23 results for qubit oscillator frequency
The Holocene palaeoenvironmental changes reflected in the multi-proxy studies of Lake Słone sediments (SE Poland)
Contributors: Piotr Kulesza, Magdalena Suchora, Irena A. Pidek, Radosław Dobrowolski, Witold P. Alexandrowicz
Frequency diagram of ostracods in the JS-25 profile. ...Frequency diagram of ostracods in the JS-c profile. ...Frequency diagram of fossil Cladocera in the JS-25 profile. ...oscillations. Most significant changes occurred at 12300cal yr BP (Younger...Oscillation”). Lowering of the water table at around 11100–10800cal yr...Frequency diagram of fossil Cladocera in the JS-c profile. ... Multi-proxy data from the Lake Słone sediments (SE Poland) yielded information on the Holocene changes of Lake Słone in a karst region. Changes of limnological conditions and vegetation reconstructions correspond to high resolution multi-proxy records from north-central Europe. Ostracods showed several small oscillations. Most significant changes occurred at 12300cal yr BP (Younger Dryas–Preboreal transition) and between 11800 and 11100cal yr BP (“Preboreal Oscillation”). Lowering of the water table at around 11100–10800cal yr BP was probably connected with abrupt warming at ca. 11000cal BP. Temperature and water depth fell at about 8400–8100cal yr BP (8200cal yr BP). The Atlantic period was generally warm and is divided into two parts: an older one with comparatively stable water level and a second one (between 7000 and 6300cal yr BP) with two phases of higher water level separated by lowering at 6800cal yr BP. At the transition from the Atlantic to the Subboreal (6200–5950cal yr BP) the dry period is more pronounced than changes in the second half of the Atlantic. Since the beginning of the Subboreal an increase in human activity in Central Europe was the main factor shaping the landscape and changing the limnic regimes.
A millennial-long record of warm season precipitation and flood frequency for the North-western Alps inferred from varved lake sediments: implications for the future
Contributors: Benjamin Amann, Sönke Szidat, Martin Grosjean
frequency of flood layers from Lake Oeschinen and flood frequency from...frequency and intensity of storms and floods in the near future. In Europe ... The recent warming of the global climate is well recognized. However, does a warmer climate also mean a moister climate? Does dry get drier and wet get wetter? There are important questions as they relate to changes in the water cycle and impacts the water resources as well as the frequency and intensity of storms and floods in the near future. In Europe, regional climate models do not show consistent and robust results for future hydroclimatic changes and how extreme events will evolve in response to future climate change.
Evolution of subpolar North Atlantic surface circulation since the early Holocene inferred from planktic foraminifera faunal and stable isotope records
Contributors: Francisca Staines-Urías, Antoon Kuijpers, Christoph Korte
frequency oscillations in Subpolar Gyre strength suggest increased surface...Oscillation...frequency and reduced amplitude of the surface hydrographic changes reflect...Oscillation-like conditions. Panel (b) represents a transitional stage ... Past changes in the surface flow regime of two main eastern North Atlantic warm water pathways toward the Nordic seas were reconstructed based on faunal analyses in combination with carbon and oxygen stable isotope measurements in planktic foraminifera. The investigated sites, in the surroundings of the Faroe Islands, are located in the transitional area where surface waters of subpolar and subtropical origin mix before entering the Arctic Mediterranean. In these areas, large-amplitude millennial variability in the characteristics of the upper-water column appears modulated by changes in the intensity of the Subpolar Gyre circulation. From 7.8 to 6 ka BP, faunal records indicate a deep mixed-layer which, in conjunction with lighter δ18O values, suggest that the inflowing Atlantic waters were dominated by a relatively cooler and fresher water mass, reflecting a strengthening of the Subpolar Gyre under conditions of enhanced positive NAO-like forcing and reduced meltwater input. A shift in the hydrographic conditions occurred during the Mid-Holocene (centered at 5 ka BP). At this time, increasing upper water column stratification and the incipient differentiation of the stable isotopic signal of the Iceland–Faroe and Faroe–Shetland surface water masses, suggest increasing influx of warmer, more saline surface waters from the Subtropical Gyre, as Subpolar Gyre circulation weakened. The mid-Holocene decline in Subpolar Gyre strength is presumably related to a shift toward a low state of the NAO-like forcing associated with decreased solar irradiance. Later in the Holocene, from 4 ka BP to present, the increased frequency and reduced amplitude of the surface hydrographic changes reflect corresponding fluctuations in Subpolar Gyre circulation. These high frequency oscillations in Subpolar Gyre strength suggest increased surface circulation sensitivity to moderate freshwater fluxes to the Labrador–Irminger Sea basin, highlighting the importance of the salinity balance in modulating Subpolar Gyre dynamics, particularly under conditions of low NAO atmospheric forcing.
Contributors: Chun-Yi Lin, Chung-Ru Ho, Yung-Hsiang Lee, Nan-Jung Kuo, Shin-Jye Liang
Oscillation (PDO). The size, increasing trend in the IPWP, calculated ...Time–frequency–spectrum–amplitude of SST in the IPWP. ...Time–frequency–spectrum–amplitude of the interannual heat storage anomalies...Time–frequency–spectrum–amplitude of the monthly averaged size in the ...Oscillation...Time–frequency energy distributions using the Hilbert–Huang transform ... The Indo-Pacific warm pool (IPWP) over the Indian Ocean and the Pacific Ocean is the largest warm pool in the global oceans. Its thermal variability and trend between 1982 and 2011 are extracted from the Ensemble Empirical Mode Decomposition method. Time–frequency energy distributions using the Hilbert–Huang transform are computed to evaluate the thermal spectrum-energy. From the SST variability and the heat storage anomaly, we find that the thermal variability is strongly influenced by the Pacific Decadal Oscillation (PDO). The size, increasing trend in the IPWP, calculated from the SST data is (0.18±0.01)×106km2/decade. Besides, the magnitude of increasing rate during the positive phase of the PDO is couple times higher than that during the negative phase. Furthermore, the SST trend is also associated with 1999/2000 climate shift. The heat increases in the IPWP from 1993 to 2011 implied an average warming rate of 1.41Wm−2. The thermal variations in the IPWP are controlled by interannual to decadal variabilities mostly related to the PDO in the Pacific Ocean sector and by annual variability in the Indian Ocean sector.
Investigation of sea surface temperature changes from replicated coral Sr/Ca variations in the eastern equatorial Pacific (Clipperton Atoll) since 1874
Contributors: Henry C. Wu, Mélanie Moreau, Braddock K. Linsley, Daniel P. Schrag, Thierry Corrège
frequency) of each reconstructed component is listed. All time-series ...Oscillation and the El Niño/Southern Oscillation (ENSO) with reduced ENSO...Oscillation...Oscillation (PDO) Index (Mantua et al., 1997). ...frequencies are listed separately. The power spectral density (power distribution ... Sub-seasonally resolved and replicated coral Sr/Ca time series at Clipperton Atoll (10°18′N, 109°13′W) in the eastern Pacific are assessed as a sea surface temperature (SST) proxy in this region with small seasonal SST variability. The composite coral Sr/Ca time series is a partially replicated record of three live and one sub-modern colony of Porites lobata extending back to 1874. Large inter-colony coral Sr/Ca offsets equate to relative SST differences of 0.6 to 4.3°C and limit the ability to reconstruct absolute SST changes. Moreover, the replication method revealed a 12-year section of growth in one colony where mean Sr/Ca was anomalously low (~1°C higher SST) relative to the other colonies without evidence of diagenesis or other significant skeletal alterations. The presence of this anomalous interval supports the need for multi-coral Sr/Ca replication in specific sites or regions. The Clipperton Composite Sr/Ca anomaly record is significantly coherent (r=0.71–0.76, p<0.001) with gridded instrumental SSTs but with larger amplitude decadal variance that appears to more accurately represent actual SST variability at Clipperton. The amplitude of the secular warming trend during the last century at Clipperton is 0.3 to 0.6°C larger (~twice as large) than the trend in the poorly “ground-truthed” instrumental SST records for the region. The interannual and decadal variability in Clipperton coral Sr/Ca demonstrates strong coherence to the Pacific Decadal Oscillation and the El Niño/Southern Oscillation (ENSO) with reduced ENSO variability from 1920 to late 1930s and enhanced variability in the late twentieth century.
Research paper - High-frequency surface water changes in the Tagus prodelta off Lisbon, eastern North Atlantic, during the last two millennia
Contributors: Helga B. Bartels-Jónsdóttir, Antje H.L. Voelker, Fatima G. Abrantes, Emilia Salgueiro, Teresa Rodrigues, Karen Luise Knudsen
Oscillation. In addition, the assemblage composition together with the ... A high-resolution sedimentary sequence recovered from the Tagus prodelta has been studied with the objective to reconstruct multi-decadal to centennial-scale climate variability on the western Iberian Margin and to discuss the observations in a wider oceanographic and climatic context. Between ca. 100BC and AD400 the foraminiferal fauna and high abundance of Globorotalia inflata indicate advection of subtropical waters via the Azores Current and the winter-time warm Portugal Coastal Current. Between ca. AD400 and 1350, encompassing the Medieval Climate Anomaly (MCA), enhanced upwelling is indicated by the planktonic foraminiferal fauna, in particular by the high abundance of upwelling indicator species Globigerina bulloides. Relatively light δ18O values and high sea surface temperature (SST) (reconstructed from foraminiferal assemblages) point to upwelling of subtropical Eastern North Atlantic Central Water. Between ca. AD1350 and 1750, i.e. most of the Little Ice Age, relatively heavy δ18O values and low reconstructed SST, as well as high abundances of Neogloboquadrina incompta, indicate the advection of cold subpolar waters to the area and a southward deflection of the subpolar front in the North Atlantic, as well as changes in the mode of the North Atlantic Oscillation. In addition, the assemblage composition together with the other proxy data reveals less upwelling and stronger river input than during the MCA. Stronger Azores Current influence on the Iberian Margin and strong anthropogenic effect on the climate after AD1750 is indicated by the foraminiferal fauna. The foraminiferal assemblage shows a significant change in surface water conditions at ca. AD1900, including enhanced river runoff, a rapid increase in temperature and increased influence of the Azores Current. The Tagus record displays a high degree of similarity to other North Atlantic records, indicating that the site is influenced by atmospheric–oceanic processes operating throughout the North Atlantic, as well as by local changes.
Anchovy population and ocean-climatic fluctuations in the Humboldt Current System during the last 700years and their implications
Contributors: Marcos Guiñez, Jorge Valdés, Abdel Sifeddine, Mohammed Boussafir, Paola M. Dávila
oscillations experienced by the ocean-climate system versus the sea surface...frequency states for cycles per 6years. ...Oscillation (instrumental record, Mantua et al., 1997) versus the SDR ... A marine sedimentary record collected from 87m water depth in a coastal environment of the Humboldt Current System (Mejillones Bay, 23° S, northern Chile) was used to reconstruct the past 700years of ocean-climatic conditions and to study the influence of any changes on anchovy population dynamics. We analyzed quartz, organic carbon, total nitrogen, alkenones and fish scales. Four stratigraphic units in the sediment column correspond with fluctuations in these and other proxies. Low Scale Deposition Rate (SDR) values from 1330 to 1420 suggest a low abundance of anchovy in this coastal environment. Three subsequent cycles of ca. 170years each showed an increase and decrease of anchovy populations, which is in agreement with changes in the wind regime, sea surface temperature and primary productivity.
Contributors: Stephen P. Obrochta, Hiroko Miyahara, Yusuke Yokoyama, Thomas J. Crowley
frequency domain, causing lower (higher) frequency bands to appear artificially...oscillation is primarily limited to the short glacial Stage 4, the age...frequency of the Site 609 series prior to 200-year interpolation. ...frequencies higher than 500 years. White areas in the wavelet indicate...frequency of millennial-scale spectral peaks in best-fit age model (1/...frequencies or combination tones to explain a phenomenon of such fleeting...frequency, top) and HSG (bottom). The frequencies of significant periods ... Ice-rafting evidence for a “1500-year cycle” sparked considerable debate on millennial-scale climate change and the role of solar variability. Here, we reinterpret the last 70,000 years of the subpolar North Atlantic record, focusing on classic DSDP Site 609, in the context of newly available raw data, the latest radiocarbon calibration (Marine09) and ice core chronology (GICC05), and a wider range of statistical methodologies. A ∼1500-year oscillation is primarily limited to the short glacial Stage 4, the age of which is derived solely from an ice flow model (ss09sea), subject to uncertainty, and offset most from the original chronology. Results from the most well-dated, younger interval suggest that the original 1500 ± 500 year cycle may actually be an admixture of the ∼1000 and ∼2000 cycles that are observed within the Holocene at multiple locations. In Holocene sections these variations are coherent with 14C and 10Be estimates of solar variability. Our new results suggest that the “1500-year cycle” may be a transient phenomenon whose origin could be due, for example, to ice sheet boundary conditions for the interval in which it is observed. We therefore question whether it is necessary to invoke such exotic explanations as heterodyne frequencies or combination tones to explain a phenomenon of such fleeting occurrence that is potentially an artifact of arithmetic averaging.
Temporal analysis of rainfall (1871–2012) and drought characteristics over a tropical monsoon-dominated State (Kerala) of India
Contributors: Jobin Thomas, V. Prasannakumar
Oscillation (ENSO). The annual rainfall shows an irregular distribution ... The climate of Kerala is controlled by the monsoon, and the analysis of rainfall and drought scenario, for a period of 141years (1871–72 to 2011–12), reveals a decreasing trend in southwest monsoon, and increasing trends for post-monsoon-, winter- and pre-monsoon-rainfall. The inconsistent periodicity (2–8years) of annual- and seasonal-rainfall agrees with the periodicity of El-Nino Southern Oscillation (ENSO). The annual rainfall shows an irregular distribution, and is concentrated roughly in half of the year, which is due to the monsoon-driven climatic seasonality. The rainfall concentration at annual-, southwest monsoon-, and winter-scales exhibits significant decreasing trends, implying decline in the degree of irregularity in annual- and seasonal-rainfall. Temporal distribution as well as severity of the drought events have been analyzed using various drought indicators. The drought pattern is not only related to the rainfall trends, but also to the rainfall concentration (or monthly rainfall heterogeneity). The decreasing rainfall during southwest monsoon contributes to short-term meteorological droughts, which have serious implications on the agricultural sector and water resources of Kerala, while the increasing rainfall during other seasons helps to reduce the drought severity.
Contributors: S.V. Kolomiyets
oscillations with the envelope curves ABCD of meteor echoes for the idealized ... The uncertainties in meteor radar data and the problem of hyperbolic meteors are interconnected. Meteor orbital data, obtained by the Meteor Automatic Radar System (MARS) at the Kharkiv Institute of Radio Electronics, Ukraine, was used to develop the algorithm to determine the uncertainties of the orbital elements obtained by radar systems such as MARS. We have constructed the empirical model of the distribution of uncertainties in the orbital elements of meteor radar data. MARS had a high effective sensitivity (the limiting magnitude of observed meteors was close to 12 ^ M) and was capable to carry out comprehensive geophysical and astronomical studies of meteors. When we register meteor numbers, radiants, meteoroid velocities, we can talk about astronomical observations. The main objective of meteor astronomy research is to determine the orbit of the meteoroid, in other words, to study a meteoroid as an astronomical object of the Solar System. Sometimes meteoroids may have an interstellar origin. Such meteoroids usually have hyperbolic orbits (i.e. with eccentricities e>1). However, hyperbolic orbits of meteoroids may have another origin, e.g. arise due to errors of observations (primarily due to the errors of eccentricities – σe). To correctly interpret the astronomical data, it is necessary to know how the errors are calculated. In this paper, we estimated the uncertainties in the Kharkiv meteor radar data (the average σe ~0.2) and discussed their connection to the problem of hyperbolic meteors. We obtained ~0.8% of total number of meteoroid orbits in 1975, which we named “real” hyperboles, i.e. with eccentricities more or equal 1+2σe.