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At least 757 records · Page 42Linked to original sources
USGS2025

Reconciliation of geochronology and paleozoogeography for Quaternary marine terraces, San Luis Obispo Bay area, California, USA

In the San Luis Obispo Bay area of central California, interpretations of marine terrace ages have been hampered by inconsistent results from geochronological indicators (U-series ages of corals and correlations using amino acid racemization of mollusks) and seemingly contradictory paleozoogeographic aspects of fossil faunal assemblages. New U-series ages of corals, amino acid data from mollusks, and detailed analyses of fossil mollusk assemblages are presented that reconcile many of the apparently discordant results from previous studies. The two lowest-elevation terraces are Q1 (lower) and Q2 (upper); both are thought to date from high-sea stands of marine isotope stage (MIS) 5, the last interglacial complex. A combination of U-series dating and amino acid racemization results indicates that the Q1 terrace probably dates to the ∼80 ka high-sea stand of MIS 5a. U-series analyses of corals from the Q2 terrace show open-system histories, but consideration of two alternative open-system histories indicates that this terrace likely hosts corals dating to the high-sea stands of MIS 5c (∼105–95 ka) and MIS 5e (∼130–115 ka). Amino acid ratios in the fossil bivalve Leukoma staminea (Conrad, 1837) support the age differences between the two terraces and the open-system models suggested by the U-series data. Alkenone studies along much of the coast of California have shown that sea surface temperatures (SSTs) of the eastern Pacific Ocean were warmer than present during MIS 5e. During MIS 5c, on the other hand, SSTs were either similar to the present or cooler, but in either case, much cooler than during MIS 5e. The paleozoogeographic aspects of the molluscan faunas from the Q2 terrace support an interpretation that these deposits contain a mixture of fossils from both the MIS 5c and 5e high-sea stands. Fossils from the Q2 terrace include southern or southward-ranging species (likely dating to MIS 5e) and northern or northward-ranging species (likely dating to MIS 5c). A mixture of MIS 5e and MIS 5c fossils on the Q2 terrace is consistent with similar data reported for other localities in California. This phenomenon is explained by glacial isostatic adjustment (GIA) processes, which brought about a higher-than-present sea level during MIS 5c. GIA processes, combined with a low uplift rate, allowed mixing of MIS 5e fossils during the MIS 5c high-sea stand through capture of an MIS 5e terrace that had experienced minimal uplift in ∼20,000 years. Terrace reoccupation and fossil mixing such as that in the San Luis Obispo Bay area can be expected along any part of the Pacific Coast of North America that was affected by GIA processes and where uplift rates are low.

California↗
USGS2004

The effects of mixotrophy on the stability and dynamics of a simple planktonic food web

Recognition of the microbial loop as an important part of aquatic ecosystems disrupted the notion of simple linear food chains. However, current research suggests that even the microbial loop paradigm is a gross simplification of microbial interactions due to the presence of mixotrophs—organisms that both photosynthesize and graze. We present a simple food web model with four trophic species, three of them arranged in a food chain (nutrients–autotrophs–herbivores) and the fourth as a mixotroph with links to both the nutrients and the autotrophs. This model is used to study the general implications of inclusion of the mixotrophic link in microbial food webs and the specific predictions for a parameterization that describes open ocean mixed layer plankton dynamics. The analysis indicates that the system parameters reside in a region of the parameter space where the dynamics converge to a stable equilibrium rather than displaying periodic or chaotic solutions. However, convergence requires weeks to months, suggesting that the system would never reach equilibrium in the ocean due to alteration of the physical forcing regime. Most importantly, the mixotrophic grazing link seems to stabilize the system in this region of the parameter space, particularly when nutrient recycling feedback loops are included.

Theoretical Population Biology↗
USGS2014

Termini of calving glaciers as self-organized critical systems

Over the next century, one of the largest contributions to sea level rise will come from ice sheets and glaciers calving ice into the ocean 1 . Factors controlling the rapid and nonlinear variations in calving fluxes are poorly understood, and therefore difficult to include in prognostic climate-forced land-ice models. Here we analyse globally distributed calving data sets from Svalbard, Alaska (USA), Greenland and Antarctica in combination with simulations from a first-principles, particle-based numerical calving model to investigate the size and inter-event time of calving events. We find that calving events triggered by the brittle fracture of glacier ice are governed by the same power-law distributions as avalanches in the canonical Abelian sandpile model 2 . This similarity suggests that calving termini behave as self-organized critical systems that readily flip between states of sub-critical advance and super-critical retreat in response to changes in climate and geometric conditions. Observations of sudden ice-shelf collapse and tidewater glacier retreat in response to gradual warming of their environment 3 are consistent with a system fluctuating around its critical point in response to changing external forcing. We propose that self-organized criticality provides a yet unexplored framework for investigations into calving and projections of sea level rise.

Nature Geoscience↗
USGS2010

Thermochronology and tectonics of the Leeward Antilles: Evolution of the southern Caribbean Plate boundary zone

Tectonic reconstructions of the Caribbean Plate are severely hampered by a paucity of geochronologic and exhumation constraints from anastomosed basement blocks along its southern margin. New U/Pb, 40 Ar/ 39 Ar, apatite fission track, and apatite (U-Th)/He data constrain quantitative thermal and exhumation histories, which have been used to propose a model for the tectonic evolution of the emergent parts of the Bonaire Block and the southern Caribbean Plate boundary zone. An east facing arc system intruded through an oceanic plateau during ~90 to ~87 Ma and crops out on Aruba. Subsequent structural displacements resulted in >80°C of cooling on Aruba during 70–60 Ma. In contrast, exhumation of the island arc sequence exposed on Bonaire occurred at 85–80 Ma and 55–45 Ma. Santonian exhumation on Bonaire occurred immediately subsequent to burial metamorphism and may have been driven by the collision of a west facing island arc with the Caribbean Plate. Island arc rocks intruded oceanic plateau rocks on Gran Roque at ~65 Ma and exhumed rapidly at 55–45 Ma. We attribute Maastrichtian-Danian exhumation on Aruba and early Eocene exhumation on Bonaire and Gran Roque to sequential diachronous accretion of their basement units to the South American Plate. Widespread unconformities indicate late Eocene subaerial exposure. Late Oligocene–early Miocene dextral transtension within the Bonaire Block drove subsidence and burial of crystalline basement rocks of the Leeward Antilles to ≤1 km. Late Miocene–recent transpression caused inversion and ≤1 km of exhumation, possibly as a result of the northward escape of the Maracaibo Block.

Tectonics↗
USGS2011

Natural radium and radon tracers to quantify water exchange and movement in reservoirs

Radon and radium isotopes are routinely used to quantify exchange rates between different hydrologic reservoirs. Since their recognition as oceanic tracers in the 1960s, both radon and radium have been used to examine processes such as air-sea exchange, deep oceanic mixing, benthic inputs, and many others. Recently, the application of radon-222 and the radium-quartet (223,224,226,228Ra) as coastal tracers has seen a revelation with the growing interest in coastal groundwater dynamics. The enrichment of these isotopes in benthic fluids including groundwater makes both radium and radon ideal tracers of coastal benthic processes (e.g. submarine groundwater discharge). In this chapter we review traditional and recent advances in the application of radon and radium isotopes to understand mixing and exchange between various hydrologic reservoirs, specifically: (1) atmosphere and ocean, (2) deep and shallow oceanic water masses, (3) coastal groundwater/benthic pore waters and surface ocean, and (4) aquifer-lakes. While the isotopes themselves and their distribution in the environment provide qualitative information about the exchange processes, it is mixing/exchange and transport models for these isotopes that provide specific quantitative information about these processes. Brief introductions of these models and mixing parameters are provided for both historical and more recent studies.

Book chapter↗
USGS2006

Photometric properties of Titan's surface from Cassini VIMS: Relevance to titan's hemispherical albedo dichotomy and surface stability

The Visual and Infrared Mapping Spectrometer (VIMS) instrument on the Cassini Saturn Orbiter returned spectral imaging data as the spacecraft undertook six close encounters with Titan beginning 7 July, 2004. Three of these flybys each produced overlapping coverage of two distinct regions of Titan's surface. Twenty-four points were selected on approximately opposite hemispheres to serve as photometric controls. Six points were selected in each of four reflectance classes. On one hemisphere each control point was observed at three distinct phase angles. From the derived phase coefficients, preliminary normal reflectances were derived for each reflectance class. The normal reflectance of Titan's surface units at 2.0178 ??m ranged from 0.079 to 0.185 for the most absorbing to the most reflective units assuming no contribution from absorbing haze. When a modest haze contribution of ??=0.1 is considered these numbers increase to 0.089-0.215. We find that the lowest three reflectance classes have comparable normal reflectance on either hemisphere. However, for the highest brightness class the normal reflectance is higher on the hemisphere encompassing longitude 14-65?? compared to the same high brightness class for the hemisphere encompassing 122-156?? longitude. We conclude that an albedo dichotomy observed in continental sized units on Titan is due not only to one unit having more areal coverage of reflective material than the other but the material on the brighter unit is intrinsically more reflective than the most reflective material on the other unit. This suggests that surface renewal processes are more widespread on Titan's more reflective units than on its less reflective units. We note that one of our photometric control points has increased in reflectance by 12% relative to the surrounding terrain from July of 2004 to April and May of 2005. Possible causes of this effect include atmospheric processes such as ground fog or orographic clouds; the suggestion of active volcanism cannot be ruled out. Several interesting circular features which resembled impact craters were identified on Titan's surface at the time of the initial Titan flyby in July of 2004. We traced photometric profiles through two of these candidate craters and attempted to fit these profiles to the photometric properties expected from model depressions. We find that the best-fit attempt to model these features as craters requires that they be unrealistically deep, approximately 70 km deep. We conclude that despite their appearance, these circular features are not craters, however, the possibility that they are palimpsests cannot be ruled out. We used two methods to test for the presence of vast expanses of liquids on Titan's surface that had been suggested to resemble oceans. Specular reflection of sunlight would be indicative of widespread liquids on the surface; we found no evidence of this. A large liquid body should also show uniformity in photometric profile; we found the profiles to be highly variable. The lack of specular reflection and the high photometric variability in the profiles across candidate oceans is inconsistent with the presence of vast expanses of flat-lying liquids on Titan's surface. While liquid accumulation may be present as small, sub-pixel-sized bodies, or in areas of the surface which still remain to be observed by VIMS, the presence of large ocean-sized accumulations of liquids can be ruled out. The Cassini orbital tour offers the opportunity for VIMS to image the same parts of Titan's surface repeatedly at many different illumination and observation geometries. This creates the possibility of understanding the properties of Titan's atmosphere and haze by iteratively adapting models to create a best fit to the surface reflectance properties. ?? 2006 Elsevier Ltd. All rights reserved.

Planetary and Space Science↗
USGS1974

Tectonic evolution of the southern Gulf of Mexico

A detailed magnetic survey in the southern Gulf of Mexico shows subdued irregular magnetic anomalies that are similar in wave length to those attributed to sea-floor spreading on present-day oceanic rises. The small amplitude of these anomalies, about 75γ, would be compatible with an oceanic basalt source at a depth of 10 km, and previous seismic refraction studies in this area have shown that layer 2 of the oceanic crust (presumed to be basalt) does indeed lie at approximately that depth. Palynomorphs in Deep Sea Drilling Project samples of cap-rock material from the Sigsbee Knolls have shown the associated salt to be Jurassic. A crustal model, based on seismic refraction evidence and on new gravity data, suggests that, whereas the salt-dome belt of the southern gulf is underlain by a thick layer with a density of 2.2 g per cm 3 (presumed to be halite rock), adjacent deeper areas of the basin seem to lack this low density layer. In northeastern Mexico, Triassic red beds fill grabens that are correlative with the Newark Group of the Atlantic Coast and suggest that the Gulf of Mexico originated at the time of the initial rifting of the North Atlantic. When the gulf was about half-opened during the Jurassic, oceanic circulation was restricted; and thick deep-basin evaporite deposits, analogous to those found in the Mediterranean Sea by the Deep Sea Drilling Project, were laid down. Further opening established normal salinity and led to the development of salt-free areas of oceanic crust that separated the Sigsbee Escarpment (together with adjacent ridges of offshore Mexico) from the Sigsbee Knolls and salt domes of Cuba. The subsequent structural evolution of the Gulf of Mexico basin is believed to have been mainly a result of interaction between it and tectonic plates of the Pacific area. After opening of the gulf, subduction began along the Cuban arc, where Atlantic rifting had created a nearly uninterrupted tract of oceanic crust extending from the Pacific between Yucatán and Colombia. Then, folding and gravity sliding associated with Laramide deformation on the west side of the gulf led to salt anticlines that underlie the ridges offshore from Mexico. Except for continued diapirism and subsidence associated with sediment loading, present tectonic activity is confined to the southwestern corner of the gulf, where volcanism and intermediate-focus earthquakes are a distant manifestation of subduction along the Middle America Trench on the Pacific side of Mexico.

Gulf of Mexico↗
USGS2016

Predictive mapping of seabirds, pinnipeds and cetaceans off the Pacific Coast of Washington

About this report This report supports Washington-led marine spatial planning and responsible stewardship of natural and cultural resources by the Olympic Coast National Marine Sanctuary. Washington state agencies and the sanctuary continually seek the best available science to improve management of marine uses and stewardship of resources (Etheridge et al., 2010; Washington Department of Fish and Wildlife, 2015a). This report and associated data provide new, state- and sanctuary-requested information on seabird, pinniped, and cetacean distributions. Through spatial planning, information on species distributions can help to identify high-value conservation areas, minimize adverse effects of ocean uses and mitigate impacts of coastal hazards. Correspondingly, the Washington Department of Fish and Wildlife has already begun to use the maps of predicted relative density presented in this report to identify ecologically important areas off the Pacific Coast of Washington and apply this information to plan for offshore renewable energy development. This is the culmination of three years of work to compile information on seabirds, pinnipeds, and cetaceans, and advance a modeling framework that can integrate data sets and develop accurate predictions of relative density for important species off the Pacific Coast of Washington. Previous reports, which evaluated existing datasets of at-sea observations (Menza et al., 2014; Kracker and Menza, 2015) and presented superseded versions of seabird models (Menza et al., 2015), provided base information for this report. In addition to the maps in this published report, all new seabird, pinniped and cetacean predictions will be made publicly available as digital geospatial data through the National Centers for Environmental Information. This research supports the National Oceanic and Atmospheric Administration (NOAA) Coastal Zone Management Program, a voluntary partnership between the federal government and U.S. coastal and Great Lakes states and territories authorized by the Coastal Zone Management Act (CZMA) of 1972 to address national coastal issues. The act provides the basis for protecting, restoring, and responsibly developing our nation’s diverse coastal communities and resources. To meet the goals of the CZMA, the national program takes a comprehensive approach to coastal resource management – balancing the often competing and occasionally conflicting demands of coastal resource use, economic development, and conservation. A wide range of issues are addressed through the program, including coastal development, water quality, public access, habitat protection, energy facility siting, ocean governance and planning, coastal hazards, and climate change. Accurate maps of seabird and marine mammal distributions are an important tool for making informed management decisions that affect all of these issues.

Washington↗
USGS2016

Intertidal salt marshes as an important source of inorganic carbon to the coastal ocean

Dynamic tidal export of dissolved inorganic carbon (DIC) to the coastal ocean from highly productive intertidal marshes and its effects on seawater carbonate chemistry are thoroughly evaluated. The study uses a comprehensive approach by combining tidal water sampling of CO 2 parameters across seasons, continuous in situ measurements of biogeochemically-relevant parameters and water fluxes, with high-resolution modeling in an intertidal salt marsh of the U.S. northeast region. Salt marshes can acidify and alkalize tidal water by injecting CO 2 (DIC) and total alkalinity (TA). DIC and TA generation may also be decoupled due to differential effects of marsh aerobic and anaerobic respiration on DIC and TA. As marsh DIC is added to tidal water, the buffering capacity first decreases to a minimum and then increases quickly. Large additions of marsh DIC can result in higher buffering capacity in ebbing tide than incoming tide. Alkalization of tidal water, which mostly occurs in the summer due to anaerobic respiration, can further modify buffering capacity. Marsh exports of DIC and alkalinity may have complex implications for the future, more acidified ocean. Marsh DIC export exhibits high variability over tidal and seasonal cycles, which is modulated by both marsh DIC generation and by water fluxes. The marsh DIC export of 414 g C m −2 yr −1 , based on high-resolution measurements and modeling, is more than twice the previous estimates. It is a major term in the marsh carbon budget and translates to one of the largest carbon fluxes along the U.S. East Coast.

Massachusetts↗
USGS2025

Surface-wave relocation and characterization of the October 2023 tsunamigenic seismic unrest near Sofugan volcano, Izu Islands, Japan

A moderate-magnitude earthquake swarm occurred in the remote Izu Islands region of Japan between October 1 and 8, 2023. The swarm included 151 shallow earthquakes cataloged by the U.S. Geological Survey, which notably included a roughly 2.5-hr episode of 15 successive magnitude (M) < 5.5 earthquakes. Origin times were coincident with regionally recorded tsunami waves, but tsunamigenesis for moderate-magnitude earthquakes is uncommon, indicating that volcanic activity generated the ocean displacements. Leveraging a surface-wave relative relocation approach, we estimate precise epicentroid locations for the remote swarm. Final epicentroids and caldera analogs indicate a three-stage model to explain swarm activity: (a) caldera pressurization due to magma intrusion, (b) depressurization via dike propagation away from the caldera, and (c) eruption corresponding with caldera reactivation either by collapse or additional intrusion.

Sofugan volcano, Izu Islands↗
USGS2011

Projected changes to growth and mortality of Hawaiian corals over the next 100 years

Background: Recent reviews suggest that the warming and acidification of ocean surface waters predicated by most accepted climate projections will lead to mass mortality and declining calcification rates of reef-building corals. This study investigates the use of modeling techniques to quantitatively examine rates of coral cover change due to these effects. Methodology/Principal Findings: Broad-scale probabilities of change in shallow-water scleractinian coral cover in the Hawaiian Archipelago for years 2000-2099 A.D. were calculated assuming a single middle-of-the-road greenhouse gas emissions scenario. These projections were based on ensemble calculations of a growth and mortality model that used sea surface temperature (SST), atmospheric carbon dioxide (CO2), observed coral growth (calcification) rates, and observed mortality linked to mass coral bleaching episodes as inputs. SST and CO2 predictions were derived from the World Climate Research Programme (WCRP) multi-model dataset, statistically downscaled with historical data. Conclusions/Significance: The model calculations illustrate a practical approach to systematic evaluation of climate change effects on corals, and also show the effect of uncertainties in current climate predictions and in coral adaptation capabilities on estimated changes in coral cover. Despite these large uncertainties, this analysis quantitatively illustrates that a large decline in coral cover is highly likely in the 21st Century, but that there are significant spatial and temporal variances in outcomes, even under a single climate change scenario.

PLoS ONE↗
USGS2014

Remediation scenarios for attenuating peak flows and reducing sediment transport in Fountain Creek, Colorado, 2013

The U.S. Geological Survey (USGS) in cooperation with the Fountain Creek Watershed, Flood Control and Greenway District assessed remediation scenarios to attenuate peak flows and reduce sediment loads in the Fountain Creek watershed. To evaluate these strategies, the U.S. Army Corps of Engineers Hydrologic Engineering Center (HEC) hydrologic and hydraulic models were employed. The U.S. Army Corps of Engineers modeling system HEC-HMS (Hydrologic Modeling System) version 3.5 was used to simulate runoff in the Fountain Creek watershed, Colorado, associated with storms of varying magnitude and duration. Rain-gage precipitation data and radar-based precipitation data from the April 28–30, 1999, and September 14–15, 2011, storm events were used in the calibration process for the HEC-HMS model. The curve number and lag time for each subwatershed and Manning's roughness coefficients for each channel reach were adjusted within an acceptable range so that the simulated and measured streamflow hydrographs for each of the 12 USGS streamgages approximated each other. The U.S. Army Corps of Engineers modeling system HEC-RAS (River Analysis System) versions 4.1 and 4.2 were used to simulate streamflow and sediment transport, respectively, for the Fountain Creek watershed generated by a particular storm event. Data from 15 USGS streamgages were used for model calibration and 7 of those USGS streamgages were used for model validation. The calibration process consisted of comparing the simulated water-surface elevations and the cross-section-averaged velocities from the model with those surveyed in the field at the cross section at the corresponding 15 and 7 streamgages, respectively. The final Manning’s roughness coefficients were adjusted between –30 and 30 percent at the 15 calibration streamgages from the original left, right, and channel-averaged Manning's roughness coefficients upon completion of calibration. The U.S. Army Corps of Engineers modeling system HEC-RAS version 4.2 was used to simulate streamflow and sediment transport for the Fountain Creek watershed generated by a design-storm event. The Laursen-Copeland sediment-transport function was used in conjunction with the Exner 5 sorting method and the Ruby fall-velocity method to predict sediment transport. Six USGS streamgages equipped with suspended-sediment samplers were used to develop sediment-flow rating curves for the sediment-transport-model calibration. The critical Shields number in the Laursen-Copeland sediment-transport function and the volume of sediment available at a given cross section were adjusted during the HEC-RAS sediment-model calibration process. HEC-RAS model simulations used to evaluate the 14 remediation scenarios were based on unsteady-state streamflows associated with a 24-hour, 1-percent annual exceedance probability (100-year) National Oceanic and Atmospheric Administration Type II precipitation event. Scenario 0 represents the baseline or current conditions in the watershed and was used to compare the remaining 13 scenarios. Scenarios 1–8 and 12 rely on side-detention facilities to reduce peak flows and sediment transport. Scenario 9 has a diversion channel, and scenario 10 has a reservoir. Scenarios 11 and 13 incorporate channel armoring and channel widening, respectively. Scenarios 8 and 10, the scenario with the most side-detention facilities, and the scenario with the reservoir, respectively, were the most effective at reducing sediment transport and peak flow at the Pueblo, Colorado, streamgage. Scenarios 8 and 10 altered the peak flow by –58.9 and –56.4 percent, respectively. In turn, scenarios 8 and 10 altered the sediment transport by –17.7 and –62.1 percent, respectively.

Colorado↗
USGS2013

Annual modulation of non-volcanic tremor in northern Cascadia

Two catalogs of episodic tremor events in northern Cascadia, one from 2006 to 2012 and the other from 1997 to 2011, reveal two systematic patterns of tremor occurrence in southern Vancouver Island: (1) most individual events tend to occur in the third quarter of the year; (2) the number of events in prolonged episodes (i.e., episodic tremor and slip events), which generally propagate to Vancouver Island from elsewhere along the Cascadia subduction zone, is inversely correlated with the amount of precipitation that occurred in the preceding 2 months. We rationalize these patterns as the product of hydrologic loading of the crust of southern Vancouver Island and the surrounding continental region, superimposed with annual variations from oceanic tidal loading. Loading of the Vancouver Island crust in the winter (when the land surface receives ample precipitation) and unloading in the summer tends to inhibit and enhance downdip shear stress, respectively. Quantitatively, for an annually variable surface load, the predicted stress perturbation depends on mantle viscoelastic rheology. A mechanical model of downdip shear stress on the transition zone beneath Vancouver Island—driven predominantly by the annual hydrologic cycle—is consistent with the 1997–2012 tremor observations, with peak-to-peak downdip shear stress of about 0.4 kPa. This seasonal dependence of tremor occurrence appears to be restricted to southern Vancouver Island because of its unique situation as an elongated narrow-width land mass surrounded by ocean, which permits seasonal perturbations in shear stress at depth.

Journal of Geophysical Research B: Solid Earth↗
USGS2018

Hawai‘i and U.S.-Affiliated Pacific Islands

The U.S. Pacific Islands are culturally and environmentally diverse, treasured by the 1.9 million people who call them home. Pacific islands are particularly vulnerable to climate change impacts due to their exposure and isolation, small size, low elevation (in the case of atolls), and concentration of infrastructure and economy along the coasts. A prevalent cause of year-to-year changes in climate patterns around the globe and in the Pacific Islands region is the El Niño –Southern Oscillation (ENSO). The El Niño and La Niña phases of ENSO can dramatically affect precipitation, air and ocean temperature, sea surface height, storminess, wave size, and trade winds. It is unknown exactly how the timing and intensity of ENSO will continue to change in the coming decades, but recent climate model results suggest a doubling in frequency of both El Niño and La Niña extremes in this century as compared to the 20th century under scenarios with more warming, including the higher scenario (RCP8.5). On islands, all natural sources of freshwater come from rainfall received within their limited land areas. Severe droughts are common, making water shortage one of the most important climate-related risks in the region. As temperature continues to rise and cloud cover decreases in some areas, evaporation is expected to increase, causing both reduced water supply and higher water demand. Streamflow in Hawai‘i has declined over approximately the past 100 years, consistent with observed decreases in rainfall. The impacts of sea level rise in the Pacific include coastal erosion, episodic flooding, permanent inundation, heightened exposure to marine hazards, and saltwater intrusion to surface water and groundwater systems. Sea level rise will disproportionately affect the tropical Pacific and potentially exceed the global average. Invasive species , landscape change, habitat alteration, and reduced resilience have resulted in extinctions and diminished ecosystem function. Inundation of atolls in the coming decades is projected to impact existing on-island ecosystems. Wildlife that relies on coastal habitats will likely also be severely impacted. In Hawaiʻi, coral reefs contribute an estimated $477 million to the local economy every year. Under projected warming of approximately 0.5°F per decade, all nearshore coral reefs in the Hawai‘i and Pacific Islands region will experience annual bleaching before 2050. An ecosystem -based approach to international management of open ocean fisheries in the Pacific that incorporates climate-informed catch limits is expected to produce more realistic future harvest levels and enhance ecosystem resilience. Indigenous communities of the Pacific derive their sense of identity from the islands. Emerging issues for Indigenous communities of the Pacific include the resilience of marine-managed areas and climate-induced human migration from their traditional lands. The rich body of traditional knowledge is place-based and localized and is useful in adaptation planning because it builds on intergenerational sharing of observations. Documenting the kinds of governance structures or decision-making hierarchies created for management of these lands and waters is also important as a learning tool that can be shared with other island communities. Across the region, groups are coming together to minimize damage and disruption from coastal flooding and inundation as well as other climate-related impacts. Social cohesion is already strong in many communities, making it possible to work together to take action. Early intervention can lower economic, environmental, social, and cultural costs and reduce or prevent conflict and displacement from ancestral land and resources.

Report↗
USGS2000

Growth response of a deep-water ferromanganese crust to evolution of the Neogene Indian Ocean

A deep-water ferromanganese crust from a Central Indian Ocean seamount dated previously by 10Be and 230Th(excess) was studied for compositional and textural variations that occurred throughout its growth history. The 10Be/9Be dated interval (upper 32 mm) yields an uniform growth rate of 2.8 ?? 0.1 mm/Ma [Frank, M., O'Nions, R.K., 1998. Sources of Pb for Indian Ocean ferromanganese crusts: a record of Himalayan erosion. Earth Planet. Sci. Lett., 158, pp. 121-130.] which gives an extrapolated age of ~ 26 Ma for the base of the crust at 72 mm and is comparable to the maximum age derived from the Co-model based growth rate estimates. This study shows that Fe-Mn oxyhydroxide precipitation did not occur from the time of emplacement of the seamount during the Eocene (~ 53 Ma) until the late Oligocene (~ 26 Ma). This paucity probably was the result of a nearly overlapping palaeo-CCD and palaeo-depth of crust formation, increased early Eocene productivity, instability and reworking of the surface rocks on the flanks of the seamount, and lack of oxic deep-water in the nascent Indian Ocean. Crust accretion began (older zone) with the formation of isolated cusps of Fe-Mn oxide during a time of high detritus influx, probably due to the early-Miocene intense erosion associated with maximum exhumation of the Himalayas (op. cit.). This cuspate textured zone extends from 72 mm to 42 mm representing the early-Miocene period. Intense polar cooling and increased mixing of deep and intermediate waters at the close of the Oligocene might have led to the increased oxygenation of the bottom-water in the basin. A considerable expansion in the vertical distance between the seafloor depth and the CCD during the early Miocene in addition to the influx of oxygenated bottom-water likely initiated Fe-Mn crust formation. Pillar structure characterises the younger zone, which extends from 40 mm to the surface of the crust, i.e., ~ 15 Ma to Present. This zone is characterised by > 25% higher content of oxide-bound elements than in the older zone, possibly corresponding to further increased oxygenation of bottom-waters, increased stability of the seamount slope, and gradually reduced input of continental detritus from the erosion of the Himalayas. Middle Miocene Antarctic glaciation, which peaked ~ 12-13 Ma ago, increased the oxic bottom-water influx to the basin resulting in accretion of the crust with low detritus. Therefore, the younger crust started to accrete in response to a shift in bottom-water circulation towards the contemporary pattern, which produced a uniform growth rate and pillar structure up to the present. (C) 2000 Published by Elsevier Science B.V.

Marine Geology↗
USGS2011

The geochemistry and petrogenesis of the Paleoproterozoic Green Mountain arc: A composite(?), bimodal, oceanic, fringing arc

The inferred subduction affinity of the ∼1780-Ma Green Mountain arc, a dominantly bimodal igneous terrane (together with immature marine and volcaniclastic sedimentary rocks) accreted to the southern margin of the Wyoming province, is integral to arc-accretion models of the Paleoproterozoic growth of southern Laurentia. Conversely, the dominantly bimodal nature of many putative arc-related igneous suites throughout southern Laurentia, including the Green Mountain arc, has also been used to support models of growth by extension of pre-existing crust. We report new geochemical and isotopic data from ∼1780-Ma gabbroic and granodioritic to tonalitic rocks of the Big Creek Gneiss, interpreted as consanguineous with previously studied metavolcanic rocks of the Green Mountain Formation. The ∼1780-Ma Big Creek Gneiss mafic rocks show clear geochemical signatures of a subduction origin and provide no supporting evidence for extensional tectonism. The ∼1780-Ma Big Creek Gneiss felsic rocks are attributed to partial melting of mafic and/or mixed lower-crustal material. The bimodal nature of the suite results from the combination of arc basalts and felsic crustal melts. The lack of andesite is consistent with the observed tholeiitic differentiation trend of the mafic magmas. The lower ɛ Nd (1780 Ma) values for the felsic rocks vs. the mafic rocks suggest that the unexposed lower crust of the arc may be older than the arc and that Trans-Hudson- or Penokean-aged rocks possibly form the substratum of the arc. Our results reinforce previous interpretations that arc-related magmatism played a key role in the Paleoproterozoic crustal growth of southern Laurentia, but also support the possibility of unexposed older crust as basement to the arcs.

Wyoming, Colorado↗
USGS2008

Factors influencing densities of non-indigenous species in the ballast water of ships arriving at ports in Puget Sound, Washington, United States

Oceanographic characteristics and the presence of international shipping in Puget Sound, Washington, USA contribute to its vulnerability to non-indigenous species (NIS) invasions. To evaluate NIS arriving in ballast water, zooplankton was sampled in 380 ballast tanks of ships after they entered Puget Sound. Taxa were classified into a higher risk group of coastal organisms (including known NIS), and a lower risk group of largely oceanic species. Most ships reported conducting mid-ocean ballast water exchange (BWE). However, despite state regulations requiring BWE, and apparent compliance by ship operators, most sampled tanks from both transpacific and coastal routes had coastal zooplankton densities exceeding internationally proposed discharge standards. BWE efficiency models and controlled before-and-after BWE experiments indicate that BWE consistently removes most coastal zooplankton. However, this study found that although the empty-refill method of BWE significantly reduced coastal plankton compared with un-exchanged tanks, the flow-through method did not, and in either case remaining coastal plankton densities presented appreciable risks of introducing NIS. Densities of high risk taxa were consistently and significantly higher from US domestic trips dominated by tank ships carrying ballast water from California, and lower in samples from trans-Pacific trips dominated by container ships and bulk carriers with ballast from Asia. These findings are probably a result of the dense and diverse NIS assemblages present in California and other US west coast estuaries and the comparatively short transit times between them and Puget Sound. While it appears that BWE can effectively replace NIS with less risky ocean species, new reporting, verification, and operational procedures may be necessary to enhance BWE efficacy. In the long-term, the introduction of ballast water treatment technologies may be required to significantly reduce the discharge of risky organisms from commercial ships if BWE practices do not become more effective. Copyright ?? 2008 John Wiley & Sons, Ltd.

Aquatic Conservation: Marine and Freshwater Ecosys↗
USGS2018

Hydrogeology of, simulation of groundwater flow in, and potential effects of sea-level rise on the Kirkwood-Cohansey aquifer system in the vicinity of Edwin B. Forsythe National Wildlife Refuge, New Jersey

The Edwin B. Forsythe National Wildlife Refuge encompasses more than 47,000 acres of New Jersey coastal habitats, including salt marshes, freshwater wetlands, tidal wetlands, barrier beaches, woodlands, and swamps. The refuge is along the Atlantic Flyway and provides breeding habitat for fish, migratory birds, and other wildlife species. The refuge area may be threatened by global climate change, including sea-level rise (SLR). The Kirkwood-Cohansey aquifer system underlies the Edwin B. Forsythe National Wildlife Refuge. Groundwater is an important source of freshwater flow into the refuge, but information about the interaction of surface water and groundwater in the refuge area and the potential effects of SLR on the underlying aquifer system is limited. The U.S. Geological Survey (USGS), in cooperation with the U.S. Fish and Wildlife Service (USFWS), conducted a hydrologic assessment of the refuge in New Jersey and developed a groundwater flow model to improve understanding of the geohydrology of the refuge area and to serve as a tool to evaluate changes in groundwater-level altitudes that may result from a rise in sea level. Groundwater flow simulations completed for this study include a calibrated baseline simulation that represents 2005–15 hydraulic conditions and three SLR scenarios―20, 40, and 60 centimeters (cm) (0.656, 1.312, and 1.968 feet, respectively). Results of the three SLR simulations indicate that the water table in the unconfined Kirkwood-Cohansey aquifer system in the refuge area will rise, resulting in increased discharge of fresh groundwater to freshwater wetlands and streams. As sea level rises, simulated groundwater discharge to the salt marsh, bay, and ocean is projected to decrease. Flow from the salt marsh, bay, and ocean to the overlying surface water is projected to increase as sea level rises. The simulated movement of the freshwater-seawater interface as sea level rises depends on the hydraulic-head gradient. In the center of the Forsythe model area, topographic relief is 23 feet (ft) and the hydraulic-head gradient is 0.0033. In the center of the Forsythe model area, the simulated interface moved inland about 600 ft and downward about 15 ft from the baseline simulation to scenario 3 as a result of a SLR of 60 cm. In the southern part of the Forsythe model area, the topography is flatter (relief of 8 ft) and the hydraulic-head gradient is smaller (0.001). In the southern part of the Forsythe model study area, the simulated interface in this area is projected to move inland about 200 ft from the baseline simulation to scenario 3 and does not move downward.

New Jersey↗