluvial episodes. In these settings, human impacts on fire regimes are assumed to be independent of climate, thereby diminishing the strength of climate–fire relationships. We used an offsite geoarchaeological approach to link terrestrial records of prairie fire activity with spatially related archaeological features (driveline complexes) used for intensive, communal bison hunting in north-central Montana. Radiocarbon-dated charcoal layers from alluvial and colluvial deposits associated with driveline complexes indicate that peak fire activity over the past millennium occurred coincident with the use of these features (ca. 1100–1650 CE). However, comparison of dated fire deposits with Palmer Drought Severity Index reconstructions reveal strong climate–fire linkages. More than half of all charcoal layers coincide with modest pluvial episodes, suggesting that fire use by indigenous hunters enhanced the effects of climate variability on prairie fire regimes. These results indicate that relatively small, mobile human populations can impact natural fire regimes, even in pyrogeographic settings in which climate exerts strong, top-down controls on fuels.

scholarly journals Supporting Restoration Decisions through Integration of Tree-Ring and Modeling Data: Reconstructing Flow and Salinity in the San Francisco Estuary over the Past Millennium

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2139
Author(s):  
Paul H. Hutton ◽  
David M. Meko ◽  
Sujoy B. Roy
Keyword(s):  
San Francisco ◽  
Tree Ring ◽  
San Francisco Estuary ◽  
Salinity Intrusion ◽  
Estuarine Ecosystem ◽  
Freshwater Flow ◽  
The Past ◽  
Decadal Scale ◽  
Tree Ring Data ◽  
Past Millennium

This work presents updated reconstructions of watershed runoff to San Francisco Estuary from tree-ring data to AD 903, coupled with models relating runoff to freshwater flow to the estuary and salinity intrusion. We characterize pre-development freshwater flow and salinity conditions in the estuary over the past millennium and compare this characterization with contemporary conditions to better understand the magnitude and seasonality of changes over this time. This work shows that the instrumented flow record spans the range of runoff patterns over the past millennium (averaged over 5, 10, 20 and 100 years), and thus serves as a reasonable basis for planning-level evaluations of historical hydrologic conditions in the estuary. Over annual timescales we show that, although median freshwater flow to the estuary has not changed significantly, it has been more variable over the past century compared to pre-development flow conditions. We further show that the contemporary period is generally associated with greater spring salinity intrusion and lesser summer–fall salinity intrusion relative to the pre-development period. Thus, salinity intrusion in summer and fall months was a common occurrence under pre-development conditions and has been moderated in the contemporary period due to the operations of upstream reservoirs, which were designed to hold winter and spring runoff for release in summer and fall. This work also confirms a dramatic decadal-scale hydrologic shift in the watershed from very wet to very dry conditions during the late 19th and early 20th centuries; while not unprecedented, these shifts have been seen only a few times in the past millennium. This shift resulted in an increase in salinity intrusion in the first three decades of the 20th century, as documented through early records. Population growth and extensive watershed modification during this period exacerbated this underlying hydrologic shift. Putting this shift in the context of other anthropogenic drivers is important in understanding the historical response of the estuary and in setting salinity targets for estuarine restoration. By characterizing the long-term behavior of San Francisco Estuary, this work supports decision-making in the State of California related to flow and salinity management for restoration of the estuarine ecosystem.

scholarly journals Contrastive Influence of ENSO and PNA on Variability and Predictability of North American Winter Precipitation

2019 ◽  
Vol 32 (19) ◽  
pp. 6271-6284 ◽  
Author(s):  
Xiaofan Li ◽  
Zeng-Zhen Hu ◽  
Ping Liang ◽  
Jieshun Zhu
Keyword(s):  
North America ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
North American ◽  
North Pacific ◽  
Winter Precipitation ◽  
Sea Surface ◽  
The North ◽  
Remote Forcing ◽  
The North Pacific

Abstract In this work, the roles of El Niño–Southern Oscillation (ENSO) in the variability and predictability of the Pacific–North American (PNA) pattern and precipitation in North America in winter are examined. It is noted that statistically about 29% of the variance of PNA is linearly linked to ENSO, while the remaining 71% of the variance of PNA might be explained by other processes, including atmospheric internal dynamics and sea surface temperature variations in the North Pacific. The ENSO impact is mainly meridional from the tropics to the mid–high latitudes, while a major fraction of the non-ENSO variability associated with PNA is confined in the zonal direction from the North Pacific to the North American continent. Such interferential connection on PNA as well as on North American climate variability may reflect a competition between local internal dynamical processes (unpredictable fraction) and remote forcing (predictable fraction). Model responses to observed sea surface temperature and model forecasts confirm that the remote forcing is mainly associated with ENSO and it is the major source of predictability of PNA and winter precipitation in North America.

scholarly journals A Magical Reorientation of the Modern: Professional Organizers and Thingly Care in Contemporary North America

2016 ◽  
Vol 31 (3) ◽  
pp. 438-457 ◽  
Author(s):  
Katie Kilroy-Marac
Keyword(s):  
North America ◽  
Mental Disorder ◽  
North American ◽  
Popular Media ◽  
Hoarding Disorder ◽  
The Past ◽  
The North ◽  
Dsm V ◽  
Double Movement ◽  
Domestic Variety

Within the past decade, material disorder—especially that of the domestic variety—has come to stand alternately as evidence, symptom, and potential cause of mental disorder in the North American popular and psychiatric imagination. Sources ranging from the newly defined Hoarding Disorder diagnosis in the DSM-V, to popular media, to agents of the burgeoning clutter-management industry describe disorder in terms of an irrational attachment, closeness, or overidentification with objects. At the same time, these sources imagine order to result from the cool distance and controlled passion a person is able to maintain toward his or her possessions. Drawing on more than twenty interviews and numerous fieldwork encounters with professional organizers (POs) in Toronto between 2014 and 2015, this article describes how POs aim to reorient their clients materially, morally, and affectively to relieve the disorder they report in their lives. Here, I argue, POs emerge as a species of late capitalist healer whose interventions are animated by a paradoxical double movement. For just as POs act to loosen the object attachments and disrupt the “secret sympathy” their clients share with their possessions, they operate within a realm of magical correspondence where matter and mind are imagined to reflect and affect one another, and where bringing order to a client’s possessions means also bringing order to his or her mind.

The Impact of Sea Surface Temperature Biases on North American Precipitation in a High-Resolution Climate Model

2020 ◽  
Vol 33 (6) ◽  
pp. 2427-2447 ◽  
Author(s):  
Nathaniel C. Johnson ◽  
Lakshmi Krishnamurthy ◽  
Andrew T. Wittenberg ◽  
Baoqiang Xiang ◽  
Gabriel A. Vecchi ◽  
...  
Keyword(s):  
North America ◽  
Surface Temperature ◽  
North Atlantic ◽  
North American ◽  
North Pacific ◽  
Climate Model ◽  
Sea Surface ◽  
Tropical Atlantic ◽  
Western North America ◽  
The North

AbstractPositive precipitation biases over western North America have remained a pervasive problem in the current generation of coupled global climate models. These biases are substantially reduced, however, in a version of the Geophysical Fluid Dynamics Laboratory Forecast-Oriented Low Ocean Resolution (FLOR) coupled climate model with systematic sea surface temperature (SST) biases artificially corrected through flux adjustment. This study examines how the SST biases in the Atlantic and Pacific Oceans contribute to the North American precipitation biases. Experiments with the FLOR model in which SST biases are removed in the Atlantic and Pacific are carried out to determine the contribution of SST errors in each basin to precipitation statistics over North America. Tropical and North Pacific SST biases have a strong impact on northern North American precipitation, while tropical Atlantic SST biases have a dominant impact on precipitation biases in southern North America, including the western United States. Most notably, negative SST biases in the tropical Atlantic in boreal winter induce an anomalously strong Aleutian low and a southward bias in the North Pacific storm track. In boreal summer, the negative SST biases induce a strengthened North Atlantic subtropical high and Great Plains low-level jet. Each of these impacts contributes to positive annual mean precipitation biases over western North America. Both North Pacific and North Atlantic SST biases induce SST biases in remote basins through dynamical pathways, so a complete attribution of the effects of SST biases on precipitation must account for both the local and remote impacts.

Is Your Power Plant Headed for a HILP? How to Avoid, Detect or Mitigate High Impact–Low Probability (HILP) Events

2008 ◽  
Author(s):  
Robert R. Richwine ◽  
G. Scott Stallard ◽  
G. Michael Curley
Keyword(s):  
Power Plant ◽  
North America ◽  
North American ◽  
Power Plants ◽  
High Impact ◽  
Root Cause ◽  
The Past ◽  
The North ◽  
Sufficient Detail ◽  
Low Probability

In recent years some power companies have instituted programs aimed at reducing or eliminating their power plants’ unreliability caused by abnormal events that occur infrequently but result in extended unplanned outages when they do occur, i.e. High Impact–Low Probability events (HILPs). HILPs include catastrophic events such as turbine water induction, boiler explosions, generator winding failures, etc. Many of these successful programs have relied on the detailed reliability data contained in the North American Electric Reliability Corporation’s (NERC) Generating Availability Data System (GADS) that contains data collected over the past 25 years from 5000+ generating units in North America. Using this data, these companies have been able to 1) benchmark their fleet’s unreliability due to HILPs against their North American peers, 2) prioritize their peer group’s susceptibility to various HILP modes and 3) use root cause data contained within the NERC-GADS data base to help identify and evaluate ways to proactively prevent, detect and/or mitigate the consequences of HILP events. This paper will describe the methods used in these successful programs in sufficient detail to enable others to adopt the techniques for application at their own generating plants.

scholarly journals Tropical cooling and the onset of North American glaciation

2007 ◽  
Vol 3 (3) ◽  
pp. 549-557 ◽  
Author(s):  
P. Huybers ◽  
P. Molnar
Keyword(s):  
North America ◽  
North American ◽  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Climate Data ◽  
Similar Estimate ◽  
Eastern Tropical Pacific ◽  
The Past ◽  
Eastern Equatorial Pacific

Abstract. We offer a test of the idea that gradual cooling in the eastern tropical Pacific led to cooling of North America and the initiation of glaciation ~3 Myr ago. Using modern climate data we estimate how warming of the eastern tropical Pacific affects North American temperature and ice-ablation. Assuming that the modern relationship holds over the past millions of years, a ~4°C warmer eastern tropical Pacific between 3–5 Ma would increase ablation in northern North America by approximately two meters per year. By comparison, a similar estimate of the ablation response to variations in Earth's obliquity gives less than half the magnitude of the tropically-induced change. Considering that variations in Earth's obliquity appear sufficient to initiate glaciations between ~1–3 Ma, we infer that the warmer eastern equatorial Pacific prior to 3 Ma suffices to preclude glaciation.

scholarly journals Supporting Restoration Decisions through Integration of Tree-Ring and Modeling Data: Reconstructing Flow and Salinity in the San Francisco Estuary over the Past Millennium

2021 ◽  
Author(s):  
Paul H Hutton ◽  
David M Meko ◽  
Sujoy B Roy
Keyword(s):  
San Francisco ◽  
Tree Ring ◽  
San Francisco Estuary ◽  
Salinity Intrusion ◽  
Estuarine Ecosystem ◽  
Freshwater Flow ◽  
The Past ◽  
Decadal Scale ◽  
Tree Ring Data ◽  
Past Millennium

This work presents updated reconstructions of watershed runoff to San Francisco Estuary from tree-ring data to AD 903, coupled with models relating runoff to freshwater flow to the estuary and salinity intrusion. We characterize pre-development freshwater flow and salinity conditions in the estuary over the past millennium and compare this characterization with contemporary conditions to better understand the magnitude and seasonality of changes over this time. This work shows that the instrumented flow record spans the range of runoff patterns over the past millennium (averaged over five, ten, twenty and one hundred years), and thus serves as a reasonable basis for planning-level evaluations of historical hydrologic conditions in the estuary. Over annual timescales we show that, although median freshwater flow to the estuary has not changed significantly, it has been more variable over the past century compared to pre-development flow conditions. We further show that the contemporary period is generally associated with greater spring salinity intrusion and lesser summer-fall salinity intrusion relative to the pre-development period. Thus, salinity intrusion in summer and fall months was a common occurrence under pre-development conditions and has been moderated in the contemporary period due to the operations of upstream reservoirs, which were designed to hold winter and spring runoff for release in summer and fall. This work also confirms a dramatic decadal-scale hydrologic shift in the watershed from very wet to very dry conditions during the late 19th and early 20th centuries; while not unprecedented, these shifts have been seen only a few times in the past millennium. This shift resulted in an increase in salinity intrusion in the first three decades of the 20th century, as documented through early records. Population growth and extensive watershed modification during this period exacerbated this underlying hydrologic shift. Putting this shift in the context of other anthropogenic drivers is important in understanding the historical response of the estuary and in setting salinity targets for estuarine restoration. By characterizing the long-term behavior of San Francisco Estuary, this work supports decision-making in the State of California related to flow and salinity management for restoration of the estuarine ecosystem.

scholarly journals Reconciling reconstructed and simulated features of the winter Pacific–North-American pattern in the early 19th century

2014 ◽  
Vol 10 (6) ◽  
pp. 4425-4468
Author(s):  
D. Zanchettin ◽  
O. Bothe ◽  
F. Lehner ◽  
P. Ortega ◽  
C. C. Raible ◽  
...  
Keyword(s):  
North America ◽  
19Th Century ◽  
North American ◽  
Climate Models ◽  
Reconstruction Process ◽  
Early 19Th Century ◽  
Climate Conditions ◽  
Pacific North American ◽  
Climate Simulations ◽  
Northwestern North America

Abstract. Reconstructions of past climate behavior often describe prominent anomalous periods that are not necessarily captured in climate simulations. Here, we illustrate the contrast between an interdecadal strong positive phase of the winter Pacific/North American pattern (PNA) in the early 19th century that is described by a PNA reconstruction based on tree-rings from northwestern North America, and a slight tendency towards negative winter PNA anomalies during the same period in an ensemble of state-of-the-art coupled climate simulations. Additionally, a pseudo-proxy investigation with the same simulation ensemble allows assessing the robustness of PNA reconstructions using solely geophysical predictors from northwestern North America for the last millennium. The reconstructed early-19th-century positive PNA anomaly emerges as a potentially reliable feature, although it is subject to a number of sources of uncertainty and potential deficiencies. The pseudo-reconstructions demonstrate that the early-19th-century discrepancy between reconstructed and simulated PNA does not stem from the reconstruction process. Instead, reconstructed and simulated features of the early-19th-century PNA can be reconciled by interpreting the reconstructed evolution during this time as an expression of internal climate variability, hence unlikely to be reproduced in its exact temporal occurrence by a small ensemble of climate simulations. However, firm attribution of the reconstructed PNA anomaly is hampered by known limitations and deficiencies of coupled climate models and uncertainties in the early-19th-century external forcing and background climate conditions.

Sign in / Sign up

Export Citation Format

Share Document