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41.
42.
Sea level variability along the US West Coast is analyzed using multi-year time series records from tide gauges and a high-resolution regional ocean model, the base of the West Coast Ocean Forecast System (WCOFS). One of the metrics utilized is the frequency of occurrences when model prediction is within 0.15 m from the observed sea level, F. A target level of F?=?90% is set by an operational agency. A combination of the tidal sea level from a shallow water inverse model, inverted barometer (IB) term computed using surface air pressure from a mesoscale atmospheric model, and low-pass filtered sea level from WCOFS representing the effect of coastal ocean dynamics (DYN) provides the most straightforward approach to reaching levels F>80%. The IB and DYN components each add between 5 and 15% to F. Given the importance of the DYN term bringing F closer to the operational requirement and its role as an indicator of the coastal ocean processes on scales from days to interannual, additional verification of the WCOFS subtidal sea level is provided in terms of the model-data correlation, standard deviation of the band-pass filtered (2–60 days) time series, the annual cycle amplitude, and alongshore sea level coherence in the range of 5–120-day periods. Model-data correlation in sea level increases from south to north along the US coast. The rms amplitude of model sea level variability in the 2–60-day band and its annual amplitude are weaker than observed north of 42 N, in the Pacific Northwest (PNW) coast region. The alongshore coherence amplitude and phase patterns are similar in the model and observations. Availability of the multi-year model solution allows computation and analysis of spatial maps of the coherence amplitude. For a reference location in the Southern California Bight, relatively short-period sea level motions (near 10 days) are incoherent with those north of the Santa Barbara Channel (in part, due to coastal trapped wave scattering and/or dissipation). At a range of periods around 60 days, the coastal sea level in Southern California is coherent with the sea surface height (SSH) variability over the shelf break in Oregon, Washington, and British Columbia, more than with the coastal SSH at the same latitudes. 相似文献
43.
Mohamad R. Soltanian Mohammad A. Amooie David R. Cole Thomas H. Darrah David E. Graham Susan M. Pfiffner Tommy J. Phelps Joachim Moortgat 《Ground water》2018,56(2):176-186
In the context of geological carbon sequestration (GCS), carbon dioxide (CO2) is often injected into deep formations saturated with a brine that may contain dissolved light hydrocarbons, such as methane (CH4). In this multicomponent multiphase displacement process, CO2 competes with CH4 in terms of dissolution, and CH4 tends to exsolve from the aqueous into a gaseous phase. Because CH4 has a lower viscosity than injected CO2, CH4 is swept up into a ‘bank’ of CH4‐rich gas ahead of the CO2 displacement front. On the one hand, this may provide a useful tracer signal of an approaching CO2 front. On the other hand, the emergence of gaseous CH4 is undesirable because it poses a leakage risk of a far more potent greenhouse gas than CO2 if the cap rock is compromised. Open fractures or faults and wells could result in CH4 contamination of overlying groundwater aquifers as well as surface emissions. We investigate this process through detailed numerical simulations for a large‐scale GCS pilot project (near Cranfield, Mississippi) for which a rich set of field data is available. An accurate cubic‐plus‐association equation‐of‐state is used to describe the non‐linear phase behavior of multiphase brine‐CH4‐CO2 mixtures, and breakthrough curves in two observation wells are used to constrain transport processes. Both field data and simulations indeed show the development of an extensive plume of CH4‐rich (up to 90 mol%) gas as a consequence of CO2 injection, with important implications for the risk assessment of future GCS projects. 相似文献
44.
Yousif K. Kharaka James J. Thordsen Susan D. Hovorka H. Seay Nance David R. Cole Tommy J. Phelps Kevin G. Knauss 《Applied Geochemistry》2009
Sedimentary basins in general, and deep saline aquifers in particular, are being investigated as possible repositories for large volumes of anthropogenic CO2 that must be sequestered to mitigate global warming and related climate changes. To investigate the potential for the long-term storage of CO2 in such aquifers, 1600 t of CO2 were injected at 1500 m depth into a 24-m-thick “C” sandstone unit of the Frio Formation, a regional aquifer in the US Gulf Coast. Fluid samples obtained before CO2 injection from the injection well and an observation well 30 m updip showed a Na–Ca–Cl type brine with ∼93,000 mg/L TDS at saturation with CH4 at reservoir conditions; gas analyses showed that CH4 comprised ∼95% of dissolved gas, but CO2 was low at 0.3%. Following CO2 breakthrough, 51 h after injection, samples showed sharp drops in pH (6.5–5.7), pronounced increases in alkalinity (100–3000 mg/L as HCO3) and in Fe (30–1100 mg/L), a slug of very high DOC values, and significant shifts in the isotopic compositions of H2O, DIC, and CH4. These data, coupled with geochemical modeling, indicate corrosion of pipe and well casing as well as rapid dissolution of minerals, especially calcite and iron oxyhydroxides, both caused by lowered pH (initially ∼3.0 at subsurface conditions) of the brine in contact with supercritical CO2. 相似文献
45.
Abstract Industrial land development has become a key feature of urbanization in Greater Jakarta, one of the largest metropolitan areas in Southeast Asia. Following Suharto's market-oriented policy measures in the late 1980s, private developers have dominated the land development projects in Greater Jakarta. The article investigates the extent to which these private industrial centers have effectively reduced the domination of Jakarta in shaping the entire metropolitan structure. The analysis indicates that major suburban industrial centers have captured most of the manufacturing employment that has dispersed from Jakarta. The industrial centers have now increasingly specialized and diversified. It is likely that a polycentric metropolitan structure will emerge in the future. 相似文献
46.
Tommy G. Jensen 《Ocean Dynamics》2011,61(9):1329-1344
The sensitivity of the bifurcation of the North Equatorial Current in the Pacific to different wind products is investigated.
Variations of the bifurcation latitude with season is simulated in a purely wind-driven model and is found to be in agreement
with recent observations. The seasonal cycle is nearly independent of the wind climatology, but the annual average latitude
depends on the wind stress curl. It is also shown that in the upper ocean, the poleward shift in bifurcation latitude with
depth is realistic in our simple model. This implies that given a stratification close to the observed, it is primarily the
wind forcing that determines the location of the bifurcation and its seasonal variation. 相似文献
47.
Tom Myers 《Hydrogeology Journal》2013,21(3):655-671
Extensive phosphate mining in the Blackfoot watershed of Idaho (USA) has substantially increased the selenium (Se) concentration in the river during both snowmelt and baseflow when groundwater discharge dominates. Phosphate mines create a linkage between Se-laden shale that occurs in the Phosphoria Formation and the underlying regional Wells Formation aquifer. Using a reconnaissance-level transport model, mines in the watershed were prioritized for remediation and for comparing the results of simulations of remediation scenarios with a baseline of no remediation, for which Se concentration in the river will exceed the aquatic standard along an extensive length. An accurate simulation of recharge distribution around the watershed and simulated flux to the river is essential. Remediation of mines north of the river will substantially decrease the size of the Se plume, although significant Se will continue to discharge to the river. Similarly, remediation of three mines south of the river would decrease the Se discharge to the river but allow substantial amounts to remain stored in the groundwater north and far south of the river. A lack of calibration data is not a reason to forgo remediation, but rather ongoing data collection can be used to fine-tune plans as they are implemented. 相似文献
48.
Dirk Kossow Charlotte Krawczyk Tommy McCann Manfred Strecker Jörg F.W. Negendank 《International Journal of Earth Sciences》2000,89(3):652-664
The northern part of the Northeast German Basin contains a large number of Late Permian (Zechstein) salt pillows, whereas diapiric structures are almost completely absent. This lack of diapirs facilitated the study of early stages of salt movement in the basin. Salt pillows and related structures were investigated in terms of distribution, geometry and time of initiation of salt flow within the regional geological context. The primary Zechstein thickness in the study area was reconstructed to gain more insight into the relationship between the geometry of the salt layer and the style of the salt-related structures. In this study, no clear spatial relationship between the salt structures and basement faults has been found and the location of the salt structures in this area appears to be highly independent of the underlying structural grain. The overburden is affected by minor faulting. We propose that buckling of the overburden due to regional compression significantly contributed to the initiation of the Late Jurassic to Early Cretaceous salt structures in the basin. Reverse faulting of the Gardelegen and Haldensleben Faults is related to inversion tectonics and exerted a compression on the basin fill. During the deformation, the Late Permian salt layer acted as an efficient detachment and led to a marked decoupling of the Mesozoic overburden from the underlying pre-Zechstein rocks. 相似文献
49.
Unconsolidated, flocculent sediments that are frequently resuspended by wind action are found in many shallow-water lakes. Collecting sediment/water interface cores in such lakes for paleolimnological study may be problematic because it is difficult to determine the depth to the water/sediment interface. Accurately determining this water depth is necessary to guarantee that a piston corer does not penetrate the sediments prior to the drive and to maximize the core length. A simple instrument constructed with inexpensive, readily available components is described. This infrared floc detector (IFD) is used to sense the increased optical density of unconsolidated sediments as the detector is lowered into a lake. The IFD, in effect, yields a precise as well as an accurate measure of water depth. The depth to the water/sediment interface can be measured with an accuracy of approximately 1 cm, provided surface waters are relatively calm. 相似文献
50.