Factors affecting marine debris deposition at French Frigate Shoals, Northwestern Hawaiian Islands Marine National Monument, 1990-2006

Data on the amount and type of small debris items deposited on the beaches of the Hawaiian Islands National Wildlife Refuge Tern Island station, French Frigate Shoals were collected over 16 years. We calculated deposition rates and investigated the relationship among deposition and year, season, El Ni?o and La Ni?a events from 1990 to 2006. In total 52,442 debris items were collected with plastic comprising 71% of all items collected. Annual debris deposition varied significantly (range 1116-5195 items) but was not influenced by season. Debris deposition was significantly greater during El Ni?o events as compared to La Ni?a events. Although often deduced to influence floating marine pollution, this study provides the first quantitative evidence of the influence of El Ni?o/La Ni?a cycles on marine debris deposition.     

Evaluation of the ECMWF 32-day ensemble predictions during 2009 season of western North Pacific tropical cyclone events on intraseasonal timescales

The performance of the ECMWF 32-day ensemble predictions of western North Pacific tropical cyclone events (formation plus track) made once a week during the 2009 season is evaluated with the same procedures as for the 2008 season. Seventeen of the 23 tropical cyclones during the 2009 season occurred during multiple storm scenarios that are more difficult to predict, and many of the deficient track predictions involved unusual and rapidly changing tracks that typically involve interactions with adjacent synoptic circulations that are not predictable on intraseasonal timescales (10–30 days). Such incorrect predictions of the duration and tracks of these multiple cyclones were found to degrade the performance in predicting subsequent tropical cyclone formations and tracks during the 32-day integration. Predominantly northward tracks throughout the life cycle tended to be less predictable on intraseasonal timescales. Given these caveats, the overall performance of the ECMWF ensemble for the 12 typhoons was more successful than during the 2008 season. However, the performance for three tropical storms during the 2009 season was less successful due to the difficult track forecast scenarios. A surprisingly good performance was found in predicting the formation location and early track segments of eight minimal tropical storms or tropical depressions. The less satisfactory aspect for many of the late season tropical depressions was that the ECMWF ensemble continued to predict member vortices for extended periods after the system had actually dissipated.     

Lessons learned from bacterial transport research at the South Oyster Site

This paper provides a review of bacterial transport experiments conducted by a multiinvestigator, multiinstitution, multidisciplinary team of researchers under the auspices of the U.S. Department of Energy (DOE). The experiments were conducted during the time period 1999-2001 at a field site near the town of Oyster, Virginia known as the South Oyster Site, and included four major experimental campaigns aimed at understanding and quantifying bacterial transport in the subsurface environment. Several key elements of the research are discussed here: (1) quantification of bacterial transport in physically, chemically, and biologically heterogeneous aquifers, (2) evaluation of the efficacy of conventional colloid filtration theory, (3) scale effects in bacterial transport, (4) development of new methods for microbial enumeration and screening for low adhesion strains, (5) application of novel hydrogeophysical techniques for aquifer characterization, and (6) experiences regarding management of a large field research effort. Lessons learned are summarized in each of these areas. The body of literature resulting from South Oyster Site research has been widely cited and continues to influence research into the controls exerted by aquifer heterogeneity on reactive transport (including microbial transport). It also served as a model (and provided valuable experience) for subsequent and ongoing highly-instrumented field research efforts conducted by DOE-sponsored investigators.     

Simulations of Hurricane Katrina (2005) under sea level and climate conditions for 1900

Global warming may result in substantial sea level rise and more intense hurricanes over the next century, leading to more severe coastal flooding. Here, observed climate and sea level trends over the last century (c. 1900s to 2000s) are used to provide insight regarding future coastal inundation trends. The actual impacts of Hurricane Katrina (2005) in New Orleans are compared with the impacts of a similar hypothetical hurricane occurring c. 1900. Estimated regional sea level rise since 1900 of 0.75 m, which contains a dominant land subsidence contribution (0.57 m), serves as a ‘prototype’ for future climate-change induced sea level rise in other regions. Landform conditions c. 1900 were estimated by changing frictional resistance based on expected additional wetlands at lower sea levels. Surge simulations suggest that flood elevations would have been 15 to 60 % lower c. 1900 than the conditions observed in 2005. This drastic change suggests that significantly more flood damage occurred in 2005 than would have occurred if sea level and climate conditions had been like those c. 1900. We further show that, in New Orleans, sea level rise dominates surge-induced flooding changes, not only by increasing mean sea level, but also by leading to decreased wetland area. Together, these effects enable larger surges. Projecting forward, future global sea level changes of the magnitude examined here are expected to lead to increased flooding in coastal regions, even if the storm climate is unchanged. Such flooding increases in densely populated areas would presumably lead to more widespread destruction.     

Enhanced velocity mixed finite element methods for modeling coupled flow and transport on non-matching multiblock grids

The enhanced velocity mixed finite element method, due to Wheeler et al. (Comput Geosci 6(3–4):315–332, 2002), is analyzed and extended to the problem of modeling slightly compressible flow coupled to the transport of chemical species through porous media, on non-matching multiblock grids. Applications include modeling bio-remediation of heavy oil spills and many other subsurface hazardous wastes, angiogenesis in transition of tumors from dormant to malignant states, transport of contaminants in ground water flow, and acid injection from well bores to increase permeability of surrounding rock. The analysis and numerical examples presented here demonstrate convergence and computational efficiency of this method.     

Phosphorus fractions in the surface sediments of three mangrove systems of southwest coast of India

The phosphorus fractions in three tropical mangrove systems of Cochin region were analysed by sequential extraction method. Iron-bound phosphorus was the major fraction in the first two stations, while station 3 was exclusively dominated by calcium-bound phosphorus. Compared to other stations, about tenfold increase in total phosphorus content was observed at station 3. This station is a congregation of communally breeding birds, and there is accumulation of bird guano. Mineralogical analysis showed the presence of monetite, a thermodynamically metastable calcium phosphate mineral, in this unique system. The excreta and carcass of the birds in this sanctuary seems to be the reason for the formation of monetite, which is favoured by periodic fluctuations in redox potential. The high mass percentages of calcium and phosphorus by XRF and SEM–EDS analysis confirm the existence of calcium phosphate mineral at station 3. First two stations did not show any noticeable difference in phosphorus fractions and inorganic fractions constituted to about 65% of total phosphorus. But at station 3, inorganic fractions were about 92%. Low C:P ratios and low organic phosphorus content indicated active mineralisation of phosphorus at station 3. Bioavailable fractions of phosphorus at stations 1 and 2 were about 75%, whereas 98% of the total phosphorus was bioavailable at station 3. Since the bulk of the total phosphorus is bioavailable, these mangrove sediments have the potential to act as source of phosphorus to the overlying waters.     

Understanding the evolution of syn-depositional folds: Coupling decompaction and 3D sequential restoration

The analysis of basin dynamics and burial evolution requires a good understanding of sediment compaction. Classically, decompaction of sediments is performed in one dimension at a well location, using either a simple compaction/depth relationship or more complex elasto-plastic models. This paper presents a new approach combining sequential decompaction with 3D restoration to allow for a true 3D basin analysis. Decompaction is performed in 3D after each restoration step, thus taking into account possible tectonic events and lateral thickness variations. Care is taken to apply decompaction to ensure volume continuity especially around faults. This approach is particularly suitable for syn-depositional folds whose growth strata constrain tectonic evolution through time.The proposed approach is applied to the sand-rich turbiditic reservoir analogue of Annot (SE France) where two fictitious wells are used to compare the new 3D technique to a well decompaction analysis. Coupling restoration and decompaction leads to an improved assessment of the basin history: an uplift of the underlying units is identified, which was not detected using decompaction on wells only. Such differences may have a significant impact on possible hydrocarbon maturation models of the basin. Moreover, the geometry of the restored and decompacted models can better constrains the basin history, and influence our understanding of potential hydrocarbon migration pathways.     

High-resolution observations of aggregate flux during a sub-polar North Atlantic spring bloom

An aggregate flux event was observed by ship and by four underwater gliders during the 2008 sub-polar North Atlantic spring bloom experiment (NAB08). At the height of the diatom bloom, aggregates were observed as spikes in measurements of both particulate backscattering coefficient (b_bp) and chlorophyll a fluorescence. Optical sensors on the ship and gliders were cross-calibrated through a series of simultaneous profiles, and b_bp was converted to particulate organic carbon. The aggregates sank as a discrete pulse, with an average sinking rate of ∼75 m d⁻¹; 65% of aggregate backscattering and 90% of chlorophyll fluorescence content was lost between 100 m and 900 m. Mean aggregate organic carbon flux at 100 m in mid-May was estimated at 514 mg C m⁻² d⁻¹, consistent with independent flux estimates. The use of optical spikes observed from gliders provides unprecedented coupled vertical and temporal resolution measurements of an aggregate flux event.