A semi-empirical wind set-up forecasting model for Lake Champlain

The precision of Lake Champlain's water level estimation is a key component in the flood forecasting process for the Richelieu River. Hydrological models do not typically take into consideration the effects of the wind on the water level (also known as the wind set-up). The objective of this study is to create an empirical wind set-up forecast model for Lake Champlain during high wind events. The proposed model uses wind speed and direction across the Lake, as well as wind gusts as inputs. The model is calibrated to a subset of observations and evaluated on an independent sample, considering four wind speed bins. It is tested and compared to a variant of the Zuider Zee equation on 20 wind set-up events that occurred between 2017 and 2019 using hindcast data from five different numerical weather prediction systems (GDPS, RDPS, HRDPS, NOAA and ECMWF). A quantile mapping-based forecast calibration scheme is implemented for each of the forecast products to correct their biases. Results show that events are successfully predicted by the proposed model at least 72 h in advance. These results are better than the other comparative models found in the literature and tested herein. Overall, significant improvements are obtained by including wind speed and wind gusts from different weather stations.     

Pathogens in Water: Value and Limits of Correlation with Microbial Indicators

This article discusses the value and limitations of using microbial indicators to predict occurrence of enteric pathogens in water. Raw or treated sewage is a primary source of fecal contamination of the receiving surface water or groundwater; hence, understanding the relationship between pathogens and indicators in sewage is an important step in understanding the correlation in receiving waters. This article presents three different datasets representing different concentrations of pathogens and microbial indicators: sewage containing high concentrations of pathogens and indicators, surface water with variable concentrations, and groundwater with low concentrations. In sewage, even with very high levels of microorganisms, no mathematical correlation can predict the type or concentration of any pathogen. After discharge in the environment, direct correlation becomes biologically improbable as dilution, transport, and different inactivation rates occur in various environments. In surface waters, advanced statistical methods such as logistic regression have provided some level of predictability of the occurrence of pathogens but not specific counts. In groundwater, the continuous absence of indicators indicates an improbable occurrence of pathogen. In contrast, when these indicators are detected, pathogen occurrence probability increases significantly. In groundwater, given the nature and dissemination pattern of pathogenic microorganisms, a direct correlation with fecal microbial indicators is not observed and should not be expected. However, the indicators are still useful as a measure of risk. In summary, many pathogens of public health importance do not behave like fecal microbial indicators, and there is still no absolute indicator of their presence, only a probability of their co‐occurrence.     

Giant palaeotsunami in Kiribati: Converging evidence from geology and oral history

For tsunami science within Oceania, the vast Central and Western Pacific (CEWEP) is an anomalous region because of the scarcity of historical tsunami observations and the complete absence of dated palaeotsunami evidence. This paper therefore records the first dated high-magnitude palaeotsunami event within the CEWEP region. A combination of both geological data and oral history is provided for a palaeotsunami that struck remote Makin island, northernmost of the Gilbert Islands in Kiribati, toward the end of the 16th century. A previously undocumented oral tradition of giant waves is well known to the people of Makin. Narration of this legend by the Wiin te Maneaba, traditional storyteller on Makin, provided important details supporting a tsunami hypothesis. The legend preserves credible information surrounding the giant-wave origin of Rebua and Tokia, two prominent subaerial megaclasts of blade and block geometry that were transported 80–130 m shorewards from the reef-edge source and deposited in sideways and inverted orientations. From available hydrodynamic flow transport equations, minimum flow velocities of 7.3–16.3 m s⁻¹ were generated, depending on whether the reefblocks were rotated or lifted onto the reef platform. The youngest U-Th age-dates for fossil corals retrieved from the reefblocks give a maximum age for the palaeotsunami of circa AD 1576. Several far-field Pacific Rim and regional possibilities exist for tsunamigenesis. These include subduction-zone seismicity and catastrophic volcanic eruption, both of which have been linked to earlier (late 15th century) palaeotsunami events recorded elsewhere in the Pacific Islands. However, the available evidence here suggests that the ~AD 1576 Makin palaeotsunami was more likely to have been locally generated by tsunamigenic offshore submarine slope failure close to Makin's western reef, associated with the giant arcuate bight structure that characterizes the northern rim of Butaritari atoll.     

Agrobiodiversity and Shade Coffee Smallholder Livelihoods: A Review and Synthesis of Ten Years of Research in Central America

We used households as the primary unit of analysis to synthesize agrobiodiversity research in small-scale coffee farms and cooperatives of Nicaragua and El Salvador. Surveys, focus groups, and plant inventories were used to analyze agrobiodiversity and its contribution to livelihoods. Households managed high levels of agrobiodiversity, including 100 shade tree and epiphyte species, food crops, and medicinals. Small farms contained higher levels of agrobiodiversity than larger, collectively managed cooperatives. Households benefited from agrobiodiversity through consumption and sales. To better support agrobiodiversity conservation, our analysis calls for a hybrid approach integrating bottom-up initiatives with the resources from top-down projects.     

A new tomographic image of the Pyrenean lithosphere from teleseismic data

A new tomographic model of the Pyrenean lithosphere is determined down to 200 km depth from teleseismic P and PKP travel times, with a lateral resolution of 0.25°. Compared to previous models, two important improvements are 1) a larger number of stations with a more even distribution, in particular to the west of the range, and 2) the introduction, before inversion, of crustal corrections inferred from previous refraction and reflection experiments. This last point is crucial because a strong Moho jump (up to 20 km) is present at the North Pyrenean Fault, the former boundary between Eurasian and Iberian plates. The comparison of the models obtained with and without crustal corrections reveals the strong contamination of the models by the crust down to 100 km depth. In the uncorrected model, a large strip with negative P-velocity anomalies, previously interpreted as subduction of lower crust, is observed. It disappears in the corrected model. Moreover, the introduction of crustal corrections allows us to reveal short wavelength heterogeneities which were hidden by the crustal signal.An attempt is made to relate the heterogeneities revealed by the tomographic model with the tectonic history of the Pyrenees, in particular with the Alpine orogeny. The Alpine phase includes an extensive episode with generation of the thin continental crust and possibly the opening of an oceanic sea floor, and then a compressive stage. In our model, no signature of an oceanic subducted slab could be detected all along the range, a result which rules out the opening of a large oceanic floor before the compressive stage. A subduction of continental crust is possible but, due to the transformation of lower crust into eclogite at depth, it can not be detected by seismological methods, whereas it was observed from electrical and gravity data. To the East of the range, large heterogeneities with low velocities are ascribable to the Neogene extension related to the rotation of the Corso–Sardo block and the opening of the Gulf of Lion. A prominent high velocity anomaly extending down to 200 km in eastern-central Pyrenees could possibly be interpreted as a detached piece of the Tethys slab. In north of Iberia outside the range, deep (down to 200 km) low velocity structures oriented N130°E are probably related to Hercynian orogeny.     

Hydrothermal dolomite marbles associated with charnockitic magmatism in the Proterozoic Bamble Shear Belt,south Norway

Deformed and metamorphosed dolomite marbles in the Kragerø area of the Bamble Shear Belt occur as lenses within metasupracrustal sequences, as matrix in bodies resembling magmatic breccias, and as veins/dykes cutting amphibolites and metagabbros. A common origin is not evident from the field relationships, but is nevertherless probable due to great geochemical similarities between dolomite from the different occurrences. They are characterized by higher REE, Ni, Co, Cr and Sc, and lower Ba and Sr contents relative to metasedimentary marbles occurring nearby. Sm-Nd isotope data shows that the dolomites are of Sveconorwegian age (1175±37 Ma). The dolomite marbles are very weakly LREE-enriched and display in most cases positive Eu anomalies. Their stable isotope compositions are uniform (¹⁸O=+9.6 to +10.7; ¹³C=-8.5 to-6.2), their initial ⁸⁷Sr/⁸⁶Sr ratios are high (0.706–0.709), whereas their age corrected _Nd varies from +0.7 to-1.5. Geochemically the dolomitic marbles differ considerably from sedimentary or metasedimentary marbles as well as from carbonatites. The Kragerø dolomite marbles represent deformed and metamorphosed hydrothermal veins or vein-complexes deposited in tensional fractures in the deep crust. Although the dolomitic marbles regionally are of minor volume, the dolomite deposition represents a specific and important event in the geological evolution of the Bamble Shear Belt. Their geochemical and isotopic homogeneity on a regional scale suggest that the hydrothermal solutions were supplied from a very large, homogeneous reservoir. Trace elements, stable and radiogenic isotopes, and field and isotopic age relationships are consistent with a deposition from hydrothermal solutions which were exsolved from crystallizing charnockitic intrusions and subsequently interacted with the crust. The parental magma to these intrusions underplated the crust and raised the geotherm of a carbonated ultramafic uppermost mantle, and imposed decarbonation and fluid release. These fluids were channelled into a large degassing zone now found as a deformed, regional zone with hydrothermal dolomite deposits, albitites, apatite-veins and widespread scapolitization. Whether the CO₂-rich fluids, which precipitated the Kragerø dolomites, pervasively infiltrated crustal rocks at a deeper level and caused granulitization is ambiguous, but possible.     

Stellar seismology from space: The Evris experiment on board Mars 94

High precision photometry from space is the only technique to detect the nonradial oscillations of a significant set of stars with different masses, ages, angular momentum, chemical composition, as already observed for the Sun. During an observation run of several days, a reasonably small telescope (10 cm) will collect enough photons to detect periodic signals of relative amplitude as low as 10 ^–6, coherent over this period. The frequency resolution necessary to distinguish the rotational splitting (0.5 H) will be achieved in increasing the observation run to 20 days.     

Solar and anthropogenic imprints on Lake Masoko (southern Tanzania) during the last 500 years

The Masoko crater-lake in southern Tanzania provides a continuous record of environmental changes covering the last 500 years. Multi-proxy studies were performed on a 52 cm sediment core retrieved from the deepest part of the lake. Magnetic, organic carbon, geochemical proxies and pollen assemblages indicate a dry climate during the ‘Little Ice Age’ (AD 1550–1850), confirming that the LIA in eastern Africa resulted in marked and synchronous hydrological changes. However, the direction of response varies between different African lakes (low versus high lake-levels), indicating strong regional contrasts that prevent the clear identification of climate trends over eastern Africa at this time. Inferred changes in Masoko lake-levels closely resemble the record of solar activity cycles, indicating a possible control of solar activity on the climate in this area. This observation supports previous results from East African lakes, and extends this relationship southward. Finally, anthropogenic impact is observed in the Masoko sediments during the last 60 years, suggesting that human disturbance significantly affected this remote basin during colonial and post-colonial times.     

Sur la paléoflore post-carbonifère de la bordure est du Bassin de Mourzouk (Libye)

Until recently the age of the continental sediments overlaying marine strata of Carboniferous age at the Murzuk Basin was unknown and long distance correlation was not possible because of lack of correlation criteria. The flora now described allows, for the first time, to identify the age of parts of this strata. Together with new sedimentological criteria of subdivision worked out by R.Glaeser, H.Kallenbach and I.Zöller which will be published later, the paleobotanical investigations contribute towards a final subdivision of these continental sediments. The terms “Nubian Series”, and “Posttassilien” will be abandoned, because they are useless within the area concerned. The creation of correlatable stratigraphical data is an important prerequisite for groundwater and mineral exploration within the large areas covered by these strata. Along the eastern Murzuk Basin these sediments containFilicophytae, Pteridophyllae,Pteridospermaphytae, Cycadophytae andConiferophytae. At Jebel Ben Ghnema the upper part of the lower third of the continental sediments contains plants which are known from triassic strata in Europe, India, North America, South America, South Africa, and Asia. At Jebel Ben Ghnema the top of the strata contains Jurassic plants known from Europe, North America, and Asia. Almost 300 kilometres further South at Jebel Ati near the top of these continental sediments plants of Jurassic age were found, too. It seems that the development of this flora has taken place under a generally warm and dry climate with wet seasons. From the paleophytographical point of view the flora described is of great interest, because it contains coexisting species of the Northern and Southern hemisphere. The Jurassic flora is comparable to that known from adjacent basins in Algeria and Egypt, and to flora known from Virginia.