Showing papers by "University of New Hampshire published in 2002"

Flavonoid antioxidants: chemistry, metabolism and structure-activity relationships.

Abstract: Flavonoids are a class of secondary plant phenolics with significant antioxidant and chelating properties. In the human diet, they are most concentrated in fruits, vegetables, wines, teas and cocoa. Their cardioprotective effects stem from the ability to inhibit lipid peroxidation, chelate redox-active metals, and attenuate other processes involving reactive oxygen species. Flavonoids occur in foods primarily as glycosides and polymers that are degraded to variable extents in the digestive tract. Although metabolism of these compounds remains elusive, enteric absorption occurs sufficiently to reduce plasma indices of oxidant status. The propensity of a flavonoid to inhibit free-radical mediated events is governed by its chemical structure. Since these compounds are based on the flavan nucleus, the number, positions, and types of substitutions influence radical scavenging and chelating activity. The diversity and multiple mechanisms of flavonoid action, together with the numerous methods of initiation, detection and measurement of oxidative processes in vitro and in vivo offer plausible explanations for existing discrepancies in structure-activity relationships. Despite some inconsistent lines of evidence, several structure-activity relationships are well established in vitro. Multiple hydroxyl groups confer upon the molecule substantial antioxidant, chelating and prooxidant activity. Methoxy groups introduce unfavorable steric effects and increase lipophilicity and membrane partitioning. A double bond and carbonyl function in the heterocycle or polymerization of the nuclear structure increases activity by affording a more stable flavonoid radical through conjugation and electron delocalization. Further investigation of the metabolism of these phytochemicals is justified to extend structure-activity relationships (SAR) to preventive and therapeutic nutritional strategies.

Methodological Nationalism and Beyond: Nation-State Building, Migration and the Social Sciences

Abstract: Methodological nationalism is understood as the assumption that the nation/state/society is the natural social and political form of the modern world. We distinguish three modes of methodological nationalism that have characterized main- stream social science, and then show how these have influenced research on migra- tion. We discover parallels between nationalist thinking and the conceptualization of migration in postwar social sciences. In a historical tour d'horizon, we show that this mainstream concept has developed in close interaction with nation-state building pro- cesses in the West and the role that immigration and integration policies have played within them. The shift towards a study of 'transnational communities' - the last phase in this process - was more a consequence of an epistemic move away from methodo- logical nationalism than of the appearance of new objects of observation. The article concludes by recommending new concepts for analysis that, on the one hand, are not coloured by methodological nationalism and, on the other hand, go beyond the fluidism of much contemporary social theory. After the first flurry of confusion about the nature and extent of contemporary pro- cesses of globalization, social scientists moved beyond rhetorical generalities about the decline of the nation-state and began to examine the ways in which nation-states are currently being reconfigured rather than demolished. That nation-states and nationalism are compatible with globalization was made all too obvious. We wit- nessed the flouring of nationalism and the restructuring of a whole range of new states in Eastern Europe along national lines in the midst of growing global interconnec- tions. The concomitance of these processes provides us with an intellectual opening to think about the limitations of our conceptual apparatus. It has become easier to under- stand that it is because we have come to take for granted a world divided into discrete and autonomous nation-states that we see nation-state building and global inter- connections as contradictory. The next step is to analyse how the concept of the nation-state has and still does influence past and current thinking in the social sciences, including our thinking about transnational migration. It is our aim in this article to move in this direction by exploring the intellectual potential of two hypotheses. We demonstrate that nation-state building processes have fundamentally shaped the ways immigration has been perceived and received. These perceptions have in turn influenced, though not completely determined, social science

Increasing river discharge to the Arctic Ocean

Abstract: Synthesis of river-monitoring data reveals that the average annual discharge of fresh water from the six largest Eurasian rivers to the Arctic Ocean increased by 7% from 1936 to 1999. The average annual rate of increase was 2.0 ± 0.7 cubic kilometers per year. Consequently, average annual discharge from the six rivers is now about 128 cubic kilometers per year greater than it was when routine measurements of discharge began. Discharge was correlated with changes in both the North Atlantic Oscillation and global mean surface air temperature. The observed large-scale change in freshwater flux has potentially important implications for ocean circulation and climate.

Soil Warming and Carbon-Cycle Feedbacks to the Climate System

Abstract: In a decade-long soil warming experiment in a mid-latitude hardwood forest, we documented changes in soil carbon and nitrogen cycling in order to investigate the consequences of these changes for the climate system. Here we show that whereas soil warming accelerates soil organic matter decay and carbon dioxide fluxes to the atmosphere, this response is small and short-lived for a mid-latitude forest, because of the limited size of the labile soil carbon pool. We also show that warming increases the availability of mineral nitrogen to plants. Because plant growth in many mid-latitude forests is nitrogen-limited, warming has the potential to indirectly stimulate enough carbon storage in plants to at least compensate for the carbon losses from soils. Our results challenge assumptions made in some climate models that lead to projections of large long-term releases of soil carbon in response to warming of forest ecosystems.

The magnetic nature of solar flares

Abstract: The main challenge for the theory of solar eruptions has been to understand two basic aspects of large flares. These are the cause of the flare itself and the nature of the morphological features which form during its evolution. Such features include separating ribbons of H $\alpha$ emission joined by a rising arcade of soft x-ray loops, with hard x-ray emission at their summits and at their feet. Two major advances in our understanding of the theory of solar flares have recently occurred. The first is the realisation that a magnetohydrodynamic (MHD) catastrophe is probably responsible for the basic eruption and the second is that the eruption is likely to drive a reconnection process in the field lines stretched out by the eruption. The reconnection is responsible for the ribbons and the set of rising soft x-ray loops, and such a process is well supported by numerical experiments and detailed observations from the Japanese satellite Yohkoh. Magnetic energy conversion by reconnection in two dimensions is relatively well understood, but in three dimensions we are only starting to understand the complexity of the magnetic topology and the MHD dynamics which are involved. How the dynamics lead to particle acceleration is even less well understood. Particle acceleration in flares may in principle occur in a variety of ways, such as stochastic acceleration by MHD turbulence, acceleration by direct electric fields at the reconnection site, or diffusive shock acceleration at the different kinds of MHD shock waves that are produced during the flare. However, which of these processes is most important for producing the energetic particles that strike the solar surface remains a mystery.

High-resolution fields of global runoff combining observed river discharge and simulated water balances

Abstract: [1] This paper demonstrates the potential of combining observed river discharge information with climate-driven water balance model (WBM) outputs to develop composite runoff fields. Such combined runoff fields simultaneously reflect the numerical accuracy of the discharge measurements and preserve the spatial and temporal distribution of simulated runoff. Selected gauging stations from the World Meteorological Organization Global Runoff Data Centre (GRDC) data archive were geographically coregistered to a gridded simulated topological network at 30′ (longitude × latitude) spatial resolution (STN–30p). Interstation regions between gauging stations along the STN–30p network were identified, and annual interstation runoff was calculated. The annual interstation runoff was compared with outputs from WBM calculations, which were performed using long-term mean monthly climate forcings (air temperature and precipitation). The simulated runoff for each cell was multiplied by the ratio of observed to simulated runoff of the corresponding interstation region from the GRDC data set to create spatially distributed runoff fields at 30′ resolution. The resulting composite runoff fields (UNH/GRDC Composite Runoff Fields V1.0) are released to the scientific community along with intermediate data sets, such as station attributes and long-term monthly regimes of the selected gauging stations, the simulated topological network (STN–30p), STN–30p derived attributes for the selected stations, and gridded fields of the interstation regions along STN–30p. These data sets represent high-resolution fields that are of value to a broad range of water-related research, including terrestrial modeling, climate-atmosphere interactions, and global water resource assessments.

Charge states of energetic (≈0.5 MeV/n) ions in corotating interaction regions at 1 AU and implications on source populations

Abstract: [1] The ionic charge states of He, C, O, Ne, Mg and Fe at ≈0.5 MeV/n have been obtained in several corotating interaction regions (CIRs) in 1999 and 2000 with the Solar Energetic Particle Ionic Charge Analyzer (SEPICA) on the Advanced Composition Explorer (ACE). A large fraction (on average 25%) of He+ is found relative to He2+, indicating a substantial contribution of interstellar pickup ions. The mean charge states of the heavy ions are consistent with those in CME related energetic particle events and in solar wind. A rather low upper limit of <1% is found for singly charged ions for C, O and Mg, while Ne shows a small, but noticeable, fraction (4.7%) of Ne+. These observations are consistent with a contribution from interstellar pickup ions, but seem to eliminate inner source pickup ions as a substantial source for CIRs at and near 1 AU.

Directing research to reduce the impacts of nonindigenous species

Abstract: Management of nonindigenous species is a crucial aspect of maintaining native biodiversity and normal ecosystem functions. We attempt to guide researchers in developing projects that will be of use to con- servation practitioners, tangibly improving applied conservation measures. We advocate a directed approach for conservation research to aid in prioritizing nonindigenous species for intervention by resource managers. This approach includes outlining what needs to be known to make such relative judgments about the impacts of nonindigenous species and the most promising methods by which to obtain such information. We also ad- dress active measures that should be taken once priorities have been set, highlighting the roles of risk assess- ment and research in improving control efforts. Ultimately, a better match between research and practical conservation needs should result in more effective reduction of the effects of nonindigenous species on native species.

On fusion categories

Abstract: Using a variety of methods developed in the literature (in particular, the theory of weak Hopf algebras), we prove a number of general results about fusion categories in characteristic zero. We show that the global dimension of a fusion category is always positive, and that the S-matrix of any modular category (not necessarily hermitian) is unitary. We also show that the category of module functors between two module categories over a fusion category is semisimple, and that fusion categories and tensor functors between them are undeformable (generalized Ocneanu rigidity). In particular the number of such categories (functors) realizing a given fusion datum is finite. Finally, we develop the theory of Frobenius-Perron dimensions in an arbitrary fusion category and classify categories of prime dimension.

Impact of non‐indigenous species on natives enhanced by anthropogenic alteration of selection regimes

Abstract: Changes in environmental conditions often reverse outcomes of competitive interactions among species. Such context dependency implies that the speed, persistence, and ubiquity of anthropogenic habitat alterations may suddenly put even previously well-adapted native species at a competitive disadvantage with non-native species. That is, anthropogenic disturbance may so drastically alter environments that a native species finds itself in an environment that in key ways is just as novel as it is to a non-indigenous species. Extreme disturbances may thereby erase a native species' prior advantage of local environmental adaptation accrued during its long-term incumbency over evolutionary time. I document examples from two areas of dramatic human alteration of selection regimes - eutrophication and the selective removal of top predators - that support this mechanism. Additionally, I highlight ways in which this mechanism is experimentally testable. Alteration of selection regimes may prove to be a powerful explanation for the enhanced success and impact of biological invasions in our globally disturbed biosphere.

Generation of the fast solar wind: A review with emphasis on the resonant cyclotron interaction

Abstract: [1] In situ measurements of the solar wind and remote observations of coronal holes have strongly implicated the resonant interaction with ion cyclotron waves as the responsible mechanism for heating and accelerating coronal hole ions to generate the fast solar wind. We review the current observational and theoretical knowledge of this mechanism and the progress that has been made in modeling the solar wind properties that result from this interaction. We begin by examining the observational and theoretical motivations for the continued study of this mechanism, including a brief historical review of these ideas. We then discuss the interplay of the resonance condition and the wave dispersion relation, which determines which ions can exchange energy with the waves. The physical basis for the interaction is then described, and we derive simple expressions for the ion response to the resonant wave dissipation. The complicated topic of oblique propagation is dealt with next, including how the resonant interaction operates for obliquely propagating waves. The plasma response to the resonant dissipation is often approximated by treating the ion populations as fluids, and we examine the solar wind models which incorporate various versions of this interaction. We then present a sample model that illustrates many of the properties and shortcomings of the current fluid results in this area. However, the resonant interaction is most accurately treated with a kinetic description of the ions and the recent attempts to construct kinetic models are explored. We close with a discussion of the many observational and theoretical gaps in our understanding that remain, including a presentation of alternative mechanisms and some speculations on future developments in this field.

Spiritual Development Across the Adult Life Course: Findings from a Longitudinal Study

Abstract: Longitudinal data spanning early (30s) and older (late 60s/mid-70s) adulthood were used to study spiritual development across the adult life course in a sample of men and women belonging to a younger (born 1928/29) and an older (born 1920/21) age cohort. All participants, irrespective of gender and cohort, increased significantly in spirituality between late middle (mid-50s/early 60s) and older adulthood. Members of the younger cohort increased in spirituality throughout the adult life cycle. In the second half of adulthood, women increased more rapidly in spirituality than men. Spiritual involvement in older age was predicted by religious involvement and personality characteristics in early adulthood and subsequent experiences of negative life events.

Emergent leaders as managers of group emotion

Abstract: This article proposes a new role for emergent group leaders, that of the manager of group emotions. This description of leadership suggests that individual group members take leadership by providing certainty and direction during times of ambiguity. They are able to assume a leadership role by making an interpretation of the emotional response that best serves the group's needs, and then modeling that response. By modeling a particular emotional response, the leader resolves ambiguity and catalyzes the group to act. Simultaneously, they are able to increase group solidarity by creating shared emotion within the group and communal action. The idea of leadership as group emotional management is not tied to one specific individual, but rather, allows leadership to be enacted by different group members at different times. Leader emergence and leader success would be subject to several conditions, such as the emergent leader's degree of empathy, group norms of emotional expression, and ambiguous feedback regarding the group's performance. Qualitative analysis of group observation reveals several examples of group emotional management that are used to develop the concept. Implications for theory and practice are discussed.

Plant biomass and production and CO2 exchange in an ombrotrophic bog

Abstract: Summary 1 Above-ground biomass was measured at bog hummock, bog hollow and poor-fen sites in Mer Bleue, a large, raised ombrotrophic bog near Ottawa, Ont., Canada. The average above-ground biomass was 587 g m ‐2 in the bog, composed mainly of shrubs and Sphagnum capitula. In the poor fen, the average biomass was 317 g m ‐2 , comprising mainly sedges and herbs and Sphagnum capitula. Vascular plant above-ground biomass was greater where the water table was lower, with a similar but weaker relationship for Sphagnum capitula and vascular leaf biomass. 2 Below-ground biomass averaged 2400 g m ‐2 at the bog hummock site, of which 300 g m ‐2 was fine roots (< 2 mm diameter), compared with 1400 g m ‐2 in hollows (fine roots 450 g m ‐2 ) and 1200 g m ‐2 at the poor-fen site. 3 Net Ecosystem Exchange (NEE) of CO 2 was measured in chambers and used to derive ecosystem respiration and photosynthesis. Under high light flux (PAR of 1500 μ mol m ‐2 s ‐1 ), NEE ranged across sites from 0.08 to 0.22 mg m ‐2 s ‐1 (a positive value indicates ecosystem uptake) in the spring and summer, but fell to ‐0.01 to ‐0.13 mg m ‐2 s ‐1 (i.e. a release of CO 2 ) during a late-summer dry period. 4 There was a general agreement between a combination of literature estimates of photosynthetic capacity for shrubs and mosses and measured biomass and summertime CO 2 uptake determined by the eddy covariance technique within a bog footprint (0.40 and 0.35‐0.40 mg m ‐2 s ‐1 , respectively). 5 Gross photosynthesis was estimated to be about 530 g m ‐2 year ‐1 , total respiration 460 g m ‐2 year ‐1 , and export of DOC, DIC and CH 4 10 g m ‐2 year ‐1 , leaving an annual C sequestration rate of 60 g m ‐2 year ‐1 . Root production and decomposition are important parts of the C budget of the bog. Root C production was estimated to be 161‐176 g m ‐2 year ‐1 , resulting in fractional turnover rates of 0.2 and 1 year ‐1 for total and fine roots,

Emotional intelligence as the basis of leadership emergence in self-managing teams ☆

Abstract: We present and test a theory on leader emergence in self-managing teams that highlights the emotional and cognitive skills underlying selection as an informal team leader. Existing theory and research reveals that informal leaders are selected because they display constructive task and team management behavior. We contribute to existing theory in two ways. First, by proposing that specific cognitive processes and skills precede the appropriate enactment of those behaviors by facilitating an accurate analysis of the task situation. Second, by proposing that empathy, an aspect of emotional intelligence, precedes and enables those cognitive processes and skills by providing an accurate understanding of team and member emotions and needs. We test our theory in a longitudinal study of 382 team members comprising 48 self-managing teams. Our theory is partially supported and implications are discussed.

Motion of the dipolarization front during a flow burst event observed by Cluster

Abstract: [1] In this paper we study a flow burst event which took place during enhanced geomagnetic activity on July 22, 2001, when Cluster was located in the postmidnight magnetotail. The flow burst was associated with a clear dipolarization ahead of the high-speed part of the predominantly Earthward directed flow. Based on the analysis of the four spacecraft data, we found that a ∼2000 km thick dipolarization front moves Earthward and dawnward with a speed of ∼77 km/s. The plasma before this front is deflected, consistent with the plasma ahead of a localized plasma bubble centered at midnight side being pushed aside by the moving obstacle. The main body of the high-speed flow is directed mainly parallel to the dipolarization front. These observations indicate that the evolution of the dipolarization front across the tail is directly coupled with the fast flow.

The origin, composition and rates of organic nitrogen deposition: A missing piece of the nitrogen cycle?

Abstract: Organic forms of nitrogen are widespread in the atmosphere and their deposition may constitute a substantive input of atmospheric N to terrestrial and aquatic ecosystems. Recent studies have expanded the pool of available measurements and our awareness of their potential significance. Here, we use these measurements to provide a coherent picture of the processes that produce both oxidized and reduced forms of organic nitrogen in the atmosphere, examine how those processes are linked to human activity and how they may contribute to the N load from the atmosphere to ecosystems. We summarize and synthesize data from 41 measurements of the concentrations and fluxes of atmospheric organic nitrogen (AON). In addition, we examine the contribution of reduced organic nitrogen compounds such as amino acids, bacterial/particulate N, and oxidized compounds such as organic nitrates to deposition fluxes of AON. The percentage contribution of organic N to total N loading varies from site to site and with measurement methodology but is consistently around a third of the total N load with a median value of 30% (Standard Deviation of 16%). There are no indications that AON is a proportionally greater contributor to N deposition in unpolluted environments and there are not strong correlations between fluxes of nitrate and AON or ammonium and AON. Possible sources for AON include byproducts of reactions between NOx and hydrocarbons, marine and terrestrial sources of reduced (amino acid) N and the long-range transport of organic matter (dust, pollen etc.) and bacteria. Both dust and organic nitrates such as PAN appear to play an important role in the overall flux of AON to the surface of the earth. For estimates of organic nitrate deposition, we also use an atmospheric chemical transport model to evaluate the spatial distribution of fluxes and the globally integrated deposition values. Our preliminary estimate of the magnitude of global AON fluxes places the flux between 10 and 50 Tg of N per year with substantial unresolved uncertainties but clear indications that AON deposition is an important aspect of local and global atmospheric N budgets and deserves further consideration.

Regional variation in foliar chemistry and n cycling among forests of diverse history and composition

Abstract: Although understanding of nitrogen cycling and nitrification in forest ecosystems has improved greatly over the past several decades, our ability to characterize spatial patterns is still quite limited. A number of studies have shown linkages between canopy chemistry and N cycling, but few have considered the degree to which these trends can provide an indicator of forest N status across large, heterogeneous landscapes. In this study, we examined relationships among canopy chemistry, nitrogen cycling, and soil carbon:nitrogen ratios across 30 forested stands in the White Mountains of New Hampshire. Plots included a range of species (sugar maple, red maple, American beech, yellow birch, paper birch, red spruce, balsam fir, eastern hemlock) and were broadly grouped into two disturbance categories: those that were historically affected by intensive logging and/or fire and those that experienced minimal human disturbance. Across all plots, rates of net N mineralization and net nitrification were correlated wi...

A 1400-year high-resolution record of atmospheric circulation over the North Atlantic and Asia:

Abstract: Major ion series developed from new subannual scale sampling of an ice core from central Greenland are calibrated with instrumental series of atmospheric sea-level pressure recording major marine (Icelandic Low) and terrestrial (Siberian High) atmospheric circulation systems to provide proxy records of atmospheric circulation over the past 1400 years. Examination of the proxy records reveals: major changes in behaviour of these systems c. ad 1400, multidecadal- and centennial-scale periodic components, characterization of mean sea-level pressure anomaly fields during the ‘Little Ice Age’ and the ‘Mediaeval Warm Period’, the potential role of solar forcing, coupled ocean-atmosphere associations, and a perspective within which the characteristics of instrumental-era climate can be assessed.

Returns on Investments in Information Technology: A Research Synthesis

Abstract: Understanding the return on investments in information technology (IT) is the focus of a large and growing body of research. The objective of this paper is to synthesize this research and develop a model to guide future research in the evaluation of information technology investments. We focus on archival studies that use accounting or market measures of firm performance. We emphasize those studies where accounting researchers with interest in market‐level analyses of systems and technology issues may hold a competitive advantage over traditional information systems (IS) researchers. We propose numerous opportunities for future research. These include examining the relation between IT and business processes, and business processes and overall firm performance, understanding the effect of contextual factors on the IT‐performance relation, examining the IT‐performance relation in an international context, and examining the interactive effects of IT spending and IT management on firm performance.

An integrated model of soil, hydrology, and vegetation for carbon dynamics in wetland ecosystems

Abstract: [1] Wetland ecosystems are an important component in global carbon (C) cycles and may exert a large influence on global climate change. Predictions of C dynamics require us to consider interactions among many critical factors of soil, hydrology, and vegetation. However, few such integrated C models exist for wetland ecosystems. In this paper, we report a simulation model, Wetland-DNDC, for C dynamics and methane (CH4) emissions in wetland ecosystems. The general structure of Wetland-DNDC was adopted from PnET-N-DNDC, a process-oriented biogeochemical model that simulates C and N dynamics in upland forest ecosystems. Several new functions and algorithms were developed for Wetland-DNDC to capture the unique features of wetland ecosystems, such as water table dynamics, growth of mosses and herbaceous plants, and soil biogeochemical processes under anaerobic conditions. The model has been validated against various observations from three wetland sites in Northern America. The validation results are in agreement with the measurements of water table dynamics, soil temperature, CH4 fluxes, net ecosystem productivity (NEP), and annual C budgets. Sensitivity analysis indicates that the most critical input factors for C dynamics in the wetland ecosystems are air temperature, water outflow parameters, initial soil C content, and plant photosynthesis capacity. NEP and CH4 emissions are sensitive to many of the tested input variables. By integrating the primary drivers of climate, hydrology, soil and vegetation, the Wetland-DNDC model is capable of predicting C biogeochemical cycles in wetland ecosystems.

Combining remote sensing and ground census data to develop new maps of the distribution of rice agriculture in China

Abstract: [1] Large-scale assessments of the potential for food production and its impact on biogeochemical cycling require the best possible information on the distribution of cropland. This information can come from ground-based agricultural census data sets and/ or spaceborne remote sensing products, both with strengths and weaknesses. Official cropland statistics for China contain much information on the distribution of crop types, but are known to significantly underestimate total cropland areas and are generally at coarse spatial resolution. Remote sensing products can provide moderate to fine spatial resolution estimates of cropland location and extent, but supply little information on crop type or management. We combined county-scale agricultural census statistics on total cropland area and sown area of 17 major crops in 1990 with a fine-resolution land-cover map derived from 1995–1996 optical remote sensing (Landsat) data to generate 0.5� resolution maps of the distribution of rice agriculture in mainland China. Agricultural census data were used to determine the fraction of crop area in each 0.5� grid cell that was in single rice and each of 10 different multicrop paddy rice rotations (e.g., winter wheat/ rice), while the remote sensing land-cover product was used to determine the spatial distribution and extent of total cropland in China. We estimate that there were 0.30 million km 2 of paddy rice cropland; 75% of this paddy land was multicropped, and 56% had two rice plantings per year. Total sown area for paddy rice was 0.47 million km 2 . Paddy rice agriculture occurred on 23% of all cultivated land in China. INDEX TERMS: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 1615 Global Change: Biogeochemical processes (4805); KEYWORDS: paddy rice, maps, China, multicropping rotation, Landsat

Hypsometry and Volume of the Arctic Ocean and Its Constituent Seas

Abstract: [1] This paper presents an analysis of the Arctic Ocean and its constituent seas for seafloor area distribution versus depth and ocean volume. The bathymetry from the International Bathymetric Chart of the Arctic Ocean (IBCAO) is used together with limits defining this ocean and its constituent seas from the International Hydrographic Organization (IHO) as well as redefined limits constructed to confine the seas to the shallow shelves. IBCAO is a bathymetric grid model with a resolution of 2.5 × 2.5 km, which significantly improved the portrayal of the Arctic Ocean seafloor through incorporation of newly released bathymetric data including echo soundings from U.S. and British navies, scientific nuclear submarine cruises, and icebreaker cruises. This analysis of seafloor area and ocean volume is the first for the Arctic Ocean based on this new and improved portrayal of the seafloor as represented by IBCAO. The seafloor area and volume are calculated for different depths starting from the present sea level and progressing in increments of 10 m to a depth of 500 m and in increments of 50 m from 550 m down to the deepest depth within each of the analyzed seas. Hypsometric curves expressed as simple histograms of the frequencies in different depth bins and depth plotted against cumulative area for each of the analyzed seas are presented. The area and volume calculations show that the entire IHO-defined Arctic Ocean makes up ∼4.3% of the total ocean area but only ∼1.4% of the volume. Furthermore, the IHO Arctic Ocean is the shallowest (mean depth 1201 m) of all the major oceans and their adjacent seas. The continental shelf area, from the coasts out to the shelf break, make up as much as ∼52.9% of the total area in the Arctic Ocean, defined in this work as consisting of the oceanic deep Arctic Ocean Basin; the broad continental shelves of the Barents, Kara, Laptev, East Siberian, Chukchi, and Beaufort Seas; the White Sea; and the narrow continental shelf off both the Canadian Arctic Archipelago and northern Greenland. This result indicates that the Arctic Ocean has significantly larger continental shelves compared with all the other oceans, where previous studies show that the proportion of shelves, from the coasts out to the foot of the continental slopes, only ranges between about 9.1 and 17.7%. Furthermore, the derived hypsometric curves show that most of the Arctic Ocean shelf seas besides the Barents Sea, Beaufort Sea, and the shelf off northern Greenland have a similar shape, with the largest seafloor area between 0 and 50 m. The East Siberian and Laptev seas, in particular, show area distributions concentrated in this shallow depth range, and together with the Chukchi Sea they form a large flat shallow shelf province composing as much as 22% of the entire Arctic Ocean area but only 1% of the volume. This implies that the circulation in the Arctic Ocean might be very sensitive to eustatic sea level changes. One of the aims with this work is to make up-to-date high-resolution area and volume calculations for the Arctic Ocean at various depths available for download.

Large‐scale hydro‐climatology of the terrestrial Arctic drainage system

Abstract: [1] The large-scale hydro-climatology of the terrestrial Arctic drainage system is examined, focusing on the period 1960 onward. Special attention is paid to the Ob, Yenisey, Lena, and Mackenzie watersheds, which provide the bulk of freshwater discharge to the Arctic Ocean. Station data are used to compile monthly gridded time series of gauge-corrected precipitation (P). Gridded time series of precipitation minus evapotranspiration (P−ET) are calculated from the moisture flux convergence using NCEP reanalysis data. Estimates of ET are obtained as a residual. Runoff (R) is obtained from available discharge records. For long-term water-year means, P−ET for the Yenisey, Lena, and Mackenzie watersheds is 16–20% lower than the observed runoff. In the Ob watershed, the two values agree within 9%. Given the uncertainties in P−ET, we consider the atmospheric and surface water budgets to be reasonably closed. Compared to the other three basins, the mean runoff ratio (R/P) is lower in the Ob watershed, consistent with the high fraction of annual precipitation lost through ET. All basins exhibit summer maxima in P and minima in P−ET. Summer P−ET in the Ob watershed is negative due to high ET rates. For large domains in northern Eurasia, about 25% of July precipitation is associated with the recycling of water vapor evapotranspirated within each domain. This points to a significant effect of the land surface on the hydrologic regime. Variability in P and P−ET has generally clear associations with the regional atmospheric circulation. A strong link with the Urals trough is documented for the Ob. Relationships with indices of the Arctic Oscillation and other teleconnections are generally weak. Water-year time series of runoff and P−ET are strongly correlated in the Lena watershed only, reflecting extensive permafrost. Cold-season runoff has increased in the Yenisey and Lena watersheds. This is most pronounced in the Yenisey watershed, where runoff has also increased sharply in spring, decreased in summer, but has increased for the year as a whole. The mechanisms for these changes are not entirely clear. While they fundamentally relate to higher air temperatures, increased winter precipitation, and strong summer drying, we speculate links with changes in active layer thickness and thawing permafrost.

Mammalian dispersal at the Paleocene/Eocene boundary.

Abstract: A profound faunal reorganization occurred near the Paleocene/Eocene boundary, when several groups of mammals abruptly appeared on the Holarctic continents. To test the hypothesis that this event featured the dispersal of groups from Asia to North America and Europe, we used isotope stratigraphy, magnetostratigraphy, and quantitative biochronology to constrain the relative age of important Asian faunas. The extinct family Hyaenodontidae appeared in Asia before it did so in North America, and the modern orders Primates, Artiodactyla, and Perissodactyla first appeared in Asia at or before the Paleocene/Eocene boundary. These results are consistent with Asia being a center for early mammalian origination.

Copepod hatching success in marine ecosystems with high diatom concentrations

Abstract: Diatoms dominate spring bloom phytoplankton assemblages in temperate waters and coastal upwelling regions of the global ocean. Copepods usually dominate the zooplankton in these regions and are the prey of many larval fish species. Recent laboratory studies suggest that diatoms may have a deleterious effect on the success of copepod egg hatching. These findings challenge the classical view of marine food-web energy flow from diatoms to fish by means of copepods. Egg mortality is an important factor in copepod population dynamics, thus, if diatoms have a deleterious in situ effect, paradoxically, high diatom abundance could limit secondary production. Therefore, the current understanding of energy transfer from primary production to fisheries in some of the most productive and economically important marine ecosystems may be seriously flawed. Here we present in situ estimates of copepod egg hatching success from twelve globally distributed areas, where diatoms dominate the phytoplankton assemblage. We did not observe a negative relationship between copepod egg hatching success and either diatom biomass or dominance in the microplankton in any of these regions. The classical model for diatom-dominated system remains valid.