摘要:

A highly charged atmosphere and a tacit agreement to disagree marked the first Union session at the 1985 AGU Fall Meeting,“Where Are We Now on Iridium, Anomalies, Extinctions, Impacts, Volcanism, and Periodicity?” The session brought together a remarkably large and varied group of participants who are studying topics related to mass extinctions. “The important thing is bringing all these people together, sharing … how they think,” said J. John Sepkoski, Jr., of the University of Chicago, who presented one of the session's invited papers.The controversies under discussion included the nature of the catastrophic events that may have occurred 65 million years ago to precipitate mass extinctions between the Cretaceous and Tertiary periods and whether mass extinctions have occurred at regular intervals (and if so, what those intervals are). Both the group advocating extraterrestrial impacts and that advocating episodes of unusual terrestrial volcanism seemed to agree that both kinds of catastrophes would have brought on highly acidic precipitation that could have threatened many life forms. In fact, one paleontologist called for closer examination of patterns of survival during periods of mass extinctions in order to gain clues about the nature of the events that may have brought on the extinctions. “The survivors … set limits on what could have occurred,” said William A. Clemens of the University of Calif

ISSN:0002-8606    

DOI:10.1029/EO067i001p00001-01

年代:1986

数据来源: WILEY

摘要:

With the advent of routine satellite investigations of the coastal regions where wind‐induced upwelling occurs (L.C. Breaker and C.N.K. Mooers (manuscript in preparation);Flament et al.[1985]) has come an increased appreciation for the complexity of the flows that can be produced. These are revealed especially in the surface temperature and chlorophyll fields, which often show a complex filamentary structure that is clearly related to the transport of surface water by interacting mesoscale eddies and large‐amplitude waves. In many cases these features are observed to propagate along shore in the direction of the applied wind stress, but often they are found to be quasi‐stationary. It has been speculated that this latter effect is due to the influence of bottom topography or coastline features to which these large‐scale flow features can become locked and then produce outward meandering jets. Often the features tend to drift offshore and in the direction of the applied stress, allowing new features to develop in their place (see, for example,Mooers and Robinson[1984] orNarimousa and Maxworthy[1985]). In this article we describe a series of laboratory experiments designed to study some of the questions raised by this line of reasoning and to compare experimentally determined values of certain of the observed features to values obtained from satellite and field obser

ISSN:0002-8606    

DOI:10.1029/EO067i001p00002

年代:1986

数据来源: WILEY

摘要:

In this issue of The Oceanography Report, S. Narimousa and T. Maxworthy point out the similarity between standing lee waves in their tank experiments and the quasi‐stationary wavelike wake often found in the Gulf Stream downstream from the bottom feature known as the “Charleston Bump” (see the article “Laboratory Modeling of Coastal Upwelling’). The Bump is perhaps more accurately described as a ridge‐and‐trough transverse anomaly in the continental shelf topography, but the more colorful name seems to be permanently lodged in the literature.Singer et al.[1983] detail the history of the Charleston Bump and its effects on the hydrographic structure of the Gulf Stream in the Cape Romain region, andBrooks and Bane[1983] describe the structure of the wavelike meanders that form farth

ISSN:0002-8606    

DOI:10.1029/EO067i001p00003

年代:1986

数据来源: WILEY

摘要:

In July 1984, a joint French‐U.S. team of scientists embarked on the first in a series of research cruises in the southwest Indian Ocean aboard the research/supply vesselMarion Dufresne, which is operated by Terres Australes et Antarctiques Francaises (TAAF). This monthlong cruise marked the debut of a multiyear program aimed at delineating the distribution of anthropogenic CO2in the Indian Ocean.Deep waters from the Atlantic, Pacific, and Indian oceans move to the southern ocean and mix there. The resultant relatively homogeneous water becomes the major source of the Antarctic bottom water, which spreads back out into the deep world oceans. Consequently, the chemistry of southern ocean water is a baseline for the deep world oceans. Therefore the carbonate chemistry of the southern ocean water must be learned in order to understand the biogeochemical cycle of carbon from the global point of view. Unfortunately, only a few high‐precision carbonate sampling programs have been conducted in the Indian Ocean section of the southern ocean (we know of only seven such stations south of 30°S). As a result, it is difficult to interpret variations in the carbonate chemistry or to calculate anthropogenic CO2in the Indian Ocean because we do not know the characteristic properties of the water near its origin. Furthermore, the scant data in the southern Indian Ocean were all collected in the summer, and it is uncertain whether the summer data are representative of the mainly winter‐formed deep

ISSN:0002-8606    

DOI:10.1029/EO067i001p00004-01

年代:1986

数据来源: WILEY

摘要:

Having devoured Holland's earlier book on the modern state of ocean and atmosphere chemical reservoirs,The Chemistry of the Atmosphere and Oceans(Wiley‐Interscience, New York, 1978), and having read several of the stimulating papers that derived from his work on the promised companion volume, concerned with the history of atmospheric and ocean chemistry, I eagerly anticipated publication ofThe Chemical Evolution of the Atmosphere and Oceans. It has been published, and I am not disappointed, nor will the education of any graduate student or practing professional in the earth or ocean sciences be complete without thorough study of this long‐awaited book. There is nothing else that resembles it in subject matter, comprehensiveness, and thoughtful and objective analysis of data and of old and new ideas in the field.Holland has devoted space and consideration in his book to the different episodes in atmospheric and ocean chemical history of the earth roughly in proportion to the relative duration of each episode. This, of course, means that the treatment of the relatively data‐rich Phanerozoic interval is more terse than the sections on the Precambrian. Yet Holland handles the paucity of data for the Precambrian with flair and appropriate conjecture. In fact, it is in this part of the book that his impressive intellect s

ISSN:0002-8606    

DOI:10.1029/EO067i001p00005

年代:1986

数据来源: WILEY

摘要:

This book is a welcome addition to the literature on shallow engineering seismic refraction surveying (“refraction seismics” in the European parlance). The theoretical approach given is general, while the practical applications discussed mainly concern surveys over shallow alluvial basins covering crystalline rocks.The book is divided into five major subtopics. First, the basic principles of refraction and diffraction are covered in 20 well‐written pages. Second, depth formulae are developed for multilayer media in a 22‐page chapter, and the concepts of parallelism and reciprocity of traveltime curves are introduced. Third, by far the longest chapter (173 pages) is devoted to interpretation methods. A very lucid and complete treatment is given for the author's preferred method, the ABEM method of interpretation (named for a Swedish company with these initials). The relationship between this method and other more familiar ones (such as delay times, plus‐minus, Hales' method, and the wavefront method) is clearly explained. It should be noted, however, that interpretation is limited to the analysis of first arrivals, and amplitudes are not considered. Fourth, instrumentation, field work and interpretation procedures are covered in 18 pages. The author wisely avoids a lengthy chapter of general advice, since each investigator generally will be using different equipment to solve a unique field problem. Fifth, a pleasant bonus is the 79‐page chapter on applications of refraction seismics to a variety of situations. These brief case histories involve 200‐m‐long profiles with interpretation to a depth of 20–40 km. Almost all of the examples are taken from

ISSN:0002-8606    

DOI:10.1029/EO067i001p00006

年代:1986

数据来源: WILEY

摘要:

Today we are here to award the Bowie Medal, the highest honor bestowed by the American Geophysical Union, to Henry William Menard. Bill Menard's outstanding contributions to geological sciences span 4 decades, making him one of only a handful of geologists of his generation to survive, and go on to lead, the plate tectonic revolution. Bill has given us ocean basins and rises, fracture zones and depth anomalies, crenelate ridges and pivoting subduction. His books on the history and sociology of science are well respected by experts in the field. For those of us who would aspire to some measure of significance and longevity in our own careers, it is appropriate on this occasion to catalogue some of Bill's attributes, which continue to sustain a lifetime of achievement.

ISSN:0002-8606    

DOI:10.1029/EO067i001p00008

年代:1986

数据来源: WILEY