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1.
Sci Adv ; 5(12): eaax8203, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31844667

RESUMO

The Holocene thermal maximum was characterized by strong summer solar heating that substantially increased the summertime temperature relative to preindustrial climate. However, the summer warming was compensated by weaker winter insolation, and the annual mean temperature of the Holocene thermal maximum remains ambiguous. Using multimodel mid-Holocene simulations, we show that the annual mean Northern Hemisphere temperature is strongly correlated with the degree of Arctic amplification and sea ice loss. Additional model experiments show that the summer Arctic sea ice loss persists into winter and increases the mid- and high-latitude temperatures. These results are evaluated against four proxy datasets to verify that the annual mean northern high-latitude temperature during the mid-Holocene was warmer than the preindustrial climate, because of the seasonally rectified temperature increase driven by the Arctic amplification. This study offers a resolution to the "Holocene temperature conundrum", a well-known discrepancy between paleo-proxies and climate model simulations of Holocene thermal maximum.

2.
Nat Commun ; 9(1): 4571, 2018 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-30385755

RESUMO

Mid-Holocene climate was characterized by strong summer solar heating that decreased Arctic sea ice cover. Motivated by recent studies identifying Arctic sea ice loss as a key driver of future climate change, we separate the influences of Arctic sea ice loss on mid-Holocene climate. By performing idealized climate model perturbation experiments, we show that Arctic sea ice loss causes zonally asymmetric surface temperature responses especially in winter: sea ice loss warms North America and the North Pacific, which would otherwise be much colder due to weaker winter insolation. In contrast, over East Asia, sea ice loss slightly decreases the temperature in early winter. These temperature responses are associated with the weakening of mid-high latitude westerlies and polar stratospheric warming. Sea ice loss also weakens the Atlantic meridional overturning circulation, although this weakening signal diminishes after 150-200 years of model integration. These results suggest that mid-Holocene climate changes should be interpreted in terms of both Arctic sea ice cover and insolation forcing.

3.
Medicine (Baltimore) ; 97(36): e12133, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30200103

RESUMO

Few studies have been performed regarding the reduction of pain in the upper trapezius (UT) muscle by applying interventions to the sternocleidomastoid (SCM) muscle, which is innervated by the same nerves.The purpose of this study was to investigate the effects of soft tissue release intervention on the SCM and suboccipital muscles with regard to muscle hardness and pressure pain threshold (PPT) of the SCM and UT muscles in smartphone users with latent myofascial trigger points (MTrPs) in the UT muscle.Seventeen smartphone users (5 men and 12 women) with latent MTrPs in the UT muscle participated in the study. This study used a single blinding, cross-over design, wherein sternocleidomastoid soft tissue release (SSTR) and suboccipital release (SR) were applied on the subjects in random order one week apart. Muscle hardness and the PPT of the SCM and UT muscles were assessed before and after the intervention.After SSTR was applied, the SCM and UT muscles showed a significant decrease in muscle hardness and a significant increase in PPT. After SR was applied, the UT muscle showed a significant decrease in muscle hardness and a significant increase in PPT. When comparing the amount of change between the SSTR and SR interventions, significant differences were found for SCM muscle hardness and PPT of the UT muscle in the SSTR intervention, compared with the SR intervention.Therefore, we suggest that, to reduce pain in the UT muscle, it may be useful to apply intervention directly to the UT muscle, as well as to the SCM muscle, which is innervated by the same nerve.


Assuntos
Síndromes da Dor Miofascial/fisiopatologia , Síndromes da Dor Miofascial/terapia , Smartphone , Terapia de Tecidos Moles , Pontos-Gatilho , Adulto , Estudos Cross-Over , Feminino , Humanos , Masculino , Síndromes da Dor Miofascial/etiologia , Músculos do Pescoço/fisiopatologia , Limiar da Dor , Pressão , Método Simples-Cego , Resultado do Tratamento , Adulto Jovem
4.
Sci Rep ; 8(1): 5504, 2018 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-29615824

RESUMO

In addition to weather conditions and pollutant emissions, the degree to which topography influences the occurrence and development of haze pollution in downtown Beijing and the mechanisms that may be involved remain open questions. A series of atmospheric chemistry simulations are executed by using the online-coupled Weather Research and Forecasting with Chemistry (WRF-Chem) model for November-December 2015 with different hypothetical topographic height scenarios. The simulation results show that topography exerts an important influence on haze pollution in downtown Beijing, particularly the typical development of haze pollution. A possible mechanism that underlies the response of haze pollution to topography is that the mountains that surround Beijing tend to produce anomalous southerly winds, high relative humidity, low boundary layer heights, and sinking motion over most of Beijing. These conditions favor the formation and development of haze pollution in downtown Beijing. Furthermore, the reduction percentage in PM2.5 concentrations due to reduced terrain height in the southerly wind (S) mode is almost three times larger than that in the northerly wind (N) mode. In the context of the regional topography, the simple S and N modes represent useful indicators for haze prediction in Beijing to some extent, especially over medium to long time scales.

5.
Chemosphere ; 187: 294-301, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28854384

RESUMO

We present high-resolution lead (Pb) concentrations and isotopic ratios from a northwest Greenland snow pit covering a six-year period between 2003 and 2009. Pb concentrations ranged widely from 2.7 pg g-1 to 97.3 pg g-1, with a mean concentration of 21.6 pg g-1. These values are higher than those recorded for the pre-industrial period. Pb concentrations exhibit seasonal spikes in winter-spring layers. Crustal Pb enrichment factors (EF) suggest that the northwest Greenland snow pit is highly enriched with Pb of predominantly anthropogenic origin. The 206Pb/207Pb ratios ranged from 1.144 to 1.169 with a mean value of 1.156, which fall between less radiogenic Eurasian-type and more radiogenic Canadian-type signatures. This result suggests that several potential source areas of Pb impact on northwest Greenland. Abrupt changes in Pb concentrations and Pb isotope ratios were observed and related to seasonal shifts in source regions of aerosol transport. The 206Pb/207Pb isotope ratio increased gradually between 2003 and 2009. The similarity of the three-isotope plot (206Pb/207Pb versus 208Pb/207Pb) between some of our samples and Chinese urban aerosols suggests a steadily increasing contribution of Chinese Pb to northwest Greenland snow.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/análise , Monitoramento Ambiental , Chumbo/análise , Neve/química , Aerossóis , Canadá , Groenlândia , Indústrias , Isótopos/análise , Estações do Ano
6.
Sci Total Environ ; 592: 627-638, 2017 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-28341468

RESUMO

Based on the hourly PM2.5 concentrations, meteorological variable records and ERA-Interim reanalysis data, a series of diagnostic analyses were conducted to explore the possible meteorological causes for the severe haze pollution that occurred in Beijing in November-December 2015. Using the online-coupled WRF-Chem model and GFS data, the predictability of hourly and daily PM2.5 concentrations was evaluated. The results showed that, in the context of pollutant emission, the severe haze pollution in downtown Beijing in November-December 2015 was primarily attributed to anomalous local meteorological conditions, which were caused and strengthened by anomalous large-scale atmospheric circulations. The abnormal changes in the upper troposphere appeared to trigger the anomalies in the middle-lower troposphere and the local conditions. The numerical simulations can capture the spatial distribution patterns of the PM2.5 concentrations for predictions of 1 to 10days in advance. The PM2.5 concentration trends in downtown Beijing were generally consistent with the predictions on both daily and hourly time-scales, although the predictability decreased gradually as the lead times prolonged. The predictability of the daily mean PM2.5 concentration was slightly higher than that of the hourly concentration. The statistical indices suggested that the predictions of daily and hourly mean PM2.5 concentrations were generally skillful and reliable for maximum lead times of 8 and 5days, respectively.


Assuntos
Poluição do Ar/análise , Monitoramento Ambiental , Tempo (Meteorologia) , Pequim , Material Particulado/análise
7.
Sci Total Environ ; 2017 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-28216028

RESUMO

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

8.
Sci Rep ; 7: 40051, 2017 01 04.
Artigo em Inglês | MEDLINE | ID: mdl-28051170

RESUMO

In January 2016, the Arctic experienced an extremely anomalous warming event after an extraordinary increase in air temperature at the end of 2015. During this event, a strong intrusion of warm and moist air and an increase in downward longwave radiation, as well as a loss of sea ice in the Barents and Kara seas, were observed. Observational analyses revealed that the abrupt warming was triggered by the entry of a strong Atlantic windstorm into the Arctic in late December 2015, which brought enormous moist and warm air masses to the Arctic. Although the storm terminated at the eastern coast of Greenland in late December, it was followed by a prolonged blocking period in early 2016 that sustained the extreme Arctic warming. Numerical experiments indicate that the warming effect of sea ice loss and associated upward turbulent heat fluxes are relatively minor in this event. This result suggests the importance of the synoptically driven warm and moist air intrusion into the Arctic as a primary contributing factor of this extreme Arctic warming event.

9.
Nat Commun ; 5: 4646, 2014 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-25181390

RESUMO

Successive cold winters of severely low temperatures in recent years have had critical social and economic impacts on the mid-latitude continents in the Northern Hemisphere. Although these cold winters are thought to be partly driven by dramatic losses of Arctic sea-ice, the mechanism that links sea-ice loss to cold winters remains a subject of debate. Here, by conducting observational analyses and model experiments, we show how Arctic sea-ice loss and cold winters in extra-polar regions are dynamically connected through the polar stratosphere. We find that decreased sea-ice cover during early winter months (November-December), especially over the Barents-Kara seas, enhances the upward propagation of planetary-scale waves with wavenumbers of 1 and 2, subsequently weakening the stratospheric polar vortex in mid-winter (January-February). The weakened polar vortex preferentially induces a negative phase of Arctic Oscillation at the surface, resulting in low temperatures in mid-latitudes.

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