| 1. |
|
|
| 2. |
- Emile-Geay, J., et al.
(author)
-
Data Descriptor: A global multiproxy database for temperature reconstructions of the Common Era
- 2017
-
In: Scientific Data. - : Springer Science and Business Media LLC. - 2052-4463. ; 4
-
Journal article (peer-reviewed)abstract
- Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850-2014. Global temperature composites show a remarkable degree of coherence between high-and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era, and is shared in the Linked Paleo Data (LiPD) format, including serializations in Matlab, R and Python. Since the pioneering work of D'Arrigo and Jacoby1-3, as well as Mann et al. 4,5, temperature reconstructions of the Common Era have become a key component of climate assessments6-9. Such reconstructions depend strongly on the composition of the underlying network of climate proxies10, and it is therefore critical for the climate community to have access to a community-vetted, quality-controlled database of temperature-sensitive records stored in a self-describing format. The Past Global Changes (PAGES) 2k consortium, a self-organized, international group of experts, recently assembled such a database, and used it to reconstruct surface temperature over continental-scale regions11 (hereafter, ` PAGES2k-2013'). This data descriptor presents version 2.0.0 of the PAGES2k proxy temperature database (Data Citation 1). It augments the PAGES2k-2013 collection of terrestrial records with marine records assembled by the Ocean2k working group at centennial12 and annual13 time scales. In addition to these previously published data compilations, this version includes substantially more records, extensive new metadata, and validation. Furthermore, the selection criteria for records included in this version are applied more uniformly and transparently across regions, resulting in a more cohesive data product. This data descriptor describes the contents of the database, the criteria for inclusion, and quantifies the relation of each record with instrumental temperature. In addition, the paleotemperature time series are summarized as composites to highlight the most salient decadal-to centennial-scale behaviour of the dataset and check mutual consistency between paleoclimate archives. We provide extensive Matlab code to probe the database-processing, filtering and aggregating it in various ways to investigate temperature variability over the Common Era. The unique approach to data stewardship and code-sharing employed here is designed to enable an unprecedented scale of investigation of the temperature history of the Common Era, by the scientific community and citizen-scientists alike.
|
|
| 3. |
- Fujita, S., et al.
(author)
-
Spatial and temporal variability of snow accumulation rate on the East Antarctic ice divide between Dome Fuji and EPICA DML
- 2011
-
In: The Cryosphere. - : Copernicus GmbH. - 1994-0416 .- 1994-0424. ; 5:4, s. 1057-1081
-
Journal article (peer-reviewed)abstract
- To better understand the spatio-temporal variability of the glaciological environment in Dronning Maud Land (DML), East Antarctica, a 2800-km-long Japanese-Swedish traverse was carried out. The route includes ice divides between two ice-coring sites at Dome Fuji and EPICA DML. We determined the surface mass balance (SMB) averaged over various time scales in the late Holocene based on studies of snow pits and firn cores, in addition to radar data. We find that the large-scale distribution of the SMB depends on the surface elevation and continentality, and that the SMB differs between the windward and leeward sides of ice divides for strong-wind events. We suggest that the SMB is highly influenced by interactions between the large-scale surface topography of ice divides and the wind field of strong-wind events that are often associated with high-precipitation events. Local variations in the SMB are governed by the local surface topography, which is influenced by the bedrock topography. In the eastern part of DML, the accumulation rate in the second half of the 20th century is found to be higher by similar to 15% than averages over longer periods of 722 a or 7.9 ka before AD 2008. A similar increasing trend has been reported for many inland plateau sites in Antarctica with the exception of several sites on the leeward side of the ice divides.
|
|
| 4. |
- Isaksson, E, et al.
(author)
-
Ice cores from Svalbard :useful archives of past climate and pollution history.
- 2003
-
In: Physics and chemistry of the earth. Part A. - : Elsevier BV. - 1464-1895 .- 1873-4642 .- 1474-7065. ; 28:28-32, s. 1217-1228
-
Journal article (peer-reviewed)abstract
- Ice cores from the relatively low-lying ice caps in Svalbard have not been widely exploited in climatic and environmental studies due to uncertainties about the effect of melt water percolation. However, results from two recent Svalbard ice cores, at Lomonosovfonna (1250 m asl) and Austfonna (750 m asl), have shown that with careful site selection, high-resolution sampling and multiple chemical analyses, it is possible to recover ice cores with partly preserved annual signals. These cores are estimated to cover at least the past 600 years and have been dated using a combination of known reference horizons and glacial modeling. The δ18O data from both Lomonosovfonna and Austfonna ice cores suggest that the 20th century was the warmest during the past 600 years. A comparison of the ice core and sea ice records from this period suggests that sea ice extent and Austfonna δ18O are linked over the past 400 years. This may reflect the position of the storm tracks and their direct influence on the relatively low altitude Austfonna. Lomonosovfonna may be less sensitive to such changes and primarily record atmospheric changes due to its higher elevation. The anthropogenic influence on Svalbard environment is illustrated by increased levels of non-sea-salt sulphate, nitrate, acidity, fly-ash and organic contaminants particularly during the second half of 1900s. Decreased concentrations of some components in recent decades most likely reflect emission and use restrictions. However, some current-use organic pesticide compounds show growing concentrations in near surface layers.
|
|
| 5. |
|
|
| 6. |
- Esteves, G. J., et al.
(author)
-
Effect of transcranial direct current stimulation on supramaximal intermittent exercise performance
- 2019
-
In: Motriz. Revista de Educacao Fisica. - : Universidade Estadual Paulista - UNESP. - 1415-9805. ; 25:4
-
Journal article (peer-reviewed)abstract
- Aims: Our purpose was to determine whether Transcranial Direct Current Stimulation (tDCS) improves performance in untrained individuals for supramaximal intermittent exercise. Methods: In a cross-over design, 11 healthy male subjects (26.8 ± 4.6 years) performed four Wingate trials after 20 minutes of anodal or sham tDCS over the left Insular Cortex (IC). For performance indexes, Relative Peak Power (RPP), Relative Average Power (RAP) and Fatigue Index (FI) were computed. Also, a Rating of Perceived Exertion (RPE) and Electromyography (EMG) signal were used to assess central and muscle fatigue development. Results: There was a significant difference over trials on all performance indexes, but there were no significant condition x trial interactions for any of the indexes. RPE increased significantly over trials, but there was no condition x trial interaction. There was no significant difference over trials on EMG for the rectus femoris and vastus medialis muscles; however, EMG decreased over trials for the vastus lateralis muscle. Furthermore, there was no condition x trial interaction on the EMG signal for any of the muscles.Conclusion: Our findings suggest that the anodal tDCS technique has no impact on physical performance, perceived exertion nor muscle fatigue development for supramaximal intermittent exercise.
|
|
| 7. |
- Isaksson, Elisabeth, et al.
(author)
-
Two ice core δ18O records from Svalbard illustrating climate and sea ice variability over the last 400 years
- 2005
-
In: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 15:4, s. 501-509
-
Journal article (peer-reviewed)abstract
- Ice cores from the relatively low-lying ice caps in Svalbard have not been widely exploited in climatic studies owing to uncertainties about the effect of meltwater percolation. However, results from two new Svalbard ice cores, at Lomonosovfonna and Austfonna, have shown that with careful site selection, high-resolution sampling and multiple chemical analyses it is possible to recover ice cores from which part of the annual signals are preserved, despite the considerable meltwater percolation. The new Svalbard ice cores are positioned in different parts of Svalbard and cover the past 800 years. In this paper we focus on the last 400 years. The 6180 signals from the cores are qualitatively similar over most of the twentieth century, suggesting that they record the same atmospheric signal. Prior to AD 1920, the Austfonna ice core exhibits more negative 6180 values than Lomonosovfonna, although there are intermittent decadal-scale periods throughout the record with similar values. We suggest that the differences reflect the effect of the inversion layer during the winter. The pattern in the 6180 records is similar to the Longyearbyen airtemperature record, but on an annual level the correlation is low. The Austfonna record correlates well with the temperature record from the more distant and southwesterly located Jan Mayen. A comparison of the ice-core and sea-ice records from this period suggests that sea-ice extent and Austfonna 6180 are related over the past 400 years. This may reflect the position of the storm tracks and their direct influence on the relatively low-altitude Austfonna. Lomonosovfonna may be less sensitive to such changes and primarily record free atmospheric changes instead of variations in sea-ice extent, the latter is probably a result of its higher elevation.
|
|
