ENSO signals and their spatial-temporal variation characteristics recorded by the sea-level changes in the northwest Pacific margin during 1965–2005

Sea-level is closely linked to the Earth’s climate and its change is important as a metric for global and regional climate change. Identifying, extracting, and revealing such information through detailed analysis is the prerequisite for understanding the mechanisms of sea-level change. The monthly- average tide-change records reported and examined in this paper are from 10 tide gauge stations distributed in the northwest margin of the Pacific Ocean, registered during the period 1965-2005. In particular, we have utilized the Second Order Blind Identification (SOBI) method to identify and the Empirical Mode Decomposition (EMD) method to extract the El Niño-Southern Oscillation (ENSO) signals imprinted in those tide gauge records; and subsequently, we have investigated the spatial-temporal characteristics of the extracted ENSO signals using wavelet analysis methods. The following results are obtained: (1) the ENSO events recorded by each tide gauge series are of different types and intensity, which show considerable temporal-spatial variation characteristics, with sea-level responses to ENSO signals remarkably stronger in low latitude areas than in medium-high latitude areas; (2) due to the influences of ocean currents, topographical conditions, and other factors, there exist variations in the type of relationship between the sea-level changes and the recorded ENSO events at different latitudes; (3) sea-level changes can also denote scale-variation characteristics of ENSO events, and particularly, since 1980s, all the tide gauges located south of Kanmen show intense responses to ENSO and the timescale of ENSO events extended gradually from around 4 years to 2–8 years, reflecting variations in the intensity and frequency of ENSO events; and (4) reverse changes of certain scale were noted before and after strong ENSO events recorded by sea-level changes, supporting the research findings about the interaction (mutual coupling and superimposition) between the probability of occurrence of strong ENSO events and their time scale.     

Sensitivity of climate response to variations in freshwater hosing location

In a recent intercomparison of the response of general circulation models (GCMs) to high-latitude freshwater forcing (Stouffer et al., J Climate 19(8):1365–1387, 2006), a number of the GCMs investigated showed a localised warming response in the high-latitude North Atlantic, as opposed to the cooling that the other models showed. We investigated the causes for this warming by testing the sensitivity of the meridional overturning circulation (MOC) to variations in freshwater forcing location, and then analysing in detail the causes of the warming. By analysing results from experiments with HadCM3, we are able to show that the high-latitude warming is independent of the exact location of the additional freshwater in the North Atlantic or Arctic Ocean basin. Instead, the addition of freshwater changes the circulation in the sub-polar gyre, which leads to enhanced advection of warm, saline, sub-surface water into the Greenland–Iceland–Norwegian Sea despite the overall slowdown of the MOC. This sub-surface water is brought to the surface by convection, where it leads to a strong warming of the surface waters and the overlying atmosphere.     

Surface dynamic deformation estimates from local seismicity: the Itoiz reservoir,Spain

We analyze the ground motion time histories due to the local seismicity near the Itoiz reservoir to estimate the near-source, surface 3D displacement gradients and dynamic deformations. The seismic data were obtained by a semipermanent broadband and accelerometric network located on surface and at underground sites. The dynamic deformation field was calculated by two different methodologies: first, by the seismo-geodetic method using the data from a three-station microarray located close to the dam, and second, by single station estimates of the displacement gradients. The dynamic deformations obtained from both methods were compared and analyzed in the context of the local free-field effects. The shallow 1D velocity structure was estimated from the seismic data by modeling the body wave travel times. Time histories obtained from both methods result quite similar in the time window of body wave arrivals. The strain misfits between methods vary from 1.4 to 35.0 % and rotational misfits vary from 2.5 to 36.0 %. Amplitudes of displacement gradients vary in the range of 10^?8 to 10^?7 strains. From these results, a new scaling analysis by numerical modeling is proposed in order to estimate the peak dynamic deformations for different magnitudes, up to the expected maximum M _w in the region (M5.5). Peak dynamic deformations due to local M _w5.5 earthquakes would reach amplitudes of 10^?5 strain and 10^?3 radians at the Itoiz dam. The single station method shows to be an adequate option for the analysis of local seismicity, where few three-component stations are available. The results obtained here could help to extend the applicability of these methodologies to other sites of engineering interest.     

Rock-magnetic properties of Neogene sediments, northern flank of Tianshan Mountains

Analyses of rock-magnetic properties of Neogene sediments of the Taxihe section, northern Tianshan Mountains, show that the section can be classified into three categories including lacustrine facies, fluvial facies and alluvial facies, which correspond to the lower, middle and upper of the Taxihe section respectively. The magnetic minerals of the lacustrine facies may be affected by the process of weath- ering, lithogenesis and biolithogenesis besides the source of the sediments. The natural remanence intensities are between 10-3 A/m and 10-2 A/m. The minerals are dominated by magnetite and the high coercive magnetic mineral may be goethite. The magnetic grains are the mixture of PSD SD or SD SP. The natural remanence intensities of the strata of fluvial facies are between 10-2 A/m and 10-1 A/m, about ten times that of the lacustrine facies. The magnetic minerals are mainly magnetite and hematite, and the magnetic grains are mainly PSD. The characteristic remanence (ChRM) carriers are magnetites. In the alluvial facies, the natural remanence intensities are mostly less than 1×10-2 A/m. The magnetic minerals of the series are dominated by magnetite and hematite, almost the same as the fluvial facies. But the difference is that most of the stepwise demagnetization can reveal two components and the ChRM carriers are hematites. The magnetic grains are PSD in terms of the hysteresis parameters.     

Geochemical anomalies of hydrothermal plume at EPR 13°N

During the DY105-12, 14cruise (R/V DAYANG YIHAO, November 2003) on East Pacific Rise (EPR) 12- 13°N, the submarine hydrothermal activity was investigated and the CTD hydrocast was carried out at EPR12°39′N-12°54′N. From the temperature anomalies and the concentrations of magnesium, chlorine, bromine in seawater samples, we discover that magnesium depletes 9.3%-22.4%, chlorine and bro- mine enrich 10.3%-28.7% and 10.7%-29.0% respectively relative to normal seawater at the stations which have chemistry anomalies, moreover temperature and chemistry anomalies are at the same layer. The depletion of magnesium in the plume may be caused by a fluid lacking of magnesium which rises after the hydrothermal fluid reaches the equilibrium with ambient seawater, the enrichment of chlorine and bromine might be the result of inputting later brine which is generated by phase separation due to hydrothermal activity. In addition, the Br/Cl ratio in the abnormal layers at the survey area is identical to that in seawater, which implies that halite dissolution (or precipitation) occurs neither when the fluid is vented nor when hydrothermal fluid entraining ambient seawater rises to form plume. From the ab- normal instance at E55 station, it is very possible that there might exist a new hydrothermal vent site.     

Wetlands of Northeast Asia and High Asia: an overview

This review reports background information on wetlands in the Northeast Asia and High Asia areas, including wetland coverage and type, significance for local populations, and threats to their vitality and protection, with particular focus on the relationship of how global change influenced wetlands. Natural wetlands in these areas have been greatly depleted and degraded, largely due to global climate change, drainage and conversion to agriculture and silviculture, hydrologic alterations, exotics invasions, and misguided management policies. Global warming has caused wetland and ice-sheet loss in High Asia and permafrost thawing in tundra wetlands in Northeast Asia, and hence induced enormous reductions in water-storage sources in High Asia and carbon loss in Northeast Asia. This, in the long term, will exacerbate chronic water shortage and positively feed back global warming. Recently, better understanding of the vital role of healthy wetland ecosystems to Asia’s sustainable economic development has led to major efforts in wetland conservation and restoration. Nonetheless, collaborative efforts to restore and protect the wetlands must involve not only the countries of Northeast and High Asia but also international agencies. Research has been productive but the results should be more effectively integrated with policy-making and wetland restoration practices under future climatic scenarios.     

Simplification and Validation of a Spectral-Tensor Model for Turbulence Including Atmospheric Stability

A spectral-tensor model of non-neutral, atmospheric-boundary-layer turbulence is evaluated using Eulerian statistics from single-point measurements of the wind speed and temperature at heights up to 100 m, assuming constant vertical gradients of mean wind speed and temperature. The model has been previously described in terms of the dissipation rate \(\epsilon \), the length scale of energy-containing eddies \(\mathcal {L}\), a turbulence anisotropy parameter \(\varGamma \), the Richardson number Ri, and the normalized rate of destruction of temperature variance \(\eta _\theta \equiv \epsilon _\theta /\epsilon \). Here, the latter two parameters are collapsed into a single atmospheric stability parameter z / L using Monin–Obukhov similarity theory, where z is the height above the Earth’s surface, and L is the Obukhov length corresponding to \(\{Ri,\eta _\theta \}\). Model outputs of the one-dimensional velocity spectra, as well as cospectra of the streamwise and/or vertical velocity components, and/or temperature, and cross-spectra for the spatial separation of all three velocity components and temperature, are compared with measurements. As a function of the four model parameters, spectra and cospectra are reproduced quite well, but horizontal temperature fluxes are slightly underestimated in stable conditions. In moderately unstable stratification, our model reproduces spectra only up to a scale \(\sim \) 1 km. The model also overestimates coherences for vertical separations, but is less severe in unstable than in stable cases.     

Precise dating of the Dansgaard-Oeschger event 4 and its sub-cycles: Evidence from a stalagmite from Xianyun Cave in Longyan City,Fujian Province

The Dansgaard-Oeschger event 4(DO4 event) is a significant warming event that occurred in the late Marine Isotope Stage 3. At present,there are different understandings about the detailed characteristics and internal structures of the DO4 event. Based on 6 precisely-dated ²³⁰Th ages and 188 oxygen isotope data of a stalagmite(No.XYⅢ-28)from the Xianyun Cave,Fujian Province,we present δ¹⁸O time series with an average resolution of 7 yr from 29.13 to 27.94 kyr B.P. Our new stalagmites δ¹⁸O records uncover the detailed processes of the DO4 event. The onset and end time of the DO4 event recorded by the stalagmite δ¹⁸O is 28.83±0.06 and 28.46±0.06 kyr B.P.,respectively, and the duration is 0.37±0.06 kyr. Differential with abrupt change of NGRIP ice core δ¹⁸O record at the onset of DO4 based on the GICC05 layer count time scale,the Xianyun Cave δ¹⁸O shows a relatively slow change. The Xianyun stalagmite δ¹⁸O values negatively shift by 0.4‰ within 145±60 yr,which indicates that the Xianyun Cave was likely affected by the ocean-atmosphere coupling of the tropical. In addition,the Xianyun stalagmite δ¹⁸O reveals a series of sub-million-scale summer monsoon enhancement events in and around the DO4 event,corresponding to the NGRIP ice core δ¹⁸O record and the Arabian Sea basin record. Our results suggest that the East Asian summer monsoon is related to the north-high latitude temperature and the ITCZ position changes on the sub-millennium-scale event.     

The burial efficiency of organic carbon in the sediments of Lake Kinneret

Even though lake sediments constitute a significant long-term carbon sink, studies on the regulation of carbon burial in lakes sediments have, to date, been surprisingly few. We investigated to what degree the organic carbon (OC) being deposited onto the bottom of Lake Kinneret (Israel) is buried in the sediment at four different sites with varying degrees of oxygenation and varying supply of allochthonous particles from the River Jordan. For estimation of the OC burial efficiency (OC BE), i.e., the ratio between buried and deposited OC, we calculated OC burial from dated sediment cores, and calculated OC deposition using three different approaches. Calculation of OC deposition from sediment trap-derived mass deposition rates multiplied with the OC content of surface sediment yielded OC BE values that were at odds with published values for sediments dominated by autochthonous OC sources. Calculation via sediment trap data on organic matter flux collected within the Lake Kinneret monitoring program, as well as calculation of OC deposition as the sum of OC burial plus OC mineralization, returned fairly congruent estimates of OC BE (range 10–41%), but only if the sediment trap data were corrected for the proportion of resuspended particles in the traps. Differences in OC BE between sites were small, indicating that OC source (common to all sites) was a more important regulator of OC BE in Lake Kinneret than oxygen exposure or mineral particles characteristics.     

桂东南云开地区变质杂岩锆石SHRIMP U-Pb年代学

对位于华夏古陆东南部的广西云开地区大面积出露的晚前寒武纪变质杂岩中的主体花岗质片麻岩、中深变质的天堂山岩群石榴辉石岩和中浅变质的云开岩群洋中脊型变质基性火山岩(斜长角闪岩)进行了高精度锆石SHRIMP U-Pb定年.获得天堂山岩群石榴辉石岩的形成年龄为1894Ma±17Ma和1847Ma±59Ma,表明其时代为古元古代;云开岩群洋中脊型变质基性火山岩(斜长角闪岩)的喷发年龄为1462Ma±28Ma,证明该地区存在中(-新)元古代的古洋壳残片;获得花岗质片麻岩的侵入年龄为906Ma±24Ma,应为1000Ma前后发生的全球性Grenville期(四堡期)造山作用的产物,并获得2702Ma±13Ma的继承碎屑锆石年龄,这是云开地区乃至华夏古陆目前获得的最古老年龄,证明华夏古陆曾存在新太古代陆壳物质.