Super-parameterization in ocean modeling: Application to deep convection

We explore the efficacy of “super parameterization” (SP) in ocean modeling in which local 2-d non-hydrostatic plume-resolving fine-grained (FG) models are embedded at each vertical column of a coarse-grained (CG) hydrostatic model. A general multi-scale algorithm is described in which tendencies from the FG models are projected onto the CG model which in turn constrains the average state of the FG models, coupling the two models together. The approach is tested in the context of models of open ocean deep convection and compared with a pure hydrostatic, coarse resolution model using convective adjustment (HYD) and a full 3-d non-hydrostatic plume-resolving simulation (NH). The SP model is found to be greatly superior to HYD at much less computational cost than the fully non-hydrostatic calculation.     

Remote sensing of surf zone waves using stereo imaging

The measurement of water wave characteristics, such as wavelength and wave height, in the surf zone is important for monitoring, prediction of erosion, and numerical model calibration. Traditional methods of measuring wave heights have either been limited to a small number of points or have required contact with the water. An experimental study of the remote sensing of water wave elevations, through the application of stereo photogrammetry, is presented. This method uses two spatially offset cameras, with overlapping fields of view, to determine water surface elevation. This remote sensing approach provides data with excellent spatial coverage and spatial and temporal resolution. Additionally, the hardware needs are minimal and the system is quickly deployed, calibrated, and operational.     

No Evidence Supporting Flare-Driven High-Frequency Global Oscillations

The underlying physics that generates the excitations in the global low-frequency (<?5.3?mHz) solar acoustic power spectrum is a well-known process that is attributed to solar convection; however, a definitive explanation as to what causes excitations in the high-frequency regime (>?5.3?mHz) has yet to be found. Karoff and Kjeldsen (Astrophys. J. 678, 73??C?76, 2008) concluded that there is a correlation between solar flares and the global high-frequency solar acoustic waves. We have used Global Oscillation Network Group (GONG) helioseismic data in an attempt to verify the Karoff and Kjeldsen (2008) results as well as compare the post-flare acoustic power spectrum to the pre-flare acoustic power spectrum for 31 solar flares. Among the 31 flares analyzed, we observe that a decrease in acoustic power after the solar flare is just as likely as an increase. Furthermore, while we do observe variations in acoustic power that are most likely associated with the usual p-modes associated with solar convection, these variations do not show any significant temporal association with flares. We find no evidence that consistently supports flare-driven high-frequency waves.     

Age of granite emplacement in the Norseman region of Western Australia

Ion probe U‐Th‐Pb dating of zircons from the Late Archaean granites of the Norseman region of the southeastern Yilgarn shows the existence of two distinct magmatic episodes. Large regional tonalite and granodiorite plutons were emplaced between 2685 and 2690 Ma, whereas large regional granite, and small tonalite and leucogranite plutons that intrude the greenstones have ages of 2660–2665 Ma. A small body of granite that intrudes the western edge of the greenstones has an inferred emplacement of 2672 ± 7Ma, and contains inherited zircon that is ～2800 Ma. The monzogranite core from a second pluton in a similar structural position also contains ～2800 Ma zircon; this age is similar to published Sm‐Nd and Rb‐Sr whole rock ages for banded gneisses associated with other members of this suite of domal plutons and is interpreted as representing the age of a significant component within the source region for these distinctive rocks.

Available geochemical and isotopic data are interpreted as indicating derivation of both the older granodiorite and younger granite suites through anatexis of pre‐existing crust of broadly andesitic composition, whereas both the domal granites and the small, late tonalite plutons could have been derived by anatexis of heterogeneous material similar to that represented by the banded gneisses.

If regional metamorphism was related to the emplacement of large volumes of felsic magma within the upper crust, as suggested by Binns et al. (1976), then the Norseman area has probably undergone two periods of regional metamorphism of comparable intensity at approximately 2660 and 2685 Ma.     

Biofilms and Size Sorting of Fine Sediment During Erosion in Intertidal Sands

The goal of this research was to investigate size-specific retention of clay and silt-sized grains by biofilms in sandy intertidal sediments. Sediment cores were collected from an intertidal flat in Cole Harbour, NS, and eroded at increasing shear stresses (0.08–0.60 Pa) with a Gust microcosm. Half of the cores were eroded without undergoing prior treatment, while sodium hypochlorite was added to the other cores to destroy biofilms. The disaggregated inorganic grain size distribution of sediment resuspended by the Gust microcosm was then obtained with a Multisizer^? 3 Coulter Counter®, and each treated core was compared with its corresponding untreated core. Overall, significantly less total sediment mass was resuspended from untreated cores than from treated cores. At intermediate shear stresses, the sediment resuspended from treated cores contained a greater proportion of fine and medium silts than the sediment resuspended from untreated cores. Very fine silts and clays were not retained preferentially by biofilms. The results show that biofilms stabilize the sediment, but they do not necessarily enhance the proportion of finest sediment sizes, as previously proposed.     

Are burnt sediments reliable recorders of geomagnetic field strength?

This study tests if burnt soils and sediments can provide reliable records of geomagnetic field strength at the time of burning by carrying out an experiment to reproduce the prehistoric use of fire on a clayish soil substratum. Rock magnetic experiments showed that in the upper 0–1 cm of the central part of the burnt surface, remanence is a thermoremanent magnetization carried by single-domain magnetite and that samples are thermally stable. Fourteen specimens from that area were subjected to paleointensity experiments with the Coe method (1967). An intensity of 42.9 ± 5.7 μT was estimated below 440°C, whereas at higher temperatures magneto-mineralogical alterations were observed. Corresponding successful microwave intensity determinations from two specimens gave a mean value of 47.6 μT. Both results are in reasonable agreement with the expected field value of 45.2 μT. Burnt soils of archeological fires thus have the potential to record accurately the paleofield strength and may be useful targets for archeointensity investigations. Coincident results obtained from two different paleointensity determination methods support this conclusion.     

Information and complexity measures applied to observed and simulated soil moisture time series

Abstract

Time series of soil moisture-related parameters provide important insights into the functioning of soil water systems. Analysis of patterns within such time series has been used in several studies. The objective of this work was to compare patterns in observed and simulated soil moisture contents to understand whether modelling leads to a substantial loss of information or complexity. The time series were observed at four plots in sandy soils within the USDA-ARS OPE3 experimental watershed, for a year; precipitation and evapotranspiration (ET) were measured and estimated, respectively, and used for soil water flow simulation with the HYDRUS-1D software. The information content measures are the metric entropy and the mean information gain, and complexity measures are the fluctuation complexity and the effective measure complexity. These measures were computed based on the binary encoding of soil moisture time series, and used probabilities of patterns, i.e. probabilities of joint or sequential appearance of symbol sequences. The information content of daily soil moisture time series was much smaller than that of rainfall data, and had higher complexity, indicating that soil worked essentially as an information filter. Information content and complexity decreased and increased with depth, respectively, demonstrating the increase in the information filtering action of soil. The information measures of simulated soil moisture content were close to those of the measurements, indicating the successful simulation of patterns in the data. The spatial variability of the information measures for simulated soil moisture content at all depths was less pronounced than the one of measured time series. Compared with precipitation and estimated ET, soil moisture time series had more structure and less randomness in this work. The information measures can provide useful complementary knowledge about model performance and patterns in observation and modelling results.

Citation Pan, F., Pachepsky, Y. A., Guber, A. K., & Hill, R. L. (2011) Information and complexity measures applied to observed and simulated soil moisture time series. Hydrol. Sci. J. 56(6), 1027–1039.     

A Review of: “Urban and Regional Technology Planning: Planning Practice in the Global Knowledge Economy”

Haiti and other developing countries have increasingly turned to emigrant remittances as a potential source of development capital. There is a vigorous debate in the development community about the impacts of remittances, however, with concerns about dependence challenging the optimism about a potential new development engine. Based on interviews with forty-two remittance recipients in Haiti and forty-five corresponding senders in New York State, we find that the remittance economy in Haiti is indeed productive and has the potential to generate employment and other important development benefits. That said, there are important limitations created by broader political–economic conditions and deeply entrenched inequalities.     

Lithogeochemical exploration for komatiite-associated Ni-sulfide deposits: strategies and limitations

Summary Lithogeochemistry of komatiites can be useful in exploration for nickel sulfides in two distinct ways: indirectly, through identification of favourable volcanic environments, and more directly, through identification of signatures of crustal contamination and sulfide liquid segregation. However, the discrimination between mineralised and unmineralised sequences is not straightforward.Komatiite chemistry is influenced by a variety of primary magmatic variables, overprinted to various degrees for various elements by the effects of metasomatic alteration. Once highly metasomatised samples have been filtered, primary magmatic signatures are largely retained for the elements Mg, Fe, Si, Al, Ti and Cr, even in cases of extensive CO₂ metasomatism and talc-carbonate alteration. Incompatible trace elements such as Zr and REE are modified to some degree by alteration, particularly in cumulate rocks, but there is evidence for some retention of primary signatures.Favourable volcanic environments, i.e. those containing large-volume lava pathways, can be identified on the basis of their distribution and ratios of whole rock Mg, Fe, Ni, Cr and Ti. Nickel depletion can be recognised in some cases of large mineralised systems where large volumes of sulfide formed at low silicate:sulfide (R) ratios, but is not effective in finding small high-grade ore shoots. PGE in low-S rocks do not appear to be an effective discriminant, owing to the local scale of S-saturation.Crustal contamination is indicated in some mineralised suites on the basis of enriched ratios of strongly to weakly incompatible lithophile elements in fractionated lavas, but the effects of alteration are significant and may be misleading. On the whole, mineralised sequences tend to have more enriched signatures than unmineralised ones, but there may be many false positives and negatives, and if the most CO₂-metasomatised suites are discounted the contrast largely disappears. Overall, the presence of Ni-enriched sulfides is by far the best lithogeochemical indicator there is, and it may be the only really effective one.