Evaluating essential processes and forecast requirements for meteotsunami-induced coastal flooding

Natural Hazards - Meteotsunamis pose a unique threat to coastal communities and often lead to damage of coastal infrastructure, deluge of nearby property, and loss of life and injury. The Great...     

Sustained Ability of a Natural Microbial Community to Remove Nitrate from Groundwater

Microbial-mediated nitrate removal from groundwater is widely recognized as the predominant mechanism for nitrate attenuation in contaminated aquifers and is largely dependent on the presence of a carbon-bearing electron donor. The repeated exposure of a natural microbial community to an electron donor can result in the sustained ability of the community to remove nitrate; this phenomenon has been clearly demonstrated at the laboratory scale. However, in situ demonstrations of this ability are lacking. For this study, ethanol (electron donor) was repeatedly injected into a groundwater well (treatment) for six consecutive weeks to establish the sustained ability of a microbial community to remove nitrate. A second well (control) located upgradient was not injected with ethanol during this time. The treatment well demonstrated strong evidence of sustained ability as evident by ethanol, nitrate, and subsequent sulfate removal up to 21, 64, and 68%, respectively, as compared to the conservative tracer (bromide) upon consecutive exposures. Both wells were then monitored for six additional weeks under natural (no injection) conditions. During the final week, ethanol was injected into both treatment and control wells. The treatment well demonstrated sustained ability as evident by ethanol and nitrate removal up to 20 and 21%, respectively, as compared to bromide, whereas the control did not show strong evidence of nitrate removal (5% removal). Surprisingly, the treatment well did not indicate a sustained and selective enrichment of a microbial community. These results suggested that the predominant mechanism(s) of sustained ability likely exist at the enzymatic- and/or genetic-levels. The results of this study demonstrated the in situ ability of a microbial community to remove nitrate can be sustained in the prolonged absence of an electron donor.     

Site selectivity of the boring Rogerella isp. infesting Cardiaster granulosus (Goldfuss) (Echinoidea) in the type Maastrichtian (Upper Cretaceous,Belgium)

A burrowing spatangoid echinoid (heart urchin), Cardiaster granulosus (Goldfuss), from the type area of the Maastrichtian Stage (Upper Cretaceous) in Belgium, was infested only in the plates of the ambulacral petals by acrothoracian barnacle borings, Rogerella isp. This infestation was after the death and exhumation of the echinoid. The distribution of Rogerella may indicate the azimuth of current flow at the time of exhumation prior to final burial. Copyright © 2015 John Wiley & Sons, Ltd.     

The two Suvasvesi impact structures,Finland: Argon isotopic evidence for a “false” impact crater doublet

The two neighboring Suvasvesi North and South impact structures in central‐east Finland have been discussed as a possible impact crater doublet produced by the impact of a binary asteroid. This study presents ⁴⁰Ar/³⁹Ar geochronologic data for impact melt rocks recovered from the drilling into the center of the Suvasvesi North impact structure and melt rock from glacially transported boulders linked to Suvasvesi South. ⁴⁰Ar/³⁹Ar step‐heating analysis yielded two essentially flat age spectra indicating a Late Cretaceous age of ~85 Ma for the Suvasvesi North melt rock, whereas the Suvasvesi South melt sample gave a Neoproterozoic minimum (alteration) age of ~710 Ma. Although the statistical likelihood for two independent meteorite strikes in close proximity to each other is rather low, the remarkable difference in ⁴⁰Ar/³⁹Ar ages of >600 Myr for the two Suvasvesi impact melt samples is interpreted as evidence for two temporally separate, but geographically closely spaced, impacts into the Fennoscandian Shield. The Suvasvesi North and South impact structures are, thus, interpreted as a “false” crater doublet, similar to the larger East and West Clearwater Lake impact structures in Québec, Canada, recently shown to be unrelated. Our findings have implications for the reliable recognition of impact crater doublets and the apparent rate of binary asteroid impacts on Earth and other planetary bodies in the inner solar system.     

Sonication of bacteria, phytoplankton and zooplankton: Application to treatment of ballast water

We investigated the effect of high power ultrasound, at a frequency of 19 kHz, on the survival of bacteria, phytoplankton and zooplankton, in order to obtain estimates of effective exposure times and energy densities that could be applied to design of ultrasonic treatment systems for ballast water. Efficacy of ultrasonic treatment varied with the size of the test organism. Zooplankton required only 3-9s of exposure time and 6-19 J/mL of ultrasonic energy to realize a 90% reduction in survival. In contrast, decimal reduction times for bacteria and phytoplankton ranged from 1 to 22 min, and decimal reduction energy densities from 31 to 1240 J/mL. Our results suggest that stand-alone ultrasonic treatment systems for ballast water, operating at 19-20 kHz, may be effective for planktonic organisms >100 microm in size, but smaller planktonic organisms such as phytoplankton and bacteria will require treatment by an additional or alternative system.     

Simulating flood events at the Twin Ports of Duluth-Superior using a linked hydrologic-hydrodynamic framework

Ocean Dynamics - Generally, ports in the North American Great Lakes are not supported with navigational guidance (water level, water temperature, currents, ice) by NOAA’s Great Lakes...     

Field evidence for the influence of weathering on rock erodibility and channel form in bedrock rivers

Erosion processes in bedrock‐floored rivers shape channel cross‐sectional geometry and the broader landscape. However, the influence of weathering on channel slope and geometry is not well understood. Weathering can produce variation in rock erodibility within channel cross‐sections. Recent numerical modeling results suggest that weathering may preferentially weaken rock on channel banks relative to the thalweg, strongly influencing channel form. Here, we present the first quantitative field study of differential weathering across channel cross‐sections. We hypothesize that average cross‐section erosion rate controls the magnitude of this contrast in weathering between the banks and the thalweg. Erosion rate, in turn, is moderated by the extent to which weathering processes increase bedrock erodibility. We test these hypotheses on tributaries to the Potomac River, Virginia, with inferred erosion rates from ~0.1 m/kyr to >0.8 m/kyr, with higher rates in knickpoints spawned by the migratory Great Falls knickzone. We selected nine channel cross‐sections on three tributaries spanning the full range of erosion rates, and at multiple flow heights we measured (1) rock compressive strength using a Schmidt hammer, (2) rock surface roughness using a contour gage combined with automated photograph analysis, and (3) crack density (crack length/area) at three cross‐sections on one channel. All cross‐sections showed significant (p < 0.01 for strength, p < 0.05 for roughness) increases in weathering by at least one metric with height above the thalweg. These results, assuming that the weathered state of rock is a proxy for erodibility, indicate that rock erodibility varies inversely with bedrock inundation frequency. Differences in weathering between the thalweg and the channel margins tend to decrease as inferred erosion rates increase, leading to variations in channel form related to the interplay of weathering and erosion rate. This observation is consistent with numerical modeling that predicts a strong influence of weathering‐related erodibility on channel morphology. Copyright © 2017 John Wiley & Sons, Ltd.     

Three‐dimensional receiver deghosting of seismic streamer data using L1 inversion and redundant extended radon dictionary

In this paper, we propose a novel three‐dimensional receiver deghosting algorithm that is capable of deghosting both horizontal and slanted streamer data in a theoretically consistent manner. Our algorithm honours wave propagation phenomena in a true three‐dimensional sense and frames the three‐dimensional receiver deghosting problem as a Lasso problem. The ultimate goal is to minimise the mismatch between the actual measurements and the simulated wavefield with an L1 constraint applied in the extended Radon space to handle the underdetermined nature of this problem. We successfully demonstrate our algorithm on a modified three‐dimensional EAGE/SEG Overthrust model and a Red Sea marine dataset.     

Modeling the ice-attenuated waves in the Great Lakes

Ocean Dynamics - A partly coupled wave-ice model with the ability to resolve ice-induced attenuation on waves was developed using the Finite-Volume Community Ocean Model (FVCOM) framework and...     

Dealing with hurricane surge flooding in a changing environment: part I. Risk assessment considering storm climatology change,sea level rise,and coastal development

Coastal flood risk will likely increase in the future due to urban development, sea-level rise, and potential change of storm surge climatology, but the latter has seldom been considered in flood risk analysis. We propose an integrated dynamic risk analysis for flooding task (iDraft) framework to assess coastal flood risk at regional scales, considering integrated dynamic effects of storm climatology change, sea-level rise, and coastal development. The framework is composed of two components: a modeling scheme to collect and combine necessary physical information and a formal, Poisson-based theoretical scheme to derive various risk measures of interest. Time-varying risk metrics such as the return period of various damage levels and the mean and variance of annual damage are derived analytically. The mean of the present value of future losses (PVL) is also obtained analytically in three ways. Monte Carlo (MC) methods are then developed to estimate these risk metrics and also the probability distribution of PVL. The analytical and MC methods are theoretically and numerically consistent. A case study is performed for New York City (NYC). It is found that the impact of population growth and coastal development on future flood risk is relatively small for NYC, sea-level rise will significantly increase the damage risk, and storm climatology change can also increase the risk and uncertainty. The joint effect of all three dynamic factors is possibly a dramatic increase of the risk over the twenty-first century and a significant shift of the probability distribution of the PVL towards high values. In a companion paper (Part II), we extend the iDraft to perform probabilistic benefit-cost analysis for various flood mitigation strategies proposed for NYC to avert the potential impact of climate change.