Spatial Variability of Living Coccolithophore Distribution in the Western Subarctic Pacific and Western Bering Sea

Vertical distributions of coccolithophores were observed in the depth range 0–50 m in the western subarctic Pacific and western Bering Sea in summer, 1997. Thirty-five species of coccolithophores were collected. Overall, Emiliania huxleyi var. huxleyi was the most abundant taxon, accounting for 82.8% of all coccolithophores, although it was less abundant in the western Bering Sea. Maximum abundance of this species was found in an area south of 41°N and east of 175°E (Transition Zone) reaching >10,000 cells L⁻¹ in the water column. In addition to this species, Coccolithus pelagicus f. pelagicus, which accounted for 4.2% of the assemblage, was representative of the coccolithophore standing crop in the western part of the subarctic Pacific. Coccolithus pelagicus f. hyalinus was relatively abundant in the Bering Sea, accounting for 2.6% of the assemblage. Coccolithophore standing crops in the top 50 m were high south of 41°N (>241 × 10⁶ cells m⁻²) and east of 170°E (542 × 10⁶ cells m⁻²) where temperatures were higher than 12°C and salinities were greater than 34.2. The lowest standing crop was observed in the Bering Sea and Oyashio areas where temperatures were lower than 6–10°C and salinities were less than 33.0. From the coccolithophore volumes, the calcite stocks in the Transition, Subarctic, and the Bering Sea regions were estimated to be 73.0, 9.7, and 6.9 mg m⁻², respectively, corresponding to calcite fluxes of 3.6, 0.5, and 0.3 mg m⁻²d⁻¹ using Stoke's Law. This revised version was published online in July 2006 with corrections to the Cover Date.     

Obliquity variations of terrestrial planets in habitable zones

We have investigated obliquity variations of possible terrestrial planets in habitable zones (HZs) perturbed by a giant planet(s) in extrasolar planetary systems. All the extrasolar planets so far discovered are inferred to be jovian-type gas giants. However, terrestrial planets could also exist in extrasolar planetary systems. In order for life, in particular for land-based life, to evolve and survive on a possible terrestrial planet in an HZ, small obliquity variations of the planet may be required in addition to its orbital stability, because large obliquity variations would cause significant climate change. It is known that large obliquity variations are caused by spin-orbit resonances where the precession frequency of the planet's spin nearly coincides with one of the precession frequencies of the ascending node of the planet's orbit. Using analytical expressions, we evaluated the obliquity variations of terrestrial planets with prograde spins in HZs. We found that the obliquity of terrestrial planets suffers large variations when the giant planet's orbit is separated by several Hill radii from an edge of the HZ, in which the orbits of the terrestrial planets in the HZ are marginally stable. Applying these results to the known extrasolar planetary systems, we found that about half of these systems can have terrestrial planets with small obliquity variations (smaller than 10°) over their entire HZs. However, the systems with both small obliquity variations and stable orbits in their HZs are only 1/5 of known systems. Most such systems are comprised of short-period giant planets. If additional planets are found in the known planetary systems, they generally tend to enhance the obliquity variations. On the other hand, if a large/close satellite exists, it significantly enhances the precession rate of the spin axis of a terrestrial planet and is likely to reduce the obliquity variations of the planet. Moreover, if a terrestrial planet is in a retrograde spin state, the spin-orbit resonance does not occur. Retrograde spin, or a large/close satellite might be essential for land-based life to survive on a terrestrial planet in an HZ.     

Mid- and far-infrared extinction coefficients of hydrous silicate minerals

Extinction coefficients were measured for three kind of hydrous silicate minerals, montmorillonite, chlorite and serpentine, from 7 to 140 m. The infrared extinction coefficients of these minerals show (1) a few broad bands in the mid-infrared region and (2) a less steep wavelength-dependence in the far-infrared region, in contrast to those of high-temperature magnesium silicates. In the far-infrared region, montmorillonite shows a ^–0.8±0.1 dependence (, the wavelength) without any band structure, chlorite has a double maxima structure around 80 m, and serpentine shows a rather steep dependence with a small peak at 77 m.The changes of mid-infrared spectra by heating were measured. Change in chlorite spectrum is the most significant. Many fine features appear by heating and then they disappear. Above 900°C one broad feature remains around 10 m. Fine features of the montmorillonite spectrum disappear by heating. For serpentine, many new peaks appear and the spectrum resembles the spectrum of olivin. In near-infrared a band around 2.72 m disappears by heating.Extinction coefficients at very low temperatures were measured in the far-infrared region. For montmorillonite and serpentine, the spectrum is the same as that at room temperature. The double peaks of chlorite around 80 m become higher.     

Ocean acidification and photic‐zone anoxia at the Toarcian Oceanic Anoxic Event: Insights from the Adriatic Carbonate Platform

Severe global climate change led to the deterioration of environmental conditions in the oceans during the Toarcian Stage of the Jurassic. Carbonate platforms of the Western Tethys Ocean exposed in Alpine Tethyan mountain ranges today offer insight into this period of environmental upheaval. In addition to informing understanding of climate change in deep time, the effect of ancient carbon cycle perturbations on carbonate platforms has important implications for anthropogenic climate change; the patterns of early Toarcian environmental deterioration are similar to those occurring in modern oceans. This study focuses on the record of the early Toarcian Oceanic Anoxic Event (ca 183.1 Ma) in outcrops of the north‐west Adriatic Carbonate Platform in Slovenia. Amidst environmental deterioration, the north‐west Adriatic Platform abruptly transitioned from a healthy, shallow‐water environment with diverse metazoan ecosystems to a partially drowned setting with low diversity biota and diminished sedimentation. An organic carbon‐isotope excursion of ?2.2‰ reflects the massive injection of CO₂ into the ocean‐atmosphere system and marks the stratigraphic position of the Toarcian Oceanic Anoxic Event. A prominent dissolution horizon and suppressed carbonate deposition on the platform are interpreted to reflect transient shoaling of the carbonate compensation depth to unprecedentedly shallow levels as the dramatic influx of CO₂ overwhelmed the ocean’s buffering capacity, causing ocean acidification. Trace metal geochemistry and palaeoecology highlight water column deoxygenation, including the development of photic‐zone anoxia, preceding and during the Toarcian Oceanic Anoxic Event. Ocean acidification and reduced oxygen levels likely had a profoundly negative effect on carbonate‐producing biota and growth of the Adriatic Platform. These effects are consistent with the approximate doubling of the concentration of CO₂ in the ocean‐atmosphere system from pre‐event levels, which has previously been linked to a volcanic triggering mechanism. Mercury enrichments discovered in this study support a temporal and genetic link between volcanism, the Toarcian Oceanic Anoxic Event and the carbonate crisis.     

Social capital as a shield against anxiety among displaced residents from Fukushima

The March 2011 meltdowns at the Fukushima nuclear power plants in Japan resulted in an increased risk of psychological distress among affected residents. We conducted original surveys of Futaba residents, a town in Fukushima where all of the residents were forced to evacuate from their homes due to radioactive contamination, obtaining 585 responses (a response rate of about 20%). Using this original data set, we investigate the role of social capital in maintaining mental health among the residents. First, we found the level of stress captured by the Kessler index (K6) to be unusually high compared both with people across Japan and with those who were displaced because of the earthquake and/or tsunami (but not the nuclear catastrophe). However, having high levels of social capital—captured by the number of neighbors from Futaba after displacement, participation in volunteer work after displacement, and participation in tea parties after displacement—plays an important role in reducing anxiety and distress among Futaba residents. Finally, we provide concrete recommendations for policy makers and NGOs to increase resilience among affected residents by strengthening social ties.     

Stochastic analysis of bed-thickness distribution of sediments

On formation of a bed and distribution of bed thickness, A. N. Kolmogorov presented a mathematical explanation that if repetitive alternations of material accumulation and erosion form a sequence of beds, the resultant bed-thickness distribution curve takes a shape truncated by the ordinate at zero thickness. In this truncated distribution curve, its continuation and extension from positive to negative thickness represents the distribution of beds with negative thickness, that is, the depth of erosion. When a distribution curve, including both positive and negative parts, is expressed by a function f(x),the ratio \(\int_0^\infty {f(x)dx to} \int_{ - \infty }^\infty {f(x)dx} \) ,called Kolmogorov's coefficient and designated as p,is a parameter representing the degree of accumulation in the depositional environment. On the assumption that f(x)is described by the Gaussian distribution function, the coefficient pfor Permian and Pliocene sequences in central Japan was calculated. The coefficients also were obtained from published data for different types of sediments from other areas. It was determined that they are more or less different depending on their depositional environments. The calculated results are summarized as follows: $$\begin{gathered} p = 0.80 - 1.0for{\text{ }}alluvial{\text{ }}or{\text{ }}fluvial{\text{ }}deposits \hfill \\ p = 0.65 - 0.95for{\text{ }}nearshore{\text{ }}sediments \hfill \\ p = 0.55 - 0.95for{\text{ }}geosynclinal{\text{ }}sediments \hfill \\ p = 0.90 - 1.0for{\text{ }}varves \hfill \\ \end{gathered} $$ In addition, a ratio \(q = \int_0^\infty {xf(x)dx/} \int_{ - \infty }^\infty {|x|f(x)dx} \) ,called Kolmogorov's ratio in this paper, is introduced for estimating a degree of total thickness actually observed in the field relative to total thickness once present in a basin. The calculated results of Kolmogorov's ratio are as follows: $$\begin{gathered} q = 0.88 - 1.0for{\text{ }}alluvial{\text{ }}or{\text{ }}fluvial{\text{ }}deposits \hfill \\ q = 0.68 - 0.98for{\text{ }}nearshore{\text{ }}sediments \hfill \\ q = 0.55 - 0.96for{\text{ }}geosynclinal{\text{ }}sediments \hfill \\ q = 0.92 - 1.0for{\text{ }}varves \hfill \\ \end{gathered} $$ The sedimentological significance of these values is discussed.     

Discriminating residual and colluvial soils using topographic analysis in a small,forested catchment in Japan

Soil moisture plays an important role in hydrology. Understanding factors (such as topography, vegetation, and meteorological conditions) that influence spatio‐temporal variability in soil moisture, and how this influence is manifested, is important for understanding hydrological processes. A number of distributed (quasi‐)physical hydrological models have been developed to investigate this subject. Previous studies have shown that the spatial differences in the distribution of soil types (residual and colluvial soils) dominantly reflect spatio‐temporal fluctuations in soil moisture and runoff. We present a methodology for assessing the spatial distribution of residual and colluvial soils, which differ with respect to their physical characteristics, in a 0·88 km² forested catchment with complex topography and a complex land‐use history. Our method is based on penetration resistance profile data; in this data set, each data point represents soil physical characteristics within an area of about 25 m². If the spatial distribution of soils under similar meteorological, geological, historical land use, and other conditions could be characterized on the basis of similarity in topographic features, then the spatial distribution of soil could be predicted based on relationships between various topographic indices (e.g. topographic index and local slope). We tested whether our model correctly assessed the reference data. The model's results were 90·5% correct for residual soils and 87·3% correct for colluvial soils. Further studies will quantify the relationships between topographic features of land covered by residual and colluvial soils and changes in spatio‐temporal variations in the catchment (e.g. vegetation and land use) as a function of geology or meteorology. Copyright © 2007 John Wiley & Sons, Ltd.