By inverting EarthScope long-period magnetotelluric (MT) data from the southeastern United States (SEUS), we obtain electrical conductivity images that provides key insights into the geodynamics of this region. Significantly, we resolve a highly electrically resistive block that extends to mantle depths beneath the modern Piedmont and Coastal Plain physiographic provinces....
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 examined long-term changes in daily streamflow associated with forestry practices with two datasets (this one and the original Alsea Streamflow dataset (1972) over a 60-year period (1959–2017) in the Alsea Watershed Study, Oregon Coast Range, Pacific Northwest, USA. In this contemporary period, 2006 to 2017 (12 water years), data...
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...
Current and hydrographic observations from the Coastal Mixing and Optics
experiment moored array, deployed from August 1996 through June 1997, are used to
describe the velocity variability and evaluate the dynamics of circulation over the New
England shelf on timescales ranging from a few days to several months. Subtidal (days...
Full Text:
mean and subtidal flow on the New England shelf,’’
J. Geophys. Res., 112, C02015, doi:10.1029
Current and hydrographic observations from the Coastal Mixing and Optics
experiment moored array, deployed from August 1996 through June 1997, are used to
describe the velocity variability and evaluate the dynamics of circulation over the New
England shelf on timescales ranging from a few days to several months. Subtidal (days...
Full Text:
mean and subtidal flow on the New England shelf,’’
J. Geophys. Res., 112, C02015, doi:10.1029
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...
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...
Here we present the first downcore results for a new paleoproxy, the Mn/Ca ratio of foraminiferal calcite, applied to sediment accumulated in the extreme Eastern Tropical North Pacific (ETNP) over the last 30,000 years. The Mn/Ca results are compared to oxygen isotopes and sea surface temperature calculated from Mg/Ca. We...
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,...
The delta O-18 signal preserved in paleoarchives is widely used to reconstruct past climate conditions. In many speleothems, this signal is classically interpreted via the amount effect. However, recent work has shown that precipitation delta O-18 (delta O-18(p)) is greatly influenced by convective processes distinct from precipitation amount, and new...
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...
Melt inclusions trapped in phenocrysts provide a unique picture of magma systems prior to modification by crustal processes. However, post-entrapment crystallization complicates their interpretation. Re-heating the phenocryst to the temperature of entrapment is a commonly applied method to recover the original melt composition. To understand the effects of re-homogenization, we...
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 investigate the freshwater composition of the shelf
and slope of the Arctic Ocean north of the New Siberian
Islands using geochemical tracer data (δ¹⁸O, Ba, and PO₄*)
collected following the extreme summer of 2007. We find
that the anomalous wind patterns that partly explained the sea
ice minimum at...
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...
An interlaboratory study of Mg/Ca and Sr/Ca ratios in three commercially available carbonate reference
materials (BAM RS3, CMSI 1767, and ECRM 752-1) was performed with the participation of
25 laboratories that determine foraminiferal Mg/Ca ratios worldwide. These reference materials containing
Mg/Ca in the range of foraminiferal calcite (0.8 mmol/mol to...
Vailulu’u seamount is an active underwater volcano that marks the end of the Samoan hotspot trail (Hart et al., 2000). Vailulu’u has a simple conical morphology (Figure 1) with a largely enclosed volcanic crater at relatively shallow water depths, ranging from 590 m (highest point on the crater rim) to...
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...
New apatite and zircon (U-Th)/He cooling ages quantify late Cenozoic exhumation patterns associated with fault activity across the Kashmir Himalaya. Apatite (U-Th)/He (AHe) cooling ages of detrital grains from the Sub-Himalayan foreland sediments indicate significant resetting. AHe data and thermal modeling reveal cooling and exhumation initiated by 4Ma at the...
The Pacific Arctic is undergoing rapid biogeochemical changes in response to warming air temperatures caused by climate forcing. This is manifesting as changes in seasonal sea ice thickness and sea ice extent, as well as changes in primary production within surface waters. The data and samples analyzed here were collected...
Climate model simulations and paleoclimate proxies are two tools that enable an understanding of the climate history of the Earth. When utilized together, they form a powerful paradigm for understanding past changes. Proxies are the only physical link to the past conditions on Earth, and models “fill in the gaps”...
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...
The primary impacts of anthropogenic CO2 emissions on marine biogeochemical cycles predicted so far include ocean acidification, global warming induced shifts in biogeographical provinces, and a possible negative feedback on atmospheric CO2 levels by CO2-fertilized biological production. Here we report a new potentially significant impact on the oxygen-minimum zones of...
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...
Surface and subsurface flow dynamics govern residence time or water age until discharge, which is a key metric of storage and water availability for human use and ecosystem function. Although observations in small catchments have shown a fractal distribution of ages, residence times are difficult to directly quantify or measure...
Full Text:
moisture dynamics, and the
old water paradox, Water Resour. Res., 46, W03514, doi:10.1029/2009WR008371
Integrated Ocean Drilling Program (IODP) Expedition 316 Sites C0006 and C0007 examined the
deformation front of the Nankai accretionary prism offshore the Kii Peninsula, Japan. In the drilling area,
the frontal thrust shows unusual behavior as compared to other regions of the Nankai Trough. Drilling
results, integrated with observations from...
The Coastal Ocean Advances in Shelf Transport (COAST) program conducted an
interdisciplinary study of coastal upwelling off central Oregon during summer 2001.
Two intensive field efforts during May–June and August 2001 were coordinated with
ocean circulation, ecosystem, and atmospheric modeling of the region. A primary
goal was to contrast the...
Volcanic eruptions are important events in Earth’s cycle of magma generation and crustal construction. Over durations of hours to years, eruptions produce new deposits of lava and/or fragmentary ejecta, transfer heat and magmatic volatiles from Earth’s interior to the overlying air or seawater, and significantly modify the landscape and perturb...
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...
In this paper, we present an approach to extracting mineralogic information from thermal infrared (TIR) spectra that is not based on an input library of pure mineral spectra nor tries to extract spectral end-members from the data. Instead, existing modal mineralogy for a number of samples are used to build...