Basin-To-Basin and Year-To-Year Variation of Temperature and Salinity Characteristics in the East Sea (Sea of Japan)

Analysis of CTD data from four CREAMS expeditions carried out in summers of 1993–1996 produces distinct T-S relationships for the western and eastern Japan Basin, the Ulleung Basin and the Yamato Basin. T-S characteristics are mainly determined by salinity as it changes its horizontal pattern in three layers, which are divided by isotherms of 5°C and 1°C; upper warm water, intermediate water and deep cold water. Upper warm water is most saline in the Ulleung Basin and the Yamato Basin. Salinity of intermediate water is the highest in the eastern Japan Basin. Deep cold water has the highest salinity in the Japan Basin. T-S curves in the western Japan Basin are characterized by a salinity jump around 1.2–1.4°C in the T-S plane, which was previously found off the east coast of Korea associated with the East Sea Intermediate Water (Cho and Kim, 1994). T-S curves for the Japan Basin undergo a large year-to-year variation for water warmer than 0.6°C, which occupies upper 400 m. It is postulated that the year-to-year variation in the Japan Basin is caused by convective overturning in winter. This revised version was published online in August 2006 with corrections to the Cover Date.     

Preliminary 10Be chronology for the last deglaciation of the western margin of the Greenland Ice Sheet

The now acknowledged thinning of the Greenland Ice Sheet raises concerns about its potential contribution to future sea level rise. In order to appreciate the full extent of its contribution to sea level rise, reconstruction of the ice sheet's most recent last deglaciation could provide key information on the timing and the height of the ice sheet at a time of rapid climate readjustment. We measured ¹⁰Be concentrations in 12 samples collected along longitudinal and altitudinal transects from Sisimiut to within 10 km of the Isunguata Sermia Glacier ice margin on the western coast of Greenland. Along the longitudinal transect, we collected three perched boulders and two bedrocks. In addition, we sampled seven perched boulders along a vertical transect in a valley within 10 km of the Isunguata Sermia Glacier ice margin. Our pilot dataset constrains the height of the ice sheet during the Last Glacial Maximum (LGM) between 500 m and 840 m (including the 120 m relative sea level depression at the time of the LGM, 21 ka BP). From the transect we estimate the thinning of the ice sheet at the end of the deglaciation between 12.3 ± 1.5 ¹⁰Be ka (n = 2) and 8.3 ± 1.2 ¹⁰Be ka (n = 3) to be ～6 cm a^?1 over this time period. Direct dating of the retreat of the western margin of the Greenland Ice Sheet has the potential to better constrain the retreat rate of the ice margin, the thickness of the former ice sheet as well as its response to climate change. Copyright © 2008 John Wiley & Sons, Ltd.     

Adjustment of the electric current in pulsar magnetospheres and origin of subpulse modulation

Stability analysis of agegraphic dark energy in Brans-Dicke theory is presented in this paper. We constrain the model parameters with the observational data and thus the results become broadly consistent with those expected from experiment. Stability analysis of the model without best fitting shows that universe may begin from an unstable state passing a saddle point and finally become stable in future. However, with the best fitted model, There is no saddle intermediate state. The agegraphic dark energy in the model by itself exhibits a phantom behavior. However, contribution of cold dark matter on the effective energy density modifies the state of the universe from phantom phase to quintessence one. The statefinder diagnosis also indicates that the universe leaves an unstable state in the past, passes the LCDM state and finally approaches the sable state in future.     

Viscous Energy Dissipation by Flux Pile-Up Merging in the Solar Corona

Magnetic field annihilation in resistive viscous incompressible plasmas is analyzed. Anisotropic viscous transport is modeled by the dominant terms in the Braginskii viscous stress tensor. An analytical solution for steady-state magnetic merging, driven by vortical plasma flows in two dimensions, is derived. Resistive and viscous energy dissipation rates are calculated. It is shown that, except in the limiting case of zero vorticity, viscous heating can significantly exceed Joule heating at the merging site. The results strongly suggest that viscous dissipation can provide a significant fraction of the total energy release in solar flares, which may have far-reaching implications for flare models.     

Pb isotopic age of the Allende chondrules

Abstract— We have studied Pb‐isotope systematics of chondrules from the oxidized CV3 carbonaceous chondrite Allende. The chondrules contain variably radiogenic Pb with a ²⁰⁶Pb/²⁰⁴Pb ratio between 19.5–268. Pb‐Pb isochron regression for eight most radiogenic analyses yielded the date of 4566.2 ± 2.5 Ma. Internal residue‐leachate isochrons for eight chondrule fractions yielded consistent dates with a weighted average of 4566.6 ± 1.0 Ma, our best estimate for an average age of Allende chondrule formation. This Pb‐Pb age is consistent with the range of model ²⁶Al‐²⁶Mg ages of bulk Allende chondrules reported by Bizzarro et al. (2004) and is indistinguishable from Pb‐Pb ages of Ca‐Al‐rich inclusions (CAIs) from CV chondrites (4567.2 ± 0.6 Ma) (Amelin et al. 2002) and the oldest basaltic meteorites. We infer that chondrule formation started contemporaneously with or shortly after formation of CV CAIs and overlapped in time with formation of the basaltic crust and iron cores of differentiated asteroids. The entire period of chondrule formation lasted from 4566.6 ± 1.0 Ma (Allende) to 4564.7 ± 0.6 Ma (CR chondrite Acfer 059) to 4562.7 ± 0.5 Ma (CB chondrite Gujba) and was either continuous or consisted of at least three discrete episodes. Since chondrules in CB chondrites appear to have formed from a vapor‐melt plume produced by a giant impact between planetary embryos after dust in the protoplanetary disk had largely dissipated (Krot et al. 2005), there were possibly a variety of processes in the early solar system occurring over at least 4–5 Myr that we now combine under the umbrella name of “chondrule formation.”     

Pushbroom-Frame Imagery Co-Registration

More and more littoral surveys are conducted with aerial platform sensor suites that include a hyperspectral pushbroom sensor and a frame camera. However, in some cases, data from auxiliary sensors may contain errors or are not available. For many research groups, a high-accuracy registration of the multi-sensor data relative to each other is essential, while absolute geo-location of each individual measurement is not. A co-registration procedure was developed for pseudo ortho-rectification of the hyperspectral imagery and to remove spatial distortions caused by the aircraft's trajectory during the survey based on a flat-earth assumption. This image-processing approach utilizes the aerial frame imagery as a reference. Each hyperspectral scan line is co-registered into the frame imagery coordinate system. The performance of the procedure was evaluated using hyperspectral imagery collected over northern New Hampshire and southern Maine. The evaluation results showed that the procedure is robust enough to pseudo ortho-rectify hyperspectral imagery over coastal areas and to remove significant spatial distortions.     

Transient electromagnetic modelling of an isolated wire loop over a conductive medium

A large closed wire loop is generally used in field experiments for testing airborne electrical exploration equipment. Thus, methods are required for the precise calculation of an electromagnetic response in the presence of a closed wire loop. We develop a fast and precise scheme for calculating the transient response for such a closed loop laid out at the surface of a horizontally layered conductive ground. Our scheme is based on the relationship between the magnetic flux flowing through a closed loop and the current induced in it. The developed scheme is compared with 2D and 3D finite‐element modelling for several positions of an airborne electromagnetic system flying over a closed loop. We also study the coupling effect between the current flowing in the closed loop and the current flowing in the horizontally layered conductive medium. The result shows that for the central position of the transmitter, the difference between axisymmetrical finite‐element modelling and our scheme is less than 1%. Moreover, for the non‐coaxial transmitter–receiver–loop system, the solution obtained by our scheme is in good agreement with full 3D finite‐element modelling, and our total simulation time is substantially lower: 1 minute versus 120 hours.