To investigate the effects of logging, three small watersheds in the Alsea River basin on the west slope of the Oregon Coast Range were selected for study. This was an interdisciplinary investigation to evaluate the influence of specific logging methods on stream regimen and on aquatic resources. The study plan...
We present a new hypothesis to explain the millennial-scale temperature variability recorded in ice cores known as Dansgaard-Oeschger (DO) cycles. We propose that an ice shelf acted in concert with sea ice to set the slow and fast timescales of the DO cycle, respectively. The abrupt warming at the onset...
In this technical note, a steady-state analytical solution of concentrations of a parent solute reacting to a daughter solute, both of which are undergoing transport and multirate mass transfer, is presented. Although the governing equations are complicated, the resulting solution can be expressed in simple terms. A function of the...
Tides in the Delaware Bay (USA) have been modeled from 7000 years before present (7 ka) to the present day and for selected future sea-level rise scenarios (100 years, 300 years). Historic bathymetries were constructed through use of glacial isostatic adjustment models and a very high spatial resolution (< 100...
The residual of the surface energy budget is represented as the linearized sum of energy losses due to storage, advection and flux underestimation. Individual contributions to the residual can be quantified through constrained multiple linear regression which identifies the site specific processes that are responsible for the lack of energy...
The carbon system of the western Arctic Ocean is undergoing a rapid transition as sea ice extent and thickness decline. These processes are dynamically forcing the region, with unknown consequences for CO2 fluxes and carbonate mineral saturation states, particularly in the coastal regions where sensitive ecosystems are already under threat...
Temperature is a fundamentally important driver of ecosystem processes in streams. Recent warming of terrestrial climates around the globe has motivated concern about consequent increases in stream temperature. More specifically, observed trends of increasing air temperature and declining stream flow are widely believed to result in corresponding increases in stream...
Reconciling rates of organic carbon export from the euphotic zone with the consumption of organic material in the dark ocean remains one of the major quantitative uncertainties of the ocean carbon cycle. Euphotic zone net community production (NCP) provides one broad constraint on export flux and potential carbon drawdown. However,...
Biomass burning is a significant contributor to atmospheric carbon emissions but may also provide an avenue in which fire-affected ecosystems can accumulate carbon over time, through the generation of highly resistant fire-altered carbon. Identifying how fuel moisture, and subsequent changes in the fire behavior, relates to the production of fire-altered...
We examine the thermal effects of seamount subduction. Seamount subduction may cause transient changes in oceanic crust hydrogeology and plate boundary fault position. Prior to subduction, seamounts provide high‐permeability pathways between the basaltic crustal aquifer and overlying ocean that can focus fluid flow and efficiently cool the oceanic crust. As...
The loss of Arctic sea ice has emerged as a leading signal of global warming. This, together with acknowledged impacts on other components of the Earth system, has led to the term “the new Arctic.” Global coupled climate models predict that ice loss will continue through the twenty-first century, with...
Seamounts are a ubiquitous feature of the seafloor but relatively little is known about their internal structure. A seamount preserved in the Franciscan mélange of California suggests a sequence of formation common to all seamounts. Field mapping, geophysical measurements, and geochemical analyses are combined to interpret three stages of seamount...
At the Costa Rica margin along the Middle America Trench along‐strike variations in heat flow are well
mapped. These variations can be understood in terms of either ventilated fluid flow, where exposed basement
allows fluids to freely advect heat between the crustal aquifer and ocean, or insulated fluid flow where...
Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects,...
Numerical solutions to the nonlinear Boussinesq equation, applied to a steeply sloping aquifer and assuming uniform hydraulic conductivity, indicate that late-time recession discharge decreases nearly linearly in time. When recession discharge is characterized by -dQ/dt=aQ[superscript b], this is equivalent to constant dQ/dt or b=0. This result suggests that a previously...
During summer 2007, perennial sea ice in the Beaufort Sea, Arctic Ocean, experienced an unprecedented amount of basal melt. It has previously been shown that this basal melt was linked to an increase in open-water fraction, increasing absorption of solar radiation into the ocean. GPS ice drifters, deployed around the...
The output of gas and tephra from volcanoes is an inherently disorganized process that makes reliable flux estimates challenging to obtain. Continuous monitoring of gas flux has been achieved in only a few instances at subaerial volcanoes, but never for submarine volcanoes. Here we use the first sustained (yearlong) hydroacoustic...
During the last glacial period atmospheric carbon dioxide and temperature in Antarctica varied in a similar fashion on millennial time scales, but previous work indicates that these changes were gradual. In a detailed analysis of one event we now find that approximately half of the CO₂ increase that occurred during...
We estimate the depth of the 120°C isotherm by constructing crustal thermal gradients based on theoretical and observed conductive heat flux as a function of lithospheric age. We chose the 120°C isotherm because it is close to the upper limit for prokaryotic life, and therefore, the isotherm approximates the maximum...
It is widely accepted that plate divergence at mid-ocean ridges drives mantle flow, mantle melting, and the formation of new oceanic crust. However, many of the details of this process remain obscure because of the inaccessibility of the mantle to direct observation. Thus, geodynamic models are needed to provide insight...
Error in distributed temperature sensing (DTS) water temperature measurements may be introduced by contact of the fiber optic cable sensor with bed materials (e.g., seafloor, lakebed, streambed). Heat conduction from the bed materials can affect cable temperature and the resulting DTS measurements. In the Middle Fork John Day River, apparent...
Large rivers represent gateways for the transport of
terrigenous and anthropogenic material to the coastal ocean.
Here we document a ∼700 km2 recirculation or bulge associated
with the Columbia River plume that retains recently discharged
river water sufficiently to create a regional bioreactor.
Fueled by a fluvial nitrate source, this...
We present a new high-precision, high-resolution record of atmospheric methane from the West Antarctic Ice Sheet (WAIS) Divide ice core covering 1000–1800 C.E., a time period known as the late preindustrial Holocene (LPIH). The results are consistent with previous measurements from the Law Dome ice core, the only other high-resolution...
This work advances a unified approach to process-based hydrologic modeling to enable controlled and systematic evaluation of multiple model representations (hypotheses) of hydrologic processes and scaling behavior. Our approach, which we term the Structure for Unifying Multiple Modeling Alternatives (SUMMA), formulates a general set of conservation equations, providing the flexibility...
New major and trace element and Sr, Nd, and Pb isotope data, together with ³⁹ Ar-⁴⁰Ar ages for lavas from the extinct Galapagos Rise spreading center in the eastern Pacific reveal the evolution in magma compositions erupted during slowdown and after the end of active spreading at a mid-ocean ridge....
Swash hydrodynamics were investigated on an intermediate beach using runup data obtained from video images. Under mild, near-constant, offshore wave conditions, the presence of a sandbar and the tidally controlled water depth over its crest determined whether most of the incoming waves broke before reaching the shoreline. This forced a...
Boreal summer insolation during the last interglaciation (LIG) generally warmed the subpolar to polar Northern Hemisphere more than during the early Holocene, yet regional climate variations between the two periods remain. We investigate northeast Labrador Sea subsurface temperature and hydrography across terminations (T) I and II and during the LIG...
Mid-ocean ridge volcanism and extensional faulting are the fundamental processes that lead to the creation and rifting of oceanic crust, yet these events go largely undetected in the deep ocean. Currently, the only means available to observe seafloor-spreading events in real time is via the remote detection of the seismicity...
The thermal structure of convergent margins provides information related to the tectonics, geodynamics,
metamorphism, and fluid flow of active plate boundaries. We report 176 heat flow measurements
made with a violin bow style probe across the Costa Rican margin at the Middle America Trench. The
probe measurements are collocated with...
NW Rota-1 is a submarine volcano in the Mariana volcanic arc that is notable as the site where underwater explosive eruptions were first witnessed in A. D. 2004. After years of continuous low-level eruptive activity, a major landslide occurred at NW Rota-1 in August 2009, triggered by an unusually large...
The volcanic origin of the Samoan archipelago can be explained by one of three models, specifically, by a hot spot forming over a mantle plume, by lithospheric extension resulting from complex subduction tectonics in the region, or by a combination of these two processes, either acting sequentially or synchronously. In...
Summertime low clouds are common in the Pacific Northwest (PNW), but spatiotemporal patterns have not been characterized. We show the first maps of low cloudiness for the western PNW and North Pacific Ocean using a 22‐year satellite‐derived record of monthly mean low cloudiness frequency for May through September and supplemented...
We examine the relation between δ¹⁸O in rainwater collected in southwestern Oregon
and climate variables including temperature, parcel trajectory, precipitation amount, and
specific humidity. Local surface air temperature at the time of sample collection explains a
large proportion of δ¹⁸O variability, suggesting that paleoclimatic archives that are related
to rainfall...
Sea surface temperatures (SST) and inorganic continental input over the last 25,000 years (25 ka) are reconstructed in the far eastern equatorial Pacific (EEP) based on three cores stretching from the equatorial front (~0.01°N, ME0005-24JC) into the cold tongue region (~3.6°S; TR163-31P and V19-30). We revisit previously published alkenone-derived SST...
Over the last three decades the first-order correlation in morphology and orientation of seamount trails
has been called upon to support the concept of a ‘‘fixed’’ Pacific hot spot frame of reference and to explain
the Hawaii-Emperor bend (HEB) by a dramatic change in Pacific plate motion. In this paper,...
Mineral dust particles have been shown to act as cloud condensation nuclei, and they are known to interact
with developing tropical storms over the Atlantic downwind of the Sahara. Once present within liquid
droplets, they have the potential to act as freezing ice nuclei and further affect the microphysics, dynamics,...
Abstract: Coastal upwelling zones may be at enhanced risk from ocean acidification as upwelling brings low aragonite saturation state (Ω[subscript Ar]) waters to the surface that are further suppressed by anthropogenic CO₂. Ω[subscript Ar] was calculated with pH, pCO₂, and salinity-derived alkalinity time series data from autonomous pH and pCO₂...
Oxygen isotope data from planktonic and benthic foraminifera, on a high-resolution age model (44 ¹⁴C dates spanning 17,400 years), document deglacial environmental change on the southeast Alaska margin (59°33.32′N, 144°9.21′W, 682 m water depth). Surface freshening (i.e., δ¹⁸O reduction of 0.8‰) began at 16,650 ± 170 cal years B.P. during...
Multiplicative random cascades (MRCs) can parsimoniously generate highly intermittent patterns similar to those in rainfall. The elemental MRC model parameter is the cascade weight, which determines how rainfall at one scale is partitioned at the next smallest scale in the cascade. While it is known that the probability density of...
Bathymetry and magnetic anomalies indicate that a seamount on the Juan de Fuca plate has been subducted beneath the central Cascadia accretionary complex and is now located similar to 45 km landward of the deformation front. Passage of this seamount through the accretionary complex has resulted in a pattern of...
The Blanco Transform Fault Zone (BTFZ) forms the ~350 km long Pacific–Juan de
Fuca plate boundary between the Gorda and Juan de Fuca ridges. Nearby broadband seismic networks provide a unique framework for a detailed, long-term seismotectonic study of an entire oceanic transform fault (OTF) system. We use regional waveforms...
Tropical instability waves (TIWs) are identified in three multiyear equatorial mooring records in Pacific and Atlantic cold tongues to evaluate how TIWs modulate turbulence. At 0◦ , 140 ◦W in the Pacific, TIWs are present in 43% of observations, and are associ ated with elevated vertical shear and a 40%...
Submarine volcanic eruptions and intrusions construct new oceanic crust and build long chains of volcanic islands and vast submarine plateaus. Magmatic events are a primary agent for the transfer of heat, chemicals, and even microbes from the crust to the ocean, but the processes that control these transfers are poorly...
The seasonal cycle of the near-surface circulation off central Chile was analyzed using satellite altimetry and an oceanic model. To evaluate the role of the wind stress curl on the circulation we performed two identical simulations except for the wind-forcing: the "control run" used long-term monthly mean wind stress and...
This work advances a unified approach to process-based hydrologic modeling, which we term the ‘‘Structure for Unifying Multiple Modeling Alternatives (SUMMA).’’ The modeling framework, introduced in the companion paper, uses a general set of conservation equations with flexibility in the choice of process parameterizations (closure relationships) and spatial architecture. This...
In conjunction with the USArray component of
EarthScope, long period magnetotelluric (MT) data are
being acquired in a series of arrays across the continental US.
Initial deployments in 2006 and 2007 acquired data (10–
10,000 s) at 110 sites covering the US Pacific Northwest,
distributed with the same nominal spacing...
Internal‐tide generation is usually predicted from local topography, surface tides, and stratification. However, internal tides are often observed to be unrelated to local spring‐neap forcing, appearing intermittently in 3–5 day bursts. Here we suggest a source of this intermittency by illustrating how remotely‐generated shoaling internal tides induce first‐order changes in...
This study investigated spatial-temporal variations of shear stress and bed load transport at three gravel bed river reaches of the Williams Fork River, Colorado. A two-dimensional flow model was used to compute spatial distributions of shear stress (τ) for four discharge levels between one third of bankfull (Qbf) and Qbf....