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North Pole (north + pole)
Selected AbstractsBiogeochemistry of a gypsum-encrusted microbial ecosystemGEOBIOLOGY, Issue 3 2004D. E. CANFIELD ABSTRACT Gypsum crusts containing multicolored stratified microbial populations grow in the evaporation ponds of a commercial saltern in Eilat, Israel. These crusts contain two prominent cyanobacterial layers, a bright purple layer of anoxygenic phototrophs, and a lower black layer with active sulphate reduction. We explored the diel dynamics of oxygen and sulphide within the crust using specially constructed microelectrodes, and further explored the crust biogeochemistry by measuring rates of sulphate reduction, stable sulphur isotope composition, and oxygen exchange rates across the crust,brine interface. We explored crusts from ponds with two different salinities, and found that the crust in the highest salinity was the less active. Overall, these crusts exhibited much lower rates of oxygen production than typical organic-rich microbial mats. However, this was mainly due to much lower cell densities within the crusts. Surprisingly, on a per cell-volume basis, rates of photosynthesis were similar to organic-rich microbial mats. Due to relatively low rates of oxygen production and deep photic zones extending from 1.5 to 3 cm depth, a large percentage of the oxygen produced during the day accumulated into the crusts. Indeed, only between 16% to 34% of the O2 produced in the crust escaped, and the remainder was internally recycled, used mainly in O2 respiration. We view these crusts as potential homologs to ancient salt-encrusted microbial ecosystems, and we compared them to the 3.45 billion-year-old quartz barite deposits from North Pole, Australia, which originally precipitated gypsum. [source] The annual cycle and interannual variability of atmospheric pressure in the vicinity of the North PoleINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2003Richard I. Cullather Abstract A comparison of National Centers for Environmental Prediction,National Center for Atmospheric Research reanalysis six-hourly sea-level pressure data with former Soviet drifting station observations over the central Arctic Basin reveals high monthly correlations throughout the period 1950,91, but also a preferred winter season negative bias of about 1.4 hPa. Using the reanalysis, supplemented by Arctic Ocean Buoy Program fields and in situ observations, a generalized depiction of the annual cycle of pressure fields over the Arctic may be constructed. Above the Canada Basin,Laptev Sea side of the Arctic, the annual cycle of surface pressure is dominated by the first harmonic, which has an amplitude of about 5 hPa and maximum pressure occurring in March. Along the periphery of northern Greenland and extending to the North Pole, a weak semiannual cycle is found in surface pressure with maxima in May and November. The presence of the semiannual variation over time is highly variable. Dynamically, this progression of the annual cycle may be attributed to the transfer of atmospheric mass from Eurasia and into the Canadian Archipelago in spring and the reverse condition in autumn. Over the central Arctic Basin, springtime pressure increases result from an enhanced poleward mass transport from Eurasia. An increase of equatorward transport over the Canadian Archipelago in May and June results in central Arctic pressure decreases into summer. A less distinct temporal separation between the poleward Canadian transport and the equatorward Eurasian transport results in the weaker second pressure maximum in autumn. On interannual time-scales, atmospheric mass over the central Arctic is exchanged with the storm track centres of action in the North Atlantic and North Pacific. In particular, the large decrease in central Arctic Basin sea-level pressure during the late 1980s is due to a large transfer of atmospheric mass into the North Pacific. Copyright © 2003 Royal Meteorological Society [source] The Middle Asian Element in the Southern Rocky Mountain Flora of the western United States: a critical biogeographical reviewJOURNAL OF BIOGEOGRAPHY, Issue 5 2003William A. Weber Abstract Aim, Presentation of an hypothesis suggesting that the extraordinarily similarity of the Russian Altai and the American Southern Rocky Mountain Flora represents an Oroboreal Flora; that had to have had an essential continuity across the northern part of the world in the Tertiary period, constituting a highland and steppe component of the better-known Arcto-Tertiary Flora of eastern and far-western North America and eastern Asia. Location, North America and Middle (Altai) Asia. Methods, Summarization of the author's field and herbarium studies of whole floras over a period of over 60 years, consisting of successive specializations in vascular plants, lichens, and bryophytes. Main conclusions, (1) The modern alpine and associated marginal steppe and montane floras contain taxa of Tertiary age. (2) The floras of the southern mountains antedate those of the present-day Arctic. (3) The Middle Asiatic and the North American floras once enjoyed a contiguous existence over a broad area involving connections between North America and Asia across the North Pole by way of Greenland. Their present disjunctions are products of extinction and attrition of ranges, not of long-distance migration or dispersal mechanisms. (4) North-eastern North American disjunctions of so-called Cordilleran species (the Nunatak hypothesis) need not require explanations involving long-distance dispersal or migration, but represent relictual populations of the once widely distributed Oroboreal flora. [source] USS Annapolis:The Wardroom and The Crews MessNAVAL ENGINEERS JOURNAL, Issue 1 2003Cdr. E.D. Maissian USNR (Ret.) BACKGROUND USS Annapolis (PG-10) was the first of four gunboats (Vicksburg, Newport, Princeton) built during the transition period of the maritime world, that is -sail to steam, wood to steel. The Annapolis' original barkentine rig was of the composite type, typical for the day , steel keel and frames, steel shell plating from main deck to waterline, and wood planking with copper sheathing to the keel. Copper being resistant to barnacles, this method was used, in as much as dry docks were a scarcity in those days. Rear Admiral Phillip Hichborn, chief constructor of the Bureau of Construction and Repair, designed the hull. Rear Admiral George Wallace Melville, chief of the Bureau of Steam Engineering, designed her power plant. He was one of few survivors of the Jeannette expedition through the Bering Straits to the North Pole. Her power plant was a triple expansion reciprocating steam engine, better known as an "Up-n-Downer". Steam was supplied by two watertube boilers at 180 psi. These gunboats were pioneers in the use of watertube boilers. [source] Geomagnetism by the North Pole, anno 1769: The Magnetic Observations of Maximilian Hell during his Venus Transit ExpeditionCENTAURUS, Issue 2 2007Per Pippin Aspaas Hell's site of observation was Vardø in the remote northeastern corner of Norway. He had ambitions to present his journey and scientific results,which reached far beyond astronomy,in a grand work entitled Expeditio litteraria ad Polum arcticum. This work was never printed, although several fragments were published otherwise. Among the pieces not published were his geomagnetic observations. Hell's original manuscripts contain a considerable amount of declination readings as well as notes on instruments, practical procedures, and theoretical reflections involved in his work. In Vardø he set up a magnetic observatory, along with the astronomical one, and recorded, on an irregular schedule, the magnetic declination several times a day from April to June 1769. The records exhibit a clear signature of the diurnal variation as well as magnetic storms. Hell vigorously refuted contemporary suggestions of a connection between magnetic storms and Northern Lights. On the return voyage, a number of observations of magnetic declination along Norway were carried out, with a technique combining a gnomon with observations of the Sun's altitude with a quadrant. [source] Seasonal evolution of Titan's dark polar hood: midsummer disappearance observed by the Hubble Space TelescopeMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006Ralph D. Lorenz ABSTRACT Titan, Saturn's largest moon, has a dense organic-laden atmosphere that displays dramatic seasonal variations in composition and appearance. Here we document the evolution of the dark polar hood, first seen in 1980 by Voyager 1 around the north pole, and report quantitative measurements of the hood's disappearance from the south pole in 2002,2003 using previously unpublished observations with the Hubble Space Telescope Advanced Camera for Surveys (HST/ACS). These data support a model of the hood as a transient structure associated with downwelling during polar winter. [source] Investigating atmospheric predictability on Mars using breeding vectors in a general-circulation modelTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 603 2004C. E. Newman Abstract A breeding vectors approach is used to investigate the hypothesis that the Martian atmosphere is predictable at certain times of year, by identifying the fastest-growing modes of instability at different times in a Mars general-circulation model. Results indicate that the period from northern mid-spring until mid-autumn is remarkably predictable, with negative global growth rates for a range of conditions, in contrast to the situation on the earth. From northern late autumn to early spring growing modes do occur, peaking in northern high latitudes and near winter solstice. Reducing the size of the initial perturbations increases global growth rates in most cases, supporting the idea that instabilities which saturate nonlinearly at lower amplitudes have generally faster growth rates. In late autumn/early winter the fastest-growing modes (,bred vectors') are around the north pole, increase with dust loading, and probably grow via barotropic as well as baroclinic energy conversion. In northern late winter/early spring the bred vectors are around the north pole and are strongly baroclinic in nature. As dust loading (and with it the global circulation strength) is increased their growth rates first decrease, as the baroclinic mode is suppressed, then increase again as the fastest-growing instabilities switch to being those which dominated earlier in the year. If dust levels are very low during late northern autumn (late southern spring) then baroclinic modes are also found around the spring pole in the south, though for a slight increase in dust loading the dominant modes shift back to northern high latitudes. The bred vectors are also used as perturbations to the initial conditions for ensemble simulations. One possible application within the Mars model is as a means of identifying regions and times when dust-lifting activity (related to surface wind stress) might show significant interannual variability for a given model configuration, without the need to perform long, computationally expensive multi-year model runs with each new set-up. This is tested for a time of year when previous multi-year experiments showed significant variability in dust storm onset in the region north of Chryse. Despite the model having no feedbacks between dust lifting and atmospheric state (unlike the original multi-year run), the ensemble members still show maximum divergence in this region in terms of near-surface wind stress, suggesting both that this application deserves further testing, and that the intrinsic atmospheric variability alone may be important in producing interannual variability in this storm type. Copyright © 2004 Royal Meteorological Society [source] | |||||||||||||