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T. J. Conomos

Publications and source records attributed to T. J. Conomos.

17 recordsLinked to original sources
USGS2003

Movement of spilled oil as predicted by estuarine nontidal drift

Information on water movement obtained from bimonthly releases of surface and seabed drifters in the San Francisco Bay and adjacent Pacific Ocean is used to understand major processes controlling dispersal of oil after a spill of 3,200 m3 of Bunker C in the bay in January 1971. River-induced nontidal estuarine circulation was the dominant factor controlling net movement of the oil spilled at the entrance of the bay system, reinforcing ebbing tidal currents and causing the seaward movement of floating oil, which followed paths taken by surface drifters released 3 weeks before the spill. In contrast, some oil formed globules which sank to the near-bottom waters, had the same relative buoyancy as seabed drifters, and moved similarly, beaching in eastern San Pablo Bay after being transported landward in the near-bottom waters. No oil or surface drifters floated into the south bay because surface waters were drifting seaward, away from the south bay. Notable seasonally modulated phenomena which must be considered in predicting surface and near-bottom oil drifts of future spills include a summer (low-river discharge period) diminution of the estuarine circulation mechanism in the north and central bayadjacent ocean region and a seasonal reversal in two-layer drift in the south bay.

California↗
USGS1985

Environmental setting of San Francisco Bay

San Francisco Bay, the largest bay on the California coast, is a broad, shallow, turbid estuary comprising two geographically and hydrologically distinct subestuaries: the northern reach lying between the connection to the Pacific Ocean at the Golden Gate and the confluence of the Sacramento-San Joaquin River system, and the southern reach (herein called South Bay) between the Golden Gate and the southern terminus of the bay. The northern reach is a partially mixed estuary dominated by seasonally varying river inflow, and the South Bay is a tidally oscillating lagoon-type estuary. Freshwater inflows, highest during winter, generate strong estuarine circulation and largely determine water residence times. They also bring large volumes of dissolved and particulate materials to the estuary. Tidal currents, generated by mixed semidiurnal and diurnal tides, mix the water column and, together with river inflow and basin geometry, determine circulation patterns. Winds, which are strongest during summer and during winter storms, exert stress on the bay's water surface, thereby creating large waves that resuspend sediment from the shallow bay bottom and, together with the tidal currents, contribute markedly to the transport of water masses throughout the shallow estuary. ?? 1985 Dr W. Junk Publishers.

Hydrobiologia↗
USGS1980

Trends in the distribution of recent foraminifera in San Francisco Bay

Much of the bathymetry of the southern part of San Francisco Bay reflects the drainage pattern of late Pleistocene streams. Holocene estuarine silt and clay cover most of the bay floor; relict eolian and deltaic sand occurs along the eastern shore; sandy patches are present in the main channel owing to higher tidal current velocities. Organic content is high along the western shore, where tidal flats are extensive, and in the slough at the mouth of Coyote Creek where wastewaters discharge. Thirty-one species of benthonic foraminifera were identified in surficial sediments of San Francisco Bay estuary; of these, 20 species were stained red by rose Bengal and are considered as live. Water depth, sediment textural characteristics, salinity, organic matter, sediment pH, and biological competition were considered as factors that might affect distribution of foraminifera. Four ecologic zones based on observed trends in the distribution and abundance of several species correlate well with some environmental factors. Four groups based on the Q-mode analysis of frequency counts of foraminiferal assemblages are reasonably similar to the four ecologic zones. These zones, showing restricted depth ranges, are: Inner Coastal Zone, where Elphidium incertum obscurum and Trochammina infiata are prominent; Outer Coastal Zone, dominated by Ammonia beccarii tepida and Elphidium incatum; Deep Bay Zone, where Elphidietla hannai, Elphidium incertum clavatum, Hopkinsina pacifica, and Bolivina spp. appear in abundance; and Deep Channel Zone, where Elphidiella hannai is most abundant. In the Inner Coastal Zone, salinity due to large fluctuations is a limiting factor for many species. Substrate textural characteristics are primary determinants of the distribution of agglutinated foraminifers. The percentage of organic matter in the sediment correlates well with the abundance of Elphidium incertum obscurum, a ubiquitous species in San Francisco Bay. Sediment pH is not critical. Biologic competition can be estimated by comparing the percentage of a species with the number of species present in the assemblage, as shown for Ammonia beccarii tepida and Elphidiella hannai.

California↗
USGS1978

Numerical simulation of dissolved silica in the San Fancisco Bay

A two-dimensional (vertical) steady-state numerical model that simulates water circulation and dissolved-silica distributions is applied to northern San Francisco Bay. The model (1) describes the strong influence of river inflow on estuarine circulation and, in turn, on the biologically modulated silica concentration, and (2) shows how rates of silica uptake relate to silica supply and mixing rates in modifying a conservative behavior. Longitudinal silica distributions influenced by biological uptake (assuming both vertically uniform and vertically decreasing uptake situations) show that uptake rates of 1 to 10 μg-at. l −1 day −1 are sufficient to depress silica concentrations at river inflows of 100–400 m 3 s −1 , respectively, and that the higher rates appear ineffective at inflows above 400 m 3 s −1 . The simulations further indicate that higher silica utilization in the null zone is not essential to depress silica concentrations strongly there. Advective water-replacement times at river inflows of 400, 200 and 100 m 3 s −1 are computed to be less than 25, 45 and 75 days, respectively, for a 120-km estuary-river system.

California↗
USGS1977

Suspended particle transport and circulation in San Francisco Bay - an overview

Differences in the relative magnitude and timing of wind stress and river inflow in the northern and southern reaches of San Francisco Bay create different sedimentary conditions. The northern reach is a partially to well mixed estuary receiving most of the total annual fresh-water input (840 m 3 sec −1 ) and suspended sediment input (4 × 10 6 metric tons) into the bay; more than 80% of the sediment is received during winter. Density-driven nontidal estuarine circulation (~5 cm sec −1 ) maintains a turbidity maximum which changes seasonally in particle concentration (40 to 80 mg litre −1 ). Strong tidal currents (≤225 cm sec −1 ) and wind-generated waves resuspend sediment from the shallow bay floor: some of the riverborne sediment deposited during winter is resuspended during summer and transported landward to the turbidity maximum. Long-term sediment data (extrapolated from bathymetrie charts) indicate that the northern reach is an effective sediment trap. In contrast, long-term sediment data suggest that the southern reach is experiencing net erosion. The southern reach receives little river inflow or riverborne suspended sediment, and the average nontidal circulation is weak (≤2 cm sec −1 ). The principal source of suspended sediment (25 mg litre −1 ) in the southern reach is the shallow bay floor (average depth 6 m).

Book chapter↗
USGS1977

Clay-mineral variability in the suspended sediments of the San Francisco Bay system, California

Semiquantitative determinations of the clay-mineral composition have been made on nearly synoptic samples of surface suspended sediments collected seasonally throughout the San Francisco Bay system. The relative amounts of chlorite + kaolinite are generally highest in the northern reach of the system, whereas illite is dominant in the southern reach. The proportion of montmorillonite is low throughout the bay. Time-series and replicate samples collected at individual stations show that the difference in clay-mineral content between reaches is real and reflects a change in the source of clay-mineral particles within the bay. The Sacramento-San Joaquin river system supplies the northern reach, whereas most clay-mineral particles come from resuspension by waves and tidal currents in the southern reach. Analyses of bottom sediments and the spatial variability in the northern reach suggest that the relationship between the abundance and sources of clay minerals may, in turn, be a function of particle size. This study demonstrates the utility of suspended clay minerals in the interpretation of sediment-dispersal patterns in estuaries.

California↗
USGS1975

Location of the non-tidal current null zone in northern San Francisco Bay

Variations in Sacramento-San Joaquin River discharge into northern San Francisco Bay causes shifts in location of the bottom density current null zone. At a river flow of 2000 m 3 /s this null zone is approximately 20 km from the seaward end of the estuary, whereas at a river flow of 100 m 3 /s it is 80 km from the seaward end; the corresponding distances of salinity penetration are approximately 40 and 90 km from the seaward end. Seaward of the null zone, during low (summer) river discharge conditions, the inward-flowing bottom density current appears typically strong (5–15 cm/s) relative to the outward-flowing river current (river discharge per unit cross-channel area) of <2 cm/s. Landward from this null zone the average river current increases with decreasing cross-channel area. This circulation implies that during the summer water within the null zone has the longest average advective replacement time relative to water seaward or landward of the null zone.

California↗
USGS1972

Drift of surface and near-bottom waters of the San Francisco Bay system, California: March 1970 through April 1971

The San Francisco Bay system is a complex estuary in which there is an interplay between natural chemical and physical processes, and changes resulting from the works of man. The bay is used for recreation, water-borne commerce, fishing, domestic and industrial waste disposal, and esthetic pleasure. Because some of these uses are competitive, it is desirable to adequately predict the impact of man's activities on this natural system. The reliability of such predictions will be strengthened by long-term observations directed toward understanding the natural processes occurring in the bay. This study is a compilation of one aspect of the U.S. Geological Survey's continuing investigations of the San Francisco Bay system.

California↗