USGS Science⌕ Search

SEARCH · USGS Science

Results for “Ocean Dynamics”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources
USGS1993

Interactions of frazil and anchor ice with sedimentary particles in a flume

Frazil and anchor ice forming in turbulent, supercooled water have been studied extensively because of problems posed to man-made hydraulic structures. In spite of many incidental observations of interactions of these ice forms with sediment, their geologic effects remain unknown. The present flume study was designed to learn about the effects of salinity, current speed, and sediment type on sediment dynamics in supercooled water. In fresh-water, frazil ice formed flocs as large as 8 cm in diameter that tended to roll along a sandy bottom and collect material from the bed. The heavy flocs often came to rest in the shelter of ripples, forming anchor ice that subsequently was buried by migrating ripples. Burial compressed porous anchor ice into ice-bonded, sediment-rich masses. This process disrupts normal ripple cross-bedding and may produce unique sedimentary structures. Salt-water flocs were smaller, incorporated less bed load, and formed less anchor ice than their fresh-water counterparts. In four experiments, frazil carried a high sediment load only for a short period in supercooled salt water, but released it with slight warming. This suggests that salt-water frazil is either sticky or traps particles only while surrounded by supercooled water (0.05 to 0.1 °C supercooling), a short-lived phase in simple, small tanks. Salt water anchor ice formed readily on blocks of ice-bonded sediment, which may be common in nature. The theoretical maximum sediment load in neutrally-buoyant ice/sediment mixture is 122 g/l, never reported in nature so far. The maximum sediment load measured in this laboratory study was 88 g/l. Such high theoretical and measured sediment concentrations suggest that frazil and anchor ice are important sediment transport agents in rivers and oceans.

Cold Regions Science and Technology↗
USGS2001

Using multiple geochemical tracers to characterize the hydrogeology of the submarine spring off Crescent Beach, Florida

A spectacular submarine spring is located about 4 km east of Crescent Beach, FL, in the Atlantic Ocean. The single vent feature of Crescent Beach Spring provides a unique opportunity to examine onshore–offshore hydrogeologic processes, as well as point source submarine ground water discharge. The Floridan aquifer system in northeastern Florida consists of Tertiary interspersed limestone and dolomite strata. Impermeable beds confine the water-bearing zones under artesian pressure. Miocene and younger confining strata have been eroded away at the vent feature, enabling direct hydrologic communication of Eocene ground water with coastal bottom waters. The spring water had a salinity of 6.02, which was immediately diluted by ambient seawater during advection/mixing. The concentration of major solutes in spring water and onshore well waters confirm a generalized easterly flow direction of artesian ground water. Nutrient concentrations were generally low in the reducing vent samples, and the majority of the total nitrogen species existed as NH 3 . The submarine ground water tracers, Rn-222 (1174 dpm l −1 , dpm), methane (232 nM) and barium (294.5 nM) were all highly enriched in the spring water relative to ambient seawater. The concentrations of the reverse redox elements U, V and Mo were expectedly low in the submarine waters. The strontium isotope ratio of the vent water ( 87 Sr/ 86 Sr=0.70798) suggests that the spring water contain an integrated signature indicative of Floridan aquifer system ground water. Additional Sr isotopic ratios from a series of surficial and Lower Floridan well samples suggest dynamic ground water mixing, and do not provide clear evidence for a single hydrogeologic water source at the spring vent. In this karst-dominated aquifer, such energetic mixing at the vent feature is expected, and would be facilitated by conduit and fractured flow. Radium isotope activities were utilized to estimate flow-path trajectories and to provide information on potential travel times between an onshore well and the spring. Using either 223 Ra and 224 Ra or 228 Ra, and qualifying this approach with several key assumptions, estimates of water mass travel times from an upper Floridan well in Crescent Beach to the submarine vent feature (distance=4050 m) are in the order of ∼0.01–0.1 m min −1 .

Florida↗
USGS2007

Effect of storms on barrier island dynamics, Core Banks, Cape Lookout National Seashore, North Carolina, 1960-2001

The effect of storms on long-term dynamics of barrier islands was evaluated on Core Banks, a series of barrier islands that extend from Cape Lookout to Okracoke Inlet in the Cape Lookout National Seashore, North Carolina. Shoreline and elevation changes were determined by comparing 77 profiles and associated reference markers established by the U.S. Army Corps of Engineers (USACE) on Core Banks from June 1960 to July 1962 to a follow-up survey by Godfrey and Godfrey (G&G) in 1971 and a survey by the Department of Geology at East Carolina University (ECU) in 2001, in which 57 of the original 77 profiles were located. Evaluation of the baseline data associated with the USACE study supplies an important record of barrier island response to two specific storm events—Hurricane Donna in September 1960 and the Ash Wednesday extra-tropical cyclone in March 1962. The 1962 USACE survey was followed by 9 years characterized by no major storms; this low-energy period was captured by the G&G survey in 1971. The G&G survey was followed by 22 years characterized by occasional small to moderate storms. Starting in 1993, however, and continuing through 1999, the North Carolina coast experienced a major increase in storm activity, with seven major hurricanes impacting Core Banks. Both the USACE 1960–1962 and G&G 1962–1971 surveys produced short-term data sets that reflected very different sets of weather conditions. The ECU 2001 survey data were then compared with the USACE 1960 survey data to develop a long-term (41 years) data set for shoreline erosion on Core Banks. Those resulting long-term data were compared with the long-term (52 years) data sets by the North Carolina Division of Coastal Management (NCDCM) from 1940–1992 and 1946–1998; a strong positive correlation and very similar rates of average annual erosion resulted. However, the ECU and NCDCM long-term data sets did not correlate with either of the USACE and G&G short-term survey data and had very different average annual erosion rates. The average annual long-term rate of shoreline erosion for all of Core Banks and for both the ECU 1960–2001 and the NCDCM 1946–1998 surveys was -5 feet per year (ft/yr). These long-term rates of shoreline recession are in strong contrast with the short-term, storm-dominated rates of shoreline erosion for all of Core Banks developed by the USACE 1960–1961 and USACE 1961–1962 surveys, which have average annual erosion rates of -40 ft/yr and -26 ft/yr, respectively, and range from -226 feet (ft) to +153 ft. The combined short-term, storm-dominated shoreline erosion rate for the USACE surveys (1960–1962) was -36 ft/yr. In contrast, the average annual short-term, non-stormy period G&G 1962–1971 survey demonstrated shoreline accretion for all of Core Banks with an average annual rate of +12 ft/yr. In general, North Core Banks has higher erosion and accretion rates than South Core Banks. In the 1961 survey, the USACE installed 231 reference markers (RM-0 is closest to the ocean and RM-2 is farthest from the ocean) along the 77 profiles, as well as 33 reference markers labeled RM-4, RM-6, and RM-8 in the wider portions of the islands. The G&G survey recovered a total of 141 reference markers (61 percent), and the ECU survey recovered a total of 83 reference markers (36 percent) of the RM-0, RM-1, and RM-2 markers. The average ground elevation measured by the USACE in 1961 was RM-0 = +5.8 ft, RM-1 = +5.2 ft, and RM-2 = +4.8 ft. The G&G 1970 survey measured average ground elevations of RM-0 = +6.7 ft, RM-1 = +6.4 ft, and RM-2 = +6.1 ft, and the average ground elevation measured by ECU in 2001 was RM-0 = +10.1 ft, RM-1 = +9.1 ft, and RM-2 = +8.5 ft. The latter numbers represent approximately an overall 72-percent increase in island elevation from 1961 to 2001. Based on aerial photographic time-slice analyses, it is hypothesized that this increase in island elevation occurred during the post-1962 period with storm overwash systematically raising the island elevation through time, which in turn led to decreased numbers of overwash events. The latter processes and responses in turn led to a substantial increase in vegetative growth on the barrier island, as well as submerged aquatic vegetation on the back-barrier sand shoals. Integration of the USACE, G&G, ECU, and NCDCM shoreline erosion data for Core Banks shows several important points about shoreline recession. (1) The ECU and NCDCM data sets demonstrate that there is an ongoing net, long-term, but small-scale shoreline recession associated with Core Banks; (2) the USACE short-term data sets demonstrate that processes associated with individual storm events or sets of events produce extremely large-scale changes that include both erosion and accretion; (3) the short-term, non-stormy period data set of G&G demonstrates that if given enough time between storm events, barriers can rebuild to their pre-storm period conditions; and (4) the post-storm response generally tends to approach the pre-storm location, but rarely reaches it before the next storm or stormy period sets in. The result is the net long-term change documented by both the ECU 1960–2001 and NCDCM 1946–1998 Core Banks data sets that resulted in erosion rates ranging from 0 to -30 ft/yr with net annual average recession rates of -5 ft/yr. Analysis and comparison of these data sets supply important information for understanding the dynamics and responses of barrier island systems through time. In addition, the results of the present study on Core Banks supply essential process-response information that can be used to design and implement management plans for the Cape Lookout and Cape Hatteras National Seashores and for other seashores in the U.S. National Park Service system.

North Carolina↗
USGS2012

Storm‐dominated bottom boundary layer dynamics on the Northern California Continental Shelf: Measurements and predictions

Measurements of near‐bottom velocity profiles in 85 m water depth during a storm on the continental shelf off northern California using the GEOPROBE tripod in December 1979 provided estimates of shear velocities, , and roughness lengths, , when the near‐bottom velocity profiles were logarithmic. These estimates agree within 90% confidence intervals with values computed from a simple near‐bottom combined wave‐current model that includes movable bed effects. The reasonably good comparison between model and profile estimates of suggests that such models can be used to predict bed shear stresses (or shear velocities) under combined flows of waves and currents typical of stormy conditions on continental shelves if stratification corrections to the velocity profile resulting from suspended sediment are small. The repeated occurrences of storms of similar intensities and wind velocities during the winter months off northern California suggest that the resultant high bottom stresses due to the combined effects of waves and currents are major factors in controlling the distribution of surficial sediment on the central portion of the northern California shelf.

California↗
USGS2011

Sediment dynamics and the burial and exhumation of bedrock reefs along an emergent coastline as elucidated by repetitive sonar surveys: Northern Monterey Bay, CA

Two high-resolution bathymetric and acoustic backscatter sonar surveys were conducted along the energetic emergent inner shelf of northern Monterey Bay, CA, USA, in the fall of 2005 and the spring of 2006 to determine the impact of winter storm waves, beach erosion, and river floods on biologically-important siliclastic bedrock reef habitats. The surveys extended from water depths of 4 m to 22 m and covered an area of 3.14 km2, 45.8% of which was bedrock, gravel, and coarse-grained sand and 54.2% was fine-grained sand. Our analyses of the bathymetric and acoustic backscatter data demonstrates that during the 6 months between surveys, 11.4% of the study area was buried by fine-grained sand while erosion resulted in the exposure of bedrock or coarse-grained sand over 26.5% of the study area. The probability of burial decreased with increasing water depth and rugosity; the probability of exhumation increased with increasing wave-induced near-bed shear stress, seabed slope and rugosity. Much of the detected change was at the boundary between bedrock and unconsolidated sediment due to sedimentation and erosion burying or exhuming bedrock, respectively. In a number of cases, however, the change in seabed character was apparently due to changes in sediment grain size when scour exposed what appeared to be an underlying coarser-grained lag or the burial of coarser-grained sand and gravel by fine-grained sand. These findings suggest that, in some places, (a) burial and exhumation of nearshore bedrock reefs along rocky, energetic inner shelves occurs over seasonal timescales and appears related to intrinsic factors such as seabed morphology and extrinsic factors such as wave forces, and (b) single acoustic surveys typically employed for geologic characterization and/or habitat mapping may not adequately characterize the geomorphologic and sedimentologic nature of these types of environments that typify most of the Pacific Ocean and up to 50% of the world's coastlines.

Monterey Bay↗
USGS2018

The nitrogen window for arctic herbivores: plant phenology and protein gain of migratory caribou (Rangifer tarandus)

Terrestrial plants are often limited by nitrogen (N) in arctic systems, but constraints of N supply on herbivores are typically considered secondary to those of energy. We tested the hypothesis that forage N is more limiting than energy for arctic caribou by collecting key forages (three species of graminoids, three species of woody browse, and one genus of forb) over three summers in the migratory range of the Central Arctic Herd in Alaska from the Brooks Range to the Coastal Plain on the Arctic Ocean. We combined in vitro digestion and detergent extraction to measure fiber, digestible energy, and usable fractions of N in forages ( n = 771). Digestible energy content fell below the minimum threshold value of 9 kJ/g for one single forage group: graminoids, and only beyond 64–75 d from parturition (6 June), whereas all forages fell below the minimum threshold value for digestible N (1% of dry matter) before female caribou would have weaned their calves at 100 d from parturition. The window for digestible N was shortest for browse, which fell below 1% at 30–41 d from parturition, whereas digestible N contents of graminoids were adequate until 46–57 d from parturition. The low quality of browse as a source of N was also apparent from concentrations of available N (i.e., the N not bound to fiber) that were <1% at 72–80 d from parturition. The Coastal Plain may be favored by female caribou because available and digestible concentrations of N are not only greater than those on the Brooks Range, the window of usable N on the Coastal Plain extends the period of protein gain for females and their calves by 17 d. Conversely, inland areas with greater biomass and densities of digestible N than the Coastal Plain may be more favorable for large male caribou that begin gaining protein from spring to breed in autumn. Our study provides evidence that phenological windows for protein gain in caribou are both spatially and temporally dynamic and likely to affect the distribution and growth of the population.

Ecosphere↗
USGS2013

Assessing factors affecting the thermal properties of a passive thermal refuge using three-dimensional hydrodynamic flow and transport modeling

Everglades restoration activities may cause changes to temperature and salinity stratification at the Port of the Islands (POI) marina, which could affect its suitability as a cold weather refuge for manatees. To better understand how the Picayune Strand Restoration Project (PSRP) may alter this important resource in Collier County in southwestern Florida, the USGS has developed a three-dimensional hydrodynamic model for the marina and canal system at POI. Empirical data suggest that manatees aggregate at the site during winter because of thermal inversions that provide warmer water near the bottom that appears to only occur in the presence of salinity stratification. To study these phenomena, the environmental fluid dynamics code simulator was used to represent temperature and salinity transport within POI. Boundary inputs were generated using a larger two-dimensional model constructed with the flow and transport in a linked overland-aquifer density-dependent system simulator. Model results for a representative winter period match observed trends in salinity and temperature fluctuations and produce temperature inversions similar to observed values. Modified boundary conditions, representing proposed PSRP alterations, were also tested to examine the possible effect on the salinity stratification and temperature inversion within POI. Results show that during some periods, salinity stratification is reduced resulting in a subsequent reduction in temperature inversion compared with the existing conditions simulation. This may have an effect on POI’s suitability as a passive thermal refuge for manatees and other temperature-sensitive species. Additional testing was completed to determine the important physical relationships affecting POI’s suitability as a refuge.

Florida↗
USGS2018

Three-dimensional modeling of fine sediment transport by waves and currents in a shallow estuary

A suspended sediment transport model is implemented in the unstructured‐grid SUNTANS model and applied to study fine‐grained sediment transport in South San Francisco Bay. The model enables calculation of suspension of bottom sediment based on combined forcing of tidal currents and wind waves. We show that accurate results can be obtained by employing two‐size classes which are representative of microflocs and macroflocs in the Bay. A key finding of the paper is that the critical calibration parameter is the ratio of the erosion of the microflocs to macroflocs from the bed. Different values of this erosion ratio are needed on the shallow shoals and deeper channels because of the different nature of the sediment dynamics in these regions. Application of a spatially variable erosion ratio and critical shear stress for erosion is shown to accurately reproduce observed suspended sediment concentration at four‐field sites located along a cross‐channel transect. The results reveal a stark contrast between the behavior of the suspended sediment concentration on the shoals and in the deep channel. Waves are shown to resuspend sediments on the shoals, although tidal and wind‐generated currents are needed to mix the thin wave‐driven suspensions into the water column. The contribution to the suspended sediment concentration in the channel by transport from the shoals is similar in magnitude to that due to local resuspension. However, the local contribution is in phase with strong bottom currents which resuspend the sediments, while the contribution from the shoals peaks during low‐water slack tide.

San Francisco Bay↗
USGS1998

On the influence of biomass burning on the seasonal CO2 signal as observed at monitoring stations

We investigated the role of biomass burning in simulating the seasonal signal in both prognostic and diagnostic analyses. The prognostic analysis involved the High-Resolution Biosphere Model, a prognostic terrestrial biosphere model, and the coupled vegetation fire module, which together produce a prognostic data set of biomass burning. The diagnostic analysis involved the Simple Diagnostic Biosphere Model (SDBM) and the Hao and Liu [1994] diagnostic data set of biomass burning, which have been scaled to global 2 and 4 Pg C yr −1 , respectively. The monthly carbon exchange fields between the atmosphere and the biosphere with a spatial resolution of 0.5° × 0.5°, the seasonal atmosphere-ocean exchange fields, and the emissions from fossil fuels have been coupled to the three-dimensional atmospheric transport model TM2. We have chosen eight monitoring stations of the National Oceanic and Atmospheric Administration network to compare the predicted seasonal atmospheric CO 2 signals with those deduced from atmosphere-biosphere carbon exchange fluxes without any contribution from biomass burning. The prognostic analysis and the diagnostic analysis with global burning emissions of 4 Pg C yr −1 agree with respect to the change in the amplitude of the seasonal CO 2 concentration introduced through biomass burning. We find that the seasonal CO 2 signal at stations in higher northern latitudes (north of 30°N) is marginally influenced by biomass burning. For stations in tropical regions an increase in the CO 2 amplitude of more than 1 ppmv (up to 50% with respect to the observed trough to peak amplitude) has been calculated. Biomass burning at stations farther south accounts for an increase in the CO 2 amplitude of up to 59% (0.6 ppmv). A change in the phase of the seasonal CO 2 signal at tropical and southern stations has been shown to be strongly influenced by the onset of biomass burning in southern tropical Africa and America. Comparing simulated and observed seasonal CO 2 signals, we find higher discrepancies at southern tropical stations if biomass burning emissions are included. This is caused by the additional increase in the amplitude in the prognostic analysis and a phase shift in a diagnostic analysis. In contrast, at the northern tropical stations biomass burning tends to improve the estimates of the seasonal CO 2 signal in the prognostic analysis because of strengthening of the amplitude. Since the SDBM predicts the seasonal CO 2 signal reasonably well for the northern hemisphere tropical stations, no general improvement of the fit occurs if biomass burning emissions are considered.

Global Biogeochemical Cycles↗
USGS2018

Evaluating the potential for near-shore bathymetry on the Majuro Atoll, Republic of the Marshall Islands, using Landsat 8 and WorldView-3 imagery

Satellite-derived near-shore bathymetry (SDB) is becoming an increasingly important method for assessing vulnerability to climate change and natural hazards in low-lying atolls of the northern tropical Pacific Ocean. Satellite imagery has become a cost-effective means for mapping near-shore bathymetry because ships cannot collect soundings safely while operating close to the shore. Also, green laser light detection and ranging (lidar) acquisitions are expensive in remote locations. Previous research has demonstrated that spectral band ratio-based techniques, commonly called the natural logarithm approach, may lead to more precise measurements and modeling of bathymetry because of the phenomenon that different substrates at the same depth have approximately equal ratio values. The goal of this research was to apply the band ratio technique to Landsat 8 at-sensor radiance imagery and WorldView-3 atmospherically corrected imagery in the coastal waters surrounding the Majuro Atoll, Republic of the Marshall Islands, to derive near-shore bathymetry that could be incorporated into a seamless topobathymetric digital elevation model of Majuro. Attenuation of light within the water column was characterized by measuring at-sensor radiance and reflectance at different depths and calculating an attenuation coefficient. Bathymetric lidar data, collected by the U.S. Naval Oceanographic Office in 2006, were used to calibrate the SDB results. The bathymetric lidar yielded a strong linear relation with water depths. The Landsat 8-derived SDB estimates derived from the blue/green band ratio exhibited a water attenuation extinction depth of 6 meters with a coefficient of determination R 2 =0.9324. Estimates derived from the coastal/red band ratio had an R 2 =0.9597. At the same extinction depth, SDB estimates derived from WorldView-3 imagery exhibited an R 2 =0.9574. Because highly dynamic coastal shorelines can be affected by erosion, wetland loss, hurricanes, sea-level rise, urban development, and population growth, consistent bathymetric data are needed to better understand sensitive coastal land/water interfaces in areas subject to coastal disasters.

Majuro Atoll↗
USGS2025

River-to-lake transitional areas contribute disproportionately to in-lake nutrient loading

River-to-lake transitional areas are biogeochemically active sections of the aquatic continuum that are often understudied compared to their adjoining environments. Internal nutrient loading from river-to-lake transitional areas may be a considerable source of nutrients to lakes and if overlooked disconnect upstream management initiatives from in-lake improvements. To contextualize internal nutrient loading by river-to-lake sediments, we conducted sediment core incubations and nutrient assays at 3 time points over a field season from a major contributing tributary of Lake Erie. Using statistical and spatial interpolation models, we upscaled internal nitrogen and phosphorus loading rates across the highly impaired mouth of the Maumee River, which drains into the western basin of Lake Erie. We found that internal nutrient dynamics in this river-to-lake transitional area were regulated by spatial differences in the physical composition and nutrient and organic matter contents of sediments. The Maumee river-to-lake transitional area was largely a source of phosphorus and ammonium nitrogen and a sink of nitrate nitrogen through high denitrification rates. Yet, we observed substantial temporal variation whereby internal nutrient loading was greatest in late summer coinciding with near-zero denitrification. Sediments at this time could contribute an additional ~17% more soluble reactive phosphorus and ~3% more total kjeldahl nitrogen in the bioavailable ammonium nitrogen fraction relative to the daily external nutrient load. High internal nutrient loading rates compared to more offshore areas in western Lake Erie suggest that this degraded river-to-lake transitional area has a disproportional biogeochemical significance and a high potential to contribute to nearshore water quality issues.

Ohio↗
USGS2021

Preliminary assessment of the wave generating potential from landslides at Barry Arm, Prince William Sound, Alaska

We simulated the concurrent rapid motion of landslides on an unstable slope at Barry Arm, Alaska. Movement of landslides into the adjacent fjord displaced fjord water and generated a tsunami, which propagated out of Barry Arm. Rather than assuming an initial sea surface height, velocity, and location for the tsunami, we generated the tsunami directly using a model capable of simulating the dynamics of both water and landslide material. The fjord below most of the landslide source area was occupied by the Barry Glacier until about 2012; therefore, our direct simulation of tsunami generation by landslide motion required new topographic and bathymetric data, which was collected in 2020. The topographic data also constrained landslide geometries and volumes. We considered four scenarios based on two landslide volumes and two landslide mobilities—a more mobile, contractive landslide and a less mobile, noncontractive landslide. The larger of the two volumes is 689 × 10 6 cubic meters (m 3 )—larger than the volume estimate in a previous study—and reflects the largest plausible volume given current observational data. The considered scenario that generated the largest wave heights resulted in forecast wave heights of over 200 meters (m) in the northern part of Barry Arm, adjacent to the landslide source area and runup on the opposite fjord wall in excess of 500 m. Simulated wave heights in excess of 5 m in southern Barry Arm and in Harriman Fjord occurred within 10–15 minutes (min) of landslide motion. The simulated tsunami reached Whittier, Alaska, approximately 20 min after initial rapid landslide motion, with peak heights of just over 2 m in Passage Fjord, 500 m offshore Whittier, occurring 26 min after initial rapid motion. Time of peak wave heights was consistent with previous modeling. Although results are preliminary and can be refined with additional observations and analyses, they provide a refined assessment of the upper bound of the hazard presented by the Barry Arm landslides. The results herein support the National Oceanic and Atmospheric Administration’s National Tsunami Warning Center mission to detect, forecast, and warn for tsunamis in Alaska.

Alaska↗
USGS2003

Regional sediment budget of the Columbia River littoral cell, USA: Analysis of bathymetric- and topographic-volume change

In this Open-File Report we present calculations of changes in bathymetric and topographic volumes for the Grays Harbor, Willapa Bay, and Columbia River entrances and the adjacent coasts of North Beach, Grayland Plains, Long Beach, and Clatsop Plains for four intervals: pre-jetty - 1920s (Interval 1), 1920s - 1950s (Interval 2), 1950s - 1990s (Interval 3), and 1920s 1990s (Interval 4). This analysis is part of the Southwest Washington Coastal Erosion Study (SWCES), the goals of which are to understand and predict the morphologic behavior of the Columbia River littoral cell on a management scale of tens of kilometers and decades. We obtain topographic Light Detection and Ranging (LIDAR) data from a joint project by the U.S. Geological Survey (USGS), National Oceanic and Atmospheric Administration (NOAA), National Aeronautic and Space Administration (NASA), and the Washington State Department of Ecology (DOE) and bathymetric data from the U.S. Coast and Geodetic Survey (USC&GS), U.S. Army Corps of Engineers (USACE), USGS, and the DOE. Shoreline data are digitized from T-Sheets and aerial photographs from the USC&GS and National Ocean Service (NOS). Instead of uncritically adjusting each survey to NAVD88, a common vertical land-based datum, we adjust some surveys to produce optimal results according to the following criteria. First, we minimize offsets in overlapping surveys within the same era, and second, we minimize bathymetric changes (relative to the 1990s) in deep water, where we assume minimal change has taken place. We grid bathymetric and topographic datasets using kriging and triangulation algorithms, calculate bathymetric-change surfaces for each interval, and calculate volume changes within polygons that are overlaid on the bathymetric-change surfaces. We find similar morphologic changes near the entrances to Grays Harbor and the Columbia River following jetty construction between 1898 and 1916 at the Grays Harbor entrance and between 1885 and 1913 at the Columbia River entrance. The inlets and inner deltas eroded and the outer deltas moved offshore and accreted. The adjacent coasts experienced accretion over alongshore distances of tens of kilometers. North of the Grays Harbor entrance along North Beach and north of the Columbia River entrance along Long Beach the shoreface and the beach-dune complex mainly prograded, whereas south of the Grays Harbor entrance along Grayland Plains and south of the Columbia River entrance along Clatsop Plains the beach-dune complex above -10 m NAVD88 prograded and the shoreface between approximately -30 m and -10 m NAVD88 eroded. In the decades following jetty construction, the rates of erosion and accretion at the entrances decreased and the centers of deposition along the adjacent coasts moved away from the entrances. The rates of change have decreased, suggesting the systems are approaching dynamic equilibrium. Exceptions to this behaviour are the accretion of the beach-dune complex of Long Beach, the erosion of Cape Shoalwater, and the northward migration of the Willapa Bay ebb-tidal delta during all intervals. The net shoreline advance of Long Beach increases from 0.28 m/yr in pre-jetty conditions to 3.78 m/yr during Interval 4. The erosion of Cape Shoalwater and the northward migration of the Willapa Bay ebb-tidal delta are related to the northern migration of the Willapa Bay North Channel. Volume changes at the Grays Harbor, Willapa Bay, and Columbia River entrances and the Columbia River estuary are balanced against losses and gains due to littoral transport and sand supply from the Columbia River. Based on these sediment balances, we infer the following pathways: sand that eroded from the inlets and inner deltas at the Grays Harbor and Columbia River entrances moved offshore and northward to accrete the outer deltas and the beaches to the north; sand from the south flank of the Grays Harbor delta and shelf along Grayland Plains moved onshore to accrete the beach dune complex of Grayland Plains and moved northward to maintain accretion of the outer delta and the beach-dune complex of North Beach; sand that eroded from the south flank of the Columbia River delta and shelf along Clatsop Plains contributed to the accretion of the beach-dune complex of Clatsop Plains and the Columbia River outer delta. The net volume change for Interval 1 and 3 at the Grays Harbor entrance and for Interval 1 at the Columbia River entrance is erosion, whereas the net change for the other intervals is accretion. For the entire CRLC, there is a net loss of 185 Mm 3 for Interval 1, a net gain of 357 Mm 3 for Interval 2, and a net gain of 187 Mm 3 for Interval 3. These imbalances can be the result of incomplete bathymetric coverage of the bays and shoreface, uncertainties in the adjustments of vertical tidal datums, inconsistencies in the bathymetric data, and uncertainties in the sediment supply of the Columbia River.

Oregon, Washington↗
USGS2012

Anchor ice, seabed freezing, and sediment dynamics in shallow arctic seas

Diving investigations confirm previous circumstantial evidence of seafloor freezing and anchor ice accretion during freeze-up storms in the Alaskan Beaufort Sea. These related bottom types were found to be continuous from shore to 2-m depth and spotty to 4.5-m depth. Spotty anchor ice occurred as pillow-shaped crystal aggregates on buried slabs of frozen sand surrounded by unfrozen sand. Considerations of required conditions for ice bonding and anchor ice growth allows regional extrapolation and suggests the possibility of anchor ice growth out to 20-m depth, the estimated maximum depth of supercooling during fall storms. Anchor ice and seabed freezing apparently do not develop during a calm freeze-up. Because of the abrupt growth of anchor ice during a freezing storm and its release soon after formation of a surface ice cover, this ice type has not been documented before. The concretelike nature of frozen bottom, where present, should prohibit sediment transport by any conceivable wave or current regime during the freezing storm. But elsewhere, particularly where the bonded crust is broken by grounded ice, anchor ice lifts coarse material off the bottom and incorporates it into the ice canopy, thereby leading to significant ice rafting of shallow shelf sediment and likely sediment loss to the deep sea.

Journal of Geophysical Research-Oceans↗
USGS2012

Validation of a coupled wave-flow model in a high-energy setting: the mouth of the Columbia River

A monthlong time series of wave, current, salinity, and suspended-sediment measurements was made at five sites on a transect across the Mouth of Columbia River (MCR). These data were used to calibrate and evaluate the performance of a coupled hydrodynamic and wave model for the MCR based on the Delft3D modeling system. The MCR is a dynamic estuary inlet in which tidal currents, river discharge, and wave-driven currents are all important. Model tuning consisted primarily of spatial adjustments to bottom drag coefficients. In combination with (near-) default parameter settings, the MCR model application is able to simulate the dominant features in the tidal flow, salinity and wavefields observed in field measurements. The wave-orbital averaged method for representing the current velocity profile in the wave model is considered the most realistic for the MCR. The hydrodynamic model is particularly effective in reproducing the observed vertical residual and temporal variations in current structure. Density gradients introduce the observed and modeled reversal of the mean flow at the bed and augment mean and peak flow in the upper half of the water column. This implies that sediment transport during calmer summer conditions is controlled by density stratification and is likely net landward due to the reversal of flow near the bed. The correspondence between observed and modeled hydrodynamics makes this application a tool to investigate hydrodynamics and associated sediment transport.

Oregon, Washington↗
USGS2001

Coastal change analysis program implemented in Louisiana

Landsat Thematic Mapper images from 1990 to 1996 and collateral data sources were used to classify the land cover of the Mermentau River Basin (MRB) within the Chenier Plain of coastal Louisiana. Landcover classes followed the definition of the National Oceanic and Atmospheric Administration's Coastal Change Analysis Program; however, classification methods had to be developed as part of this study for attainment of these national classification standards. Classification method developments were especially important when classes were spectrally inseparable, when classes were part of spatial and spectral continuums, when the spatial resolution of the sensor included more than one landcover type, and when human activities caused abnormal transitions in the landscape. Most classification problems were overcome by using one or a combination of techniques, such as separating the MRB into subregions of commonality, applying masks to specific land mixtures, and highlighting class transitions between years that were highly unlikely. Overall, 1990, 1993, and 1996 classification accuracy percentages (associated kappa statistics) were 80% (0.79), 78% (0.76), and 86% (0.84), respectively. Most classification errors were associated with confusion between managed (cultivated land) and unmanaged grassland classes; scrub shrub, grasslands and forest classes; water, unconsolidated shore and bare land classes; and especially in 1993, between water and floating vegetation classes. Combining cultivated land and grassland classes and water and floating vegetation classes into single classes accuracies for 1990, 1993, and 1996 increased to 82%, 83%, and 90%, respectively. To improve the interpretation of landcover change, three indicators of landcover class stability were formulated. Location stability was defined as the percentage of a landcover class that remained as the same class in the same location at the beginning and the end of the monitoring period. Residence stability was defined as the percent change in each class within the entire MRB during the monitoring period. Turnover was defined as the addition of other landcover classes to the target landcover class during the defined monitoring period. These indicators allowed quick assessment of the dynamic nature of landcover classes, both in reference to a spatial location and to retaining their presence throughout the MRB. Examining the landcover changes between 1990 to 1993 and 1993 to 1996, led us to five principal findings: (1) Landcover turnover is maintaining a near stable logging cycle, although the locations of grassland, scrub shrub, and forest areas involved in the cycle appeared to change. (2) Planting of seedlings is critical to maintaining cycle stability. (3) Logging activities tend to replace woody land mixed forests with woody land evergreen forests. (4) Wetland estuarine marshes are expanding slightly. (5) Wetland palustrine marshes and mature forested wetlands in the MRB are relatively stable.

Louisiana↗
USGS2011

A behavior-oriented dynamic model for sandbar migration and 2DH evolution

A nonlinear model is developed to study the time‐dependent relationship between the alongshore variability of a sandbar, a ( t ), and alongshore‐averaged sandbar position, x c ( t ). Sediment transport equations are derived from energetics‐based formulations. A link between this continuous physical representation and a parametric form describing the migration of sandbars of constant shape is established through a simple transformation of variables. The model is driven by offshore wave conditions. The parametric equations are dynamically coupled such that changes in one term (i.e., x c ) drive changes in the other (i.e., a ( t )). The model is tested on 566 days of data from Palm Beach, New South Wales, Australia. Using weighted nonlinear least squares to estimate best fit model coefficients, the model explained 49% and 41% of the variance in measured x c and a ( t ), respectively. Comparisons against a 1‐D horizontal (1DH) version of the model showed significant improvements when the 2DH terms were included (1DH and 2DH Brier skill scores were −0.12 and 0.42, respectively). Onshore bar migration was not predicted in the 1DH model, while the 2DH model correctly predicted onshore migration in the presence of 2DH morphology and allowed the bar to remain closer to shore for a given amount of breaking, providing an important hysteresis to the system. The model is consistent with observations that active bar migration occurs under breaking waves with onshore migration occurring at timescales of days to weeks and increasing 2DH morphology, while offshore migration occurs rapidly under high waves and coincides with a reduction in 2DH morphology.

Journal of Geophysical Research C: Oceans↗
USGS1998

Greenland Sea Odden sea ice feature: Intra-annual and interannual variability

The “Odden” is a large sea ice feature that forms in the east Greenland Sea that may protrude eastward to 5°E from the main sea ice pack (at about 8°W) between 73° and 77°N. It generally forms at the beginning of the winter season and can cover 300,000 km 2 . Throughout the winter the outer edge of the Odden may advance and retreat by several hundred kilometers on timescales of a few days to weeks. Satellite passive microwave observations from 1978 through 1995 provide a continuous record of the spatial and temporal variations of this extremely dynamic phenomenon. Aircraft synthetic aperture radar, satellite passive microwave, and ship observations in the Odden show that the Odden consists of new ice types, rather than older ice types advected eastward from the main pack. The 17-year record shows both strong interannual and intra-annual variations in Odden extent and temporal behavior. For example, in 1983 the Odden was weak, in 1984 the Odden did not occur, and in 1985 the Odden returned late in the season. An analysis of the ice area and extent time series derived from the satellite passive microwave observations along with meteorological data from the International Arctic Buoy Program (IABP) determined the meteorological forcing associated with Odden growth, maintenance, and decay. The key meteorological parameters that are related to the rapid ice formation and decay associated with the Odden are, in order of importance, air temperature, wind speed, and wind direction. Oceanographic parameters must play an important role in controlling Odden formation, but it is not yet possible to quantify this role because of a lack of long-term oceanographic observations.

Journal of Geophysical Research C: Oceans↗