Modeling seasonal variations of ocean and sea ice circulation in the Beaufort and Chukchi Seas： A model-data fusion study

A 3.8-kin Coupled Ice-Ocean Model （C1OM） was implemented to successfully reproduce many observed phenomena in the Beaufort and Chukchi seas, including the Bering-inflow-originated coastal current that splits into three branches： Alaska Coastal Water （ACW） , Central Channel, and Herald Valley branches. Other modeled phenomena include the Beaufort Slope Current （BSC） , the Beaufort Gyre, the East Siberian Current （ ESC）, mesoscale eddies, seasonal landfast ice, sea ice ridging, shear, and deformation. Many of these downscaling processes can only be captured by using a high-resolution CIOM, nested in a global climate model. The seasonal cycles for sea ice concentration, thickness, velocity, and other variables are well reproduced with Solid validation by satellite measurements. The seasonal cycles for upper ocean dynamics and thermodynamics are also well reproduced, which include the formation of the cold saline layer due to the injection of salt during sea ice formation, the BSC, and the subsurface upwelling in winter that brings up warm, even more saline Atlantic Water along the shelfbreak and shelf along the Beaufort coast.     

Estimation of heat flux through the eastern Bering Strait

We estimated the northward heat flux through the eastern channel of the Bering Strait during the ice-free seasons between 1999 and 2008. This is likely about half of the total heat flux through the strait. The net volume transport and heat flux through the eastern channel of the strait were estimated from multiple linear regression models with in-situ/satellite remotely sensed datasets and NCEP reanalysis 10 m wind. The net volume transport was well explained by the west-east slope of sea level anomaly and NNW wind component at the strait. On the heat flux, the contributions of both barotropic and baroclinic components were taken into account. Estimated volume transport and vertical profile of temperature were used to calculate northward heat flux through the eastern channel of the strait. The magnitude of the estimated heat flux is comparable to estimates from in-situ measurements. Averaged heat flux in the eastern Bering Strait between 2004 and 2007 was about 1.9 times larger than that between 2000 and 2003. Maximum heat flux occurred in 2004, and same magnitude of heat flux was estimated from 2005 to 2007. This resulted not only from the increase in northward volume transport but also anomalous warm water intrusion from the Bering Sea. Our results suggest a candidate among the important parameters controlling heat budget, which contributes to the Arctic sea ice reduction, whereas more studies are required to confirm that this mechanism is actually responsible for the interannual and longer timescale variability.     

Statistical Approach for Classification of Dinosaur Eggs from the Heyuan Basin at the Northeast of Guangdong Province

The Zhutian and Dafeng formations (Upper Cretaceous) of the Heyuan Basin in northeastern Guangdong Province, China, have produced thousands of dinosaur eggs. Macromorphological features (egg diameter, egg shape, outer surface texture, and shell thickness) of 461 eggs were analyzed using non-destructive techniques and subjected to statistical analyses in order to assess their diversity and taxonomic affinities. Three types (1, 2 and 3) of eggs were discerned based on shape and outer surface morphology. Type 1 eggs are spherical to ellipsoidal in shape and have a rough surface. Three subtypes (Type 1-A-1, 1-A-2, and 1-B) are apparent from scatter plots and cluster analyses of egg diameters and shell thickness. Type 2 eggs are elongate with linear ornamentation on the surface, and are comparable to eggs that belong to the oofamily Elongatoolithidae. Type 3 eggs are elongate with a smooth surface, and are assigned to the oofamily Prismatoolithidae. Macromorphological features of the various egg types suggest that Type 1 could have been laid by ornithischian, sauropod or therizinosaur dinosaurs, Type 2 by oviraptorids, and Type 3 by troodontids. This study represents the first comprehensive statistical analysis of macrofeatures of dinosaur eggs, and reveals taxonomic diversity in the dinosaurs that were laying eggs in the Upper Cretaceous Heyuan area heretofore unrecognized in skeletal remains.     

TM classification using local spectral variability

A classification method which takes into account not only spectral but also spatial features for LANDSAT‐4 and 5 Thematic Mapper (TM) data is proposed. In accordance with improvement of Instantaneous Field of View (IFOV), spatial information such as textural, contextual, etc. is also increased so that some treatments of such information is highly required. One of the simplest spatial features is local spectral variability such as standard deviation, variability constant, variance, etc. in small cells such as 2x2,3x3 pixels. Such information can be used together with conventional spectral features in an unified way, for the traditional classifier such as a pixel‐wise Maximum Likelihood Decision Rule (MLDR). From the experiments, there was a substantial improvement in overall classification accuracy for TM forestry data. The probability of correct classification (PCC) for the new clearcut and the alpine meadow classes increased by 7% to 97% correct. The confusion between alpine meadow and new clearcut was reduced from 9% to 3%.     

Photometric observations of 107P/Wilson-Harrington

We present lightcurve observations and multiband photometry for 107P/Wilson-Harrington using five small- and medium-sized telescopes. The lightcurve has shown a periodicity of 0.2979 day (7.15 h) and 0.0993 day (2.38 h), which has a commensurability of 3:1. The physical properties of the lightcurve indicate two models: (1) 107P/Wilson-Harrington is a tumbling object with a sidereal rotation period of 0.2979 day and a precession period of 0.0993 day. The shape has a long axis mode (LAM) of L₁:L₂:L₃ = 1.0:1.0:1.6. The direction of the total rotational angular momentum is around λ = 310°, β = −10°, or λ = 132°, β = −17°. The nutation angle is approximately constant at 65°. (2) 107P/Wilson-Harrington is not a tumbler. The sidereal rotation period is 0.2979 day. The shape is nearly spherical but slightly hexagonal with a short axis mode (SAM) of L₁:L₂:L₃ = 1.5:1.5:1.0. The pole orientation is around λ = 330°, β = −27°. In addition, the model includes the possibility of binary hosting. For both models, the sense of rotation is retrograde. Furthermore, multiband photometry indicates that the taxonomy class of 107P/Wilson-Harrington is C-type. No clear rotational color variations are confirmed on the surface.     

Variation of volatile concentration in a magma system of Satsuma-Iwojima volcano deduced from melt inclusion analyses

Chemical analyses of 30 melt inclusions from Satsuma-Iwojima volcano, Japan, were carried out to investigate volatile evolution in a magma chamber beneath the volcano from about 6300 yr BP to the present. Large variations in volatile concentrations of melts were observed. (1) Water concentration of rhyolitic melts decreases with time; 3–4.6 wt.% at the time of latest caldera-forming eruption of Takeshima pyroclastic flow deposit (ca. 6300 yr BP), 3 wt.% for small pyroclastic flow (ca. 1300 yr BP) of Iwodake, post-caldera rhyolitic dome, and 0.7–1.4 wt.% for submarine lava eruption (Showa-Iwojima) in 1934. (2) Rhyolitic melts of the Takeshima and Iwodake eruptions contained CO₂ of less than 40 ppm, while the Showa-Iwojima melt has higher CO₂ concentration of up to 140 ppm. (3) Water and CO₂ concentrations of basaltic to andesitic melt of Inamuradake, a post-caldera basaltic scoria cone, are 1.2–2.8 wt.% and ≤290 ppm, respectively.Volatile evolution in the magma chamber is interpreted as follows: (1) the rhyolitic magma at the time of the latest caldera-forming eruption (ca. 6300 yr BP) was gas-saturated due to pressure variation in the magma chamber because the large variation in water concentration of the melt was attributed to exsolution of volatile in the magma prior to the eruption. Iwodake eruption (ca. 1300 yr BP) was caused by a remnant of the caldera-forming rhyolitic magma, suggested from the similarity of major element composition between these magmas. (2) Volatile composition of the Showa-Iwojima rhyolitic melt agrees with that of magmatic gases presently discharging from a summit of Iwodake, indicating the low pressure degassing condition. (3) The degassing of the magma chamber by magma convection in a conduit of Iwodake during non-eruptive but active degassing period for longer than 800 years decreased water concentration of the rhyolitic magma. (4) Geological and petrological observations indicate that a stratified magma chamber, which consists of a lower basaltic layer and an upper rhyolitic layer, might have existed during the post-caldera stage. Addition of CO₂ from the underlying basaltic magma to the upper gas-undersaturated (degassed) rhyolitic magma increased CO₂ concentration of the rhyolitic magma.     

Evaluation of Vector Winds Observed by NSCAT in the Seas around Japan

In order to validate wind vectors derived from the NASA Scatterometer (NSCAT), two NSCAT wind products of different spatial resolutions are compared with observations by buoys and research vessels in the seas around Japan. In general, the NSCAT winds agree well with the wind data from the buoys and vessels. It is shown that the root-mean-square (rms) difference between NSCAT-derived wind speeds and the buoy observations is 1.7 ms^–1, which satisfies the mission requirement of accuracy, 2 ms^–1. However, the rms difference of wind directions is slightly larger than the mission requirement, 20°. This result does not agree with those of previous studies on validation of the NSCAT-derived wind vectors using buoy observations, and is considered to be due to differences in the buoy observation systems. It is also shown that there are no significant systematic trends of the NSCAT wind speed and direction depending on the wind speed and incidence angle. Comparison with ship winds shows that the NSCAT wind speeds are lower than those observed by the research vessels by about 0.7 ms^–1 and this bias is twice as large for data observed by moving ships than by stationary ships. This result suggests that the ship winds may be influenced by errors caused by ship's motion, such as pitching and rolling.     

Near-infrared spectrophotometry of Asteroid 25143 Itokawa from NIRS on the Hayabusa spacecraft

A photometric analysis of the S-type Asteroid 25143 Itokawa is performed over multiple wavelengths ranging from 0.85 to 2.10 μm based on disk-resolved reflectance spectra obtained with the Hayabusa near-infrared spectrometer (NIRS). We derive the global photometric properties of Itokawa in terms of Hapke's photometric model. We find that Itokawa has a single-scatter albedo that is 35-40% less than that of Asteroid 433 Eros. Itokawa also has a single-particle phase function that is more strongly back-scattering than that of Eros. Despite its hummocky surface strewn with large boulders, Itokawa exhibits an opposition effect. However, the total amplitude of the opposition surge for Itokawa was estimated to be less than unity while Eros and other S-type asteroids have been found to have model values exceeding unity. The wavelength dependence of the opposition surge width reveals that coherent backscatter contributes to the opposition effect on Itokawa's surface. The photometric roughness of Itokawa is well constrained to a value of 26° ± 1° which is similar to Eros, suggesting that photometric roughness models the smallest surface roughness scale for which shadows exist.