We have measured ³He/⁴He ratios and He and Ne concentrations on a suite of 24 basalt glasses from the neovolcanic zone of the Juan de Fuca Ridge (JdFR) from 44.6°N near the Blanco Transform up to 48.0°N on the Endeavour Segment. The helium isotope ratios exhibit a clear geographic variation,...
The Vizcaino block is an anomalously shallow region of the western U.S continental margin located southwest of the Mendocino triple junction. It originated as part of the accretionary prism of the North America plate and was transferred to the Pacific plate in the Miocene as the Pacific-North America plate boundary...
Models of magnetic and gravity anomalies along two E-W transects offshore central Oregon, one of which is coincident with a detailed velocity model, provide quantitative limits on the structure of the subducting oceanic crust and the crystalline backstop. The models indicate that the backstop-forming western edge of the Siletz terrane,...
Analytical and numerical models are used to study the effects of a meridional ridge on the propagation of barotropic Rossby waves produced by distant wind stress forcing. The analytical model illustrates the qualitative aspects of the problem by solving a simplified form of the potential vorticity equation. The analytical results...
The sensitivity of the tropics to climate change, particularly the amplitude of glacial‐to‐interglacial changes in sea surface temperature (SST), is one of the great controversies in paleoclimatology. Here we reassess faunal estimates of ice age SSTs, focusing on the problem of no‐analog planktonic foraminiferal assemblages in the equatorial oceans that...
Benthic foraminiferal δ¹³C data from site 502 in the Caribbean Sea (sill depth 1800 m) indicate that throughout the past 2.6 m.y., glacial δ¹³C values in the middepth Atlantic were higher during glaciations than interglaciations. This is interpreted as indicating a greater proportion of Upper North Atlantic Deep Water (UNADW)...
We evaluate the reliability of statistical estimates of sea surface temperature (SST) derived from planktonic foraminiferal faunas using the modern analog method and the Imbrie‐Kipp method. Global core top faunas provide a calibration data set, while modern sediment trap faunas are used for validation. Linear regression of core top predicted...
Relative humidity (RH) measurements acquired in orographic wave cloud and cirrus environments are used to investigate the temperature‐dependent RH required to nucleate ice crystals in the upper troposphere, RHnuc(T). High ice‐supersaturations in clear air—conducive to the maintenance of aircraft contrails yet below RHnuc and therefore insufficient for cirrus formation—are not...
A temperature spectrum if heterogeneous freezing nuclei concentrations in continental air in the upper troposphere was determined based on airborne measurements. Numerical model simulations incorporating ice formation by heterogeneous and homogeneous freezing of deliquesced soluble aerosol particles were performed to investigate the effect of the heterogeneous freezing nuclei were predicted...
Meanders of the shelf break front in the Mid-Atlantic Bight (MAB) during April and May of 1997 were associated with chlorophyll enhancement along a hydrographic and a topographic feature. The hydrographic feature was the surface outcrop of the front, which ranged from ~10 to >100 km seaward of the shelf...
We use the position fixes and temperature readings from 56 Tristar-II mixed-layer drifters, in conjunction with advanced very high resolution radiometer images, to provide a description of the mesoscale variability of the flows associated with cold-water filaments in the California Current system off northern California in July 1988. We find...
Satellite infrared imagery and coastal meteorological data for March 1984 through February 1985 are used to estimate the net annual surface heat flux for the northern Gulf of California. The average annual surface heat flux for the area north of Guaymas and Santa Rosalia is estimated to be +74 W...
Satellite-derived pigment concentrations from the west coast time series (WCTS) are averaged into monthly mean fields over the California Current system (CCS) for the period July 1979 to June 1986. Errors caused by the scattering algorithm used in the WCTS are reduced by an empirical correction function, although winter values...
A succession of basaltic lavas, volcaniclastic sediments, and lignite beds in the Holmatindur region of eastern Iceland provides the means for tying magnetic reversal stratigraphy and a record of major North Atlantic cooling to a precise radiometric timescale. A prominent part of the section is the Holmatindur classic bed, which...
Evidence for secondary circulation associated with a shelfbreak front is obtained from a high‐resolution, cross‐shelf section of hydrographic, optical and velocity fields. Convergence in the bottom boundary layer on the inshore side of the front and subsequent upwelling into the interior is evident by a mid‐water region of suspended bottom...
Previous simulations of the Martian atmosphere have shown how topography acts to confine the low-level Hadley cell flow into intense jets on the eastern flanks of Tharsis and Syrtis Major. We now conduct detailed studies of these jets using the NASA Ames Mars general circulation model (MGCM). The structure of...
An atmospheric transport model has been used to explore the relationship between source emissions and ambient air quality for individual particle phase organic compounds present in primary aerosol source emissions. An inventory of fine particulate organic compound emissions was assembled for the Los Angeles area in the year 1982. Sources...
Satellite data from the Geosat altimeter and the Advanced Very High Resolution Radiometer (AVHRR) are used to show the large-scale structure of the surface circulation of the California Current System in summer. These data show the connection between an equatorward jet and temperature front off Oregon that lies within 100...
Data from Geosat and TOPEX altimeters are used to infer the structure of the Peru-Chile Countercurrent, a jet that flows from at least as far north as 10ºS (historical data suggests 7ºS) to 35º–40ºS, maintaining its position between approximately 100–300 km offshore. Although the annual mean current cannot be determined...
In July 1993 we collected hydrographic data and information on chlorophyll distribution on the continental shelf north of Cape Hatteras and across the shelf break at Cape Hatteras. The data show that a warm, transparent mixed layer lies over much colder, euphotic, chlorophyll-rich bottom water on the shelf. This layer...