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.
... Frequency diagram of fossil Cladocera in the JS-c profile.
Contributors:Stephen P. Obrochta, Hiroko Miyahara, Yusuke Yokoyama, Thomas J. Crowley
Distribution of ensemble-mean and 1σ range of significant spectral peaks in alternate age models. Shaded vertical bars indicate sum total within each band. Vertical dashed lines indicate the frequency of millennial-scale spectral peaks in best-fit age model (1/2180, 1/1390, and 1/980 years). Results are plotted in the frequency domain, causing lower (higher) frequency bands to appear artificially narrow (wide) (See text for explanation of bandwidths).
... MTM power spectrum with F-test (green) and confidence intervals for IntCal 09 14C production (analyzed to a 1/100 year frequency, top) and HSG (bottom). The frequencies of significant periods in 14C production are shown as dark red and dark blue lines for 95% and 90% confidence respectively as determined by F-test. Light colored lines represent heterodynes of all >90% confident peaks in the production series to 1/100 years. Black circles indicate the location of discrete spectral peaks in the HSG series.
... Wavelet analysis of the stacked Holocene HSG record of Bond et al. (2001) (left) and DSDP Site 609 (Bond et al., 1999) (right). Solid black lines indicate the 95% confidence intervals, and the hatched area represents the cone of influence. The 609 record was interpolated to a 200-year time step, detrended, and filtered to removed frequencies higher than 500 years. White areas in the wavelet indicate the nyquist frequency of the Site 609 series prior to 200-year interpolation.
Time–frequency–spectrum–amplitude of the interannual heat storage anomalies in the IPWP.
... Time–frequency–spectrum–amplitude of SST in the IPWP.
... Pacific Decadal Oscillation... Time–frequency–spectrum–amplitude of the monthly averaged size in the IPWP.
Contributors:Francisca Staines-Urías, Antoon Kuijpers, Christoph Korte
Surface circulation and convection intensity in the subpolar North Atlantic under high (a) and low (c) Subpolar Gyre (SPG) activity corresponding to positive and negative North Atlantic Oscillation-like conditions. Panel (b) represents a transitional stage. The position of deep convection sites is denoted by the solid (intense) and dashed (incipient) circles (Sarafanov, 2009). Larger, shaded ovals represent areas where the Atlantic Inflow waters are entrained into the Arctic Mediterranean (Sarafanov et al., 2010). STG, Subtropical Gyre.
... North Atlantic Oscillation
Contributors:Helga B. Bartels-Jónsdóttir, Antje H.L. Voelker, Fatima G. Abrantes, Emilia Salgueiro, Teresa Rodrigues, Karen Luise Knudsen
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.
Contributors:Henry C. Wu, Mélanie Moreau, Braddock K. Linsley, Daniel P. Schrag, Thierry Corrège
El Niño/Southern Oscillation... Singular Spectrum Analysis (SSA) results of the Clipperton composite Sr/Ca and δ18Osw time-series with various greater Pacific Ocean climate indices and time-series.
The percent variances of the interannual variability (~3–7 years) and decadal/interdecadal variability (10–20 years) frequencies are listed separately. The power spectral density (power distribution of the variance of the time series over each frequency) of each reconstructed component is listed. All time-series were processed identically for: Niño Regions 3 and 3.4 SST anomaly (Reynolds et al., 2002); Extended Reconstructed SST anomaly v.3b (ERSST) for the grid centered on 10° N, 110° W (Smith et al., 2008); Palmyra Sr/Ca anomaly (Nurhati et al., 2011); ENSO Modoki Index (Ashok et al., 2007); and the Pacific Decadal Oscillation (PDO) Index (Mantua et al., 1997).
Comparison of the reconstructed February–April precipitation with the Pacific climate. (a) The standardized November–April Southern Oscillation Index (SOI) (i.e., difference of the sea level pressure between Tahiti and Darwin, Australia) over 1952–2013, and (b) the Niño3.4 November–April sea surface temperature anomaly over 1951–2013. Note: the right y-axis in Fig. 8(a) was reversed for direct comparison.
... February–April total precipitation reconstruction in the Xianxia Mountains, southeastern China. (a), Comparison of actual (solid line) and reconstructed (dotted line) precipitation for 1951–2012; and (b), the reconstructed precipitation (thin line), its 10-yr FFT smoothing (thick line) to highlight the low-frequency variability, and the average value (horizontal line) from 1856 to 2013.
Contributors:Marcos Guiñez, Jorge Valdés, Abdel Sifeddine, Mohammed Boussafir, Paola M. Dávila
Spectral analysis for Mejillones Bay proxy time series (a) Anchovy SDR, (b) Sea Surface Temperature, (c) Organic Carbon, and (d) C37. The straight line corresponds to the White Noise Spectrum (WNS), and the frequency states for cycles per 6years.
... Comparison between the Pacific Decadal Oscillation (instrumental record, Mantua et al., 1997) versus the SDR of anchovy for the last 100years. The dotted line corresponds to the PDO.
... Comparative analysis of the different oscillations experienced by the ocean-climate system versus the sea surface temperatures recorded in Mejillones Bay sediments and the anchovy SDR records in our samples.
... Spectral analysis for the (a) Oxygen Index and climatological time series, (b) PDO, (c) NAO and (d) Solar Irradiance Index. The straight line corresponds to the White Noise Spectrum (WNS), and the frequency states for cycles per 6years.
Contributors:Lesleigh Anderson, Max Berkelhammer, John A. Barron, Byron A. Steinman, Bruce P. Finney, Mark B. Abbott
Lake sediment oxygen isotope records (calcium carbonate-δ18O) in the western North American Cordillera developed during the past decade provide substantial evidence of Pacific ocean–atmosphere forcing of hydroclimatic variability during the Holocene. Here we present an overview of 18 lake sediment δ18O records along with a new compilation of lake water δ18O and δ2H that are used to characterize lake sediment sensitivity to precipitation-δ18O in contrast to fractionation by evaporation. Of the 18 records, 14 have substantial sensitivity to evaporation. Two records reflect precipitation-δ18O since the middle Holocene, Jellybean and Bison Lakes, and are geographically positioned in the northern and southern regions of the study area. Their comparative analysis indicates a sequence of time-varying north–south precipitation-δ18O patterns that is evidence for a highly non-stationary influence by Pacific ocean–atmosphere processes on the hydroclimate of western North America. These observations are discussed within the context of previous research on North Pacific precipitation-δ18O based on empirical and modeling methods. The Jellybean and Bison Lake records indicate that a prominent precipitation-δ18O dipole (enriched-north and depleted-south) was sustained between ~3.5 and 1.5ka, which contrasts with earlier Holocene patterns, and appears to indicate the onset of a dominant tropical control on North Pacific ocean–atmosphere dynamics. This remains the state of the system today. Higher frequency reversals of the north–south precipitation-δ18O dipole between ~2.5 and 1.5ka, and during the Medieval Climate Anomaly and the Little Ice Age, also suggest more varieties of Pacific ocean–atmosphere modes than a single Pacific Decadal Oscillation (PDO) type analogue. Results indicate that further investigation of precipitation-δ18O patterns on short (observational) and long (Holocene) time scales is needed to improve our understanding of the processes that drive regional precipitation-δ18O responses to Pacific ocean–atmosphere variability, which in turn, will lead to a better understanding of internal Pacific ocean–atmosphere variability and its response to external climate forcing mechanisms.
Table 3 shows that the multiple periodicity in permafrost temperature was almost identical to the periodicity observed in air temperature, LWD, SWD, precipitation, and wind speed. To evaluate the relationship between oscillations in permafrost temperature and climate change, their correlation coefficients were analyzed (Table 4). As wavelet variance was used to detect the main periods in these time sequences, and this reflects the period oscillations of these time series at various time scales and their intensities, we calculated the correlation coefficients between wavelet variance of permafrost temperature and climate change (Table 4). In this case, a wavelet variance of climate change was generated by stacking the wavelet variance of all five climatic factors.Table 4Correlation coefficients between multi-period of soil temperature and climate change.CM2 siteFH1 site0.5 m6 m0.5 m6 mClimate change0.99∗0.16∗∗0.97∗0.73∗∗Significant at the 1% significance level (P < 0.001).∗∗Significant at the 5% significance level (P < 0.05).... Wavelet variance (left panels) and time-frequency structure of real wavelet transformation coefficients (right panels) of soil temperatures. a) 0.5 m depth at CM2 site; b) 6 m depth at CM2 site; c) 0.5 m depth at FH1 site; d) 6 m depth at FH1 site.
... Most of the observation sites for long-term permafrost monitoring on the QXP are located along the QXH. These sites provided time series data for our study of the impact of five climatic factors on permafrost in the time-frequency domain. Soil temperatures were measured at 10 sites between Xidatan, near the northern boundary of the permafrost, and Anduo on the southern boundary of the permafrost along the QXH, traversing roughly 550 km of terrain (Fig. 1) (Wu and Zhang, 2008; Gao et al., 2014). Geographical information for ten monitoring sites is listed in Table 1. Mean annual air temperature ranges from about −6.5 °C at the Kunlun Pass to about −2.0 °C at Anduo along the QXH. Annual total precipitation is generally less than 300 mm, ranging from 250 mm in the north to 450 mm in the south; about 10% of the annual precipitation falls as snow (Wu and Zhang, 2010). Vegetation cover ranges from less than 30% in the north to above 90% in the south, with vegetation height of around 10–15 cm. Near-surface deposits are dominated by coarse materials, such as gravel and sandy soils (Wu and Zhang, 2008). For more detailed information on these monitoring sites see Wu and Zhang (2010).Table 1Geographical information of the 10 monitoring sites.No.Site nameAreasElevation (m)LatitudeLongitudeDistance between site to highway (m)1KM1Kunlunshan Mountains477035°37′58″N94°04′18″E202KM2475935°37′12″N94°04′13″E303CM1Chumaer River455235°30′50″N93°44′05″E304CM2448235°23′49″N93°32′01″E305WD1Wudaoliang461035°13′48″N93°05′06″E306WD2470735°07′36″N93°02′12″E307FH1Fenghuo Mountains493834°41′24″N92°53′30″E1008TG1Tanggula Mountains499732°42′30″N91°52′16″E209TM1Touerjiu Mountains487332°29′33″N91°49′17″E5010AD1Near Anduo478632°23′00″N91°42′27″E20... Wavelet variance (left panels) and time-frequency structure of real wavelet transformation coefficients (right panels) of climatic factors. a) air temperature; b) LWD; c) SWD; d) precipitation; e) wind speed.