摘要:

The circulation of the Gulf of California has long been of scientific interest. The first hydrographic expedition there was in 1889 [Roden and Groves, 1959], followed half a century later by Sverdrup's cruise on the R/VE.W. Scripps[Suerdrup, 1941] in February and March of 1939. Since then, the Gulfs circulation has been the subject of active research [Alvarez‐Boirego, 1983]. During the 1980s, scientists at CICESE and at the Scripps Institution of Oceanography designed a cooperative effort, the Pichicuco project, to investigate some of the notable physical oceanographic features of the Gulf.The Gulf of California is a marginal sea close to 1500 km long and about 200 km wide, oriented northwest to southeast, between the peninsula of Baja California and western continental Mexico. It consists of a succession of basins that shoal progressively from about 3500 m at the mouth, where the Gulf connects with the Pacific Ocean, to just over 2000 m in the central Guaymas Basin. In contrast, the far northern Gulf is a continental shelf sea whose depth exceeds 200 m only in a few small basins. The Gulf's circulation is profoundly influenced by processes taking place at the narrows that connect Guaymas Basin to the northern Gulf between 28°N and 29°N (see Figure 1). These are a sequence of channels, each about 15 km wide, between San Lorenzo, San Esteban, and Tiburón islands, which reduce the effective cross section of the Gulf to about 2.25×106m2. The westernmost connection, close to Baja California, is the Ballenas‐Salsipuedes (hereafter Ballenas) channel, whose depth exceeds 1600 m in its central part. It is bounded partially to the north by a lateral constriction with a maximum depth of 600 m, near the northern extreme of Angel de la Guarda island, and to the east by a ridge from which rise Angel de la Guarda, San Lorenzo, and other smaller islands. This ridge extends underwater about 20 km to the southeast from San Lorenzo into Guaymas Basin, where it forms the eastern wall of San Lorenzo sill, the southern end of Ballenas channel. A narrow canyon on this sill has a maximum depth of about 430 m. The central San Esteban channel is located between San Lorenzo and San Esteban islands, and is the deepest and widest of the three. It possesses a single, rather broad sill, formed by a westward underwater extension of San Esteban island. The third channel, between San Esteban and Tiburon islands, is narrower than the first two, has a broad sill at about 300 m depth, and connects the extension of the Sonoran shelf with the deeper basin to the north. Little studied before, it now appears to play a significant role in the regional exchange of water. A fourth, narrow channel between Tiburon island and mainland Mexico is too shallow to participate strongly in the circ

ISSN:0002-8606    

DOI:10.1029/EO072i019p00209-01

年代:1991

数据来源: WILEY

摘要:

On May 1, before a standing‐room‐only House hearing, Representative Barbara Boxer (D‐Calif.) hammered hard questions at Richard Truly, administrator of the National Aeronautics and Space Administration, over the cost of the redesigned Space StationFreedom. AGU President G. Brent Dalrymple was also invited to testify about the station's cost and scientific merit as part of an expert panel before the House Government Operations subcommittee on government activities and transportation. Other witnesses included another AGU member, Louis J. Lanzerotti, chairman of the Space Studies Board of the National Research Council.The hearing, which ran three‐and‐a‐half intense hours, dealt with new estimates of Freedom's cost that are well in excess of NASA's $30 billion figure for the revised design. Charles A. Bowsher, U.S. comptroller general, testified about a new study by the General Accounting Office that estimates a $118 billion cost for the station, more than triple NASA's figure. AGU's testimony and the subcommittee's staff both projected an even higher figure—$180 billion—although they used different assumpti

ISSN:0002-8606    

DOI:10.1029/90EO00156

年代:1991

数据来源: WILEY

摘要:

Senator Al Gore (D.‐Tenn.) spotlighted the National Aeronautics and Space Administration's budget with three hearings of the Senate subcommittee on science, technology, and space, held between April 17 and 24. Gore, who chairs the Senate panel, particularly grilled NASA administrator Richard Truly and other witnesses over where space science stacks up as a budget priority. The agenda and costs for Mission to Planet Earth also provoked detailed discussion.Using the report by the Advisory Committee on the Future of the U.S. Space Program as a blueprint, Gore closely questioned Truly and the committee's chair, Norman Augustine, as to whether particular NASA program matched the committee's recommendations. In one such exchange about the new launch system, Gore charged that the Augustine panel had envisioned a $2–$4 billion cost, while NASA was now proposing an $11 billion sys

ISSN:0002-8606    

DOI:10.1029/90EO00158

年代:1991

数据来源: WILEY

摘要:

Volcanic activity beginning in March at Colima, in southwest Mexico (19.51°N, 103.61°W), has turned into a major eruption that is continuing as of May 1. The following report was provided by the Smithsonian Institution's Global Volcanism Network. All times are local (= UT −6 hours).“Lava extrusion began on March 1, following increases in seismicity, dome deformation, and thermal activity in late February. By mid‐March, the new lobe was large enough to be visible from Colima city (about 30 km from the volcano). Geologists visiting the summit on March 27 reported that the lava dome was 100 m across, 30–40 m high, and still growing. Some lava flowed into a small depression just northeast of the nearly symmetrical dome. At the time of the visit, the dome margin was 3 m from the southwest crater rim and spawned about 3 avalanches/hour. Advance of the lava was shown by blocks falling from the d

ISSN:0002-8606    

DOI:10.1029/EO072i019p00212-03

年代:1991

数据来源: WILEY

摘要:

It was with great interest that we read the article by Fraser Fanale inEos(November 20, 1990) on “Galileo's Earth‐Moon Encounter Set for December 8.” We noted the number of important observations that were planned and carried out to study the Earth‐Moon system. We are also looking forward to the large number of interesting results that will undoubtedly become available after the encounter with the asteroid Gaspra, the second Earth encounter, and, most importantly, during the Jupiter mission.However, we would like to correct an important historical statement made by the author in the introductory section of his article. The Galileo encounter with the Earth‐Moon system was not the first encounter by a spacecraft from deep space with the Earth‐Moon system. On July 2, 1990, the Giotto spacecraft encountered the Earth with closest approach at a radial distance of 3.56 Earth radii at 10:01:18 UTC. During the encounter, observations were made of the magnetic field and the energetic particle environment of the terrestrial ma

ISSN:0002-8606    

DOI:10.1029/90EO00162

年代:1991

数据来源: WILEY

摘要:

In order to better understand the physics responsible for radar imaging of oceanographic submesoscale features, the Office of the Chief of Naval Research is sponsoring the High‐Resolution Remote Sensing Program, an accelerated research initiative managed by Frank Herr and Chuck Luther at the Office of Naval Research and Richard Mied at the Naval Research Laboratory. This program includes the disciplines of remote sensing, oceanography, meteorology, and microlayer physics. The approach will be to conduct a field program of simultaneous radar and in‐situ measurements and to conduct theoretical/modeling work to understand the feature generation, variability, and imaging physics.Since the launch of SEASAT in 1978, there has been great interest in synthetic aperture radar (SAR) imaging of oceanographic features. For example, SEASAT SAR images clearly showed evidence of internal waves, current boundaries, fronts, eddies, and tidal flow over variable bathymetry (see SEASAT Special Issue I, J. Geophys. Res., 87, C5, 1982). Unfortunately, there was little or no in‐situ data associated with most of these images, so there has been little validation of models that describe the imaging mech

ISSN:0002-8606    

DOI:10.1029/EO072i019p00214-01

年代:1991

数据来源: WILEY

摘要:

The scientific and personal papers of the late C. V. Theis have been donated to the University of New Mexico by the U.S. Geological Survey and Theis's daughter, Marilyn Lewis. The collection will be housed in the Center for Southwest Research, formerly the Special Collections Department, of the UNM General Library.The university expressed a strong interest in the material because so much of it relates to the water resources of New Mexico and because of Theis's long association with the university as research associate, adjunct professor, and senior official of the Geological Survey, which was housed on the campus for many years. Although Theis was known principally for his contributions to groundwater hydraulics, his publications included papers on evaporation, terrestrial heat flow, and other subjects.

ISSN:0002-8606    

DOI:10.1029/EO072i019p00216-01

年代:1991

数据来源: WILEY

摘要:

AGU congratulates the 26 distinguished scientists who were selected by a committee of their peers to be AGU Fellows in 1991. This selection was based on the individual attaining acknowledged eminence in a branch of geophysics. The number of Fellows selected annually is limited to no more than 0.1% of the AGU membership. The new Fellows are listed below along with the citation recognizing their specific achievement.

ISSN:0002-8606    

DOI:10.1029/90EO10169

年代:1991

数据来源: WILEY