Seasat scanning multichannel microwave radiometer: results of the gulf of alaska workshop

The scanning multichannel microwave radiometer results for the Gulf of Alaska Seasat Experiment Workshop are quite encouraging, especially in view of the immaturity of the data-processing algorithms. For open ocean, rain-free cells of highest-quality surface truth wind determinations exhibit standard deviations of 3 meters per second about a bias of 1.5 meters per second. The sea-surface temperature shows a standard deviation of approximately 1.5 degrees C about a bias of 3 degrees to 5 degrees C under a variety of changing meteorological conditions.     

Seasat altimeter calibration: initial results

Preliminary analysis of radar altimeter data indicates that the instrument has met its specifications for measuring spacecraft height above the ocean surface (+/- 10 centimeters) and significant wave height (+/- 0.5 meter). There is ample evidence that the radar altimeter, having undergone development through three earth orbit missions [Skylab, Geodynamics Experimental Ocean Satellite 3 (GEOS-3), and Seasat], has reached a level of precision that now makes possible its use for important quantitative oceanographic investigations and practical applications.     

Radiometric ages of kodiak seamount and giacomini guyot, gulf of alaska: implications for circum-pacific tectonics

Kodiak Seamount and Giacomini Guyot have been dated at 22.6 +/- 1.1 and 19.9 +/- 1.0 [2sigma (standard deviation)] x 10(6) years, respectively. Concordant whole-rock and plagioclase potassium-argon dates and fission-track apatite ages demonstrate that significant quantities of excess radiogenic (40)Ar are not present in the dated samples. These seamounts are the northwesternmost edifices of the Pratt-Welker chain, which cuts obliquely across magnetic anomaly patterns in an older northeastern Pacific sea floor. The older of the two dated seamounts is in the Aleutian Trench, apparently about to be subducted. If one assumes that seamounts are generated by plate motion over a fixed hot spot in the mantle, a Pacific-plate motion of 6.6 centimeters per year during early Miocene time may be calculated.     

Deep seismic reflection results from the gulf of Mexico: part I

Deep sounding seismic reflection data show undeformed reflectors at depths down to 11 kilometers beneath the continental rise and abyssal plain and 7 kilometers in basins of the lower slope. Weak reflectors are visible beneath the salt of the Sigsbee Scarp and within salt ridges separating the lower slope basins.     

Paleoindians in beringia: evidence from arctic alaska

Excavations at the Mesa site in arctic Alaska provide evidence for a Paleoindian occupation of Beringia, the region adjacent to the Bering Strait. Eleven carbon-14 dates on hearths associated with Paleoindian projectile points place humans at the site between 9,730 and 11,660 radiocarbon years before present (years B.P.). The presence of Paleoindians in Beringia at these times challenges the notion that Paleoindian cultures arose exclusively in mid-continental North America. The age span of Paleoindians at the Mesa site overlaps with dates from two other cultural complexes in interior Alaska. A hiatus in the record of human occupation occurs between 10,300 and 11,000 years B.P. Late Glacial climatic fluctuations may have made northern Alaska temporarily unfavorable for humans and spurred their southward dispersal.     

Seasat synthetic aperture radar: ocean wave detection capabilities

A preliminary assessment has been made of the capability of the Seasat synthetic aperture radar to detect ocean waves. Comparison with surface and aircraft measurements from five passes of the satellite over the Gulf of Alaska indicates agreement to within about - 15 percent in wavelength and about +/- 25 degrees in wave direction. These results apply to waves 100 to 250 meters in length propagating in a direction predominantly across the satellite track, in sea states with significant wave height (H((1/3))) in a range of 2 to 3.5 meters.     

The archeology of alaska and the peopling of america

The proposed existence of a biotically productive tundra-steppe on the exposed Bering Land Bridge of the late Pleistocene aids conceptualization of the migrations of early Asian hunters. But clear knowledge of the human occupants of north-westernmost America before 11,000 years ago is elusive. Evidence indicates that at that time the Alaskan peoples had a culture generally based on microliths that, while obviously derived from Asia, were not sufficiently similar to the tools of the earliest widely distributed hunters of more southerly North America to support any direct and close relation between the two cultures.     

Mercury distribution in the gulf stream

Measurements of reactive mercury in ocean water in the Gulf Stream at depths from 250 to 4460 meters revealed lower and more consistent concentrations than have been reported in the western Atlantic. The mean and standard deviation of 24 values in a vertical profile were 4.1 +/- 1.0 nanograms per liter. A correlation was found between variations in mercury and silicate, suggesting a common link in their marine geochemistry.     

Radiocarbon dating of coastal peat, barrow, alaska

A buried, frozen section of peat from sea level yielded radiocarbon dates between 700 and 2600 B.C.; it suggests burial by a transgressing sea.     

Dinosaurs on the north slope, alaska: high latitude, latest cretaceous environments

Abundant skeletal remains demonstrate that lambeosaurine hadrosaurid, tyrannosaurid, and troodontid dinosaurs lived on the Alaskan North Slope during late Campanian-early Maestrichtian time (about 66 to 76 million years ago) in a deltaic environment dominated by herbaceous vegetation. The high ground terrestrial plant community was a mild- to cold-temperate forest composed of coniferous and broad leaf trees. The high paleolatitude (about 70 degrees to 85 degrees North) implies extreme seasonal variation in solar insolation, temperature, and herbivore food supply. Great distances of migration to contemporaneous evergreen floras and the presence of both juvenile and adult hadrosaurs suggest that they remained at high latitudes year-round. This challenges the hypothesis that short-term periods of darkness and temperature decrease resulting from a bolide impact caused dinosaurian extinction.     

Strain accumulation in the shumagin and yakataga seismic gaps, alaska

Strain accumulation during the 1980-85 interval has been measured by means of trilateration surveys in the Shumagin and Yakataga seismic gaps, which are the two regions identified as the most likely sites for the next great thrust earthquakes along the Alaska-Aleutian arc. No significant strain accumulation was detected in the Shumagin gap, but experience at similar subduction zones and simple models of the subduction process suggest that a measurable amount of strain should have accumulated. The most likely explanation of the observation is that subduction there is either aseismic or episodic. The strain accumulation measured in the Yakataga gap is consistent with that expected for the plate convergence rate, although the direction of maximum compression may suggest a somewhat more oblique convergence than expected.     

Thermogenic gas hydrates in the gulf of Mexico

Thermogenic gas hydrates were recovered from the upper few meters of bottom sediments in the northwestern Gulf of Mexico. The hydrates were associated with oil-stained cores at a water depth of 530 meters. The hydrates apparently occur sporadically in seismic "wipeout" zones of sediments in a region of the Gulf continental slope at least several hundred square kilometers in area.     

Glacier surge mechanism: 1982-1983 surge of variegated glacier, alaska

The hundredfold speedup in glacier motion in a surge of the kind the kind that took place in Variegated Glacier in 1982-1983 is caused by the buildup of high water pressure in the basal passageway system, which is made possible by a fundamental and pervasive change in the geometry and water-transport characteristics of this system. The behavior of the glacier in surge has many remarkable features, which can provide clues to a detailed theory of the surging process. The surge mechanism is akin to a proposed mechanism of overthrust faulting.