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At least 595 records · Page 33Linked to original sources
USGS2021

Numerical simulation of the effects of groundwater withdrawal and injection of high-salinity water on salinity and groundwater discharge, Kaloko-Honokōhau National Historical Park, Hawaiʻi

Kaloko-Honokōhau National Historical Park (KAHO) is located on the west coast of the island of Hawaiʻi and contains water resources exposed in fishponds, anchialine pools, and marine waters that are cultural resources and that provide habitat for threatened, endangered, and other culturally important native species. KAHO’s water resources are sustained by and dependent on groundwater discharge. In 1978, the year of KAHO authorization, the lands immediately surrounding KAHO were undeveloped and zoned for conservation purposes; at present, most surrounding lands are either developed or zoned for industrial, commercial, or residential use. Urbanization of the North Kona District has increased the need for additional drinking and nonpotable (irrigation) water. Because KAHO’s water resources may be affected by existing and proposed groundwater withdrawals and injections of high-salinity water in the surrounding area, the U.S. Geological Survey, in cooperation with the National Park Service, undertook this study to refine the understanding of how groundwater withdrawals and injection of high-salinity water may affect KAHO’s water resources. Changes in KAHO water resources, in terms of changes in salinity and groundwater discharge, were modeled for selected scenarios of groundwater withdrawal and high-salinity water injection in the aquifer. The numerical model was developed using the model code SUTRA, which accounts for density-dependent flow and salinity transport, and included the coastal-confined groundwater system beneath the coastal freshwater-lens system. Model results indicate that withdrawal of additional groundwater from the coastal freshwater-lens system will affect the salinity of KAHO’s anchialine pools, which provide habitat for the endangered orangeblack Hawaiian damselfly ( Megalagrion xanthomelas ). The magnitude of the effect is dependent on the amount and location of the withdrawal. Greater withdrawal rates cause greater increases in salinity in KAHO, other factors being equal. For a given withdrawal rate, the greatest increase in salinity in KAHO is associated with wells withdrawing groundwater in an area inland of KAHO and the least increase in salinity is associated with wells near the coast. Model results also indicate that withdrawal of additional groundwater from the coastal freshwater-lens system will affect the groundwater discharge, in terms of the freshwater component (water with zero salinity) of the discharge, through KAHO. Greater withdrawal rates cause greater reductions in freshwater discharge through KAHO. For a given withdrawal rate, the greatest reduction in freshwater discharge through KAHO is associated with wells near the north boundary of KAHO and the least reduction is associated with wells near the coast to the north and south of KAHO. Injection of high-salinity water that is denser than ocean water can affect the salinity of damselfly habitat in KAHO, with the magnitude of the effect dependent on the location of the injection. Model results indicate that salinity may either increase or decrease in the anchialine pools that provide damselfly habitat in KAHO, depending on the site of injection. Injection inland of KAHO and at sites immediately north and south of KAHO causes a simulated decrease in salinity at the damselfly habitat, whereas injection farther north and south of KAHO causes an increase in salinity. Injection of high-salinity water also causes a reduction in freshwater discharge through KAHO, with the greatest reduction associated with distant injection wells to the north and south of KAHO and the least reduction associated with wells located near and immediately inland from KAHO. The numerical groundwater models developed for this study have a number of limitations. Lack of understanding of the subsurface geology constrains the ability to accurately model the groundwater-flow system. The models developed for this study are nonunique, cannot account for local-scale heterogeneities in the aquifer, and contain uncertainties related to recharge, boundary conditions, assigned parameter values in the model, and representations of the different hydrogeological features. Confidence in model results can be improved by addressing these and other limitations. In spite of these limitations, the three-dimensional numerical model developed for this study provides a useful conceptual understanding of the potential effects of additional withdrawals and injections on groundwater resources in KAHO. Further evaluation of the ecologic effects of the simulated changes in groundwater quality and quantity in KAHO is needed but is beyond the scope of this study.

Hawaii↗
USGS2011

Density estimation in a wolverine population using spatial capture-recapture models

Classical closed-population capture-recapture models do not accommodate the spatial information inherent in encounter history data obtained from camera-trapping studies. As a result, individual heterogeneity in encounter probability is induced, and it is not possible to estimate density objectively because trap arrays do not have a well-defined sample area. We applied newly-developed, capture-recapture models that accommodate the spatial attribute inherent in capture-recapture data to a population of wolverines (Gulo gulo) in Southeast Alaska in 2008. We used camera-trapping data collected from 37 cameras in a 2,140-km 2 area of forested and open habitats largely enclosed by ocean and glacial icefields. We detected 21 unique individuals 115 times. Wolverines exhibited a strong positive trap response, with an increased tendency to revisit previously visited traps. Under the trap-response model, we estimated wolverine density at 9.7 individuals/1,000-km 2 (95% Bayesian CI: 5.9-15.0). Our model provides a formal statistical framework for estimating density from wolverine camera-trapping studies that accounts for a behavioral response due to baited traps. Further, our model-based estimator does not have strict requirements about the spatial configuration of traps or length of trapping sessions, providing considerable operational flexibility in the development of field studies.

Alaska↗
USGS2018

Rapid, remote assessment of Hurricane Matthew impacts using four-dimensional structure-from-motion photogrammetry

Timely assessment of coastal landforms and structures after storms is important for evaluating storm impacts, aiding emergency response and restoration, and initializing and assessing morphological models. Four-dimensional multiview photogrammetry, also known as structure from motion (4D SfM), provides a method for generating three-dimensional reconstructions of landscapes at two times (before and after events) using only photos and existing information for ground control points. Here, these techniques were applied using National Oceanic and Atmospheric Administration (NOAA)-obtained oblique aerial photos taken before (2015) and immediately after Hurricane Matthew (2016) to assess coastal changes near Matanzas, Florida. This work demonstrated that 3D digital elevation models can be constructed within 48 hours of postevent photo collection without on-site ground control measurements. One advantage of timely SfM elevation-change assessments is that they avoid confusion of storm impacts with changes that occur after the event but before LIDAR surveys can be performed. The accuracy and precision of the 4D SfM maps were assessed a posteriori using the first-available LIDAR data, which were collected more than a month after the hurricane, and 11 independent ground-truth survey points measured a week after the hurricane. Horizontal coordinates of the 4D SfM reconstruction were biased by an average of 0.79 m (0.83 m root-mean-square difference; RMSD) compared with the ground-truth points, but vertical elevations were more accurate. They were biased from the LIDAR by −0.09 to −0.25 m, with ∼0.20 m RMSD from both the LIDAR data and five ground-truth points with good vertical positioning and 0.25 m RMSD from LIDAR data along a 60-m stretch of pavement. This level of precision was sufficient to quantify geomorphological change that was often in excess of 1 m. The methodology is conducive for rapid assessment of changes along short stretches (tens of kilometers) of coast with modest resources and could be scaled up for larger regions.

Florida↗
USGS2010

Geologic structure of the northern New Caledonia ridge, as inferred from magnetic and gravity anomalies

Bathymetric, gravity, and magnetic data collected in the southwest Pacific Ocean over the northern New Caledonia ridge show that the main geological units known from the island of New Caledonia extend northward from this island, beneath the Grand Lagon Nord, the Grand Passage, and the d'Entrecasteaux reefs. These data support the model of tectonic evolution of the New Caledonia region proposed by Kroenke [1984]. We interpret a linear axial gravity low that extends from southern New Caledonia to the Grand Passage as evidence for the continuity of the thick pre-Permian to Jurassic core of the island. The Belep magnetic pattern, which covers the southwestern half of the Grand Lagon Nord, shows linear, high relief (1000–2000 nT) anomalies that are locally associated with a 120-mGal gravity high. These magnetic and gravity anomalies resemble anomalies measured over the west coast of New Caledonia, suggesting that the Cretaceous to Eocene basaltic complex of the coastal area is overlain by ophiolite remnants as far north as the western d'Entrecasteaux reefs. The similarity between the Belep magnetic pattern and a highly magnetic province evident 200 km southwest across the New Caledonia basin, along the Fairway ridge, indicates that volcanic rocks lie symmetrically on both sides of the New Caledonia basin. We suggest that part of these volcanic rocks were emplaced during the middle Cretaceous when the New Caledonia ridge rifted from the Australian margin. Simple gravity models of an elongated gravity high, having peak values in the range of +130 to +150 mGal, suggest that the ophiolite, which was thrust over New Caledonia during the Upper Eocene, extends along the east side of the Grand Lagon Nord and as far north as the d'Entrecasteaux reefs. Gravity and magnetic models suggest that in the area of the d'Entrecasteaux reefs, the ophiolite belt includes two subunits. The first subunit underlies the Huon-La Surprise platform and may include highly serpentinized ultramafic rocks without basaltic oceanic crust. The second subunit, which lies beneath the Guilbert ridge, may include ultramafic rocks as well as thin imbricate slices of oceanic crust. At the northern termination of the New Caledonia ridge, seismic and geopotential data evidence a major east-west trending tectonic zone that separates the basement of the New Caledonia ridge from the d'Entrecasteaux zone, an arcuate oceanic feature extending northward from the ridge. Differences in structure, geophysical signatures and morphology evident between areas north and those south of the Grand Passage, together with the nearness of the Le Noroit massif west of the Grand Passage, suggest that contemporaneously with Eocene to early Oligocene subduction along the western New Caledonia margin, an arc-ridge collision may have occurred near the northern termination of this subduction zone.

Tectonics↗
USGS2010

Age and origin of Cretaceous planktonic foraminifers from limestone of the Franciscan Complex near Laytonville, California

Detailed planktonic foraminiferal biostratigraphy from eight measured sections of Cretaceous limestone near Laytonville, California, indicates a composite sequence that extends in age from late Albian to early Turonian. The sequence contains seven biozones and two subzones based on the first and last appearance datums of planktonic foraminifers examined in thin section. Unequivocal biostratigraphic facing directions show four sections are right side up and four are reversed, and confirm the stratigraphic polarity employed in the paleomagnetic studies of Alvarez et al. (1980) and Tarduno et al. (1986). Temporal changes in the microfauna deviate from the global trend. Early Albian through early Cenomanian planktonic foraminiferal assemblages dominated by opportunistic, eurytopic species of Hedbergella and Globigerinelloides give way in the late Cenomanian to assemblages containing more abundant larger, heavily ornamented stenotopic species of Rotalipora and Praeglobotruncana typical of stratified Tethyan oceans. Radiolarian replacement chert increases slightly in the late Albian to early Cenomanian part of the Laytonville sequence and then decreases in the late Cenomanian and early Turonian. Benthic foraminifers show a similar decrease in abundance and diversity. We propose that this complex of biogenic and lithogenic patterns records transit via oceanic plate motion from a depositional site in the southern part of the paleoequatorial zone of high productivity, characterized by pronounced upwelling and habitat destabilization, perhaps augmented by topographic upwelling, to the central part of the equatorial zone dominated by biogenic calcite deposition. Our model of northward transit from below the equator supports the paleomagnetic determinations of Alvarez et al. (1980) and Tarduno et al. (1986). Arrival at the paleoequator coincided with the onset of stratification in the world ocean during the middle Cenomanian, indicated by the diversification of the more complex rotaliporids, and the subsequent intensification of oxygen-depleted intermediate waters in the latest Cenomanian to early Turonian. Two pulses in heterohelicid abundance signify the onset or intensification of an oxygen-minimum layer if Cretaceous heterohelicids occupied habitats analagous to Tertiary biserial heterohelicids. The first pulse beginning in the middle Cenomanian Rotalipora reicheli Zone may indicate a minor expansion of the oxygen-minimum zone or regional upwelling due to transit of the site beneath the equatorial divergence. The second pulse in the late Cenomanian Dicarinella algeriana Subzone signals the onset of upwelling of deeper oceanic water masses that characterized the succeeding Whiteinella archaeocretacea Zone. Organic-rich black shales typical of the Whiteinella archaeocretacea Zone are missing at Laytonville, although samples do contain the low-diversity, partially dissolved, planktonic assemblages that characterize this zone. The lack of black shales suggests that deposition occurred at depths greater than the oxygen-depleted intermediate water depths or alternately indicates paleoceanographic conditions unique to the Pacific.

California↗
USGS2008

Satellite-derived aerosol radiative forcing from the 2004 British Columbia wildfires

The British Columbia wildfires of 2004 was one of the largest wildfire events in the last ten years in Canada. Both the shortwave and longwave smoke aerosol radiative forcing at the top-of-atmosphere (TOA) are investigated using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Clouds and the Earth's Radiant Energy System (CERES) instruments. Relationships between the radiative forcing fluxes (??F) and wildfire aerosol optical thickness (AOT) at 0.55 ??m (??0.55) are deduced for both noontime instantaneous forcing and diurnally averaged forcing. The noontime averaged instantaneous shortwave and longwave smoke aerosol radiative forcing at the TOA are 45.8??27.5 W m-2 and -12.6??6.9 W m-2, respectively for a selected study area between 62??N and 68??N in latitude and 125??W and 145??W in longitude over three mainly clear-sky days (23-25 June). The derived diurnally averaged smoke aerosol shortwave radiative forcing is 19.9??12.1 W m-2 for a mean ??0.55 of 1.88??0.71 over the same time period. The derived ??F-?? relationship can be implemented in the radiation scheme used in regional climate models to assess the effect of wildfire aerosols.

Atmosphere - Ocean↗
USGS2007

National volcanic ash operations plan for aviation

The National Aviation Weather Program Strategic Plan (1997) and the National Aviation Weather Initiatives (1999) both identified volcanic ash as a high-priority informational need to aviation services. The risk to aviation from airborne volcanic ash is known and includes degraded engine performance (including flameout), loss of visibility, failure of critical navigational and operational instruments, and, in the worse case, loss of life. The immediate costs for aircraft encountering a dense plume are potentially major—damages up to $80 million have occurred to a single aircraft. Aircraft encountering less dense volcanic ash clouds can incur longer-term costs due to increased maintenance of engines and external surfaces. The overall goal, as stated in the Initiatives, is to eliminate encounters with ash that could degrade the in-flight safety of aircrews and passengers and cause damage to the aircraft. This goal can be accomplished by improving the ability to detect, track, and forecast hazardous ash clouds and to provide adequate warnings to the aviation community on the present and future location of the cloud. To reach this goal, the National Aviation Weather Program established three objectives: (1) prevention of accidental encounters with hazardous clouds; (2) reduction of air traffic delays, diversions, or evasive actions when hazardous clouds are present; and (3) the development of a single, worldwide standard for exchange of information on airborne hazardous materials. To that end, over the last several years, based on numerous documents (including an OFCMsponsored comprehensive study on aviation training and an update of Aviation Weather Programs/Projects), user forums, and two International Conferences on Volcanic Ash and Aviation Safety (1992 and 2004), the Working Group for Volcanic Ash (WG/VA), under the OFCM-sponsored Committee for Aviation Services and Research, developed the National Volcanic Ash Operations Plan for Aviation and Support of the International Civil Aviation Organization’s (ICAO) International Airways Volcano Watch. This plan defines agency responsibilities, provides a comprehensive description of an interagency standard for volcanic ash products and their formats, describes the agency backup procedures for operational products, and outlines the actions to be taken by each agency following an occurrence of a volcanic eruption that subsequently affects and impacts aviation services. Since our most recent International Conference on Volcanic Ash and Aviation Safety, volcanic ash-related product and service activities have grown considerably along with partnerships and alliances throughout the aviation community. In January 2005, the National Oceanic and Atmospheric Administration’s National Centers for Environment Prediction began running the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model in place of the Volcanic Ash Forecast Transport and Dispersion (VAFTAD) model, upgrading support to the volcanic ash advisory community. Today, improvements to the HYSPLIT model are ongoing based on recommendations by the OFCM-sponsored Joint Action Group for the Selection and Evaluation of Atmospheric Transport and Diffusion Models and the Joint Action Group for Atmospheric Transport and Diffusion Modeling (Research and Development Plan). Two international workshops on volcanic ash have already taken place, noticeable improvements and innovations in education, training, and outreach have been made, and federal and public education and training programs on volcanic ash-related products, services, and procedures iv continue to evolve. For example, in partnership with Embry-Riddle Aeronautical University and other academic institutions, volcanic ash hazard and mitigation training has been incorporated into aviation meteorology courses. As an essential next step, our volcanic ash-related efforts in the near term will be centered on the development of an interagency implementation plan to document and address the most critical needs of the volcanic ash advisory community. This interagency plan, developed as the result of the cooperative efforts of six federal agencies, follows the guidelines in support of the ICAO International Airways Volcano Watch. The signatories on the next page are committed to volcanic ash operations for aviation and will work toward full implementation through agency programs, initiatives, and procedures. I extend my sincere thanks to all members of the WG/VA, subject-matter experts, and to my staff for their collaborative and cooperative efforts in developing this first-ever national volcanic ash operations plan.

Report↗
USGS1981

Tectonic elements of the southern part of the Gulf of California

Closely spaced seismic and bathymetric surveys in the southern province of the Gulf of California reveal a tectonically active and structurally complex plate boundary. While heat-flow measurements, seismicity, large sediment accumulations on continental margins, and the presence of oceanic crust in deep basins strongly suggest divergent plate motion, magnetic anomaly patterns are conspicuously absent in the Gulf as a whole. The rate of sediment accumulation (range: 6-1,000 m/m.y.), however, provides an alternative for the differentiation of two types of fault traces and suggests a process by which recently formed plate boundary zones evolve. Active faults manifest themselves as steep, elongate scarps delineating the active plate boundary zone. These fault traces appear to converge and diverge, for example in the Pescadero Basin complex, in a manner similar to the Southern California borderland. The floors of the intervening basins are flat and relatively sediment free. Relict faults, also elongate fracture zones, are distinguished from active traces in that they are completely filled with hemipelagic muds. The relict faults are located along both sides of the active plate boundary zone and subparallel to it. These features infer that plate motion is relatively rapid, thus explaining the paucity of sediment accumulation in actively spreading basins in spite of high sedimentation rates. Substantial plate boundary readjustment in short time periods is suggested by the periodic abandoment and subsequent infilling and attachment of formerly active transform faults to the more stable margins of the plates involved. The Gulf of California, therefore, represents a working model of the evolution of a plate boundary and its sedimentological consequences in the early tectonic developmental stage of a passive margin ocean basin such as the Atlantic.

southern Gulf of California↗
USGS2023

A life cycle model for evaluating estuary residency and restoration potential in Chinook salmon

Understanding the spatial and temporal habitat use of a population is a necessary step for recovery planning. For Chinook salmon ( Oncorhynchus tshawytscha ), variation in their migration and habitat use complicate predicting how restoring habitats could impact total recruitment. To evaluate how juvenile life history variation affects a population’s response to potential restoration, we developed a stage-structured model for a Chinook salmon population in a northern California river with a seasonally closed estuary. We modeled the timing of juvenile migration and estuarine use as a function of freshwater conditions and fish abundance. We used the model to evaluate the sensitivity of the population to different estuary and freshwater restoration scenarios that could affect population parameters at different life stages. The population’s run size increased most in response to freshwater restoration that enhanced spawning productivity (egg and fry survival), followed by spawner capacity. In contrast, estuary restoration scenarios affected only a subset of Chinook salmon (average 15%), and as a result, did not have a large impact on the total recruitment of a cohort. Under current condition, estuary rearing fish were over six times less likely to survive than fish that migrate to the ocean in the spring or early summer before estuary closure. Because estuary residents experienced low survival in the estuary and in the ocean, improvements to both estuary survival and growth would be needed to increase their total survival. When life cycle monitoring data is available, life cycle models such as ours generate predictions at scales relevant to conservation and are an advantageous approach to managing and conserving anadromous salmon that use multiple habitats throughout their life cycle.

California↗
USGS2008

Extreme changes in stable hydrogen isotopes and precipitation characteristics in a landfalling Pacific storm

With a new automated precipitation collector we measured a remarkable decrease of 51??? in the hydrogen isotope ratio (?? 2H) of precipitation over a 60-minute period during the landfall of an extratropical cyclone along the California coast on 21 March 2005. The rapid drop in ??2H occurred as precipitation generation transitioned from a shallow to a much deeper cloud layer, in accord with synoptic-scale ascent and deep "seeder-feeder" precipitation. Such unexpected ?? 2H variations can substantially impact widely used isotope-hydrograph methods. From extreme ??2H values of -26 and -78???, we calculate precipitation temperatures of 9.7 and -4.2??C using an adiabatic condensation isotope model, in good agreement with temperatures estimated from surface observations and radar data. This model indicates that 60 percent of the moisture was precipitated during ascent as temperature decreased from 15??C at the ocean surface to -4??C above the measurement site.

Geophysical Research Letters↗
USGS2010

The California current of the last glacial maximum: reconstruction at 42°N based on multiple proxies

Multiple paleoceanographic proxies in a zonal transect across the California Current near 42°N record modern and last glacial maximum (LGM) thermal and nutrient gradients. The offshore thermal gradient, derived from foraminiferal species assemblages and oxygen isotope data, was similar at the LGM to that at present (warmer offshore), but average temperatures were 3.3° ±1.5°C colder. Observed gradients require that the sites remained under the southward flow of the California Current, and thus that the polar front remained north of 42°N during the LGM. Carbon isotopic and foraminiferal flux data suggests enhanced nutrients and productivity of foraminfera in the northern California Current up to 650 km offshore. In contrast, marine organic carbon and coastal diatom burial rates decreased during the LGM. These seemingly contradictory results are reconciled by model simulations of the LGM wind- field, which suggest that wind stress curl at 42°N (and thus open-ocean upwelling) increased, while offshore Ekman transport (and thus coastal upwelling) decreased during the last ice age. The ecosystem of the northern California Current during the LGM approximated that of the modern Gulf of Alaska. Cooling and production in this region was thus driven by stronger open-ocean upwelling and/or southward flow of high-latitude water masses, rather than by coastal upwelling.

Paleoceanography↗
USGS1969

The structure and tectonic history of the eastern Aleutian Trench

The tectonic character of the eastern Aleutian Trench and some major events in its geologic history can be estimated from nine continuous seismic reflection records. A section of pre-trench, deep oceanic sediments rests on the down-warped crust that forms the trench. Nearly horizontal undeformed strata that unconformably overlie this deep oceanic section partially fill the trench. The trench fill is thickest near present sediment sources. A Pliocene age for development of the eastern Aleutian Trench is estimated from the thickness of deep oceanic sediment that accumulated after the trench began to fill. The eastern Aleutian Trench thus appears younger than the central Aleutian Trench—a relation which helps to explain the distribution of sediment along the two trench segments. Depression of the eastern Aleutian Trench diminished or virtually ended soon after the trench began to fill. The undeformed fill provides no evidence for a large thrust fault zone at the base of the continental slope. Nor is there any evidence that oceanic sediments have disappeared beneath the continents in late Tertiary time. These observations are difficult to reconcile with the simple model of a continental margin advanced in the hypothesis of plate tectonics.

Alaska↗
USGS1979

Palladium, platinum, and rhodium concentrations in mafic and ultramafic rocks from the Kizildag and Guleman areas, Turkey, and the Faryab and Esfandagheh-Abdasht areas, Iran

The Kizildag and Guleman areas, Turkey, and the Faryab and Esfandagheh-Abdasht areas, Iran, have produced chromite from ophiolite complexes consisting of harzburgite tectonite, dunite tectonite containing chromitite, pyroxenite, wehrlite, and gabbro. Forty-six samples from these complexes were analyzed in order to investigate the possibility of platinum-group metals being present that could be produced as byproducts. The results, however, indicate concentrations of palladium, platinum, and rhodium ranging up to 46 ppb (parts per billion), 55 ppb, and 24 ppb, respectively. The concentration levels and ratios of these metals are similar to other alpine ultramafic bodies that have been analyzed by modern analytical techniques. Ten samples from massive sulfide deposits in the Gunes and Ergani-Maden areas, Turkey, and the Sheikh Ali mine, Iran, were analyzed also. The results of the analysis suggests a low potential for byproduct palladium, platinum, and rhodium production in these ophiolite-associated massive sulfide deposits. The four ultramafic and mafic areas in Turkey and Iran under consideration have, and are, producing in 1978 chromite from podiform chromitites in alpine-type complexes. Because of the known association of chromitites and platinum-group metals, a collection of chromitites was made to check their palladium, platinum, and rhodium content to determine if economic concentrations might exist. Also, inasmuch as such rocks are thought to represent parts of the oceanic crust and upper mantle, data on platinum-group elements from these rocks can provide information to design geochemical models for the distribution of these elements. During the field excursions of the CENTO Working Group on Volcanic and Intrusive Rocks and Their Associated Ore Deposits, the Kizildag and Gunes areas, Turkey, were sampled in 1974 and the Guleman area, Turkey; Faryab and Esfandagheh-Abdasht areas, Iran, were sampled in 1975. In addition, samples of massive sulfide ores from the Ergani-Maden area, Turkey, were also collected for analysis, and the results included here. In this report the geologic framework of these areas is briefly examined as a background for interpreting the concentrations of palladium, platinum, and rhodium in the chromitites and ultramafic and mafic rocks. Comparisons of these analyses with analyses from other areas containing similar rocks show few differences in concentration or proportions of these three platinum-group metals.

Open-File Report↗
USGS1998

Ice sheet history from Antarctic Continental Margin sediments: The ANTOSTRAT approach

The Antarctic Ice Sheet is today an important part of the global climate engine, and probably has been so for most of its long existence. However, the details of its history are poorly known, despite the measurement and use, over two decades, of low-latitude proxies of ice sheet volume. An additional way of determining ice sheet history is now available, based on understanding terrigenous sediment transport and deposition under a glacial regime. It requires direct sampling of the prograded wedge of glacial sediments deposited at the Antarctic continental margin (and of derived sediments on the continental rise) at a small number of key sites, and combines the resulting data using numerical models of ice sheet development. The new phase of sampling is embodied mainly in a suite of proposals to the Ocean Drilling Program, generated by separate regional proponent groups co-ordinated through ANTOSTRAT (the Antarctic Offshore Acoustic Stratigraphy initiative). The first set of margin sites has now been drilled as ODP Leg 178 to the Antarctic Peninsula margin, and a first, short season of inshore drilling at Cape Roberts, Ross Sea, has been completed. Leg 178 and Cape Roberts drilling results are described briefly here, together with an outline of key elements of the overall strategy for determining glacial history, and of the potential contributions of drilling other Antarctic margins investigated by ANTOSTRAT. ODP Leg 178 also recovered continuous ultra-high-resolution Holocene biogenic sections at two sites within a protected, glacially-overdeepened basin (Palmer Deep) on the inner continental shelf of the Antarctic Peninsula. These and similar sites from around the Antarctic margin are a valuable resource when linked with ice cores and equivalent sections at lower latitude sites for studies of decadal and millenial-scale climate variation.

Terra Antarctica↗
USGS2023

Central Beaufort Sea Wave and Hydrodynamic Modeling Study--Report 1: Field measurements and model development

Renewed interest in nearshore oil exploration and production in the shallow waters of the Central Beaufort Sea Shelf has created a need to advance our understanding of the past, current, and future atmospheric and oceanographic conditions that affect existing and planned infrastructure and nearshore ecosystems. At the time of writing this report, Hilcorp Alaska, LLC, has received BOEM approval for an oil and gas Development and Production Plan (DPP) that includes the construction of the Liberty Drilling Island (LDI) in Foggy Island Bay, situated within Stefansson Sound circa 30 km east of Prudhoe Bay (Figure 1.1). The aim of this study is to investigate how longer periods of open water (defined as < 15% ice cover), decreased sea ice cover, and changes in ocean and atmospheric conditions might affect wave and storm surge conditions, sediment transport patterns, and coastal erosion rates within Foggy Island Bay as well as the modeled influence of the offshore artificial island on sediment transport patterns.

Foggy Island Bay↗
USGS2020

Influence of niche breadth and position on the historical biogeography of seafaring scincid lizards

Niche breadth and position can influence diversification among closely related species or populations, yet limited empirical data exist concerning the predictability of the outcomes. We explored the effects of these factors on the evolution of the Emoia atrocostata species group, an insular radiation of lizards in the western Pacific Ocean and Indo-Australasia composed of both endemic and widespread species that differ in niche occupancy. We used molecular data and phylogeographical diffusion models to estimate the timing and patterns of range expansion, and ancestral reconstruction methods to infer shifts in ecology. We show evidence of multidirectional spread from a centre of origin in western Micronesia, and that the phyletic diversity of the group is derived from a putative habitat specialist that survives in the littoral zone. This species is composed of paraphyletic lineages that represent stages or possible endpoints in the continuum toward speciation. Several descendant species have transitioned to either strand or interior forest habitat, but only on remote islands with depauperate terrestrial faunas. Our results suggest that the atrocostata group might be in the early phases of a Wilsonian taxon cycle and that the capacity to tolerate salt stress has promoted dispersal and colonization of remote oceanic islands. Divergence itself, however, is largely driven by geographical isolation rather than shifts in ecology.

Biological Journal of the Linnean Society↗
USGS2009

Monitoring and modeling shoreline response due to shoreface nourishment on a high-energy coast

Shoreface nourishment can be an efficient technique to feed sediment into the littoral zone without the order of magnitude cost increase incurred by directly nourishing the beach. An erosion hot spot at Ocean Beach in San Francisco, California, USA, threatens valuable public infrastructure as well as safe recreational use of the beach. In an effort to reduce the erosion at this location, a new beneficial reuse plan was implemented in May 2005 for the sediment dredged annually from the main shipping channel at the mouth of San Francisco Bay. From 2005 to 2007, approximately 230,000 m of sand was placed annually at depths between 9 and 14 m, in a location where strong tidal currents and open-ocean waves could potentially feed sediment onto the section of beach experiencing critical erosion. The evolution of the disposal mound and adjacent beach were monitored with 12 multibeam bathymetric surveys, and over 40 high-resolution beach topographic surveys. In addition, sediment transport processes were investigated using sediment grab samples, acoustic Doppler profilers, and two separate models: a cross-shore profile model (UNIBEST-TC) and a coastal area model (Delft3D). The results of the monitoring and modeling demonstrate that the disposal mound may be effective in dissipating wave energy striking this vulnerable stretch of coast with negligible shadowing effects, but a positive shoreline response can only be achieved by placing the sediment in water depths less than 5 m.

California↗
USGS2015

Transdisciplinary science: A path to understanding the interactions among ocean acidification, ecosystems, and society

The global nature of ocean acidification (OA) transcends habitats, ecosystems, regions, and science disciplines. The scientific community recognizes that the biggest challenge in improving understanding of how changing OA conditions affect ecosystems, and associated consequences for human society, requires integration of experimental, observational, and modeling approaches from many disciplines over a wide range of temporal and spatial scales. Such transdisciplinary science is the next step in providing relevant, meaningful results and optimal guidance to policymakers and coastal managers. We discuss the challenges associated with integrating ocean acidification science across funding agencies, institutions, disciplines, topical areas, and regions, and the value of unifying science objectives and activities to deliver insights into local, regional, and global scale impacts. We identify guiding principles and strategies for developing transdisciplinary research in the ocean acidification science community.

Oceanography↗