Research Progress Report, No. 17

Legumes are notable for their ability to convert atmospheric dinitrogen into forms of nitrogen which are usable by plants. This is done in association with bacteria (called Rhizobium) which inhabit nodules of the plant roots. This process is called nitrogen-fixation. Legumes are important as forage and food crops due to their high protein content. Some are also useful for soil conservation purposes. There was no information on nitrogen fixation by legume crops in Alaska. This research was initiated to determine how much nitrogen different types of legumes can fix in interior Alaska

Annular variability and eddy-zonal flow interactions in a simplified atmospheric GCM. Part 1: Characterization of high and low frequency behaviour

Experiments have been performed using a simplified, Newtonian forced, global circulation model to investigate how variability of the tropospheric jet can be characterized by examining the combined fluctuations of the two leading modes of annular variability. Eddy forcing of this variability is analyzed in the phase space of the leading modes using the vertically integrated momentum budget. The nature of the annular variability and eddy forcing depends on the time scale. At low frequencies the zonal flow and baroclinic eddies are in quasi equilibrium and anomalies propagate poleward. The eddies are shown primarily to reinforce the anomalous state and are closely balanced by the linear damping, leaving slow evolution as a residual. At high frequencies the flow is strongly evolving and anomalies are initiated on the poleward side of the tropospheric jet and propagate equatorward. The eddies are shown to drive this evolution strongly: eddy location and amplitude reflect the past baroclinicity, while eddy feedback on the zonal flow may be interpreted in terms of wave breaking associated with baroclinic life cycles in lateral shear

No-till Forage Establishment in Alaska

We assessed the effectiveness of no-till forage establishment at six Alaska locations: Anchor Point, Sterling, Point MacKenzie, Palmer, Delta Junction, and Fairbanks. Directly seeding grass into established grass stands generally did not improve forage yields or quality. Seeding rate had little effect on establishment of newly seeded forages in no-till. Grass yields were depressed when companion crop yields were high, and they typically did not recover in subsequent years. Red clover established well, producing high yields of good quality forage under no-till at Point MacKenzie, but established poorly at Anchor Point and Delta Junction. These results indicated that no-till seeding of most forage crops into declining grass stands is not likely to be successful in Alaska with current available technology

MP 2012-02

Final report to BP.The Prudhoe Bay oil fields, Alaska were discovered in 1968, and commercial production commenced in 1977 with the completion of the Trans-Alaska Pipeline. Oil production has been declining since 1989, although additional exploratory drilling continues. Support facilities for oil production are built on permafrost soils that surface-thaw in summer to form extensive wetlands composed of moist meadows, sedge marshes, moist sedge-dwarf shrub tundra, grass marshes, small ponds and lakes (Walker and Acevedo 1987). To prevent thawing and subsidence of subsurface, ice-rich soils, gravel pads, 2m (6 ft) or more thickness have been built to support drilling sites as well as roads, airstrips and building pads (Kidd et al. 2006). As well sites are decommissioned, the gravel is wholly or partially removed resulting in the need for site rehabilitation and/or restoration to support wetland plants and, in some instances, enhance wildlife habitat (McKendrick 1991, Jorgenson and Joyce 1994, Kidd et al. 2004, 2006). Since the 1970s, methods to revegetate arctic wetlands have included a variety of planting techniques, seed treatments, seeding with native and non-native species (mostly grasses), and fertilizer applications (Chapin and Chapin 1980; Bishop and Chapin 1989, Jorgenson 1988, Kidd and Rossow 1998, Kidd et al. 2004, 2006, Maslen and Kershaw 1989, McKendrick 1987, 1991, 2000, McKendrick et al. 1980, McKendrick and Mitchell 1978, Mitchell et al. 1974). Treatments also have included sprigging and plug transplantation (Kidd et al. 2004, 2006), surface manipulation (Streever et al. 2003), as well as natural re-colonization (Ebersole 1987, Schwarzenbach 1996). These methods have been partially successful. The gravelly soils often are dry, nutrient-poor, and have a higher pH and lower organic matter content than surrounding soils, so natural recolonization does not occur readily (Bishop and Chapin 1989, Jorgenson and Joyce 1994). Methods such as sprigging and plug transplanting are slow, labor intensive and expensive compared to direct seeding. Fertilization, especially with phosphorus, is recommended for long-term survival of plants grown on gravelly sandy soils (BP Exploration and McKendrick 2004). Two common species in the arctic coastal wetlands are water sedge, Carex aquatilis Wahlenb. and cotton sedge, Eriophorum angustifolium Honck. Carex aquatilis in particular forms large populations that spread vegetatively by rhizomes and often dominate these wetland environments (Shaver and Billings 1975). Despite their abundance, these species have not been considered for revegetation because of poor seed germination and inadequate information on seed development and viability (Dr. William Streever, BP Alaska, pers. comm.). Both Carex and Eriophorum in arctic environments produce abundant seeds, but seed viability and germination often is low and highly variable among years and locations (Archibold 1984, Billings and Mooney 1968, Ebersole 1989, Gartner et al. 1983). Germination recommendations for both species vary by location and have included an array of pretreatments such as light, alternating temperatures, cold stratification, scarification, and high and low temperature dry storage (Amen 1966, Billings and Mooney 1960, Bliss 1958, Hunt and Moore 2003, Johnson et al. 1965, Phillips 1954 and Steinfeld 2001). The purpose of this project was to explore methods of seed germination of Carex aquatilis and Eriophorum angustifolium, to learn the conditions for germination and dormancy control mechanisms, and identify seed treatments that might enhance germination for eventual use in direct-seeding or plug production for arctic wetland revegetation

Progression from ocular hypertension to visual field loss in the English hospital eye service

Background There are more than one million National Health Service visits in England and Wales each year for patients with glaucoma or ocular hypertension (OHT). With the ageing population and an increase in optometric testing, the economic burden of glaucoma-related visits is predicted to increase. We examined the conversion rates of OHT to primary open-angle glaucoma (POAG) in England and assessed factors associated with risk of conversion. Methods Electronic medical records of 45 309 patients from five regionally different glaucoma clinics in England were retrospectively examined. Conversion to POAG from OHT was defined by deterioration in visual field (two consecutive tests classified as stage 1 or worse as per the glaucoma staging system 2). Cox proportional hazards models were used to examine factors (age, sex, treatment status and baseline intraocular pressure (IOP)) associated with conversion. Results The cumulative risk of conversion to POAG was 17.5% (95% CI 15.4% to 19.6%) at 5 years. Older age (HR 1.35 per decade, 95% CI 1.22 to 1.50, p<0.001) was associated with a higher risk of conversion. IOP-lowering therapy (HR 0.45, 95% CI 0.35 to 0.57, p<0.001) was associated with a lower risk of conversion. Predicted 5-year conversion rates for treated and untreated groups were 14.0% and 26.9%, respectively. Conclusion Less than one-fifth of OHT patients managed in glaucoma clinics in the UK converted to POAG over a 5-year period, suggesting many patients may require less intensive follow-up. Our study provides real-world evidence for the efficacy of current management (including IOP-lowering treatment) at reducing risk of conversion

MP 2009-09

As the price of traditional fossil fuels escalates, there is increasing interest in using renewable resources, such as biomass, to meet our energy needs. Biomass resources are of particular interest to communities in interior Alaska, where they are abundant (Fresco, 2006). Biomass has the potential to partially replace heating oil, in addition to being a possible source for electric power generation (Crimp and Adamian, 2000; Nicholls and Crimp, 2002; Fresco, 2006). The communities of Tanana and Dot Lake have already installed small Garn boilers to provide space heating for homes and businesses (Alaska Energy Authority, 2009). A village-sized combined heat and power (CHP) demonstration project has been proposed in North Pole. In addition, several Fairbanks area organizations are interested in using biomass as a fuel source. For example, the Fairbanks North Star Borough is interested in using biomass to supplement coal in a proposed coal-to-liquids project, the Cold Climate Housing Research Center is planning to test a small biomass fired CHP unit, and the University of Alaska is planning an upgrade to its existing coal-fired power plant that could permit co-firing with biomass fuels. The challenge for all of these projects is in ensuring that biomass can be harvested on both an economically and ecologically sustainable basis

The impact of the state of the troposphere on the response to stratospheric heating in a simplified GCM

Previous studies have made use of simplified general circulation models (sGCMs) to investigate the atmospheric response to various forcings. In particular, several studies have investigated the tropospheric response to changes in stratospheric temperature. This is potentially relevant for many climate forcings. Here the impact of changing the tropospheric climatology on the modeled response to perturbations in stratospheric temperature is investigated by the introduction of topography into the model and altering the tropospheric jet structure. The results highlight the need for very long integrations so as to determine accurately the magnitude of response. It is found that introducing topography into the model and thus removing the zonally symmetric nature of the model’s boundary conditions reduces the magnitude of response to stratospheric heating. However, this reduction is of comparable size to the variability in the magnitude of response between different ensemble members of the same 5000-day experiment. Investigations into the impact of varying tropospheric jet structure reveal a trend with lower-latitude/narrower jets having a much larger magnitude response to stratospheric heating than higher-latitude/wider jets. The jet structures that respond more strongly to stratospheric heating also exhibit longer time scale variability in their control run simulations, consistent with the idea that a feedback between the eddies and the mean flow is both responsible for the persistence of the control run variability and important in producing the tropospheric response to stratospheric temperature perturbations

Direct transition to high-dimensional chaos through a global bifurcation

In the present work we report on a genuine route by which a high-dimensional (with d>4) chaotic attractor is created directly, i.e., without a low-dimensional chaotic attractor as an intermediate step. The high-dimensional chaotic set is created in a heteroclinic global bifurcation that yields an infinite number of unstable tori.The mechanism is illustrated using a system constructed by coupling three Lorenz oscillators. So, the route presented here can be considered a prototype for high-dimensional chaotic behavior just as the Lorenz model is for low-dimensional chaos.Comment: 7 page

Frontal Structure of the Antarctic Circumpolar Current in the South Indian Ocean

Using recently published atlas data [Olbers et al., 1992] and the Fine Resolution Antarctic Model (FRAM) [Webb et al., 1991], an investigation has been conducted into the structure of the frontal jets centered around the region of the islands of Crozet (46°27'S, 52°0'E) and Kerguelen (48°15'S, 69°10'E) in the south Indian Ocean. Geostrophic current velocities and transports were calculated from the temperature and salinity fields available from the atlas and compared with results from FRAM and previous studies. We have identified the Agulhas Return Front (ARF) and the Subtropical Front (STF), as well as the following fronts of the Antarctic Circumpolar Current (ACC): the Subantarctic Front (SAP), the Polar Front (PF), and the Southern ACC Front (SACCF), from temperature and salinity characteristics and from geostrophic currents. This analysis of model and atlas data indicates that the jets associated with the ARF, STF, and SAF are topograpliically steered into a unique frontal system north of the islands, having some of the largest temperature and salinity gradients anywhere in the world ocean. The frontal jet associated with the ARF is detectable up to 75°E and has associated with it several northward branching jets. The PF bifurcates in the region of the Ob'Lena (Conrad) seamount; subsurface and surface expressions are identified, separated by as much as 8° of latitude immediately west of the Kerguelen Plateau. The surface expression, carrying the bulk of the transport (~65 Sv), is steered through the col in the Kerguelen Plateau at 56°S, 6° south of the latitude normally associated with the PF at this meridian. On crossing the plateau it rejoins the subsurface expression. In the south, passing eastward along the margin of the Antarctic continent and through the Princess Elizabeth Trough, a frontal jet is identified transporting up to 35 Sv, believed to be the SACCF [Orsi et al., 1995], placing the southern extent of the ACC in the region at 67°S. Copyright 1996 by the American Geophysical Union