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At least 343 records · Page 19Linked to original sources

USGS2002

The dynamics of subtidal poleward flows over a narrow continental shelf, Palos Verdes, CA

The Palos Verdes peninsula is a short, very narrow (< 3 km) shelf in southern California that is bracketed by two large embayments. In May 1992, arrays of up to 4 moorings and 2 benthic tripods were deployed in a yearlong study of the circulation processes over this shelf and the adjacent slope. Wind stress, coastal sea level, atmospheric pressure and wave records were obtained from offshore sites and from coastal stations surrounding Palos Verdes. Bottom stress calculated for the mid-shelf sites using a boundary-layer model and data from the above instruments indicated the bottom drag coefficient over this shelf is about 0.003 Currents flow toward the northwest along the shelf and upper slope. Speeds are generally around 20-30 cm/s. There was no obvious seasonal structure in the flow. The first EOF for subtidal alongshelf current accounted for nearly 70% of the variance at sites on the shelf and upper slope. The dominant fluctuations had periods between 5 and 20 days, periods longer than seen in the regional wind stress field. Coastal sea level and the alongshore gradient in sea level had a similar concentration of energy in the 5-20 day frequency band. About 30% of the alongshelf flow was coherent with the alongshelf pressure gradient; currents flowed down the pressure gradient with minimal phase lag. Winds accounted for only 15-20% of the variance in subtidal currents, but the measured effect of wind stress was large. A 1 dyne/cm2 wind stress was associated with a 20-30 cm/s alongshore current. Both the regional wind stress and the alongshelf pressure gradients had spatial scales much larger than found on this small shelf. Subtidal flows forced by these regional fields were set up in the adjacent, much broader basins. The currents amplified as they moved onto the narrow shelf between the basins. Hence, local wind-driven currents had anomalously large amplitudes. The momentum equations for alongshelf wind or pressure gradients did not balance because some of the measured terms were associated with regional fields, others with local process. Our observations suggest that it is more difficult to determine which measured fields reflect the local processes in regions with rapidly changing topography. ?? 2002 Elsevier Science Ltd. All rights reserved.

Continental Shelf Research↗

USGS2011

Sedimentary response to orogenic exhumation in the northern Rocky Mountain Basin and Range province, Flint Creek basin, west-central Montana

Middle Eocene through Upper Miocene sedimentary and volcanic rocks of the Flint Creek basin in western Montana accumulated during a period of significant paleoclimatic change and extension across the northern Rocky Mountain Basin and Range province. Gravity modelling, borehole data, and geologic mapping from the Flint Creek basin indicate that subsidence was focused along an extensionally reactivated Sevier thrust fault, which accommodated up to 800 m of basin fill while relaying stress between the dextral transtensional Lewis and Clark lineament to the north and the Anaconda core complex to the south. Northwesterly paleocurrent indicators, foliated metamorphic lithics, 64 Ma (40Ar/39Ar) muscovite grains, and 76 Ma (U-Pb) zircons in a ca. 27 Ma arkosic sandstone are consistent with Oligocene exhumation and erosion of the Anaconda core complex. The core complex and volcanic and magmatic rocks in its hangingwall created an important drainage divide during the Paleogene shedding detritus to the NNW and ESE. Following a major period of Early Miocene tectonism and erosion, regional drainage networks were reorganized such that paleoflow in the Flint Creek basin flowed east into an internally drained saline lake system. Renewed tectonism during Middle to Late Miocene time reestablished a west-directed drainage that is recorded by fluvial strata within a Late Miocene paleovalley. These tectonic reorganizations and associated drainage divide explain observed discrepancies in provenance studies across the province. Regional correlation of unconformities and lithofacies mapping in the Flint Creek basin suggest that localized tectonism and relative base level fluctuations controlled lithostratigraphic architecture.

Canadian Journal of Earth Sciences↗

USGS2013

Seventy-five years of science—The U.S. Geological Survey’s Western Fisheries Research Center

As of January 2010, 75 years have elapsed since Dr. Frederic Fish initiated the pioneering research program that would evolve into today’s Western Fisheries Research Center (WFRC). Fish began his research working alone in the basement of the recently opened Fisheries Biological Laboratory on Lake Union in Seattle, Washington. WFRC’s research began under the aegis of the U.S. Fish and Wildlife Service and ends its first 75 years as part of the U.S. Geological Survey with a staff of more than 150 biologists and support personnel and a heritage of fundamental research that has made important contributions to our understanding of the biology and ecology of the economically important fish and fish populations of the Nation. Although the current staff may rarely stop to think about it, WFRC’s antecedents extend many years into the past and are intimately involved with the history of fisheries conservation in the Western United States. Thus, WFRC Director Lyman Thorsteinson asked me to write the story of this laboratory “while there are still a few of you around who were here for some of the earlier years” to document the rich history and culture of WFRC by recognizing its many famous scientists and their achievements. This historyalso would help document WFRC’s research ‘footprint’ in the Western United States and its strategic directions. Center Director Thorsteinson concluded that WFRC’s heritage told by an emeritus scientist also would add a texture of legitimacy based on personal knowledge that will all-to-soon be lost to the WFRC and to the USGS. The WFRC story is important for the future as well as for historical reasons. It describes how we got to the place we are today by documenting the origin, original mission, and our evolving role in response to the constantly changing technical information requirements of new environmental legislation and organizational decision-making. The WFRC research program owes its existence to the policy requirements of Federal conservation legislation originating with the construction of Grand Coulee Dam in 1933. The research program was shaped by laws enacted in subsequent years such as the Federal Water Pollution Control Act (1972), National Environmental Policy Act (1973), Endangered Species Act (1974), and Northwest Power Planning Act (1980), to name only a few. The WFRC has not been constrained by direct management or regulatory responsibility for a particular fishery (such as providing sustainable catch limits data to a resource management structure). Thus, WFRC has been able to concentrate on scientific pursuits and information needs required by contemporary environmental legislation. Over the years, we have pioneered in several important areas of fisheries research including the diagnoses and control of diseases in economically important fish, effects of environmental alterations on the physiological quality and survival of Pacific salmon released from federal mitigation hatcheries, applications in biotelemetry, and the bioenergetics of predator-prey interactions in the Columbia River. The WFRC of today is a widely distributed organization in the Western United States. Knowledge of the historical connections and accomplishments of our predecessors is important beyond the sense of pride and unity it instills in the WFRC family of today. For example, a discerning reader will note the evolution of WFRC’s research from a single disciplinary focus (early era—hatchery disease problems), to multiple disciplines (middle to late era—species, populations, habitats; threatened and endangered species), to the present era (multidisciplinary and with increasing process focus). For the benefit of the current WFRC staff, more emphasis has been placed on the early years rather than on the present day because people are quite naturally more familiar with the recent past than with the research done during the first decades of WFRC’s existence. By every rational measure, the WFRC has evolved into a fisheries research organization well positioned to provide the biological information needed to support the continued conservation and management of our Nation’s living aquatic natural resources. The high standard of excellence that connects WFRC’s past to our present research program provides a firm foundation on which to base the work yet to be done. In another 75 years, WFRC will undoubtedly be a very different place than it is today, but its evolution will be forever rooted in the story of the research and of the people related here. More about the diverse fisheries research projects WFRC scientists are conducting today is available at WFRC’s website: http://wfrc.usgs.gov/.

Washington↗

USGS2000

Formation of ferromanganese crusts on northwest intertropical Pacific seamounts: Electron photomicrography and microprobe chemistry

Seven ferromanganese crusts from the northwest intertropical Pacific seamounts were analyzed for photomicroscopic growth structures, microprobe chemistry, and ages based on Co-chronometer growth rate. The crusts on the Marshall Islands seamounts are thick and ale divided into phosphatized lower older and nonphosphatized upper younger growth generations: the older crust consists of compact laminations and columns impregnated with carbonate fluoapatite (CFA), whereas the younger crust is characterized by porous botryoids and columns of ??-MnO2 and Fe oxyhydroxide. The crusts on the Federated States of Micronesia (FSM) and Palau Islands seamounts are thin and are often incorporated with inorganic opal-A in the uppermost part, comprising the younger generation. Some crusts show scours and fractures. Although the growth of crusts has been often interrupted by mass failure of slope sediments, the crusts on the Marshall Islands seamounts are estimated to have grown at rate of about 3 mm/Ma since the middle Eocene and to have been phosphatized in the late Oligocene during the host seamounts were located beneath the equatorial zone of high productivity. Prolonged infiltration of the oxygen minimum zone (OMZ) water into shallower water older crusts redistributed crust composition by precipitating CFA, enriching subsequent amounts of Mn and Ni, and removing some Co. The younger crust has formed at slower rate (about 2 mm/Ma) under the stronger influence of bottom-water circulation in the north of the equatorial zone, concentrating abundant Co. In the uppermost part of some crusts, siliceous skeletons transform with burial to inorganic opal-A and Si-rich Fe oxyhydroxide, suggesting that biosilica diagenesis can enhance crust growth. (C) 2000 Elsevier Science B.V.

Marine Geology↗

USGS2001

Paleoclimate and Amerindians: Evidence from stable isotopes and atmospheric circulation

Two Amerindian demographic shifts are attributed to climate change in the northwest plains of North America: at ???11,000 calendar years before present (yr BP), Amerindian culture apparently split into foothills-mountains vs. plains biomes; and from 8,000-5,000 yr BP, scarce archaeological sites on the open plains suggest emigration during xeric "Altithermal" conditions. We reconstructed paleoclimates from stable isotopes in prehistoric bison bone and relations between weather and fractions of C4 plants in forage. Further, we developed a climate-change model that synthesized stable isotope, existing qualitative evidence (e.g., palynological, erosional), and global climate mechanisms affecting this midlatitude region. Our isotope data indicate significant warming from ???12,400 to 11,900 yr BP, supporting climate-driven cultural separation. However, isotope evidence of apparently wet, warm conditions at 7,300 yr BP refutes emigration to avoid xeric conditions. Scarcity of archaeological sites is best explained by rapid climate fluctuations after catastrophic draining of the Laurentide Lakes, which disrupted North Atlantic Deep Water production and subsequently altered monsoonal inputs to the open plains.

Proceedings of the National Academy of Sciences of↗

USGS1990

Precambrian terrane of north-central Wisconsin: an aeromagnetic perspective

A shaded relief magnetic map covering most of the region of exposed Precambrian rocks of north-central Wisconsin shows the structural grain and many lithologic units with clarity and comprehensive detail. The area includes part of the volcanic sequence of the Keweenawan Supergroup south of Lake Superior, the southern margin of the Archean Superior Province, the accreted island-arc terranes of the Penokean Orogen, and the Wolf River batholith. Numerous dikes are evident in the shaded relief, some being more than 200 km in length. Many of the longer dikes are reversely magnetized Keweenawan diabase associated with early extension of the Midcontinent Rift; some apparently were intruded along preexisting faults. A northwest system of dikes and faults indicated by the shaded relief map may be related to later stages of Keweenawan rifting. The Wolf River batholith is characterized by low magnetic relief associated with the predominant granitoids but includes circular plutons of highly magnetic anorthosite and a large area of magnetic rock having a signature different from the mapped anorthosite bodies. A fault bounding the western side of the batholith is paralleled by an apparent system of faults or dikes in the older terrane to the west. The magnetic map covering the Wisconsin magmatic terranes and the Archean Superior Province margin to the north is dominated by east-northeast-trending Penokean rocks. Large units of magnetic mafic rocks and less magnetic granitoid rocks are cut by a system of well-defined northeast shear zones and a more easterly trending, possibly younger set of faults, some of which contain dikes along parts of their lengths. Although the sutures bounding the magmatic terranes generally follow the magnetic trends, they do not have distinctive magnetic signatures.

Wisconsin↗

USGS2020

Rainfall triggers more deep-seated landslides than Cascadia earthquakes in the Oregon Coast Range, USA

The coastal Pacific Northwest USA hosts thousands of deep-seated landslides. Historic landslides have primarily been triggered by rainfall, but the region is also prone to large earthquakes on the 1100-km-long Cascadia Subduction Zone megathrust. Little is known about the number of landslides triggered by these earthquakes because the last magnitude 9 rupture occurred in 1700 CE. Here, we map 9938 deep-seated bedrock landslides in the Oregon Coast Range and use surface roughness dating to estimate that past earthquakes triggered fewer than half of the landslides in the past 1000 years. We find landslide frequency increases with mean annual precipitation but not with modeled peak ground acceleration or proximity to the megathrust. Our results agree with findings about other recent subduction zone earthquakes where relatively few deep-seated landslides were mapped and suggest that despite proximity to the megathrust, most deep-seated landslides in the Oregon Coast Range were triggered by rainfall.

Oregon↗

USGS2026

Region-specific understanding of virus transmission to support salmonid health at hatcheries in three regions of the Pacific Northwest, North America

Juvenile salmonid mortality due to infectious haematopoietic necrosis virus (IHNV) can be a major burden on fish hatcheries. We consider possible IHNV transmission routes and specialist–generalist patterns across three regions in the Pacific Northwest of North America: Coastal Washington and Oregon (CWO), Lower Columbia River Basin (LCRB) and Snake River Basin (SRB) to obtain multi-region inference about IHNV transmission and specialization. While individual regions have been studied previously, our consideration of three regions to identify consistent trends or localized patterns is novel. The most consistent patterns we found were that most exposure to IHNV was from migrating adult salmonids and that the IHNV lineage MD specialized in steelhead and rainbow trout. Our results were consistent with LCRB being a source of IHNV and the SRB and CWO being sinks. Results specific to particular regions include the role of local geography on exposure and influence of hatchery complexes on transmission, which highlights the need to understand local hatchery operations before disease ecology can be understood and suitable hatchery management can be planned. Results demonstrate the need for spatially and temporally explicit quantitative approaches to understand disease dynamics and inform management.

Oregon, Washington↗

USGS2024

Wildfires influence mercury transport, methylation, and bioaccumulation in headwater streams of the Pacific Northwest

The increasing frequency and severity of wildfires are among the most visible impacts of climate change. However, the effects of wildfires on mercury (Hg) transformations and bioaccumulation in stream ecosystems are poorly understood. We sampled soils, water, sediment, in-stream leaf litter, periphyton, and aquatic invertebrates in 36 burned (one-year post fire) and 21 reference headwater streams across the northwestern U.S. to evaluate the effects of wildfire occurrence and severity on total Hg (THg) and methylmercury (MeHg) transport and bioaccumulation. Suspended particulate THg and MeHg concentrations were 89 and 178% greater in burned watersheds compared to unburned watersheds and increased with burn severity, likely associated with increased soil erosion. Concentrations of filter-passing THg were similar in burned and unburned watersheds, but filter-passing MeHg was 51% greater in burned watersheds, and suspended particles in burned watersheds were enriched in MeHg but not THg, suggesting higher MeHg production in burned watersheds. Among invertebrates, MeHg in grazers, filter-feeders, and collectors was 33, 48, and 251% greater in burned watersheds, respectively, but did not differ in shredders or predators. Thus, increasing wildfire frequency and severity may yield increased MeHg production, mobilization, and bioaccumulation in headwaters and increased transport of particulate THg and MeHg to downstream environments.

Idaho, Oregon, Washington↗

USGS1992

Suspension freezing of bottom sediment and biota in the Northwest Passage and implications for Arctic Ocean sedimentation

Ice observations and sediment collected in a summer transit through the Northwest Passage provide insights on suspension freezing, the most important sediment entrainment mechanism for the Arctic Ocean. No evidence was seen for entrainment by bottom adfreezing, bluff slumping, river flooding, dragging ice keels, or significant eolian transport from land to sea. Lack of eolian sediment loading in the Northwest Passage, together with that already reported for northern Alaska, eliminates wind as an important source for fine sediment in the pack of the Beaufort Gyre and related parts of the Transpolar Drift. Muddy sediment with pebbles and cobbles, algae with holdfasts, ostracodes with appendages, and well-preserved mollusks and sea urchins were collected from two sites in a 50 km long stretch of turbid ice. These materials indicate that suspension freezing reaching to a water depth of 25–30 m during the previous fall was responsible for entrainment. This mechanism requires rapid ice formation in open, shallow water during a freezing storm, when the ocean becomes supercooled, and frazil and anchor ice attach to and ultimately lift sediment and living organisms to the sea surface. The mechanism, already known to be important in the Beaufort Sea, probably also affects wide, shallow Siberian shelves and leads to cross-shelf transport of shallow-water organisms and dropstones with "glacial striations" toward deep basins. This makes distinguishing glacial–interglacial cycles more difficult.

Nunavut↗

USGS2001

The geology of a part of Acadia and the nature of the Acadian orogeny across Central and Eastern Maine

The zone of Acadian collision between the Medial New England and Composite Avalon terranes is well preserved in Maine. A transect from northwest (Rome) to southeast (Camden) crosses the eastern part of Medial New England comprising the Central Maine basin, Liberty-Orrington thrust sheet, and Fredericton trough, and the western part of Composite Avalon, including the Graham Lake, Clarry Hill, and Clam Cove thrust sheets. U-Pb geochronology of events before, during, and after the Acadian orogeny helps elucidate the nature and distribution of tectonostratigraphic belts in this zone and the timing of some Acadian events in the Northern Appalachians. The Central Maine basin consists of sedimentary and volcanic rocks of Middle Ordovician (∼470 to ∼460 Ma) age overlain with probable conformity by latest Ordovician(?) through earliest Devonian marine rift and flysch sedimentary rocks; these are intruded by weakly to undeformed plutonic rocks of Early and Middle Devonian age (∼399–378 Ma). The Fredericton trough consists of Early Silurian gray pelite and sandstone to earliest Late Silurian calcareous turbidite, deformed and variably metamorphosed prior to the emplacement of Late Silurian (∼422 Ma) and Early to Late Devonian (∼418 to ∼368 Ma) plutons. The Liberty-Orrington thrust sheet consists of Cambrian(?)-Ordovician (>∼474 to ∼469 Ma and younger) clastic sedimentary and volcanic rocks intruded by highly deformed Late Silurian (∼424 to ∼422 Ma) and Devonian (∼418 to ∼389 Ma) plutons, possibly metamorphosed in Late Silurian time (prior to ∼417 Ma), and metamorphosed to amphibolite facies in Early to Middle Devonian time (∼400 to ∼381 Ma). The Graham Lake thrust sheet contains possible Precambrian rocks, Cambrian sedimentary rocks with a volcanic unit dated at ∼503 Ma, and Ordovician rocks with possible Caradocian Old World fossils, metamorphosed and deformed in Silurian time and intruded by mildly to undeformed Late Silurian (∼421 Ma) and Late Devonian (∼371 to ∼368 Ma) plutons. The Clarry Hill thrust sheet consists of poorly studied, highly metamorphosed Cambrian (?) rocks. The Clam Cove thrust sheet contains highly deformed Precambrian limestone, shale, sandstone, and conglomerate, metamorphosed to epidote amphibolite facies and intruded by a mildly deformed pluton dated at ∼421 Ma. Metamorphism, deformation, and voluminous intrusive igneous activity of Silurian age are common to both the most southeastern parts of Medial New England and the thrust sheets of Composite Avalon. In contrast to Medial New England, the thrust sheets of Composite Avalon show only modest effects of Devonian deformation and metamorphism. Regional stratigraphic relations, paleontologic findings, and U-Pb geochronology suggest that the Graham Lake, Clarry Hill, and Clam Cove thrust sheets are far-traveled allochthons that were widely separated from Medial New England in the Silurian. One hundred nine (109) new U-Pb analyses of zircon, monazite, and sphene from 25 samples of metamorphosed, stratified, and intrusive igneous rocks are used to decipher the history of events along the transect. In our view, many of the structures within Medial New England were formed during the closing of the back-arc ocean during the waning stages of the Taconian orogeny. These features include the precursors to the upright folds found in Silurian sedimentary rocks, the west-facing Liberty-Orrington thrust sheet, and the Silurian plutons of Medial New England. Acadian tectonic features, including flysch sedimentation, igneous activity, deformation with nappe emplacement, and metamorphism record the progressive loading of Medial New England by a stack of thrust nappes emplaced in latest Silurian to Middle Devonian time. The Acadian orogeny is a prolonged event, lasting from earliest Late Silurian to the Late Devonian, whose evolution involved: (1) convergence between Medial New England and Composite Avalon along an east-dipping subduction zone from earliest Late Silurian to Early Devonian time; (2) collision and concurrent delamination of lithospheric mantle beneath Medial New England in Early Devonian time resulting in deformation, high-grade metamorphism, and intrusive igneous activity in the most eastern part of Medial New England and the western parts of Composite Avalon; (3) Early to Middle Devonian northwest-migrating penetrative deformations of the Acadian Main stage, including northwest-directed thrusting and recumbent folding followed by tightening of folds possibly produced in the waning stages of the Taconian orogeny and forming folded wave trains of isoclinal folds (∼419 to ∼404 Ma), (4) asymmetrical folds produced by east-west shortening (∼399 to ∼380 Ma); and (5) final westward emplacement of Composite Avalon thrust sheets onto Medial New England in Late Devonian time (∼380 to ∼371 Ma). The present boundary between rocks of Medial New England and Composite Avalon at the surface is the Sennebec Pond fault, a high-angle fault that cuts the Graham Lake and Clarry Hill thrusts, and is intruded by the Mt. Waldo pluton (∼371), one of several Late Devonian plutons (∼371 to ∼367 Ma) that mark the end of the Acadian orogeny in coastal Maine. The thrust sheets of Composite Avalon carried rocks of peri-Gondwanan affinity and with possible Old World fauna many kilometers to the west over Medial New England, thus potentially hiding the original suture at depth under the Gulf of Maine.

Maine↗

USGS2006

Sedimentary deposits of the 26 December 2004 tsunami on the northwest coast of Aceh, Indonesia

The 2004 Sumatra-Andaman tsunami flooded coastal northern Sumatra to a depth of over 20 m, deposited a discontinuous sheet of sand up to 80 cm thick, and left mud up to 5 km inland. In most places the sand sheet is normally graded, and in some it contains complex internal stratigraphy. Structures within the sand sheet may record the passage of up to 3 individual waves. We studied the 2004 tsunami deposits in detail along a flow-parallel transect about 400 m long, 16 km southwest of Banda Aceh. Near the shore along this transect, the deposit is thin or absent. Between 50 and 400 m inland it ranges in thickness from 5 to 20 cm. The main trend in thickness is a tendency to thicken by filling low spots, most dramatically at pre-existing stream channels. Deposition generally attended inundation - along the transect, the tsunami deposited sand to within about 40 m of the inundation limit. Although the tsunami deposit contains primarily material indistinguishable from material found on the beach one month after the event, it also contains grain sizes and compositions unavailable on the current beach. Along the transect we studied, these grains become increasingly dominant both landward and upward in the deposit; possibly some landward source of sediment was exposed and exploited by the passage of the waves. The deposit also contains the unabraded shells of subtidal marine organisms, suggesting that at least part of the deposit came from offshore. Grain sizes within the deposit tend to fine upward and landward, although individual units within the deposit appear massive, or show reverse grading. Sorting becomes better landward, although the most landward sites generally become poorly sorted from the inclusion of soil clasts. These sites commonly show interlayering of sandy units and soil clast units. Deposits from the 2004 tsunami in Sumatra demonstrate the complex nature of the deposits of large tsunamis. Unlike the deposits of smaller tsunamis, internal stratigraphy is complex, and will require some effort to understand. The Sumatra deposits also show the contribution of multiple sediment sources, each of which has its own composition and grain size. Such complexity may allow more accurate modeling of flow depth and flow velocity for paleotsunamis, if an understanding of how tsunami hydraulics affect sedimentation can be established. Copyright ?? The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB.

Earth, Planets and Space↗

USGS2017

Longitudinal thermal heterogeneity in rivers and refugia for coldwater species: Effects of scale and climate change

Climate-change driven increases in water temperature pose challenges for aquatic organisms. Predictions of impacts typically do not account for fine-grained spatiotemporal thermal patterns in rivers. Patches of cooler water could serve as refuges for anadromous species like salmon that migrate during summer. We used high-resolution remotely sensed water temperature data to characterize summer thermal heterogeneity patterns for 11,308 km of second–seventh-order rivers throughout the Pacific Northwest and northern California (USA). We evaluated (1) water temperature patterns at different spatial resolutions, (2) the frequency, size, and spacing of cool thermal patches suitable for Pacific salmon (i.e., contiguous stretches ≥ 0.25 km, ≤ 15 °C and ≥ 2 °C, aooler than adjacent water), and (3) potential influences of climate change on availability of cool patches. Thermal heterogeneity was nonlinearly related to the spatial resolution of water temperature data, and heterogeneity at fine resolution (< 1 km) would have been difficult to quantify without spatially continuous data. Cool patches were generally > 2.7 and < 13.0 km long, and spacing among patches was generally > 5.7 and < 49.4 km. Thermal heterogeneity varied among rivers, some of which had long uninterrupted stretches of warm water ≥ 20 °C, and others had many smaller cool patches. Our models predicted little change in future thermal heterogeneity among rivers, but within-river patterns sometimes changed markedly compared to contemporary patterns. These results can inform long-term monitoring programs as well as near-term climate-adaptation strategies.

California, Idaho, Oregon, Washington↗

USGS2023

Paleohydrologic history of pluvial lake San Agustin, New Mexico: Tracking changing effective moisture in southwest North America through the last glacial transition

Paleoclimate records across the Intermountain West region of North America show significant regional variation in timing and magnitude of wet conditions that accompanied the last glacial-interglacial transition. To understand the climate controls on paleohydrologic change, well-dated records are needed across the region. The Plains of San Agustin (New Mexico, USA) is a closed-basin watershed of the American Southwest influenced by both winter westerly and summer North American Monsoon precipitation. The flat valley floors of the Plains contain lake and groundwater discharge deposits that record multiple periods of past wet climate. We present a record of hydroclimate for the past 26,000 years based on radiocarbon, U–Th series, and OSL dating of these deposits and stratigraphic correlation across the three sub-basins of the lake system. We find that two major lake oscillations occurred, coincident with the global Last Glacial Maximum (∼23–18 ka) and with Heinrich Stadial 1 (∼17–14 ka). The LGM lake cycle created a deep lake in the lowermost sub-basin, fed by marsh/lake overflow in the upper sub-basins. The Heinrich Stadial 1 wet interval attained the highest recorded lake level between ∼17.0 and 15.3 ka, merging the lower two sub-basins into one lake. Both lake cycles agree well in timing and magnitude with other lake-based records from the southwestern U.S., supporting previous interpretations that a south-shifted cool season storm track brought a dipole-like pattern of enhanced moisture to the southwest at the expense of drier conditions in the northwest during the LGM and deglaciation. A transition from lake to groundwater discharge conditions followed during the Bølling-Allerød (14.7–12.9 ka) across the study area. Wet meadows prevailed in the lower sub-basin during the Younger Dryas (12.9–11.7 ka), with marsh and open lake conditions in the upper and middle sub-basins, respectively. During the early Holocene, discrete wet intervals are recorded by ages for wet meadow deposits in all sub-basins with centennial-millennial frequency at 9.9, 8.8, 8.2 ka. These events agree well with other Intermountain West records showing wetter-than-present conditions prior to 8 ka. Two additional wet periods, centered at 6.8 and 5.4 ka, occurred during the driest known interval of the middle Holocene, and likely were partly supported in the Plains of San Agustin by summer moisture associated with the peak strength of the North American Monsoon. Our record highlights that both winter and summer moisture support water resources in New Mexico watersheds.

New Mexico↗

USGS2012

Predicting sea-level rise vulnerability of terrestrial habitat and wildlife of the Northwestern Hawaiian Islands

If current climate change trends continue, rising sea levels may inundate low-lying islands across the globe, placing island biodiversity at risk. Recent models predict a rise of approximately one meter (1 m) in global sea level by 2100, with larger increases possible in areas of the Pacific Ocean. Pacific Islands are unique ecosystems home to many endangered endemic plant and animal species. The Northwestern Hawaiian Islands (NWHI), which extend 1,930 kilometers (km) beyond the main Hawaiian Islands, are a World Heritage Site and part of the Papahanaumokuakea Marine National Monument. These NWHI support the largest tropical seabird rookery in the world, providing breeding habitat for 21 species of seabirds, 4 endemic land bird species and essential foraging, breeding, or haul-out habitat for other resident and migratory wildlife. In recent years, concern has grown about the increasing vulnerability of the NWHI and their wildlife populations to changing climatic patterns, particularly the uncertainty associated with potential impacts from global sea-level rise (SLR) and storms. In response to the need by managers to adapt future resource protection strategies to climate change variability and dynamic island ecosystems, we have synthesized and down scaled analyses for this important region. This report describes a 2-year study of a remote northwestern Pacific atoll ecosystem and identifies wildlife and habitat vulnerable to rising sea levels and changing climate conditions. A lack of high-resolution topographic data for low-lying islands of the NWHI had previously precluded an extensive quantitative model of the potential impacts of SLR on wildlife habitat. The first chapter (chapter 1) describes the vegetation and topography of 20 islands of Papahanaumokuakea Marine National Monument, the distribution and status of wildlife populations, and the predicted impacts for a range of SLR scenarios. Furthermore, this chapter explores the potential effects of SLR on wildlife breeding habitats for each island. The subsequent chapter (chapter 2) details a study of the Laysan Island ecosystem, describing a quantitative model that incorporates SLR, storm wave, and rising groundwater inundation. Wildlife, storm, and oceanographic data allowed for an assessment of the phenological and spatial vulnerability of Laysan Island's breeding bird species to SLR and storms. Using remote sensing and geospatial techniques, we estimated topography, classified vegetation, modeled SLR, and evaluated a range of climate change scenarios. On the basis of high-resolution airborne data collected during 2010-11 (root-mean-squared error = 0.05-0.18 m), we estimated the maximum elevation of 20 individual islands extending from Kure Atoll to French Frigate Shoals (range: 1.8-39.7 m) and computed the mean elevation (1.7 m, standard deviation 1.1 m) across all low-lying islands. We also analyzed general climate models to describe rainfall and temperature scenarios expected to influence adaptation of some plants and animals for this region. Outcomes for the NWHI predicted an increase in temperature of 1.8-2.6 degrees Celsius (°C) and an annual decrease in precipitation of 24.7-76.3 millimeters (mm) across the NWHI by 2100. Our models of passive SLR (excluding wave-driven effects, erosion, and accretion) showed that approximately 4 percent of the total land area in the NWHI will be lost with scenarios of +1.0 m of SLR and 26 percent will be lost with +2.0 m of SLR. Some atolls are especially vulnerable to SLR. For example, at Pearl and Hermes Atoll our analysis indicated substantial habitat losses with 43 percent of the land area inundated at +1.0 m SLR and 92 percent inundated at +2.0 m SLR. Across the NWHI, seven islands will be completely submerged with +2.0 m SLR. The limited global ranges of some tropical nesting birds make them particularly vulnerable to climate change impacts in the NWHI. Climate change scenarios and potential SLR impacts presented here emphasize the need for early climate change adaptation and mitigation planning, especially for species with limited breeding distributions and/or ranges restricted primarily to the low-lying NWHI: Cyperus pennatiformis var. bryanii , Black-footed Albatross ( Phoebastria nigripes ), Laysan Albatross ( P. immutabilis ), Bonin Petrel ( Pterodroma hypoleuca ), Gray-backed Tern ( Onychoprion lunatus ), Laysan Teal ( Anas laysanensis ), Laysan Finch ( Telespiza cantans ), and Hawaiian monk seal ( Monachus schauinslandi ). Furthermore, SLR scenarios that include the effects of wave dynamics and groundwater rise may indicate amplified vulnerability to climate change driven habitat loss on low-lying islands. In chapter 2, we incorporated the combined effects of SLR, dynamic wave-driven inundation, and rising groundwater in a quantitative study specifically for the Laysan Island ecosystem. This is the first hydrodynamic model to simulate the combined impacts of SLR and wave-driven inundation in the NWHI. We developed a high-resolution digital elevation model (mean vertical accuracy of 0.32 m) for the island. Then using recent satellite imagery, geospatial models, and historical oceanographic, storm, and biological data we estimated potential inundation extent, habitat loss, and wildlife population impacts for a range of potential SLR scenarios (0.00, +0.50, +1.00, +1.50, and +2.00 m) that may occur over the next century. Additionally, we estimated the carrying capacity of Laysan Island for five species based on the available population monitoring data and described how potential losses in nesting habitat could influence population dynamics for Black-footed Albatross, Laysan Albatross, Red-footed Booby (Sula sula), Laysan Teal, and Laysan Finch. For some other seabird populations (Masked Booby, S. dactylatra ; Brown Booby, S. leucogaster ; Great Frigatebird, Fregata minor ; and Sooty Tern, Onychoprion fuscata ), we used recent colony distribution data, land cover maps, and nesting behavior to estimate potential losses of nesting habitat from SLR and wave-driven inundation. We observed far greater potential impacts of SLR to wildlife with the dynamic wave-driven modeling approach than with the passive modeling approach. Depending on SLR scenario and coastal orientation, during storms under a +2.00 m SLR scenario, the wave-driven inundation model predicted three times more inundation than the passive model (17.2 percent of total terrestrial area versus 4.6 percent, respectively). Large-wave events generally added 1 m of water height to passive inundation surfaces, therefore our dynamic models (during storm events) forecasted comparable inundation extents earlier than passive models. Although wave-driven water levels were highest in the northwest quadrant of Laysan Island, the greatest extent of inundation occurred in the southeast where coastal dunes less than 3 m above mean sea level provide little protection from wave-driven inundation. When wave-driven inundation was included in the SLR model for Laysan Island greater nesting habitat loss and potential impacts on wildlife population dynamics were predicted. The consequences of habitat loss due to SLR may be worse for species with colonies in the wave-exposed coastal zones (for example, Black-footed Albatross) and for populations already near the island's carrying capacity (for example, Laysan Teal). Species whose peak incubation and chick-rearing periods coincide with seasonally high wave heights also will be increasingly vulnerable, especially those species nesting on the ground in areas vulnerable to inundation, such as Gray-backed Tern and Black-footed Albatross. Other species that have space for population growth, or are not restricted to a narrow range of habitat types on Laysan (for instance, Sooty Terns), may be less sensitive to habitat loss from SLR over the next century. Our assessments of inundation risk, habitat loss, and wildlife species vulnerability synthesize current knowledge about individual islands and contribute to a broader understanding of the impacts of inundation from SLR and storm-induced waves. Yet, most NWHI and their bird populations lack monitoring data to evaluate adaptations to and impacts of climate change. Exceptions include some data sets from long-term monitoring of wildlife populations, tides, or weather at French Frigate Shoals, Laysan Island, and Midway Atoll. These data sets are potentially valuable baselines, which could be informative for adaptive learning (integrating management and science) to predict, adapt, and mitigate the effects of climate change on NWHI wildlife in the future. This study provides the first quantitative vulnerability assessment for all of the low-lying NWHI, and results identify biological communities, locales, and resident endangered species of Papahanaumokuakea Marine National Monument expected to be at risk from SLR. This report is also intended as a reference for managers and conservation planners, a tool to identify and potentially reduce uncertainty, and a starting place for developing climate change monitoring priorities and future scientific studies.

Hawai'i↗

USGS2020

The importance of the Northeastern Gulf of Mexico to foraging loggerhead sea turtles

Identification of high-use foraging sites where imperiled sea turtles are resident remains a globally-recognized conservation priority. In the biodiverse Gulf of Mexico (GoM), recent telemetry studies highlighted post-nesting foraging sites for federally threatened loggerhead turtles (Caretta caretta). Our aim here was to discern loggerhead use of additional northern GoM regions that may serve as high-use foraging sites. Thus, we used satellite tracking and switching state-space modeling to show that the Big Bend region off the northwest Florida coast is a coastal foraging area that supports imperiled adult female loggerhead turtles tracked from different nesting subpopulations. From 2011 to 2016, we satellite-tagged 15 loggerheads that nested on four distinct beaches around the GoM: Dry Tortugas National Park, FL; Everglades National Park, FL; St. Joseph Peninsula, FL; and Gulf Shores, AL. Turtles arrived at their foraging ground in the Big Bend region between June and September and remained resident in their respective foraging sites for an average of 198 tracking days, where they established mean home ranges (95% kernel density estimate) 232.7 km2. Larger home ranges were in deeper water; 50% kernel density estimate centroid values were a mean 26.4 m deep and 52.7 km from shore. The Big Bend region provides a wide area of suitable year-round foraging habitat for loggerheads from at least 3 different nesting subpopulations. Understanding where and when threatened loggerheads forage and remain resident is key for designing both surveys of foraging resources and additional protection strategies that can impact population recovery trajectories for this imperiled species.

Florida↗

USGS2015

Community clusters of tsunami vulnerability in the US Pacific Northwest

Many coastal communities throughout the world are threatened by local (or near-field) tsunamis that could inundate low-lying areas in a matter of minutes after generation. Although the hazard and sustainability literature often frames vulnerability conceptually as a multidimensional issue involving exposure, sensitivity, and resilience to a hazard, assessments often focus on one element or do not recognize the hazard context. We introduce an analytical framework for describing variations in population vulnerability to tsunami hazards that integrates ( i ) geospatial approaches to identify the number and characteristics of people in hazard zones, ( ii ) anisotropic path distance models to estimate evacuation travel times to safety, and ( iii ) cluster analysis to classify communities with similar vulnerability. We demonstrate this approach by classifying 49 incorporated cities, 7 tribal reservations, and 17 counties from northern California to northern Washington that are directly threatened by tsunami waves associated with a Cascadia subduction zone earthquake. Results suggest three primary community groups: ( i ) relatively low numbers of exposed populations with varied demographic sensitivities, ( ii ) high numbers of exposed populations but sufficient time to evacuate before wave arrival, and ( iii ) moderate numbers of exposed populations but insufficient time to evacuate. Results can be used to enhance general hazard-awareness efforts with targeted interventions, such as education and outreach tailored to local demographics, evacuation training, and/or vertical evacuation refuges.

California, Oregon, Washington↗

USGS2018

Rapid discovery of SNPs differentiating hatchery steelhead trout from ESA-listed natural-origin steelhead trout using a 57K SNP array

Natural-origin steelhead trout ( Oncorhynchus mykiss (Walbaum, 1792)) in the Pacific Northwest, USA, are threatened by a number of factors including habitat destruction, disease, decline in marine survival, and a potential erosion of genetic viability due to introgression from hatchery strains. Our major goal was to use a recently developed SNP array containing ∼57 000 SNPs to identify a subset of SNPs that differentiate hatchery and natural-origin populations. We analyzed 35 765 polymorphic SNPs in nine populations of steelhead trout sampled from Puget Sound, Washington, USA. We then conducted two outlier tests and found 360 loci that were candidates for divergent selection between hatchery and natural-origin populations (mean F CT = 0.29, maximum = 0.65) and 595 SNPs that were candidates for selection among natural-origin populations (mean F ST = 0.25, maximum = 0.51). Comparisons with a linkage map revealed that two chromosomes (Omy05 and Omy25) contained significantly more outliers than other chromosomes, suggesting that regions on Omy05 and Omy25 may be of adaptive significance. Our results highlight several advantages of the 57 000 SNP array as a tool for population and conservation genomics studies.

British Columbia, Washington↗