The interanual rainfall variability in Indonesia corresponding to El Niño Southern Oscillation and Indian Ocean Dipole

The Impact of the Indian Ocean Dipole(IOD) and the El Ni?o Southern Oscillation(ENSO) event for Indonesian rainfall has been investigated for the period from 1950 to 2011. Inter-annual change of IOD and ENSO indices are used to investigate their relationship with Indonesian rainfall. By using the wavelet transform method, we found a positive significant correlation between IOD and Indonesian rainfall on the time scale of nearly 2.5–4 years.Furthermore, the positive significant correlation between ENSO(sea surface temperature anomaly at Ni?o3.4 area indices) and Indonesian rainfall exists for shorter than 2 years and between 5.5 to 6.5-year time scales.     

Variations of Kuroshio geostrophic transport south of Japan estimated from long-term IES observations

Two inverted echo sounders were maintained on coastal and offshore sides of the Kuroshio south of Japan from October 1993 to July 2004. Applying the gravest empirical mode method, we obtained a time series of geostrophic transport. Estimated transports generally agree well with geostrophic transports estimated from hydrography. Their agreement with the hydrographic transports is better than that of transports estimated from satellite altimetry data. The geostrophic transport is expressed as the surface transport per unit depth multiplied by the equivalent depth. The geostrophic transport varies mostly with the surface transport and fractionally with the equivalent depth. Seasonal variation of the geostrophic transport has a minimum in March and a maximum in September, with a range of about one fifth of the total transport.     

Vertical double silicate maxima in the sea-ice reduction region of the western Arctic Ocean: Implications for an enhanced biological pump due to sea-ice reduction

The R/V Mirai conducted hydrographic surveys in the western Arctic Ocean during summer 2004 (Mirai04) over wide east-west ranges from Alaska to eastern Siberia, where sea-ice cover has been greatly reduced in recent summers. The obtained data reveal differences in silicate profiles between shelf slope areas east and west of the Chukchi Plateau, the ridge that divides the Canada Basin into the Alaskan and east Siberian sides. East of the plateau, a single silicate maximum was found in a layer of Pacific-origin winter water, as examined in many previous studies. In contrast, west of the plateau, we found vertical double silicate maxima, which are reported for the first time in this study. The shallower silicate maximum corresponded to an N** minimum, signaling denitrification at the shelf bottom. This suggests that the shallower silicate maximum was caused by the spreading of shelf water. In contrast, the deeper silicate maximum corresponded to an oxygen minimum and a maximum silicate/phosphate ratio (Si/P), suggesting that this deeper maximum resulted from the decomposition of opal-shelled organisms. We also compared a silicate profile from Mirai04 to aprofile from the Arctic Ocean Section 94 (AOS94) expedition of 1994, a heavy ice year. The results suggest that sea-ice loss has enhanced biological activities, likely resulting in the appearance of the deeper silicate maximum.     

Process length variation of the cyst of the dinoflagellate Protoceratium reticulatum in the North Pacific and Baltic‐Skagerrak region: calibration as an annual density proxy and first evidence of pseudo‐cryptic speciation

Process length variation of cysts of the dinoflagellate Protoceratium reticulatum (Claparède et Lachmann) Bütschli in surface sediments from the North Pacific was investigated. The average process length showed a significant inverse relation to annual seawater density: σ_{t annual} = ?0.8674 × average process length + 1029.3 (R² = 0.84), with a standard error of 0.78 kg m^?3. A sediment trap study from Effingham Inlet in British Columbia revealed the same relationship between average process length and local seawater density variations. In the Baltic–Skagerrak region, the average process length variation was related significantly to annual seawater density: σ_{t annual} = 3.5457 × average process length ? 993.28 (R² = 0.86), with a standard error of 3.09 kg m^?3. These calibrations cannot be reconciled, which accentuates the regional character of the calibrations. This can be related to variations in molecular data (small subunit, long subunit and internal transcribed spacer sequences), which show the presence of several genotypes and the occurrence of pseudo‐cryptic speciation within this species. Copyright © 2012 John Wiley & Sons, Ltd.     

Least squares and integral methods for the spherical harmonic analysis of theSq-field

Spherical harmonic coefficients (SHCs) for the daily magnetic variation fields (solar and lunar) and the main field of the earth are usually estimated by the method of least squares applied to a truncated spherical harmonic series. In this paper, an integral method for computing the SHCs for the solar quiet daily magnetic variation fieldSq is described and applied toSq data for May and June 1965. TheSq SHCs thus derived are then compared with the results obtained using both unweighted and weighted versions of the least squares method. The weighting used tends to orthogonalize the least squares terms. The integral and weighted least squares results agree closely for terms up to order 4 and degree 30, but both disagree considerably for the higher degree terms with the results of the unweighted least squares. Errors introduced by the numerical integration can be shown to be small, hence the disagreement between integral and unweighted least squares coefficient sets arises from improper weighting. Also, it is concluded that discrepancies between the geomagnetic northward and eastward component-derived coefficient sets arise from either time-dependent external sources that produce non-local-time, based fields or nonpotential sources and not from truncation of the spherical harmonic series as has previously been suggested.Deceased.     

Diurnal freeze–thaw depth in rockwalls: Field measurements and theoretical considerations

Rock temperatures were monitored for a year at two alpine rockwalls in the Akaishi Range, Japan, where permafrost is absent. Diurnal frost and thaw penetration depths were evaluated from subsurface isotherms drawn on the basis of the temperature records at 0, 10 and 40 cm depths. The surface of the rockwalls experienced more than 100 diurnal freeze-thaw cycles, most of which accompanied a frost or thaw penetration shallower than 50 cm, and several long duration cycles with deeper frost or thaw penetration. Theoretical frost and thaw depths were also calculated by incorporating the surface freezing indices into the modified Berggren equation, the results from which were then compared with the actual values. The modified Berggren equation provided values that showed a strong correlation with observed depths, despite somewhat underestimating the actual values. Using the modified Berggren equation, the seasonal frost depth in the observed winter was estimated to be about 4·5 m. The frost and thaw depths are considered to give the maximum estimation of the depth to which frost-induced cracking can propagate in the bedrock.     

Rock weathering processes and landform development in the Sør Rondane Mountains, Antarctica

Field observations of weathering processes and the related landforms, combined with laboratory analyses of weathering products, permit a synthetic evaluation of Late Cenozoic weathering environments in the Sør Rondane Mountains, Antarctica, an arid upland characterized by low temperatures and strong winds. Rates and character of weathering depend mainly on moisture availability and the bedrock geology. Under the humid weathering regime that occurs only locally around the margin of the present sheet, frequent diurnal freeze-thaw cycles in summer cause relatively rapid rock fragmentation. Most of the mountains are situated in the arid weathering regime, under which rock breakdown is very slow unless the rock contains plenty of salts. Salt weathering becomes more intensive and extensive with exposure age, as a result of salt accumulation in rock, eventually producing soils as small as fine-silt size. Lack of clay mineralization even in weathered rocks having been exposed above the ice sheet prior to 4 Ma ago indicates that hydrolysis or carbonation of rock minerals has been insignificant during the past 4 Ma. The final products of weathering are due mainly to salt action and reflect the parent lithology. Resistant fine-grained granite forms strongly oxidized tors carved with tafoni, or fields of mushroom-like boulders overlying the fractured bedrock. Less resistant rocks, like biotite gneiss and amphibolite, produce stone pavements underlain by saline, silty soils up to 30–40 cm thick, the thickness of which corresponds to the maximum thaw depth.     

The rate of bedrock weathering by frost action: Field measurements and a predictive model

Shattering rate, surface temperature, moisture content, and the physical and strength properties of bedrock were measured in four rockwall sites of the Japanese Alps. Five-year observations revealed that the bedrock shattering rate was usually much higher in the freeze-thaw period from October to next May than in the frost-free period from June to September. This indicates that frost action is the most important shattering process, although unusual heavy rainstorms in summer are also responsible for the shattering. A combination of some empirical relationships derived from recent laboratory experiments leads to a predictive model of the frost shattering rate. This model shows that the annual shattering rate is dependent on the annual freeze-thaw frequency on the rock surface, and the degree of saturation and tensile strength of the rock masses. The coefficients involved in the model were determined using the field data.     

Rates of tafoni weathering on uplifted shore platforms in Nojima-Zaki,Boso Peninsula,Japan

Many tafoni occur on the faces of marine cliffs on three uplifted shore platforms with different altitudes and with known ages of emergence. The mean value of the ten largest depths of tafoni, D (cm), was obtained and the period of their formation, t (years), was estimated. The relationship between the two variables was found to be D = 20·3 × (1?e^?0.005t).