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1.
The tropospheric zenith total delay (ZTD) derived from very long baseline interferometry (VLBI) is an important parameter of the atmosphere, reflecting various atmosphere-related processes and variations. In this paper, ZTD time series of the IVS rapid combined tropospheric product (2002–2006) with a 1-h resolution are used for the first time to investigate the diurnal and semidiurnal oscillations. Significant diurnal and semidiurnal variations of ZTD are found at all VLBI stations. The amplitude of the diurnal cycle S1 is 0.6–1.2 mm at most of the VLBI stations, and the amplitude of the semidiurnal cycle S2 is 0.2–1.9 mm, which nearly accord with the surface pressure tides S1/S2 and co-located GPS estimated S1/S2. The results indicate that the S1 and S2 behaviors are mainly dominated by the hydrostatic component, namely pressure tides. In general, the semidiurnal S2 amplitudes are slightly larger than the diurnal S1. While S1 shows no clear dependency on site altitude, S2 has a regular distribution with VLBI site altitude. The results are in accordance with predictions of the classic tidal theory [Chapman, S., Lindzen, R.S., 1970. Atmospheric Tides, Gordon and Breach, New York].  相似文献   

2.
An analysis of the climate change signal for seasonal temperature and precipitation over the Northern Adriatic region is presented here. We collected 43 regional climate simulations covering the target area, including experiments produced in the context of the PRUDENCE and ENSEMBLES projects, and additional experiments produced by the Swedish Meteorological and Hydrological Institute. The ability of the models to simulate the present climate in terms of mean and interannual variability is discussed and the insufficient reproduction of some features, such as the intensity of summer precipitation, are shown. The contribution to the variance associated with the intermodel spread is computed. The changes of mean and interannual variability are analyzed for the period 2071–2100 in the PRUDENCE runs (A2 scenario) and the periods 2021–2050 and 2071–2100 (A1B scenario) for the other runs. Ensemble results show a major warming at the end of the 21st century. Warming will be larger in the A2 scenario (about 5.5 K in summer and 4 K in winter) than in the A1B. Precipitation is projected to increase in winter and decrease in summer by 20% (+0.5 mm/day and −1 mm/day over the Alps, respectively). The climate change signal for scenario A1B in the period 2021–2050 is significant for temperature, but not yet for precipitation. In summer, interannual variability is projected to increase for temperature and for precipitation. Winter interannual variability change is different among scenarios. A reduction of precipitation is found for A2, while for A1B a reduction of temperature interannual variability is observed.  相似文献   

3.
Semidiurnal tidal features have been examined in the Mesosphere and Lower Thermosphere (MLT) from the long-term (2002–2007) meteor wind data over Maui (20.75°N, 156.43°W). Amplitude and phase obtained from the harmonic analysis exhibit large day to day variability. Mean amplitude obtained from the monthly mean data over the observation period is found to vary within ～8–28 m/s and 10–32 m/s for the zonal and meridional winds, respectively. The amplitude has revealed clear semiannual oscillation (SAO) pattern with maxima during solstices and altitudinal growth in both wind components. Significant resemblance in its variability with other observations carried out from the low latitude sites all over the globe is obtained. Vertical wavelength estimated from the phase gradients exposes large values (>90 km) in all seasons. Contribution of the semidiurnal tide to the total tidal variability in the MLT is found to vary over wide range throughout the year with generally higher influence during winter season over diurnal and terdiurnal components.  相似文献   

4.
Both coastal and global mean sea level rise by about 3.0 ± 0.5 mm/year from January 1993 to December 2004. Over shorter intervals the coastal sea level rises faster and over longer intervals slowly than the global mean, which trend is almost constant for each interval and is equal to 2.9 ± 0.5 mm/year in 1993–2008. The different trends are due to the higher interannual variability of coastal sea level, caused by the sea level regional variability, that is further averaged out when computing the global mean.Coastal sea level rise is well represented by a selected set of 267 stations of the Permanent Service for Mean Sea Level and by the corresponding co-located altimeter points. Its departure from coastal sea level computed from satellite altimetry in a 150 km distance from coast, dominated by a large rise in the Eastern Pacific, is due to the regional interannual variability.Regionally the trends of the coastal and open-ocean sea level variability are in good agreement and the main world basins have a positive averaged trend. The interannual variability is highly correlated with the El Nino Southern Oscillation (SO) and the North Atlantic Oscillation (NAO) climatic indices over both the altimeter period and the interval 1950–2001. Being the signal of large scale a small number of stations with good spatial coverage is needed. The reconstruction of the interannual variability using the spatial pattern from altimetry and the temporal patterns from tide gauges correlated to NAO and SOI restitutes about 50% of the observed interannual variability over 1993–2001.  相似文献   

5.
Seasonal variations in the auroral E-region neutral wind for different solar activity periods are studied. This work is based on neutral wind data obtained over 56 days between 95–119 km altitude under geomagnetic quiet conditions (Ap<16) during one solar cycle by the European Incoherent Scatter radar located in northern Scandinavia. In general, the meridional mean wind shifts northward, and the zonal mean wind increases in eastward amplitude from winter to summer. The zonal mean wind blows eastward in the middle and lower E-region for each season and for each solar condition except for the equinox, where the zonal mean wind blows westward at and below 104 km. Solar activity dependence of the mean wind exists during the winter and equinox seasons, while in summer it is less prominent. Under high solar activity conditions, the altitude profiles of the horizontal mean winds in winter and the equinoxes tend to resemble those in summer. The horizontal diurnal tide is less sensitive to solar activity except during summer when the meridional amplitude increases by ∼10 m s−1 and the corresponding phase shifts to a later time period (1–2 h) during high solar activity. Seasonal dependence of the semidiurnal tide is complex, but is found to vary with solar activity. Under low solar activity conditions the horizontal semidiurnal amplitude shows seasonal dependence except at upper E-region heights, while under high solar activity conditions it becomes less sensitive to seasonal effects (except for the meridional component above 107 km). Comparisons of mean winds with LF and UARS observations are made, and the driving forces for the horizontal mean winds are discussed for various conditions.  相似文献   

6.
《Continental Shelf Research》2005,25(9):1081-1095
The mesoscale distribution and seasonal variation of the size structure of phytoplankton biomass, as measured by chlorophyll a (chl a), was studied in the Ebro shelf area (NW Mediterranean) during three different seasons: autumn, winter and summer. In autumn and summer, when the water column was, respectively, slightly or strongly stratified and nutrient concentrations were low at surface, average total chl a values were 0.31 and 0.29 mg m−3, respectively. In winter, the intrusion of nutrients into the photic zone by intense vertical mixing and strong riverine inputs, produced an increase of the total autotrophic biomass (0.76 mg m−3). In the three seasons, the main contributor to total chl a was the picoplanktonic (<2 μm) size fraction (42% in winter and around 60% in autumn and summer). The nanophytoplankton (2–20 μm) contribution to total chl a showed the lowest variability amongst seasons (between 29% and 39%). The microplanktonic (>20 μm) chl a size fraction was higher in winter (27%) than in the other seasons (less than 13%). The maximum total chl a concentrations were found at surface in winter, at depths of 40 m in autumn and between 50 and 80 m in summer. The relative contribution of the <2 μm size fraction at these levels of the water column tended to be higher than at other depths in autumn and winter and lower in summer. In autumn and winter, nutrient inputs from Ebro river discharge and mixing processes resulted in an increase on the >2 μm contribution to total chl a in the coastal zone near the Ebro Delta area. In summer, the contribution of the <2 and >2 μm chl a size fractions was homogeneously distributed through the sampling area. In autumn and summer, when deep chl a maxima were observed, the total amount of the autotrophic biomass in the superficial waters (down to 10 m) of most offshore stations was less than 10% of the whole integrated chl a (down to 100 m or to the bottom). In winter, this percentage increased until 20% or 40%. The >2 μm chl a increased linearly with total chl a values. However, the <2 μm chl a showed a similar linear relationship only at total chl a values lower than 1 mg m−3 (in autumn and summer) or 2 mg m−3 (winter). At higher values of total chl a, the contribution of the <2 μm size fraction remained below an upper limit of roughly 0.5 mg m−3. Our results indicate that the picoplankton fraction of phytoplankton may show higher seasonal and mesoscale variability than is usually acknowledged.  相似文献   

7.
Two accurately calibrated superconducting gravimeters (SGs) provide high quality tidal gravity records in three central European stations: C025 in Vienna and at Conrad observatory (A) and OSG050 in Pecný (CZ). To correct the tidal gravity factors from ocean loading effects we compared the load vectors from different ocean tides models (OTMs) computed with different software: OLFG/OLMP by the Free Ocean Tides Loading Provider (FLP), ICET and NLOADF. Even with the recent OTMs the mass conservation is critical but the methods used to correct the mass imbalance agree within 0.1 nm/s2. Although the different software agrees, FLP probably provides more accurate computations as this software has been optimised. For our final computation we used the mean load vector computed by FLP for 8 OTMs (CSR4, NAO99, GOT00, TPX07, FES04, DTU10, EOT11a and HAMTIDE). The corrected tidal factors of the 3 stations agree better than 0.04% in amplitude and 0.02° in phase. Considering the weighted mean of the three stations we get for O1 δc = 1.1535 ± 0.0001, for K1 δc = 1.1352 ± 0.0003 and for M2 δc = 1.1621 ± 0.0003. These values confirm previous ones obtained with 16 European stations. The theoretical body tides model DDW99/NH provides the best agreement for M2 (1.1620) and MATH01/NH for O1 (1.1540) and K1 (1.1350). The largest discrepancy is for O1 (0.05%). The corrected phase αc does not differ significantly from zero except for K1 and S2. The calibrations of the two SG's are consistent within 0.025% and agree with Strasbourg results within 0.05%.  相似文献   

8.
《Marine pollution bulletin》2009,58(6-12):632-636
The intertidal copeopod Tigriopus japonicus, which is abundant and widely distributed along the coasts of Western Pacific, has been suggested to be a good marine ecotoxicity testing organism. In this study, a series of experiments were conducted to investigate the reproducibility and variability of copper (Cu) sensitivity of T. japonicus so as to evaluate its potential to serve as an appropriate test species. To understand the seasonal variation of Cu sensitivity, individuals of T. japonicus were collected from the field in summer and winter, and subjected to standard 96 h acute (static renewal) toxicity tests. 96 h-LC50 values of T. japonicus collected from the two seasons were marginally different (p = 0.05), with an overall coefficient of variation (CV) of 33%. Most importantly, our results indicated that chronic Cu sensitivity of T. japonicus was highly reproducible. The CVs of intrinsic rates of increase in the population of the control and Cu treatment (10 μg Cu l−1) groups were only 10–11% between 10 runs of a standardised complete life-cycle test. Moreover, different Cu(II) salts generally resulted in a similar 96 h-LC50 value while Cu(I) chloride was consistently slightly less toxic than Cu(II) salts. Given such a high reproducibility of toxic responses, it is advocated to use T. japonicus as a routine testing organism.  相似文献   

9.
Horizontal winds in the mesosphere and lower thermosphere over the Antarctic have been measured by a meteor radar at Rothera (67.5°S, 68.0°W) and MF radar at Davis (68.6°S, 78.0°E). Data from Rothera recorded over a 20-month interval in 2005–2006 and data from Davis recorded over the 13-year interval 1994–2006 are examined to investigate the monthly mean behaviour of the lunar semidiurnal tide. Both data sets show a clear signal of the 12.42-h lunar semidiurnal (M2) tide. The amplitude reaches values as large as 8 m s−1. The vertical wavelengths of the tide vary seasonally from 10 to 65 km. Comparisons of the phase of the tide measured over the two sites reveals that it does not purely consist of a migrating wavenumber 2 mode. This suggests that other, non-migrating, modes are likely to be present.  相似文献   

10.
The paper is focused on the global spatial structure, seasonal and interannual variability of the ～5-day Rossby (W1) and ～6-day Kelvin (E1) waves derived from the SABER/TIMED temperature measurements for 6 full years (January 2002–December 2007). The latitude structure of the ～5-day W1 wave is related to the gravest symmetric wave number 1 Rossby wave. The vertical structure of the ～5-day Rossby wave amplitude consists of double-peaked maxima centred at ～80–90 km and ～105–110 km. This wave has a vertically propagating phase structure from the stratosphere up to 120 km altitude with a mean vertical wavelength of ～50–60 km. The ～6-day E1 wave is an equatorially trapped wave symmetric about the equator and located between 20°N and 20°S. Its seasonal behaviour indicates some equinoctial and June solstice amplifications, while the vertical phase structure indicates that this is a vertically propagating wave between 20–100 km altitudes with a mean vertical wavelength of ～25 km.  相似文献   

11.
The mass-induced sea level variability and the net mass transport between Mediterranean Sea and Black Sea are derived for the interval between August 2002 and July 2008 from satellite-based observations and from model data. We construct in each basin two time series representing the basin mean mass signal in terms of equivalent water height. The first series is obtained from steric-corrected altimetry while the other is deduced from GRACE data corrected for the contamination by continental hydrology. The series show a good agreement in terms of annual and inter-annual signals, which is in line with earlier works, although different model corrections influence the consistency in terms of seasonal signal and trend.In the Mediterranean Sea, we obtain the best agreement using a steric correction from the regional oceanographic model MFSTEP and a continental hydrological leakage correction derived from the global continental hydrological model WaterGAP2. The inter-annual time series show a correlation of 0.85 and a root mean square (RMS) difference of 15 mm. The two estimates have similar accuracy and their annual amplitude and phase agree within 3 mm and 23 days respectively. The GRACE-derived mass-induced sea level variability yields an annual amplitude of 27 ± 5 mm peaking in December and a trend of 5.3 ± 1.9 mm/yr, which deviates within 3 mm/yr from the altimetry-derived estimate.In the Black Sea, the series are less consistent, with lower accuracy of the GRACE-derived estimate, but still show a promising agreement considering the smaller size of the basin. The best agreement is realized choosing the corrections from WaterGAP2 and from the regional oceanographic model NEMO. The inter-annual time series have a correlation and RMS differences of 0.68 and 55 mm, their annual amplitude and phase agree within 4 mm and 6 days respectively. The GRACE-derived seawater mass signal has an annual amplitude of 32 ± 4 mm peaking in April. On inter-annual time scales, the mass-induced sea level variability is stronger than in the Mediterranean Sea, with an increase from 2003 to 2005 followed by a decrease from 2006 to 2008.Based on mass conservation, the mass-induced sea level variations, river runoff and precipitation minus evaporation are combined to derive the strait flows between the basins and with the Atlantic Ocean. At the Gibraltar strait, the net inflow varies annually with an amplitude of 52 ± 10 × 10−3 Sv peaking end of September (1 Sv = 106 m3 s−1). The inflow through the Bosphorus strait displays an annual amplitude of 13 ± 3 ×10−3 Sv peaking in the middle of March. Additionally, an increase of the Gibraltar net inflow (3.4 ± 0.8 × 10−3 Sv/yr) is detected.  相似文献   

12.
Observations are presented of large-amplitude internal waves (LAIWs) generated by the steepening of the internal tide on the Australian North West Shelf (NWS) over a 4-month period extending from strongly stratified summer conditions to weakly stratified winter conditions. The observations are from a site in water depth of 124 m where current and temperature measurements were made from a fixed vertical mooring and a benthic L-shaped spatial array. The observations show the LAIWs at this site to be characterized by strong seasonal variability, with energetic LAIWs of depression being dominant during summer and weaker LAIWs of elevation being dominant during the winter months as the stratification weakens, the upper mixed layer deepens, and the thermocline is close to the bottom. Waves were also seen to propagate from a range of directions towards the observation site. Modeling using the Regional Ocean Modeling System (ROMS v2.1) revealed that internal tide generation in the area occurred at water depths of between 400 and 600 m along an arc of approximately 120 km in length, some 70 km to the northwest of our experimental site. The results demonstrate both the 3D nature as well as the seasonal variation of the LAIW field.  相似文献   

13.
Most rivers in Italy are segmented by dams that need rehabilitation because of (1) safety requirements by increasingly risk-averse societies, (2) changes in the downstream river and riparian system after dams building, (3) poor initial design at the time of completion and (4) modified priorities of watershed management. Safe design of flood spillways is a major concern, and requires to cope with low frequency flood hazard. One must estimate flood figures with high return periods (R ⩾ 1000–10,000 years) but statistical methods involve large uncertainties because of the short length of the available records. This paper investigates the return period of the design flood of existing spillways RS of large dams in Italy. We used re-normalized flood frequency approach and regionalization using the Generalized Extreme Value distribution. The estimation of the site specific index flood is carried out by simple scaling with basin area at the regional level. The result show that 55% (245) of the 448 examined dams are equipped by spillway with RS > 10,000; and 71% (315) of the dams have RS > 1000. Conversely, 29% (130) of the dams display RS < 1000 years, lower than acceptable hazard. The spillway of 14% (62) of the dams has RS < 100 years, indicating potential exceedance of spillways capacity. Reservoir routing may dampen the outflow hydrograph, but one should carefully account for the need of achieving accurate dam safety assessment of these dams based on site specific investigations, also accounting for global change forcing.  相似文献   

14.
The seasonal cycle of chlorophyll concentration in the Bay of Biscay and western English Channel has been examined using satellite data (chlorophyll, sea surface temperature (SST), photosynthetically available radiation (PAR) and wind) along the line of the ferry Pride of Bilbao (Bilbao to Portsmouth). The spring phytoplankton bloom develops regularly in the oceanic region of the Bay of Biscay from mid March to the beginning of May with peak chlorophyll concentrations ranging 2–4 mg m?3. Low wind turbulence is a major factor allowing the development of productivity pulses in the Bay of Biscay during spring. Exceptional blooms of phytoplankton take place in summer (July–August) in the western English Channel with chlorophyll concentrations as high as 40 mg m?3. Some environmental factors (SST, wind, pressure and tide) are examined. Autumn blooms of phytoplankton (1–2 mg m?3) are also detected in the northern Bay of Biscay, shelf-break and Celtic Sea in October. A 11 years pluri-annual synthesis of SeaWiFS satellite measurements is presented.  相似文献   

15.
《Journal of Geodynamics》2010,49(3-5):253-259
We observe the Earth tidal fields at diurnal and semi-diurnal periods using Kinematic Precise Point Positioning (KPPP) GPS analysis. Our KPPP GPS solutions compare well with super-conducting gravimeter (SG) observations and a theoretical Earth tidal model, that includes both ocean tide loading model and body tides. We make a high resolution map of the observed Earth tidal response fields using the Japanese GEONET GPS network which consists of 1200 sites. We find that: (1) the average phase of GPS data lags 0.11 ± 0.04° from our theoretical Earth tidal model, (2) the average amplitude ratio between GPS and the theoretical Earth tidal model is 1.007 ± 0.003, (3) the amplitude in the Kyushu district is about 1.0–1.5 ± 0.3% larger than in the Hokkaido district, and (4) the amplitude at the Japan Sea side is about 0.5 ± 0.2% larger than that at the Pacific Ocean side. These results suggest that we may be able to place constraints on Earth structure using GPS-derived tidal information.  相似文献   

16.
Outcrops of the Cretaceous Upper sandstone formation some 375 km to the East of Addis Ababa on the motor Highway to Harar was paleomagnetically investigated. About seventy core samples were collected at various stratigraphic levels from 250–300 meters thick sedimentary formation. After standard sample preparations in the laboratory the resulting specimens were subjected to routine paleomagnetic demagnetization protocol. In the first steps of demagnetizations process the recent and viscous magnetizations were removed by heating until a temperature of level of 300 °C. Further demagnetization of the samples resulted in the isolation of the final magnetization with stable line segments that is directed towards the origin, which is interpreted as Characteristic Remanent Magnetization (ChRM). Rock – magnetic experiments have identified goethite (αFeOOH), hematite (αFe2O3), detritial hematite, and magnetite as the magnetic mineral phases carrying the remanence. The ChRM identified resulted in an average value of (Ds = 0.5°, Is = ?0.7°, α95 = 4.3°, N = 34) for the red sandstones while an average value of (Ds = 335.8°, Is = ?31.8°, α95 = 4.7°, N = 14) for the limestone intercalations. The former ChRM in the red sandstone is determined to be secondary while the latter ChRM is known to be primary. Comparison of these directional results and their pole equivalents with the African plate Apparent Polar Wander Path curve established by Besse and Courtillot (2003) give ages of between 115–130 Million years for the limestone intercalation and ages of 30 million years for red sandstone unit. These are interpreted respectively as estimates of the age of deposition and a later remagnetization respectively.  相似文献   

17.
The elastic moduli of polycrystalline ringwoodite, (Mg0.91Fe0.09)2SiO4, were measured up to 470 K by means of the resonant sphere technique. The adiabatic bulk (KS) and shear (μ) moduli were found to be 185.1(2) and 118.22(6) GPa at room temperature, and the average slopes of dKS/dT and dμ/dT in the temperature range of the study were determined to be −0.0193(9) and −0.0148(3) GPa/K, respectively. Using these results, we estimate seismic wave velocity jumps for a pure olivine mantle model at 520 km depth. We find that the jump for the S-wave velocity is about 1.5 times larger than that for the P-wave velocity at this depth. This suggests that velocity jumps at the 520 km discontinuity are easier to detect using S-waves than P-waves.  相似文献   

18.
Biomonitoring methods based on macrophytes have been used mandatorily in the assessment of freshwaters since the implementation of the Water Framework Directive (WFD). The Macrophyte Index for Rivers (MIR) was developed in Poland for the monitoring of running waters under the WFD requirements. This index shows the degree of river degradation under the influence of water pollutants, especially nutrients. The aim of the present study was to determine the relationship between the MIR and various hydrochemical parameters using artificial neural networks (ANNs). Physico-chemical parameters of water (monthly results for the whole year), which were derived from 147 lowland river survey sites, all located in Poland, were applied to model the MIR values. Water quality variables were determined over three timeframes: the annual average; the average for the vegetation period; and the average for the summer period. Quality of the networks was assessed using coefficient of determination (R2), Nash-Sutcliffe efficiency (NSE) and root mean square error (RMSE). The best modeling quality was obtained for yearly average values of water quality parameters. The quality statistics were: R2 = 0.722, NSE = 0.721 and RMSE = 0.056 (training dataset); R2 = 0.555, NSE = 0.533 and RMSE = 0.101 (validation dataset); R2 = 0.650. NSE = 0.600 and RMSE = 0.089 (testing dataset). This indicates that macrophytes reflect the whole year impact of pollution, whereas summer.  相似文献   

19.
A fine grid tidal modeling experiment is carried out in order to investigate the tidal regimes for major five tidal constituents, the nonlinear tidal phenomena in terms of M4 and MS4 generation, and the independent tide by the tide generating force in the Yellow and East China Seas (YECS). In this study a two-dimensional numerical model based upon a subgrid-scale (SGS) stress modeling technique is used with the tide generating force included. The model was validated with recently observed tide and current data. The calculated tidal charts for tidal elevation show a generally good agreement with existing ones, with more accurate feature of the M2 cotidal chart in comparison with both the observed data and the existing tidal charts. A careful comparison of the computed diurnal amplitude with observations suggests that the diurnal constituents seem to be overdamped especially in the Kyunggi Bay region, for the case when quadratic bottom friction law is used.Propagation features of the M4(MS4) tides are discussed in the YECS, based upon the analyses of the observed and calculated results. The amphidromic system of the M4 is quite complicated and one noticeable characteristic is that the propagation direction of the M4 tidal wave along the west coast of Korean peninsula is opposite to that of the M2 tidal wave. This result coincides with observations. The propagation feature of the MS4 is almost similar to that of the M4, but with lesser amplitude. The responses of the M4 tidal features to momentum diffusion term and depth-dependent form of the friction coefficient are also discussed.It is also shown that when the independent tide (Defant, 1960) arising from tide generating force (TGF) coexists with tidal waves (co-oscillating tide) arising from external boundary forcing, the TGF tidal waves are dissipated and their amphidromes tend to move westward. This may be interpreted as a process whereby the incident and reflected TGF tidal waves are damped by co-oscillating tide arising from external force at open boundaries. The TGF amplitude is found to be up to 10 cm and 4 cm in the Kyunggi Bay for the M2 and S2 constituents while those for all diurnal constituents are less than 1 cm over the entire model domain.  相似文献   

20.
New Late Cretaceous paleomagnetic results from the Okhotsk-Chukotka Volcanic Belt in the Kolyma-Omolon Composite Terrane yield stable and consistent remanent directions. The Late Cretaceous (86–81 Ma) ignimbrites from the Kholchan and Ola suites were sampled at 19 sites in the Magadan area (60.4° N, 151.0° E). We isolated the characteristic paleomagnetic directions from 16 sampled sites using an alternating field demagnetization procedure. The primary nature of these directions is ascertained by dual polarities and positive fold tests. A tilt-corrected mean direction (D = 42.8°, I = 84.7°, k = 46.0, α95 = 10.0°) yields a paleomagnetic pole of 66.7° N, 168.5° E (A95 = 18.8°) which appears almost identical to the 90–67 Ma pole reported from the Lake El’gygytgyn area of the Okhotsk-Chukotka Volcanic Belt (Chukotka Terrane). This consistency suggests that the Kolyma-Omolon Composite Terrane and Chukotka Terrane has acted as a single tectonic unit since 80 Ma without any significant internal deformation. Accordingly, we calculate a combined 80 Ma characteristic paleomagnetic pole (Long. = 164.7° E, Lat. = 68.0°, A95 = 10.9°, N = 12) for the Kolyma-Omolon-Chukotka Block which falls 16.5–17.5° south of the same age poles from Europe and East Asia. We ascribe this discrepancy in pole positions to tectonic activity in the area and infer a southward displacement of 1640 ± 1380 km for the Kolyma-Omolon-Chukotka Block with respect to the North American and Eurasian blocks since 80 Ma; more than 260 km of it is attributed to tectonic displacement in the Arctic Ocean due to the opening of the Canadian Basin.  相似文献   

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