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Sample records for north american atlantic

  1. Structure of the North American Atlantic Continental Margin.

    ERIC Educational Resources Information Center

    Klitgord, K. K.; Schlee, J. S.

    1986-01-01

    Offers explanations on the origin of the North American Atlantic continental margin. Provides an analysis and illustrations of structural and strategraphic elements of cross sections of the Atlantic continental margin. Also explains the operations and applications of seismic-relection profiles in studying ocean areas. (ML)

  2. Linking North Atlantic Teleconnections to Latitudinal Variability of Wave Climate Along the North American Atlantic Coast

    NASA Astrophysics Data System (ADS)

    Provancha, C.; Adams, P. N.; Hegermiller, C.; Storlazzi, C. D.

    2015-12-01

    Shoreline change via coastal erosion and accretion is largely influenced by variations in ocean wave climate. Identifying the sources of these variations is challenging because the timing of wave energy delivery varies over multiple timescales within ocean basins. We present the results of an investigation of USACE Wave Information Studies hindcast hourly wave heights, periods, and directions along the North American Atlantic coast from 1980-2012, designed to explore links between wave climate and teleconnection patterns. Trends in median and extreme significant wave heights (SWHs) demonstrate that mean monthly SWHs increased from 1 to 5 cm/yr along the roughly 3000 km reach of study area, with changes in hurricane season waves appearing to be most influential in producing the overall trends. Distributions of SWHs categorized by North Atlantic Oscillation (NAO) phase, show that positive-period NAO SWHs are greater than negative-period NAO SWHs along the entire eastern seaboard (25°N to 45°N). The most prominent wave direction off Cape Cod, MA during positive-period NAO is approximately 105°, as compared to approximately 75° during negative-period NAO. Prominent wave directions between Cape Canaveral, FL, and Savannah, GA exhibit a similar shift but during opposite phases of the NAO. The results of this analysis suggest that the atmosphere-ocean interactions associated with contrasting NAO phases can significantly change the wave climate observed offshore along the North American Atlantic coast, altering alongshore wave energy fluxes and sediment transport patterns along the coast.

  3. Synoptic Scale North American Weather Tracks and the Formation of North Atlantic Windstorms

    NASA Astrophysics Data System (ADS)

    Baum, A. J.; Godek, M. L.

    2014-12-01

    Each winter, dozens of fatalities occur when intense North Atlantic windstorms impact Western Europe. Forecasting the tracks of these storms in the short term is often problematic, but long term forecasts provide an even greater challenge. Improved prediction necessitates the ability to identify these low pressure areas at formation and understand commonalities that distinguish these storms from other systems crossing the Atlantic, such as where they develop. There is some evidence that indicates the majority of intense windstorms that reach Europe have origins far west, as low pressure systems that develop over the North American continent. This project aims to identify the specific cyclogenesis regions in North America that produce a significantly greater number of dangerous storms. NOAA Ocean Prediction Center surface pressure reanalysis maps are used to examine the tracks of storms. Strong windstorms are characterized by those with a central pressure of less than 965 hPa at any point in their life cycle. Tracks are recorded using a coding system based on source region, storm track and dissipation region. The codes are analyzed to determine which region contains the most statistical significance with respect to strong Atlantic windstorm generation. The resultant set of codes also serves as a climatology of North Atlantic extratropical cyclones. Results indicate that a number of windstorms favor cyclogenesis regions off the east coast of the United States. A large number of strong storms that encounter east coast cyclogenesis zones originate in the central mountain region, around Colorado. These storms follow a path that exits North America around New England and subsequently travel along the Canadian coast. Some of these are then primed to become "bombs" over the open Atlantic Ocean.

  4. Atlantic Ocean forcing of North American and European summer climate.

    PubMed

    Sutton, Rowan T; Hodson, Daniel L R

    2005-07-01

    Recent extreme events such as the devastating 2003 European summer heat wave raise important questions about the possible causes of any underlying trends, or low-frequency variations, in regional climates. Here, we present new evidence that basin-scale changes in the Atlantic Ocean, probably related to the thermohaline circulation, have been an important driver of multidecadal variations in the summertime climate of both North America and western Europe. Our findings advance understanding of past climate changes and also have implications for decadal climate predictions.

  5. Atlantic Ocean forcing of North American and European summer climate.

    PubMed

    Sutton, Rowan T; Hodson, Daniel L R

    2005-07-01

    Recent extreme events such as the devastating 2003 European summer heat wave raise important questions about the possible causes of any underlying trends, or low-frequency variations, in regional climates. Here, we present new evidence that basin-scale changes in the Atlantic Ocean, probably related to the thermohaline circulation, have been an important driver of multidecadal variations in the summertime climate of both North America and western Europe. Our findings advance understanding of past climate changes and also have implications for decadal climate predictions. PMID:15994552

  6. Climate and ecosystem linkages explain widespread declines in North American Atlantic salmon populations.

    PubMed

    Mills, Katherine E; Pershing, Andrew J; Sheehan, Timothy F; Mountain, David

    2013-10-01

    North American Atlantic salmon (Salmo salar) populations experienced substantial declines in the early 1990s, and many populations have persisted at low abundances in recent years. Abundance and productivity declined in a coherent manner across major regions of North America, and this coherence points toward a potential shift in marine survivorship, rather than local, river-specific factors. The major declines in Atlantic salmon populations occurred against a backdrop of physical and biological shifts in Northwest Atlantic ecosystems. Analyses of changes in climate, physical, and lower trophic level biological factors provide substantial evidence that climate conditions directly and indirectly influence the abundance and productivity of North American Atlantic salmon populations. A major decline in salmon abundance after 1990 was preceded by a series of changes across multiple levels of the ecosystem, and a subsequent population change in 1997, primarily related to salmon productivity, followed an unusually low NAO event. Pairwise correlations further demonstrate that climate and physical conditions are associated with changes in plankton communities and prey availability, which are ultimately linked to Atlantic salmon populations. Results suggest that poor trophic conditions, likely due to climate-driven environmental factors, and warmer ocean temperatures throughout their marine habitat area are constraining the productivity and recovery of North American Atlantic salmon populations.

  7. Reddish Egret extends its breeding range along the North American Atlantic coast into South Carolina

    USGS Publications Warehouse

    Ferguson, L.M.; Jodice, P.G.R.; Post, W.; Sanders, F.I.

    2005-01-01

    We report the northernmost breeding record of the Reddish Egret (Egretta rufescens) along the North American Atlantic Coast. Nesting activity was first seen in late May 2004, and on 6 July 2004 a nest was discovered with two young chicks on Marsh Island, a barrier island located within Cape Romain National Wildlife Refuge, South Carolina, USA. Reddish Egret nestlings were last observed within 1 m of the nest on 30 July 2004. This represents a northward extension of ca. 450 km in the breeding range of this species and, for the U.S. Atlantic Coast, the only recorded instance of nesting north of Florida.

  8. Moisture transport by Atlantic tropical cyclones onto the North American continent

    NASA Astrophysics Data System (ADS)

    Xu, Guangzhi; Osborn, Timothy J.; Matthews, Adrian J.

    2016-07-01

    Tropical Cyclones (TCs) are an important source of freshwater for the North American continent. Many studies have tried to estimate this contribution by identifying TC-induced precipitation events, but few have explicitly diagnosed the moisture fluxes across continental boundaries. We design a set of attribution schemes to isolate the column-integrated moisture fluxes that are directly associated with TCs and to quantify the flux onto the North American Continent due to TCs. Averaged over the 2004-2012 hurricane seasons and integrated over the western, southern and eastern coasts of North America, the seven schemes attribute 7-18 % (mean 14 % ) of total net onshore flux to Atlantic TCs. A reduced contribution of 10 % (range 9-11 % ) was found for the 1980-2003 period, though only two schemes could be applied to this earlier period. Over the whole 1980-2012 period, a further 8 % (range 6-9 % from two schemes) was attributed to East Pacific TCs, resulting in a total TC contribution of 19 % (range 17-22 % ) to the ocean-to-land moisture transport onto the North American continent between May and November. Analysis of the attribution uncertainties suggests that incorporating details of individual TC size and shape adds limited value to a fixed radius approach and TC positional errors in the ERA-Interim reanalysis do not affect the results significantly, but biases in peak wind speeds and TC sizes may lead to underestimates of moisture transport. The interannual variability does not appear to be strongly related to the El Niño-Southern Oscillation phenomenon.

  9. North Atlantic and orbital controls on North American Monsoon rainfall for the past 25,000 years

    NASA Astrophysics Data System (ADS)

    Lachniet, M. S.; Bernal-Uruchurtu, J. P.; Asmerom, Y.; Polyak, V.; Vazquez-Selem, L.

    2011-12-01

    The paleoclimate controls on Mexican rainfall remain poorly understood, making it difficult to test hypotheses of late Quaternary climate changes in the North American Monsoon region. A high-resolution and chronologically robust integrative paleoclimate history for central and southwestern Mexico is required to evaluate the climate context associated with the late glacial peopling of Mesoamerica, the Holocene domestication of maize, and climate's influence on several advanced pre-Colombian civilizations. Herein, we combine new and previously published precipitation- and temperature-sensitive proxy records to delineate the paleoclimatic history of the "Mesoamerican Monsoon" region since ca. 25,000 yr BP, from stalagmite, glacial, and lacustrine paleoclimatic data. Our results demonstrate a wet last glacial maximum (23 to 18 ka) in southwestern Mexico at 17.4 degrees N, a region that today is outside the influence of nortes or the westerlies. Wet conditions may be attributed to a moderately strong summer monsoon due to near-modern summer insolation values and a cooler eastern tropical Pacific Ocean akin to a modern La Niña-like state. We also document Heinrich stadial 1 and Younger Dryas monsoon weakening coincident with reduced North Atlantic thermohaline circulation, which implicates reduced onshore moisture flux due to a weaker and more southerly position of the Intertropical Convergence Zone. Mesoamerican rainfall was greatest during the early Holocene, and decreased non-linearly to the present in concert with decreasing local summer insolation. Following a relative mid-Holocene wet period, the last 4.5 ka are characterized by increasingly dry conditions, likely related to decreasing summer insolation and a greater El Niño frequency.

  10. A statistical overview of mass movement characteristics on the North American atlantic outer continental margin

    USGS Publications Warehouse

    Booth, James S.; O'Leary, Dennis W.

    1992-01-01

    An analysis of 179 mass movements on the North American Atlantic continental slope and upper rise shows that slope failures have occurred throughout the geographic extent of the outer margin. Although the slope failures show no striking affinity for a particular depth as an origination level, there is a broad, primary mode centered at about 900 m. The resulting slides terminate at almost all depths and have a primary mode at 1100 m, but the slope/rise boundary (at 2200 m) also is an important mode. Slope failures have occurred at declivities ranging from 1° to 30° (typically, 4°); the resultant mass movement deposits vary in width from 0.2 to 50 km (typically, 1-2 km) and in length from 0.3 to 380 km (typically, 2–4 km), and they have been reported to be as thick as 650 m. On a numeric basis, mass movements are slightly more prevalent on open slopes than in other physiographic settings, and both translational and rotational failure surfaces are common. The typical mass movement is disintegrative in nature. Open slope slides tend to occur at lower slope angles and are larger than canyon slides. Further, large‐scale slides rather than small‐scale slides tend to originate on gentle slopes (≍ 3-4°). Rotational slope failures appear to have a slightly greater chance of occurring in canyons, but there is no analogous bias associated with translational failures. Similarly, disintegrative slides seem more likely to be associated with rotational slope failures than translational ones and are longer than their nondisintegrative counterparts. The occurrence of such a variety of mass movements at low declivities implies that a regional failure mechanism has prevailed. We suggest that earthquakes or, perhaps in some areas, gas hydrates are the most likely cause of the slope failures.

  11. North Atlantic Circulation

    NASA Astrophysics Data System (ADS)

    Molinari, R.; Bryan, K.; Schott, F.

    The intensity of the North Atlantic winddriven and thermohaline circulation and the close proximity of many oceanographic installations make the North Atlantic a particularly favored region of the world ocean from the standpoint of research in ocean circulation. Recent increases in available data and advances in numerical modeling techniques served as the impetus to convene a joint workshop of modelers and observers working on the North Atlantic with the Scientific Committee on Oceanic Research (SCOR) Working Group (WG) 68 (“North Atlantic Circulation”). Goals of the workshop were to provide an update on data sets and models and to discuss the poleward heat flux problem and possible monitoring strategies. The joint Workshop/SCOR WG-68 meeting was convened by F. Schott (chairman of the working group; Rosenstiel School of Marine and Atmospheric Science, Miami, Fla.), K. Bryan (National Oceanic and Atmospheric Administration/ Geophysical Fluid Dynamics Laboratory (NOAA/GFDL)), and R. Molinari (NOAA/Atlantic Oceanographic and Meteorological Laboratory (NOAA/AOML)).

  12. North Atlantic Bloom

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Reminiscent of the distinctive swirls in a Van Gogh painting, millions of microscopic plants color the waters of the North Atlantic with strokes of blue, turquoise, green, and brown. Fed by nutrients that have built up during the winter and the long, sunlit days of late spring and early summer, the cool waters of the North Atlantic come alive every year with a vivid display of color. The microscopic plants, called phytoplankton, that give the water this color are the base of the marine food chain. Some species of phytoplankton are coated with scales of calcium (chalk), which turn the water electric blue. Chlorophyll and other light-capturing pigments in others give the water a deep green hue. The proliferation of many different species in various stages of growth and decay provides many nuances of color in this concentrated bloom. The bloom stretches across hundreds of kilometers, well beyond the edges of this photo-like image, captured on June 23, 2007, by the Moderate Resolution Imaging Spectroradiometer (MODIS) flying aboard NASA's Aqua satellite. The upper left edge of the image is bounded by Greenland. Iceland is in the upper right. Plumes of dust are blowing off the island, probably adding nutrients to the surface waters to its south. NASA image courtesy Norman Kuring, Ocean Color Group at NASA Goddard Space Flight Center

  13. Chriolepis prolata, a new species of Atlantic goby (Teleostei: Gobiidae) from the North American continental shelf.

    PubMed

    Hastings, Philip A; Findley, Lloyd T

    2015-01-08

    A new species of seven-spined goby of the genus Chriolepis is described from five specimens collected from the continental shelf of the northeastern Gulf of Mexico and Atlantic Ocean off South Carolina in depths of ca 54 to 110 m. The "Platform Goby", Chriolepis prolata, is distinguishable from all other western Atlantic species currently assigned to the genus Chriolepis and the morphologically similar genus Varicus in having pelvic-fin rays one through four branched, the fifth (innermost) pelvic-fin ray unbranched and relatively long (longer than the second ray to longer than all other pelvic-fin rays); most lateral body scales ctenoid, extending anteriorly in a wedge to a level anterior to the first dorsal-fin insertion or nearly to the pectoral-fin axil, with two or more rows of small cycloid scales extending anteriorly to near the pectoral-fin axil, cycloid scales along the bases of the dorsal and anal fins, and no scales on the belly; and the first two anal-fin pterygiophores inserted anterior to the first haemal spine. It closely resembles C. bilix but differs from that species which has a scaled belly, a shorter fifth pelvic-fin ray, prolonged dorsal-fin spines and smaller teeth in the lower jaw. An earlier report of C. bilix from Florida waters apparently refers to C. prolata. 

  14. Seasonal predictability of the North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

    Vellinga, Michael; Scaife, Adam

    2015-04-01

    Until recently, long-range forecast systems showed only modest levels of skill in predicting surface winter climate around the Atlantic Basin and associated fluctuations in the North Atlantic Oscillation at seasonal lead times. Here we use a new forecast system to assess seasonal predictability of winter North Atlantic climate. We demonstrate that key aspects of European and North American winter climate and the surface North Atlantic Oscillation are highly predictable months ahead. We demonstrate high levels of prediction skill in retrospective forecasts of the surface North Atlantic Oscillation, winter storminess, near-surface temperature, and wind speed, all of which have high value for planning and adaptation to extreme winter conditions. Analysis of forecast ensembles suggests that while useful levels of seasonal forecast skill have now been achieved, key sources of predictability are still only partially represented and there is further untapped predictability. This work is distributed under the Creative Commons Attribution 3.0 Unported License together with an author copyright. This license does not conflict with the regulations of the Crown Copyright.

  15. North Atlantic Coastal Tidal Wetlands

    EPA Science Inventory

    The book chapter provides college instructors, researchers, graduate and advanced undergraduate students, and environmental consultants interested in wetlands with foundation information on the ecology and conservation concerns of North Atlantic coastal wetlands. The book c...

  16. North Atlantic Deep Water Formation

    NASA Technical Reports Server (NTRS)

    Bennett, T. (Editor); Broecker, W. S. (Editor); Hansen, J. (Editor)

    1984-01-01

    Various studies concerning differing aspects of the North Atlantic are presented. The three major topics under which the works are classified include: (1) oceanography; (2) paleoclimate; and (3) ocean, ice and climate modeling.

  17. Species profiles: life histories and environmental requirements of coastal fishes and invertebrates (North Atlantic) - American oyster

    SciTech Connect

    Sellers, M.A.; Stanley, J.G.

    1984-07-01

    The American oyster, Crassostrea virginica, is an important commercial and mariculture species. Spawning occurs repeatedly during warmer months with millions of eggs released. Embryos and larvae are carried by currents throughout the estuaries and oceanic bays where they occur. The few surviving larvae cement themselves to a solid object, where they remain for the remainder of life. Unable to move, they must tolerate changes in the environment that range from -1.7/sup 0/ to 49/sup 0/C, 5 to 30 ppt salinity, and clear or muddy water. 88 references, 2 figures, 1 table.

  18. Population genetics of the American eel (Anguilla rostrata): FST = 0 and North Atlantic Oscillation effects on demographic fluctuations of a panmictic species.

    PubMed

    Côté, Caroline L; Gagnaire, Pierre-Alexandre; Bourret, Vincent; Verreault, Guy; Castonguay, Martin; Bernatchez, Louis

    2013-04-01

    We performed population genetic analyses on the American eel (Anguilla rostrata) with three main objectives. First, we conducted the most comprehensive analysis of neutral genetic population structure to date to revisit the null hypothesis of panmixia in this species. Second, we used this data to provide the first estimates of contemporary effective population size (Ne ) and to document temporal variation in effective number of breeders (Nb ) in American eel. Third, we tested for statistical associations between temporal variation in the North Atlantic Oscillation (NAO), the effective number of breeders and two indices of recruit abundance. A total of 2142 eels from 32 sampling locations were genotyped with 18 microsatellite loci. All measures of differentiation were essentially zero, and no evidence for significant spatial or temporal genetic differentiation was found. The panmixia hypothesis should thus be accepted for this species. Nb estimates varied by a factor of 23 among 12 cohorts, from 473 to 10,999. The effective population size Ne was estimated at 10,532 (95% CI, 9312-11,752). This study also showed that genetically based demographic indices, namely Nb and allelic richness (Ar), can be used as surrogates for the abundance of breeders and recruits, which were both shown to be positively influenced by variation during high (positive) NAO phases. Thus, long-term genetic monitoring of American glass eels at several sites along the North American Atlantic coast would represent a powerful and efficient complement to census monitoring to track demographic fluctuations and better understand their causes.

  19. Atlantic salmon, Salmo salar L. are broadly susceptible to isolates representing the North American genogroups of infectious hematopoietic necrosis virus

    USGS Publications Warehouse

    Kurath, Gael; Winton, James R.; Dale, Ole Bendik; Purcell, Maureen K.; Falk, Knut; Busch, Robert D.

    2016-01-01

    Beginning in 1992, three epidemic waves of infectious hematopoietic necrosis, often with high mortality, occurred in farmed Atlantic salmon Salmo salar L. on the west coast of North America. We compared the virulence of eleven strains of infectious hematopoietic necrosis virus (IHNV), representing the U, M and L genogroups, in experimental challenges of juvenile Atlantic salmon in freshwater. All strains caused mortality and there was wide variation within genogroups: cumulative mortality for five U-group strains ranged from 20 to 100%, four M-group strains ranged 30-63% and two L-group strains varied from 41 to 81%. Thus, unlike Pacific salmonids, there was no apparent correlation of virulence in a particular host species with virus genogroup. The mortality patterns indicated two different phenotypes in terms of kinetics of disease progression and final per cent mortality, with nine strains having moderate virulence and two strains (from the U and L genogroups) having high virulence. These phenotypes were investigated by histopathology and immunohistochemistry to describe the variation in the course of IHNV disease in Atlantic salmon. The results from this study demonstrate that IHNV may become a major threat to farmed Atlantic salmon in other regions of the world where the virus has been, or may be, introduced.

  20. On the North Atlantic circulation

    SciTech Connect

    Schmitz, W.J. Jr.; McCartney, M.S. )

    1993-02-01

    A summary for North Atlantic circulation is proposed to replace the circulation scheme hypothesized by Worthington in 1976. Divergences from the previous model are in thermohaline circulation, cross-equatorical transport and Florida Current sources, flow in the eastern Atlantic, circulation in the Newfoundland Basin, slope water currents, and flow pattern near the Bahamas. The circulation patterns presented here are consistent with the majority of of published accounts of flow components. 77 refs., 14 figs., 3 tabs.

  1. North American Biome

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The North America biome includes the major ecoregions that make up the land area of Canada, the United States, Mexico, and countries in Central America. The biome is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the s...

  2. On the North Atlantic Circulation

    NASA Astrophysics Data System (ADS)

    Schmitz, William J.; McCartney, Michael S.

    1993-02-01

    A new, speculative, and, we hope, provocative summary of the North Atlantic circulation is described, including both horizontal currents (wind-driven) and the primarily (thermohaline) meridional flows that involve the transformation of warm to cold water at high latitudes. Our picture is based on a synthesis of a variety of independent investigations that are contained in the literature as opposed to a presentation of the results of one technique or the point of view of one author. We describe a thermohaline cell (the so-called thermohaline conveyor belt) that is concentrated within the Atlantic and Southern oceans (rather than essentially global), with the most important upwelling sites being in the circumpolar and the equatorial current regimes. We concentrate on deep water formation and its replacement relative to intermediate-water formation. It has been pointed out recently that the formation of 13 Sv (1 Sv = 106 m³ s-1) of southward flowing North Atlantic Deep Water is compensated for in the upper ocean by northward cross-equatorial transport. We suggest that this thermocline layer flow passes through the Straits of Florida, transits the Gulf Stream system on its inshore side, and exits through the North Atlantic Current system after recirculation and modification. There is now a clear observational basis for the structure of recirculating gyres on the southern and northern sides of the Gulf Stream. We suggest a recirculation for the North Atlantic Current as well. We also describe a C-shaped component to the southern Gulf Stream recirculation and identify a roughly 10-Sv circulation in the eastern North Atlantic associated with the Azores Current. Recirculations play an important role in deep boundary current regimes and in water mass formation and modification. The transport of the deep western and northern boundary currents in the North Atlantic Ocean may be boosted (roughly doubled or tripled) by counterclockwise recirculating gyres and by additions of

  3. Climatic Variability over the North Atlantic

    NASA Astrophysics Data System (ADS)

    Hurrell, J.; Hoerling, M. P.; Folland, C. K.

    INTRODUCTION WHAT IS THE NORTH ATLANTIC OSCILLATION AND HOW DOES IT IMPACT REGIONAL - CLIMATE? WHAT ARE THE MECHANISMS THAT GOVERN NORTH ATLANTIC OSCILLATION VARIABILITY? Atmospheric Processes Ocean Forcing of the Atmosphere CONCLUDING COMMENTS ON THE OTHER ASPECTS OF NORTH ATLANTIC CLIMATE - VARIABILITY REFERENCES

  4. 3. VIEW LOOKING NORTH WEST OVER CENTRAL ATLANTIC WITH ATLANTIC ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. VIEW LOOKING NORTH WEST OVER CENTRAL ATLANTIC WITH ATLANTIC OCEAN IN THE FOREGROUND. DENNIS HOTEL, BLENHEIM HOTEL, AND MARLBOROUGH HOTEL (LEFT TO RIGHT) ARE LOCATED IN THE CENTER OF THE PHOTOGRAPH. THE CLARIDGE HOTEL IS THE HIGHRISE IMMEDIATELY TO THE RIGHT OF THE MARLBOROUGH HOTEL - Marlborough, Blenheim & Dennis Hotels (aerial views), Between Park Place, Michigan Avenue & Boardwalk, Atlantic City, Atlantic County, NJ

  5. Probable changes in lake chemistry in CanadaÂ’s Atlantic Provinces under proposed North American emission reductions

    NASA Astrophysics Data System (ADS)

    Clair, Thomas A.; Dennis, Ian F.; Cosby, B. J.

    Atlantic Canada, located in the extreme north-eastern portion of North America, receives acid precipitation from all major acid emission sources on the eastern part of the continent. The region was glaciated and has thin soils over a generally poorly acid buffering bedrock. Because of regional topography, large groupings of lakes occur in a number of regions. Environment Canada and the Government of New Brunswick have operated lake sampling networks in trend detection studies and have concentrated their work on these lake groupings. The MAGIC model has been applied to these lakes and their catchments to see: a) what initial water chemistry conditions existed before acidification began, b) what the chemistry was like during the worst of regional acid deposition, and c) what it would be like under deposition conditions predicted for new Canadian and US emission reduction proposals. While pH, sulphate, acid neutralisation capacity (ANC) and the sum of the base cations (SBC) of all lakes have been significantly affected by acid deposition, water chemistry conditions are now considerably better than they were in 1975, at the worst of the deposition. However, a 50% reduction in acid deposition from Year 2000 deposition amounts will not return water chemistry to original conditions in most of the region.

  6. North American patience

    SciTech Connect

    1994-12-01

    Independent power companies are facing numerous changes in power markets across North America. While changes bring uncertainty, they also hold promise for future competitive power opportunities. Included are new capacity, repowering aging infrastructure and the role of power brokers. It is likely that patience has never been a more valuable attribute for companies working in the North American market.

  7. North American encephalitic arboviruses

    PubMed Central

    Davis, Larry E.; Beckham, J. David; Tyler, Kenneth L.

    2008-01-01

    Synopsis Arboviruses continue to be a major cause of encephalitis in North America and West Nile virus neuroinvasive disease is now the dominant cause of encephalitis. Transmission to humans of North American arboviruses occurs by infected mosquitoes or ticks. Most infections are asymptomatic or produce a flu-like illness. Elderly, immunosuppressed individuals and infants for some arboviruses have the highest incidence of severe encephalitis. Rapid serum or CSF IgM antibody capture ELISA assays are now available to diagnosis the acute infection for all North American arboviruses. Unfortunately, no antiviral drugs are approved for the treatment of arbovirus infection and current therapy is supportive. PMID:18657724

  8. An Integrated Mercury Monitoring Program for Temperate Estuarine and Marine Ecosystems on the North American Atlantic Coast

    PubMed Central

    Evers, David C.; Mason, Robert P.; Kamman, Neil C.; Chen, Celia Y.; Bogomolni, Andrea L.; Taylor, David L.; Hammerschmidt, Chad R.; Jones, Stephen H.; Burgess, Neil M.; Munney, Kenneth; Parsons, Katharine C.

    2008-01-01

    During the past century, anthropogenic activities have altered the distribution of mercury (Hg) on the earth’s surface. The impacts of such alterations to the natural cycle of Hg can be minimized through coordinated management, policy decisions, and legislative regulations. An ability to quantitatively measure environmental Hg loadings and spatiotemporal trends of their fate in the environment is critical for science-based decision making. Here, we outline a Hg monitoring program for temperate estuarine and marine ecosystems on the Atlantic Coast of North America. This framework follows a similar, previously developed plan for freshwater and terrestrial ecosystems in the United States. Methylmercury (MeHg) is the toxicologically relevant form of Hg, and its ability to bioaccumulate in organisms and biomagnify in food webs depends on numerous biological and physicochemical factors that affect its production, transport, and fate. Therefore, multiple indicators are needed to fully characterize potential changes of Hg loadings in the environment and MeHg bioaccumulation through the different marine food webs. In addition to a description of how to monitor environmental Hg loads for air, sediment, and water, we outline a species-specific matrix of biotic indicators that include shellfish and other invertebrates, fish, birds and mammals. Such a Hg monitoring template is applicable to coastal areas across the Northern Hemisphere and is transferable to arctic and tropical marine ecosystems. We believe that a comprehensive approach provides an ability to best detect spatiotemporal Hg trends for both human and ecological health, and concurrently identify food webs and species at greatest risk to MeHg toxicity. PMID:19294469

  9. From Europe to America: Pliocene to Recent trans-Atlantic expansion of cold-water North Atlantic molluscs

    PubMed Central

    Vermeij, Geerat J

    2005-01-01

    Data on the geographical distribution, phylogeny and fossil record of cool-temperate North Atlantic shell-bearing molluscs that live in waters shallower than 100 m depth belong to two biogeographic provinces, one in eastern North America north of Cape Cod, the other in northern Europe. Amphi-Atlantic species, which are found in both provinces, comprise 30.8% of the 402 species in the northeastern Atlantic and 47.3% of the 262 species in the northwestern Atlantic. Some 54.8% of these amphi-Atlantic species have phylogenetic origins in the North Pacific. Comparisons among fossil Atlantic faunas show that amphi-Atlantic distributions became established in the Middle Pliocene (about 3.5 million years ago), and that all represent westward expansions of European taxa to North America. No American taxa spread eastward to Europe without human assistance. These results are in accord with previous phylogeographic studies among populations within several amphi-Atlantic species. Explanations for the unidirectional expansion of species across the Atlantic remain uncertain, but may include smaller size and greater prior extinction of the North American as compared to the European fauna and biased transport mechanisms. Destruction of the European source fauna may jeopardize faunas on both sides of the Atlantic. PMID:16271981

  10. Atmospheric transmission of North Atlantic Heinrich events

    USGS Publications Warehouse

    Hostetler, S.W.; Clark, P.U.; Bartlein, P.J.; Mix, A.C.; Pisias, N.J.

    1999-01-01

    We model the response of the climate system during Heinrich event 2 (H2) by employing an atmospheric general circulation model, using boundary conditions based on the concept of a "canonical" Heinrich event. The canonical event is initialized with a full-height Laurentide ice sheet (LIS) and CLIMAP sea surface temperatures (SSTs), followed by lowering of the LIS, then warming of North Atlantic SSTs. Our modeled temperature and wind fields exhibit spatially variable responses over the Northern Hemisphere at each stage of the H2 event. In some regions the climatic responses are additive, whereas in other regions they cancel or are of opposite sign, suggesting that Heinrich event climatic variations may have left complex signatures in geologic records. We find variations in the tropical water balance and the mass balance of ice sheets, and implications for variations in terrestrial methane production from the contraction of northern permafrost regions and the expansion of tropical wetlands. Copyright 1999 by the American Geophysical Union.

  11. Species profiles: life histories and environmental requirements of coastal fishes and invertebrates (North Atlantic). American lobster. [Homarus americanus

    SciTech Connect

    MacKenzie, C.; Moring, J.R.

    1985-04-01

    This species profile is a literature summary of the taxonomy, morphology, distribution, life history, and environmental requirements of the American lobster (Homarus americanus). These species profiles are designed to assist in the preparation of environmental impact assessments. The American lobster is a valuable commercial shellfish. After spawning, lobsters undergo a series of molts; as adults they live in coastal and offshore waters. Lobsters are captured in baited traps and incidentally in trawls. About 5 to 6 million pounds were captured commercially in 1983, a downward trend from 1971. Major environmental factors affecting reproduction, growth, and survival are water temperature, oxygen concentration, salinity, and substrate. 82 refs., 2 figs., 3 tabs.

  12. Species profiles: Life histories and environmental requirements of coastal fishes and invertebrates (north Atlantic): American eel. [Anguilla rostrata

    SciTech Connect

    Facey, D.E.; Van Den Avyle, M.J.

    1987-08-01

    The American eel is an ecologically and economically important catadromous species that occupies freshwater streams, rivers, brackish estuaries, and the open ocean during various phases of its life cycle. Adult eels apparently spawn in the Sargasso Sea, and ocean currents transport the developing larvae northward until the young metamorphose into juveniles capable of swimming shoreward and moving upstream into coastal areas, estuaries, and rivers. Developing eels commonly remain in freshwater or brackish areas for 10-12 years before migrating to spawn. American eels tend to be bottom-dwellers and feed on a variety of fauna that occupy the same habitats. Eels occupy areas having wide ranges of temperature, salinity, and other environmental factors, suggesting broad tolerance limits, but few studies of requirements have been reported. Salinity patterns and water currents created by river discharges into coastal areas apparently provide the gradient that cues shoreward migration of juvenile eels. Alteration of patterns of freshwater inflows to estuaries and bays could affect upstream migrations.

  13. Lowermost Mantle Velocity Estimations Beneath the Central North Atlantic Area from Pdif Observed at Balkan, East Mediterranean, and American Stations

    NASA Astrophysics Data System (ADS)

    Ivan, Marian; Ghica, Daniela Veronica; Gosar, Andrej; Hatzidimitriou, Panagiotis; Hofstetter, Rami; Polat, Gulten; Wang, Rongjiang

    2015-02-01

    Lowermost mantle velocity in the area 15°S-70°N latitude/60°W-5° W longitude is estimated using two groups of observations, complementary to each other. There are 894 Pdif observations at stations in the Balkan and Eastern Mediterranean areas from 15 major earthquakes in Central and South America. Another 218 Pdif observations are associated with four earthquakes in Greece/Turkey and one event in Africa, recorded by American stations. A Pdif slowness tomographic approach of the structures immediately above the core-to-mantle boundary (CMB) is used, incorporating corrections for ellipticity, station elevation and velocity perturbations along the ray path. A low-velocity zone above CMB with a large geographical extent, approximately in the area (35-65°N) × (40-20°W), appears to have the velocity perturbations exceeding the value actually assumed by some global models. Most likely, it is extended beneath western Africa. A high-velocity area is observed west of the low-velocity zone. The results suggest that both Cape Verde and Azorean islands are located near transition areas from low-to-high velocity values in the lowermost mantle.

  14. North American plate dynamics

    NASA Technical Reports Server (NTRS)

    Richardson, Randall M.; Reding, Lynn M.

    1991-01-01

    Deformation within the North American plate in response to various tectonic processes is modeled using an elastic finite element analysis. The tectonic processes considered in the modeling include ridge forces associated with the normal thermal evolution of oceanic lithosphere, shear and normal stresses transmitted across transforms, normal stresses transmitted across convergent boundaries, stresses due to horizontal density contrasts within the continent, and shear tractions applied along the base of the plate. Model stresses are calculated with respect to a lithostatic reference stress state. Shear stresses transmitted across transform boundaries along the San Andreas and Caribbean are small, of the order of 5-10 MPa. Also, compressive stresses of the order of 5-10 MPa transmitted across the major transforms improve the fit to the data. Compressive stresses across convergent margins along the Aleutians and the Middle America trench are important.

  15. Millennial changes in North Atlantic oxygen concentrations

    NASA Astrophysics Data System (ADS)

    Hoogakker, B. A. A.; Thornalley, D. J. R.; Barker, S.

    2015-08-01

    Glacial-interglacial changes in bottom water oxygen concentrations [O2] in the deep Northeast Atlantic have been linked to decreased ventilation relating to changes in ocean circulation and the biological pump (Hoogakker et al., 2015). In this paper we discuss seawater [O2] changes in relation to millennial climate oscillations in the North Atlantic ocean over the last glacial cycle, using bottom water [O2] reconstructions from 2 cores: (1) MD95-2042 from the deep northeast Atlantic (Hoogakker et al., 2015), and (2) ODP 1055 from the intermediate northwest Atlantic. Deep northeast Atlantic core MD95-2042 shows decreased bottom water [O2] during millennial scale cool events, with lowest bottom water [O2] of 170, 144, and 166 ± 17 μmol kg-1 during Heinrich ice rafting events H6, H4 and H1. Importantly, at intermediate core ODP 1055 bottom water [O2] was lower during parts of Marine Isotope Stage 4 and millennial cool events, with lowest values of 179 and 194 μmol kg-1 recorded during millennial cool events C21 and a cool event following Dansgaard-Oeschger event 19. Our reconstructions agree with previous model simulations suggesting that glacial cold events may be associated with lower seawater [O2] across the North Atlantic below ~1 km (Schmittner et al., 2007), although in our reconstructions the changes are less dramatic. The decreases in bottom water [O2] during North Atlantic Heinrich events and earlier cold events at the deep site can be linked to water mass changes in relation to ocean circulation changes, and possibly productivity changes. At the intermediate depth site a strong North Atlantic Intermediate Water cell precludes water mass changes as a cause for decreased bottom water [O2]. Instead we propose that the lower bottom [O2] there can be linked to productivity changes through increased export of organic material from the surface ocean.

  16. Modelling non-analogue elements of Pliocene North Atlantic warming

    NASA Astrophysics Data System (ADS)

    Hill, D. J.

    2013-12-01

    the North Atlantic, including the Barents Sea. North American and European rivers have changed course, due to the newly created marginal seas and glacial rerouting, potentially affecting the salinity balance in the North Atlantic. We present simulations using the Hadley Centre coupled atmosphere-ocean HadCM3 model to estimate the impact of these changes on Atlantic Meridional Overturning Circulation (AMOC) and SST in the North Atlantic. By applying palaeogeographic changes to the standard PlioMIP Experiment 2 simulation individually and as a whole, we show that these can produce North Atlantic SST changes of a similar magnitude to data-model discrepancies. Palaeoclimate model simulations can only reproduce global and regional climate accurately if the boundary conditions given to the model are sufficient to capture all the significant changes in climate processes and dynamics. Incorporation of other important boundary condition changes and proper quantification of the model uncertainties due to unknown boundary conditions could explain existing data-model mismatches in the Pliocene North Atlantic.

  17. 22 CFR 120.31 - North Atlantic Treaty Organization.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 22 Foreign Relations 1 2014-04-01 2014-04-01 false North Atlantic Treaty Organization. 120.31 Section 120.31 Foreign Relations DEPARTMENT OF STATE INTERNATIONAL TRAFFIC IN ARMS REGULATIONS PURPOSE AND DEFINITIONS § 120.31 North Atlantic Treaty Organization. North Atlantic Treaty Organization (NATO)...

  18. 22 CFR 120.31 - North Atlantic Treaty Organization.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 22 Foreign Relations 1 2012-04-01 2012-04-01 false North Atlantic Treaty Organization. 120.31 Section 120.31 Foreign Relations DEPARTMENT OF STATE INTERNATIONAL TRAFFIC IN ARMS REGULATIONS PURPOSE AND DEFINITIONS § 120.31 North Atlantic Treaty Organization. North Atlantic Treaty Organization (NATO)...

  19. 22 CFR 120.31 - North Atlantic Treaty Organization.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 22 Foreign Relations 1 2013-04-01 2013-04-01 false North Atlantic Treaty Organization. 120.31 Section 120.31 Foreign Relations DEPARTMENT OF STATE INTERNATIONAL TRAFFIC IN ARMS REGULATIONS PURPOSE AND DEFINITIONS § 120.31 North Atlantic Treaty Organization. North Atlantic Treaty Organization (NATO)...

  20. 22 CFR 120.31 - North Atlantic Treaty Organization.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 22 Foreign Relations 1 2011-04-01 2011-04-01 false North Atlantic Treaty Organization. 120.31 Section 120.31 Foreign Relations DEPARTMENT OF STATE INTERNATIONAL TRAFFIC IN ARMS REGULATIONS PURPOSE AND DEFINITIONS § 120.31 North Atlantic Treaty Organization. North Atlantic Treaty Organization (NATO)...

  1. 22 CFR 120.31 - North Atlantic Treaty Organization.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false North Atlantic Treaty Organization. 120.31 Section 120.31 Foreign Relations DEPARTMENT OF STATE INTERNATIONAL TRAFFIC IN ARMS REGULATIONS PURPOSE AND DEFINITIONS § 120.31 North Atlantic Treaty Organization. North Atlantic Treaty Organization (NATO)...

  2. Ocean Current Boundry, North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This view of the ocean current boundry between the Gulf Stream of the North Atlantic Ocean and the coastal currents off the eastern seaboard of North America (43.5N, 65.5W), is an excellent study in ocean dynamics. The warm waters of the Gulf Stream are clearly visible as a dynamic rapidly flowing current with many internal wave patterns and a rougher surface versus the cooler and less active coastal shelf waters having a smoother surface.

  3. The North Atlantic Treaty Organization at 40.

    ERIC Educational Resources Information Center

    Baker, John A.

    1989-01-01

    Surveys the history of the North Atlantic Treaty Organization's (NATO) on the 40th anniversary of the signing of the Treaty. Highlights milestones in the Organization's history of dealing with the Soviet Union, from containment to the Intermediate-Range Nuclear Forces Treaty. Discusses needs, tasks, and challenges that NATO faces in the 1990s.…

  4. Origins of the North Atlantic Treaty.

    ERIC Educational Resources Information Center

    Rotter, Andrew J.

    1983-01-01

    The author is persuaded that the main purpose of the North Atlantic Treaty Organization (NATO) was to raise the confidence of moderate ruling groups in Western Europe. Today NATO is an expression of support between troubled allies with a number of common interests. (RM)

  5. North Atlantic westerlies during the last millennium

    NASA Astrophysics Data System (ADS)

    Vasskog, Kristian; Bakke, Jostein; Ringkjøb Nielsen, Pål; Meidell, Susanne

    2015-04-01

    Understanding North Atlantic decadal-scale climate variability is crucial in order to make projections of future climate change and to assess anthropogenic impacts on climate. However, reconstructing past changes in atmospheric circulation patterns from proxy data is particularly challenging, and different proxy reconstructions often show conflicting results. Winter accumulation dominates the annual mass-balance of glaciers along the west coast of Norway, and because the winter accumulation is highly sensitive to changes in the strength of wintertime westerly winds, these glaciers are potentially valuable recorders of past atmospheric circulation. Here we present a 1200-year long spatiotemporal reconstruction of Nordfonna, a maritime plateau glacier in western Norway, based on an integrated study of terrestrial moraine sequences, sub-glacial topography, and multi-proxy records from two distal glacier-fed lakes located at the opposite sides of the glacier in a west-east transect. We use temporal changes in the west-to-east tilt of the Equilibrium-Line-Altitude (ELA) across the ice cap to infer the strength of North-Atlantic westerly winds over the past 1200 years, and validate our high-resolution (5-yr) record against instrumental data. While multidecadal fluctuations in the regional ELA can be explained largely by changes in North Atlantic sea surface temperatures (i.e. the AMO), our data suggests that the local 'Little Ice Age' maximum glacier expansion (AD 1700-1750) was caused mainly by strengthened wintertime westerlies. The wintertime westerlies over southern Norway are closely linked to the leading mode of atmospheric variability in the North Atlantic, known as the North Atlantic Oscillation (NAO), and our record therefore represents a unique proxy of past changes in the NAO.

  6. Earthquakes at North Atlantic passive margins

    SciTech Connect

    Gregersen, S. ); Basham, P.W. )

    1989-01-01

    The main focus of this volume is the earthquakes that occur at and near the continental margins on both sides of the North Atlantic. The book, which contains the proceedings of the NATO workshop on Causes and Effects of Earthquakes at Passive Margins and in Areas of Postglacial Rebound on Both Sides of the North Atlantic, draws together the fields of geophysics, geology and geodesy to address the stress and strain in the Earth's crust. The resulting earthquakes produced on ancient geological fault zones and the associated seismic hazards these pose to man are also addressed. Postglacial rebound in North America and Fennoscandia is a minor source of earthquakes today, during the interglacial period, but evidence is presented to suggest that the ice sheets suppressed earthquake strain while they were in place, and released this strain as a pulse of significant earthquakes after the ice melted about 9000 years ago.

  7. A tritium budget for the North Atlantic

    NASA Astrophysics Data System (ADS)

    Doney, Scott C.; Jenkins, Wllliam J.; Östlund, H. G.

    1993-10-01

    We develop a new model bomb-3H budget for the North Atlantic between 1950 and 1986. The model, which calculates the atmospheric and continental 3H delivery as well as the advective 3H transports from the South Atlantic and Arctic, agrees within about 10% with the 3H inventories computed from the 1972 GEOSECS and the 1981-1983 Transient Tracers in the Ocean (TTO) observations. The decay-corrected 3H inventory for the North Atlantic increased by about 43% between the GEOSECS and TTO programs (1972 to 1981), and the inflow of high 3H polar water from the Arctic into the North Atlantic is found to be crucial for correctly simulating this increase. Key aspects of the model that differ from previous studies include the treatment of vapor/rain isotopic equilibrium, the continental vapor flux, and the downward flux of water vapor into the ocean. The sensitivity of the atmospheric 3H delivery to model parameters and to seasonal and interannual variability are explored.

  8. Millennial changes in North Atlantic oxygen concentrations

    NASA Astrophysics Data System (ADS)

    Hoogakker, B. A. A.; Thornalley, D. J. R.; Barker, S.

    2016-01-01

    Glacial-interglacial changes in bottom water oxygen concentrations [O2] in the deep northeast Atlantic have been linked to decreased ventilation relating to changes in ocean circulation and the biological pump (Hoogakker et al., 2015). In this paper we discuss seawater [O2] changes in relation to millennial climate oscillations in the North Atlantic over the last glacial cycle, using bottom water [O2] reconstructions from 2 cores: (1) MD95-2042 from the deep northeast Atlantic (Hoogakker et al., 2015) and (2) ODP (Ocean Drilling Program) Site 1055 from the intermediate northwest Atlantic. The deep northeast Atlantic core MD95-2042 shows decreased bottom water [O2] during millennial-scale cool events, with lowest bottom water [O2] of 170, 144, and 166 ± 17 µmol kg-1 during Heinrich ice rafting events H6, H4, and H1. Importantly, at intermediate depth core ODP Site 1055, bottom water [O2] was lower during parts of Marine Isotope Stage 4 and millennial cool events, with the lowest values of 179 and 194 µmol kg-1 recorded during millennial cool event C21 and a cool event following Dansgaard-Oeschger event 19. Our reconstructions agree with previous model simulations suggesting that glacial cold events may be associated with lower seawater [O2] across the North Atlantic below ˜ 1 km (Schmittner et al., 2007), although in our reconstructions the changes are less dramatic. The decreases in bottom water [O2] during North Atlantic Heinrich events and earlier cold events at the two sites can be linked to water mass changes in relation to ocean circulation changes and possibly productivity changes. At the intermediate depth site a possible strong North Atlantic Intermediate Water cell would preclude water mass changes as a cause for decreased bottom water [O2]. Instead, we propose that the lower bottom [O2] there can be linked to productivity changes through increased export of organic material from the surface ocean and its subsequent remineralization in the water column

  9. Two Distinct Roles of Atlantic SSTs in ENSO Variability: North Tropical Atlantic SST and Atlantic Nino

    NASA Technical Reports Server (NTRS)

    Ham, Yoo-Geun; Kug, Jong-Seong; Park, Jong-Yeon

    2013-01-01

    Two distinct roles of the Atlantic sea surface temperatures (SSTs), namely, the North Tropical Atlantic (NTA) SST and the Atlantic Nino, on the El Nino-Southern Oscillation (ENSO) variability are investigated using the observational data from 1980 to 2010 and coupled model experiments. It appears that the NTA SST and the Atlantic Nino can be used as two independent predictors for predicting the development of ENSO events in the following season. Furthermore, they are likely to be linked to different types of El Nino events. Specifically, the NTA SST cooling during February, March, and April contributes to the central Pacific warming at the subsequent winter season, while the negative Atlantic Nino event during June, July, and August contributes to enhancing the eastern Pacific warming. The coupled model experiments support these results. With the aid of a lagged inverse relationship, the statistical forecast using two Atlantic indices can successfully predict various ENSO indices.

  10. Quantification of dissolved iron sources to the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Conway, Tim M.; John, Seth G.

    2014-07-01

    Dissolved iron is an essential micronutrient for marine phytoplankton, and its availability controls patterns of primary productivity and carbon cycling throughout the oceans. The relative importance of different sources of iron to the oceans is not well known, however, and flux estimates from atmospheric dust, hydrothermal vents and oceanic sediments vary by orders of magnitude. Here we present a high-resolution transect of dissolved stable iron isotope ratios (δ56Fe) and iron concentrations ([Fe]) along a section of the North Atlantic Ocean. The different iron sources can be identified by their unique δ56Fe signatures, which persist throughout the water column. This allows us to calculate the relative contribution from dust, hydrothermal venting and reductive and non-reductive sedimentary release to the dissolved phase. We find that Saharan dust aerosol is the dominant source of dissolved iron along the section, contributing 71-87 per cent of dissolved iron. Additional sources of iron are non-reductive release from oxygenated sediments on the North American margin (10-19 per cent), reductive sedimentary dissolution on the African margin (1-4 per cent) and hydrothermal venting at the Mid-Atlantic Ridge (2-6 per cent). Our data also indicate that hydrothermal vents in the North Atlantic are a source of isotopically light iron, which travels thousands of kilometres from vent sites, potentially influencing surface productivity. Changes in the relative importance of the different iron sources through time may affect interactions between the carbon cycle and climate.

  11. Review of North Atlantic Source Waters

    NASA Technical Reports Server (NTRS)

    Swift, J. H.

    1984-01-01

    North Atlantic Deep Water (NADW) ventilates the deep World Ocean. It not only carries relatively well-oxygenated waters, but also other substances derived from recent sea-surface exchanges. There are five regional sources for NADW: (1) derivatives of the salty Mediterranean Sea outflow, (2) products of open-ocean convection in the Labrador Sea, (3) Iceland-Scotland Overflow Water from the Norwegian Sea - salty by virtue of mixing with saline water near the sills, (4) Denmark Strait Overflow Water from the Iceland and Greenland Seas - which retains a high-density, relatively low-salinity signal, and (5) remnants of deep water from the Antarctic circumpolar region - freshest of the bottom waters. Despite the differences of characteristics of the source waters, the NADW is relatively uniform. Because the formation of each of the five source waters may be viewed as a response to a complex series of events, it is difficult to examine the sensitivity of NADW to environmental fluctuations. It is known that the deep northern North Atlantic is relatively closely coupled to the sea surface in the Greenland and Iceland seas. The most recent studies indicate a minimum response time of only two years between the introduction of a passive signal north of Iceland and its appearance in the deep northwest Atlantic.

  12. Multi-model ensemble forecasting of North Atlantic tropical cyclone activity

    NASA Astrophysics Data System (ADS)

    Villarini, Gabriele; Luitel, Beda; Vecchi, Gabriel A.; Ghosh, Joyee

    2016-09-01

    North Atlantic tropical cyclones (TCs) and hurricanes are responsible for a large number of fatalities and economic damage. Skillful seasonal predictions of the North Atlantic TC activity can provide basic information critical to our improved preparedness. This study focuses on the development of statistical-dynamical seasonal forecasting systems for different quantities related to the frequency and intensity of North Atlantic TCs. These models use only tropical Atlantic and tropical mean sea surface temperatures (SSTs) to describe the variability exhibited by the observational records because they reflect the importance of both local and non-local effects on the genesis and development of TCs in the North Atlantic basin. A set of retrospective forecasts of SSTs by six experimental seasonal-to-interannual prediction systems from the North American Multi-Model Ensemble are used as covariates. The retrospective forecasts are performed over the period 1982-2015. The skill of these statistical-dynamical models is quantified for different quantities (basin-wide number of tropical storms and hurricanes, power dissipation index and accumulated cyclone energy) for forecasts initialized as early as November of the year prior to the season to forecast. The results of this work show that it is possible to obtain skillful retrospective forecasts of North Atlantic TC activity with a long lead time. Moreover, probabilistic forecasts of North Atlantic TC activity for the 2016 season are provided.

  13. North American XP-51 Mustang

    NASA Technical Reports Server (NTRS)

    1941-01-01

    North American XP-51 Mustang: This is the North American XP-51 Mustang shortly after it arrived for NACA trials in December 1941. Built as the fourth Mustang, it was diverted from RAF production for U. S. Army use. The prewar polished metal finish would soon be covered in camouflage paint. Extensive flight tests were made on this aircraft at Langley. In the past few years, this particular aircraft has been restored to flight status by the Experimental Aircraft Association, and may be seen at their museum at Oshkosh, Wisconsin.

  14. Climatology and Interannual Variability of North Atlantic Hurricane Tracks.

    NASA Astrophysics Data System (ADS)

    Xie, Lian; Yan, Tingzhuang; Pietrafesa, Leonard J.; Morrison, John M.; Karl, Thomas

    2005-12-01

    The spatial and temporal variability of North Atlantic hurricane tracks and its possible association with the annual hurricane landfall frequency along the U.S. East Coast are studied using principal component analysis (PCA) of hurricane track density function (HTDF). The results show that, in addition to the well-documented effects of the El Niño Southern Oscillation (ENSO) and vertical wind shear (VWS), North Atlantic HTDF is strongly modulated by the dipole mode (DM) of Atlantic sea surface temperature (SST) as well as the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). Specifically, it was found that Atlantic SST DM is the only index that is associated with all top three empirical orthogonal function (EOF) modes of the Atlantic HTDF. ENSO and tropical Atlantic VWS are significantly correlated with the first and the third EOF of the HTDF over the North Atlantic Ocean. The second EOF of North Atlantic HTDF, which represents the “zonal gradient” of North Atlantic hurricane track density, showed no significant correlation with ENSO or with tropical Atlantic VWS. Instead, it is associated with the Atlantic SST DM, and extratropical processes including NAO and AO. Since for a given hurricane season, the preferred hurricane track pattern, together with the overall basinwide hurricane activity, collectively determines the hurricane landfall frequency, the results provide a foundation for the construction of a statistical model that projects the annual number of hurricanes striking the eastern seaboard of the United States.

  15. Ocean Modeling of the North Atlantic

    NASA Technical Reports Server (NTRS)

    Seminar, A. J.

    1984-01-01

    Present modeling of the North Atlantic is inadequate and can be improved in a number of ways. A number of important physical processes are listed in five categories from the viewpoints of how they are treated in isolation, how they are usually represented in present ocean basin models, and how they may be better represented in future models. In the first two categories of vertical boundary processes and internal vertical mixing, parameterizations exist which can easily be incorporated into models and which will have important effects on the simulated structure of the North Atlantic. For the third catagory (mesoscale eddy effects), adequate parameterizations do not exist; but the order of magnitude of the effects is known from observational and process-model studies. A horizontal grid spacing of 100 km or less in required to allow parameterizations with this order of magnitude, as well as to resolve the time-averaged ocean fields. In the fourth category of large scale transports improvements are suggested by way of increased vertical resolution and by the requirement that lateral mixing due to eddies takes place on isopycnal surfaces. Model incorporation of the latter phenomenta is underway. In the fifth category of miscellaneous high-latitude processes, formulations for the treatment of sea ice are available for use. However, the treatment of gravitational instability, which is crucial to deepwater formation in the Atlantic Ocean, will require additional refinements to account for the unresolved physics of chimney formations in the open ocean and buoyant plumes near ocean boundaries.

  16. Decadal variability in the Eastern North Atlantic

    NASA Astrophysics Data System (ADS)

    Köllner, Manuela; Klein, Birgit; Kieke, Dagmar; Klein, Holger; Rhein, Monika; Roessler, Achim; Denker, Claudia

    2016-04-01

    The strong warming and salinification of the Eastern North Atlantic starting in the mid 1990s has been attributed to a westward contraction of the subpolar gyre and stronger inflow of waters from the subtropical gyre. Temporal changes in the shape and strength of the two gyres have been related to the major mode of atmospheric variability in the Atlantic sector, the NAO. Hydrographic conditions along the Northwest European shelf are thus the result of different processes such as variations in transports, varying relative contributions of water masses from the two gyres and property trends in the source water masses. We examine the decadal variability in the eastern North Atlantic based on Argo data from 2000-2015 and have constructed time series for four water masses (Subpolar Mode Water (SPMW), Intermediate Water (IW), upper Labrador Sea Water (uLSW) and deep Labrador Sea Water (dLSW)) at selected locations along the Northwest European shelf. Data from the Rockall Trough and the Iceland Basin are chosen to represent advective pathways in the subpolar gyre at two major branches of the North Atlantic Current towards the Nordic Seas and the Arctic Ocean. Temporal variability of subtropical waters transported northward along the eastern boundary is studied at Goban Spur around 48°N. The Argo data are extended in time with long-term hydrographic observations such as the Extended Ellet Line data and other climatological sources in the region. For the study of transport fluctuations time series from the RACE (Regional circulation and Global change) program (2012-2015) and predecessor programs have been used. These programs have monitored the subpolar gyre in the western basin and provide time series of transports and hydrographic anomalies from moored instruments at the western flank of the Mid Atlantic Ridge (MAR). First results show that the temperatures and salinities remained at high levels for the upper waters (SPMW and IW) until 2010 and have been decreasing since

  17. Late Eocene to middle Miocene (33 to 13 million years ago) vegetation and climate development on the North American Atlantic Coastal Plain (IODP Expedition 313, Site M0027)

    NASA Astrophysics Data System (ADS)

    Kotthoff, U.; Greenwood, D. R.; McCarthy, F. M. G.; Müller-Navarra, K.; Prader, S.; Hesselbo, S. P.

    2014-08-01

    C higher than today, but ∼1.5 °C lower than preceding and following phases of the Miocene. We conclude that vegetation and regional climate in the hinterland of the New Jersey shelf did not react as sensitively to Oligocene and Miocene climate changes as other regions in North America or Europe due to the moderating effects of the North Atlantic. An additional explanation for the relatively low regional temperatures reconstructed for the mid-Miocene climatic optimum could be an uplift of the Appalachian Mountains during the Miocene, which would also have influenced the catchment area of our pollen record.

  18. Whales before whaling in the North Atlantic.

    PubMed

    Roman, Joe; Palumbi, Stephen R

    2003-07-25

    It is well known that hunting dramatically reduced all baleen whale populations, yet reliable estimates of former whale abundances are elusive. Based on coalescent models for mitochondrial DNA sequence variation, the genetic diversity of North Atlantic whales suggests population sizes of approximately 240,000 humpback, 360,000 fin, and 265,000 minke whales. Estimates for fin and humpback whales are far greater than those previously calculated for prewhaling populations and 6 to 20 times higher than present-day population estimates. Such discrepancies suggest the need for a quantitative reevaluation of historical whale populations and a fundamental revision in our conception of the natural state of the oceans.

  19. Pb isotopes in surficial pelagic sediments from the North Atlantic

    SciTech Connect

    Hamelin, B.; Grousset, F. ); Sholkovitz, E.R. )

    1990-01-01

    The authors measured Pb isotopic composition and concentration in sediment samples close to the sea water interface in 6 box-cores from the NE Atlantic, 2 box-cores from the Sargasso Sea, and one from the US continental shelf. The anthropogenic Pb input to marine sediments due to the increase of Pb contamination over the ocean during the last century can be identified in all these cores. In the eastern part of the Atlantic, i.e., in regions under aeolian influence from Europe, Pb pollution can be recognized using its distinctive unradiogenic composition, clearly different from the upper-crustal values commonly found in pre-Holocene sediments. In contrast, Pb pollution in regions influenced by North American sources can be identified only in detailed concentration profiles because the American Pb pollution has an isotopic composition much closer to that of the natural detrital Pb input coming from weathering of the continental crust. Pb excess inventories are in good agreement with fluxes estimated from sediment-trap data and with the time record of Pb-contamination increase given by analyses in coral growth bands. Inventories of Pb contamination to the sediments of the Mud Patch (American shelf) are tenfold higher (84 {mu}g/cm{sup 2}) than those to Hatteras and Bermuda abyssal plains (4.3 and 2.8 {mu}g/cm{sup 2}).

  20. Conservation of North American rallids

    USGS Publications Warehouse

    Eddleman, William R.; Knopf, Fritz L.; Manley, Brooke; Reid, Frederic A.; Zembal, Richard

    1988-01-01

    The Rallidae are a diverse group in their habitat selection, yet most North American species occur in or near wetlands As a consequence, most species are subject to habitat enhancement or perturbation from waterfowl management programs. The overall effects of these management programs relative to rallid conservation have been assessed for few species, and there is a need for synthesis of such information. In the cases of some species or raves, population status is not known, and suggested directions for conservation and management are needed. Rare, endangered, or status undetermined species or races often occur in areas where related species are classified as game birds, and the effects of such hunting on rarer forms are not known. Their generally secretive nature, the endangered status of several races and populations, and continued loss of habitat and threats to present habitat, warrant an examination of the conservation status of the North American taxa in this group. In 1977, a committee of the International Association of Fish and Wildlife Agencies summarized available information on management and biology of American Coots (Fulica americana), rails, and gallinules in North America (Holliman 1977). That summary was intended to provide relatively complete information on conservation of these species, and also to provide guidance for research within the U.S. Fish and Wildlife Service's (FWS) Accelerated Research Program for Webless Migratory Shore and Upland Game Birds (ARP). Subsequently, a number of rallid studies were funded under this program. The program was eliminated in 1982, following substantial research activities on North American rallids. Since the demise of the ARP, additional research on rallids in North America has focused on an area the International Association of Fish and Wildlife Agencies report failed to cover in detail--that of endangered rallids in the U.S. and their possessions. Most of these studies have been of threatened and endangered

  1. Cenozoic climates: evidence from the North Atlantic

    SciTech Connect

    Berggren, W.A.

    1985-01-01

    Cenozoic biostratigraphy and climatology of the North Atlantic and adjacent land areas reflects the continuing fragmentation of Eurasia and concomitant changes on ocean-continent geometry. A latitudinal (zonal) Mesozoic circulation pattern evolved into a predominantly longitudinal (meridional) pattern during the Cenozoic in which the development of oceanic gateways and barriers gradually decreased the efficiency of poleward heat transfer resulting in the progressive climatic change which has taken place over the past 50 million years. Cenozoic distributional data from the North Atlantic and adjacent land areas will be reviewed from the following fields: a) terrestrial vertebrates and floras: b) marine calcareous microplankton and benthic foraminifera; c) other marine invertebrates. Available data suggests that the present climate in the northern hemisphere has resulted from a gradual, but inexorable, strengthening of latitudinal and vertical temperature gradients punctuated by several brief intervals of accelerated change. The absence of evidence for northern hemisphere polar glaciation prior to the late Neogene does not preclude seasonal cooling near the freezing point in post-Eocene time. Evidence for early Paleogene cold climates is not reflected in the fossil record.

  2. North Atlantic Climate Variability. An Oceanographers's Perspective

    NASA Astrophysics Data System (ADS)

    Visbeck, M.

    Much of the interannual to decadal variability in the North Atlantic Ocean is strongly linked to changes in the atmospheric forcing. The dominant mode of Atmospheric Variability is associated with changes in the strength and location of the westerly winds, a mode which is known as the North Atlantic Oscillation. The oceans response can be divided into three related categories. First there are changes in the upper ocean transports (Ekman transport) which directly alter the oceans heat transport (fast re- sponse) and because of changes in the planetary vorticity balance generate Rossby and Kelvin waves which then establish a new balanced state (slow response). Sec- ondly changes in the air-sea fluxes by a combination of variable atmospheric advection (wind vector) and efficiency of exchange (wind speed) perturb the upper ocean heat content. Part of that signal is then advected in regions of large mean ocean currents. Finally changes of the surface ocean density can alter the amount and type of newly formed water masses. Thus the characteristics and types of deep water vary possibly altering the rate of the ocean overturning. Specifically I will review recent findings about the oceans response to NAO forcing and the associated propagation of upper ocean heat content anomalies. I will discuss observations of decadal salinity variations in the Labrador Sea. and finally touch upon how a simple ecosystem is effected by the above.

  3. Advancing decadal-scale climate prediction in the North Atlantic sector.

    PubMed

    Keenlyside, N S; Latif, M; Jungclaus, J; Kornblueh, L; Roeckner, E

    2008-05-01

    The climate of the North Atlantic region exhibits fluctuations on decadal timescales that have large societal consequences. Prominent examples include hurricane activity in the Atlantic, and surface-temperature and rainfall variations over North America, Europe and northern Africa. Although these multidecadal variations are potentially predictable if the current state of the ocean is known, the lack of subsurface ocean observations that constrain this state has been a limiting factor for realizing the full skill potential of such predictions. Here we apply a simple approach-that uses only sea surface temperature (SST) observations-to partly overcome this difficulty and perform retrospective decadal predictions with a climate model. Skill is improved significantly relative to predictions made with incomplete knowledge of the ocean state, particularly in the North Atlantic and tropical Pacific oceans. Thus these results point towards the possibility of routine decadal climate predictions. Using this method, and by considering both internal natural climate variations and projected future anthropogenic forcing, we make the following forecast: over the next decade, the current Atlantic meridional overturning circulation will weaken to its long-term mean; moreover, North Atlantic SST and European and North American surface temperatures will cool slightly, whereas tropical Pacific SST will remain almost unchanged. Our results suggest that global surface temperature may not increase over the next decade, as natural climate variations in the North Atlantic and tropical Pacific temporarily offset the projected anthropogenic warming.

  4. Quantification of dissolved iron sources to the North Atlantic Ocean.

    PubMed

    Conway, Tim M; John, Seth G

    2014-07-10

    Dissolved iron is an essential micronutrient for marine phytoplankton, and its availability controls patterns of primary productivity and carbon cycling throughout the oceans. The relative importance of different sources of iron to the oceans is not well known, however, and flux estimates from atmospheric dust, hydrothermal vents and oceanic sediments vary by orders of magnitude. Here we present a high-resolution transect of dissolved stable iron isotope ratios (δ(56)Fe) and iron concentrations ([Fe]) along a section of the North Atlantic Ocean. The different iron sources can be identified by their unique δ(56)Fe signatures, which persist throughout the water column. This allows us to calculate the relative contribution from dust, hydrothermal venting and reductive and non-reductive sedimentary release to the dissolved phase. We find that Saharan dust aerosol is the dominant source of dissolved iron along the section, contributing 71-87 per cent of dissolved iron. Additional sources of iron are non-reductive release from oxygenated sediments on the North American margin (10-19 per cent), reductive sedimentary dissolution on the African margin (1-4 per cent) and hydrothermal venting at the Mid-Atlantic Ridge (2-6 per cent). Our data also indicate that hydrothermal vents in the North Atlantic are a source of isotopically light iron, which travels thousands of kilometres from vent sites, potentially influencing surface productivity. Changes in the relative importance of the different iron sources through time may affect interactions between the carbon cycle and climate.

  5. Decline of North Atlantic eels: a fatal synergy?

    PubMed

    Wirth, Thierry; Bernatchez, Louis

    2003-04-01

    Panmictic species pose particular problems for conservation because their welfare can be addressed effectively only on a global scale. We recently documented by means of microsatellite analysis that the European eel (Anguilla anguilla) is not panmictic but instead shows genetic isolation by distance. In this study, we extended the analysis to the American eel (A. rostrata) by applying identical analytical procedures and statistical power. Results obtained for the American eel were in sharp contrast with those obtained for the European eel: the null hypothesis of panmixia could not be rejected, and no isolation by distance was detected. This implies that the species must be managed as a single population. Using Bayesian statistics, we also found that the effective population sizes for both species were surprisingly low and that the populations had undergone severe contractions, most probably during the Wisconsinan glaciation. The apparent sensitivity of eels to climatic changes affecting the strength and position of the Gulf Stream 20,000 years ago is particularly worrying, given the effects of the ongoing global warming on the North Atlantic climate. Moreover, additional short-term stresses such as surging glass eel prizes, overfishing and lethal parasitic infections negatively affect eel population size. The fascinating transatlantic migration and life cycle of Atlantic eels is also their Achilles' heel as these negative short- and long-term effects will probably culminate in a fatal synergy if drastic conservation measures are not implemented to protect these international biological resources.

  6. Production of market-size North American strain Atlantic salmon Salmo salar in a land-based recirculation aquaculture system using freshwater

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is interest in culturing Atlantic salmon Salmo salar to market-size in land-based, closed containment systems that use recirculation aquaculture systems (RAS), as this technology often enables facilities to locate near major markets, obtain permits, exclude obligate pathogens, and/or reduce en...

  7. North American Natural Gas Markets

    SciTech Connect

    Not Available

    1989-02-01

    This report summarizes die research by an Energy Modeling Forum working group on the evolution of the North American natural gas markets between now and 2010. The group's findings are based partly on the results of a set of economic models of the natural gas industry that were run for four scenarios representing significantly different conditions: two oil price scenarios (upper and lower), a smaller total US resource base (low US resource case), and increased potential gas demand for electric generation (high US demand case). Several issues, such as the direction of regulatory policy and the size of the gas resource base, were analyzed separately without the use of models.

  8. Preformed Nitrate in the Glacial North Atlantic

    NASA Astrophysics Data System (ADS)

    Homola, K.; Spivack, A. J.; D'Hondt, S.; Estes, E. R.; Insua, T. L.; McKinley, C. C.; Murray, R. W.; Pockalny, R. A.; Robinson, R. S.; Sauvage, J.

    2015-12-01

    Atmospheric CO2 abundances are highly correlated with global temperature variations over the past 800,000 years. Consequently, understanding the feedbacks between climate and CO2 is important for predictions of future climate. Leading hypotheses to explain this feedback invoke changes in ocean biology, circulation, chemistry, and/or gas exchange rates to trap CO2 in the deep ocean, thereby reducing the greenhouse effect of CO2 in the atmosphere. To test these hypotheses, we use sediment pore water profiles of dissolved nitrate and oxygen to reconstruct paleo-preformed nitrate concentrations at two deep-water sites in the western North Atlantic (23°N 57°W, 5557 m water depth; 30°N 58°W, 5367 m water depth). Preformed nitrate increases down-core to 22.7 μM (25.6 m core depth) at the northern site, and to 28.5 μM (27.8 m core depth) at the southern site. The large preformed nitrate gradient between these sites reveals a paleo-boundary between a southern water source high in preformed nitrate and a northern water source with lower concentrations, similar to today's ocean. However, the boundary between these water masses occurs north of where their modern counterparts meet, indicating that Antarctic Bottom Water (AABW) extended farther north during the Last Glacial Maximum (LGM). In addition, the southern source had a higher preformed nitrate concentration than today's AABW (25 μM), contradicting hypotheses that nutrient utilization was more efficient in the Southern Ocean deep-water formation regions during the LGM. Comparison to our previous Pacific data reveals that the average preformed nitrate concentration of the deep ocean was slightly higher during the LGM than today. This result implies that the CO2-climate feedback was not principally due to more efficient nitrate utilization.

  9. Processes and mechanisms for the model SST biases in the North Atlantic and North Pacific: A link with the Atlantic meridional overturning circulation

    NASA Astrophysics Data System (ADS)

    Zhang, Liping; Zhao, Chuanhu

    2015-06-01

    Almost all of CMIP5 climate models show cold SST biases in the extratropical North Atlantic (ENA) and tropical North Atlantic (TNA) as well as in the North Pacific which are commonly linked with the weak simulated Atlantic meridional overturning circulation (AMOC). A weak AMOC and its associated reduced northward oceanic heat transport are associated with a cooling of the ENA Ocean, whereas the TNA cooling is attributable to both weak AMOC and surface heat flux. The cold biases in the ENA and TNA have remote impacts on the SST bias in the North Pacific. Here we use coupled ocean-atmosphere model experiments to show the mechanisms and pathways by which the ENA and TNA affect the North Pacific. The model simulations demonstrate that the cooling SST bias in the North Pacific is largely due to the remote effect of the cooling SST bias in the ENA, while the remote impact of the TNA cooling SST bias is of secondary importance. The ENA cooling bias triggers the circumglobal teleconnection via the Northern Hemisphere annular mode, producing a strengthening of the Aleutian low, an enhancement of the southward Ekman and Oyashio cold advection, and thus a cooling SST in the North Pacific. In contrast, the TNA cooling produces a surface high extending to the eastern tropical North Pacific, inducing the northeasterly wind anomalies north, northerly cross-equatorial wind anomalies, and northwesterly wind anomalies south of the equator. This C-shape wind anomaly pattern generates an SST warming in the tropical southeastern Pacific, which eventually leads to an SST warming in the tropical central and western Pacific by the wind-evaporation-SST feedback. The tropical Pacific warming in turn leads to an SST cooling in the North Pacific by the Pacific North American teleconnection pattern.

  10. Satellite Movie Shows Hurricane Cristobal Speeding Through North Atlantic

    NASA Video Gallery

    This animation of NOAA's GOES-East satellite imagery from August 26 through 29 shows Hurricane Cristobal changing into a post-tropical storm in the North Atlantic Ocean. Credit: NASA/NOAA GOES Project

  11. North Atlantic climate variability: The role of the North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

    Hurrell, James W.; Deser, Clara

    2009-08-01

    Marine ecosystems are undergoing rapid change at local and global scales. To understand these changes, including the relative roles of natural variability and anthropogenic effects, and to predict the future state of marine ecosystems requires quantitative understanding of the physics, biogeochemistry and ecology of oceanic systems at mechanistic levels. Central to this understanding is the role played by dominant patterns or "modes" of atmospheric and oceanic variability, which orchestrate coherent variations in climate over large regions with profound impacts on ecosystems. We review the spatial structure of extratropical climate variability over the Northern Hemisphere and, specifically, focus on modes of climate variability over the extratropical North Atlantic. A leading pattern of weather and climate variability over the Northern Hemisphere is the North Atlantic Oscillation (NAO). The NAO refers to a redistribution of atmospheric mass between the Arctic and the subtropical Atlantic, and swings from one phase to another producing large changes in surface air temperature, winds, storminess and precipitation over the Atlantic as well as the adjacent continents. The NAO also affects the ocean through changes in heat content, gyre circulations, mixed layer depth, salinity, high latitude deep water formation and sea ice cover. Thus, indices of the NAO have become widely used to document and understand how this mode of variability alters the structure and functioning of marine ecosystems. There is no unique way, however, to define the NAO. Several approaches are discussed including both linear (e.g., principal component analysis) and nonlinear (e.g., cluster analysis) techniques. The former, which have been most widely used, assume preferred atmospheric circulation states come in pairs, in which anomalies of opposite polarity have the same spatial structure. In contrast, nonlinear techniques search for recurrent patterns of a specific amplitude and sign. They reveal

  12. North Atlantic climate variability: The role of the North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

    Hurrell, James W.; Deser, Clara

    2010-02-01

    Marine ecosystems are undergoing rapid change at local and global scales. To understand these changes, including the relative roles of natural variability and anthropogenic effects, and to predict the future state of marine ecosystems requires quantitative understanding of the physics, biogeochemistry and ecology of oceanic systems at mechanistic levels. Central to this understanding is the role played by dominant patterns or "modes" of atmospheric and oceanic variability, which orchestrate coherent variations in climate over large regions with profound impacts on ecosystems. We review the spatial structure of extratropical climate variability over the Northern Hemisphere and, specifically, focus on modes of climate variability over the extratropical North Atlantic. A leading pattern of weather and climate variability over the Northern Hemisphere is the North Atlantic Oscillation (NAO). The NAO refers to a redistribution of atmospheric mass between the Arctic and the subtropical Atlantic, and swings from one phase to another producing large changes in surface air temperature, winds, storminess and precipitation over the Atlantic as well as the adjacent continents. The NAO also affects the ocean through changes in heat content, gyre circulations, mixed layer depth, salinity, high latitude deep water formation and sea ice cover. Thus, indices of the NAO have become widely used to document and understand how this mode of variability alters the structure and functioning of marine ecosystems. There is no unique way, however, to define the NAO. Several approaches are discussed including both linear (e.g., principal component analysis) and nonlinear (e.g., cluster analysis) techniques. The former, which have been most widely used, assume preferred atmospheric circulation states come in pairs, in which anomalies of opposite polarity have the same spatial structure. In contrast, nonlinear techniques search for recurrent patterns of a specific amplitude and sign. They reveal

  13. Phylogeography and historical ecology of the North Atlantic intertidal.

    PubMed

    Wares, J P; Cunningham, C W

    2001-12-01

    Recent glaciation covered the full extent of rocky intertidal habitat along the coasts of New England and the Canadian Maritimes. To test whether this glaciation in fact caused wholesale extinction of obligate rocky intertidal invertebrates, and thus required a recolonization from Europe, we compared American and European populations using allelic diversity and techniques adapted from coalescent theory. Mitochondrial DNA sequences were collected from amphi-Atlantic populations of three cold-temperate obligate rocky intertidal species (a barnacle, Semibalanus balanoides, and two gastropods, Nucella lapillus and Littorina obtusata) and three cold-temperate habitat generalist species (a seastar, Asterias rubens; a mussel, Mytilus edulis, and an isopod, Idotea balthica). For many of these species we were able to estimate the lineage-specific mutation rate based on trans-Arctic divergences between Pacific and Atlantic taxa. These data indicate that some obligate rocky intertidal taxa have colonized New England from European populations. However, the patterns of persistence in North America indicate that other life-history traits, including mech anisms of dispersal, may be more important for surviving dramatic environmental and climatic change. PMID:11831661

  14. Reorganization of the North Atlantic Oscillation during early Holocene deglaciation

    NASA Astrophysics Data System (ADS)

    Wassenburg, Jasper A.; Dietrich, Stephan; Fietzke, Jan; Fohlmeister, Jens; Jochum, Klaus Peter; Scholz, Denis; Richter, Detlev K.; Sabaoui, Abdellah; Spötl, Christoph; Lohmann, Gerrit; Andreae, Meinrat O.; Immenhauser, Adrian

    2016-08-01

    The North Atlantic Oscillation is the dominant atmospheric pressure mode in the North Atlantic region and affects winter temperature and precipitation in the Mediterranean, northwest Europe, Greenland, and Asia. The index that describes the sea-level pressure difference between Iceland and the Azores is correlated with a dipole precipitation pattern over northwest Europe and northwest Africa. How the North Atlantic Oscillation will develop as the Greenland ice sheet melts is unclear. A potential past analogue is the early Holocene, during which melting ice sheets around the North Atlantic freshened surface waters, affecting the strength of the meridional overturning circulation. Here we present a Holocene rainfall record from northwest Africa based on speleothem δ18O and compare it against a speleothem-based rainfall record from Europe. The two records are positively correlated during the early Holocene, followed by a shift to an anti-correlation, similar to the modern record, during the mid-Holocene. On the basis of our simulations with an Earth system model, we suggest the shift to the anti-correlation reflects a large-scale atmospheric and oceanic reorganization in response to the demise of the Laurentide ice sheet and a strong reduction of meltwater flux to the North Atlantic, pointing to a potential sensitivity of the North Atlantic Oscillation to the melting of ice sheets.

  15. Evidence for cooler European summers during periods of changing meltwater flux to the North Atlantic.

    PubMed

    Heiri, Oliver; Tinner, Willy; Lotter, André F

    2004-10-26

    We analyzed fossil chironomids (nonbiting midges) and pollen in two lake-sediment records to reconstruct and quantify Holocene summer-temperature fluctuations in the European Alps. Chironomid and pollen records indicate five centennial-scale cooling episodes during the early- and mid-Holocene. The strongest temperature declines of approximately 1 degrees C are inferred at approximately 10,700-10,500 and 8,200-7,600 calibrated 14C years B.P., whereas other temperature fluctuations are of smaller amplitude. Two forcing mechanisms have been presented recently to explain centennial-scale climate variability in Europe during the early- and mid-Holocene, both involving changes in Atlantic thermohaline circulation. In the first mechanism, changes in meltwater flux from the North American continent to the North Atlantic are responsible for changes in the Atlantic thermohaline circulation, thereby affecting circum-Atlantic climate. In the second mechanism, solar variability is the cause of Holocene climatic fluctuations, possibly triggering changes in Atlantic thermohaline overturning. Within their dating uncertainty, the two major cooling periods in the European Alps are coeval with substantial changes in the routing of North American freshwater runoff to the North Atlantic, whereas quantitatively, our climatic reconstructions show a poor agreement with available records of past solar activity. Thus, our results suggest that, during the early- and mid-Holocene, freshwater-induced Atlantic circulation changes had stronger influence on Alpine summer temperatures than solar variability and that Holocene thermohaline circulation reductions have led to summer-temperature declines of up to 1 degrees C in central Europe. PMID:15492214

  16. Evidence for cooler European summers during periods of changing meltwater flux to the North Atlantic.

    PubMed

    Heiri, Oliver; Tinner, Willy; Lotter, André F

    2004-10-26

    We analyzed fossil chironomids (nonbiting midges) and pollen in two lake-sediment records to reconstruct and quantify Holocene summer-temperature fluctuations in the European Alps. Chironomid and pollen records indicate five centennial-scale cooling episodes during the early- and mid-Holocene. The strongest temperature declines of approximately 1 degrees C are inferred at approximately 10,700-10,500 and 8,200-7,600 calibrated 14C years B.P., whereas other temperature fluctuations are of smaller amplitude. Two forcing mechanisms have been presented recently to explain centennial-scale climate variability in Europe during the early- and mid-Holocene, both involving changes in Atlantic thermohaline circulation. In the first mechanism, changes in meltwater flux from the North American continent to the North Atlantic are responsible for changes in the Atlantic thermohaline circulation, thereby affecting circum-Atlantic climate. In the second mechanism, solar variability is the cause of Holocene climatic fluctuations, possibly triggering changes in Atlantic thermohaline overturning. Within their dating uncertainty, the two major cooling periods in the European Alps are coeval with substantial changes in the routing of North American freshwater runoff to the North Atlantic, whereas quantitatively, our climatic reconstructions show a poor agreement with available records of past solar activity. Thus, our results suggest that, during the early- and mid-Holocene, freshwater-induced Atlantic circulation changes had stronger influence on Alpine summer temperatures than solar variability and that Holocene thermohaline circulation reductions have led to summer-temperature declines of up to 1 degrees C in central Europe.

  17. Evidence for cooler European summers during periods of changing meltwater flux to the North Atlantic

    PubMed Central

    Heiri, Oliver; Tinner, Willy; Lotter, André F.

    2004-01-01

    We analyzed fossil chironomids (nonbiting midges) and pollen in two lake-sediment records to reconstruct and quantify Holocene summer-temperature fluctuations in the European Alps. Chironomid and pollen records indicate five centennial-scale cooling episodes during the early- and mid-Holocene. The strongest temperature declines of ≈1°C are inferred at ≈10,700–10,500 and 8,200–7,600 calibrated 14C years B.P., whereas other temperature fluctuations are of smaller amplitude. Two forcing mechanisms have been presented recently to explain centennial-scale climate variability in Europe during the early- and mid-Holocene, both involving changes in Atlantic thermohaline circulation. In the first mechanism, changes in meltwater flux from the North American continent to the North Atlantic are responsible for changes in the Atlantic thermohaline circulation, thereby affecting circum-Atlantic climate. In the second mechanism, solar variability is the cause of Holocene climatic fluctuations, possibly triggering changes in Atlantic thermohaline overturning. Within their dating uncertainty, the two major cooling periods in the European Alps are coeval with substantial changes in the routing of North American freshwater runoff to the North Atlantic, whereas quantitatively, our climatic reconstructions show a poor agreement with available records of past solar activity. Thus, our results suggest that, during the early- and mid-Holocene, freshwater-induced Atlantic circulation changes had stronger influence on Alpine summer temperatures than solar variability and that Holocene thermohaline circulation reductions have led to summer-temperature declines of up to 1°C in central Europe. PMID:15492214

  18. "SPURS" in the North Atlantic Salinity Maximum

    NASA Astrophysics Data System (ADS)

    Schmitt, Raymond

    2014-05-01

    The North Atlantic Salinity Maximum is the world's saltiest open ocean salinity maximum and was the focus of the recent Salinity Processes Upper-ocean Regional Study (SPURS) program. SPURS was a joint venture between US, French, Irish, and Spanish investigators. Three US and two EU cruises were involved from August, 1012 - October, 2013 as well as surface moorings, glider, drifter and float deployments. Shipboard operations included underway meteorological and oceanic data, hydrographic surveys and turbulence profiling. The goal is to improve our understanding of how the salinity maximum is maintained and how it may be changing. It is formed by an excess of evaporation over precipitation and the wind-driven convergence of the subtropical gyre. Such salty areas are getting saltier with global warming (a record high SSS was observed in SPURS) and it is imperative to determine the relative roles of surface water fluxes and oceanic processes in such trends. The combination of accurate surface flux estimates with new assessments of vertical and horizontal mixing in the ocean will help elucidate the utility of ocean salinity in quantifying the changing global water cycle.

  19. North American X-15 model

    NASA Technical Reports Server (NTRS)

    1958-01-01

    A one-twentieth scale model of the X-15; originally suspended beneath the wing of a B-52 is observed by a scientist of the National Aeronautics and Space Administration (NASA) as it leaves the bomber model in tests to determine the release characteristics and drop motion of the research airplane. Caption: 'The aerodynamics of air launching the North American X-15 being investigated in the High Speed 7x10 FT Tunnel, about 1957.' Photograph and caption published in Engineer in Charge: A History of the Langley Aeronautical Laboratory, 1917-1958 by James R. Hansen (page 366). Photograph also published in Sixty Years of Aeronautical Research 1917-1977 By David A. Anderton. A NASA publication (page 49).

  20. North American sturgeon otolith morphology

    USGS Publications Warehouse

    Chalupnicki, Marc A.; Dittman, Dawn E.

    2016-01-01

    Accurate expedient species identification of deceased sturgeon (Acipenseridae) when external physical characteristic analysis is inconclusive has become a high priority due to the endangered or threatened status of sturgeon species around the world. Examination of otoliths has provided useful information to aid in population management, age and size-class analysis, understanding predator–prey interactions, and archeological research in other fish species. The relationship between otolith characteristics and sturgeon species has remained unknown. Therefore, we analyzed the shape of otoliths from the eight species of sturgeon found in North America to test the utility of otolith characteristic morphology in species identification. There were distinct differences in the size and shape of the otoliths between species of sturgeon with little shape variation among individuals of the same species. The relationship between otolith length axes was linear, and most of the variability was explained by a Log (axis + 1) transformation of the x and y axes (r2 = 0.8983) using the equation y = 0.73x + 0.0612. Images of otoliths from all eight North American species are presented to assist in the identification process.

  1. Decadal predictions of the North Atlantic CO2 uptake.

    PubMed

    Li, Hongmei; Ilyina, Tatiana; Müller, Wolfgang A; Sienz, Frank

    2016-01-01

    As a major CO2 sink, the North Atlantic, especially its subpolar gyre region, is essential for the global carbon cycle. Decadal fluctuations of CO2 uptake in the North Atlantic subpolar gyre region are associated with the evolution of the North Atlantic Oscillation, the Atlantic meridional overturning circulation, ocean mixing and sea surface temperature anomalies. While variations in the physical state of the ocean can be predicted several years in advance by initialization of Earth system models, predictability of CO2 uptake has remained unexplored. Here we investigate the predictability of CO2 uptake variations by initialization of the MPI-ESM decadal prediction system. We find large multi-year variability in oceanic CO2 uptake and demonstrate that its potential predictive skill in the western subpolar gyre region is up to 4-7 years. The predictive skill is mainly maintained in winter and is attributed to the improved physical state of the ocean. PMID:27026490

  2. Decadal predictions of the North Atlantic CO2 uptake

    PubMed Central

    Li, Hongmei; Ilyina, Tatiana; Müller, Wolfgang A.; Sienz, Frank

    2016-01-01

    As a major CO2 sink, the North Atlantic, especially its subpolar gyre region, is essential for the global carbon cycle. Decadal fluctuations of CO2 uptake in the North Atlantic subpolar gyre region are associated with the evolution of the North Atlantic Oscillation, the Atlantic meridional overturning circulation, ocean mixing and sea surface temperature anomalies. While variations in the physical state of the ocean can be predicted several years in advance by initialization of Earth system models, predictability of CO2 uptake has remained unexplored. Here we investigate the predictability of CO2 uptake variations by initialization of the MPI-ESM decadal prediction system. We find large multi-year variability in oceanic CO2 uptake and demonstrate that its potential predictive skill in the western subpolar gyre region is up to 4–7 years. The predictive skill is mainly maintained in winter and is attributed to the improved physical state of the ocean. PMID:27026490

  3. Correcting North Atlantic sea surface salinity biases in the Kiel Climate Model: influences on ocean circulation and Atlantic Multidecadal Variability

    NASA Astrophysics Data System (ADS)

    Park, T.; Park, W.; Latif, M.

    2016-10-01

    A long-standing problem in climate models is the large sea surface salinity (SSS) biases in the North Atlantic. In this study, we describe the influences of correcting these SSS biases on the circulation of the North Atlantic as well as on North Atlantic sector mean climate and decadal to multidecadal variability. We performed integrations of the Kiel Climate Model (KCM) with and without applying a freshwater flux correction over the North Atlantic. The quality of simulating the mean circulation of the North Atlantic Ocean, North Atlantic sector mean climate and decadal variability is greatly enhanced in the freshwater flux-corrected integration which, by definition, depicts relatively small North Atlantic SSS biases. In particular, a large reduction in the North Atlantic cold sea surface temperature bias is observed and a more realistic Atlantic Multidecadal Variability simulated. Improvements relative to the non-flux corrected integration also comprise a more realistic representation of deep convection sites, sea ice, gyre circulation and Atlantic Meridional Overturning Circulation. The results suggest that simulations of North Atlantic sector mean climate and decadal variability could strongly benefit from alleviating sea surface salinity biases in the North Atlantic, which may enhance the skill of decadal predictions in that region.

  4. Genetics Home Reference: North American Indian childhood cirrhosis

    MedlinePlus

    ... Health Conditions North American Indian childhood cirrhosis North American Indian childhood cirrhosis Enable Javascript to view the expand/ ... Download PDF Open All Close All Description North American Indian childhood cirrhosis is a rare liver disorder that ...

  5. 75 FR 68378 - Meeting Announcement: North American Wetlands Conservation Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-05

    ... Fish and Wildlife Service Meeting Announcement: North American Wetlands Conservation Council AGENCY: Fish and Wildlife Service, Interior. ACTION: Notice of meeting. SUMMARY: The North American Wetlands Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA)...

  6. 76 FR 31626 - Meeting Announcement; North American Wetlands Conservation Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-01

    ... Fish and Wildlife Service Meeting Announcement; North American Wetlands Conservation Council AGENCY: Fish and Wildlife Service, Interior. ACTION: Notice of meeting. SUMMARY: The North American Wetlands Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA)...

  7. 77 FR 71820 - Meeting Announcement: North American Wetlands Conservation Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-04

    ... Fish and Wildlife Service Meeting Announcement: North American Wetlands Conservation Council AGENCY: Fish and Wildlife Service, Interior. ACTION: Notice of meeting. SUMMARY: The North American Wetlands Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA)...

  8. 78 FR 71637 - Meeting Announcement: North American Wetlands Conservation Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-29

    ... Fish and Wildlife Service Meeting Announcement: North American Wetlands Conservation Council AGENCY: Fish and Wildlife Service, Interior. ACTION: Notice of meeting. SUMMARY: The North American Wetlands Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA)...

  9. 77 FR 39252 - Meeting Announcement: North American Wetlands Conservation Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-02

    ... Fish and Wildlife Service Meeting Announcement: North American Wetlands Conservation Council AGENCY: Fish and Wildlife Service, Interior. ACTION: Notice of meetings. SUMMARY: The North American Wetlands Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA)...

  10. 76 FR 69278 - Meeting Announcement: North American Wetlands Conservation Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-08

    ... Fish and Wildlife Service Meeting Announcement: North American Wetlands Conservation Council AGENCY: Fish and Wildlife Service, Interior. ACTION: Notice of meeting. SUMMARY: The North American Wetlands Conservation Council will meet to select North American Wetlands Conservation Act grant proposals...

  11. 78 FR 11220 - Meeting Announcement: North American Wetlands Conservation Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-15

    ... Fish and Wildlife Service Meeting Announcement: North American Wetlands Conservation Council AGENCY: Fish and Wildlife Service, Interior. ACTION: Notice of meeting. SUMMARY: The North American Wetlands Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA)...

  12. 75 FR 34479 - Meeting Announcement: North American Wetlands Conservation Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-17

    ... Fish and Wildlife Service Meeting Announcement: North American Wetlands Conservation Council AGENCY: Fish and Wildlife Service, Interior. ACTION: Notice of meeting. SUMMARY: The North American Wetlands Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA)...

  13. Total Dissolved Cobalt and Labile Cobalt in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Saito, M. A.; Noble, A.

    2012-12-01

    This study presents the total and labile dissolved cobalt distributions from the North Atlantic GEOTRACES Zonal Transect expeditions of the fall of 2010 and 2011. Labile cobalt was detected in much of the water column below the euphotic zone, suggesting that strong cobalt binding ligands were not present in excess of the total cobalt concentration. Near complete complexation of cobalt was observed in surface waters, and linear relationships were observed when both total and labile cobalt were compared to phosphate in surface waters, indicative of a strong biological influence on cobalt cycling. Decoupling of cobalt and macronutrients in the surface waters was observed approaching the North American coast, and a relationship between cobalt and salinity was observed, suggesting that coastal inputs may dominate the distributions of cobalt there. In deep waters, both total and labile cobalt were generally lower in concentration than at intermediate depths, which is evidence of scavenging processes removing cobalt from the water column. Elevated concentrations of labile and total cobalt were observed in samples taken within the TAG hydrothermal plume, and a reverse relationship between cobalt and oxygen was observed in the western basin OMZ.

  14. North American ultra-distal tephrochronology

    NASA Astrophysics Data System (ADS)

    Pyne-O'Donnell, S.; Hughes, P.; Mallon, G.; Amesbury, M.; Charman, D.; Street-Perrott, A.; Loader, N.; Woodman-Ralph, J.; Mauquoy, D.; Daley, T.; Booth, R.

    2011-12-01

    PRECIP (Palaeo-REconstruction of ocean-atmosphere Coupling In Peat) is a multi-proxy project examining the influences of Gulf Stream and Labrador Current variations on Holocene raised bogs along the Atlantic seaboard of North America. The project aims to reconstruct the influences of such climate drivers at multi-decadal timescales, thus enabling the testing of hypotheses relating to ocean-atmosphere coupling of Thermohaline Circulation (THC) and terrestrial responses (e.g. the '8.2 ka' event). A valuable geochronological tool for this task is tephrochronology which utilises far-travelled volcanic ash (microtephra: < ca.100 μm) as precise synchronous horizons or isochrons between depositional archives. One project site (Nordan's Pond Bog, Newfoundland) has been found to contain up to 12 rhyolitic microtephra layers throughout a continuous ca. 9000-year profile. The nearest volcanic sources are Iceland and Jan Mayan, ca. 2500 km to the north-east of Newfoundland. However, geochemical analysis reveals that the ash isochrons have little affinity with these sources and are instead primarily of North American provenance transported by Westerlies from Alaska and the Pacific Mountain System ca. 5000 km to the west. Two layers of particularly high shard concentration (> 600 shards/cm3) are estimated by the age model to occur at ca. 7500 14C cal. yrs BP and ca. 1200 14C cal. yrs BP (ca. AD 800), and are the correct period and geochemistry for correlation with the widespread Mazama Ash (Crater Lake, Oregon) (7627±150 Greenland GISP2 ice core yrs BP) and White River Ash (Mount Churchill, Alaska) eruptions respectively. Other sources for prominent sequence isochrons are Mount St Helens (Washington), Mount Augustine (Alaska) and Mount Aniakchak (Alaska). The tephrochronological potential of other sites in the region is anticipated to be just as promising and should therefore provide the opportunity for the development of a new Holocene tephrostratigraphic framework for north

  15. Array Analysis of North Atlantic Microseisms

    NASA Astrophysics Data System (ADS)

    Craig, David; Bean, Chris; Möllhoff, Martin; Donne, Sarah; Lokmer, Ivan; Le Pape, Florian

    2016-04-01

    Oceans generate persistent low frequency background seismic signals known as microseisms through a mechanical coupling with the Earth's crust. Microseism energy originates as regions of low barometric pressure (depressions) over the oceans where it is transmitted to the sea-floor and propagates as elastic energy in the Earths crust. Consequently microseisms carry important meteorological information relating to both the atmosphere and the hydrosphere. The significance of microseisms as climate indicators has previously been investigated in several studies (Essen et al., 1999; Aster et al., 2010) and to estimate ocean wave parameters using onshore seismometer data (Bromirski et al., 1999). Also many modern seismological methods make use of microseism signals, for example "noise tomography" (Shapiro et al., 2005); spectral ratio techniques ; and cross-correlation techniques (Wapenaar et al., 2011; Brenguier et al., 2014). The continental shelf near Ireland is a known generation are for microseisms and an important region for European weather forecasting and climate studies. There has also been seismometers in the region since the 1960s. There is a single station in Valentia observatory in south-west Ireland and a small scale seismic array in Scotland which offer potential climate records for the region. To make use of this information it is first necessary to understand how microseisms recorded in Ireland relate to the local ocean wavefield. The WAVEOBS project was set established with three primary goals; to get a better fundamental understanding of microseism sources; to investigate the use of ocean generated microseisms as real time ocean wave height data; and to investigate their use as a climate proxy. Using spectral analysis and array methods the microseism wavefield in the North-East Atlantic near Ireland is described with reference to the ocean wavefield.

  16. Holocene dynamics of North Atlantic Deep Water Masses

    NASA Astrophysics Data System (ADS)

    Hoogakker, B.; Chapman, M.; McCave, I. N.; Hillaire-Marcel, C.

    2012-12-01

    The Atlantic Meridional Overturning Circulation (AMOC) is a key component in latitudinal heat and salt transport, comprising northward flow of salty warm near-surface waters in the North Atlantic Current, and its compensating cool return flow at depth. During the early Holocene high summer insolation and strong inflow of North Atlantic surface waters into the Nordic Seas and the Arctic Ocean may have contributed to increased deep-water formation. To assess the effect of increased deep-water formation in the Nordic Seas and the Arctic Ocean on AMOC we reconstructed and assessed bottom flow vigour (using the mean grain size of the sortable silt) and hydrographic properties (using benthic foraminiferal isotopes) at key locations in the deep North Atlantic. The core sites of MD99-2251 and ODP 980 are currently influenced by North East Atlantic Deep Water (NEADW-origin Iceland Scotland Overflow Water), whilst that of MD95-2024 is under the influence of North West Atlantic Bottom Water (NWABW-currently densest North Atlantic Deep Water mass, origin Denmark Strait Overflow). When exiting the Labrador Sea, NEADW and NWABW mix to make up Lower North Atlantic Deep Water. Our results show that NEADW at Gardar Drift in the northeast Atlantic was considerably enhanced and denser (comparable to NWABW) during the early Holocene, until ~6.5 ka. The density increase is attributed to NEADW mainly consisting of Iceland Scotland Overflow Water, lacking significant contributions of Labrador Sea Water or Lower Deep Water (LDW-origin Antarctic Bottom Water) that it contains at present. This implies there was no density gradient between these two deep-water masses during the early Holocene, contrary to today. A subsequent weakening of NEADW accompanied with a reduction in its density after 6.5 ka allowed a shoaling of LDW and deeper eastward advection of Labrador Sea Water into the northeast Atlantic basin. The density gradient observed between current NEADW and NWABW might have been

  17. Dissolved Organic Carbon in the North Atlantic Meridional Overturning Circulation

    PubMed Central

    Fontela, Marcos; García-Ibáñez, Maribel I.; Hansell, Dennis A.; Mercier, Herlé; Pérez, Fiz F.

    2016-01-01

    The quantitative role of the Atlantic Meridional Overturning Circulation (AMOC) in dissolved organic carbon (DOC) export is evaluated by combining DOC measurements with observed water mass transports. In the eastern subpolar North Atlantic, both upper and lower limbs of the AMOC transport high-DOC waters. Deep water formation that connects the two limbs of the AMOC results in a high downward export of non-refractory DOC (197 Tg-C·yr−1). Subsequent remineralization in the lower limb of the AMOC, between subpolar and subtropical latitudes, consumes 72% of the DOC exported by the whole Atlantic Ocean. The contribution of DOC to the carbon sequestration in the North Atlantic Ocean (62 Tg-C·yr−1) is considerable and represents almost a third of the atmospheric CO2 uptake in the region. PMID:27240625

  18. North American tidal power prospects

    NASA Astrophysics Data System (ADS)

    Wayne, W. W., Jr.

    1981-07-01

    Prospects for North American tidal power electrical generation are reviewed. Studies by the US Army Corps of Engineers of 90 possible generation schemes in Cobscook Bay, ME, indicated that maximum power generation rather than dependable capacity was the most economic method. Construction cost estimates for 15 MW bulb units in a single effect mode from basin to the sea are provided; five projects were considered ranging from 110-160 MW. Additional tidal power installations are examined for: Half-Moon Cove, ME (12 MW, 18 ft tide); Cook Inlet, AK, which is shown to pose severe environmental and engineering problems due to fish migration, earthquake hazards, and 300 ft deep silt deposits; and the Bay of Fundy, Canada. This last has a 17.8 MW plant under construction in a 29 ft maximum tide area. Other tidal projects of the Maritime Provinces are reviewed, and it is noted that previous economic evaluations based on an oil price of $16/barrel are in need of revision.

  19. North Atlantic Deep Water Production during the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Howe, Jacob N. W.; Piotrowski, Alexander M.; Noble, Taryn L.; Mulitza, Stefan; Chiessi, Cristiano M.; Bayon, Germain

    2016-06-01

    Changes in deep ocean ventilation are commonly invoked as the primary cause of lower glacial atmospheric CO2. The water mass structure of the glacial deep Atlantic Ocean and the mechanism by which it may have sequestered carbon remain elusive. Here we present neodymium isotope measurements from cores throughout the Atlantic that reveal glacial-interglacial changes in water mass distributions. These results demonstrate the sustained production of North Atlantic Deep Water under glacial conditions, indicating that southern-sourced waters were not as spatially extensive during the Last Glacial Maximum as previously believed. We demonstrate that the depleted glacial δ13C values in the deep Atlantic Ocean cannot be explained solely by water mass source changes. A greater amount of respired carbon, therefore, must have been stored in the abyssal Atlantic during the Last Glacial Maximum. We infer that this was achieved by a sluggish deep overturning cell, comprised of well-mixed northern- and southern-sourced waters.

  20. North Atlantic Deep Water Production during the Last Glacial Maximum.

    PubMed

    Howe, Jacob N W; Piotrowski, Alexander M; Noble, Taryn L; Mulitza, Stefan; Chiessi, Cristiano M; Bayon, Germain

    2016-01-01

    Changes in deep ocean ventilation are commonly invoked as the primary cause of lower glacial atmospheric CO2. The water mass structure of the glacial deep Atlantic Ocean and the mechanism by which it may have sequestered carbon remain elusive. Here we present neodymium isotope measurements from cores throughout the Atlantic that reveal glacial-interglacial changes in water mass distributions. These results demonstrate the sustained production of North Atlantic Deep Water under glacial conditions, indicating that southern-sourced waters were not as spatially extensive during the Last Glacial Maximum as previously believed. We demonstrate that the depleted glacial δ(13)C values in the deep Atlantic Ocean cannot be explained solely by water mass source changes. A greater amount of respired carbon, therefore, must have been stored in the abyssal Atlantic during the Last Glacial Maximum. We infer that this was achieved by a sluggish deep overturning cell, comprised of well-mixed northern- and southern-sourced waters. PMID:27256826

  1. North Atlantic Deep Water Production during the Last Glacial Maximum

    PubMed Central

    Howe, Jacob N. W.; Piotrowski, Alexander M.; Noble, Taryn L.; Mulitza, Stefan; Chiessi, Cristiano M.; Bayon, Germain

    2016-01-01

    Changes in deep ocean ventilation are commonly invoked as the primary cause of lower glacial atmospheric CO2. The water mass structure of the glacial deep Atlantic Ocean and the mechanism by which it may have sequestered carbon remain elusive. Here we present neodymium isotope measurements from cores throughout the Atlantic that reveal glacial–interglacial changes in water mass distributions. These results demonstrate the sustained production of North Atlantic Deep Water under glacial conditions, indicating that southern-sourced waters were not as spatially extensive during the Last Glacial Maximum as previously believed. We demonstrate that the depleted glacial δ13C values in the deep Atlantic Ocean cannot be explained solely by water mass source changes. A greater amount of respired carbon, therefore, must have been stored in the abyssal Atlantic during the Last Glacial Maximum. We infer that this was achieved by a sluggish deep overturning cell, comprised of well-mixed northern- and southern-sourced waters. PMID:27256826

  2. Vegetation and climate development on the North American Atlantic Coastal Plain from 33 to 13 million years ago (IODP Expedition 313)

    NASA Astrophysics Data System (ADS)

    Kotthoff, U.; Greenwood, D. R.; McCarthy, F. M. G.; Müller-Navarra, K.; Hesselbo, S. P.

    2013-12-01

    We have investigated the palynology of sediment cores from Sites M0027 and M0029 of IODP Expedition 313 on the New Jersey shallow shelf, east coast of North America, spanning an age range of 33 to 13 million years before present. Additionally, a pollen assemblage from the Pleistocene was examined. The palynological results were statistically analyzed and complemented with pollen-based quantitative climate reconstructions. Transport-related bias of the pollen assemblages was identified via analysis of the ratio of terrestrial to marine palynomorphs, and considered when interpreting palaeovegetation and palaeoclimate from the pollen data. Results indicate that from the early Oligocene to the middle Miocene, the hinterland vegetation of the New Jersey shelf was characterized by oak-hickory forests in the lowlands and conifer-dominated vegetation in the highlands. The Oligocene witnessed several expansions of conifer forest, probably related to cooling events. The pollen-based climate data imply an increase in annual temperatures from ~12 °C to more than 15 °C during the Oligocene. The Mi-1 cooling event at the onset of the Miocene is reflected by an expansion of conifers and an annual temperature decrease by almost 3 °C, from 15 °C to 12.5 °C around 23 million years before present. Particularly low annual temperatures are also recorded for an interval around ~20 million years before present, which probably reflects the Mi-1aa cooling event. Generally, the Miocene ecosystem and climate conditions were very similar to those of the Oligocene in the hinterland of the New Jersey shelf. Miocene grasslands, as known from other areas in the USA during that time period, are not evident for the hinterland of the New Jersey shelf. Surprisingly, the palaeovegetation data for the hinterland of the New Jersey shelf do not show extraordinary changes during the Mid-Miocene climatic optimum at ~15 million years before present, except for a minor increase in deciduous

  3. Changes in North Atlantic nitrogen fixation controlled by ocean circulation.

    PubMed

    Straub, Marietta; Sigman, Daniel M; Ren, Haojia; Martínez-García, Alfredo; Meckler, A Nele; Hain, Mathis P; Haug, Gerald H

    2013-09-12

    In the ocean, the chemical forms of nitrogen that are readily available for biological use (known collectively as 'fixed' nitrogen) fuel the global phytoplankton productivity that exports carbon to the deep ocean. Accordingly, variation in the oceanic fixed nitrogen reservoir has been proposed as a cause of glacial-interglacial changes in atmospheric carbon dioxide concentration. Marine nitrogen fixation, which produces most of the ocean's fixed nitrogen, is thought to be affected by multiple factors, including ocean temperature and the availability of iron and phosphorus. Here we reconstruct changes in North Atlantic nitrogen fixation over the past 160,000 years from the shell-bound nitrogen isotope ratio ((15)N/(14)N) of planktonic foraminifera in Caribbean Sea sediments. The observed changes cannot be explained by reconstructed changes in temperature, the supply of (iron-bearing) dust or water column denitrification. We identify a strong, roughly 23,000-year cycle in nitrogen fixation and suggest that it is a response to orbitally driven changes in equatorial Atlantic upwelling, which imports 'excess' phosphorus (phosphorus in stoichiometric excess of fixed nitrogen) into the tropical North Atlantic surface. In addition, we find that nitrogen fixation was reduced during glacial stages 6 and 4, when North Atlantic Deep Water had shoaled to become glacial North Atlantic intermediate water, which isolated the Atlantic thermocline from excess phosphorus-rich mid-depth waters that today enter from the Southern Ocean. Although modern studies have yielded diverse views of the controls on nitrogen fixation, our palaeobiogeochemical data suggest that excess phosphorus is the master variable in the North Atlantic Ocean and indicate that the variations in its supply over the most recent glacial cycle were dominated by the response of regional ocean circulation to the orbital cycles.

  4. A peak and decline in North Atlantic CO2 uptake

    NASA Astrophysics Data System (ADS)

    Halloran, Paul; Lebehot, Alice; Watson, Andy; McNeall, Doug; Schuster, Ute; Voelker, Christoph; Booth, Ben; Totterdell, Ian; Jones, Chris; Lambert, Hugo

    2016-04-01

    The oceans play a vital role in mitigating climate change by removing anthropogenic CO2 from the atmosphere. Presently, only around half of human-emitted CO2 remains in the atmosphere, with the rest being taken up by the land and ocean carbon sinks in approximately equal proportions. Of the ocean's CO2 uptake, that occurring in that high-latitude North Atlantic is the most intense. We develop a theoretical framework which proposes that Subpolar North Atlantic CO2 uptake is likely to peak and decline within the coming century. Considering the CMIP5 models within this framework, and comparing their behaviour to observations, we find that the CMIP5 models underestimate how close the real world's Subpolar North Atlantic CO2 uptake is to reaching peak uptake.

  5. Natural and anthropogenic forcing of North Atlantic tropical cyclone track position since 1550 A.D.

    NASA Astrophysics Data System (ADS)

    Baldini, Lisa; Baldini, James; McElwaine, Jim; Frappier, Amy; Asmerom, Yemane; Liu, Kam-biu; Prufer, Keith; Ridley, Harriet; Polyak, Victor; Kennett, Douglas; Macpherson, Colin; Aquino, Valorie; Awe, Jamie; Breitenbach, Sebastian

    2016-04-01

    Over the last 30 years, North Atlantic tropical cyclones (TC) have increased in frequency, intensity, and duration in response to rising North Atlantic sea surface temperatures (SST). Here we present a 450-year record of western Caribbean TC activity reconstructed using subannually-resolved carbon and oxygen isotope ratios in a stalagmite from Yok Balum Cave, southern Belize. Western Caribbean TC activity peaked at 1650 A.D. coincident with maximum Little Ice Age cooling and decreased gradually to 1983 A.D. (the end of the record). Comparison with existing basin-wide reconstructions reveals that the dominant TC tracks corridor migrated from the western Caribbean toward the North American east coast through time. A close link with Atlantic Multidecadal Oscillation (AMO) exists throughout the record but with a clear polarity shift in the TC-AMO relationship at 1870 A.D., coincident with industrialisation. We suggest that the cause of this reversal is Greenhouse gas and aerosol emission induced changes in the relationship between the Intertropical Convergence Zone and the Bermuda High between the modern warm period and the Pre-Industrial Era. The likely impact of continued anthropogenic forcing of TC track on population centres of the western North Atlantic and Caribbean will be addressed.

  6. Spatial and temporal evolution of lead isotope ratios in the North Atlantic Ocean between 1981 and 1989

    NASA Astrophysics Data System (ADS)

    Weiss, Dominik; Boyle, Edward A.; Wu, Jingfeng; Chavagnac, ValéRie; Michel, Anna; Reuer, Matthew K.

    2003-10-01

    Lead concentrations and isotope ratios were measured in North Atlantic surface water samples collected in 1981 (29°-79°N, 6°E-49°W) and in 1989 (23°-39°N, 29°-68°W). In the early 1980s, 206Pb/207Pb ratios in the North African Basin averaged 1.193 ± 0.005 (1 σ). Similar radiogenic ratios within the level of analytical precision (average 0.29%) were found in the Labrador and Iceland Basins (1.198 ± 0.006) and in the Norwegian Sea (1.196 ± 0.008). These radiogenic mixed layer signatures along with atmospheric global lead emission patterns suggest that most North Atlantic lead in the early 1980s was derived from North American leaded gasoline. Samples in the East Iberian Basin near Portugal and France showed lower 206Pb/207Pb ratios, between 1.167 and 1.182, indicating a significant influence of less radiogenic atmospheric lead transported from Europe and possibly the influence of the Rio Tinto acid mine drainage very close to shore in the Gulf of Cadiz. [Pb] across the entire North Atlantic Basin ranged between 54 and 145 pmol/kg, with the lowest values (54-74 pmol/kg) found at high latitudes (>65°N). In the late 1980s, surface waters in the western subtropical North Atlantic (North American Basin/Sargasso Sea, >47°W) and in the eastern subtropical North Atlantic (North African Basin/Central Iberian Basin, <45°W) showed very similar 206Pb/207Pb signatures with little zonal variation, ranging from 1.177 to 1.192. Lead concentrations ranged between 47 and 137 pmol/kg, increasing slightly from west to east. South of 25°N in the equatorial North Atlantic, crossing the subtropical/tropical surface water boundary, the 206Pb/207Pb seawater signatures were significantly less radiogenic (1.170-1.175) and concentrations were lower (≤51 pmol/kg). This difference suggests a relative increase in the atmospheric lead supply from the western Mediterranean/North African continent via Trade Easterlies and illustrates the effective barrier between the subtropical

  7. Teaching Atlantic Studies in American High Schools.

    ERIC Educational Resources Information Center

    Foster, Charles R.

    1980-01-01

    Stresses the importance of Atlantic studies within the framework of United States history, European history, and the contemporary world scene. Ways of integrating Atlantic studies into the high school social studies curriculum are suggested. Topics discussed include objectives, audiovisual aids, supplementary reading material, and global political…

  8. North Atlantic summer to winter rainfall response to the Atlantic-Pacific tropical connection

    NASA Astrophysics Data System (ADS)

    Rodríguez-Fonseca, Belen; Losada Doval, Teresa; Mohino Harris, Elsa; Polo Sánchez, Irene; Garcia Serrano, Javier

    2010-05-01

    Recent observational and GCM studies have shown, following the results of Polo et al. (2008), how the Atlantic and Pacific Niños present a dynamical link during the last decades of the XX century (Rodriguez-Fonseca et al., 2009). In this way, the positive (negative) phase of the summer Pacific Niño signal has been found to be connected with a negative (positive) phase of the Equatorial Atlantic mode (EM or Atlantic Niño, Polo et al., 2008); a pattern which leads the summer Atlantic variability. The determinant impact of this connection on the WA monsoon has been addressed by defining a global summer tropical mode accounting for more than the 60% of the rainfall variance. The rainfall response to an isolated Pacific forcing has been documented to be a decrease of rainfall over Sahel whilst, the response associated to an isolated EM is a Guinean-Sahel rainfall dipolar pattern. Nevertheless, the rainfall response to the Pacific ENSO- Atlantic Niña forcing observed from the 70's has a unified behavior in the WA region. In order to deeply analyse the dynamics involved in the concomitant action of the Atlantic and Pacific in summer and in the subsequent months, different sensitivity experiments have been performed separating the global Atlantic-IndoPacific contribution to the independent Pacific and Atlantic ones. Some dynamical aspects in relation to the extratropical North Atlantic teleconnections in the following seasons are also included.

  9. THE RESPONSE OF MARINE ECOSYSTEMS TO CLIMATE VARIABILITY ASSOCIATED WITH THE NORTH ATLANTIC OSCILLATION

    EPA Science Inventory

    A strong association is documented between variability of the North Atlantic Oscillation (NAO) and changes in various trophic levels of the marine ecosystems of the North Atlantic. Examples are presented for phytoplankton, zooplankton, benthos, fish, marine diseases, whales and s...

  10. Recent changes in the North Atlantic.

    PubMed

    Dickson, Robert R; Curry, Ruth; Yashayaev, Igor

    2003-09-15

    It has long been recognized that the Atlantic meridional overturning circulation (MOC) is potentially sensitive to greenhouse-gas and other climate forcing, and that changes in the MOC have the potential to cause abrupt climate change. However, the mechanisms remain poorly understood and our ability to detect these changes remains incomplete. Four main (interrelated) types of ocean change in particular are associated in the literature with greenhouse-gas forcing. These are: a slowing of MOC overturning rate; changes in northern seas which might effect a change in Atlantic overturning, including changes in the freshwater flux from the Arctic, and changes in the transport and/or hydrographic character of the northern overflows which ventilate the deep Atlantic; a change in the trans-ocean gradients of steric height (both zonal and meridional) which might accompany a change in the MOC; and an intensification of the global water cycle. Though as yet we have no direct measure of the freshwater flux passing from the Arctic to the Atlantic either via the Canadian Arctic Archipelago or along the East Greenland Shelf, and no direct measure yet of the Atlantic overturning rate, we examine a wide range of time-series from the existing hydrographic record for oceanic evidence of the other anticipated responses. Large amplitude and sustained changes are found (or indicated by proxy) over the past three to four decades in the southward transport of fresh waters along the Labrador shelf and slope, in the hydrography of the deep dense overflows from Nordic seas, in the transport of the eastern overflow through Faroe Bank Channel, and in the global hydrologic cycle. Though the type and scale of changes in ocean salinity are consistent with an amplification of the water cycle, we find no convincing evidence of any significant, concerted slowdown in the Atlantic overturning circulation.

  11. North American Journal of Psychology, 2003.

    ERIC Educational Resources Information Center

    McCutcheon, Lynn E., Ed.

    2003-01-01

    "North American Journal of Psychology" publishes scientific papers of general interest to psychologists and other social scientists. Articles included in volume 5 issue 1 (March 2003) are: "Mothers' Attributional Style for Events in Their Offsprings' Lives as Predictors of Their Offsprings' Cognitive Vulnerability to Depression"; "American High…

  12. Atlantic meridional overturning circulation and the prediction of North Atlantic sea surface temperature

    NASA Astrophysics Data System (ADS)

    Klöwer, M.; Latif, M.; Ding, H.; Greatbatch, R. J.; Park, W.

    2014-11-01

    The Atlantic Meridional Overturning Circulation (AMOC), a major current system in the Atlantic Ocean, is thought to be an important driver of climate variability, both regionally and globally and on a large range of time scales from decadal to centennial and even longer. Measurements to monitor the AMOC strength have only started in 2004, which is too short to investigate its link to long-term climate variability. Here the surface heat flux-driven part of the AMOC during 1900-2010 is reconstructed from the history of the North Atlantic Oscillation, the most energetic mode of internal atmospheric variability in the Atlantic sector. The decadal variations of the AMOC obtained in that way are shown to precede the observed decadal variations in basin-wide North Atlantic sea surface temperature (SST), known as the Atlantic Multidecadal Oscillation (AMO) which strongly impacts societally important quantities such as Atlantic hurricane activity and Sahel rainfall. The future evolution of the AMO is forecast using the AMOC reconstructed up to 2010. The present warm phase of the AMO is predicted to continue until the end of the next decade, but with a negative tendency.

  13. Variability of the North Atlantic Current over the Common Era

    NASA Astrophysics Data System (ADS)

    Moffa Sanchez, P.; Hall, I. R.; Born, A.; Thornalley, D. J.; Barker, S.; Richter, T.

    2014-12-01

    Over the last 2000 years, the climate of the North Atlantic region was punctuated by centennial oscillations, which despite their small magnitude had important societal impacts, particularly in NW Europe. The most favoured explanations for this climate variability invoke changes in external forcings (such as solar activity and explosive volcanism) amplified by ocean and atmosphere feedbacks, mainly involving the Atlantic Meridional Overturning Circulation (AMOC) and the North Atlantic Oscillation. However, the scarcity of highly resolved archives has hampered our understanding of the involvement of the ocean-atmosphere interactions in these climatic oscillations. We present a subdecadally resolved temperature and salinity record derived from paired Mg/Ca-δ18O measurements on planktonic foraminifera from a marine sediment core located in the pathway of the North Atlantic Current. Our findings show a strong centennial co-variability of the temperature and salinity of the surface limb of the AMOC with solar irradiance (Moffa-Sánchez et al. 2014- NGS). Climate model results from this study show a similar correlation over the last millennium and we infer that the hydrographic changes were linked to the strength of the subpolar gyre associated with changes in atmospheric circulation. Specifically, in the simulation, low solar irradiance promotes the development of frequent and persistent atmospheric blocking events, in which a quasi-stationary high-pressure system in the eastern North Atlantic, also known as blocking event, modifies the flow of the westerly winds. To further explore the response of the upper limb of the AMOC to solar forcing found in Moffa-Sánchez et al. 14, we synthesize new and available proxy-data from the North Atlantic Current in combination with analysis from CMIP5 simulations of the last millennium.

  14. Icebergs not the trigger for North Atlantic cold events.

    PubMed

    Barker, Stephen; Chen, James; Gong, Xun; Jonkers, Lukas; Knorr, Gregor; Thornalley, David

    2015-04-16

    Abrupt climate change is a ubiquitous feature of the Late Pleistocene epoch. In particular, the sequence of Dansgaard-Oeschger events (repeated transitions between warm interstadial and cold stadial conditions), as recorded by ice cores in Greenland, are thought to be linked to changes in the mode of overturning circulation in the Atlantic Ocean. Moreover, the observed correspondence between North Atlantic cold events and increased iceberg calving and dispersal from ice sheets surrounding the North Atlantic has inspired many ocean and climate modelling studies that make use of freshwater forcing scenarios to simulate abrupt change across the North Atlantic region and beyond. On the other hand, previous studies identified an apparent lag between North Atlantic cooling events and the appearance of ice-rafted debris over the last glacial cycle, leading to the hypothesis that iceberg discharge may be a consequence of stadial conditions rather than the cause. Here we further establish this relationship and demonstrate a systematic delay between pronounced surface cooling and the arrival of ice-rafted debris at a site southwest of Iceland over the past four glacial cycles, implying that in general icebergs arrived too late to have triggered cooling. Instead we suggest that--on the basis of our comparisons of ice-rafted debris and polar planktonic foraminifera--abrupt transitions to stadial conditions should be considered as a nonlinear response to more gradual cooling across the North Atlantic. Although the freshwater derived from melting icebergs may provide a positive feedback for enhancing and or prolonging stadial conditions, it does not trigger northern stadial events. PMID:25877202

  15. Atlantic Deep-water Response to the Early Pliocene Shoaling of the Central American Seaway

    PubMed Central

    Bell, David B.; Jung, Simon J. A.; Kroon, Dick; Hodell, David A.; Lourens, Lucas J.; Raymo, Maureen E.

    2015-01-01

    The early Pliocene shoaling of the Central American Seaway (CAS), ~4.7–4.2 million years ago (mega annum-Ma), is thought to have strengthened Atlantic Meridional Overturning Circulation (AMOC). The associated increase in northward flux of heat and moisture may have significantly influenced the evolution of Pliocene climate. While some evidence for the predicted increase in North Atlantic Deep Water (NADW) formation exists in the Caribbean and Western Atlantic, similar evidence is missing in the wider Atlantic. Here, we present stable carbon (δ13C) and oxygen (δ18O) isotope records from the Southeast Atlantic-a key region for monitoring the southern extent of NADW. Using these data, together with other δ13C and δ18O records from the Atlantic, we assess the impact of the early Pliocene CAS shoaling phase on deep-water circulation. We find that NADW formation was vigorous prior to 4.7 Ma and showed limited subsequent change. Hence, the overall structure of the deep Atlantic was largely unaffected by the early Pliocene CAS shoaling, corroborating other evidence that indicates larger changes in NADW resulted from earlier and deeper shoaling phases. This finding implies that the early Pliocene shoaling of the CAS had no profound impact on the evolution of climate. PMID:26193070

  16. Reconstruction of the North Atlantic tropical cyclones in Azores for the last 800 years.

    NASA Astrophysics Data System (ADS)

    Rubio-Ingles, Maria Jesus; Sánchez, Guiomar; Trigo, Ricardo; Francus, Pierre; Gonçalves, Vitor; Raposeiro, Pedro; Freitas, Conceiçao; Borges, Paolo; Hernández, Armand; Bao, Roberto; Vázquez-Loureiro, David; Andrade, Cesar; Sáez, Alberto; Giralt, Santiago

    2014-05-01

    The variability of North Atlantic tropical storms has been the focus of several studies. Duration and seasonality has been attributed to a number of climate patterns and processes such as El Niño-Southern Oscillation, Atlantic Meridional Mode, African easterly waves, and atmospheric Rossby waves, but their tracks have been widely related to the North Atlantic Oscillation. Several authors have pointed out an increase and track shifting of North Atlantic tropical cyclones since 1995 with increased probability of these turning north far away from the North American continent. However, this cannot be regarded as an infrequent phenomenon as most proxy records from the Atlantic North have shown the existence of similar patterns in the past. Sao Miguel Island (Azores archipelago, Portugal) is settled in the middle of the Atlantic Ocean. This location makes this island an excellent natural laboratory to record shifts on North Atlantic tropical storms tracks that can reach the archipelago as low intensity hurricanes (e.g. Nadine in 2012) or downgraded to tropical storm (e.g. Grace in 2009). In the present work, lake sediment records have been used as a proxy sensor of tropical storms. Lagoa Azul is located inside Sete Cidades volcanic caldera and its catchment is characterized by stepped and forested caldera walls. Tropical storms and heavy rainfalls produce a flashy and substantial enhancement in the erosion of the catchment, increasing the sediments reaching the lake by rockfalls deposits (in littoral zones) and flood events deposits (in offshore zones). These flood events can be recognized in the sedimentary record as lobe deposits dominated by terrestrial components. It can be found in the sedimentary record and the bathymetry. Instrumental meteorological data and historical records have been compiled to reconstruct the most recent history of the North Atlantic tropical storms that have landed or affected the Sao Miguel Island (Andrade et al., 2008). In addition, a 1

  17. Patterns of distribution of deepwater demersal fishes of the North Atlantic mid-ocean ridge, continental slopes, islands and seamounts

    NASA Astrophysics Data System (ADS)

    Bergstad, Odd Aksel; Menezes, Gui M. M.; Høines, Åge S.; Gordon, John D. M.; Galbraith, John K.

    2012-03-01

    Basin-scale spatial and depth-related distribution patterns of deepwater demersal fishes were analysed using bottom trawl datasets from the North Atlantic continental margin, slopes of oceanic islands and seamounts, and the mid-Atlantic Ridge. Depth-stratified presence-absence data for 593 species were compiled from fisheries-independent trawl studies with full species lists. The datasets comprised trawls conducted on the upper continental slope (200 m) to abyssal depths, and 750 m wide depth strata were used. Number of species and families declined with depth in all areas. Species number was highest in the western North Atlantic, significantly lower on the mid-Atlantic Ridge and eastern North Atlantic. Observed species numbers are also low in southern areas (Bahamas, NW Africa, southerly seamounts), but the sampling effort in these waters has been much less than in northern sites. Fish assemblages vary by depth, latitude and longitude, and the study corroborates earlier suggestions that assemblages are broadly distributed in relation to regional circulation and watermass features. The mid-Atlantic Ridge assemblages between Iceland and the Azores are most similar to those on eastern North Atlantic slopes and rises, rather dissimilar to all others, including western Atlantic, Greenland, northwest Africa and Azorean seamount and island assemblages. Across the North Atlantic differences between subareas are strongest at slope depths, much less pronounced at the less speciose rise and abyssal depths. Demersal fish biomass estimates suggest that the American slope (New England) has low biomass compared with Newfoundland and European areas, and that the supposedly oligotrophic mid-Atlantic Ridge has a level of biomass similar to or higher than the European margin.

  18. North Atlantic forcing of tropical Indian Ocean climate.

    PubMed

    Mohtadi, Mahyar; Prange, Matthias; Oppo, Delia W; De Pol-Holz, Ricardo; Merkel, Ute; Zhang, Xiao; Steinke, Stephan; Lückge, Andreas

    2014-05-01

    The response of the tropical climate in the Indian Ocean realm to abrupt climate change events in the North Atlantic Ocean is contentious. Repositioning of the intertropical convergence zone is thought to have been responsible for changes in tropical hydroclimate during North Atlantic cold spells, but the dearth of high-resolution records outside the monsoon realm in the Indian Ocean precludes a full understanding of this remote relationship and its underlying mechanisms. Here we show that slowdowns of the Atlantic meridional overturning circulation during Heinrich stadials and the Younger Dryas stadial affected the tropical Indian Ocean hydroclimate through changes to the Hadley circulation including a southward shift in the rising branch (the intertropical convergence zone) and an overall weakening over the southern Indian Ocean. Our results are based on new, high-resolution sea surface temperature and seawater oxygen isotope records of well-dated sedimentary archives from the tropical eastern Indian Ocean for the past 45,000 years, combined with climate model simulations of Atlantic circulation slowdown under Marine Isotope Stages 2 and 3 boundary conditions. Similar conditions in the east and west of the basin rule out a zonal dipole structure as the dominant forcing of the tropical Indian Ocean hydroclimate of millennial-scale events. Results from our simulations and proxy data suggest dry conditions in the northern Indian Ocean realm and wet and warm conditions in the southern realm during North Atlantic cold spells. PMID:24784218

  19. North Atlantic forcing of tropical Indian Ocean climate.

    PubMed

    Mohtadi, Mahyar; Prange, Matthias; Oppo, Delia W; De Pol-Holz, Ricardo; Merkel, Ute; Zhang, Xiao; Steinke, Stephan; Lückge, Andreas

    2014-05-01

    The response of the tropical climate in the Indian Ocean realm to abrupt climate change events in the North Atlantic Ocean is contentious. Repositioning of the intertropical convergence zone is thought to have been responsible for changes in tropical hydroclimate during North Atlantic cold spells, but the dearth of high-resolution records outside the monsoon realm in the Indian Ocean precludes a full understanding of this remote relationship and its underlying mechanisms. Here we show that slowdowns of the Atlantic meridional overturning circulation during Heinrich stadials and the Younger Dryas stadial affected the tropical Indian Ocean hydroclimate through changes to the Hadley circulation including a southward shift in the rising branch (the intertropical convergence zone) and an overall weakening over the southern Indian Ocean. Our results are based on new, high-resolution sea surface temperature and seawater oxygen isotope records of well-dated sedimentary archives from the tropical eastern Indian Ocean for the past 45,000 years, combined with climate model simulations of Atlantic circulation slowdown under Marine Isotope Stages 2 and 3 boundary conditions. Similar conditions in the east and west of the basin rule out a zonal dipole structure as the dominant forcing of the tropical Indian Ocean hydroclimate of millennial-scale events. Results from our simulations and proxy data suggest dry conditions in the northern Indian Ocean realm and wet and warm conditions in the southern realm during North Atlantic cold spells.

  20. North American amphibians: distribution and diversity

    USGS Publications Warehouse

    : Green, David M.; Weir, Linda A.; Casper, Gary S.; Lannoo, Michael

    2014-01-01

    Some 300 species of amphibians inhabit North America. The past two decades have seen an enormous growth in interest about amphibians and an increased intensity of scientific research into their fascinating biology and continent-wide distribution. This atlas presents the spectacular diversity of North American amphibians in a geographic context. It covers all formally recognized amphibian species found in the United States and Canada, many of which are endangered or threatened with extinction. Illustrated with maps and photos, the species accounts provide current information about distribution, habitat, and conservation. Researchers, professional herpetologists, and anyone intrigued by amphibians will value North American Amphibians as a guide and reference.

  1. Key areas for wintering North American herons

    USGS Publications Warehouse

    Mikuska, T.; Kushlan, J.A.; Hartley, S.

    1998-01-01

    Nearly all North American heron populations are migratory, but details of where they winter are little known. Locations where North American herons winter were identified using banding recovery data. North American herons winter from Canada through northern South America but especially in eastern North America south of New York, Florida, California, Louisiana, Texas, Mexico and Cuba, these areas accounting for 63% of winter recoveries. We identified regions where recoveries for various species clustered as "key areas." These forty-three areas constitute a network of areas that hold sites that likely are important to wintering North American herons. Within each area, we identify specific sites that are potentially important to wintering herons. The relative importance of each area and site within the network must be evaluated by further on the ground inventory. Because of biases inherent in the available data, these hypothesized key areas are indicative rather than exhaustive. As a first cut, this network of areas can serve to inform further inventory activities and can provide an initial basis to begin planning for the year-round conservation of North American heron populations.

  2. Atmospheric transport of pollutants from North America to the North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Harriss, R. C.; Browell, E. V.; Sebacher, D. I.; Gregory, G. L.; Hinton, R. R.; Beck, S. M.; Mcdougal, D. S.; Shipley, S. T.

    1984-01-01

    Ground-based measurements strongly support the hypothesis that pollutant materials of anthropogenic origin are being transported over long distances in the midtroposphere and are a significant source of acid rain, acid snow, trace metal deposition, ozone and visibility-reducing aerosols in remote oceanic and polar regions of the Norhern Hemisphere. Atmospheric sulphur budget calculations and studies of acid rain on Bermuda indicate that a large fraction of pollutant materials emitted into the atmosphere in eastern North America are advected eastwards over the North Atlantic Ocean. The first direct airborne measurements of the vertical distribution of tropospheric aerosols over the western North Atlantic is reported here. A newly developed airborne differential adsorption lidar system was used to obtain continuous, remotely sensed aerosol distributions along its flight path. The data document two episodes of long-distance transport of pollutant materials from North America over the North Atlantic Ocean.

  3. Study of North Atlantic ventilation using transient tracers. Doctoral Thesis

    SciTech Connect

    Doney, S.C.

    1991-08-01

    Tritium, (3)He, and chlorofluorocarbon distributions in the North Atlantic provide constraints on the ventilation time-scales for the thermocline and abyssal water. A new model function based on a factor analysis of the WMO/IAEA precipitation data set is developed for predicting the spatial and temporal patterns of bomb-tritium in precipitation. Model atmospheric and advective tritium inputs to the North Atlantic are compared with the observed bomb-tritium inventories calculated from the 1972 GEOSECS and 1981-1983 TTO data sets. The observed growth of bomb-tritium levels in the deep North Atlantic are used, along with the tracer gradients ((3)H and (3)He) in the Deep Western Boundary Current, to estimate abyssal ventilation rates and boundary current recirculation. The surface boundary conditions for different transient tracers are found to profoundly effect thermocline ventilation rates estimates. Tracers that equilibrate rapidly with the atmosphere, such as (3)He and the CFCs, have faster apparent ventilation rates and are more appropriate for estimating oxygen utilization rates than tracers that are reset slowly in the surface ocean (e.g. (3)H and (14)C). The chlorofluorocarbon data for a new section in the eastern North Atlantic are presented and used to illustrate the ventilation time-scales for the major water masses in the region. (Copyright (c) Scott C. Doney, 1991.)

  4. CHARACTERIZATION OF WESTERN NORTH ATLANTIC RIGHT WHALE SPRING FEEDING HABITAT

    EPA Science Inventory

    The Great South Channel region of the southwestern Gulf of Maine, between George's Bank and Cape Cod, is the primary spring feeding ground for the western North Atlantic population of the I northern right whale, E. glacialis .Since this whale is so endangered, it is critical to i...

  5. The Response of the North Atlantic Bloom to NAO Forcing

    NASA Technical Reports Server (NTRS)

    Mizoguchi, Ken-Ichi; Worthen, Denise L.; Hakkinen, Sirpa; Gregg, Watson W.

    2004-01-01

    Results from the climatologically forced coupled ice/ocean/biogeochemical model that covers the Arctic and North Atlantic Oceans are presented and compared to the chlorophyll fields of satellite-derived ocean color measurements. Biogeochemical processes in the model are determined from the interactions among four phytoplankton functional groups (diatoms, chlorophytes, cyanobacteria and coccolithophores) and four nutrients (nitrate, ammonium, silicate and dissolved iron). The model simulates the general large-scale pattern in April, May and June, when compared to both satellite-derived and in situ observations. The subpolar North Atlantic was cool in the 1980s and warm in the latter 1990s, corresponding to the CZCS and SeaWiFS satellite observing periods, respectively. The oceanographic conditions during these periods resemble the typical subpolar upper ocean response to the NAO+ and NAO-phases, respectively. Thus, we use the atmospheric forcing composites from the two NAO phases to simulate the variability of the mid-ocean bloom during the satellite observing periods. The model results show that when the subpolar North Atlantic is cool, the NAO+ case, more nutrients are available in early spring than when the North Atlantic is warm, the NAO-case. However, the NAO+ simulation produces a later bloom than the NAO-simulation. This difference in the bloom times is also identified in SeaWiFS and CZCS satellite measurements. In the model results, we can trace the difference to the early diatom bloom due to a warmer upper ocean. The higher nutrient abundance in the NAO+ case did not provide larger total production than in the NAO- case, instead the two cases had a comparable area averaged amplitude. This leads us to conclude that in the subpolar North Atlantic, the timing of the spring phytoplankton bloom depends on surface temperature and the magnitude of the bloom is not significantly impacted by the nutrient abundance.

  6. Extratropical North Atlantic SST influence on Sahel rainfall

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Chiang, J. C.

    2013-12-01

    We present evidence suggesting that the late 1960's Sahel drought was linked to an abrupt cooling in the extratropical North Atlantic, whose influence was then propagated to the Sahel by atmospheric teleconnection. Such linkages have been observed in paleoclimate during abrupt climate changes of the last glacial period. They have also occurred in coupled model simulations of Atlantic meridional overturning circulation (AMOC) slowdown, the latter being the leading cause of said paleoclimate abrupt changes. The AMOC-slowdown simulations show a characteristic global pattern of climate changes, including a northern hemispheric-wide cooling and increased surface pressure, and weakening of the West African and Asian monsoons. We show that an observed northern-hemispheric pattern of changes, resembling the AMOC slowdown, occurred during the late 1960's, co-incident with the Sahel drought. A combined principal component analysis of 20th century surface temperature, sea level pressure and precipitation extracts a leading mode whose spatial pattern closely resemble the impacts of AMOC slowdown. A similar analysis of AMIP-type simulations forced by 20th century observed forcings shows a similar result, suggesting that the origins of the climate change reside in SST changes, in particular over extratropical North Atlantic. Taken together, the results suggests the influence of extratropical North Atlantic cooling on the 20th century Sahel drought, and a teleconnection pathway through surface/tropospheric cooling. Motivated by our observational result, we investigated atmospheric teleconnection mechanisms of extratropical North Atlantic cooling in an atmospheric general circulation model (GCM) coupled with slab ocean. Our results indicate the central role of tropospheric cooling in communicating the influence on the Sahel. We explicitly show this using regional climate model simulation of the Sahel, with air temperature and associated humidity anomalies from the GCM simulation

  7. North American LNG Project Sourcebook

    SciTech Connect

    2007-06-15

    The report provides a status of the development of LNG Import Terminal projects in North America, and includes 1-2 page profiles of 63 LNG projects in North America which are either in operation, under construction, or under development. For each project, the sourcebook provides information on the following elements: project description, project ownership, project status, projected operation date, storage capacity, sendout capacity, and pipeline interconnection.

  8. North Atlantic magmatism controlled by temperature, mantle composition and buoyancy

    NASA Astrophysics Data System (ADS)

    Brown, Eric L.; Lesher, Charles E.

    2014-11-01

    Large igneous provinces are characterized by anomalously high rates of magma production. Such voluminous magmatism is commonly attributed to partial melting of hot, buoyantly upwelling mantle plume material. However, compositional heterogeneity in the mantle, caused by the subduction of oceanic crust, can also enhance magma production, diminishing the need for elevated temperatures associated with upwelling plumes. A plume origin for the North Atlantic large igneous province has been questioned because lava compositions correlate with crustal thickness, implying a link between magma productivity and mantle source composition. Here we use a numerical model that simulates upwelling and melting of compositionally heterogeneous mantle material to constrain the conditions that gave rise to magmatism in the North Atlantic. Using observations of lava compositions and volumes from the North Atlantic, we show that subducted crustal material represented less than 10% of the mantle source. We further show that mantle temperatures have remained elevated by 85-210 °C and increased mantle upwelling up to 14 times the rate of plate separation has occurred over the past 56 Myr. The enhanced temperatures and upwelling rates extended along more than 1,000 km of the Palaeogene rift, but are substantially more restricted along the modern Mid-Atlantic Ridge. These findings reflect the long-term manifestation of a mantle plume.

  9. The carbon balance of North American wetlands

    USGS Publications Warehouse

    Bridgham, S.D.; Megonigal, J.P.; Keller, J.K.; Bliss, N.B.; Trettin, C.

    2006-01-01

    We examine the carbon balance of North American wetlands by reviewing and synthesizing the published literature and soil databases. North American wetlands contain about 220 Pg C, most of which is in peat. They are a small to moderate carbon sink of about 49 Tg C yr-1, although the uncertainty around this estimate is greater than 100%, with the largest unknown being the role of carbon sequestration by sedimentation in freshwater mineral-soil wetlands. We estimate that North American wetlands emit 9 Tg methane (CH 4) yr-1; however, the uncertainty of this estimate is also greater than 100%. With the exception of estuarine wetlands, CH4 emissions from wetlands may largely offset any positive benefits of carbon sequestration in soils and plants in terms of climate forcing. Historically, the destruction of wetlands through land-use changes has had the largest effects on the carbon fluxes and consequent radiative forcing of North American wetlands. The primary effects have been a reduction in their ability to sequester carbon (a small to moderate increase in radiative forcing), oxidation of their soil carbon reserves upon drainage (a small increase in radiative forcing), and reduction in CH4 emissions (a small to large decrease in radiative forcing). It is uncertain how global changes will affect the carbon pools and fluxes of North American wetlands. We will not be able to predict accurately the role of wetlands as potential positive or negative feedbacks to anthropogenic global change without knowing the integrative effects of changes in temperature, precipitation, atmospheric carbon dioxide concentrations, and atmospheric deposition of nitrogen and sulfur on the carbon balance of North American wetlands. 

  10. The Southern Cone: A critical element in North American geology

    SciTech Connect

    Dalziel, I.W.D. . Inst. for Geophysics)

    1993-02-01

    The Pacific and Atlantic-Gulf of Mexico continental margins converge towards southern Mexico, delimiting the Southern Cone of North American. The margins are controlled by late Precambrian to early Paleozoic rift systems. The Neoproterozoic rifts along the Pacific margin truncate the 1.3--1.0 Ga Grenville-Llano front and still older structural boundaries within the craton, such as the Snowbird line. The Atlantic margin originated by separation from another continent within the Grenville orogen near the time of the Precambrian-Cambrian boundary. The Gulf of Mexico margin was initiated with rifting at that time, but appears to truncate the Ordovician Taconian orogen in Georgia. The continental margins of the Southern Cone may prove critical in understanding the origin of North America as a discrete continent. A possible continuation of the Grenville-Llano front has now been identified along the Pacific margin of the East Antarctic craton; the opposite side of the Grenville orogen may be present in South America and East Antarctic; a southern continuation of the Taconic Appalachians may have been identified in southern South American and Antarctica (L. Dalla Salda et al., Geology, 1992 a;b: I. Dalziel, Geology, 1991, and GSA Today, 1992; P. Hoffman, Science, 1991; E. Moores, Geology, 1991). Thus the geology of the Southern Cone of North America provides opportunities for critical testing of these globally important hypotheses, notably through geochronometry, isotope geochemistry, stratigraphy, and paleobiogeography. Conversely, East Antarctica, southern Africa, and the proto-Andean margin of South America may offer exciting opportunities to further understanding of pre-Pangea geology across southern North America.

  11. Key areas for wintering North American herons

    USGS Publications Warehouse

    Mikuska, T.; Kushlan, J.A.; Hartley, S.

    1998-01-01

    Nearly all North American heron populations are migratory, but details of where they winter are little known. Locations where North American herons winter were identified using banding recovery data. North American herons winter from Canada through northern South America but especially in eastern North America south of New York, Florida, California, Louisiana, Texas, Mexico and Cuba, these areas accounting for 63% of winter recoveries. We identified regions where recoveries for various species clustered as 'key areas.' These forty-three areas constitute a network of areas that hold sites that likely are important to wintering herons. The relative importance of each area and site within the network must be evaluated by further on the ground inventory. Because of biases inherent in the available data, these hypothesized key areas are indicative rather than exhaustive. As a first cut, this network of areas can serve to inform further inventory activities and can provide an initial basis to begin planning for the year-round conservation of North American heron populations.

  12. Summer North Atlantic Oscillation and flood variability in Switzerland

    NASA Astrophysics Data System (ADS)

    Peña, Juan Carlos; Schulte, Lothar; Badoux, Alexandre

    2016-04-01

    The study analyses the possible links between flood frequency in Switzerland and the North Atlantic dynamics over the last two centuries. Given the intricate topography of Switzerland, it will generate a territorial division to retain main physiographic and environmental dissimilarities between different regions. The flood variability in Switzerland over the period 1800-2010 has been determined from a flood damage index for July and August months. The index considers very severe and catastrophic floods from existing flood inventories, summarizing both the severity of these events, their spatial extent and the regional differences. Special attention will be focused on the disparities between flood dynamics at northern and southern slopes of the Alps. The analysis of the possible links between floods and North Atlantic dynamics is focused on the low-frequency atmospheric circulation patterns. Summer climate in the North Atlantic-European sector shows a principal pattern of year-to-year variability, although this pattern is weaker than the North Atlantic Oscillation (NAO) in winter and is confined to northern latitudes. By analogy the climatology community refers to this pattern as the Summer North Atlantic Oscillation (SNAO), which is defined as the main empirical orthogonal function of the standardized anomalies of the European mean sea level pressure during July and August. The flood damage index provides evidences of floods clusters in: 1830-1851, 1881-1927, 1977-1990 and 2005 to present. These clusters coincide with those reported from Switzerland and from some areas of the European continent such as the Czech Republic, Italy and the eastern half of the Iberian Peninsula. This link is not so close when compared with the flood occurrences in Germany. The analysis of the principal mode of low-frequency atmospheric variability shows that the Swiss river catchments situated on the center and southern flank of the Alps are affected by atmospherically unstable areas

  13. North Atlantic-Fennoscandian Holocene climate trends and mechanisms

    NASA Astrophysics Data System (ADS)

    Sejrup, Hans Petter; Seppä, Heikki; McKay, Nicholas P.; Kaufman, Darrell S.; Geirsdóttir, Áslaug; de Vernal, Anne; Renssen, Hans; Husum, Katrine; Jennings, Anne; Andrews, John T.

    2016-09-01

    To investigate the mechanisms behind Holocene regional climate trends from north of 58°N in the North Atlantic-Fennoscandian region Principal Component Analysis (PCA) was performed and a temperature anomaly stack produced from 81 proxy derived summer temperature time series from 74 sites. The PC results show distinctly different trends for near-surface versus surface temperatures, demonstrating the importance of handling these separately. The first PC of weighted sea surface summer temperature time series and continental time series explains 45 ± 8% of the variance, where the uncertainty is the standard deviation of the distribution of variance explained across the 1000 age-uncertain ensemble members. PC1 has a relatively uniform expression over the whole region, closely following the summer insolation at 65°N. The second PC explains 22 ± 4% of the variance and shows a non-uniform expression, with loadings in opposite directions in the northern and southeastern parts of the region. Comparing the PC time series with model runs and with the timing of the demise of the Laurentide Ice Sheet (LIS), suggest that this pattern reflects both topographic and albedo effects of the LIS as well as release of meltwater into the North Atlantic and Arctic Oceans. Comparing the stack of gridded records with published global stacks reveals an unusual Holocene temperature development in the North Atlantic-Fennoscandian region most likely resulting from the location relative to the decaying LIS.

  14. Paleoceanography. Onset of Mediterranean outflow into the North Atlantic.

    PubMed

    Hernández-Molina, F Javier; Stow, Dorrik A V; Alvarez-Zarikian, Carlos A; Acton, Gary; Bahr, André; Balestra, Barbara; Ducassou, Emmanuelle; Flood, Roger; Flores, José-Abel; Furota, Satoshi; Grunert, Patrick; Hodell, David; Jimenez-Espejo, Francisco; Kim, Jin Kyoung; Krissek, Lawrence; Kuroda, Junichiro; Li, Baohua; Llave, Estefania; Lofi, Johanna; Lourens, Lucas; Miller, Madeline; Nanayama, Futoshi; Nishida, Naohisa; Richter, Carl; Roque, Cristina; Pereira, Hélder; Sanchez Goñi, Maria Fernanda; Sierro, Francisco J; Singh, Arun Deo; Sloss, Craig; Takashimizu, Yasuhiro; Tzanova, Alexandrina; Voelker, Antje; Williams, Trevor; Xuan, Chuang

    2014-06-13

    Sediments cored along the southwestern Iberian margin during Integrated Ocean Drilling Program Expedition 339 provide constraints on Mediterranean Outflow Water (MOW) circulation patterns from the Pliocene epoch to the present day. After the Strait of Gibraltar opened (5.33 million years ago), a limited volume of MOW entered the Atlantic. Depositional hiatuses indicate erosion by bottom currents related to higher volumes of MOW circulating into the North Atlantic, beginning in the late Pliocene. The hiatuses coincide with regional tectonic events and changes in global thermohaline circulation (THC). This suggests that MOW influenced Atlantic Meridional Overturning Circulation (AMOC), THC, and climatic shifts by contributing a component of warm, saline water to northern latitudes while in turn being influenced by plate tectonics.

  15. Paleoceanography. Onset of Mediterranean outflow into the North Atlantic.

    PubMed

    Hernández-Molina, F Javier; Stow, Dorrik A V; Alvarez-Zarikian, Carlos A; Acton, Gary; Bahr, André; Balestra, Barbara; Ducassou, Emmanuelle; Flood, Roger; Flores, José-Abel; Furota, Satoshi; Grunert, Patrick; Hodell, David; Jimenez-Espejo, Francisco; Kim, Jin Kyoung; Krissek, Lawrence; Kuroda, Junichiro; Li, Baohua; Llave, Estefania; Lofi, Johanna; Lourens, Lucas; Miller, Madeline; Nanayama, Futoshi; Nishida, Naohisa; Richter, Carl; Roque, Cristina; Pereira, Hélder; Sanchez Goñi, Maria Fernanda; Sierro, Francisco J; Singh, Arun Deo; Sloss, Craig; Takashimizu, Yasuhiro; Tzanova, Alexandrina; Voelker, Antje; Williams, Trevor; Xuan, Chuang

    2014-06-13

    Sediments cored along the southwestern Iberian margin during Integrated Ocean Drilling Program Expedition 339 provide constraints on Mediterranean Outflow Water (MOW) circulation patterns from the Pliocene epoch to the present day. After the Strait of Gibraltar opened (5.33 million years ago), a limited volume of MOW entered the Atlantic. Depositional hiatuses indicate erosion by bottom currents related to higher volumes of MOW circulating into the North Atlantic, beginning in the late Pliocene. The hiatuses coincide with regional tectonic events and changes in global thermohaline circulation (THC). This suggests that MOW influenced Atlantic Meridional Overturning Circulation (AMOC), THC, and climatic shifts by contributing a component of warm, saline water to northern latitudes while in turn being influenced by plate tectonics. PMID:24926012

  16. Abstracting the Pacific Ocean's Impact on North Atlantic Tropical Cyclones

    NASA Astrophysics Data System (ADS)

    Faghmous, J.; Le, M.; Liess, S.; Mesquita, M.; Kumar, V.

    2012-12-01

    The warming anomalies of sea surface temperatures (SSTs) along the near- equatorial Pacific Ocean (ENSO) have well documented global long-range weather teleconnections from rainfall in southern India to mudslides in the western United States. In this work, we focus on ENSO's teleconnections with North Atlantic tropical cyclone (TC) activity. Traditionally, ENSO's impact on Atlantic TCs has been abstracted by monitoring the warming of static regions along the equatorial Pacific Ocean. We propose that the spatial distribution of Pacific Ocean warming might provide better predictive insights into ENSO-Atlantic TC impact than warming anomalies alone. We present a distance-based ENSO index (S-ENSO for spatial ENSO) that tracks the location of the maximum near-tropical Pacific warming anomaly instead the absolute warming of a static region. Our spatial ENSO index correlates better with seasonal TC activity than standard ENSO indices, especially with increased lead times.

  17. Closing the North American Carbon Budget: Continental Margin Fluxes Matter!

    NASA Astrophysics Data System (ADS)

    Najjar, R.; Benway, H. M.; Siedlecki, S. A.; Boyer, E. W.; Cai, W. J.; Coble, P. G.; Cross, J. N.; Friedrichs, M. A.; Goni, M. A.; Griffith, P. C.; Herrmann, M.; Lohrenz, S. E.; Mathis, J. T.; McKinley, G. A.; Pilskaln, C. H.; Smith, R. A.; Alin, S. R.

    2015-12-01

    Despite their relatively small surface area, continental margins are regions of intense carbon and nutrient processing, export and exchange, and thus have a significant impact on global biogeochemical cycles. In response to recommendations for regional synthesis and carbon budget estimation for North America put forth in the North American Continental Margins workshop report (Hales et al., 2008), the Ocean Carbon and Biogeochemistry (OCB) Program and North American Carbon Program (NACP) began coordinating a series of collaborative, interdisciplinary Coastal CARbon Synthesis (CCARS) research activities in five coastal regions of North America (Atlantic Coast, Pacific Coast, Gulf of Mexico, Arctic, Laurentian Great Lakes) to improve quantitative assessments of the North American carbon budget. CCARS workshops and collaborative research activities have resulted in the development of regional coastal carbon budgets based on recent literature- and model-based estimates of major carbon fluxes with estimated uncertainties. Numerous peer-reviewed papers and presentations by involved researchers have highlighted these findings and provided more in-depth analyses of processes underlying key carbon fluxes in continental margin systems. As a culminating outcome of these synthesis efforts, a comprehensive science plan highlights key knowledge gaps identified during this synthesis and provides explicit guidance on future research and observing priorities in continental margin systems to help inform future agency investments in continental margins research. This presentation will provide an overview of regional and flux-based (terrestrial inputs, biological transformations, sedimentary processes, atmospheric exchanges, lateral carbon transport) synthesis findings and key recommendations in the science plan, as well as a set of overarching priorities and recommendations on observations and modeling approaches for continental margin systems.

  18. A predictive relationship between early season North Atlantic hurricane activity and the upcoming winter North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

    Boyd, Jessica; Saunders, Mark

    2016-04-01

    The winter North Atlantic Oscillation (NAO) is linked strongly to European winter climate including windstorms. Predicting the winter NAO is key to making successful seasonal predictions of European winter climate. We observe that in recent decades there are many instances of an inverse relationship between the strength of the North Atlantic hurricane season and the strength of the subsequent European winter windstorm season. Stormy European winter seasons often follow quiet Atlantic hurricane seasons and calm European winters follow active hurricane seasons. We explore the strength and temporal stability of this inverse relationship, consider a facilitating physical mechanism, and briefly discuss the implications of our findings for end users, in particular global reinsurers. We find there is a statistically significant link between North Atlantic hurricane activity and the upcoming winter NAO. The relationship is established by the midway point of the hurricane season in early September. The link is strongest when hurricane activity is in the upper or lower tercile and when summer ENSO (El Niño Southern Oscillation) is neutral. The relationship works well going back 40 years to the mid 1970s. The early winter (October-November-December) NAO is predicted best but since the early 1980s the predictive link extends to the main winter (December-January-February) NAO. The inverse link can be facilitated by a persistence and slow evolution of atmospheric circulation patterns and sea surface temperature anomalies over the North Atlantic between the summer and the winter. This persistence is best when hurricane seasons are more extreme and when summer ENSO is neutral. Our findings offer the potential for predicting the early winter and winter NAO from early September. The implied inverse relationship between US hurricane activity and European windstorm activity may enable more effective offsetting of risks between territories.

  19. North Atlantic explosive cyclones and large scale atmospheric variability modes

    NASA Astrophysics Data System (ADS)

    Liberato, Margarida L. R.

    2015-04-01

    Extreme windstorms are one of the major natural catastrophes in the extratropics, one of the most costly natural hazards in Europe and are responsible for substantial economic damages and even fatalities. During the last decades Europe witnessed major damage from winter storms such as Lothar (December 1999), Kyrill (January 2007), Klaus (January 2009), Xynthia (February 2010), Gong (January 2013) and Stephanie (February 2014) which exhibited uncommon characteristics. In fact, most of these storms crossed the Atlantic in direction of Europe experiencing an explosive development at unusual lower latitudes along the edge of the dominant North Atlantic storm track and reaching Iberia with an uncommon intensity (Liberato et al., 2011; 2013; Liberato 2014). Results show that the explosive cyclogenesis process of most of these storms at such low latitudes is driven by: (i) the southerly displacement of a very strong polar jet stream; and (ii) the presence of an atmospheric river (AR), that is, by a (sub)tropical moisture export over the western and central (sub)tropical Atlantic which converges into the cyclogenesis region and then moves along with the storm towards Iberia. Previous studies have pointed to a link between the North Atlantic Oscillation (NAO) and intense European windstorms. On the other hand, the NAO exerts a decisive control on the average latitudinal location of the jet stream over the North Atlantic basin (Woollings et al. 2010). In this work the link between North Atlantic explosive cyclogenesis, atmospheric rivers and large scale atmospheric variability modes is reviewed and discussed. Liberato MLR (2014) The 19 January 2013 windstorm over the north Atlantic: Large-scale dynamics and impacts on Iberia. Weather and Climate Extremes, 5-6, 16-28. doi: 10.1016/j.wace.2014.06.002 Liberato MRL, Pinto JG, Trigo IF, Trigo RM. (2011) Klaus - an exceptional winter storm over Northern Iberia and Southern France. Weather 66:330-334. doi:10.1002/wea.755 Liberato

  20. 78 FR 56151 - Safety Zone, North Atlantic Ocean; Virginia Beach, VA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-12

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone, North Atlantic Ocean; Virginia Beach, VA... zone on the navigable waters of the North Atlantic Ocean in Virginia Beach, VA to support the Virginia... over the navigable waters of the Atlantic Ocean. Due to the need to protect mariners and...

  1. Is There Really A North American Plate?

    NASA Astrophysics Data System (ADS)

    Krill, A.

    2011-12-01

    Lithospheric plates are typically identified from earthquake epicenters and evidence such as GPS movements. But no evidence indicates a plate boundary between the North American and South American Plates. Some plate maps show them separated by a transform boundary, but it is only a fracture zone. Other maps show an "undefined plate boundary" or put no boundary between these two plates (check Google images). Early plate maps showed a single large American Plate, quite narrow east of the Caribbean Plate (Le Pichon 1968, Morgan 1968). The North and South American Plates became established by the leading textbook Earth (Press & Siever 1974). On their map, from a Scientific American article by John Dewey (1972), these new plates were separated by an "uncertain plate boundary." The reasons for postulating a North American Plate were probably more psychological than geological. Each of the other continents of the world had its own plate, and North American geologists naturally wanted theirs. Similarly, European geographers used to view Europe as its own continent. A single large plate should again be hypothesized. But the term American Plate would now be ambiguous ("Which plate, North or South?") Perhaps future textbook authors could call it the "Two-American Plate." Textbook authors ultimately decide such global-tectonic matters. I became aware of textbook authors' opinions and influence from my research into the history of Alfred Wegener's continental drift (see Fixists vs. Mobilists by Krill 2011). Leading textbook author Charles Schuchert realized that continental drift would abolish his cherished paleogeographic models of large east-west continents (Eria, Gondwana) and small oceans (Poseiden, Nereis). He and his junior coauthors conspired to keep drift evidence out of their textbooks, from the 1934-editions until the 1969-editions (Physical Geology by Longwell et al. 1969, Historical Geology by Dunbar & Waage 1969). Their textbooks ruled in America. Textbooks

  2. Introgressive hybridization and latitudinal admixture clines in North Atlantic eels

    PubMed Central

    2014-01-01

    Background Hybridization, the interbreeding of diagnosably divergent species, is a major focus in evolutionary studies. Eels, both from North America and Europe migrate through the Atlantic to mate in a vast, overlapping area in the Sargasso Sea. Due to the lack of direct observation, it is unknown how these species remain reproductively isolated. The detection of inter-species hybrids in Iceland suggests on-going gene flow, but few studies to date have addressed the influence of introgression on genetic differentiation in North Atlantic eels. Results Here, we show that while mitochondrial lineages remain completely distinct on both sides of the Atlantic, limited hybridization is detectable with nuclear DNA markers. The nuclear hybridization signal peaks in the northern areas and decreases towards the southern range limits on both continents according to Bayesian assignment analyses. By simulating increasing proportions of both F1 hybrids and admixed individuals from the southern to the northern-most locations, we were able to generate highly significant isolation-by-distance patterns in both cases, reminiscent of previously published data for the European eel. Finally, fitting an isolation-with-migration model to our data supports the hypothesis of recent asymmetric introgression and refutes the alternative hypothesis of ancient polymorphism. Conclusions Fluctuating degrees of introgressive hybridization between Atlantic eel species are sufficient to explain temporally varying correlations of geographic and genetic distances reported for populations of the European eel. PMID:24674242

  3. Synchronous climate changes in antarctica and the north atlantic

    PubMed

    Steig; Brook; White; Sucher; Bender; Lehman; Morse; Waddington; Clow

    1998-10-01

    Central Greenland ice cores provide evidence of abrupt changes in climate over the past 100,000 years. Many of these changes have also been identified in sedimentary and geochemical signatures in deep-sea sediment cores from the North Atlantic, confirming the link between millennial-scale climate variability and ocean thermohaline circulation. It is shown here that two of the most prominent North Atlantic events-the rapid warming that marks the end of the last glacial period and the Bolling/Allerod-Younger Dryas oscillation-are also recorded in an ice core from Taylor Dome, in the western Ross Sea sector of Antarctica. This result contrasts with evidence from ice cores in other regions of Antarctica, which show an asynchronous response between the Northern and Southern Hemispheres.

  4. Synchronous climate changes in Antarctica and the North Atlantic

    USGS Publications Warehouse

    Steig, E.J.; Brook, E.J.; White, J.W.C.; Sucher, C.M.; Bender, M.L.; Lehman, S.J.; Morse, D.L.; Waddington, E.D.; Clow, G.D.

    1998-01-01

    Central Greenland ice cores provide evidence of abrupt changes in climate over the past 100,000 years. Many of these changes have also been identified in sedimentary and geochemical signatures in deep-sea sediment cores from the North Atlantic, confirming the link between millennial-scale climate variability and ocean thermohaline circulation. It is shown here that two of the most prominent North Atlantic events - the rapid warming that makes the end of the last glacial period and the Bolling/Allerod-Younger Dryas oscillation - are also recorded in an ice core from Taylor Dome, in the western Ross Sea sector of Antarctica. This result contrasts with evidence from ice cores in other regions of Antarctica, which show an asynchronous response between the Northern and Southern Hemispheres.

  5. Spin-Down of the North Atlantic Subpolar Circulation

    NASA Technical Reports Server (NTRS)

    Hakkinen, S.; Rhines, P. B.

    2004-01-01

    Dramatic changes have occurred in the mid-to-high-latitude North Atlantic Ocean as evidenced by TOPEX/Poseidon observations of sea surface height (SSH) in the subpolar gyre and the Gulf Stream. Analysis of altimeter data shows that subpolar SSH has increased during the 1990s and the geostrophic velocity derived from altimeter data shows a decline in the gyre circulation. Direct current-meter observations in the boundary current of the Labrador Sea support the trend in the 199Os, and, together with hydrographic data show that in the mid-late 1990s the trend extends deep in the water column. We find that buoyancy forcing over the northern North Atlantic has a dynamic effect consistent with the altimeter data and hydrographic observations: a weak thermohaline forcing and the subsequent decay of the domed structure of the subpolar isopycnals would give rise to the observed anticyclonic circulation trend.

  6. Synchronous climate changes in antarctica and the north atlantic

    PubMed

    Steig; Brook; White; Sucher; Bender; Lehman; Morse; Waddington; Clow

    1998-10-01

    Central Greenland ice cores provide evidence of abrupt changes in climate over the past 100,000 years. Many of these changes have also been identified in sedimentary and geochemical signatures in deep-sea sediment cores from the North Atlantic, confirming the link between millennial-scale climate variability and ocean thermohaline circulation. It is shown here that two of the most prominent North Atlantic events-the rapid warming that marks the end of the last glacial period and the Bolling/Allerod-Younger Dryas oscillation-are also recorded in an ice core from Taylor Dome, in the western Ross Sea sector of Antarctica. This result contrasts with evidence from ice cores in other regions of Antarctica, which show an asynchronous response between the Northern and Southern Hemispheres. PMID:9756484

  7. Climate, fishery and society interactions: Observations from the North Atlantic

    NASA Astrophysics Data System (ADS)

    Hamilton, Lawrence C.

    2007-11-01

    Interdisciplinary studies comparing fisheries-dependent regions across the North Atlantic find a number of broad patterns. Large ecological shifts, disastrous to historical fisheries, have resulted when unfavorable climatic events occur atop overfishing. The "teleconnections" linking fisheries crises across long distances include human technology and markets, as well as climate or migratory fish species. Overfishing and climate-driven changes have led to a shift downwards in trophic levels of fisheries takes in some ecosystems, from dominance by bony fish to crustaceans. Fishing societies adapt to new ecological conditions through social reorganization that have benefited some people and places, while leaving others behind. Characteristic patterns of demographic change are among the symptoms of such reorganization. These general observations emerge from a review of recent case studies of individual fishing communities, such as those conducted for the North Atlantic Arc research project.

  8. The arctic mirage and the early north atlantic.

    PubMed

    Sawatzky, H L; Lehn, W H

    1976-06-25

    The arctic mirage is a phenomenon that is common in higher latitudes. It occurs under conditions of pronounced temperature inversion, which impart to the air a refractive capability that may equal or exceed the curvature of the earth. Manifestations of the arctic mirage, though largely forgotten in modern times, are described in the earliest accounts of North Atlantic discovery. This interdisciplinary investigation, combining historical induction with scientific observation and analysis, has suggested a new interpretation of historical events. We believe that information gleaned from these mirages was vital to Norse navigation and exploration in the North Atlantic. We further contend that the mirage may furnish a logical basis for the pervasive ancient and medieval concept of the flat or saucer-shaped world. PMID:17739820

  9. North Atlantic warming and the retreat of Greenland's outlet glaciers.

    PubMed

    Straneo, Fiammetta; Heimbach, Patrick

    2013-12-01

    Mass loss from the Greenland ice sheet quadrupled over the past two decades, contributing a quarter of the observed global sea-level rise. Increased submarine melting is thought to have triggered the retreat of Greenland's outlet glaciers, which is partly responsible for the ice loss. However, the chain of events and physical processes remain elusive. Recent evidence suggests that an anomalous inflow of subtropical waters driven by atmospheric changes, multidecadal natural ocean variability and a long-term increase in the North Atlantic's upper ocean heat content since the 1950s all contributed to a warming of the subpolar North Atlantic. This led, in conjunction with increased runoff, to enhanced submarine glacier melting. Future climate projections raise the potential for continued increases in warming and ice-mass loss, with implications for sea level and climate.

  10. Indigenous Environmental Perspectives: A North American Primer.

    ERIC Educational Resources Information Center

    LaDuke, Winona

    1992-01-01

    Presents a brief overview of the nature of indigenous sustainable subsistence economies, and the present underdevelopment and dependency of North American indigenous economies resulting from colonialism and marginalization. Describes environmental and personal contamination on indigenous lands from uranium and coal mining, toxic and nuclear waste,…

  11. North American Journal of Psychology, 1999.

    ERIC Educational Resources Information Center

    McCutcheon, Lynn E., Ed.

    1999-01-01

    "North American Journal of Psychology" publishes scientific papers of general interest to psychologists and other social scientists. Articles included in volume 1 issue 1 (June 1999) are: "Generalist Looks at His Career in Teaching: Interview with Dr. Phil Zimbardo"; "Affective Information in Videos"; "Infant Communication"; "Defining Projective…

  12. North American Journal of Psychology, 2001.

    ERIC Educational Resources Information Center

    McCutcheon, Lynn E., Ed.

    2001-01-01

    "North American Journal of Psychology" publishes scientific papers of general interest to psychologists and other social scientists. Articles included in volume 3 issue 1 (March/April 2001) are: "Sense of Humor in Black and White"; "Convergent Validity of the Situational Outlook Questionnaire"; "Alcohol Consumption and Consequences in a Sample of…

  13. North American Journal of Psychology, 2002.

    ERIC Educational Resources Information Center

    McCutcheon, Lynn E., Ed.

    2002-01-01

    "North American Journal of Psychology" publishes scientific papers of general interest to psychologists and other social scientists. Articles included in volume 4 issue 1 (March 2002) are: "An Interview with Kimmo Lehtonen: Music Therapy with Adolescents"; "The Relationship of Verbal-Nonverbal Incongruence to Communication Mismatches in Married…

  14. Ideas from Ten North American Curriculum Thinkers.

    ERIC Educational Resources Information Center

    Short, Edmund C.

    The views and attitudes of ten North American educational policy-makers concerning curriculum development and design are presented. The theories and research of Herbert M. Kliebard, Fenwick W. English, Walter Werner, John I. Goodlad, Decker F. Walker, William A. Reid, Norman E. Gleadow, Neil Postman, Elliot W. Eisner, and Michael W. Apple are…

  15. Swimbladder Leiomyosarcoma in Atlantic salmon (Salmo salar) in North America.

    PubMed

    Bowser, Paul R; Casey, James W; Casey, Rufina N; Quackenbush, Sandra L; Lofton, Larry; Coll, John A; Cipriano, Rocco C

    2012-07-01

    Leiomyosarcoma with associated retrovirus were found in North America for the first time in adult Atlantic salmon (Salmo salar) held in a quarantine facility at the North Attleboro National Fish Hatchery (NANFH), Massachusetts, USA. The fish had been collected as age 1-2 yr animals from the Pleasant River, Maine, and were to be used as brood stock in a population augmentation program for that river. Neoplastic disease was observed at NANFH initially in older (age 4 yr) fish, followed by age 3 yr fish. Disease was not observed in age 2 yr fish. The mortality pattern was chronic.

  16. Towards a North Atlantic Marine Radiocarbon Calibration Curve

    NASA Astrophysics Data System (ADS)

    Austin, William; Reimer, Paula; Blaauw, Maarten; Bryant, Charlotte; Rae, James; Burke, Andrea

    2015-04-01

    Service du dejeuner! Twenty years ago, in 1995, I sailed as a post-doctoral researcher based at the University of Edinburgh (UK) on the first scientific mission of the new Marion Dufresne II. In this presentation, I will provide an update on the work that first quantified North Atlantic marine radiocarbon reservoir ages, highlighting how advances in marine tephrochronology over the last twenty years have significantly improved our understanding (and ability to test) land-ice-ocean linkages. The mechanistic link that connects marine radiocarbon reservoir ages to ocean ventilation state will also be discussed with reference to the Younger Dryas climate anomaly, where models and data have been successfully integrated. I will discuss the use of reference chronologies in the North Atlantic region and evaluate the common practice of climate synchronization between the Greenland ice cores and some of the key MD records that are now available. The exceptional quality of the MD giant piston cores and their potential to capture high-resolution last glacial sediment records from the North Atlantic provides an exciting opportunity to build new regional marine radiocarbon calibration curves. I will highlight new efforts by my co-authors and others to build such curves, setting-out a new agenda for the next twenty years of the IMAGES programme.

  17. 76 FR 53149 - North American Waterfowl Management Plan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-25

    ... Fish and Wildlife Service North American Waterfowl Management Plan AGENCY: Fish and Wildlife Service... Wildlife Service, announce the availability of the draft North American Waterfowl Management Plan Revision... Plan Revision, which was developed in close consultation with the waterfowl management...

  18. West Nile virus: North American experience

    USGS Publications Warehouse

    Hofmeister, Erik K.

    2011-01-01

    West Nile virus, a mosquito-vectored flavivirus of the Japanese encephalitis serogroup, was first detected in North America following an epizootic in the New York City area in 1999. In the intervening 11 years since the arrival of the virus in North America, it has crossed the contiguous USA, entered the Canadian provinces bordering the USA, and has been reported in the Caribbean islands, Mexico, Central America and, more recently, South America. West Nile virus has been reported in over 300 species of birds in the USA and has caused the deaths of thousands of birds, local population declines of some avian species, the clinical illness and deaths of thousands of domestic horses, and the clinical disease in over 30 000 Americans and the deaths of over 1000. Prior to the emergence of West Nile virus in North America, St. Louis encephalitis virus and Dengue virus were the only other known mosquito-transmitted flaviviruses in North America capable of causing human disease. This review will discuss the North American experience with mosquito-borne flavivirus prior to the arrival of West Nile virus, the entry and spread of West Nile virus in North America, effects on wild bird populations, genetic changes in the virus, and the current state of West Nile virus transmission.

  19. West Nile virus: North American experience.

    PubMed

    Hofmeister, Erik K

    2011-09-01

    West Nile virus, a mosquito-vectored flavivirus of the Japanese encephalitis serogroup, was first detected in North America following an epizootic in the New York City area in 1999. In the intervening 11 years since the arrival of the virus in North America, it has crossed the contiguous USA, entered the Canadian provinces bordering the USA, and has been reported in the Caribbean islands, Mexico, Central America and, more recently, South America. West Nile virus has been reported in over 300 species of birds in the USA and has caused the deaths of thousands of birds, local population declines of some avian species, the clinical illness and deaths of thousands of domestic horses, and the clinical disease in over 30 000 Americans and the deaths of over 1000. Prior to the emergence of West Nile virus in North America, St. Louis encephalitis virus and Dengue virus were the only other known mosquito-transmitted flaviviruses in North America capable of causing human disease. This review will discuss the North American experience with mosquito-borne flavivirus prior to the arrival of West Nile virus, the entry and spread of West Nile virus in North America, effects on wild bird populations, genetic changes in the virus, and the current state of West Nile virus transmission.

  20. North Atlantic Migratory Bird Flyways Provide Routes for Intercontinental Movement of Avian Influenza Viruses

    PubMed Central

    Dusek, Robert J.; Hallgrimsson, Gunnar T.; Ip, Hon S.; Jónsson, Jón E.; Sreevatsan, Srinand; Nashold, Sean W.; TeSlaa, Joshua L.; Enomoto, Shinichiro; Halpin, Rebecca A.; Lin, Xudong; Fedorova, Nadia; Stockwell, Timothy B.; Dugan, Vivien G.; Wentworth, David E.; Hall, Jeffrey S.

    2014-01-01

    Avian influenza virus (AIV) in wild birds has been of increasing interest over the last decade due to the emergence of AIVs that cause significant disease and mortality in both poultry and humans. While research clearly demonstrates that AIVs can move across the Pacific or Atlantic Ocean, there has been no data to support the mechanism of how this occurs. In spring and autumn of 2010 and autumn of 2011 we obtained cloacal swab samples from 1078 waterfowl, gulls, and shorebirds of various species in southwest and west Iceland and tested them for AIV. From these, we isolated and fully sequenced the genomes of 29 AIVs from wild caught gulls (Charadriiformes) and waterfowl (Anseriformes) in Iceland. We detected viruses that were entirely (8 of 8 genomic segments) of American lineage, viruses that were entirely of Eurasian lineage, and viruses with mixed American-Eurasian lineage. Prior to this work only 2 AIVs had been reported from wild birds in Iceland and only the sequence from one segment was available in GenBank. This is the first report of finding AIVs of entirely American lineage and Eurasian lineage, as well as reassortant viruses, together in the same geographic location. Our study demonstrates the importance of the North Atlantic as a corridor for the movement of AIVs between Europe and North America. PMID:24647410

  1. North Atlantic migratory bird flyways provide routes for intercontinental movement of avian influenza viruses

    USGS Publications Warehouse

    Dusek, Robert J.; Hallgrimsson, Gunnar T.; Ip, Hon S.; Jónsson, Jón E.; Sreevatsan, Srinand; Nashold, Sean W.; TeSlaa, Joshua L.; Enomoto, Shinichiro; Halpin, Rebecca A.; Lin, Xudong; Federova, Nadia; Stockwell, Timothy B.; Dugan, Vivien G.; Wentworth, David E.; Hall, Jeffrey S.

    2014-01-01

    Avian influenza virus (AIV) in wild birds has been of increasing interest over the last decade due to the emergence of AIVs that cause significant disease and mortality in both poultry and humans. While research clearly demonstrates that AIVs can move across the Pacific or Atlantic Ocean, there has been no data to support the mechanism of how this occurs. In spring and autumn of 2010 and autumn of 2011 we obtained cloacal swab samples from 1078 waterfowl, gulls, and shorebirds of various species in southwest and west Iceland and tested them for AIV. From these, we isolated and fully sequenced the genomes of 29 AIVs from wild caught gulls (Charadriiformes) and waterfowl (Anseriformes) in Iceland. We detected viruses that were entirely (8 of 8 genomic segments) of American lineage, viruses that were entirely of Eurasian lineage, and viruses with mixed American-Eurasian lineage. Prior to this work only 2 AIVs had been reported from wild birds in Iceland and only the sequence from one segment was available in GenBank. This is the first report of finding AIVs of entirely American lineage and Eurasian lineage, as well as reassortant viruses, together in the same geographic location. Our study demonstrates the importance of the North Atlantic as a corridor for the movement of AIVs between Europe and North America.

  2. Origin and fate of the North Atlantic Current at the Mid-Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Breckenfelder, Tilia; Myers, Paul G.; Rhein, Monika; Pennelly, Clark; Hu, Xianmin

    2016-04-01

    Warm, salty tropical and subtropical water is brought into the subpolar gyre by the North Atlantic Current (NAC). The NAC is the northward extension of the Gulf Stream and is part of the upper branch of the Atlantic Meridional Overturning Circulation. The warm, salty water is further transported into the Nordic Seas via the Rockall Trough, into the Denmark Strait and, finally into the Labrador Sea, where it plays an important role in the deep water formation process. On its way into the Labrador Sea the water mass increases its density by dissipating heat to the atmosphere and thereby influencing the local climate. To further understand the processes behind warm water transport towards higher latitudes, we start our investigation at the Mid-Atlantic Ridge (MAR). Here, the NAC flows from the western to eastern basin of the North Atlantic and crosses the MAR via the Charlie-Gibbs, Faraday and Maxwell Fracture Zones. The role of the subpolar and subtropical gyre on the different water masses, and their properties, originating or reaching the MAR is studied using the lagrangian tool ARIANE with the 3D velocity fields taken from a 1/12° AGRIF nest set in a regional NEMO configuration. One result of this investigation is that the majority of particles released at the MAR, distributed over the entire water column, recirculate. Most of the remaining particles make their way into the East Greenland Current or turn in the eastern basin towards the south. The influence of the North Atlantic Oscillation (NAO) is investigated by studying the pathways of the NAC and their properties during different NAO phases.

  3. 50 CFR 223.210 - North American green sturgeon.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 7 2010-10-01 2010-10-01 false North American green sturgeon. 223.210... Applicable to Threatened Marine and Anadromous Species § 223.210 North American green sturgeon. (a... endangered species apply to the threatened Southern Distinct Population Segment (DPS) of North American...

  4. 47 CFR 52.13 - North American Numbering Plan Administrator.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 3 2014-10-01 2014-10-01 false North American Numbering Plan Administrator. 52.13 Section 52.13 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) NUMBERING Administration § 52.13 North American Numbering Plan Administrator. (a) The North American Numbering Plan Administrator...

  5. Hawaiian angiosperm radiations of North American origin

    PubMed Central

    Baldwin, Bruce G.; Wagner, Warren L.

    2010-01-01

    Background Putative phytogeographical links between America (especially North America) and the Hawaiian Islands have figured prominently in disagreement and debate about the origin of Pacific floras and the efficacy of long-distance (oversea) plant dispersal, given the obstacles to explaining such major disjunctions by vicariance. Scope Review of past efforts, and of progress over the last 20 years, toward understanding relationships of Hawaiian angiosperms allows for a historically informed re-evaluation of the American (New World) contribution to Hawaiian diversity and evolutionary activity of American lineages in an insular setting. Conclusions Temperate and boreal North America is a much more important source of Hawaiian flora than suggested by most 20th century authorities on Pacific plant life, such as Fosberg and Skottsberg. Early views of evolution as too slow to account for divergence of highly distinctive endemics within the Hawaiian geological time frame evidently impeded biogeographical understanding, as did lack of appreciation for the importance of rare, often biotically mediated dispersal events and ecological opportunity in island ecosystems. Molecular phylogenetic evidence for North American ancestry of Hawaiian plant radiations, such as the silversword alliance, mints, sanicles, violets, schiedeas and spurges, underlines the potential of long-distance dispersal to shape floras, in accordance with hypotheses championed by Carlquist. Characteristics important to colonization of the islands, such as dispersibility by birds and ancestral hybridization or polyploidy, and ecological opportunities associated with ‘sky islands’ of temperate or boreal climate in the tropical Hawaiian archipelago may have been key to extensive diversification of endemic lineages of North American origin that are among the most species-rich clades of Hawaiian plants. Evident youth of flowering-plant lineages from North America is highly consistent with recent geological

  6. Summer North Atlantic Oscillation: decadal change, impact, and possible mechanisms

    NASA Astrophysics Data System (ADS)

    Sun, J.

    2010-12-01

    Summer North Atlantic Oscillation: decadal change, impact, and possible mechanisms Jianqi Sun, Huijun Wang, and Wei Yuan Nansen-Zhu International Research Centre (NZC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China. Email: sunjq@mail.iap.ac.cn It is well known that the North Atlantic Oscillation (NAO) is strong in winter, so most previous studies focused on the NAO in winter time. However, actually the NAO is also one of the teleconnection patterns that have a year-round presence. For example, some studies have indicated that the summer North Atlantic Oscillation (SNAO) is still a dominant pattern over the North Atlantic region. So it is of importance to investigate the SNAO’s variability and influences. Our recent studies revealed that the summer (SNAO) experienced a significant decadal change around the late 1970s, with the southern action center located farther eastward after the late 1970s as compared to before. Such decadal change of the SNAO pattern altered its relationship with the Northern Hemispheric summer climate. In the period before the late 1970s, the connection of the SNAO on the Northern Hemispheric land surface air temperature is weak, but after that time the impact of the SNAO is significantly enhanced. Our further analysis indicated that the decadal change of the SNAO pattern is to some extend attributed to the decadal variability of the Mediterranean-Black Sea (MBS) sea surface temperature (SST). In 1951-1975, the variability of the MBS SST is quite weak, but in 1978-2002 it becomes more active. The active MBS SST can enhance the interaction between the sea and its overlying atmosphere, thus strengthening the activity of the east part of the SNAO southern center after the late 1970s and consequently producing an eastward SNAO southern center shift. This observational analysis result is further confirmed by sensitivity experiments. Besides the MBS SST, the decadal variability of the tropical Atlantic SST

  7. Standardized North American marsh bird monitoring protocol

    USGS Publications Warehouse

    Conway, Courtney J.

    2011-01-01

    Little is known about the population status of many marsh-dependent birds in North America but recent efforts have focused on collecting more reliable information and estimates of population trends. As part of that effort, a standardized survey protocol was developed in 1999 that provided guidance for conducting marsh bird surveys throughout North America such that data would be consistent among locations. The original survey protocol has been revised to provide greater clarification on many issues as the number of individuals using the protocol has grown. The Standardized North American Marsh Bird Monitoring Protocol instructs surveyors to conduct an initial 5-minute passive point-count survey followed by a series of 1-minute segments during which marsh bird calls are broadcast into the marsh following a standardized approach. Surveyors are instructed to record each individual bird from the suite of 26 focal species that are present in their local area on separate lines of a datasheet and estimate the distance to each bird. Also, surveyors are required to record whether each individual bird was detected within each 1-minute subsegment of the survey. These data allow analysts to use several different approaches for estimating detection probability. The Standardized North American Marsh Bird Monitoring Protocol provides detailed instructions that explain the field methods used to monitor marsh birds in North America.

  8. Composition of the ancient north american crust.

    PubMed

    Condie, K C

    1967-02-24

    Geochemical studies of Wyoming Precambrian graywackes derived from continental crust older than 3.2 x 10(9) years indicate that their source area was at least as highly differentiated as most younger Precambrian crust. The composition of this early crust (approximately that of calcium-rich granite) is not unlike that of the 2.5 to 3.2 x 10(9) year old North American crust. Limited geochemical data suggest that the composition of North America may not have changed significantly during the last 3.0 to 3.5 x 10(9) years.

  9. The Evolution of North American Rhinoceroses

    NASA Astrophysics Data System (ADS)

    Prothero, Donald R.

    2005-03-01

    First appearing about 40 million years ago in North America, rhinoceroses diversified into an incredible array of taxa, with a variety of ecologies that don't resemble any of the five living species. They ranged from delicate long-legged dog-sized forms, to huge hippo-like forms that apparently lived in rivers and lakes. Including a complete systematic review, and discussions of biogeography, evolution and paleoecology, this book summarizes our current knowledge of North American rhinos and constitutes the most complete reference available.

  10. Candidates for GRL North American coeditor sought

    NASA Astrophysics Data System (ADS)

    Geophysical Research Letters (GRL), AGU's all-Union primary research journal, is seeking candidates and nominations for candidates to succeed Rob Van der Voo, whose term as North American Coeditor ends December 31, 1986. The successful candidate will be challenged to seek out interesting papers at the forefront of the geophysical sciences and to attempt to strike a balance in the publication of that science that is of interest to the entire AGU membership. While complementing the interests of Editor in Chief Alex Dessler, the successful candidate will also be challenged to maintain rapid publication time and minimize the publication of research that is routine. The North American Coeditor should be prepared to welcome controversial research papers that challenge conventional wisdom in all fields of interest to AGU. The individual selected for this prestigious position will have a vital role in making GRL an even more important and more exciting journal that readers look forward to receiving each month.

  11. Chronic liver disease in Aboriginal North Americans

    PubMed Central

    Scott, John D; Garland, Naomi

    2008-01-01

    A structured literature review was performed to detail the frequency and etiology of chronic liver disease (CLD) in Aboriginal North Americans. CLD affects Aboriginal North Americans disproportionately and is now one of the most common causes of death. Alcoholic liver disease is the leading etiology of CLD, but viral hepatitis, particularly hepatitis C, is an important and growing cause of CLD. High rates of autoimmune hepatitis and primary biliary cirrhosis (PBC) are reported in regions of coastal British Columbia and southeastern Alaska. Non-alcoholic liver disease is a common, but understudied, cause of CLD. Future research should monitor the incidence and etiology of CLD and should be geographically inclusive. In addition, more research is needed on the treatment of hepatitis C virus (HCV) infection and non-alcoholic fatty liver disease (NAFLD) in this population. PMID:18698674

  12. Do North Atlantic eels show parallel patterns of spatially varying selection?

    PubMed Central

    2014-01-01

    Background The two North Atlantic eel species, the European and the American eel, represent an ideal system in which to study parallel selection patterns due to their sister species status and the presence of ongoing gene flow. A panel of 80 coding-gene SNPs previously analyzed in American eel was used to genotype European eel individuals (glass eels) from 8 sampling locations across the species distribution. We tested for single-generation signatures of spatially varying selection in European eel by searching for elevated genetic differentiation using FST-based outlier tests and by testing for significant associations between allele frequencies and environmental variables. Results We found signatures of possible selection at a total of 11 coding-gene SNPs. Candidate genes for local selection constituted mainly genes with a major role in metabolism as well as defense genes. Contrary to what has been found for American eel, only 2 SNPs in our study correlated with differences in temperature, which suggests that other explanatory variables may play a role. None of the genes found to be associated with explanatory variables in European eel showed any correlations with environmental factors in the previous study in American eel. Conclusions The different signatures of selection between species could be due to distinct selective pressures associated with the much longer larval migration for European eel relative to American eel. The lack of parallel selection in North Atlantic eels could also be due to most phenotypic traits being polygenic, thus reducing the likelihood of selection acting on the same genes in both species. PMID:24947556

  13. Rapid subtropical North Atlantic salinity oscillations across Dansgaard-Oeschger cycles.

    PubMed

    Schmidt, Matthew W; Vautravers, Maryline J; Spero, Howard J

    2006-10-01

    Geochemical and sedimentological evidence suggest that the rapid climate warming oscillations of the last ice age, the Dansgaard-Oeschger cycles, were coupled to fluctuations in North Atlantic meridional overturning circulation through its regulation of poleward heat flux. The balance between cold meltwater from the north and warm, salty subtropical gyre waters from the south influenced the strength and location of North Atlantic overturning circulation during this period of highly variable climate. Here we investigate how rapid reorganizations of the ocean-atmosphere system across these cycles are linked to salinity changes in the subtropical North Atlantic gyre. We combine Mg/Ca palaeothermometry and oxygen isotope ratio measurements on planktonic foraminifera across four Dansgaard-Oeschger cycles (spanning 45.9-59.2 kyr ago) to generate a seawater salinity proxy record from a subtropical gyre deep-sea sediment core. We show that North Atlantic gyre surface salinities oscillated rapidly between saltier stadial conditions and fresher interstadials, covarying with inferred shifts in the Tropical Atlantic hydrologic cycle and North Atlantic overturning circulation. These salinity oscillations suggest a reduction in precipitation into the North Atlantic and/or reduced export of deep salty thermohaline waters during stadials. We hypothesize that increased stadial salinities preconditioned the North Atlantic Ocean for a rapid return to deep overturning circulation and high-latitude warming by contributing to increased North Atlantic surface-water density on interstadial transitions.

  14. Rapid subtropical North Atlantic salinity oscillations across Dansgaard-Oeschger cycles.

    PubMed

    Schmidt, Matthew W; Vautravers, Maryline J; Spero, Howard J

    2006-10-01

    Geochemical and sedimentological evidence suggest that the rapid climate warming oscillations of the last ice age, the Dansgaard-Oeschger cycles, were coupled to fluctuations in North Atlantic meridional overturning circulation through its regulation of poleward heat flux. The balance between cold meltwater from the north and warm, salty subtropical gyre waters from the south influenced the strength and location of North Atlantic overturning circulation during this period of highly variable climate. Here we investigate how rapid reorganizations of the ocean-atmosphere system across these cycles are linked to salinity changes in the subtropical North Atlantic gyre. We combine Mg/Ca palaeothermometry and oxygen isotope ratio measurements on planktonic foraminifera across four Dansgaard-Oeschger cycles (spanning 45.9-59.2 kyr ago) to generate a seawater salinity proxy record from a subtropical gyre deep-sea sediment core. We show that North Atlantic gyre surface salinities oscillated rapidly between saltier stadial conditions and fresher interstadials, covarying with inferred shifts in the Tropical Atlantic hydrologic cycle and North Atlantic overturning circulation. These salinity oscillations suggest a reduction in precipitation into the North Atlantic and/or reduced export of deep salty thermohaline waters during stadials. We hypothesize that increased stadial salinities preconditioned the North Atlantic Ocean for a rapid return to deep overturning circulation and high-latitude warming by contributing to increased North Atlantic surface-water density on interstadial transitions. PMID:17024090

  15. Simulations of Western North American Hydroclimate during the Little Ice Age and Medieval Climate Anomaly

    NASA Astrophysics Data System (ADS)

    Simon, S. M.; Mann, M. E.; Steinman, B. A.; Feng, S.; Zhang, Y.; Miller, S. K.

    2013-12-01

    Despite the immense impact that large, modern North American droughts, such as those of the 1930s and 1950s, have had on economic, social, aquacultural, and agricultural systems, they are smaller in duration and magnitude than the multidecadal megadroughts that affected North America, in particular the western United States, during the Medieval Climate Anomaly (MCA, ~ 900-1300 AD) and the Little Age (LIA, ~1450-1850 AD). Although various proxy records have been used to reconstruct the timing of these MCA and LIA megadroughts in the western United States, there still exists great uncertainty in the magnitude and spatial coherence of such droughts in the Pacific Northwest region, especially on decadal to centennial timescales. This uncertainty motivates the following study to establish a causal link between the climate forcing that induced these megadroughts and the spatiotemporal response of regional North American hydroclimates to this forcing. This study seeks to establish a better understanding of the influence of tropical Pacific and North Atlantic SSTs on North American drought during the MCA and LIA. We force NCAR's Community Atmospheric Model version 5.1.1 (CAM 5) with prescribed proxy-reconstructed tropical Pacific and North Atlantic SST anomalies from the MCA and LIA, in order to investigate the influence that these SST anomalies had on the spatiotemporal patterns of drought in North America. To isolate the effects of individual ocean basin SSTs on the North American climate system, the model experiments use a variety of SST permutations in the tropical Pacific and North Atlantic basin as external forcing. In order to quantify the spatiotemporal response of the North American climate system to these SST forcing permutations, temperature and precipitation data derived from the MCA and LIA model experiments are compared to lake sediment isotope and tree ring-based hydroclimate reconstructions from the Pacific Northwest. The spatiotemporal temperature and

  16. The North American ALMA Science Center

    NASA Astrophysics Data System (ADS)

    Lonsdale, Carol J.; Hibbard, J. E.; Staff, NAASC

    2010-01-01

    The North American ALMA Science Center at the National Radio Astronomy Observatory, NRAO, in Charlottesville, Virginia, in partnership with the Herzberg Institute of Astrophysics in Victoria, Canada, will support the North American community in their observations with the Atacama Large Millimeter Array, ALMA. Our goal is to promote successful observations with ALMA for both novice users, with no experience in either interferometry or millimeter astronomy, and experts alike. We will describe the services that the Science Center will provide for the community, from education about the capabilities of ALMA, though proposal preparation to data analysis. The Science Center will host a website with a Helpdesk that includes FAQs and a growing knowledgebase of ALMA expertise, and will support extensive demos and tutorials on observation preparation and data reduction with ALMA. The Science Center also promotes science-themed meetings. The staff of the Science Center will provide expert assistance for observers at all stages of development and execution of their program. There are visitor and postdoc opportunities at the Science Center. The North American ALMA Science Center is one of three regional centers around the globe that will support ALMA observations. Our partners are the European ALMA Regional Center at ESO in Garching, Germany, and the East Asian ALMA Region Center in Tokyo, Japan.

  17. Pb isotope signatures in the North Atlantic: initial results from the U.S. GEOTRACES North Atlantic Transect

    NASA Astrophysics Data System (ADS)

    Noble, A.; Echegoyen-Sanz, Y.; Boyle, E. A.

    2012-12-01

    This study presents Pb isotope data from the US GEOTRACES North Atlantic Transect (US-GT-NAT) sampled during two cruises that took place during Fall 2010 and 2011. Almost all of the Pb in the modern ocean is derived from anthropogenic sources, and the North Atlantic has received major Pb inputs from the United States and Europe due to emissions from leaded gasoline and high temperature industrial processes. During the past three decades, Pb fluxes to the North Atlantic have decreased following the phasing out of leaded gasoline in the United States and Europe. Following the concentrations and isotope ratios of Pb in this basin over time reveals the temporal evolution of Pb in this highly-affected basin. The Pb isotope signatures reflect the relative importance of changing inputs from the United States and Europe as leaded gasoline was phased out faster in the United States relative to Europe. In the western North Atlantic, a shallow (~100-200m) low Pb-206/Pb-207 ratio feature was observed near the Subtropical Underwater salinity peak at many stations across the transect, coincident with shallow subsurface maxima in Pb concentration. This water mass originates from high-salinity surface water near 25°N (Defant), which is in the belt of European-Pb-gas-contaminated African aerosols, which we confirmed by Pb-206/Pb-207 ~ 1.17 from upper ocean samples from US-GT-NAT station 18 (23.24degN,38.04degW). At the Mid-Atlantic Ridge station, Pb scavenging onto iron oxides and sulfide was observed by a decrease in Pb concentrations within the TAG hydrothermal plume, although the isotopic signature within the plume was slightly (~3 permil) lower than the surrounding waters possibly indicating a small contribution of hydrothermal Pb or preferential uptake of the lighter isotope. In the Mediteranean Outflow plume near Lisbon, Pb-206/Pb-207 (~1.178) is also strongly influenced by European Pb. Further results from the section will be presented as more data will be available by the

  18. Modeling Mesoscale Eddies in the North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Chao, Yi

    1999-01-01

    Ocean modeling plays an important role in understanding the current climatic conditions and predicting the future climate change. Modeling the ocean at eddy-permitting and/or eddy resolving resolutions (1/3 degree or higher) has a two-fold objective. One part is to represent the ocean as realistically as possible, because mesoscale eddies have an impact on the large-scale circulation. The second objective is to learn how to represent effects of mesoscale eddies without explicitly resolving them. This is particularly important for climate models which cannot be run at eddy-resolving resolutions because of the computational constraints. At JPL, a 1/6 degree latitude by 1/6 degree longitude with 37 vertical levels Atlantic Ocean model has been developed. The model is based on the Parallel Ocean Program (POP) developed at Los Alamos National Laboratory (LANL). Using the 256-processor Cray T3D, we have conducted a 40-year integration of this Atlantic eddy-resolving ocean model. A regional analysis demonstrate that many observed features associated with the Caribbean Sea eddies can be realistically simulated by this model. Analysis of this Atlantic eddy-resolving ocean model further suggests that these Caribbean Sea eddies are connected with eddies formed outside the Caribbean Sea at the confluence of the North Brazil Current (NBC) and the North Equatorial Countercurrent. The diagram of the model simulated surface current shows that the Caribbean eddies ultimately originate in the NBC retroflection region, traveling more than a year from the North Brazil coast through the Lesser Antilles into the Caribbean Sea and eventually into the Gulf of Mexico. Additional information is contained in the original.

  19. Surface Salinity Variability in the North Atlantic During Recent Decades

    NASA Technical Reports Server (NTRS)

    Haekkinen, Sirpa

    2001-01-01

    The sea surface salinity (SSS) variability in the North Atlantic is investigated using numerical model simulations for the last 50 years based on atmospheric forcing variability from Comprehensive Atmosphere Ocean Data Set (COADS) and National Center for Environmental Prediction / National Center for Atmospheric Research (NCEP/NCAR) Reanalysis. The largest interannual and longer term variability occurs in two regions: the Labrador Sea and the North Equatorial Countercurrent (NECC) region. In both regions the seasonality of the surface salinity variability is prominent with the maximum standard deviation occurring in the summer/fall period. In the Labrador Sea the summer SSS anomalies far exceed those of wintertime in amplitude. The interannual SSS variability in the subpolar gyre can be attributed to two factors: excess ice melt and heat flux (i.e. deep mixing) variations. On the other hand, heat flux variability can also lead to meridional overturning changes on decadal time scales such that weak overturning is manifested in fresh surface conditions in the subpolar gyre. The overturning changes also influence the NECC region SSS variability. Moreover, the subpolar freshening events are expected to occur during the negative phase of North Atlantic Oscillation which is associated with a weak wintertime surface heat loss in the subpolar gyre. No excess sea ice melt or precipitation is necessary for the formation of the fresh anomalies, because with the lack of wide-spread deep mixing, the fresh water that would be expected based on climatology, would accumulate at the surface. Thus, the fresh water 'conveyor' in the Atlantic operates via the overturning circulation such that deep mixing inserts fresh water while removing heat from the water column.

  20. The JGOFS North Atlantic Bloom Experiment: An overview

    NASA Technical Reports Server (NTRS)

    Ducklow, Hugh W.

    1992-01-01

    The North Atlantic Bloom Experiment (NABE) of JGOFS presents a unique opportunity and challenge to the data management community because of the diversity and large size of biogeochemical data sets collected. NABE was a pilot study for JGOFS and has also served as a pilot study within the U.S. NODC for management and archiving of the data sets. Here I present an overview to some of the scientific results of NABE, which will be published as an Introduction to a special volume of NABE results in Deep-Sea Research later this year. An overview of NABE data management is given elsewhere in the present report. This is the first collection of papers from the Joint Global Ocean Flux Study (JGOFS). Formed as an international program in 1987, JGOFS has four principal elements: modelling and data management, multidisciplinary regional process studies, a global survey of biogeochemical properties and long-term time series observatories. In 1989-1990 JGOFS conducted a pilot process study of the spring phytoplankton bloom, the North Atlantic Bloom Experiment (NABE). JGOFS decided to conduct a large scale, internationally-coordinated pilot study in the North Atlantic because of its proximity to the founding nations of the project, the size and predictability of the bloom and its fundamental impact on ocean bio-geochemistry (Billett et al., 1983; Watson and Whitfield, 1985; Pfannkuche, 1992). In 1989, six research vessels from Canada, Germany, The Netherlands, the United Kingdom and the USA and over 200 scientists and students from more than a dozen nations participated in NABE. Some of their initial results are reported in this volume.

  1. Isohaline Salinity Budget of the North Atlantic Salinity Maximum

    NASA Astrophysics Data System (ADS)

    Bryan, F.; Bachman, S.

    2014-12-01

    The Salinity Processes in the Upper Ocean Regional Study (SPURS) field experiment was designed as a multi-scale investigation of the processes that give rise to the North Atlantic subtropical salinity maximum. The choice of control volume influences the processes that dominate budgets of ocean properties. In this study we analyze the salinity budget of the North Atlantic subtropical salinity maximum region for control volumes bounded by isohaline surfaces. We provide closed budgets based on output from a high-resolution numerical simulation, and partial budgets based on climatological analyses of observations. With this choice of control volume, advection is eliminated from the instantaneous volume integrated salt budget, and time mean advection eliminated from the budget evaluated from time-averaged data. In this way, the role of irreversible mixing processes in the maintenance and variability of the salinity maximum are more readily revealed. By carrying out the analysis with near instantaneous and time-filtered model output, the role of mesoscale eddies in stirring and mixing for this region is determined. We find that the small-scale mixing acting on enhanced gradients generated by the mesoscale eddies is approximately equal to that acting on the large-scale gradients estimated from climatological mean conditions. The isohaline salinity budgets can be related to water mass transformation rates associated with surface forcing and mixing processes in a straightforward manner. We find that the surface net evaporation in the North Atlantic salinity maximum region accounts for a transformation of 7 Sv of water into the salinity maximum in the simulation, whereas the estimate based on climatological observations is 10 Sv.

  2. The spatial distribution and evolution characteristics of North Atlantic cyclones

    NASA Astrophysics Data System (ADS)

    Dacre, H.; Gray, S.

    2009-09-01

    Mid-latitude cyclones play a large role in determining the day-to-day weather conditions in western Europe through their associated wind and precipitation patterns. Thus, their typical spatial and evolution characteristics are of great interest to meteorologists, insurance and risk management companies. In this study a feature tracking algorithm is applied to a cyclone database produced using the Hewson-method of cyclone identification, based on low-level gradients of wet-bulb potential temperature, to produce a climatology of mid-latitude cyclones. The aim of this work is to compare the cyclone track and density statistics found in this study with previous climatologies and to determine reasons for any differences. This method is found to compare well with other cyclone identification methods; the north Atlantic storm track is reproduced along with the major regions of genesis. Differences are attributed to cyclone lifetime and strength thresholds, dataset resolution and cyclone identification and tracking methods. Previous work on cyclone development has been largely limited to case studies as opposed to analysis of climatological data, and does not distinguish between the different stages of cyclone evolution. The cyclone database used in this study allows cyclone characteristics to be tracked throughout the cyclone lifecycle. This enables the evaluation of the characteristics of cyclone evolution for systems forming in different genesis regions and a calculation of the spatial distribution and evolution of these characteristics in composite cyclones. It was found that most of the cyclones that cross western Europe originate in the east Atlantic where the baroclinicity and sea surface temperature gradients are weak compared to the west Atlantic. East Atlantic cyclones also have higher low-level relative vorticity and lower mean sea level pressure at their genesis point than west Atlantic cyclones. This is consistent with the hypothesis that they are secondary

  3. The spatial distribution and evolution characteristics of North Atlantic cyclones

    NASA Astrophysics Data System (ADS)

    Dacre, H.; Gray, S.

    2009-04-01

    Mid-latitude cyclones play a large role in determining the day-to-day weather conditions in western Europe through their associated wind and precipitation patterns. Thus, their typical spatial and evolution characteristics are of great interest to meteorologists, insurance and risk management companies. In this study a feature tracking algorithm is applied to a cyclone database produced using the Hewson-method of cyclone identification, based on low-level gradients of wet-bulb potential temperature, to produce a climatology of mid-latitude cyclones. The aim of this work is to compare the cyclone track and density statistics found in this study with previous climatologies. This method is found to compare well with other cyclone identification methods; the north Atlantic storm track is reproduced along with the major regions of genesis. Differences are attributed to cyclone lifetime and strength thresholds, dataset resolution and cyclone identification and tracking methods. Previous work on cyclone development has been largely limited to case studies as opposed to analysis of climatological data, and does not distinguish between the different stages of cyclone evolution. The cyclone database used in this study allows cyclone characteristics to be tracked throughout the cyclone lifecycle. This enables the evaluation of the characteristics of cyclone evolution for systems forming in different genesis regions and a calculation of the spatial distribution and evolution of these characteristics in composite cyclones. It was found that most of the cyclones that cross western Europe originate in the east Atlantic where the baroclinicity and sea surface temperature gradients are weak compared to the west Atlantic. East Atlantic cyclones also have higher low-level relative vorticity and lower mean sea level pressure at their genesis point than west Atlantic cyclones. This is consistent with the hypothesis that they are secondary cyclones developing on the trailing fronts of

  4. Borrelia garinii in Seabird Ticks (Ixodes uriae), Atlantic Coast, North America

    PubMed Central

    Muzaffar, Sabir Bin; Lavers, Jennifer; Lacombe, Eleanor H.; Cahill, Bruce K.; Lubelczyk, Charles B.; Kinsler, Allen; Mathers, Amy J.; Rand, Peter W.

    2006-01-01

    Borrelia garinii is the most neurotropic of the genospecies of B. burgdorferi sensu lato that cause Lyme disease in Europe, where it is transmitted to avian and mammalian reservoir hosts and to humans by Ixodes ricinus. B. garinii is also maintained in an enzootic cycle in seabirds by I. uriae, a tick found at high latitudes in both the Northern and Southern Hemispheres. To determine whether B. garinii is present in seabird ticks on the Atlantic Coast of North America, we examined 261 I. uriae ticks by polyclonal antiborrelial fluorescent antibody. Ten of 61 ticks from Gull Island, Newfoundland, were positive for borreliae by this screen. Amplicons of DNA obtained by PCR that targeted the B. garinii rrs-rrla intergenic spacer were sequenced and matched to GenBank sequences for B. garinii. The potential for introduction of this agent into the North American Lyme disease enzootic is unknown. PMID:17326943

  5. A high resolution salinity time series 1993-2012 in the North Atlantic from Argo and Altimeter data

    NASA Astrophysics Data System (ADS)

    Stendardo, I.; Rhein, M.; Hollmann, R.

    2016-04-01

    The study of salinity changes has been hampered by the lack of temporal and spatial resolution of the observations. In order to improve the spatial and temporal distribution of salinity observations, we used the Gravest Empirical Mode (GEM) technique to calculate high-resolution salinity distributions as a function of dynamic height for the period 1993-2012. This technique combined Argo and altimeter data to exploit the relationship between T/S profiles and dynamic height in the North Atlantic. The method was valid in the upper 700 m mainly at and near the pathways of the North Atlantic Current (NAC), but failed in regions with weak stratification or with ambiguities in the T/S relationships. Coherent, multiannual large-scale variability was observed, with many features present in all regions, albeit with weaker amplitudes in the eastern basins. Some of the interannual features in the northeastern Atlantic basins were unrelated to the variability further south and west, pointing to an occasional advection of subtropical water in the eastern Atlantic. Origin and advection of salinity anomalies with the NAC from the North American Basin into the western subpolar North Atlantic are correlated with the state of the North Atlantic Oscillation (NAO) and dampened by the surface freshwater fluxes. Other mechanisms influencing the salinity pattern are the changing location of the subpolar front, also related to the NAO. The large multiyear variability in the 20 year time series obscured any potential trends caused by global warming. Only the Rockall Trough showed a salinity increase of 0.03 per decade.

  6. North Atlantic Ocean drivers of the 2015 European heat wave

    NASA Astrophysics Data System (ADS)

    Duchez, Aurélie; Frajka-Williams, Eleanor; Josey, Simon A.; Hirschi, Joël; Evans, Gwyn

    2016-04-01

    Major European heat waves have occurred on several occasions in the past two decades, including the summer of 2015, with dramatic socioeconomic impacts and in a globally warming world, heat waves are expected to become longer, more frequent and more intense. Nevertheless, our understanding of heat wave causes remains at a basic level, limiting the usefulness of event prediction. We show that 2015 was the most extreme heat wave in central Europe in the past 35 years. We find that the heat wave was preceded by cold mid-latitude North Atlantic Ocean surface temperatures, which contributed to its development. In order to explain the genesis of the cold ocean anomaly, we consider surface heat loss, ocean heat content and wind driven upwelling. The anomaly is primarily due to extreme ocean heat loss in the preceding two winters and re-emergent cold ocean water masses. Further analysis indicates that this ocean anomaly was a driver for the 2015 heat wave as it favoured a stationary position of the Jet Stream, which steered Atlantic cyclones away from central Europe towards northern Europe. The cold Atlantic anomaly was also present during the most devastating European heat waves since the 1980s indicating that it is a common factor in the development of these extreme events.

  7. Cetaceans of the Atlantic Frontier, north and west of Scotland

    NASA Astrophysics Data System (ADS)

    Weir, C. R.; Pollock, C.; Cronin, C.; Taylor, S.

    2001-05-01

    Surveys carried out to the north and west of Scotland have recorded 15 species of cetacean between 1979 and 1998. These were fin whale ( Balaenoptera physalus) , sei whale ( B. borealis) , minke whale ( B. acutorostrata) , humpback whale ( Megaptera novaeangliae) , sperm whale ( Physeter macrocephalus) , northern bottlenose whale ( Hyperoodon ampullatus) , Sowerby's beaked whale ( Mesoplodon bidens) , killer whale ( Orcinus orca) , long-finned pilot whale ( Globicephala melas) , Atlantic white-sided dolphin ( Lagenorhynchus acutus) , white-beaked dolphin ( L. albirostris) , Risso's dolphin ( Grampus griseus) , bottlenose dolphin ( Tursiops truncatus) , common dolphin ( Delphinus delphis) and harbour porpoise ( Phocoena phocoena) . Atlantic white-sided dolphin was the most abundant species in the region with a total of 6317 animals recorded. Harbour porpoise was the most frequently sighted cetacean species. The geographical distribution of sightings indicate that cetacean species have varying ecological requirements, with species such as sperm whale, pilot whale and white-sided dolphin favouring deep water off the continental shelf edge, while minke whale, white-beaked dolphin and harbour porpoise were apparently limited to the continental shelf. The diversity of species recorded in the region suggests that the Atlantic Frontier is an important habitat for cetaceans.

  8. The North Atlantic Oscillation: Climatic Significance and Environmental Impact

    NASA Astrophysics Data System (ADS)

    Hurrell, James W.; Kushnir, Yochanan; Ottersen, Geir; Visbeck, Martin

    Over the middle and high latitudes of the Northern Hemisphere the most prominent and recurrent pattern of atmospheric variability is the North Atlantic Oscillation (NAO). The NAO refers to swings in the atmospheric sea level pressure difference between the Arctic and the subtropical Atlantic that are most noticeable during the boreal cold season (November-April) and are associated with changes in the mean wind speed and direction. Such changes alter the seasonal mean heat and moisture transport between the Atlantic and the neighboring continents, as well as the intensity and number of storms, their paths, and their weather. Significant changes in ocean surface temperature and heat content, ocean currents and their related heat transport, and sea ice cover in the Arctic and sub-Arctic regions are also induced by changes in the NAO. Such climatic fluctuations affect agricultural harvests, water management, energy supply and demand, and fisheries yields. All these effects have led to many studies of the phenomenon; yet, despite this interest, unanswered questions remain regarding the climatic processes that govern NAO variability, how the phenomenon has varied in the past or will vary in the future, and whether it is at all predictable.

  9. D″ discontinuity structure beneath the North Atlantic from Scd observations

    NASA Astrophysics Data System (ADS)

    Yao, Yao; Whittaker, Stefanie; Thorne, Michael S.

    2015-05-01

    We analyzed transverse and radial component recordings from the 2010 M6.3 southern Spain earthquake (depth = 620 km) recorded on 370 broadband stations in North America. We grouped these seismograms into subarrays and applied fourth root vespa processing (vespagram analysis) in order to enhance low-amplitude arrivals. These vespagrams show clear Scd arrivals which indicate the existence of the D″ discontinuity beneath the North Atlantic Ocean (45-60°N, 45-55°W). These observations are best fit with a +2-4% velocity increase at the top of the D″ discontinuity at a height above the core-mantle boundary of 304 ± 14 km. We do not observe Scd arrivals at the eastern end of our study region which is consistent with the presence of the easternmost edge of the ancient Farallon plate.

  10. Holocene history of drift ice in the northern North Atlantic: Evidence for different spatial and temporal modes

    USGS Publications Warehouse

    Moros, M.; Andrews, John T.; Eberl, D.D.; Jansen, E.

    2006-01-01

    We present new high-resolution proxy data for the Holocene history of drift ice off Iceland based on the mineralogy of the <2-mm sediment fraction using quantitative X-ray diffraction. These new data, bolstered by a comparison with published proxy records, point to a long-term increasing trend in drift ice input into the North Atlantic from 6 to 5 ka toward the present day at sites influenced by the cold east Greenland Current. This feature reflects the late Holocene Neoglacial or cooling period recorded in ice cores and further terrestrial archives on Greenland. In contrast, a decrease in drift ice during the same period is recorded at sites underlying the North Atlantic Drift, which may reflect a warming of this region. The results document that Holocene changes in iceberg rafting and sea ice advection did not occur uniformly across the North Atlantic. Centennial-scale climate variability in the North Atlantic region over the last ???4 kyr is linked to the observed changes in drift ice input. Increased drift ice may have played a role in the increase of cold intervals during the late Holocene, e.g., the Little Ice Age cooling. Copyright 2006 by the American Geophysical Union.

  11. Pliocene planktic foraminifer census data from the North Atlantic region

    USGS Publications Warehouse

    PRISM Project Members

    1996-01-01

    INTRODUCTION: The U.S. Geological Survey is conducting a long-term study of the climatic and oceanographic conditions of the Pliocene known as PRISM (Pliocene Research, Interpretation, and Synoptic Mapping). One of the major elements of the study involves the use of quantitative composition of planktic foraminifer assemblages to estimate seasurface temperatures and identify major oceanographic boundaries and water masses (Dowsett, 1991; Dowsett and Poore, 1991; Dowsett et al., 1992; Dowsett et al., 1994). We have analyzed more than 900 samples from 19 core sites in the North Atlantic Basin (Fig. 1) resulting in a large volume of raw census data. These data are presented here together to facilitate comparison of North Atlantic faunal assemblages. Latitude, longitude, water depth, source of faunal data and source of data used to construct age model (or publication from which age model was taken) are provided for each locality in Table 1. All ages refer to the geomagnetic polarity time scale of Berggren et al. (1985). Counts of species tabulated in each sample are given in Tables 2-20. DSDP and ODP sample designations are abbreviated in Tables 2-20 as core-section, depth within section in centimeters (eg. 10-5, 34 = core 10, section 5, 34 cm below top of section 5).

  12. Hindcasts of Integrated Kinetic Energy in North Atlantic Tropical Cyclones

    NASA Astrophysics Data System (ADS)

    Kozar, Michael; Misra, Vasubandhu

    2015-04-01

    Integrated kinetic energy (IKE) is a recently developed metric that evaluates the destructive potential of a tropical cyclone by assessing the size and strength of its wind field. Despite the potential usefulness of the IKE metric, there are few, if any, operational tools that are specifically designed to forecast IKE in real-time. Therefore, a system of artificial neural networks is created to produce deterministic and probabilistic projections of IKE in North Atlantic tropical cyclones out to 72 hours from a series of relevant environmental and storm specific normalized input parameters. In an effort to assess its real-time skill, this IKE forecasting system is run in a mock-operational mode for the 1990 to 2011 North Atlantic hurricane seasons. Hindcasts of IKE are produced in this manner by running the neural networks with hindcasted input parameters from NOAA's second generation Global Ensemble Forecasting System reforecast dataset. Ultimately, the results of the hindcast exercises indicate that the neural network system is capable of skillfully forecasting IKE in an operational setting at a level significantly higher than climatology and persistence. Ultimately, forecasts of IKE from these neural networks could potentially be an asset for operational meteorologists that would complement existing forecast tools in an effort to better assess the damage potential of landfalling tropical cyclones, particularly with regards to storm surge damage.

  13. Reevaluation of mid-Pliocene North Atlantic sea surface temperatures

    USGS Publications Warehouse

    Robinson, Marci M.; Dowsett, Harry J.; Dwyer, Gary S.; Lawrence, Kira T.

    2008-01-01

    Multiproxy temperature estimation requires careful attention to biological, chemical, physical, temporal, and calibration differences of each proxy and paleothermometry method. We evaluated mid-Pliocene sea surface temperature (SST) estimates from multiple proxies at Deep Sea Drilling Project Holes 552A, 609B, 607, and 606, transecting the North Atlantic Drift. SST estimates derived from faunal assemblages, foraminifer Mg/Ca, and alkenone unsaturation indices showed strong agreement at Holes 552A, 607, and 606 once differences in calibration, depth, and seasonality were addressed. Abundant extinct species and/or an unrecognized productivity signal in the faunal assemblage at Hole 609B resulted in exaggerated faunal-based SST estimates but did not affect alkenone-derived or Mg/Ca–derived estimates. Multiproxy mid-Pliocene North Atlantic SST estimates corroborate previous studies documenting high-latitude mid-Pliocene warmth and refine previous faunal-based estimates affected by environmental factors other than temperature. Multiproxy investigations will aid SST estimation in high-latitude areas sensitive to climate change and currently underrepresented in SST reconstructions.

  14. Blue whale (Balaenoptera musculus) sounds from the North Atlantic

    NASA Astrophysics Data System (ADS)

    Mellinger, David K.; Clark, Christopher W.

    2003-08-01

    Sounds of blue whales were recorded from U.S. Navy hydrophone arrays in the North Atlantic. The most common signals were long, patterned sequences of very-low-frequency sounds in the 15-20 Hz band. Sounds within a sequence were hierarchically organized into phrases consisting of one or two different sound types. Sequences were typically composed of two-part phrases repeated every 73 s: a constant-frequency tonal ``A'' part lasting approximately 8 s, followed 5 s later by a frequency-modulated ``B'' part lasting approximately 11 s. A common sequence variant consisted only of repetitions of part A. Sequences were separated by silent periods averaging just over four minutes. Two other sound types are described: a 2-5 s tone at 9 Hz, and a 5-7s inflected tone that swept up in frequency to ca. 70 Hz and then rapidly down to 25 Hz. The general characteristics of repeated sequences of simple combinations of long-duration, very-low-frequency sound units repeated every 1-2 min are typical of blue whale sounds recorded in other parts of the world. However, the specific frequency, duration, and repetition interval features of these North Atlantic sounds are different than those reported from other regions, lending further support to the notion that geographically separate blue whale populations have distinctive acoustic displays.

  15. Blue whale (Balaenoptera musculus) sounds from the North Atlantic.

    PubMed

    Mellinger, David K; Clark, Christopher W

    2003-08-01

    Sounds of blue whales were recorded from U.S. Navy hydrophone arrays in the North Atlantic. The most common signals were long, patterned sequences of very-low-frequency sounds in the 15-20 Hz band. Sounds within a sequence were hierarchically organized into phrases consisting of one or two different sound types. Sequences were typically composed of two-part phrases repeated every 73 s: a constant-frequency tonal "A" part lasting approximately 8 s, followed 5 s later by a frequency-modulated "B" part lasting approximately 11 s. A common sequence variant consisted only of repetitions of part A. Sequences were separated by silent periods averaging just over four minutes. Two other sound types are described: a 2-5 s tone at 9 Hz, and a 5-7 s inflected tone that swept up in frequency to ca. 70 Hz and then rapidly down to 25 Hz. The general characteristics of repeated sequences of simple combinations of long-duration, very-low-frequency sound units repeated every 1-2 min are typical of blue whale sounds recorded in other parts of the world. However, the specific frequency, duration, and repetition interval features of these North Atlantic sounds are different than those reported from other regions, lending further support to the notion that geographically separate blue whale populations have distinctive acoustic displays.

  16. Solar forcing synchronizes decadal North Atlantic climate variability.

    PubMed

    Thiéblemont, Rémi; Matthes, Katja; Omrani, Nour-Eddine; Kodera, Kunihiko; Hansen, Felicitas

    2015-01-01

    Quasi-decadal variability in solar irradiance has been suggested to exert a substantial effect on Earth's regional climate. In the North Atlantic sector, the 11-year solar signal has been proposed to project onto a pattern resembling the North Atlantic Oscillation (NAO), with a lag of a few years due to ocean-atmosphere interactions. The solar/NAO relationship is, however, highly misrepresented in climate model simulations with realistic observed forcings. In addition, its detection is particularly complicated since NAO quasi-decadal fluctuations can be intrinsically generated by the coupled ocean-atmosphere system. Here we compare two multi-decadal ocean-atmosphere chemistry-climate simulations with and without solar forcing variability. While the experiment including solar variability simulates a 1-2-year lagged solar/NAO relationship, comparison of both experiments suggests that the 11-year solar cycle synchronizes quasi-decadal NAO variability intrinsic to the model. The synchronization is consistent with the downward propagation of the solar signal from the stratosphere to the surface. PMID:26369503

  17. Early Oligocene initiation of North Atlantic Deep Water formation

    NASA Astrophysics Data System (ADS)

    Davies, Richard; Cartwright, Joseph; Pike, Jennifer; Line, Charles

    2001-04-01

    Dating the onset of deep-water flow between the Arctic and North Atlantic oceans is critical for modelling climate change in the Northern Hemisphere and for explaining changes in global ocean circulation throughout the Cenozoic era (from about 65 million years ago to the present). In the early Cenozoic era, exchange between these two ocean basins was inhibited by the Greenland-Scotland ridge, but a gateway through the Faeroe-Shetland basin has been hypothesized. Previous estimates of the date marking the onset of deep-water circulation through this basin-on the basis of circumstantial evidence from neighbouring basins-have been contradictory, ranging from about 35 to 15 million years ago. Here we describe the newly discovered Southeast Faeroes drift, which extends for 120km parallel to the basin axis. The onset of deposition in this drift has been dated to the early Oligocene epoch (~35 million years ago) from a petroleum exploration borehole. We show that the drift was deposited under a southerly flow regime, and conclude that the initiation of deep-water circulation from the Norwegian Sea into the North Atlantic Ocean took place much earlier than is currently assumed in most numerical models of ancient ocean circulation.

  18. Early Oligocene initiation of North Atlantic Deep Water formation.

    PubMed

    Davies, R; Cartwright, J; Pike, J; Line, C

    2001-04-19

    Dating the onset of deep-water flow between the Arctic and North Atlantic oceans is critical for modelling climate change in the Northern Hemisphere and for explaining changes in global ocean circulation throughout the Cenozoic era (from about 65 million years ago to the present). In the early Cenozoic era, exchange between these two ocean basins was inhibited by the Greenland-Scotland ridge, but a gateway through the Faeroe-Shetland basin has been hypothesized. Previous estimates of the date marking the onset of deep-water circulation through this basin-on the basis of circumstantial evidence from neighbouring basins-have been contradictory, ranging from about 35 to 15 million years ago. Here we describe the newly discovered Southeast Faeroes drift, which extends for 120 km parallel to the basin axis. The onset of deposition in this drift has been dated to the early Oligocene epoch ( approximately 35 million years ago) from a petroleum exploration borehole. We show that the drift was deposited under a southerly flow regime, and conclude that the initiation of deep-water circulation from the Norwegian Sea into the North Atlantic Ocean took place much earlier than is currently assumed in most numerical models of ancient ocean circulation. PMID:11309613

  19. North Atlantic Oscillation records in Siberian tree rings

    NASA Astrophysics Data System (ADS)

    Sidorova, Olga; Saurer, Matthias; Siegwolf, Rolf

    2010-05-01

    Changes in the Eurasian subarctic like temperature increase, thawing of permafrost, changes in seasonality (shifting of the beginning of the growth period), and changes in the amount of precipitations are linked to a positive phase of North Atlantic Oscillation (NAO) in recent decades. We report about the response of larch trees to climatic changes in the eastern Taimyr (Central Siberia) and northeastern Yakutia (Eastern Siberia) at high latitudes during the last century using tree ring width, latewood density and stable isotope wood and cellulose (δ13C, δ18O) chronologies. Not only the summer months were related to the carbon and oxygen isotope variations. The positive relationship, which was found between February temperature and δ18O of cellulose for northeastern Yakutia and the negative correlations between the temperature of February and δ13C of wood and cellulose for eastern Taimyr, could be explained by the influence of North Atlantic Oscillation. This work was supported by Swiss National Science Foundation SNF 200021_121838/1 and RFBR_sibir 09-05-98015.

  20. North Atlantic Storm Activity During the Younger Dryas

    NASA Astrophysics Data System (ADS)

    Toomey, M.

    2015-12-01

    The risks posed to cities along the Eastern Seaboard by a potential intensification of tropical cyclone activity over the coming decades remain poorly constrained, in part, due to a lack of available storm proxy records that extend beyond the relatively stable climates of the late Holocene. Previous work in the Bahamas shows that coarse-grained, high-energy event layers in carbonate bank margin sediments: (1) closely track recent historic hurricane events and (2) that the sensitivity of this proxy may be less affected by the deglacial changes in sea level that have limited our ability to reconstruct past hurricane activity using overwash records from back-barrier beach settings. Here we present a record of storm triggered turbidite deposition from a suite of well dated (e.g. Lynch-Stieglitz et al., 2011, Paleoceanography) jumbo piston cores taken offbank (300-500 mbsl) the Dry Tortugas, Florida, that spans abrupt transitions in North Atlantic sea surface temperature and thermohaline circulation during the Younger Dryas (12.9 - 11.5 kyr BP). This record, along with General Circulation Model output (TraCE: NCAR-CGD), indicates strong hurricane activity may have occurred along Southeastern US coasts through this interval despite considerably colder North Atlantic SSTs.

  1. North Atlantic salinity as a predictor of Sahel rainfall

    PubMed Central

    Li, Laifang; Schmitt, Raymond W.; Ummenhofer, Caroline C.; Karnauskas, Kristopher B.

    2016-01-01

    Water evaporating from the ocean sustains precipitation on land. This ocean-to-land moisture transport leaves an imprint on sea surface salinity (SSS). Thus, the question arises of whether variations in SSS can provide insight into terrestrial precipitation. This study provides evidence that springtime SSS in the subtropical North Atlantic ocean can be used as a predictor of terrestrial precipitation during the subsequent summer monsoon in Africa. Specifically, increased springtime SSS in the central to eastern subtropical North Atlantic tends to be followed by above-normal monsoon-season precipitation in the African Sahel. In the spring, high SSS is associated with enhanced moisture flux divergence from the subtropical oceans, which converges over the African Sahel and helps to elevate local soil moisture content. From spring to the summer monsoon season, the initial water cycling signal is preserved, amplified, and manifested in excessive precipitation. According to our analysis of currently available soil moisture data sets, this 3-month delay is attributable to a positive coupling between soil moisture, moisture flux convergence, and precipitation in the Sahel. Because of the physical connection between salinity, ocean-to-land moisture transport, and local soil moisture feedback, seasonal forecasts of Sahel precipitation can be improved by incorporating SSS into prediction models. Thus, expanded monitoring of ocean salinity should contribute to more skillful predictions of precipitation in vulnerable subtropical regions, such as the Sahel. PMID:27386525

  2. North Atlantic salinity as a predictor of Sahel rainfall.

    PubMed

    Li, Laifang; Schmitt, Raymond W; Ummenhofer, Caroline C; Karnauskas, Kristopher B

    2016-05-01

    Water evaporating from the ocean sustains precipitation on land. This ocean-to-land moisture transport leaves an imprint on sea surface salinity (SSS). Thus, the question arises of whether variations in SSS can provide insight into terrestrial precipitation. This study provides evidence that springtime SSS in the subtropical North Atlantic ocean can be used as a predictor of terrestrial precipitation during the subsequent summer monsoon in Africa. Specifically, increased springtime SSS in the central to eastern subtropical North Atlantic tends to be followed by above-normal monsoon-season precipitation in the African Sahel. In the spring, high SSS is associated with enhanced moisture flux divergence from the subtropical oceans, which converges over the African Sahel and helps to elevate local soil moisture content. From spring to the summer monsoon season, the initial water cycling signal is preserved, amplified, and manifested in excessive precipitation. According to our analysis of currently available soil moisture data sets, this 3-month delay is attributable to a positive coupling between soil moisture, moisture flux convergence, and precipitation in the Sahel. Because of the physical connection between salinity, ocean-to-land moisture transport, and local soil moisture feedback, seasonal forecasts of Sahel precipitation can be improved by incorporating SSS into prediction models. Thus, expanded monitoring of ocean salinity should contribute to more skillful predictions of precipitation in vulnerable subtropical regions, such as the Sahel. PMID:27386525

  3. Saharan dust enhances carbon sequestration in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Pabortsava, Katsiaryna; Lampitt, Richard; Le Moigne, Frederic; Sanders, Richard; Statham, Peter

    2016-04-01

    We present unique time-series data from sediment traps deployed at 3000 m depth in the subtropical North (NOG) and South (SOG) Atlantic oligotrophic gyres during 2007-2010. The sampling sites have similar physical properties and carbon fixation rates but different surface ocean biogeochemistry owing to enhanced input of Saharan dust in the North. NOG and SOG sites are thus ideal to investigate the effects of dust input on carbon sequestration in low-nutrient low-chlorophyll oceans. Analyses of the trap material (chemical, microscopic and stable isotope) revealed significant inter-basin differences in the downward particle flux and its composition, showing that biogeochemical differences at the surface have major effects on deep ocean sequestration scenarios. Particulate organic carbon flux in the dustier Northern gyre was twice that in the dust-poor Southern gyre. We conclude that this is a consequence of tight coupling between fertilization and ballasting due to dust deposition. We suggest that excess of micronutrient Fe from the dust increased phytoplankton biomass by stimulating di-nitrogen fixation, while dust particles caused rapid and more efficient transport to depth via ballasting. These findings present compelling direct evidence of two distinct biogeochemical provinces in the subtropical oligotrophic Atlantic not only with respect to surface nutrient biogeochemistry but also with respect to carbon sequestration.

  4. On the Prediction of North Atlantic CATEGORY-5 Hurricans

    NASA Astrophysics Data System (ADS)

    Zapotitla Rpman, J.; Juarez-Zuñiga, A.; Pérez-Peraza, J. A.

    2013-05-01

    Category-5 Hurricanes are the most devastating from the standpoint of human and economic losses. To minimize such damages we propose here a method to predict those kinds of hurricanes. We consider north Atlantic category-5 hurricanes since 1920. Data was transformed into a series of Pulses with unitary value at the dates of hurricanes occurrence and 0 for dates of no occurrence. Under the hypothesis that the occurrence of hurricanes of this category behave in a sinusoidal manner we can define the dominant periods of oscillation and establish correspondence rules that delimit the occurrence of the next hurricane. By means of the Wavelet transform we determine the dominant oscillation periods and we search for associations between the hurricanes occurrence and the behavior of the harmonics. The Wavelet Power Spectrum yields the following periodicities 2, 9, 14 and 24 yrs. The 24 years periodicity divides exactly the events in four groups, where we observe that each of the periodicities have a similar peculiar behavior through all the four groups. According to the behavior of the harmonics it is found that their combination restricts regions of probability of Hurricane occurrence. Interpolation of this sinusoidal behavior allows for a good reconstruction of past Hurricanes dates as well as extrapolation to the future. In this way we conclude that there is a good probability that the next category-5 Hurricane in the north Atlantic occurs in the course of this year.

  5. Reconstruction of the North Atlantic Oscillation, 1429-1983

    NASA Astrophysics Data System (ADS)

    Glueck, Mary F.; Stockton, Charles W.

    2001-10-01

    The North Atlantic Oscillation (NAO) is considered to be the dominant mode of winter atmospheric variability in the Northern Hemisphere (Barnston AG, Livezey RE. 1987. Classification, seasonality and persistence of low frequency atmospheric circulation patterns. Monthly Weather Review 115: 1083-1126), especially in the North Atlantic region. A better understanding of its recent variability in the context of pre-instrumental period variations is critical for prediction purposes. A 555-year (1429-1983) multi-proxy reconstruction of the cool season NAO, calibrated against the Lisbon-Iceland (LISJHI) NAO, is presented. Predictor variables include tree-ring chronologies from Morocco and Finland, GISP2 18O annual series, and a GISP2 snow accumulation record. Although the reconstructed values are generally lower than the instrumental values during the calibration period (1863-1983), the final reconstruction does capture the low frequency of the instrumental NAO. The reconstruction compares favourably with existing shorter NAO reconstructions and with the instrumental NAO. The variability in the reconstructed NAO is also discussed within the context of lengthy regional climate records. Results suggest that the occurrence and length of the recent persistently high phase of the NAO are not unusual over the 555-year period of time, but that the magnitude of some of the instrumental values may, in fact, be unique.

  6. Solar forcing synchronizes decadal North Atlantic climate variability.

    PubMed

    Thiéblemont, Rémi; Matthes, Katja; Omrani, Nour-Eddine; Kodera, Kunihiko; Hansen, Felicitas

    2015-09-15

    Quasi-decadal variability in solar irradiance has been suggested to exert a substantial effect on Earth's regional climate. In the North Atlantic sector, the 11-year solar signal has been proposed to project onto a pattern resembling the North Atlantic Oscillation (NAO), with a lag of a few years due to ocean-atmosphere interactions. The solar/NAO relationship is, however, highly misrepresented in climate model simulations with realistic observed forcings. In addition, its detection is particularly complicated since NAO quasi-decadal fluctuations can be intrinsically generated by the coupled ocean-atmosphere system. Here we compare two multi-decadal ocean-atmosphere chemistry-climate simulations with and without solar forcing variability. While the experiment including solar variability simulates a 1-2-year lagged solar/NAO relationship, comparison of both experiments suggests that the 11-year solar cycle synchronizes quasi-decadal NAO variability intrinsic to the model. The synchronization is consistent with the downward propagation of the solar signal from the stratosphere to the surface.

  7. 48 CFR 225.871 - North Atlantic Treaty Organization (NATO) cooperative projects.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 3 2014-10-01 2014-10-01 false North Atlantic Treaty Organization (NATO) cooperative projects. 225.871 Section 225.871 Federal Acquisition Regulations System... Other International Agreements and Coordination 225.871 North Atlantic Treaty Organization...

  8. 48 CFR 225.871 - North Atlantic Treaty Organization (NATO) cooperative projects.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 3 2013-10-01 2013-10-01 false North Atlantic Treaty Organization (NATO) cooperative projects. 225.871 Section 225.871 Federal Acquisition Regulations System... Other International Agreements and Coordination 225.871 North Atlantic Treaty Organization...

  9. 48 CFR 225.871 - North Atlantic Treaty Organization (NATO) cooperative projects.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 3 2012-10-01 2012-10-01 false North Atlantic Treaty Organization (NATO) cooperative projects. 225.871 Section 225.871 Federal Acquisition Regulations System... Other International Agreements and Coordination 225.871 North Atlantic Treaty Organization...

  10. 48 CFR 225.871 - North Atlantic Treaty Organization (NATO) cooperative projects.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 3 2011-10-01 2011-10-01 false North Atlantic Treaty Organization (NATO) cooperative projects. 225.871 Section 225.871 Federal Acquisition Regulations System... Other International Agreements and Coordination 225.871 North Atlantic Treaty Organization...

  11. 48 CFR 225.871 - North Atlantic Treaty Organization (NATO) cooperative projects.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false North Atlantic Treaty Organization (NATO) cooperative projects. 225.871 Section 225.871 Federal Acquisition Regulations System... Other International Agreements and Coordination 225.871 North Atlantic Treaty Organization...

  12. North American Natural Gas Markets. Volume 2

    SciTech Connect

    Not Available

    1989-02-01

    This report summarizes die research by an Energy Modeling Forum working group on the evolution of the North American natural gas markets between now and 2010. The group`s findings are based partly on the results of a set of economic models of the natural gas industry that were run for four scenarios representing significantly different conditions: two oil price scenarios (upper and lower), a smaller total US resource base (low US resource case), and increased potential gas demand for electric generation (high US demand case). Several issues, such as the direction of regulatory policy and the size of the gas resource base, were analyzed separately without the use of models.

  13. North American poisonous bites and stings.

    PubMed

    Quan, Dan

    2012-10-01

    Critters and creatures can strike fear into anyone who thinks about dangerous animals. This article focuses on the management of the most common North American scorpion, arachnid, hymenoptera, and snake envenomations that cause clinically significant problems. Water creatures and less common animal envenomations are not covered in this article. Critical care management of envenomed patients can be challenging for unfamiliar clinicians. Although the animals are located in specific geographic areas, patients envenomed on passenger airliners and those who travel to endemic areas may present to health care facilities distant from the exposure.

  14. Overview of North American Hydrogen Sensor Standards

    SciTech Connect

    O'Malley, Kathleen; Lopez, Hugo; Cairns, Julie; Wichert, Richard; Rivkin, Carl; Burgess, Robert; Buttner, William

    2015-08-11

    An overview of the main North American codes and standards associated with hydrogen safety sensors is provided. The distinction between a code and a standard is defined, and the relationship between standards and codes is clarified, especially for those circumstances where a standard or a certification requirement is explicitly referenced within a code. The report identifies three main types of standards commonly applied to hydrogen sensors (interface and controls standards, shock and hazard standards, and performance-based standards). The certification process and a list and description of the main standards and model codes associated with the use of hydrogen safety sensors in hydrogen infrastructure are presented.

  15. North American poisonous bites and stings.

    PubMed

    Quan, Dan

    2012-10-01

    Critters and creatures can strike fear into anyone who thinks about dangerous animals. This article focuses on the management of the most common North American scorpion, arachnid, hymenoptera, and snake envenomations that cause clinically significant problems. Water creatures and less common animal envenomations are not covered in this article. Critical care management of envenomed patients can be challenging for unfamiliar clinicians. Although the animals are located in specific geographic areas, patients envenomed on passenger airliners and those who travel to endemic areas may present to health care facilities distant from the exposure. PMID:22998994

  16. A correlated shortening of the North and South American monsoon seasons in the past few decades

    NASA Astrophysics Data System (ADS)

    Arias, Paola A.; Fu, Rong; Vera, Carolina; Rojas, Maisa

    2015-12-01

    Our observational analysis shows that the wet seasons of the American monsoon systems have shortened since 1978 due to correlated earlier retreats of the North American monsoon (NAM) and late onsets of the southern Amazon wet season, an important part of the South American monsoon (SAM). These changes are related to the combination of the global sea surface temperature (SST) warming mode, the El Niño-Southern Oscillation (ENSO), the Atlantic Multidecadal Oscillation (AMO), the westward shift of the North Atlantic subtropical high (NASH), and the enhancement of Pacific South American and Pacific North American wave train patterns, which induces variations of the regional circulation at interannual and decadal scales. The joint contributions from these forcing factors are associated with a stronger and more equatorward regional Hadley cell, which enhances convergence towards the equator, strengthening and possibly delaying the retreat of the tropical part of the NAM. This in turn accelerates the demise of the northern NAM and delays the reversal of the cross-equatorial flow over South America, reducing moisture transport to the SAM and delaying its onset. In addition, the thermodynamic response to warming appears to cause local drier land conditions over both regions, reinforcing the observed changes in these monsoons. Although previous studies have identified the isolated influence of the regional Hadley cell, ENSO, AMO, global SST warming, and NASH on the NAM, the correlated changes between NAM and SAM through variations of the cross-equatorial flow had not been established before.

  17. Observed recent trends in tropical cyclone rainfall over the North Atlantic and the North Pacific

    NASA Astrophysics Data System (ADS)

    Lau, William K. M.; Zhou, Y. P.

    2012-02-01

    In this study, we use Tropical Rainfall Measurement Mission and Global Precipitation Climatology Project rainfall data together with historical storm track records to examine the trend of tropical cyclone (TC) rainfall in the North Atlantic and the northeast and northwest Pacific during two recent decades (1988-1997 and 1998-2007). We find that there is an approximate linear relationship between TC rain (defined as accumulated total rainfall along storm tracks) and storm intensity as classified by the Saffir-Simpson scheme. During the data period, total TC rain has trended upward at a rate of 23.8% ± 23.5% per decade over the North Atlantic but downward with a rate of 25.1% ± 19.7% per decade over the northeast Pacific. Over the northwest Pacific, there is a reduction in TC rain of approximately 20.9% ± 13.5% per decade, possibly associated with a strong interdecadal-scale oscillation. Storm characteristics such as duration and TC rain energy per storm (EPS) remain unchanged for the North Atlantic and the northeast Pacific. For the northwest Pacific, a 28% ± 18% reduction in EPS from the first decade (1988-1997) to the second decade (1998-2007) is found with the track data from the Joint Typhoon Warning Center. Analyses of the probability distribution function of TC rain show that there is an overall increase in TC frequency across the entire TC rainfall spectrum over the North Atlantic but an overall decrease for the northeast Pacific. In the northwest Pacific, we find a redistribution in EPS with decreased frequency in heavy-rain storms and increased frequency in light-rain storms. Overall, trends in TC rain in the different ocean basins are consistent with long-term relative changes in the ambient large-scale sea surface temperature and vertical wind shear and, to a lesser extent, tropical cyclone Maximum Potential Intensity.

  18. On the relationship between Indian Ocean Dipole-Indian Summer Monsoon and Summer North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

    Sundaram, S.; Stenchikov, G. L.

    2013-12-01

    Using 60 years of observed and re-analysis data sets a link between positive Indian Ocean dipole (PIOD), Indian Summer Monsoon (ISM) and Summer North Atlantic Oscillation (SNAO) is proposed. When positive IOD years occur independently without Elnino the presence of positive phase of SNAO is noticed. In such cases over the Atlantic region the centers of action associated with SNAO is shifted northward leading to the change in the mean position of Atlantic jet and storm tracks. Persistence of storm tracks at the new location amounts to a stationary waves, which have a barotropic structure in the vertical. Therefore, the temperature anomalies associated with the stationary wave influences the Tropospheric Temperature (TT), which is clearly seen in the average TT anomaly, showing warming over southern Eurasia and India. This affects the north-south TT gradient in the monsoon region and influences the ISM (Goswami et al., 2006). Concurrently the local Hadley cell associated with PIOD strengthens and enhances the anomalous subsidence over the Mediterranean/Sahara region which in turn strengthens the Azores high and the hence the SNAO itself. Thus the combined influence of PIOD and SNAO produces a positive feed back mechanism for ISM. On the other hand most of the PIOD years co-occurring with Elnino years are accompanied by the negative phase of SNAO. The analysis of the atmospheric circulation clearly indicates the Pacific North American (PNA) type pattern, which negatively influence the SNAO (Huang et al., 1998). This is consistent with the observation that ISM is not enhanced in all PIOD years. The analysis of 60 years historic sea surface temperature runs with the high resolution atmospheric model shows that the model is able to reproduce these teleconnections.

  19. Exploring Linkages Between Gulf of Mexico Sea Surface Conditions and North American Hydroclimate during the Holocene

    NASA Astrophysics Data System (ADS)

    Richey, J. N.; Thirumalai, K.; Quinn, T. M.; Poore, R. Z.

    2015-12-01

    The Gulf of Mexico is part of the Atlantic Warm Pool, a feature that drives oceanic moisture flux to the surrounding continent. It is connected to the North Atlantic Ocean via the loop current, which transports salt and heat from the Caribbean and Gulf of Mexico poleward via the Gulf Stream. As such, variations in Gulf of Mexico sea surface temperature (SST) and salinity (SSS) are linked to changes in North Atlantic Ocean circulation and North American hydroclimate. Although SST and SSS variability in the Gulf of Mexico are well understood on inter-annual and glacial-interglacial timescales, little is known about centennial scale variability in these sea surface parameters through the Holocene. We present here the first continuous multi-decadal resolution time series of SST and SSS spanning the entire Holocene from the Gulf of Mexico. This proxy reconstruction is based on paired measurements of Mg/Ca and δ18O in the planktic foraminifer, Globigerinoides ruber (white variety) in the Garrison Basin. Using these data, in combination with additional Gulf of Mexico SST and SSS records from the late Holocene, we explore linkages between North American precipitation patterns and ocean circulation on centennial timescales.

  20. Evidence for the Original Unity of North American French Dialects

    ERIC Educational Resources Information Center

    Hull, Alexander

    1974-01-01

    Examines the resemblances - morphological, syntactic, lexical and phonological - among North American French dialects today in order to determine the extent to which these represent a common source. (PMP)

  1. Wintering ecology of adult North American ospreys

    USGS Publications Warehouse

    Washburn, Brian E.; Martell, Mark S.; Bierregaard, Richard O.; Henny, Charles J.; Dorr, Brian S.; Olexa, Thomas J.

    2014-01-01

    North American Ospreys (Pandion haliaetus) typically migrate long distances to their wintering grounds in the tropics. Beyond the general distribution of their wintering range (i.e., the Caribbean, South America, and Central America), very little is known about the wintering ecology of these birds. We used satellite telemetry to determine the duration of wintering period, to examine the characteristics of wintering areas used by Ospreys, and to quantify space use and activity patterns of wintering Ospreys. Adult Ospreys migrated to wintering sites and exhibited high wintering site fidelity among years. Overall, Ospreys wintered on river systems (50.6%) more than on lakes (19.0%), and use of coastal areas was (30.4%) intermediate. Ospreys remained on their wintering grounds for an average of 154 d for males and 167 d for females. Locations of wintering Ospreys obtained via GPS-capable satellite telemetry suggest these birds move infrequently and their movements are very localized (i.e., 2 and 1.4 km2, respectively. Overall, our findings suggest wintering adult North American Ospreys are very sedentary, demonstrating a pattern of limited daily movements and high fidelity to a few select locations (presumably roosts). We suggest this wintering strategy might be effective for reducing the risk of mortality and maximizing energy conservation.

  2. Historical genomics of North American maize

    PubMed Central

    van Heerwaarden, Joost; Hufford, Matthew B.; Ross-Ibarra, Jeffrey

    2012-01-01

    Since the advent of modern plant breeding in the 1930s, North American maize has undergone a dramatic adaptation to high-input agriculture. Despite the importance of genetic contributions to historical yield increases, little is known about the underlying genomic changes. Here we use high-density SNP genotyping to characterize a set of North American maize lines spanning the history of modern breeding. We provide a unique analysis of genome-wide developments in genetic diversity, ancestry, and selection. The genomic history of maize is marked by a steady increase in genetic differentiation and linkage disequilibrium, whereas allele frequencies in the total population have remained relatively constant. These changes are associated with increasing genetic separation of breeding pools and decreased diversity in the ancestry of individual lines. We confirm that modern heterotic groups are the product of ongoing divergence from a relatively homogeneous landrace population, but show that differential landrace ancestry remains evident. Using a recent association approach, we characterize signals of directional selection throughout the genome, identifying a number of candidate genes of potential agronomic relevance. However, overall we find that selection has had limited impact on genome-wide patterns of diversity and ancestry, with little evidence for individual lines contributing disproportionately to the accumulation of favorable alleles in today's elite germplasm. Our data suggest breeding progress has mainly involved selection and recombination of relatively common alleles, contributed by a representative but limited set of ancestral lines. PMID:22802642

  3. The Summer Atlas of North American Birds

    USGS Publications Warehouse

    Price, J.; Droege, S.; Price, A.

    1995-01-01

    The North American Breeding Bird Survey comprises a network of regularly censussed, road-based survey routes and constitutes the most comprehensive set of data on the relative abundance and population trends of these birds during the summer months. Its value was highlighted in 1989, when the data were used to confirm suspected population declines in a number of species of neotropical migrants breeding in the northeastern United States and Canada. In this book Jeff and Amy Price and Sam Droege have used these data to create detailed, computer-generated maps showing the relative abundance of 450 species that summer in the contiguous United States and southern Canada. Tabular information on distribution hotspots for these, and a further 50 or so species too local in occurrence to map effectively, are also presented. As a data-based survey, the focus of the maps is on places where occurrence has been systematically confirmed over a number of years. As such, the maps provide a baseline for future and more regionally based studies. Supporting chapters provide details on the survey methodology, the mapping procedures used, and some current concerns in North American bird conservation.

  4. Passive margin uplift around the North Atlantic region and its role in Northern Hemisphere late Cenozoic glaciation

    NASA Astrophysics Data System (ADS)

    Eyles, Nicholas

    1996-02-01

    Tectonic-climatic models of late Cenozoic global cooling emphasize the importance of middle latitude uplifts (e.g., Tibetan Plateau and the American west) but ignore widespread tectonic events on the margins of the North Atlantic Ocean. Pleistocene glaciations, after 2.5 Ma, are characterized by circum North Atlantic continental ice sheets that formed by the coalescence of perennial snow fields on extensive plateau surfaces in eastern Canada, northwest Britain, and Scandinavia. Plateaus record Cenozoic uplift of peneplains in response to semisynchronous magmatic underplating and thermal buoyancy of rifted continental margins. High-standing plateaus are very sensitive to small reductions in summer temperature. As late Cenozoic climate cooling proceeded, driven by uplift in regions external to the North Atlantic region, elevated plateaus became sites for extensive snow fields and ultimately ice sheets. Circum-Atlantic uplift took place in the key latitudinal belt that is most sensitive to orbitally forced changes in solar irradiation; this, together with albedo effects from large snow fields, could have amplified the relatively weak Milankovitch signal.

  5. North American migratory bird management issues

    USGS Publications Warehouse

    Wilson, M.H.; Ryan, D.A.

    1995-01-01

    As human population and industry have grown in North America, land-use practices have greatly altered the landscape. As a result of this changed landscape, several migratory bird populations have declined in recent years. For waterbirds, there have been several milestones: the 1986 North American Waterfowl Management Plan (NAWMP) and the 1989 North American Wetlands Conservation Act. As a result, the United States and Canada have established 12 habitat and 2 species joint ventures. The primary emphasis of waterfowl management in Canada-U.S. has been land purchase and lease, wetland restoration, and coordination of harvest rates. Because of its different biological and cultural context, Mexico has established other conservation priorities. Mexico has had a long-standing concern to conserve its biodiversity and, in addition, conservation of Mexican resources goes hand in hand with human community development. Unlike Canada-U.S., wetland conservation projects in'Mexico include information gathering, environmental education, and management planning for its 32 priority wetlands. For migratory landbirds' scientists attribute declines in several migrant populations to forest fragmentation on the breeding grounds, deforestation on the wintering grounds, pesticide poisoning, or the cumulative effects of habitat changes. In 1990, the Neotropical Migratory Bird Conservation Program, commonly known as Partners in Flight-Aves de las Americas-was initiated. The next step that is being proposed is the formation of a habitat conservation plan for landbirds modeled after the NAWMP. Management of migratory birds requires a strong international approach in order to coordinate actions for the benefit of migratory birds, their habitats, and the uses they provide.

  6. Integrated impact of tropical cyclones on sea surface chlorophyll in the North Atlantic

    USGS Publications Warehouse

    Hanshaw, M.N.; Lozier, M.S.; Palter, J.B.

    2008-01-01

    Past studies have shown that surface chlorophyll-a concentrations increase in the wake of hurricanes. Given the reported increase in the intensity of North Atlantic hurricanes in recent years, increasing chlorophyll-a concentrations, perhaps an indication of increasing biological productivity, would be an expected consequence. However, in order to understand the impact of variable hurricane activity on ocean biology, the magnitude of the hurricane-induced chlorophyll increase relative to other events that stir or mix the upper ocean must be assessed. This study investigates the upper ocean biological response to tropical cyclones in the North Atlantic from 1997-2005. Specifically, we quantitatively compare the anomalous chlorophyll-a concentrations created by cyclone activity to the total distribution of anomalies in the subtropical waters. We show that the cyclone-induced chlorophyll-a increase has minimal impact on the integrated biomass budget, a result that holds even when taking into consideration the lagged and asymmetrical response of ocean color. Copyright 2008 by the American Geophysical Union.

  7. Combined influences of seasonal East Atlantic Pattern and North Atlantic Oscillation to excite Atlantic multidecadal variability in a climate model

    NASA Astrophysics Data System (ADS)

    Ruprich-Robert, Yohan; Cassou, Christophe

    2015-01-01

    The physical processes underlying the internal component of the Atlantic Multidecadal Variability (AMV) are investigated from a 1,000-yr pre-industrial control simulation of the CNRM-CM5 model. The low-frequency fluctuations of the Atlantic Meridional Overturning Circulation (AMOC) are shown to be the main precursor for the model AMV. The full life cycle of AMOC/AMV events relies on a complex time-evolving relationship with both North Atlantic Oscillation (NAO) and East Atlantic Pattern (EAP) that must be considered from a seasonal perspective in order to isolate their action; the ocean is responsible for setting the multidecadal timescale of the fluctuations. AMOC rise leading to a warm phase of AMV is statistically preceded by wintertime NAO+ and EAP+ from ~Lag -40/-20 yrs. Associated wind stress anomalies induce an acceleration of the subpolar gyre (SPG) and enhanced northward transport of warm and saline subtropical water. Concurrent positive salinity anomalies occur in the Greenland-Iceland-Norwegian Seas in link to local sea-ice decline; those are advected by the Eastern Greenland Current to the Labrador Sea participating to the progressive densification of the SPG and the intensification of ocean deep convection leading to AMOC strengthening. From ~Lag -10 yrs prior an AMOC maximum, opposite relationship is found with the NAO for both summer and winter seasons. Despite negative lags, NAO- at that time is consistent with the atmospheric response through teleconnection to the northward shift/intensification of the Inter Tropical Convergence Zone in link to the ongoing warming of tropical north Atlantic basin due to AMOC rise/AMV build-up. NAO- acts as a positive feedback for the full development of the model AMV through surface fluxes but, at the same time, prepares its termination through negative retroaction on AMOC. Relationship between EAP+ and AMOC is also present in summer from ~Lags -30/+10 yrs while winter EAP- is favored around the AMV peak. Based on

  8. North Atlantic Deep Water cools the southern hemisphere

    NASA Astrophysics Data System (ADS)

    Crowley, Thomas J.

    1992-08-01

    A standard explanation for coupling climate variations in the northern and southern hemispheres involves fluctuations in North Atlantic Deep Water (NADW) production. However, I suggest that the "NADW-Antarctic" connection may work opposite to that conjectured by many investigators; that is, when NADW production rates are high, southern hemisphere temperatures decrease rather than increase. The revised interpretation is consistent with observations and ocean modeling studies which demonstrate that, although upwelling of relatively warm NADW water around Antarctica promotes sea ice meltback, a second and more important negative feedback is also operating. In order to conserve volume, southward export of NADW across the equator is accompanied by import of an equivalent volume of considerably warmer water from shallower oceanic layers in the South Atlantic. The southern hemisphere loses heat as a result of this exchange. The hemispherically averaged net heat loss may be as high as 4 W/m², an amount comparable to a CO2 doubling. It is suggested that this more comprehensive view of the role of NADW may explain both decadal-scale variations in South Atlantic sea surface temperatures in this century and two significant problems in Pleistocene climatology: why southern hemisphere temperatures decreased before CO2 levels decreased at the end of the last interglacial and why southern hemisphere temperature changes precede changes in northern hemisphere ice volume. It is shown that when NADW production was reinitiated during the last interglacial (120,000 B.P.), high-latitude southern hemisphere temperatures decreased. The estimated magnitude of altered southern hemisphere heat export is comparable to the ice-age CO2 signal and may be able to account for the observed cooling even when CO2 levels were high. When cast into a frequency domain framework, this interpretation may also help explain why southern hemisphere temperatures lead global ice volume changes.

  9. Categorical representation of North American precipitation projections

    PubMed Central

    Greene, Arthur M.; Seager, Richard

    2016-01-01

    We explore use of the familiar tercile framework of seasonal forecasting for the characterization of 21st-century precipitation projections over North America. Consistent with direct analyses of modeled precipitation change, in a superensemble of CMIP5 simulations an unambiguous pattern of shifted tercile population statistics develops as the globe warms. Expressed categorically, frequencies for the low (i.e., dry) tercile increase in the southwestern United States and southward into Mexico and decrease across the northern tier of North America, while counts for the high tercile shift in the opposite sense. We show that as the 21st-century proceeds, changes become statistically significant over wide regions in the pointwise sense, and also when considered as projections on model-specific climate change “fingerprints”. Background noise in the superensemble, against which significance is established, comprises both structural model uncertainty and natural climate variability. The robustness of these findings makes a compelling case for long-range planning for a dryer future in the American Southwest and southward, and wetter one to the north and especially northeast, while communication is facilitated by widespread user familiarity with the tercile format. PMID:27041506

  10. Categorical representation of North American precipitation projections

    NASA Astrophysics Data System (ADS)

    Greene, Arthur M.; Seager, Richard

    2016-04-01

    We explore use of the familiar tercile framework of seasonal forecasting for the characterization of 21st-century precipitation projections over North America. Consistent with direct analyses of modeled precipitation change, in a superensemble of CMIP5 simulations an unambiguous pattern of shifted tercile population statistics develops as the globe warms. Expressed categorically, frequencies for the low (i.e., dry) tercile increase in the southwestern United States and southward into Mexico and decrease across the northern tier of North America, while counts for the high tercile shift in the opposite sense. We show that as the 21st-century proceeds, changes become statistically significant over wide regions in the pointwise sense, and also when considered as projections on model-specific climate change “fingerprints”. Background noise in the superensemble, against which significance is established, comprises both structural model uncertainty and natural climate variability. The robustness of these findings makes a compelling case for long-range planning for a dryer future in the American Southwest and southward, and wetter one to the north and especially northeast, while communication is facilitated by widespread user familiarity with the tercile format.

  11. Categorical representation of North American precipitation projections.

    PubMed

    Greene, Arthur M; Seager, Richard

    2016-01-01

    We explore use of the familiar tercile framework of seasonal forecasting for the characterization of 21st-century precipitation projections over North America. Consistent with direct analyses of modeled precipitation change, in a superensemble of CMIP5 simulations an unambiguous pattern of shifted tercile population statistics develops as the globe warms. Expressed categorically, frequencies for the low (i.e., dry) tercile increase in the southwestern United States and southward into Mexico and decrease across the northern tier of North America, while counts for the high tercile shift in the opposite sense. We show that as the 21st-century proceeds, changes become statistically significant over wide regions in the pointwise sense, and also when considered as projections on model-specific climate change "fingerprints". Background noise in the superensemble, against which significance is established, comprises both structural model uncertainty and natural climate variability. The robustness of these findings makes a compelling case for long-range planning for a dryer future in the American Southwest and southward, and wetter one to the north and especially northeast, while communication is facilitated by widespread user familiarity with the tercile format. PMID:27041506

  12. Extreme conditions over Europe and North America: role of the Atlantic Multidecadal Variability

    NASA Astrophysics Data System (ADS)

    Ruprich-Robert, Yohan; Msadek, Rym; Delworth, Tom

    2016-04-01

    The Atlantic Multidecadal Variability (AMV) is the result and possibly the source of marked modulations of the climate over many areas of the globe. For instance, the relatively warm and dry climate of North America throughout the 30-yr interval of 1931-60, during which the Dust Bowl and the 1950's drought occurred, has been linked to the concomitant warm phase of the AMV. During this period relative warm and wet conditions prevailed over Europe. After 1960, the Atlantic began to cool, and for almost three decades the North American climate turned wetter and cooler whereas Europe experienced cooler and dryer conditions. However, the shortness of the historical observations compared to the AMV period suggested by longer proxy (~60-80yr) does not allow to firmly conclude on the causal effect of the AMV. We use a model approach to isolate the causal role of the AMV on the occurrence of extreme events over Europe and North America. We present experiments based on two GFDL global climate models, a low resolution version, CM2.1 and a higher resolution model for the atmospheric component, FLOR. In both model experiments sea surface temperatures in the North Atlantic sector are restored to the observed AMV pattern, while the other basins are left fully coupled. In order to explore and robustly isolate the AMV impacts on extreme events, we use large ensemble simulations (100 members for CM2.1 and 50 for FLOR) that we run for 20 years. We find that a positive phase of the AMV increases the frequency of occurrence of drought over North America and of extremely cold/warm conditions over Northern/Central Europe during winter/summer. Interestingly, we find that the AMV impacts on these extreme conditions are modulated by the Pacific response to the AMV itself. Members that develop a weak Pacific response show more extreme events over Europe whereas those that develop a strong Pacific response show more extreme events over North America.

  13. Contributions of Tropical Cyclones to the North Atlantic Climatological Rainfall as Observed from Satellites

    NASA Technical Reports Server (NTRS)

    Rodgers, Edward B.; Adler, Robert F.; Pierce, Harold F.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    The tropical cyclone rainfall climatology study that was performed for the North Pacific was extended to the North Atlantic. Similar to the North Pacific tropical cyclone study, mean monthly rainfall within 444 km of the center of the North Atlantic tropical cyclones (i.e., that reached storm stage and greater) was estimated from passive microwave satellite observations during, an eleven year period. These satellite-observed rainfall estimates were used to assess the impact of tropical cyclone rainfall in altering the geographical, seasonal, and inter-annual distribution of the North Atlantic total rainfall during, June-November when tropical cyclones were most abundant. The main results from this study indicate: 1) that tropical cyclones contribute, respectively, 4%, 3%, and 4% to the western, eastern, and entire North Atlantic; 2) similar to that observed in the North Pacific, the maximum in North Atlantic tropical cyclone rainfall is approximately 5 - 10 deg poleward (depending on longitude) of the maximum non-tropical cyclone rainfall; 3) tropical cyclones contribute regionally a maximum of 30% of the total rainfall 'northeast of Puerto Rico, within a region near 15 deg N 55 deg W, and off the west coast of Africa; 4) there is no lag between the months with maximum tropical cyclone rainfall and non-tropical cyclone rainfall in the western North Atlantic, while in the eastern North Atlantic, maximum tropical cyclone rainfall precedes maximum non-tropical cyclone rainfall; 5) like the North Pacific, North Atlantic tropical cyclones Of hurricane intensity generate the greatest amount of rainfall in the higher latitudes; and 6) warm ENSO events inhibit tropical cyclone rainfall.

  14. Lower-crustal intrusion on the North Atlantic continental margin.

    PubMed

    White, R S; Smith, L K; Roberts, A W; Christie, P A F; Kusznir, N J; Roberts, A M; Healy, D; Spitzer, R; Chappell, A; Eccles, J D; Fletcher, R; Hurst, N; Lunnon, Z; Parkin, C J; Tymms, V J

    2008-03-27

    When continents break apart, the rifting is sometimes accompanied by the production of large volumes of molten rock. The total melt volume, however, is uncertain, because only part of it has erupted at the surface. Furthermore, the cause of the magmatism is still disputed-specifically, whether or not it is due to increased mantle temperatures. We recorded deep-penetration normal-incidence and wide-angle seismic profiles across the Faroe and Hatton Bank volcanic margins in the northeast Atlantic. Here we show that near the Faroe Islands, for every 1 km along strike, 360-400 km(3) of basalt is extruded, while 540-600 km(3) is intruded into the continent-ocean transition. We find that lower-crustal intrusions are focused mainly into a narrow zone approximately 50 km wide on the transition, although extruded basalts flow more than 100 km from the rift. Seismic profiles show that the melt is intruded into the lower crust as sills, which cross-cut the continental fabric, rather than as an 'underplate' of 100 per cent melt, as has often been assumed. Evidence from the measured seismic velocities and from igneous thicknesses are consistent with the dominant control on melt production being increased mantle temperatures, with no requirement for either significant active small-scale mantle convection under the rift or the presence of fertile mantle at the time of continental break-up, as has previously been suggested for the North Atlantic Ocean.

  15. Monitoring the North Atlantic using ocean colour data

    NASA Astrophysics Data System (ADS)

    Fuentes-Yaco, C.; Caverhill, C.; Maass, H.; Porter, C.; White, GN, III

    2016-04-01

    The Remote Sensing Unit (RSU) at the Bedford Institute of Oceanography (BIO) has been monitoring the North Atlantic using ocean colour products for decades. Optical sensors used include CZCS, POLDER, SeaWiFS, MODIS/Aqua and MERIS. The monitoring area is defined by the Atlantic Zone Monitoring Program (AZMP) but certain products extend into Arctic waters, and all-Canadian waters which include the Pacific coast. RSU provides Level 3 images for various products in several formats and a range of temporal and spatial resolutions. Basic statistics for pre-defined areas of interest are compiled for each product. Climatologies and anomaly maps are also routinely produced, and custom products are delivered by request. RSU is involved in the generation of Level 4 products, such as characterizing the phenology of spring and fall phytoplankton blooms, computing primary production, using ocean colour to aid in EBSA (Ecologically and Biologically Significant Area) definition and developing habitat suitability maps. Upcoming operational products include maps of diatom distribution, biogeochemical province boundaries, and products from sensors such as VIIRS (Visible Infrared Imaging Radiometer Suite), OLCI (Ocean Land Colour Instrument), and PACE (Pre-Aerosol, Clouds and ocean Ecosystem) hyperspectral microsatellite mission.

  16. Lower-crustal intrusion on the North Atlantic continental margin.

    PubMed

    White, R S; Smith, L K; Roberts, A W; Christie, P A F; Kusznir, N J; Roberts, A M; Healy, D; Spitzer, R; Chappell, A; Eccles, J D; Fletcher, R; Hurst, N; Lunnon, Z; Parkin, C J; Tymms, V J

    2008-03-27

    When continents break apart, the rifting is sometimes accompanied by the production of large volumes of molten rock. The total melt volume, however, is uncertain, because only part of it has erupted at the surface. Furthermore, the cause of the magmatism is still disputed-specifically, whether or not it is due to increased mantle temperatures. We recorded deep-penetration normal-incidence and wide-angle seismic profiles across the Faroe and Hatton Bank volcanic margins in the northeast Atlantic. Here we show that near the Faroe Islands, for every 1 km along strike, 360-400 km(3) of basalt is extruded, while 540-600 km(3) is intruded into the continent-ocean transition. We find that lower-crustal intrusions are focused mainly into a narrow zone approximately 50 km wide on the transition, although extruded basalts flow more than 100 km from the rift. Seismic profiles show that the melt is intruded into the lower crust as sills, which cross-cut the continental fabric, rather than as an 'underplate' of 100 per cent melt, as has often been assumed. Evidence from the measured seismic velocities and from igneous thicknesses are consistent with the dominant control on melt production being increased mantle temperatures, with no requirement for either significant active small-scale mantle convection under the rift or the presence of fertile mantle at the time of continental break-up, as has previously been suggested for the North Atlantic Ocean. PMID:18368115

  17. Comparison data for Seasat altimetry in the western North Atlantic

    NASA Technical Reports Server (NTRS)

    Cheney, R. E.

    1981-01-01

    The radar altimeter flown on Seasat in 1978 collected approximately 1,000 orbits of high quality data (5-8 precision). In the western North Atlantic these data were combined with a detailed gravimetric geoid in an attempt to produce profiles of dynamic topography. In order to provide a basis for evaluation of these profiles, available oceanographic observations in the Gulf Stream/Sargasso Sea region have been compiled into a series of biweekly maps. The data include XBT's, satellite infrared imagery, and selected trajectories of surface drifters and sub-surface SOFAR floats. The maps document the known locations of the Gulf Stream, cyclonic and anticyclonic rings, and mid-ocean eddies during the period July to October 1978.

  18. The variability of the North Atlantic Oscillation throughout the Holocene

    NASA Astrophysics Data System (ADS)

    Wassenburg, Jasper; Dietrich, Stephan; Fietzke, Jan; Fohlmeister, Jens; Wei, Wei; Jochum, Klaus Peter; Scholz, Denis; Richter, Detlev; Sabaoui, Abdellah; Lohmann, Gerrit; Andreae, Meinrat; Immenhauser, Adrian

    2013-04-01

    The North Atlantic Oscillation (NAO) has a major impact on Northern Hemisphere winter climate. Trouet et al. (2009) reconstructed the NAO for the last millennium based on a Moroccan tree ring PDSI (Palmer Drought Severity Index) reconstruction and a Scottish speleothem record. More recently, Olsen et al. (2012) extended the NAO record back to 5.2 ka BP based on a lake record from West Greenland. It is, however, well known that the NAO exhibits non-stationary behavior and the use of a single location for a NAO reconstruction may not capture the complete variability. In addition, the imprint of the NAO on European rainfall patterns in the Early and Mid Holocene on (multi-) centennial timescales is still largely unknown. This is related to difficulties in establishing robust correlations between different proxy records and the fact that proxies may not only reflect winter conditions (i.e., the season when the NAO has the largest influence). Here we present a precisely dated, high resolution speleothem δ18O record from NW Morocco covering the complete Early and Mid Holocene. Carbon and oxygen isotopes were measured at a resolution of 15 years. A multi-proxy approach provides solid evidence that speleothem δ18O values reflect changes in past rainfall intensity. The Moroccan record shows a significant correlation with a speleothem rainfall record from western Germany, which covers the entire Holocene (Fohlmeister et al., 2012). The combination with the extended speleothem record from Scotland, speleothem records from north Italy and the NAO reconstruction from West Greenland (Olsen et al., 2012) allows us to study the variability of the NAO during the entire Holocene. The relation between West German and Northwest Moroccan rainfall has not been stationary, which is evident from the changing signs of correlation. The Early Holocene is characterized by a positive correlation, which changes between 9 and 8 ka BP into a negative correlation. Simulations with the state

  19. An investigation of Ekman upwelling in the North Atlantic

    NASA Technical Reports Server (NTRS)

    Mcclain, Charles R.; Firestone, James

    1993-01-01

    The spatial and temporal variability of the North Atlantic Ekman upwelling fields on seasonal and interannual time scales is investigated on the basis of surface winds from the Fleet Numerical Oceanography Center for 1979-1986. A pronounced minimum in the basin-wide monthly mean vertical Ekman velocities during 1981-1982 is found. It is shown that the primary source of the interannual signal was the region off NW Africa in the vicinity of the Guinea Dome. Other sectors of the basin experienced no significant interannual trends. Hydrographic data and SST data from the NW Africa sector for 1981-1986 indicate a cooling trend beginning in late 1982, consistent with increased upwelling. The fall and winter seasons' mixed layers at the center of the Guinea Dome were deeper in 1984 and 1985 than in previous years. The potential impact of large interannual variations in Ekman upwelling on basin-wide primary productivity is discussed.

  20. Late Miocene biogeography and paleoclimatology of the central North Atlantic

    USGS Publications Warehouse

    Poore, R.Z.

    1981-01-01

    Quantitative analyses of planktonic foraminiferal assemblages from Deep Sea Drilling Project (DSDP) Holes 334 and 410 demonstrate that subpolar and subtropical faunal provinces existed in the North Atlantic during the late Miocene. Climatic oscillations are clearly recorded in Hole 410 by variations in abundance of the Neogloboquadrina subpolar assemblage. These climatic oscillations have a period of about 1 m.y. Higher frequency oscillations with a periodicity of one to several hundred thousand years are evident from about 6.5 to 7.5 m.y. and are probably present throughout the entire late Miocene. A revised age of 7.0 m.y. is proposed for the first occurrence of the calcareous nannofossil Amaurolithus primus (the Amaurolithus datum). ?? 1981.

  1. The North Atlantic Oscillation system and plant phenology

    NASA Astrophysics Data System (ADS)

    Hubálek, Zdenek

    2016-05-01

    The onset of flowering in 78 wild and domesticated terrestrial plant species recorded in South Moravia (Czech Republic) from 1965 to 2014 was correlated with the North Atlantic Oscillation (NAO) index of the preceding winter. Flowering occurred significantly earlier following positive winter NAO phases (causing spring to be warmer than normal in Central Europe) in nearly all early-flowering (March, April) species; high Pearson correlation values were recorded in, e.g., goat willow, spring snowflake, golden bell, cornelian cherry, sweet violet, cherry plum, grape hyacinth, apricot, blackthorn, common dandelion, cherry, southern magnolia, common apple, cuckoo flower, European bird cherry, and cherry laurel. In contrast, the timing of later-flowering plant species (May to July) did not correlate significantly with the winter NAO index. It was found that local temperature is obviously a proximate factor of plant phenology, while the winter NAO is the ultimate factor, affecting temperature and other meteorological phenomena in Central Europe during spring season.

  2. Plastic Accumulation in the North Atlantic Subtropical Gyre

    NASA Astrophysics Data System (ADS)

    Law, Kara Lavender; Morét-Ferguson, Skye; Maximenko, Nikolai A.; Proskurowski, Giora; Peacock, Emily E.; Hafner, Jan; Reddy, Christopher M.

    2010-09-01

    Plastic marine pollution is a major environmental concern, yet a quantitative description of the scope of this problem in the open ocean is lacking. Here, we present a time series of plastic content at the surface of the western North Atlantic Ocean and Caribbean Sea from 1986 to 2008. More than 60% of 6136 surface plankton net tows collected buoyant plastic pieces, typically millimeters in size. The highest concentration of plastic debris was observed in subtropical latitudes and associated with the observed large-scale convergence in surface currents predicted by Ekman dynamics. Despite a rapid increase in plastic production and disposal during this time period, no trend in plastic concentration was observed in the region of highest accumulation.

  3. The North Atlantic Oscillation system and plant phenology.

    PubMed

    Hubálek, Zdenek

    2016-05-01

    The onset of flowering in 78 wild and domesticated terrestrial plant species recorded in South Moravia (Czech Republic) from 1965 to 2014 was correlated with the North Atlantic Oscillation (NAO) index of the preceding winter. Flowering occurred significantly earlier following positive winter NAO phases (causing spring to be warmer than normal in Central Europe) in nearly all early-flowering (March, April) species; high Pearson correlation values were recorded in, e.g., goat willow, spring snowflake, golden bell, cornelian cherry, sweet violet, cherry plum, grape hyacinth, apricot, blackthorn, common dandelion, cherry, southern magnolia, common apple, cuckoo flower, European bird cherry, and cherry laurel. In contrast, the timing of later-flowering plant species (May to July) did not correlate significantly with the winter NAO index. It was found that local temperature is obviously a proximate factor of plant phenology, while the winter NAO is the ultimate factor, affecting temperature and other meteorological phenomena in Central Europe during spring season. PMID:26431699

  4. Sting jets in intense winter North-Atlantic windstorms

    NASA Astrophysics Data System (ADS)

    Martínez-Alvarado, Oscar; Gray, Suzanne L.; Catto, Jennifer L.; Clark, Peter A.

    2012-06-01

    Extratropical cyclones dominate autumn and winter weather over western Europe. The strongest cyclones, often termed windstorms, have a large socio-economic impact due to the strong surface winds and associated storm surges in coastal areas. Here we show that sting jets are a common feature of windstorms; up to a third of the 100 most intense North-Atlantic winter windstorms over the last two decades satisfy conditions for sting jets. The sting jet is a mesoscale descending airstream that can cause strong near-surface winds in the dry slot of the cyclone, a region not usually associated with strong winds. Despite their localized transient nature, these sting jets can cause significant damage, a prominent example being the storm that devastated southeast England on 16 October 1987. We present the first regional climatology of windstorms with sting jets. Previously analysed sting-jet cases appear to have been exceptional in their track over northwest Europe rather than in their strength.

  5. Oceanic Situational Awareness over the North Atlantic Corridor

    NASA Technical Reports Server (NTRS)

    Welch, Bryan; Greenfield, Israel

    2005-01-01

    Air traffic control (ATC) mandated, aircraft separations over the oceans impose a limitation on traffic capacity for a given corridor, given the projected traffic growth over the oceanic domain. The separations result from a lack of acceptable situational awareness over oceans where radar position updates are not available. This study considers the use of Automatic Dependent Surveillance (ADS) data transmitted over a commercial satellite communications system as an approach to provide ATC with the needed situational awareness and thusly allow for reduced aircraft separations. This study uses Federal Aviation Administration data from a single day for the North Atlantic Corridor to analyze traffic loading to be used as a benchmark against which to compare several approaches for coordinating data transmissions from the aircraft to the satellites.

  6. Sensitivity of the North Atlantic Basin to cyclic climatic forcing during the early Cretaceous

    USGS Publications Warehouse

    Dean, W.E.; Arthur, M.A.

    1999-01-01

    Striking cyclic interbeds of laminated dark-olive to black marlstone and bioturbated white to light-gray limestone of Neocomian (Early Cretaceous) age have been recovered at Deep Sea Drilling Project (DSDP) and Ocean Drilling Project (ODP) sites in the North Atlantic. These Neocomian sequences are equivalent to the Maiolica Formation that outcrops in the Tethyan regions of the Mediterranean and to thick limestone sequences of the Vocontian Trough of France. This lithologic unit marks the widespread deposition of biogenic carbonate over much of the North Atlantic and Tethyan seafloor during a time of overall low sealevel and a deep carbonate compensation depth. The dark clay-rich interbeds typically are rich in organic carbon (OC) with up to 5.5% OC in sequences in the eastern North Atlantic. These eastern North Atlantic sequences off northwest Africa, contain more abundant and better preserved hydrogen-rich, algal organic matter (type II kerogen) relative to the western North Atlantic, probably in response to coastal upwelling induced by an eastern boundary current in the young North Atlantic Ocean. The more abundant algal organic matter in sequences in the eastern North Atlantic is also expressed in the isotopic composition of the carbon in that organic matter. In contrast, organic matter in Neocomian sequences in the western North Atlantic along the continental margin of North America has geochemical and optical characteristics of herbaceous, woody, hydrogen-poor, humic, type III kerogen. The inorganic geochemical characteristics of the dark clay-rich (80% CaCO3) interbeds in both the eastern and western basins of the North Atlantic suggest that they contain minor amounts of relatively unweathered eolian dust derived from northwest Africa during dry intervals.

  7. Regional Model Simulations of Cyclones Over The North Atlantic

    NASA Astrophysics Data System (ADS)

    Keup-Thiel, E.; Klepp, C.; Raschke, E.; Rockel, B.

    Regional model simulations have been carried out for selected cyclones to study wa- ter cycle components over the North Atlantic Ocean. The simulations have been per- formed with the regional model REMO which is based in the dynamical part on the regional weather forecast model system EM/DM of the German Weather Service and on the physical parameterizations of the climate model ECHAM4. Case studies have been done for special cyclones in January/February 1997. For these investigations the regional model REMO has been used with a horizontal resolution of 1/6 degrees, a vertical resolution on 20 levels and a timestep of 60 seconds. As input at the bound- aries and for initialization ECMWF-Analysis fields in T213 resolution were available. Water cycle components such as cloud liquid water content and precipitation are very important for climate simulations and weather forecasts. The uncertainties associated with quantitative estimates of the water cycle components are highlighted by a com- parison of satellite data with simulations of cyclones over the North Atlantic with the regional model REMO. The validation of model simulations with satellite data from the SSM/I (Special Sensor Microwave Imager) clearly show the deficiencies of water cycle components. In this context several case studies will be presented and discussed. The vertically integrated water vapor of the regional model is in good agreement with the satellite data. In contrast to that the high precipitation rate in the cold air outbreak on the backside of the cold front derived from satellite data is generally underesti- mated by the regional model. Although the cold front precipitation itself and a small subsidence zone afterwards is well simulated. In line with this, the liquid water content is to low in the cold air outbreak but reasonable at the cold front itself.

  8. Link between North Atlantic wave climate and circulation changes

    SciTech Connect

    Cardone, V.J.; Greenwood, J.G.; Kushnir, Y.; Cane, M.A.

    1994-12-31

    A secular trend in the mean wave height of the North Atlantic (NA) Ocean has been proposed recently by Bacon and Carter (1991). This estimate was based mainly upon the analysis of wave observations from Seven Stones Light Vessel (SSLV) (1962--1986) located off the southwest tip of England, and Ocean Weather Station Lima (LIMA) (1975--1988) at 57{degree}N, 20{degree}W. The positive trend in the annual mean originates mainly in the monthly means for December, January and February. Kushnir (1994) reports a pattern of NA ocean-atmosphere interaction that indicates a change in the mean low level atmospheric circulation beginning around 1960. This change corresponds to a gradual increase in sea-level pressure in the central NA Ocean. Kushnir linked the change to interdecadal variations in NA sea surface temperature. This raises the possibility that the change in wave climate is associated with this interdecadal air-sea interaction. In this study, this possibility is explored by first hindcasting the sea state over the entire NA over a 10-year period using a calibrated hindcast method and then correlating the variations in the hindcast monthly and seasonal wave height means in the Northeast NA with variations in the circulation index used by Kushnir to monitor changes in the large-scale low level atmospheric circulation. The positive correlation found between these variations, especially during the winter, provides a plausible explanation for the proposed trend in wave climate off the Northwest Coast of Europe as a manifestation of a longer term interdecadal variation resembling the North Atlantic Oscillation.

  9. Geosat Data Assimilation with Application to the Eastern North Atlantic

    NASA Technical Reports Server (NTRS)

    Stammer, Detlef

    1997-01-01

    An attempt is made to determine the three-dimensional ocean circulation from satellite altimeter measurements by assimilating Geosat sea surface height data into an eddy-resolving QuasiGeostrophic (QG) model of the eastern North Atlantic Ocean. Results are tested against independent information from hydrographic field observations and moored current meter data collected during the Geosat ERM. The comparison supports the concept of inferring aspects of the three-dimensional flow field from sea surface height observations by combining altimetric measurements with the dynamics of ocean circulation models. A Holland-type QG model with open boundaries is set up on a 2000 km X 2000 km domain of the eastern North Atlantic between 25 deg. and 45 deg. N, 32 deg. and 8 deg. W. By using a simple nudging technique, about two years of Geosat altimeter data are assimilated into the model every five days as space-time objective analyses on the model grid. The error information resulting from the analysis is used during the assimilation procedure to account for data uncertainties. Results show an intense eddy field, which in the surface layer interacts with a meandering Azores Front. Compared to Geosat, the model leads to smoothed fields that follow the observations. Model simulations are significantly correlated with hydrographic data from March 1988 and June 1989, both close to the surface and in the subsurface. Good agreement is also found between the model velocity fields and moored current meter data in the top two model layers. The agreement is visually weak in the bottom layer, although a coherence analysis reveals an agreement between the model simulation and current meter data over the full water column at periods exceeding 80 days.

  10. Why were Past North Atlantic Warming Conditions Associated with Drier Climate in the Western United States?

    NASA Astrophysics Data System (ADS)

    Wong, C. I.; Potter, G. L.; Montanez, I. P.; Otto-Bliesner, B. L.; Behling, P.; Oster, J. L.

    2014-12-01

    Investigating climate dynamics governing rainfall over the western US during past warmings and coolings of the last glacial and deglaciation is pertinent to understanding how precipitation patterns might change with future global warming, especially as the processes driving the global hydrological reorganization affecting this drought-prone region during these rapid temperature changes remain unresolved. We present model climates of the Bølling warm event (14,500 years ago) and Younger Dryas cool event (12,200 years ago) that i) uniquely enable the assessment of dueling hypothesis about the atmospheric teleconnections responsible for abrupt temperature shifts in the North Atlantic region to variations in moisture conditions across the western US, and ii) show that existing hypotheses about these teleconnections are unsupported. Modeling results show no evidence for a north-south shift of the Pacific winter storm track, and we argue that a tropical moisture source with evolving trajectory cannot explain alternation between wet/dry conditions, which have been reconstructed from the proxy record. Alternatively, model results support a new hypothesis that variations in the intensity of the winter storm track, corresponding to its expansion/contraction, can account for regional moisture differences between warm and cool intervals of the last deglaciation. Furthermore, we demonstrate that the mechanism forcing the teleconnection between the North Atlantic and western US is the same across different boundary conditions. In our simulation, during the last deglaciation, and in simulations of future warming, perturbation of the Rossby wave structure reconfigures the atmospheric state. This reconfiguration affects the Aleutian Low and high-pressure ridge over and off of the northern North American coastline driving variability in the storm track. Similarity between the processes governing the climate response during these distinct time intervals illustrates the robust nature

  11. Sources of iron and phosphate affect the distribution of diazotrophs in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Ratten, Jenni-Marie; LaRoche, Julie; Desai, Dhwani K.; Shelley, Rachel U.; Landing, William M.; Boyle, Ed; Cutter, Gregory A.; Langlois, Rebecca J.

    2015-06-01

    Biological nitrogen fixation (BNF) supplies nutrient-depleted oceanic surface waters with new biologically available fixed nitrogen. Diazotrophs are the only organisms that can fix dinitrogen, but the factors controlling their distribution patterns in the ocean are not well understood. In this study, the relative abundances of eight diazotrophic phylotypes in the subtropical North Atlantic Ocean were determined by quantitative PCR (qPCR) of the nifH gene using TaqMan probes. A total of 152 samples were collected at 27 stations during two GEOTRACES cruises; Lisbon, Portugal to Mindelo, Cape Verde Islands (USGT10) and Woods Hole, MA, USA via the Bermuda Time Series (BATS) to Praia, Cape Verde Islands (USGT11). Seven of the eight diazotrophic phylotypes tested were detected. These included free-living and symbiotic cyanobacteria (unicellular groups (UCYN) A, B and C, Trichodesmium, the diatom-associated cyanobacteria Rhizoselinia-Richelia and Hemiaulus-Richelia) and a γ-proteobacterium (Gamma A, AY896371). The nifH gene abundances were analyzed in the context of a large set of hydrographic parameters, macronutrient and trace metal concentrations measured in parallel with DNA samples using the PRIMER-E software. The environmental variables that most influenced the abundances and distribution of the diazotrophic phylotypes were determined. We observed a geographic segregation of diazotrophic phylotypes between east and west, with UCYN A, UCYN B and UCYN C and the Rhizosolenia-Richelia symbiont associated with the eastern North Atlantic (east of 40°W), and Trichodesmium and Gamma A detected across the basin. Hemiaulus-Richelia symbionts were primarily found in temperate waters near the North American coast. The highest diazotrophic phylotype abundance and diversity were associated with temperatures greater than 22 °C in the surface mixed layer, a high supply of iron from North African aeolian mineral dust deposition and from remineralized nutrients upwelled at the

  12. Opening of the Arctic-North Atlantic Gateway

    NASA Astrophysics Data System (ADS)

    Engen, O.; Faleide, J. I.; Eldholm, O.; Breivik, A.

    2003-12-01

    The ˜150 km wide Fram Strait between Svalbard and Greenland is the only deep-water connection between the Arctic and the world oceans. It is essential for the thermohaline `engine' of the North Atlantic circulation system, pulling warm surface water north along the European coasts while returning cold, saline bottom water from the Arctic. Moreover, it contains a series of short, ultra-slow spreading segments and right-lateral transform faults, connecting the Gakkel Ridge to the rest of the Mid-Atlantic Ridge system. While the ridges to the north and south started spreading near the Paleocene-Eocene transition ( ˜55 Ma), the plate boundary between Svalbard and Greenland underwent shear and a transpressive orogeny. Only after the earliest Oligocene ( ˜33 Ma), when the Greenland plate became attached to North America and the rotation pole moved, the entire plate boundary became divergent. However, the final opening of the Fram Strait gateway was delayed for several reasons: First, basement terraces on the western Svalbard margin were downfaulted post-Eocene, witnessing a pre-breakup crustal thinning period that may have lasted for 15-20 m.y. Second, transform segments formed continental bridges for several m.y. after breakup on the ridge segments; the deep-water passage was not established before continental outliers were separated by young oceanic crust across all transform faults. Third, the Hovgaard microcontinent, which was split off the western Barents Sea-Svalbard margin, may have restricted water circulation for some time. By integrating gravity, bathymetry, magnetic and reflection seismic data we locate the positions of present and extinct spreading axes, as well as the continent-ocean transition (COT) on the Svalbard side. The COT correlates with a steep gradient in the Bouguer gravity anomaly, which is taken as a proxy COT on the sparsely surveyed Greenland side. By testing different rotation poles we arrive at a regionally consistent plate kinematic

  13. Ozone Production from the 2004 North American Boreal Fires

    NASA Technical Reports Server (NTRS)

    Pfister, G. G.; Emmons, L. K.; Hess, P. G.; Honrath, R.; Lamarque, J.-F.; Val Martin, M.; Owen, R. C.; Avery, M. A.; Browell, E. V.; Holloway, J. S.; Nedelec, P.; Purvis, R.; Ryerson, T. B.; Sachse, G. W.; Schlager, H.

    2006-01-01

    We examine the ozone production from boreal forest fires based on a case study of wildfires in Alaska and Canada in summer 2004. The model simulations were performed with the chemistry transport model, MOZART-4, and were evaluated by comparison with a comprehensive set of aircraft measurements. In the analysis we use measurements and model simulations of carbon monoxide (CO) and ozone (O3) at the PICO-NARE station located in the Azores within the pathway of North American outflow. The modeled mixing ratios were used to test the robustness of the enhancement ratio deltaO3/deltaCO (defined as the excess O3 mixing ratio normalized by the increase in CO) and the feasibility for using this ratio in estimating the O3 production from the wildfires. Modeled and observed enhancement ratios are about 0.25 ppbv/ppbv which is in the range of values found in the literature, and results in a global net O3 production of 12.9 2 Tg O3 during summer 2004. This matches the net O3 production calculated in the model for a region extending from Alaska to the East Atlantic (9-11 Tg O3) indicating that observations at PICO-NARE representing photochemically well-aged plumes provide a good measure of the O3 production of North American boreal fires. However, net chemical loss of fire related O3 dominates in regions far downwind from the fires (e.g. Europe and Asia) resulting in a global net O3 production of 6 Tg O3 during the same time period. On average, the fires increased the O3 burden (surface-300 mbar) over Alaska and Canada during summer 2004 by about 7-9%, and over Europe by about 2-3%.

  14. Impacts of Sea Surface Salinity Bias Correction on North Atlantic Ocean Circulation and Climate Variability in the Kiel Climate Model

    NASA Astrophysics Data System (ADS)

    Park, Taewook; Park, Wonsun; Latif, Mojib

    2016-04-01

    We investigated impacts of correcting North Atlantic sea surface salinity (SSS) biases on the ocean circulation of the North Atlantic and on North Atlantic sector mean climate and climate variability in the Kiel Climate Model (KCM). Bias reduction was achieved by applying a freshwater flux correction over the North Atlantic to the model. The quality of simulating the mean circulation of the North Atlantic Ocean, North Atlantic sector mean climate and decadal variability is greatly enhanced in the freshwater flux-corrected integration which, by definition, depicts relatively small North Atlantic SSS biases. In particular, a large reduction in the North Atlantic cold sea surface temperature (SST) bias is observed and a more realistic Atlantic Multidecadal Variability (AMV) simulated. Improvements relative to the non-flux corrected integration also comprise a more realistic representation of deep convection sites, sea ice, gyre circulation and Atlantic Meridional Overturning Circulation (AMOC). The results suggest that simulations of North Atlantic sector mean climate and decadal variability could strongly benefit from alleviating sea surface salinity biases in the North Atlantic, which may enhance the skill of decadal predictions in that region.

  15. North American Tropical Cyclone Landfall and SST: A Statistical Model Study

    NASA Technical Reports Server (NTRS)

    Hall, Timothy; Yonekura, Emmi

    2013-01-01

    A statistical-stochastic model of the complete life cycle of North Atlantic (NA) tropical cyclones (TCs) is used to examine the relationship between climate and landfall rates along the North American Atlantic and Gulf Coasts. The model draws on archived data of TCs throughout the North Atlantic to estimate landfall rates at high geographic resolution as a function of the ENSO state and one of two different measures of sea surface temperature (SST): 1) SST averaged over the NA subtropics and the hurricane season and 2) this SST relative to the seasonal global subtropical mean SST (termed relSST). Here, the authors focus on SST by holding ENSO to a neutral state. Jackknife uncertainty tests are employed to test the significance of SST and relSST landfall relationships. There are more TC and major hurricane landfalls overall in warm years than cold, using either SST or relSST, primarily due to a basinwide increase in the number of storms. The signal along the coast, however, is complex. Some regions have large and significant sensitivity (e.g., an approximate doubling of annual major hurricane landfall probability on Texas from -2 to +2 standard deviations in relSST), while other regions have no significant sensitivity (e.g., the U.S. mid-Atlantic and Northeast coasts). This geographic structure is due to both shifts in the regions of primary TC genesis and shifts in TC propagation.

  16. North American box turtles: A natural history

    USGS Publications Warehouse

    Dodd, C. Kenneth

    2002-01-01

    Once a familiar backyard visitor in many parts of the United States and Mexico, the box turtle is losing the battle against extinction. In North American Box Turtles, C. Kenneth Dodd, Jr., has written the first book-length natural history of the twelve species and subspecies of this endangered animal. This volume includes comprehensive information on the species’ evolution, behavior, courtship and reproduction, habitat use, diet, population structure, systematics, and disease. Special features include color photos of all species, subspecies, and their habitats; a simple identification guide to both living and fossil species; and a summary of information on fossil Terrapene and Native uses of box turtles. End-of-chapter sections highlight future research directions, including the need for long-term monitoring and observation of box turtles within their natural habitat and conservation applications. A glossary and a bibliography of literature on box turtles accompany the text.

  17. North American Insecurities, Fears and Anxieties: Educational Implications

    ERIC Educational Resources Information Center

    Larsen, Marianne A.

    2008-01-01

    Contemporary North American insecurities and fears are the focus of this article. In the first section, the inter-related concepts of insecurity, fear and vulnerability are theorised, and the argument put forward that these have come to constitute a dominant discourse in contemporary North American society. In the second section of the paper, the…

  18. Knowledge Organisation Systems in North American Digital Library Collections

    ERIC Educational Resources Information Center

    Shiri, Ali; Chase-Kruszewski, Sarah

    2009-01-01

    Purpose: The purpose of this paper is to report an investigation into the types of knowledge organisation systems (KOSs) utilised in North American digital library collections. Design/methodology/approach: The paper identifies, analyses and deep scans online North American hosted digital libraries. It reviews the literature related to the…

  19. 2005 the North American Solar Challenge

    SciTech Connect

    Dan Eberle

    2008-12-22

    In July 2005 the North American Solar Challenge (NASC) featured university built solar powered cars ran across the United States into Canada. The competition began in Austin, Texas with stops in Weatherford, Texas; Broken Arrow, Oklahoma; Topeka, Kansas; Omaha, Nebraska; Sioux Falls, South Dakota, Fargo, North Dakota; Winnipeg, Manitoba; Brandon, Manitoba; Regina, Saskatchewan; Medicine Hat, Alberta; mainly following U.S. Highway 75 and Canadian Highway 1 to the finish line in Calgary, Alberta, Canada, for a total distance of 2,500 miles. NASC major sponsors include the U.S. Department of Energy (DOE), Natural Resources Canada and DOEs National Renewable Energy Laboratory. The event is designed to inspire young people to pursue careers in science and engineering. NASCs predecessors, the American Solar Challenge and Sunrayce, generally have been held every two years since 1990. With each race, the solar cars travel faster and further with greater reliability. The NASC promotes: -Renewable energy technologies (specifically photovoltaic or solar cells) -Educational excellence in science, engineering and mathematics -Creative integration of technical and scientific expertise across a wide-range of disciplines -Hands-on experience for students and engineers to develop and demonstrate their technical and creative abilities. Safety is the first priority for the NASC. Each team put its car through grueling qualifying and technical inspections. Teams that failed to meet the requirements were not allowed participate. During the race, each team was escorted by lead and chase vehicles sporting rooftop hazard flashers. An official observer accompanied each solar car team to keep it alert to any safety issues.

  20. Arctic contribution to upper-ocean variability in the North Atlantic

    NASA Technical Reports Server (NTRS)

    Walsh, John E.; Chapman, William L.

    1990-01-01

    The potential climatic leverage of salinity and temperature anomalies in the high-latitude North Atlantic is large. Substantial variations of sea ice have accompanied North Atlantic salinity and temperature anomalies. Atmospheric pressure data are used here to show that the local forcing of high-latitude North Atlantic Ocean fluctuations is augmented by antecedent atmospheric circulation anomalies over the central Arctic. These circulation anomalies are consistent with enhanced wind-forcing of thicker older ice into the Transpolar Drift Stream and an enhanced export of sea ice (fresh water) from the Arctic into the Greenland Sea prior to major episodes of ice severity in the Greenland and Iceland seas.

  1. North East Atlantic Tsunamis Related with Gloria Fault

    NASA Astrophysics Data System (ADS)

    Baptista, M.; Miranda, J. M.; Batllo, J.; Macia, R.

    2011-12-01

    Gloria fault is one segment of the Eurasia-Nubia plate boundary. It is a large strike slip fault, located between 24W and 19W, with scarce seismic activity but which was the location of several large events during the XX Century, in particular the 25 November 1941 earthquake, a submarine strike-slip event of magnitude 8.3-8.4 and the 26 May 1975 with magnitude 7.9. Since the installation of the tide-gauge networks in several countries of the North East Atlantic area a significant amount of mareograms were obtained, concerning these events, in a number of coastal stations located along the European coasts. The most impacted areas were the north coast of Portugal where the sea overtopped some beaches, in November 1941, and the harbors of Azores, in 1975, where it was observed the fast withdraw of the sea followed by a strong influx over the highest water mark. We present here a systematic view of the tsunami potential of the Gloria Fault and using results of hydrodynamic simulations we compare model results against observations and tide records and we discuss the corresponding implications in the design of the NEAMTWS decision matrix. To properly constrain the source characteristics of the tsunamigenic earthquakes, relocation and scalar moment calculation of the 1941 earthquake from digitized seismograms have been performed. This work is a funded by project s TAGUSDELTA. Ref. PTDC/MAR/113888/2009 and PTDC/CTE-GIX/110205/2009

  2. The North American Breeding Bird Survey

    USGS Publications Warehouse

    Bystrak, D.; Ralph, C. John; Scott, J. Michael

    1981-01-01

    A brief history of the North American Breeding Bird Survey (BBS) and a discussion of the technique are presented. The approximately 2000 random roadside routes conducted yearly during the breeding season throughout North America produce an enormous bank of data on distribution and abundance of breeding birds with great potential use. Data on about one million total birds of 500 species per year are on computer tape to facilitate accessibility and are available to any serious investigator. The BBS includes the advantages of wide geographic coverage, sampling of most habitat types, standardization of data collection, and a relatively simple format. The Survey is limited by placement of roads (e.g., marshes and rugged mountainous areas are not well sampled), traffic noise interference in some cases and preference of some bird species for roadside habitats. These and other problems and biases of the BBS are discussed. The uniformity of the technique allows for detecting changes in populations and for creation of maps of relative abundance. Examples of each are presented.

  3. 77 FR 59986 - Johnson Controls Including Workers Whose Wages Were Reported Under IMECO LLC; North American...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-01

    ... IMECO LLC; North American Refrigeration Dixon, IL; Amended Certification Regarding Eligibility To Apply... Johnson Controls, North American Refrigeration, Dixon, Illinois (subject firm). The workers were engaged... LLC, North American Refrigeration, Dixon, Illinois, who became totally or partially separated...

  4. 78 FR 33857 - Meeting Announcements: North American Wetlands Conservation Council; Neotropical Migratory Bird...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-05

    ... Fish and Wildlife Service Meeting Announcements: North American Wetlands Conservation Council...: Notice of meetings. SUMMARY: The North American Wetlands Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA) grant proposals for recommendation to...

  5. 75 FR 8989 - Meeting Announcements: North American Wetlands Conservation Council; Neotropical Migratory Bird...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-26

    ... Fish and Wildlife Service Meeting Announcements: North American Wetlands Conservation Council...: Notice of meetings. SUMMARY: The North American Wetlands Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA) grant proposals for recommendation to...

  6. 77 FR 5264 - Meeting Announcements: North American Wetlands Conservation Council; Neotropical Migratory Bird...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-02

    ... Fish and Wildlife Service Meeting Announcements: North American Wetlands Conservation Council...: Notice of meetings. SUMMARY: The North American Wetlands Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA) grant proposals for recommendation to...

  7. 76 FR 5820 - Meeting Announcements: North American Wetlands Conservation Council; Neotropical Migratory Bird...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-02

    ... Fish and Wildlife Service Meeting Announcements: North American Wetlands Conservation Council...: Notice of meetings. SUMMARY: The North American Wetlands Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA) grant proposals for recommendation to...

  8. Sea-Level Acceleration Hotspot along the Atlantic Coast of North America

    NASA Astrophysics Data System (ADS)

    Sallenger, A. H.; Doran, K. J.; Howd, P.

    2012-12-01

    Spatial variations of sea level rise (SLR) can be forced by dynamic processes arising from circulation and variations in temperature and/or salinity, and by static equilibrium processes arising from mass re-distributions changing gravity and the earth's rotation and shape. The sea-level variations can form unique spatial patterns, yet there are very few field observations verifying predicted patterns, or fingerprints. We present evidence of SLR acceleration in a 1,000-km-long hotspot on the North American Atlantic coast north of Cape Hatteras, North Carolina to above Boston, Massachusetts. By using accelerations, or rate differences, sea level signals that are linear over sub-century records, like the relative sea level changes arising from vertical land movements of glacial isostatic adjustment, do not affect our results. For a 60-yr regression window (between 1950-1979 and 1980-2009), mean increase in the rate of SLR in the hotspot was 1.97 ± 0.64 mm/yr. (For a 40-yr window, the mean rate increase was 3.80 ± 1.06 mm/yr.) South of Cape Hatteras to Key West, Florida, rate differences for either 60 yr or 40 yr windows were not statistically different from zero (e.g. for 60 yr window: mean= 0.11 ± 0.92 mm/yr). This pattern is similar to a fingerprint of dynamic SLR established by sea-level projections in several climate model studies. Correlations were consistent with accelerated SLR associated with a slowdown of Atlantic Meridional Overturning Current.

  9. Interglacial Climate Variability in the Mid-Latitude North Atlantic

    NASA Astrophysics Data System (ADS)

    Chapman, M. R.; Farmer, E. J.

    2009-04-01

    It is widely believed that the last interglacial period had significantly elevated temperatures relative to the Holocene, and sea levels were around 6m above the modern level due to the partial melting of the Greenland Ice Sheet and the West Antarctic Ice Sheet. A pattern of enhanced peak interglacial warmth is particularly evident in the Arctic region, but these differences are thought to be significant at a wider scale as global mean surface temperatures were raised by around +2°C (Otto-Bliesner et al., 2006). Elevated last interglacial temperatures are likewise evident in the deep ocean. The positive temperature anomalies and changes in ocean circulation patterns have largely been ascribed to differences in the distribution of insolation. In this study we use high resolution records of last interglacial climate to examine the extent of variability in the subpolar North Atlantic, corresponding to the Marine Isotope Stage (MIS) 5e interval. Sea surface temperature (SST) estimates are calculated using a variety of planktonic foraminiferal transfer functions, based on faunal assemblage counts, which together with stable isotope and ice rafted debris (IRD) data are used to reconstruct surface hydrography. Benthic stable isotope data provide stratigraphic control and allow us to assess the relative dominance of northern waters of the North Atlantic Deep Water (NADW) in comparison to southern source waters such as the Antarctic Bottom Water. These records provide a detailed picture of climate variability for the period from 65 to 140 ka (approximately from the end of MIS 6 to early MIS 4). Last Interglacial temperature estimates also are compared to the previous and subsequent periods of interglacial warmth to assess the scale and extent of regional variability within the surface ocean environment. Our results highlight two features of particular interest: the internal variability of the MIS 5e period and the pronounced climate fluctuations during the MIS 5

  10. Abrupt changes in the southern extent of North Atlantic Deep Water during Dansgaard-Oeschger events

    NASA Astrophysics Data System (ADS)

    Gottschalk, Julia; Skinner, Luke C.; Misra, Sambuddha; Waelbroeck, Claire; Menviel, Laurie; Timmermann, Axel

    2015-12-01

    The glacial climate system transitioned rapidly between cold (stadial) and warm (interstadial) conditions in the Northern Hemisphere. This variability, referred to as Dansgaard-Oeschger variability, is widely believed to arise from perturbations of the Atlantic Meridional Overturning Circulation. Evidence for such changes during the longer Heinrich stadials has been identified, but direct evidence for overturning circulation changes during Dansgaard-Oeschger events has proven elusive. Here we reconstruct bottom water [CO32-] variability from B/Ca ratios of benthic foraminifera and indicators of sedimentary dissolution, and use these reconstructions to infer the flow of northern-sourced deep water to the deep central sub-Antarctic Atlantic Ocean. We find that nearly every Dansgaard-Oeschger interstadial is accompanied by a rapid incursion of North Atlantic Deep Water into the deep South Atlantic. Based on these results and transient climate model simulations, we conclude that North Atlantic stadial-interstadial climate variability was associated with significant Atlantic overturning circulation changes that were rapidly transmitted across the Atlantic. However, by demonstrating the persistent role of Atlantic overturning circulation changes in past abrupt climate variability, our reconstructions of carbonate chemistry further indicate that the carbon cycle response to abrupt climate change was not a simple function of North Atlantic overturning.

  11. Monitoring and Mitigation Alternatives for Protection of North Atlantic Right Whales during Offshore Wind Farm Installation

    SciTech Connect

    Carlson, Thomas J.; Halvorsen, Michele B.; Matzner, Shari; Copping, Andrea E.; Stavole, Jessica

    2012-09-01

    Progress report on defining and determining monitoring and mitigation measures for protecting North Atlantic Right Whales from the effects of pile driving and other activities associated with installation of offshore wind farms.

  12. Quaternary North Atlantic Surface Paleoceanography in Regions of Potential Deep-water Formation

    NASA Technical Reports Server (NTRS)

    Ruddiman, W. F.

    1984-01-01

    At the time scale of the Quaternary climate cycles, the sites of formation of North Atlantic Deep Water are not known. The interglacial extreme is presumably exemplified by the modern regions; the Norwegian, Greenland and Labrador Seas. During the major glacial-age coolings in the North Atlantic, the sites may have shifted well to the south, perhaps as far as the limit of the polar front at 40 to 50 N. Still other sites may have been important during intermediate climatic conditions. Because of the close coupling of high-latitude surface waters to North Atlantic Deep Water in the modern ocean, the history of sea-surface temperature (SST) oscillations across the high-latitude North Atlantic is relevant to an understanding of deep-water formation on the longer time scales.

  13. Early opening of initially closed Gulf of Mexico and central North Atlantic ocean

    SciTech Connect

    Van Siclen, D.C.

    1984-09-01

    This paper presents ideas on the early opening and evolution of the Gulf of Mexico and the central North Atlantic ocean. It discusses rifting activity, plate tectonics, magnetic anomalies, and the geologic time elements involved.

  14. Recent Changes in Arctic Ocean Sea Ice Motion Associated with the North Atlantic Oscillation

    NASA Technical Reports Server (NTRS)

    Kwok, R.

    1999-01-01

    Examination of a new ice motion dataset of the Arctic Ocean over a recent eighteen year period (1978-1996) reveals patterns of variability that can be linked directly to the North Atlantic Oscillation.

  15. A refined age grid for the Central North Atlantic

    NASA Astrophysics Data System (ADS)

    Luis, J. M.; Miranda, J.

    2012-12-01

    We present a digital model for the age of the Central North Atlantic as a geographical grid with 1 arc minute resolution. Our seafloor isochrons are identified following the 'grid procedure' described in the work of Luis and Miranda (2008). The grid itself, which was initially a locally improved version of the Verhoef et al. (1996) compilation, was improved in 2011 (Luis and Miranda, 2011) and further refined with the inclusion of Russian data north of Charlie Gibbs FZ (personal communication, S. Mercuriev). The location and geometry of the Mid-Atlantic Ridge is now very well constrained by both magnetic anomalies and swath bathymetry data down to ~10 degrees N. We identified an extensive set of chrons 0, 2A, 3, 3A, 4, 4A, 5, 6, 6C, 11-12, 13, 18, 20, 21, 22, 23, 24, 25, 26, 28, 29, 30, 32, 33r, M0, M2, M4, M10, M16, M21 and M25. The ages at each grid node are computed by linear interpolation of adjacent isochrons along the direction of the flow-lines. As a pre-processing step each conjugate pair of isochrones was simplified by rotating one of them about the finite pole of that anomaly and use both, original picks plus rotated ones, to calculate an average segment. Fractures zones are used to constrain the chron's shape. These procedures minimize the uncertainties in locations where on one side of the basin one has good identifications but the other is poorly defined as is typical of many of the old isochrones. Care has also taken to account for locations where significant ridge jumps were found. Ages of the ocean floor between the oldest identified magnetic anomalies and continental crust are interpolated using the oldest ages of the Muller at al. (2008), which were themselves estimated from the ages of passive continental margin segments. This is a contribution to MAREKH project (PTDC/MAR/108142/2008) funded by the Portuguese Science Foundation.

  16. Centennial-Scale Changes in Tropical North Atlantic Salinity Inferred from Scleractinian Corals

    NASA Astrophysics Data System (ADS)

    Moses, C. S.; Swart, P. K.; Rosenheim, B. E.; Thorrold, S.; Zhang, D.

    2004-12-01

    Although there exist reasonably good sea-surface temperature records for most portions of the surface oceans over the past 100 years, there are poor records of salinity variations over the same time period. Salinity variations are important because when combined with temperature they govern the density of ocean water and hence oceanic circulation. Using the well established relationships between the oxygen isotopic composition of coral skeletons and temperature, it is possible to utilize the temperature records to remove this influence from the oxygen isotopic composition and thereby extract salinity records. We have applied this method to corals collected from the Cape Verde Islands in the eastern tropical Atlantic Ocean and from the Lesser Antilles in the western tropical Atlantic and compared the results to sclerosponges from the sub-tropical North Atlantic. The Cape Verde Islands are positioned at a critical juncture in the tropical Atlantic. They are located in an area which shows the highest correlation with the temperature of the north tropical Atlantic Ocean (TNA) and one where there is a steep salinity gradient associated with the presence of the sub-tropical Atlantic gyre. Salinity changes in this area are not associated with input of freshwater from either precipitation or runoff, but rather from changes in evaporation and migration of the sub-tropical Atlantic gyre. Recent work by others has suggested the presence of secular changes in the salinity of surface waters in the tropical and subtropical North Atlantic. In particular, the Salinity Maximum Waters (SMW) of the North Atlantic, generally located between 15°-30° N and 20°-50° W, have reportedly increased in salinity over the last 50-100 years. The reported increase is slight, and does not apply to the entire Atlantic, but it represents a significant change in the freshwater input, or evaporation-precipitation (E-P) balance over large sections of the Atlantic. Our data for the eastern tropical

  17. A definition for rapid weakening of North Atlantic and eastern North Pacific tropical cyclones

    NASA Astrophysics Data System (ADS)

    Wood, Kimberly M.; Ritchie, Elizabeth A.

    2015-11-01

    Periods of 24 h over-water weakening during 1982-2013 for North Atlantic (NAL) and eastern North Pacific (ENP) tropical cyclones (TCs) are examined to determine a threshold for rapid weakening (RW). These periods are defined by consistent weakening while the TC center remained more than 50 km from land. Weakening thresholds of 25, 30, and 35 kt represent the 87th (69th), 94th (80th), and 97th (89th) percentile in the NAL (ENP). Based on these statistics, the 30 kt threshold is chosen to define RW. Compared to all weakening periods, RW events are generally associated with greater 24 h official forecast errors, and these errors tend to be overestimates in both basins. These events usually occur as the TC crosses a sharp sea surface temperature gradient, encounters greater vertical wind shear, and entrains drier air. These metrics may be useful to forecasters assessing the likelihood of RW.

  18. North American Climate in CMIP5 Experiments: Assessment of 21st Century Projections

    NASA Astrophysics Data System (ADS)

    Maloney, E. D.; Kinter, J. L.; Mariotti, A.; Sheffield, J.; Task Force, T.

    2012-12-01

    This presentation summarizes the efforts of the NOAA MAPP CMIP5 task force to examine projections of 21st Century climate in the RCP4.5 and RCP8.5 emission experiments, contained within a comprehensive paper submitted to Journal of Climate. We examine aspects of North American climate change including changes in continental-scale temperature and the hydrologic cycle, extremes events, Northern Hemisphere sea ice, and storm tracks, as well as regional manifestations of these climate variables. We also examine changes in east Pacific and Atlantic tropical cyclone activity and North American intraseasonal to decadal variability, including changes in teleconnections to North America. We show that projected changes are generally consistent with those in CMIP3, although with better model agreement in some areas (e.g. projections of summer time precipitation decreases in the Caribbean and Southern Mexico). Although many projected changes in North American climate are robust across CMIP5 models, substantial disagreement in other areas helps to define priorities for future research. Areas of disagreement include projections of changes in snow water equivalent and diurnal temperature range on a regional basis, precipitation in the Southern U.S., Atlantic and east Pacific tropical cyclone activity, intraseasonal variability, and El Niño teleconnections. CMIP5 model success in simulating historical climate lends confidence to many of the projected results. However, we show that model biases in other areas decrease confidence in projections, including changes in the timing of North American monsoon precipitation, growing season length along the West Coast, and the distribution of persistent drought and wet spells.

  19. Forecast calls for continued period of active hurricane seasons in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    “I have been designated as a representative of Chicken Little to tell you the sky is falling with regard to hurricanes.” So said William Gray professor of atmospheric science at Colorado State University at a July 26 briefing on Capitol Hill. The briefing, sponsored by the Congressional Natural Hazards Caucus, the (U.S.) University Corporation for Atmospheric Research, and the American Meteorological Society highlighted a new report about the current active hurricane period in the North Atlantic, as well as funding needs for hurricane research. “It is amazing the threat we appear to be in for in the next two to three decades, and how little realization of this [there] is with the government and with the general public,” said Gray a long-time forecaster of seasonal hurricane activity and co-author of a July 19 article in Science, “The Recent Increase in Atlantic Hurricane Activity: Causes and Implications.”

  20. Habitats of North American sea ducks.

    USGS Publications Warehouse

    Derksen, Dirk V.; Petersen, Margaret R.; Savard, Jean-Pierre L.

    2015-01-01

    Breeding, molting, fall and spring staging, and wintering habitats of the sea duck tribe Mergini are described based on geographic locations and distribution in North America, geomorphology, vegetation and soil types, and fresh water and marine characteristics. The dynamics of habitats are discussed in light of natural and anthropogenic events that shape areas important to sea ducks. Strategies for sea duck habitat management are outlined and recommendations for international collaboration to preserve key terrestrial and aquatic habitats are advanced. We follow the definition of habitat advanced by Odum (1971), which is the place or space where an organism lives. Weller (1999) emphasized that habitats for waterbirds required presence of sufficient resources (i.e., food, water, cover, space) for maintenance during a portion of their annual cycle. Habitats exploited by North American sea ducks are diverse, widespread across the continent and adjacent marine waters and until recently, most were only superficially known. Even following a 15-year-long effort through the Sea Duck Joint Venture and U.S. and Canadian Endangered/Threatened Species programs to fund research focused on sea duck habitats there are still important gaps in our understanding of key elements required by some species during various life stages. Importantly, many significant habitats, especially staging and wintering sites, have been and continue to be destroyed or altered, largely as a result of anthropogenic effects. Our goal here is to develop a comprehensive summary of marine, freshwater, and terrestrial habitats and their characteristics by considering sea duck species with similar needs as groups (e.g., eiders) within the tribe Mergini. Additionally, this chapter will examine threats and changes to sea duck habitats from human-caused and natural events. Finally, we will evaluate conservation and management programs underway or available for maintenance and enhancement of habitats critical for

  1. Diversity of Diazotrophic Unicellular Cyanobacteria in the Tropical North Atlantic Ocean

    PubMed Central

    Falcón, Luisa I.; Cipriano, Frank; Chistoserdov, Andrei Y.; Carpenter, Edward J.

    2002-01-01

    We present data on the genetic diversity and phylogenetic affinities of N2-fixing unicellular cyanobacteria in the plankton of the tropical North Atlantic Ocean. Our dinitrogenase gene (nifH) sequences grouped together with a group of cyanobacteria from the subtropical North Pacific; another subtropical North Pacific group was only distantly related. Most of the 16S ribosomal DNA sequences from our tropical North Atlantic samples were closely allied with sequences from a symbiont of the diatom Climacodium frauenfeldianum. These findings suggest a complex pattern of evolutionary and ecological divergence among unicellular cyanobacteria within and between ocean basins. PMID:12406777

  2. Phylogeographic analysis reveals a deep lineage split within North Atlantic Littorina saxatilis

    PubMed Central

    Doellman, Meredith M.; Trussell, Geoffrey C.; Grahame, John W.; Vollmer, Steve V.

    2011-01-01

    Phylogeographic studies provide critical insight into the evolutionary histories of model organisms; yet, to date, range-wide data are lacking for the rough periwinkle Littorina saxatilis, a classic example of marine sympatric speciation. Here, we use mitochondrial DNA (mtDNA) sequence data to demonstrate that L. saxatilis is not monophyletic for this marker, but is composed of two distinct mtDNA lineages (I and II) that are shared with sister species Littorina arcana and Littorina compressa. Bayesian coalescent dating and phylogeographic patterns indicate that both L. saxatilis lineages originated in the eastern North Atlantic, around the British Isles, at approximately 0.64 Ma. Both lineages are now distributed broadly across the eastern, central and western North Atlantic, and show strong phylogeographic structure among regions. The Iberian Peninsula is genetically distinct, suggesting prolonged isolation from northeastern North Atlantic populations. Western North Atlantic populations of L. saxatilis lineages I and II predate the last glacial maximum and have been isolated from eastern North Atlantic populations since that time. This identification of two distinct, broadly distributed mtDNA lineages further complicates observed patterns of repeated incipient ecological speciation in L. saxatilis, because the sympatric origins of distinct ecotype pairs on eastern North Atlantic shores may be confounded by admixture of divergent lineages. PMID:21429920

  3. Phylogeographic analysis reveals a deep lineage split within North Atlantic Littorina saxatilis.

    PubMed

    Doellman, Meredith M; Trussell, Geoffrey C; Grahame, John W; Vollmer, Steve V

    2011-11-01

    Phylogeographic studies provide critical insight into the evolutionary histories of model organisms; yet, to date, range-wide data are lacking for the rough periwinkle Littorina saxatilis, a classic example of marine sympatric speciation. Here, we use mitochondrial DNA (mtDNA) sequence data to demonstrate that L. saxatilis is not monophyletic for this marker, but is composed of two distinct mtDNA lineages (I and II) that are shared with sister species Littorina arcana and Littorina compressa. Bayesian coalescent dating and phylogeographic patterns indicate that both L. saxatilis lineages originated in the eastern North Atlantic, around the British Isles, at approximately 0.64 Ma. Both lineages are now distributed broadly across the eastern, central and western North Atlantic, and show strong phylogeographic structure among regions. The Iberian Peninsula is genetically distinct, suggesting prolonged isolation from northeastern North Atlantic populations. Western North Atlantic populations of L. saxatilis lineages I and II predate the last glacial maximum and have been isolated from eastern North Atlantic populations since that time. This identification of two distinct, broadly distributed mtDNA lineages further complicates observed patterns of repeated incipient ecological speciation in L. saxatilis, because the sympatric origins of distinct ecotype pairs on eastern North Atlantic shores may be confounded by admixture of divergent lineages. PMID:21429920

  4. Relationship between North American winter temperature and large-scale atmospheric circulation anomalies and its decadal variation

    NASA Astrophysics Data System (ADS)

    Yu, B.; Lin, H.; Wu, Z. W.; Merryfield, W. J.

    2016-07-01

    The interannual relationship between North American (NA) winter temperature and large-scale atmospheric circulation anomalies and its decadal variation are analyzed. NA temperature anomalies are dominated by two leading maximum covariance analysis (MCA) modes of NA surface temperature and Northern Hemisphere 500 hPa geopotential anomalies. A new teleconnection index, termed the Asian-Bering-North American (ABNA) pattern, is constructed from the normalized geopotential field after linearly removing the contribution of the Pacific-North American (PNA) pattern. The ABNA pattern is sustained by synoptic eddy forcing. The first MCA mode of NA surface temperature is highly correlated with the PNA and ABNA teleconnections, and the second mode with the North Atlantic Oscillation (NAO). This indicates that NA temperature is largely controlled by these three large-scale atmospheric patterns, i.e., the PNA, ABNA and NAO. These temperature-circulation relationships appear stationary in the 20th century.

  5. North Atlantic Surface and Deep-Water Hydrography during the Early Pliocene Warm Period

    NASA Astrophysics Data System (ADS)

    Voelker, A. H. L.; Evans, H. F.; Naafs, B. D.; Cavaleiro, C. D.; Rebotim, A.; Ventura, C.; Stein, R. H.; Channell, J. E. T.

    2014-12-01

    The early Pliocene, with atmospheric carbon dioxide concentrations at levels similar to today, is seen as a case study for Earth's future climate evolution. During this period the progressive closing of the Central American Seaway led to increased poleward heat and salt transport within the Atlantic with North Atlantic Deep Water (NADW) becoming warmer and saltier and resulting in an enhanced Atlantic Meridional Overturning Circulation (AMOC). In order to understand how stable the AMOC really was we produced millennial-scale (1-2 kyr) surface and deep-water records for IODP Site U1313 (41°N, 33°W, 3412m) for the interval from 3.4 to 4.1 Ma. This site is ideally located to monitor past AMOC changes with North Atlantic Drift waters at the surface and NADW in the deep. Although interglacial/glacial cycles are visible, the higher frequency oscillations recorded in both the planktonic G. ruber (white) and benthic Cibicidoides sp. δ18O records impede tuning to the LR04 stack (Lisiecki and Raymo, 2005). We therefore exploit a different approach: using the magnetic polarity chrons (Gilbert, Cochiti) as recorded at Site U1313 as framework, we tune our benthic δ18O record to that of ODP Site 1085 (on LR04 ages). The benthic δ13C record shows millennial-scale oscillations, and the values indicate nearly continuous NADW presence and confirm a strong AMOC, also during most of the glacial periods. Varying surface water conditions, especially during the younger interglacial periods, are reflected in the G. ruber isotope data and appear to be linked to salinity changes since they are not recorded in the alkenone sea-surface temperature data. Although glacial stages Gi 2 and Gi 4 show the expected higher benthic δ18O values, Gi 6 was the glacial period with the strongest impact on the AMOC as revealed by cooler, less ventilated surface waters and a less ventilated NADW. Overall, the AMOC was strong throughout, but experienced high frequency oscillations at a level similar to

  6. Contrails developed under frontal influences of the North Atlantic

    NASA Astrophysics Data System (ADS)

    Laken, B. A.; Pallé, E.; Kniveton, D. R.; Williams, C. J. R.; Kilham, D. A.

    2012-06-01

    Satellite imagery reveals a visually striking pattern of persistent line-shaped contrails located to the Northwest of the British Isles on 1 September 2007, just before sunrise. These contrails formed over the heavily trafficked eastbound North Atlantic Track (NAT) flight paths, as they intersected an area of prefrontal mixing. The high relative humidity with respect to ice within the prefrontal mixing zone allowed the contrails to persist, while the strictly regulated flight paths over the region account for their remarkable shapes. The positioning of the NAT flight paths to take advantage of the jet stream likely maximized regional contrail formation. An estimation of the outgoing top of the atmosphere longwave (LW) flux from the CERES instrument shows that the contrails reduced the local instantaneous LW emissivity by 20.96 (±0.26) W/m2. This example demonstrates that for middle latitude regions, prefrontal mixing is an important factor governing the radiative influence of contrails. However, a full estimation of the radiative impact is not possible, as we cannot specify the amount of shortwave forcing caused by the persistence of the contrails into daytime; moreover, several hours after formation the line-shaped contrails spread and overlapped with pre-existing cloud structures.

  7. Trophodynamic studies on the Condor seamount (Azores, Portugal, North Atlantic)

    NASA Astrophysics Data System (ADS)

    Colaço, A.; Giacomello, E.; Porteiro, F.; Menezes, G. M.

    2013-12-01

    Compared to the surrounding ocean waters, seamounts are commonly considered habitats where biological productivity is higher and consumers proliferate. Despite their high productivity, studies of seamount trophic webs are still scarce and fragmentary, and little is known about the connections between the different compartments. What are the trophic interactions of seamount fauna? How do the pelagic and benthic environment couple? In order to answer these questions, stable isotopes δ15N and δ13C were measured in the organisms collected during the course of numerous campaigns at the Condor seamount in the North Atlantic. The Condor seamount food chain is composed of five trophic levels. Mesopelagic organisms are the link between the epipelagic environment and the benthic and benthopelagic organisms, bridging the gap between primary consumers and the 4th and 5th trophic chain levels. Our results demonstrate, through stable isotope analysis, the important role of mesopelagic organisms in the transfer of energy within the seamount food web, as modeling/theoretical studies have previously suggested.

  8. Decline of subpolar North Atlantic circulation during the 1990s.

    PubMed

    Häkkinen, Sirpa; Rhines, Peter B

    2004-04-23

    Observations of sea surface height reveal that substantial changes have occurred over the past decade in the mid- to high-latitude North Atlantic Ocean. TOPEX/Poseidon altimeter data show that subpolar sea surface height increased during the 1990s, and the geostrophic velocity derived from altimeter data exhibits declining subpolar gyre circulation. Combining the data from earlier satellites, we find that subpolar circulation may have been weaker in the late 1990s than in the late 1970s and 1980s. Direct current-meter observations in the boundary current of the Labrador Sea support the weakening circulation trend of the 1990s and, together with hydrographic data, show that the mid- to late 1990s decline extends deep in the water column. Analysis of the local surface forcing suggests that the 1990s buoyancy forcing has a dynamic effect consistent with altimetric and hydrographic observations: A weak thermohaline forcing allows the decay of the domed structure of subpolar isopycnals and weakening of circulation.

  9. Oceanographic influences on Deep Scattering Layers across the North Atlantic

    NASA Astrophysics Data System (ADS)

    Fennell, Sheena; Rose, George

    2015-11-01

    The distribution and density of Deep Scattering Layers (DSLs) were quantified along North Atlantic transits from Ireland to the Grand Banks of Newfoundland in the springs of 2012, 2013 and 2014 employing a calibrated Simrad EK60 echo sounder at 38 kHz. Concurrently, Sippican T5 XBTs (eXpendable Bathy Thermographs) were used to profile temperatures to 1800 m. In each year the scattering layers spanned the deep basin at depths ranging from near surface to approximately 900 m, but annual mean densities differed significantly. Higher DSL densities were recorded during years that exhibited higher sea temperatures at the depths of major DSL concentration (400-600 m), higher sea level anomalies and stronger eastward geostrophic currents. The highest concentration of the DSLs in each year was found in the area east of the Grand Banks that corresponded with areas of anticyclonic eddies. In this region DSL densities in 2014 were among the highest recorded worldwide (>7000 m2 nautical mile-2). Midwater fishing indicated DSLs were dominated by Myctophids and Sternoptychids. Anticyclonic eddy formation is discussed as a possible means of transport and aggregation of the DSLs in that region, where oceanographic influences may play a dominant role in the distribution and density of the DSLs and upper trophic level fishes.

  10. Decline of subpolar North Atlantic circulation during the 1990s.

    PubMed

    Häkkinen, Sirpa; Rhines, Peter B

    2004-04-23

    Observations of sea surface height reveal that substantial changes have occurred over the past decade in the mid- to high-latitude North Atlantic Ocean. TOPEX/Poseidon altimeter data show that subpolar sea surface height increased during the 1990s, and the geostrophic velocity derived from altimeter data exhibits declining subpolar gyre circulation. Combining the data from earlier satellites, we find that subpolar circulation may have been weaker in the late 1990s than in the late 1970s and 1980s. Direct current-meter observations in the boundary current of the Labrador Sea support the weakening circulation trend of the 1990s and, together with hydrographic data, show that the mid- to late 1990s decline extends deep in the water column. Analysis of the local surface forcing suggests that the 1990s buoyancy forcing has a dynamic effect consistent with altimetric and hydrographic observations: A weak thermohaline forcing allows the decay of the domed structure of subpolar isopycnals and weakening of circulation. PMID:15087505

  11. Declining survival probability threatens the North Atlantic right whale.

    PubMed

    Caswell, H; Fujiwara, M; Brault, S

    1999-03-16

    The North Atlantic northern right whale (Eubalaena glacialis) is considered the most endangered large whale species. Its population has recovered only slowly since the cessation of commercial whaling and numbers about 300 individuals. We applied mark-recapture statistics to a catalog of photographically identified individuals to obtain the first statistically rigorous estimates of survival probability for this population. Crude survival decreased from about 0.99 per year in 1980 to about 0.94 in 1994. We combined this survival trend with a reported decrease in reproductive rate into a branching process model to compute population growth rate and extinction probability. Population growth rate declined from about 1. 053 in 1980 to about 0.976 in 1994. Under current conditions the population is doomed to extinction; an upper bound on the expected time to extinction is 191 years. The most effective way to improve the prospects of the population is to reduce mortality. The right whale is at risk from entanglement in fishing gear and from collisions with ships. Reducing this human-caused mortality is essential to the viability of this population. PMID:10077680

  12. Estimating the Length of the North Atlantic Basin Hurricane Season

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    2012-01-01

    For the interval 1945-2011, the length of the hurricane season in the North Atlantic basin averages about 130 +/- 42 days (the +/-1 standard deviation interval), having a range of 47 to 235 days. Runs-testing reveals that the annual length of season varies nonrandomly at the 5% level of significance. In particular, its trend, as described using 10-yr moving averages, generally has been upward since about 1979, increasing from about 113 to 157 days (in 2003). Based on annual values, one finds a highly statistically important inverse correlation at the 0.1% level of significance between the length of season and the occurrence of the first storm day of the season. For the 2012 hurricane season, based on the reported first storm day of May 19, 2012 (i.e., DOY = 140), the inferred preferential regression predicts that the length of the current season likely will be about 173 +/- 23 days, suggesting that it will end about November 8 +/- 23 days, with only about a 5% chance that it will end either before about September 23, 2012 or after about December 24, 2012.

  13. Sting jets in intense winter North-Atlantic windstorms

    NASA Astrophysics Data System (ADS)

    Martinez-Alvarado, O.; Gray, S. L.; Catto, J. L.; Clark, P. A.

    2012-04-01

    Extratropical cyclones dominate autumn and winter weather over western Europe. The strongest cyclones, often termed windstorms, have a large socio-economic impact due to the strong surface winds and associated storm surges in coastal areas. Here we show that sting jets are a common feature of windstorms; up to a third of the 100 most intense North Atlantic windstorms over the last two decades (identified from ERA-Interim data) satisfy conditions for sting jets. The sting jet is a mesoscale descending airstream that can cause strong near-surface winds in the dry slot of the cyclone, a region not usually associated with strong winds. Despite their localised transient nature these sting jets can cause significant damage, a prominent example being the storm that devastated southeast England on 16 October 1987. We present the first regional climatology of windstorms with sting jets. Previously analysed sting jet cases appear to have been exceptional in their track over northwest Europe rather than in their strength.

  14. Distribution patterns of wintering sea ducks in relation to the North Atlantic Oscillation and local environmental characteristics

    USGS Publications Warehouse

    Zipkin, Elise F.; Gardner, Beth; Gilbert, Andrew T.; O'Connell, Allan F.; Royle, J. Andrew; Silverman, Emily D.

    2010-01-01

    Twelve species of North American sea ducks (Tribe Mergini) winter off the eastern coast of the United States and Canada. Yet, despite their seasonal proximity to urbanized areas in this region, there is limited information on patterns of wintering sea duck habitat use. It is difficult to gather information on sea ducks because of the relative inaccessibility of their offshore locations, their high degree of mobility, and their aggregated distributions. To characterize environmental conditions that affect wintering distributions, as well as their geographic ranges, we analyzed count data on five species of sea ducks (black scoters Melanitta nigra americana, surf scoters M. perspicillata, white-winged scoters M. fusca, common eiders Somateria mollissima, and long-tailed ducks Clangula hyemalis) that were collected during the Atlantic Flyway Sea Duck Survey for ten years starting in the early 1990s. We modeled count data for each species within ten-nautical-mile linear survey segments using a zero-inflated negative binomial model that included four local-scale habitat covariates (sea surface temperature, mean bottom depth, maximum bottom slope, and a variable to indicate if the segment was in a bay or not), one broad-scale covariate (the North Atlantic Oscillation), and a temporal correlation component. Our results indicate that species distributions have strong latitudinal gradients and consistency in local habitat use. The North Atlantic Oscillation was the only environmental covariate that had a significant (but variable) effect on the expected count for all five species, suggesting that broad-scale climatic conditions may be directly or indirectly important to the distributions of wintering sea ducks. Our results provide critical information on species-habitat associations, elucidate the complicated relationship between the North Atlantic Oscillation, sea surface temperature, and local sea duck abundances, and should be useful in assessing the impacts of climate

  15. Species longevity in North American fossil mammals.

    PubMed

    Prothero, Donald R

    2014-08-01

    Species longevity in the fossil record is related to many paleoecological variables and is important to macroevolutionary studies, yet there are very few reliable data on average species durations in Cenozoic fossil mammals. Many of the online databases (such as the Paleobiology Database) use only genera of North American Cenozoic mammals and there are severe problems because key groups (e.g. camels, oreodonts, pronghorns and proboscideans) have no reliable updated taxonomy, with many invalid genera and species and/or many undescribed genera and species. Most of the published datasets yield species duration estimates of approximately 2.3-4.3 Myr for larger mammals, with small mammals tending to have shorter species durations. My own compilation of all the valid species durations in families with updated taxonomy (39 families, containing 431 genera and 998 species, averaging 2.3 species per genus) yields a mean duration of 3.21 Myr for larger mammals. This breaks down to 4.10-4.39 Myr for artiodactyls, 3.14-3.31 Myr for perissodactyls and 2.63-2.95 Myr for carnivorous mammals (carnivorans plus creodonts). These averages are based on a much larger, more robust dataset than most previous estimates, so they should be more reliable for any studies that need species longevity to be accurately estimated.

  16. Glacial geography and native North American languages

    NASA Astrophysics Data System (ADS)

    Rogers, Richard A.

    1985-01-01

    This study tests the hypothesis that the number and distribution of some native American languages may be related to ice-margin changes of the Wisconsin glaciation. The analysis indicated that the number of languages per unit area is much greater in unglaciated areas of the last glacial maximum than in glaciated areas. The pattern of languge overlap between land areas sequentially exposed during deglaciation appears to indicate the direction of movement of populations from the periphery toward the core of the area once covered by the Wisconsin Ice Sheet. The data strongly indicate that North America was inhabited prior to the Wisconsin glacial maximum, because glacial maximum conditions apparently influenced linguistic distributions. Evidence suggests that ancestral Eskimo-Aleut and Na-Dene speakers occupied the northwestern edge of the continental ice mass, and that ancestral Algonquian speakers were south of the ice mass during the Wisconsin glacial maximum (approximately 18,000 yr ago). These three linguistic groups were the principal ones to spreas into areas exposed by the recession of the Wisconsin ice.

  17. Bioluminescence patterns among North American Armillaria species.

    PubMed

    Mihail, Jeanne D

    2015-06-01

    Bioluminescence is widely recognized among white-spored species of Basidiomycota. Most reports of fungal bioluminescence are based upon visual light perception. When instruments such as photomultipliers have been used to measure fungal luminescence, more taxa have been discovered to produce light, albeit at a range of magnitudes. The present studies were undertaken to determine the prevalence of bioluminescence among North American Armillaria species. Consistent, constitutive bioluminescence was detected for the first time for mycelia of Armillaria calvescens, Armillaria cepistipes, Armillaria gemina, Armillaria nabsnona, and Armillaria sinapina and confirmed for mycelia of Armillaria gallica, Armillaria mellea, Armillaria ostoyae, and Armillaria tabescens. Emission spectra of mycelia representing all species had maximum intensity in the range 515-525 nm confirming that emitted light was the result of bioluminescence rather than chemiluminescence. Time series analysis of 1000 consecutive luminescence measurements revealed a highly significant departure from random variation. Mycelial luminescence of eight species exhibited significant, stable shifts in magnitude in response to a series of mechanical disturbance treatments, providing one mechanism for generating observed luminescence variation.

  18. The North American Soil Moisture Database

    NASA Astrophysics Data System (ADS)

    Ford, T.; Quiring, S.

    2012-12-01

    Soil moisture is an important variable in the climate system, yet in situ observations of soil moisture are not prevalent in most regions of the world. The Soil Moisture and Ocean Salinity (SMOS) satellite recently launched by the European Space Agency and NASA's Soil Moisture Active and Passive (SMAP) mission underscore the need for better in situ soil moisture data for validation and accuracy assessment. The North American Soil Moisture Database is a harmonized and quality-controlled soil moisture dataset that is being developed to support investigations of land-atmosphere interactions, validating the accuracy of soil moisture simulations in global land surface models, and describing how soil moisture influences climate on seasonal to interannual timescales. Currently the database is comprised of well over 1,300 soil moisture observation stations from more than 20 networks in the United States. The data is subjected to rigorous quality control procedures. Upon completion, the database will consist of homogenized and standardized soil moisture data products that will be published on a dedicated website and made available to the scientific community to support research efforts such as EaSM, SMAP and SMOS.

  19. Effects of tropical North Atlantic SST on tropical cyclone genesis in the western North Pacific

    NASA Astrophysics Data System (ADS)

    Yu, Jinhua; Li, Tim; Tan, Zhemin; Zhu, Zhiwei

    2016-02-01

    The tropical cyclone genesis number (TCGN) in July-October (JASO) over the western North Pacific (WNP) exhibits a robust interannual variation. It shows a longitudinally tri-pole pattern with a high in the eastern WNP and South China Sea (SCS) and a low in the western WNP, which explain 42.2 and 23.4 % of total TCGN variance in the eastern WNP and SCS, respectively. The high-low-high pattern is similar to that derived from a TC genesis potential index (GPI). To understand the cause of the longitudinal distribution of the dominant interannual mode, we examine the contributions of environmental parameters associated with GPI. It is found that relative humidity and relative vorticity are important factors responsible for TC variability in the SCS, while vertical shear and relative vorticity are crucial in determining TC activity in eastern WNP. A simultaneous correlation analysis shows that the WNP TCGN in JASO is significantly negatively correlated (with a correlation coefficient of -0.5) with sea surface temperature anomalies (SSTA) in the tropical North Atlantic (TNA). The longitudinal distribution of TC genesis frequency regressed onto TNA SSTA resembles that regressed upon the WNP TCGN series. The spatial patterns of regressed environmental variables onto the SSTA over the TNA also resemble those onto TCGN in the WNP, that is, an increase of relative humidity in the SCS and a weakening of vertical shear in the eastern WNP are all associated with cold SSTA in the TNA. Further analyses show that the cold SSTA in the TNA induce a negative heating in situ. In response to this negative heating, a low (upper)-level anomalous aniti-cyclonic (cyclonic) flows appear over the subtropical North Atlantic and eastern North Pacific, and to east of the cold SSTA, anomalous low-level westerlies appear in the tropical Indian Ocean. Given pronounced mean westerlies in northern Indian Ocean in boreal summer, the anomalous westerly flows increase local surface wind speed and surface

  20. Forced and unforced variability of twentieth century North American droughts and pluvials

    NASA Astrophysics Data System (ADS)

    Cook, Benjamin I.; Cook, Edward R.; Anchukaitis, Kevin J.; Seager, Richard; Miller, Ron L.

    2011-09-01

    Research on the forcing of drought and pluvial events over North America is dominated by general circulation model experiments that often have operational limitations (e.g., computational expense, ability to simulate relevant processes, etc). We use a statistically based modeling approach to investigate sea surface temperature (SST) forcing of the twentieth century pluvial (1905-1917) and drought (1932-1939, 1948-1957, 1998-2002) events. A principal component (PC) analysis of Palmer Drought Severity Index (PDSI) from the North American Drought Atlas separates the drought variability into five leading modes accounting for 62% of the underlying variance. Over the full period spanning these events (1900-2005), the first three PCs significantly correlate with SSTs in the equatorial Pacific (PC 1), North Pacific (PC 2), and North Atlantic (PC 3), with spatial patterns (as defined by the empirical orthogonal functions) consistent with our understanding of North American drought responses to SST forcing. We use a large ensemble statistical modeling approach to determine how successfully we can reproduce these drought/pluvial events using these three modes of variability. Using Pacific forcing only (PCs 1-2), we are able to reproduce the 1948-1957 drought and 1905-1917 pluvial above a 95% random noise threshold in over 90% of the ensemble members; the addition of Atlantic forcing (PCs 1-2-3) provides only marginal improvement. For the 1998-2002 drought, Pacific forcing reproduces the drought above noise in over 65% of the ensemble members, with the addition of Atlantic forcing increasing the number passing to over 80%. The severity of the drought, however, is underestimated in the ensemble median, suggesting this drought intensity can only be achieved through internal variability or other processes. Pacific only forcing does a poor job of reproducing the 1932-1939 drought pattern in the ensemble median, and less than one third of ensemble members exceed the noise threshold

  1. Forced and Unforced Variability of Twentieth Century North American Droughts and Pluvials

    NASA Technical Reports Server (NTRS)

    Cook, Benjamin I.; Cook, Edward R.; Anchukaitis, Kevin J.; Seager, Richard; Miller, Ron L.

    2010-01-01

    Research on the forcing of drought and pluvial events over North America is dominated by general circulation model experiments that often have operational limitations (e.g., computational expense, ability to simulate relevant processes, etc). We use a statistically based modeling approach to investigate sea surface temperature (SST) forcing of the twentieth century pluvial (1905-1917) and drought (1932-1939, 1948-1957, 1998-2002) events. A principal component (PC) analysis of Palmer Drought Severity Index (PDSI) from the North American Drought Atlas separates the drought variability into five leading modes accounting for 62% of the underlying variance. Over the full period spanning these events (1900-2005), the first three PCs significantly correlate with SSTs in the equatorial Pacific (PC 1), North Pacific (PC 2), and North Atlantic (PC 3), with spatial patterns (as defined by the empirical orthogonal functions) consistent with our understanding of North American drought responses to SST forcing. We use a large ensemble statistical modeling approach to determine how successfully we can reproduce these drought/pluvial events using these three modes of variability. Using Pacific forcing only (PCs 1-2), we are able to reproduce the 1948-1957 drought and 1905-1917 pluvial above a 95% random noise threshold in over 90% of the ensemble members; the addition of Atlantic forcing (PCs 1-2-3) provides only marginal improvement. For the 1998-2002 drought, Pacific forcing reproduces the drought above noise in over 65% of the ensemble members, with the addition of Atlantic forcing increasing the number passing to over 80%. The severity of the drought, however, is underestimated in the ensemble median, suggesting this drought intensity can only be achieved through internal variability or other processes. Pacific only forcing does a poor job of reproducing the 1932-1939 drought pattern in the ensemble median, and less than one third of ensemble members exceed the noise threshold

  2. Decadal trends in the North Atlantic Oscillation: Regional temperatures and precipitation

    SciTech Connect

    Hurrell, J.W.

    1995-08-01

    Greenland ice-core data have revealed large decadal climate variations over the North Atlantic that can be related to a major source of low-frequency variability, the North Atlantic Oscillation. Over the past decade, the Oscillation has remained in one extreme phase during the winters, contributing significantly to the recent wintertime warmth across Europe and to cold conditions in the northwest Atlantic. An evaluation of the atmospheric moisture budget reveals coherent large-scale changes since 1980 that are linked to recent dry conditions over southern Europe and the Mediterranean, whereas northern Europe and parts of Scandinavia have generally experienced wetter than normal conditions. 27 refs., 4 figs., 1 tab.

  3. The North Atlantic Oscillation as a driver of rapid climate change in the Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Delworth, Thomas L.; Zeng, Fanrong; Vecchi, Gabriel A.; Yang, Xiaosong; Zhang, Liping; Zhang, Rong

    2016-07-01

    Pronounced climate changes have occurred since the 1970s, including rapid loss of Arctic sea ice, large-scale warming and increased tropical storm activity in the Atlantic. Anthropogenic radiative forcing is likely to have played a major role in these changes, but the relative influence of anthropogenic forcing and natural variability is not well established. The above changes have also occurred during a period in which the North Atlantic Oscillation has shown marked multidecadal variations. Here we investigate the role of the North Atlantic Oscillation in these rapid changes through its influence on the Atlantic meridional overturning circulation and ocean heat transport. We use climate models to show that observed multidecadal variations of the North Atlantic Oscillation can induce multidecadal variations in the Atlantic meridional overturning circulation and poleward ocean heat transport in the Atlantic, extending to the Arctic. Our results suggest that these variations have contributed to the rapid loss of Arctic sea ice, Northern Hemisphere warming, and changing Atlantic tropical storm activity, especially in the late 1990s and early 2000s. These multidecadal variations are superimposed on long-term anthropogenic forcing trends that are the dominant factor in long-term Arctic sea ice loss and hemispheric warming.

  4. Surface changes in the North Atlantic meridional overturning circulation during the last millennium.

    PubMed

    Wanamaker, Alan D; Butler, Paul G; Scourse, James D; Heinemeier, Jan; Eiríksson, Jón; Knudsen, Karen Luise; Richardson, Christopher A

    2012-01-01

    Despite numerous investigations, the dynamical origins of the Medieval Climate Anomaly and the Little Ice Age remain uncertain. A major unresolved issue relating to internal climate dynamics is the mode and tempo of Atlantic meridional overturning circulation variability, and the significance of decadal-to-centennial scale changes in Atlantic meridional overturning circulation strength in regulating the climate of the last millennium. Here we use the time-constrained high-resolution local radiocarbon reservoir age offset derived from an absolutely dated annually resolved shell chronology spanning the past 1,350 years, to reconstruct changes in surface ocean circulation and climate. The water mass tracer data presented here from the North Icelandic shelf, combined with previously published data from the Arctic and subtropical Atlantic, show that surface Atlantic meridional overturning circulation dynamics likely amplified the relatively warm conditions during the Medieval Climate Anomaly and the relatively cool conditions during the Little Ice Age within the North Atlantic sector.

  5. Surface changes in the North Atlantic meridional overturning circulation during the last millennium

    PubMed Central

    Wanamaker, Alan D.; Butler, Paul G.; Scourse, James D.; Heinemeier, Jan; Eiríksson, Jón; Knudsen, Karen Luise; Richardson, Christopher A.

    2012-01-01

    Despite numerous investigations, the dynamical origins of the Medieval Climate Anomaly and the Little Ice Age remain uncertain. A major unresolved issue relating to internal climate dynamics is the mode and tempo of Atlantic meridional overturning circulation variability, and the significance of decadal-to-centennial scale changes in Atlantic meridional overturning circulation strength in regulating the climate of the last millennium. Here we use the time-constrained high-resolution local radiocarbon reservoir age offset derived from an absolutely dated annually resolved shell chronology spanning the past 1,350 years, to reconstruct changes in surface ocean circulation and climate. The water mass tracer data presented here from the North Icelandic shelf, combined with previously published data from the Arctic and subtropical Atlantic, show that surface Atlantic meridional overturning circulation dynamics likely amplified the relatively warm conditions during the Medieval Climate Anomaly and the relatively cool conditions during the Little Ice Age within the North Atlantic sector. PMID:22692542

  6. Investigators Share Improved Understanding of the North American Carbon Cycle

    SciTech Connect

    Birdsey, Richard A.; Cook, Robert B; Denning, Scott; Griffith, Peter; Law, Beverly E.; Masek, Jeffrey; Michalak, Anna; Ogle, Stephen; Ojima, Dennis; Pan, Yude; Sabine, Christopher; Sheffner, Edwin; Sundquist, Eric

    2007-06-01

    U.S. North American Carbon Program Investigators Meeting, Colorado Springs, Colorado, 22-25 January 2007. The U.S. North American Carbon Program (NACP) sponsored an "all-scientist" meeting to review progress in understanding the dynamics of the carbon cycle of North America and adjacent oceans, and to chart a course for improved integration across scientific disciplines, scales, and Earth system boundaries. The meeting participants also addressed the need for better decision support tools for managing the carbon cycle of North America, so that strong science can inform policy as interest in taking action increases across the nation.

  7. Pliocene shallow water paleoceanography of the North Atlantic ocean based on marine ostracodes

    USGS Publications Warehouse

    Cronin, T. M.

    1991-01-01

    Middle Pliocene marine ostracodes from coastal and shelf deposits of North and Central America and Iceland were studied to reconstruct paleotemperatures of shelf waters bordering portions of the Western Boundary Current System (including the Gulf Loop Current, Florida Current, Gulf Stream and North Atlantic Drift). Factor analytic transfer functions provided Pliocene August and February bottom-water temperatures of eight regions from the tropics to the subfrigid. The results indicate: (1) meridional temperature gradients in the western North Atlantic were less steep during the Pliocene than either today or during Late Pleistocene Isotope Stage 5e; (2) tropical and subtropical shelf waters during the Middle Pliocene were as warm as, or slightly cooler than today; (3) slightly cooler water was on the outer shelf off the southeastern and mid-Atlantic coast of the U.S., possibly due to summer upwelling of Gulf Stream water; (4) the shelf north of Cape Hatteras, North Carolina may have been influenced by warm water incursions from the western edge of the Gulf Stream, especially in summer; (5) the northeast branch of the North Atlantic Drift brought warm water to northern Iceland between 4 and 3 Ma; evidence from the Iceland record indicates that cold East Greenland Current water did not affect coastal Iceland between 4 and 3 Ma; (6) Middle Pliocene North Atlantic circulation may have been intensified, transporting more heat from the tropics to the Arctic than it does today. ?? 1991.

  8. Trace elements in the atmosphere over the North Atlantic

    NASA Astrophysics Data System (ADS)

    Arimoto, R.; Duce, R. A.; Ray, B. J.; Ellis, W. G.; Cullen, J. D.; Merrill, J. T.

    1995-01-01

    The concentrations of trace elements in aerosol particles from the atmosphere over the North Atlantic Ocean were determined as part of a program designed to characterize the chemical climatology of the region. For these studies, which were part of the Atmosphere-Ocean Chemistry Experiment (AEROCE), 2 years of samples were collected at Tudor Hill, Bermuda (BTT), and at Ragged Point, Barbados (BAT); and 1 year of samples was collected at Mace Head, Ireland (MHT) and at the Izaña Observatory, Tenerife, Canary Islands (IZT). One major component of the aerosol was atmospheric dust, and the ranking for the median mineral dust concentrations as represented by aluminum was BAT > IZT > BTT > MHT. The Al concentrations at BAT, IZT, and BTT ranged over 4 orders of magnitude, i.e., from 0.001 to 10 μg m-3. At MHT the maximum dust concentrations were about a factor of 10 lower than at the other sites, but the lower end of the range in dust concentrations was similar at all sites. The mineral dust concentrations generally were highest in summer, and the flux of atmospheric dust was dominated by sources in North Africa. The elements showing clear enrichments over the concentrations expected from sea salt or crustal sources were I, Sb, Se, V, and Zn. At Izaña, which is in the free troposphere (elevation ˜2360 m), the concentrations of Se and I were much lower than at the boundary layer sites; this difference between sites most likely results from the marine emissions of these elements. The impact of pollution sources on trace element concentrations was evident at all sites but varied with season and location. The concentrations of elements originating from pollution sources generally were low at Barbados. Analyses of trace element ratios indicate that there are large-scale differences in the pollution emissions from North America versus those from Europe and Africa. Emissions from pyrometallurgical industries, steel and iron manufacturing, and possibly biomass burning are more

  9. Hydrography and through-flow in the north-eastern North Atlantic Ocean: the NANSEN project

    NASA Astrophysics Data System (ADS)

    van Aken, H. M.; Becker, G.

    The circulation and hydrography of the north-eastern North Atlantic has been studied with an emphasis on the upper layers and the deep water types which take part in the thermohaline overturning of the Oceanic Conveyor Belt. Over 900 hydrographic stations were used for this study, mainly from the 1987-1991 period. The hydrographic properties of Subpolar Mode Water in the upper layer, which is transported towards the Norwegian Sea, showed large regional variation. The deep water mass was dominated by the cold inflow of deep water from the Norwegian Sea and by a cyclonic recirculation of Lower Deep Water with a high Antarctic Bottom Water content. At intermediate levels the dominating water type was Labrador Sea Water with only minor influence of Mediterranean Sea Water. In the permanent pycnocline traces of Antarctic Intermediate Water were found. Geostrophic transports have been estimated, and these agreed in order of magnitude with the local heat budget, with current measurements, with data from surface drifters, and with the observed water mass modification. A total of 23 Sv of surface water entered the region, of which 20 Sv originated from the North Atlantic Current, while 3 Sv entered via an eastern boundary current. Of this total, 13 Sv of surface water left the area across the Reykjanes Ridge, and 7 Sv entered the Norwegian Sea, while 3 Sv was entrained by the cold overflow across the Iceland-Scotland Ridge. Approximately 1.4 Sv of Norwegian Sea Deep Water was involved in the overflow into the Iceland Basin, which, with about 1.1 Sv of entrained water and 1.1 Sv recirculating Lower Deep Water, formed a deep northern boundary current in the Iceland Basin. At intermediate depths, where Labrador Sea Water formed the dominant water type, about 2 Sv of entrained surface water contributed to a saline water mass which was transported westwards along the south Icelandic slope.

  10. Suborbital timescale variability of North Atlantic Deep Water during the past 200,000 years

    NASA Astrophysics Data System (ADS)

    Oppo, Delia W.; Lehman, Scott J.

    1995-10-01

    also seen in tropical surface water records and at some deep Atlantic sites and may reflect the common derivation of these water masses. Variations of ≥ 0.5 ‰ superimposed on this rising δ13C trend within substage 5e in V29-202 are so far not evident in tropical feed waters and may therefore indicate that NADW production was weaker during the late than mid-Eemian. An electronic supplement of this material may be obtained on a diskette or Anonymous FTP from KOSMOS.AGU.ORG. (LOGIN to AGU's FTP account using ANONYMOUS as the username and GUEST as the password. Go to the right directory by typing CD APEND. Type LS to see what files are available. Type GET and the name of the file to get it. Finally, type QUIT to leave the system.) (Paper 95PA02089, Suborbital timescale variability of North Atlantic Deep Water during the past 200,000 years, by D. W. Oppo and S. J. Lehman) Diskette may be ordered from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009; $15.00. Payment must accompany order.

  11. The potential role of the thermohaline circulation in 20th century North Atlantic climate

    NASA Astrophysics Data System (ADS)

    Delworth, T. L.

    2002-05-01

    Areal mean sea surface temperatures (SSTs) over the North Atlantic are characterized by substantial multidecadal fluctuations during the 20th century. A potential contributing mechanism to this variability is identified using an ensemble of coupled ocean-atmosphere integrations. One ensemble member produces a time series of areal mean SSTs which resembles the observed SSTs, and is used as a surrogate for the real climate system to probe potential mechanisms of Atlantic variability. It is shown that multidecadal fluctuations of the thermohaline circulation (THC) contribute substantially to the simulated multidecadal SST fluctuations. Additional experiments demonstrate that multidecadal fluctuations of the North Atlantic Oscillation are an important influence on the simulated THC by modulating the surface buoyancy flux over oceanic convective regions in the subpolar North Atlantic. Further, additional experiments suggest that such THC fluctuations may have some predictability on decadal timescales. The existence of such multidecadal variability has important implications for the detection of climate change.

  12. New data on Lepidion schmidti (Gadiformes: Moridae) from the north-east Atlantic Ocean.

    PubMed

    Arronte, J C; Bañón, R; Quigley, D T G; Pis-Millán, J A; Heredia, J

    2011-12-01

    A new record of Lepidion schmidti (Gadiformes: Moridae) is reported from the Bay of Biscay (north-east Atlantic Ocean). Lepidion schmidti is a rare and poorly known species, scarcely described in the ichthyological literature. Morphometric and meristic characteristics of the specimen are given. A compilation of the specimens caught in the north-east Atlantic Ocean was carried out and the current status of the species in Atlantic waters is discussed. Lepidion schmidti is characterized mainly by the presence of an inverted V-shaped patch of vomerine teeth and a V-shaped crest on the dorsal surface of the head with the apex anterior. The presence of supernumerary anal fin rays in this species is described for the first time. The results obtained confirm the presence of L. schmidti from the north-east Atlantic Ocean.

  13. Crustal thickness anomalies in the North Atlantic Ocean basin from gravity analysis

    NASA Astrophysics Data System (ADS)

    Wang, Tingting; Lin, Jian; Tucholke, Brian; Chen, Yongshun John

    2011-03-01

    Gravity-derived crustal thickness models were calculated for the North Atlantic Ocean between 76°N and the Chain Fracture Zone and calibrated using seismically determined crustal thickness. About 7% of the ocean crust is <4 km thick (designated as thin crust), and 58% is 4-7 km thick (normal crust); the remaining 35% is >7 km thick and is interpreted to have been affected by excess magmatism. Thin crust probably reflects reduced melt production from relatively cold or refractory mantle at scales of up to hundreds of kilometers along the spreading axis. By far the most prominent thick crust anomaly is associated with Iceland and adjacent areas, which accounts for 57% of total crustal volume in excess of 7 km. Much smaller anomalies include the Azores (8%), Cape Verde Islands (6%), Canary Islands (5%), Madeira (<4%), and New England-Great Meteor Seamount chain (2%), all of which appear to be associated with hot spots. Hot spot-related crustal thickening is largely intermittent, suggesting that melt production is episodic on time scales of tens of millions of years. Thickened crust shows both symmetrical and asymmetrical patterns about the Mid-Atlantic Ridge (MAR) axis, reflecting whether melt anomalies were or were not centered on the MAR axis, respectively. Thickened crust at the Bermuda and Cape Verde rises appears to have been formed by isolated melt anomalies over periods of only ˜20-25 Myr. Crustal thickness anomalies on the African plate generally are larger than those on the North American plate; this most likely results from slower absolute plate speed of the African plate over relatively fixed hot spots.

  14. Links between salinity variation in the Caribbean and North Atlantic thermohaline circulation.

    PubMed

    Schmidt, Matthew W; Spero, Howard J; Lea, David W

    2004-03-11

    Variations in the strength of the North Atlantic Ocean thermohaline circulation have been linked to rapid climate changes during the last glacial cycle through oscillations in North Atlantic Deep Water formation and northward oceanic heat flux. The strength of the thermohaline circulation depends on the supply of warm, salty water to the North Atlantic, which, after losing heat to the atmosphere, produces the dense water masses that sink to great depths and circulate back south. Here we analyse two Caribbean Sea sediment cores, combining Mg/Ca palaeothermometry with measurements of oxygen isotopes in foraminiferal calcite in order to reconstruct tropical Atlantic surface salinity during the last glacial cycle. We find that Caribbean salinity oscillated between saltier conditions during the cold oxygen isotope stages 2, 4 and 6, and lower salinities during the warm stages 3 and 5, covarying with the strength of North Atlantic Deep Water formation. At the initiation of the Bølling/Allerød warm interval, Caribbean surface salinity decreased abruptly, suggesting that the advection of salty tropical waters into the North Atlantic amplified thermohaline circulation and contributed to high-latitude warming.

  15. Links between salinity variation in the Caribbean and North Atlantic thermohaline circulation.

    PubMed

    Schmidt, Matthew W; Spero, Howard J; Lea, David W

    2004-03-11

    Variations in the strength of the North Atlantic Ocean thermohaline circulation have been linked to rapid climate changes during the last glacial cycle through oscillations in North Atlantic Deep Water formation and northward oceanic heat flux. The strength of the thermohaline circulation depends on the supply of warm, salty water to the North Atlantic, which, after losing heat to the atmosphere, produces the dense water masses that sink to great depths and circulate back south. Here we analyse two Caribbean Sea sediment cores, combining Mg/Ca palaeothermometry with measurements of oxygen isotopes in foraminiferal calcite in order to reconstruct tropical Atlantic surface salinity during the last glacial cycle. We find that Caribbean salinity oscillated between saltier conditions during the cold oxygen isotope stages 2, 4 and 6, and lower salinities during the warm stages 3 and 5, covarying with the strength of North Atlantic Deep Water formation. At the initiation of the Bølling/Allerød warm interval, Caribbean surface salinity decreased abruptly, suggesting that the advection of salty tropical waters into the North Atlantic amplified thermohaline circulation and contributed to high-latitude warming. PMID:15014495

  16. North American Society for Pediatric Gastroenterology, Hepatology and Nutrition

    MedlinePlus

    North American Society for Pediatric Gastroenterology, Hepatology and Nutrition Skip to Navigation Essential Pediatric GI Review Course ... Fellows Concise Review of Pediatric Gastroenterology, Hepatology and Nutrition (Second Edition) Just released - The NASPGHAN Fellows Concise ...

  17. North-American Microtektites are More Oxidised than Tektites

    NASA Astrophysics Data System (ADS)

    Giuli, G.; Cicconi, M. R.; Eeckhout, S. G.; Koeberl, C.; Glass, B. P.; Pratesi, G.; Paris, E.

    2012-09-01

    North American (NA) microtektites display Fe3+/Fetot ratios from 0 to 0.75, much higher than microtektites from Ivory Coast and Australasian strewn fields. FTIR determined water content compare well with NA tektites, suggesting lack of alteration.

  18. 4. Historic American Buildings Survey, August, 1971 VIEW OF NORTH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. Historic American Buildings Survey, August, 1971 VIEW OF NORTH SIDE OF CALIFORNIA STREET LOOKING EAST SHOWING LOVE AND BILGER TIN SHOP (FAR LEFT) (HABS NO. ORE-97). - Jacksonville Historic District, Jacksonville, Jackson County, OR

  19. 5. Historic American Buildings Survey, August, 1971 VIEW OF NORTH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. Historic American Buildings Survey, August, 1971 VIEW OF NORTH SIDE CALIFORNIA STREET BETWEEN OREGON STREET AND THIRD STREET SHOWING REPRODUCTION BUILDING. - Jacksonville Historic District, Jacksonville, Jackson County, OR

  20. 24. Historic American Buildings Survey L. C. Durette, Photographer NORTH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    24. Historic American Buildings Survey L. C. Durette, Photographer NORTH ENTRANCE DETAIL RIGHT JAMB, SHOWING SECTION OF CUT FOR DOOR HEADER - Doe Garrison, Lamprey River & Great Bay, Newmarket, Rockingham County, NH

  1. Wildlife values of North American ricelands

    USGS Publications Warehouse

    Eadie, J.M.; Elphick, C.S.; Reinecke, K.J.; Miller, M.R.; Manley, Scott W.

    2008-01-01

    derermining threshold food levels required to maintain bird use; (3) quantifying use of ricefields by nonwaterfowl species throughout the year; and (4) determining the amount and distribution of rice habitat needed to meet objectives of the North American Waterfowl Management Plan and the United States Shorebird Conservation Plan.

  2. Assessing patterns of hybridization between North Atlantic eels using diagnostic single-nucleotide polymorphisms.

    PubMed

    Pujolar, J M; Jacobsen, M W; Als, T D; Frydenberg, J; Magnussen, E; Jónsson, B; Jiang, X; Cheng, L; Bekkevold, D; Maes, G E; Bernatchez, L; Hansen, M M

    2014-06-01

    The two North Atlantic eel species, the European eel (Anguilla anguilla) and the American eel (Anguilla rostrata), spawn in partial sympatry in the Sargasso Sea, providing ample opportunity to interbreed. In this study, we used a RAD (Restriction site Associated DNA) sequencing approach to identify species-specific diagnostic single-nucleotide polymorphisms (SNPs) and design a low-density array that combined with screening of a diagnostic mitochondrial DNA marker. Eels from Iceland (N=159) and from the neighboring Faroe Islands (N=29) were genotyped, along with 94 larvae (49 European and 45 American eel) collected in the Sargasso Sea. Our SNP survey showed that the majority of Icelandic eels are pure European eels but there is also an important contribution of individuals of admixed ancestry (10.7%). Although most of the hybrids were identified as F1 hybrids from European eel female × American eel male crosses, backcrosses were also detected, including a first-generation backcross (F1 hybrid × pure European eel) and three individuals identified as second-generation backcrosses originating from American eel × F1 hybrid backcrosses interbreeding with pure European eels. In comparison, no hybrids were observed in the Faroe Islands, the closest bodies of land to Iceland. It is possible that hybrids show an intermediate migratory behaviour between the two parental species that ultimately brings hybrid larvae to the shores of Iceland, situated roughly halfway between the Sargasso Sea and Europe. Only two hybrids were observed among Sargasso Sea larvae, both backcrosses, but no F1 hybrids, that points to temporal variation in the occurrence of hybridization.

  3. Assessing patterns of hybridization between North Atlantic eels using diagnostic single-nucleotide polymorphisms.

    PubMed

    Pujolar, J M; Jacobsen, M W; Als, T D; Frydenberg, J; Magnussen, E; Jónsson, B; Jiang, X; Cheng, L; Bekkevold, D; Maes, G E; Bernatchez, L; Hansen, M M

    2014-06-01

    The two North Atlantic eel species, the European eel (Anguilla anguilla) and the American eel (Anguilla rostrata), spawn in partial sympatry in the Sargasso Sea, providing ample opportunity to interbreed. In this study, we used a RAD (Restriction site Associated DNA) sequencing approach to identify species-specific diagnostic single-nucleotide polymorphisms (SNPs) and design a low-density array that combined with screening of a diagnostic mitochondrial DNA marker. Eels from Iceland (N=159) and from the neighboring Faroe Islands (N=29) were genotyped, along with 94 larvae (49 European and 45 American eel) collected in the Sargasso Sea. Our SNP survey showed that the majority of Icelandic eels are pure European eels but there is also an important contribution of individuals of admixed ancestry (10.7%). Although most of the hybrids were identified as F1 hybrids from European eel female × American eel male crosses, backcrosses were also detected, including a first-generation backcross (F1 hybrid × pure European eel) and three individuals identified as second-generation backcrosses originating from American eel × F1 hybrid backcrosses interbreeding with pure European eels. In comparison, no hybrids were observed in the Faroe Islands, the closest bodies of land to Iceland. It is possible that hybrids show an intermediate migratory behaviour between the two parental species that ultimately brings hybrid larvae to the shores of Iceland, situated roughly halfway between the Sargasso Sea and Europe. Only two hybrids were observed among Sargasso Sea larvae, both backcrosses, but no F1 hybrids, that points to temporal variation in the occurrence of hybridization. PMID:24424165

  4. Assessing patterns of hybridization between North Atlantic eels using diagnostic single-nucleotide polymorphisms

    PubMed Central

    Pujolar, J M; Jacobsen, M W; Als, T D; Frydenberg, J; Magnussen, E; Jónsson, B; Jiang, X; Cheng, L; Bekkevold, D; Maes, G E; Bernatchez, L; Hansen, M M

    2014-01-01

    The two North Atlantic eel species, the European eel (Anguilla anguilla) and the American eel (Anguilla rostrata), spawn in partial sympatry in the Sargasso Sea, providing ample opportunity to interbreed. In this study, we used a RAD (Restriction site Associated DNA) sequencing approach to identify species-specific diagnostic single-nucleotide polymorphisms (SNPs) and design a low-density array that combined with screening of a diagnostic mitochondrial DNA marker. Eels from Iceland (N=159) and from the neighboring Faroe Islands (N=29) were genotyped, along with 94 larvae (49 European and 45 American eel) collected in the Sargasso Sea. Our SNP survey showed that the majority of Icelandic eels are pure European eels but there is also an important contribution of individuals of admixed ancestry (10.7%). Although most of the hybrids were identified as F1 hybrids from European eel female × American eel male crosses, backcrosses were also detected, including a first-generation backcross (F1 hybrid × pure European eel) and three individuals identified as second-generation backcrosses originating from American eel × F1 hybrid backcrosses interbreeding with pure European eels. In comparison, no hybrids were observed in the Faroe Islands, the closest bodies of land to Iceland. It is possible that hybrids show an intermediate migratory behaviour between the two parental species that ultimately brings hybrid larvae to the shores of Iceland, situated roughly halfway between the Sargasso Sea and Europe. Only two hybrids were observed among Sargasso Sea larvae, both backcrosses, but no F1 hybrids, that points to temporal variation in the occurrence of hybridization. PMID:24424165

  5. Why different gas flux velocity parameterizations result in so similar flux results in the North Atlantic?

    NASA Astrophysics Data System (ADS)

    Piskozub, Jacek; Wróbel, Iwona

    2016-04-01

    The North Atlantic is a crucial region for both ocean circulation and the carbon cycle. Most of ocean deep waters are produced in the basin making it a large CO2 sink. The region, close to the major oceanographic centres has been well covered with cruises. This is why we have performed a study of net CO2 flux dependence upon the choice of gas transfer velocity k parameterization for this very region: the North Atlantic including European Arctic Seas. The study has been a part of a ESA funded OceanFlux GHG Evolution project and, at the same time, a PhD thesis (of I.W) funded by Centre of Polar Studies "POLAR-KNOW" (a project of the Polish Ministry of Science). Early results have been presented last year at EGU 2015 as a PICO presentation EGU2015-11206-1. We have used FluxEngine, a tool created within an earlier ESA funded project (OceanFlux Greenhouse Gases) to calculate the North Atlantic and global fluxes with different gas transfer velocity formulas. During the processing of the data, we have noticed that the North Atlantic results for different k formulas are more similar (in the sense of relative error) that global ones. This was true both for parameterizations using the same power of wind speed and when comparing wind squared and wind cubed parameterizations. This result was interesting because North Atlantic winds are stronger than the global average ones. Was the flux result similarity caused by the fact that the parameterizations were tuned to the North Atlantic area where many of the early cruises measuring CO2 fugacities were performed? A closer look at the parameterizations and their history showed that not all of them were based on North Atlantic data. Some of them were tuned to the South Ocean with even stronger winds while some were based on global budgets of 14C. However we have found two reasons, not reported before in the literature, for North Atlantic fluxes being more similar than global ones for different gas transfer velocity parametrizations

  6. Jurassic Magmatism and Tectonics of the North American Cordillera

    NASA Astrophysics Data System (ADS)

    Boettcher, Stefan

    The relationship of Jurassic magmatic arc rocks to the tectonic evolution of the North American Cordilleran continental margin is a principle theme of Geological Society of America Special Paper 299. The volume gives readers a comprehensive view of the early stages of magmatic arc evolution on a continental margin and is a tribute to the contributions of Richard Lee Armstrong, whose pioneering studies provide a framework for current geologic investigations of the North American Cordillera.

  7. Imaging the lithosphere of rifted passive margins using waveform tomography: North Atlantic, South Atlantic and beyond

    NASA Astrophysics Data System (ADS)

    Lebedev, Sergei; Schaeffer, Andrew; Celli, Nicolas Luca

    2016-04-01

    Lateral variations in seismic velocities in the upper mantle reflect variations in the temperature of the rocks at depth. Seismic tomography thus provides a proxy for lateral changes in the temperature and thickness of the lithosphere. It can map the deep boundaries between tectonic blocks with different properties and age of the lithosphere. Our 3D tomographic models of the upper mantle and the crust at the Atlantic and global scales are constrained by an unprecedentedly large global dataset of broadband waveform fits (over one million seismograms) and provide improved resolution of the lithosphere, compared to other available models. The most prominent high-velocity anomalies, seen down to 150-200 km depths, indicate the cold, thick, stable mantle lithosphere beneath Precambrian cratons, including those in North America, Greenland, northern and eastern Europe, Africa and South America. The dominant, large-scale, low-velocity feature is the global system of mid-ocean ridges, with broader low-velocity regions near hotspots, including Iceland. Currently active continental rifts show highly variable expression in the upper mantle, from pronounced low velocities to weak anomalies; this correlates with the amount of magmatism within the rift zone. Rifted passive margins have typically undergone cooling since the rifting and show more subtle variations in their seismic-velocity structure. Their thermal structure and evolution, however, are also shaped by 3D geodynamic processes since their formation, including cooling by the adjacent cratonic blocks inland and heating by warm oceanic asthenosphere.

  8. Dynamic variability of dissolved Pb and Pb isotope composition from the U.S. North Atlantic GEOTRACES transect

    NASA Astrophysics Data System (ADS)

    Noble, Abigail E.; Echegoyen-Sanz, Yolanda; Boyle, Edward A.; Ohnemus, Daniel C.; Lam, Phoebe J.; Kayser, Rick; Reuer, Matt; Wu, Jingfeng; Smethie, William

    2015-06-01

    This study presents dissolved Pb concentration and isotopic composition distributions from GEOTRACES GA03, the U.S. North Atlantic Transect. Pb in the ocean is primarily derived from anthropogenic sources and Pb fluxes into the North Atlantic Ocean have been steadily decreasing following the phase-out of alkyl leaded gasoline usage in North America and Europe between 1975 and 1995. A compilation of dissolved Pb profiles from three stations occupied repeatedly during the last three decades reveals a dramatic decrease in concentrations within the surface layers and the thermocline maxima, although elevated concentrations greater than 60 pmol/kg are still observed in the center of the North Atlantic gyre where ventilation timescales are longer than at the western boundary. The evolution of stable Pb isotopes at these stations shows a shift from dominantly North American-like composition in surface waters in the early 1980s towards a more European-like composition in later years. The most recent shallow signatures at the Bermuda Atlantic Time Series station (BATS) show an even more recent trend returning to higher 206Pb/207Pb ratios after the completed phase-out of leaded gasoline in Europe, presumably because recently deposited Pb is more strongly influenced by industrial and incineration Pb than by residual alkyl leaded gasoline utilization. In surface waters, trends toward a more prominent European influence are also found in the middle of the basin and toward the European coast, coincident with higher concentrations of surface dissolved Pb. Scavenging of anthropogenic Pb is observed within the TAG hydrothermal plume, and it is unclear if there is any significant contribution to deep water by basaltic Pb leached by hydrothermal fluids. In the upper water column, many stations along the transect show Pb concentration maxima at ~100 m depth, coincident with a low 206Pb/207Pb isotopic signature that is typical of European emission sources. Although Pb ores from the

  9. Hotspot of accelerated sea-level rise on the Atlantic coast of North America

    USGS Publications Warehouse

    Sallenger,, Asbury H.; Doran, Kara S.; Howd, Peter A.

    2012-01-01

    Climate warming does not force sea-level rise (SLR) at the same rate everywhere. Rather, there are spatial variations of SLR superimposed on a global average rise. These variations are forced by dynamic processes, arising from circulation and variations in temperature and/or salinity, and by static equilibrium processes, arising from mass redistributions changing gravity and the Earth's rotation and shape. These sea-level variations form unique spatial patterns, yet there are very few observations verifying predicted patterns or fingerprints. Here, we present evidence of recently accelerated SLR in a unique 1,000-km-long hotspot on the highly populated North American Atlantic coast north of Cape Hatteras and show that it is consistent with a modelled fingerprint of dynamic SLR. Between 1950–1979 and 1980–2009, SLR rate increases in this northeast hotspot were ~ 3–4 times higher than the global average. Modelled dynamic plus steric SLR by 2100 at New York City ranges with Intergovernmental Panel on Climate Change scenario from 36 to 51 cm (ref. 3); lower emission scenarios project 24–36 cm (ref. 7). Extrapolations from data herein range from 20 to 29 cm. SLR superimposed on storm surge, wave run-up and set-up will increase the vulnerability of coastal cities to flooding, and beaches and wetlands to deterioration.

  10. North American Wetlands and Mosquito Control

    PubMed Central

    Rey, Jorge R.; Walton, William E.; Wolfe, Roger J.; Connelly, Roxanne; O’Connell, Sheila M.; Berg, Joe; Sakolsky-Hoopes, Gabrielle E.; Laderman, Aimlee D.

    2012-01-01

    Wetlands are valuable habitats that provide important social, economic, and ecological services such as flood control, water quality improvement, carbon sequestration, pollutant removal, and primary/secondary production export to terrestrial and aquatic food chains. There is disagreement about the need for mosquito control in wetlands and about the techniques utilized for mosquito abatement and their impacts upon wetlands ecosystems. Mosquito control in wetlands is a complex issue influenced by numerous factors, including many hard to quantify elements such as human perceptions, cultural predispositions, and political climate. In spite of considerable progress during the last decades, habitat protection and environmentally sound habitat management still remain inextricably tied to politics and economics. Furthermore, the connections are often complex, and occur at several levels, ranging from local businesses and politicians, to national governments and multinational institutions. Education is the key to lasting wetlands conservation. Integrated mosquito abatement strategies incorporate many approaches and practicable options, as described herein, and need to be well-defined, effective, and ecologically and economically sound for the wetland type and for the mosquito species of concern. The approach will certainly differ in response to disease outbreaks caused by mosquito-vectored pathogens versus quality of life issues caused by nuisance-biting mosquitoes. In this contribution, we provide an overview of the ecological setting and context for mosquito control in wetlands, present pertinent information on wetlands mosquitoes, review the mosquito abatement options available for current wetlands managers and mosquito control professionals, and outline some necessary considerations when devising mosquito control strategies. Although the emphasis is on North American wetlands, most of the material is applicable to wetlands everywhere. PMID:23222252

  11. The North American Amphibian Monitoring Program. [abstract

    USGS Publications Warehouse

    Griffin, J.

    1998-01-01

    The North American Amphibian Monitoring Program has been under development for the past three years. The monitoring strategy for NAAMP has five main prongs: terrestrial salamander surveys, calling surveys, aquatic surveys, western surveys, and atlassing. Of these five, calling surveys were selected as one of the first implementation priorities due to their friendliness to volunteers of varying knowledge levels, relative low cost, and the fact that several groups had already pioneered the techniques involved. While some states and provinces had implemented calling surveys prior to NAAMP, like WI and IL, most states and provinces had little or no history of state/provincewide amphibian monitoring. Thus, the majority of calling survey programs were initiated in the past two years. To assess the progress of this pilot phase, a program review was conducted on the status of the NAAMP calling survey program, and the results of that review will be presented at the meeting. Topics to be discussed include: who is doing what where, extent of route coverage, the continuing random route discussions, quality assurance, strengths and weaknesses of calling surveys, reliability of data, and directions for the future. In addition, a brief overview of the DISPro project will be included. DISPro is a new amphibian monitoring program in National Parks, funded by the Demonstration of Intensive Sites Program (DISPro) through the EPA and NPS. It will begin this year at Big Bend and Shenandoah National Parks. The purpose of the DISPro Amphibian Project will be to investigate relationships between environmental factors and stressors and the distribution, abundance, and health of amphibians in these National Parks. At each Park, amphibian long-term monitoring protocols will be tested, distributions and abundance of amphibians will be mapped, and field research experiments will be conducted to examine stressor effects on amphibians (e.g., ultraviolet radiation, contaminants, acidification).

  12. North American wetlands and mosquito control.

    PubMed

    Rey, Jorge R; Walton, William E; Wolfe, Roger J; Connelly, C Roxanne; O'Connell, Sheila M; Berg, Joe; Sakolsky-Hoopes, Gabrielle E; Laderman, Aimlee D

    2012-12-10

    Wetlands are valuable habitats that provide important social, economic, and ecological services such as flood control, water quality improvement, carbon sequestration, pollutant removal, and primary/secondary production export to terrestrial and aquatic food chains. There is disagreement about the need for mosquito control in wetlands and about the techniques utilized for mosquito abatement and their impacts upon wetlands ecosystems. Mosquito control in wetlands is a complex issue influenced by numerous factors, including many hard to quantify elements such as human perceptions, cultural predispositions, and political climate. In spite of considerable progress during the last decades, habitat protection and environmentally sound habitat management still remain inextricably tied to politics and economics. Furthermore, the connections are often complex, and occur at several levels, ranging from local businesses and politicians, to national governments and multinational institutions. Education is the key to lasting wetlands conservation. Integrated mosquito abatement strategies incorporate many approaches and practicable options, as described herein, and need to be well-defined, effective, and ecologically and economically sound for the wetland type and for the mosquito species of concern. The approach will certainly differ in response to disease outbreaks caused by mosquito-vectored pathogens versus quality of life issues caused by nuisance-biting mosquitoes. In this contribution, we provide an overview of the ecological setting and context for mosquito control in wetlands, present pertinent information on wetlands mosquitoes, review the mosquito abatement options available for current wetlands managers and mosquito control professionals, and outline some necessary considerations when devising mosquito control strategies. Although the emphasis is on North American wetlands, most of the material is applicable to wetlands everywhere.

  13. Twinning rates for North American Holstein sires.

    PubMed

    Johanson, J M; Bergert, P J; Kirkpatrick, B W; Dentine, M R

    2001-09-01

    Calving data of North American Holsteins were analyzed using a linear sire model and a threshold sire model to estimate fixed effects and sire predicted transmitting abilities (PTA) for twinning rate. The data were 1,324,678 births of 37,174 sires of cows from the National Association of Animal Breeders (NAAB) calving ease database. All twins were assumed to be dizygotic. Triplets were not included in the analysis. The twinning rate was 5.02%. The sire model included relationships among sires and fixed effects of herd-years, season, parity, and sire groups. Different estimates of heritability due to models and restrictions on data have been demonstrated. Heritability estimates for the sire of the cow effect were 2.10% by the linear model analysis and 8.71% by the threshold model analysis. Sire PTA for twinning rate ranged from 1.6 to 8.0%. Mean incidence of twins increased from first to fifth and later parities: 1.63, 5.22, 6.66, 7.19, and 7.19%, respectively. Some changes with season were also evident. The incidence of twins was highest in April to June, at 5.88%, and lowest in October to December, at 4.23%. Sire group effects showed that sires born after 1990 had a higher incidence of twins than sires born before 1990. The mean twinning rate for sires born before 1980 was 4.55% compared with a mean of 5.58% for sires born after 1991. Characteristics of individual sire evaluations are discussed. Ample opportunity exists to change the incidence of twins in the Holstein population. Sire selection can be used to reduce the incidence of twins and also the increased cost of production associated with twins. From a national perspective, a reduction in the incidence of twin births can result in a saving of as much as $55 million per year.

  14. 50 CFR 224.105 - Speed restrictions to protect North Atlantic Right Whales.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 9 2011-10-01 2011-10-01 false Speed restrictions to protect North... AND ANADROMOUS SPECIES § 224.105 Speed restrictions to protect North Atlantic Right Whales. (a) The..., GA): Vessels shall travel at a speed of 10 knots or less over ground during the period of November...

  15. 50 CFR 224.105 - Speed restrictions to protect North Atlantic Right Whales.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 10 2013-10-01 2013-10-01 false Speed restrictions to protect North... AND ANADROMOUS SPECIES § 224.105 Speed restrictions to protect North Atlantic Right Whales. (a) The..., GA): Vessels shall travel at a speed of 10 knots or less over ground during the period of November...

  16. 50 CFR 224.105 - Speed restrictions to protect North Atlantic Right Whales.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 50 Wildlife and Fisheries 10 2012-10-01 2012-10-01 false Speed restrictions to protect North... AND ANADROMOUS SPECIES § 224.105 Speed restrictions to protect North Atlantic Right Whales. (a) The..., GA): Vessels shall travel at a speed of 10 knots or less over ground during the period of November...

  17. 50 CFR 224.105 - Speed restrictions to protect North Atlantic Right Whales.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 10 2014-10-01 2014-10-01 false Speed restrictions to protect North... AND ANADROMOUS SPECIES § 224.105 Speed restrictions to protect North Atlantic Right Whales. (a) The..., GA): Vessels shall travel at a speed of 10 knots or less over ground during the period of November...

  18. 50 CFR 224.105 - Speed restrictions to protect North Atlantic Right Whales.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 7 2010-10-01 2010-10-01 false Speed restrictions to protect North... AND ANADROMOUS SPECIES § 224.105 Speed restrictions to protect North Atlantic Right Whales. (a) The..., GA): Vessels shall travel at a speed of 10 knots or less over ground during the period of November...

  19. Diabatic modification of potential vorticity in a north Atlantic cyclone

    NASA Astrophysics Data System (ADS)

    Chagnon, J.; Gray, S.; Methven, J.

    2012-04-01

    Heating and cooling due to moist processes in extratropical cyclones introduce local anomalies of potential vorticity (PV). On the mesoscale, diabatically-induced flow anomalies can influence the evolution of mesoscale precipitation structures. If distributed over a large portion of the cyclone, the modified PV can also influence the evolution of the synoptic-scale wave pattern, thus effecting events downstream. The moist processes contributing to modification of PV are typically parameterized in numerical weather prediction models. The purpose of this paper is to examine the structure and origin of diabatic PV near the level of the tropopause in a north Atlantic cyclone. A mature cyclone with a warm conveyor belt and a tropopause fold that was located northwest of the UK on 20 October 2008 was simulated using the Met Office Unified Model (MetUM) in a global domain (with ~40km horizontal grid spacing in midlatitudes) and in a limited-area domain (with 12 km horizontal grid spacing). A set of Lagrangian PV tracers were integrated online. Each tracer accumulated and advected sources of PV from a specific modelled process (e.g., convection scheme, long-wave radiation, boundary-layer scheme, cloud microphysics). A key finding of this work is that diabatic PV was minimised along the 2 pvu tropopause. A dipole of diabatic PV straddled the tropopause with an increase (decrease) in PV above (beneath) the elevation of the tropopause. The positive diabatic PV above the tropopause was contributed primarily by long-wave radiative cooling, and the negative PV beneath the tropopause was contributed by the convection and large-scale cloud schemes. The practical and theoretical implications of the increased gradient of PV at the tropopause level will be discussed.

  20. Open ocean dead zones in the tropical North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Karstensen, J.; Fiedler, B.; Schütte, F.; Brandt, P.; Körtzinger, A.; Fischer, G.; Zantopp, R.; Hahn, J.; Visbeck, M.; Wallace, D.

    2015-04-01

    Here we present first observations, from instrumentation installed on moorings and a float, of unexpectedly low (<2 μmol kg-1) oxygen environments in the open waters of the tropical North Atlantic, a region where oxygen concentration does normally not fall much below 40 μmol kg-1. The low-oxygen zones are created at shallow depth, just below the mixed layer, in the euphotic zone of cyclonic eddies and anticyclonic-modewater eddies. Both types of eddies are prone to high surface productivity. Net respiration rates for the eddies are found to be 3 to 5 times higher when compared with surrounding waters. Oxygen is lowest in the centre of the eddies, in a depth range where the swirl velocity, defining the transition between eddy and surroundings, has its maximum. It is assumed that the strong velocity at the outer rim of the eddies hampers the transport of properties across the eddies boundary and as such isolates their cores. This is supported by a remarkably stable hydrographic structure of the eddies core over periods of several months. The eddies propagate westward, at about 4 to 5 km day-1, from their generation region off the West African coast into the open ocean. High productivity and accompanying respiration, paired with sluggish exchange across the eddy boundary, create the "dead zone" inside the eddies, so far only reported for coastal areas or lakes. We observe a direct impact of the open ocean dead zones on the marine ecosystem as such that the diurnal vertical migration of zooplankton is suppressed inside the eddies.

  1. Cenozoic Transient Convective Uplift of the North Atlantic European Margin

    NASA Astrophysics Data System (ADS)

    Hartley, Ross; Roberts, Gareth; White, Nicky

    2013-04-01

    Given that the Rayleigh number of the convecting mantle is 106 to 108, instabilities should occur over a range of length and time scales (100-1000 km, 0.1-100 Myr). Tomographic measurements of seismic wave velocities in the mantle, long wavelength gravity observations, surface elevation and the geochemical signature of volcanism can be used to reveal the existence of convective upwellings. Beneath the North Atlantic Ocean, there is evidence to suggest that the region has been affected, for the last 60 Myr, by the presence of an upwelling plume, which is currently centred beneath Iceland. Short-lived (i.e. < 1 Myr) variations in temperature of 10-100 °C are inferred from the pattern of bathymetry and short wavelength gravity south of Iceland, where a series of V-shaped ridges occur. These temperature variations should give rise to an associated variation in dynamic support of the overlying plate and result in vertical motion of the surface over timescales of < 1 Myr. Interpretation of 3D seismic reflection data from the Faroe Shetland Basin, a Cenozoic sedimentary basin located 200 km north of the British Isles, has revealed a spectacular terrestrial unconformity dated at ~55 Ma, today buried under up to 2 km of sediment in water depths of up to 1km. The existence of this unconformity indicates that the basin underwent up to 1 km of uplift in 1 Myr followed by subsidence of 1 km in 1 Myr. There is also evidence for magmatic and volcanic activity in the basin at these times. These vertical motions can be attributed to the passage of a thermal plume transient beneath the basin. Inversion of longitudinal river profiles which drained this sub-aerial landscape allows a detailed history of uplift to be calculated. This uplift history reveals that the basin was uplifted in three stages with maximum uplift rates of 3 km Myr-1. Therefore, the plume transient must have had a complicated thermal and/or chemical structure. Evidence for heterogeneity in the mantle over these

  2. Tropical North Atlantic ocean-atmosphere interactions synchronize forest carbon losses from hurricanes and Amazon fires

    NASA Astrophysics Data System (ADS)

    Chen, Yang; Randerson, James T.; Morton, Douglas C.

    2015-08-01

    We describe a climate mode synchronizing forest carbon losses from North and South America by analyzing time series of tropical North Atlantic sea surface temperatures (SSTs), landfall hurricanes and tropical storms, and Amazon fires during 1995-2013. Years with anomalously high tropical North Atlantic SSTs during March-June were often followed by a more active hurricane season and a larger number of satellite-detected fires in the southern Amazon during June-November. The relationship between North Atlantic tropical cyclones and southern Amazon fires (r = 0.61, p < 0.003) was stronger than links between SSTs and either cyclones or fires alone, suggesting that fires and tropical cyclones were directly coupled to the same underlying atmospheric dynamics governing tropical moisture redistribution. These relationships help explain why seasonal outlook forecasts for hurricanes and Amazon fires both failed in 2013 and may enable the design of improved early warning systems for drought and fire in Amazon forests.

  3. Mid-Pliocene planktic foraminifer assemblage of the North Atlantic Ocean

    USGS Publications Warehouse

    Dowsett, H.J.; Robinson, M.M.

    2007-01-01

    The US Geological Survey Pliocene Research, Interpretation and Synoptic Mapping (PRISM) North Atlantic faunal data set provides a unique, temporally constrained perspective to document and evaluate the quantitative geographic distribution of key mid-Pliocene taxa. Planktic foraminifer census data from within the PRISM time slab (3.29 to 2.97 Ma) at thirteen sites in the North Atlantic Ocean have been analyzed. We have compiled Scanning Electron Micrographs for an atlas of mid-Pliocene assemblages from the North Atlantic with descriptions of each taxon to document the taxonomic concepts that accompany the PRISM data. In mid-Pliocene assemblages, the geographic distributions of extant taxa are similar to their present day distributions, although some are extended to the north. We use the distribution of extinct taxa to assess previous assumptions regarding environmental preferences.

  4. Using European Systems from a North American Library.

    ERIC Educational Resources Information Center

    Clinton, Marshall; Grenville, Sally

    1980-01-01

    Illustrates the special considerations of using European search systems from North America: steps in establishing a telephone link with the European Space Agency's system, lack of availability to North Americans of some European databases through this system, user reaction, and costs. Brief descriptions of some European databases and a connect…

  5. North American Ground Surface Temperature Histories: A Contribution to the PAGES2k North American Project

    NASA Astrophysics Data System (ADS)

    Mareschal, J. C.; Jaume Santero, F.; Beltrami, H.

    2015-12-01

    Within the framework of the PAGES NorthAmerica2k project, three hundred and seventy three (373) North American temperature-depth profiles from boreholes deeper than 300 meters were analyzed for recent climate. To facilitate comparisons and examine the same time period, the profiles were truncated at 300 m. The ground surface temperature (GST) histories for the last 500 years were inverted from the subsurface temperature anomalies using singular value decomposition for a model of 10 temperature changes along time-intervals of increasing duration. The inversion retains four singular values and accounts for the data acquisition time difference. The reference surface temperature and geothermal gradient were estimated by linear regression to the deepest 100 meters with a 95% confidence interval. Additionally, a Monte-Carlo method was used to find the range of solutions within a maximum subsurface anomaly error determined by the root mean square between the model and the data. The GST history results for North America, given by the mean and 95% confidence interval, reveal in most cases, a warming up to 1°C - 2.5°C during the last 100-150 years.

  6. North Atlantic Ocean control on surface heat flux on multidecadal timescales.

    PubMed

    Gulev, Sergey K; Latif, Mojib; Keenlyside, Noel; Park, Wonsun; Koltermann, Klaus Peter

    2013-07-25

    Nearly 50 years ago Bjerknes suggested that the character of large-scale air-sea interaction over the mid-latitude North Atlantic Ocean differs with timescales: the atmosphere was thought to drive directly most short-term--interannual--sea surface temperature (SST) variability, and the ocean to contribute significantly to long-term--multidecadal--SST and potentially atmospheric variability. Although the conjecture for short timescales is well accepted, understanding Atlantic multidecadal variability (AMV) of SST remains a challenge as a result of limited ocean observations. AMV is nonetheless of major socio-economic importance because it is linked to important climate phenomena such as Atlantic hurricane activity and Sahel rainfall, and it hinders the detection of anthropogenic signals in the North Atlantic sector. Direct evidence of the oceanic influence of AMV can only be provided by surface heat fluxes, the language of ocean-atmosphere communication. Here we provide observational evidence that in the mid-latitude North Atlantic and on timescales longer than 10 years, surface turbulent heat fluxes are indeed driven by the ocean and may force the atmosphere, whereas on shorter timescales the converse is true, thereby confirming the Bjerknes conjecture. This result, although strongest in boreal winter, is found in all seasons. Our findings suggest that the predictability of mid-latitude North Atlantic air-sea interaction could extend beyond the ocean to the climate of surrounding continents.

  7. Reduced North Atlantic Deep Water flux to the glacial Southern Ocean inferred from neodymium isotope ratios

    PubMed

    Rutberg; Hemming; Goldstein

    2000-06-22

    The global circulation of the oceans and the atmosphere transports heat around the Earth. Broecker and Denton suggested that changes in the global ocean circulation might have triggered or enhanced the glacial-interglacial cycles. But proxy data for past circulation taken from sediment cores in the South Atlantic Ocean have yielded conflicting interpretations of ocean circulation in glacial times--delta13C variations in benthic foraminifera support the idea of a glacial weakening or shutdown of North Atlantic Deep Water production, whereas other proxies, such as Cd/Ca, Ba/Ca and 231Pa/230Th ratios, show little change from the Last Glacial Maximum to the Holocene epoch. Here we report neodymium isotope ratios from the dispersed Fe-Mn oxide component of two southeast Atlantic sediment cores. Both cores show variations that tend towards North Atlantic signatures during the warm marine isotope stages 1 and 3, whereas for the full glacial stages 2 and 4 they are closer to Pacific Ocean signatures. We conclude that the export of North Atlantic Deep Water to the Southern Ocean has resembled present-day conditions during the warm climate intervals, but was reduced during the cold stages. An increase in biological productivity may explain the various proxy data during the times of reduced North Atlantic Deep Water export. PMID:10879531

  8. Deglacial Subsurface Temperature Change in the Tropical North Atlantic Linked to Atlantic Meridional Overturning Circulation Variability

    NASA Astrophysics Data System (ADS)

    Schmidt, M. W.; Chang, P.; Otto-Bliesner, B. L.

    2010-12-01

    Coupled ocean-atmosphere modeling experiments indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly coupled to abrupt tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes (Zhang, 2007; Chang et al., 2008; and Chiang et al., 2008). While a slowdown of AMOC in these experiments results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger warming due to rapid reorganizations of ocean circulation patterns (Wan et al., 2009). In addition, observational records of detrended 20th century ocean temperature and salinity variability show a strong anticorrelation between surface cooling and subsurface warming in the TNA over the past several decades, suggesting changing vertical temperature gradients in this region may be a distinct fingerprint of AMOC variability (Zhang 2007). In order to test the hypothesis that subsurface temperature change in the TNA is coupled to AMOC variability across abrupt climate events over the last deglacial, we reconstructed high-resolution Mg/Ca-temperature and δ18O records from both surface (G. ruber) and sub-thermocline dwelling (G. truncatulinoides, 350-500 m depth and G. crassaformis, 450-580 m) planktonic foraminifera in the southern Caribbean Sea sediment core VM12-107 (11.33oN, 66.63oW; 1079 m; 18 cm/kyr sedimentation rate). Sea surface temperatures indicate a gradual warming in the TNA starting at ~19 kyr BP with small cold reversals of ~1.5oC during Heinrich Event 1 (H1) and the Younger Dryas (YD). In contrast, last glacial maximum subsurface temperatures were as much as 2.5oC warmer than Late Holocene values and H1 and the YD are marked by the warmest subsurface temperatures characterized by abrupt temperature increases as large as 4-5oC. Furthermore, a comparison of our subsurface temperature record with the Bermuda Rise 231Pa/230Th proxy record of AMOC variability (McManus et al., 2004) indicates a strong

  9. Prediction of interannual North Atlantic sea surface temperature and its remote influence over land

    NASA Astrophysics Data System (ADS)

    Lienert, Fabian; Doblas-Reyes, Francisco J.

    2016-07-01

    The quality of a multimodel of six coupled climate forecast systems initialized with observations—relative to the accompanying uninitialized system—to re-forecast the future annual-mean North Atlantic sea surface temperature (SST) departures is described. The study concludes that, measured by the anomaly correlation (AC) skill, the evolution of the leading two empirical orthogonal function modes of North Atlantic SSTs are skillfully forecast throughout the 9-year forecast range. This skill results in part from the predictions of the trend. The skill of the detrended modes, i.e., in absence of SST variability generated by the trend, is reduced, but still statistically distinguishable from zero throughout the 9-year forecast for the first mode and exclusively in the first two forecast years for the second mode. The initialization effect on the AC skill in the initialized system is statistically distinguishable from the one without initialization for the detrended first mode during the first three forecast years and the first forecast year only when the trend in North Atlantic SSTs is included. All six initialized systems of the multimodel are capable to skillfully forecast the shift of the full first mode of North Atlantic SST anomalies in the mid 1990s at all leads with HadCM 3 and EC-Earth 2.3 outperforming other systems. All systems share an intrinsic bias in simulating annual-mean SST variability in the North Atlantic. The study finds that the area-average AC skill (i.e., of a forecast containing regional information) of the North Atlantic influence on anomalous European temperature in the initialized multimodel is positive and statistically distinguishable from zero throughout the 9-year forecast for the full field case. On the other hand, a continent-wide forecast (i.e., without any regional information) of future European precipitation departures associated with North Atlantic SST variability is skillful throughout the 9-year forecast for the full field

  10. The East Atlantic - West Russia Teleconnection in the North Atlantic: Climate Impact and Relation to Rossby Wave Propagation

    NASA Technical Reports Server (NTRS)

    Lim, Young-Kwon

    2014-01-01

    Large-scale winter teleconnection of the East Atlantic - West Russia (EA-WR) over the Atlantic and surrounding regions is examined in order to quantify its impacts on temperature and precipitation and identify the physical mechanisms responsible for its existence. A rotated empirical orthogonal function (REOF) analysis of the upper-tropospheric monthly height field captures successfully the EA-WR pattern and its interannual variation, with the North Atlantic Oscillation as the first mode. EA-WRs climate impact extends from eastern North America to Eurasia. The positive (negative) EA-WR produces positive (negative) temperature anomalies over the eastern US, western Europe and Russia east of Caspian Sea, with negative (positive) anomalies over eastern Canada, eastern Europe including Ural Mountains and the Middle East. These anomalies are largely explained by lower-tropospheric temperature advections. Positive (negative) precipitation anomalies are found over the mid-latitude Atlantic and central Russia around 60E, where lower-level cyclonic (anticyclonic) circulation anomaly is dominant. The eastern Canada and the western Europe are characterized by negative (positive) precipitation anomalies.The EA-WR is found to be closely associated with Rossby wave propagation. Wave activity fluxes show that it is strongly tied to large-scale stationary waves. Furthermore, a stationary wave model (SWM) forced with vorticity transients in the mid-latitude Atlantic (approximately 40N) or diabatic heat source over the subtropical Atlantic near the Caribbean Sea produces well-organized EA-WR-like wave patterns, respectively. Sensitivity tests with the SWM indicate improvement in the simulation of the EA-WR when the mean state is modified to have a positive NAO component that enhances upper-level westerlies between 40-60N.

  11. Impact of the North Atlantic sea surface temperature tripole on the East Asian summer monsoon

    NASA Astrophysics Data System (ADS)

    Zuo, Jinqing; Li, Weijing; Sun, Chenghu; Xu, Li; Ren, Hong-Li

    2013-07-01

    A strong (weak) East Asian summer monsoon (EASM) is usually concurrent with the tripole pattern of North Atlantic SST anomalies on the interannual timescale during summer, which has positive (negative) SST anomalies in the northwestern North Atlantic and negative (positive) SST anomalies in the subpolar and tropical ocean. The mechanisms responsible for this linkage are diagnosed in the present study. It is shown that a barotropic wave-train pattern occurring over the Atlantic-Eurasia region likely acts as a link between the EASM and the SST tripole during summer. This wave-train pattern is concurrent with geopotential height anomalies over the Ural Mountains, which has a substantial effect on the EASM. Diagnosis based on observations and linear dynamical model results reveals that the mechanism for maintaining the wave-train pattern involves both the anomalous diabatic heating and synoptic eddy-vorticity forcing. Since the North Atlantic SST tripole is closely coupled with the North Atlantic Oscillation (NAO), the relationships between these two factors and the EASM are also examined. It is found that the connection of the EASM with the summer SST tripole is sensitive to the meridional location of the tripole, which is characterized by large seasonal variations due to the north-south movement of the activity centers of the NAO. The SST tripole that has a strong relationship with the EASM appears to be closely coupled with the NAO in the previous spring rather than in the simultaneous summer.

  12. Did the North Atlantic Ocean sequester more CO2 during the last glacial?

    NASA Astrophysics Data System (ADS)

    Yu, J.; Thornalley, D. J.; Jin, Z.; Rohling, E. J.; Menviel, L.; McCave, I. N. N.

    2015-12-01

    To explain the ~90 ppm lower atmospheric CO2 content during the Last Glacial Maximum, much effort has been focused on the mechanisms that helped to limit the outgassing of CO2 from the deep ocean to the atmosphere via the Southern Ocean. Field measurements and modeling studies suggest that the North Atlantic Ocean has been an important sink of CO2 during preindustrial and modern times. However, the role of the North Atlantic in sequestering atmospheric CO2 in the past largely remains unconstrained. Here, we use a suite of geochemical proxies to reconstruct nutrient and carbonate ion concentrations of both surface and deep waters in the North Atlantic during the last ~25 kyr. When normalized to the same nutrient levels, we find that the gradient in carbonate ion content between surface and mid-depth waters increased during the last glacial. Although a combination of factors including changes in Redfield ratio and rain ratio and increased CO2 absorption at the air-sea boundary might have caused the observed change, the greater gradient most likely suggests an enhanced sequestration of CO2 in the North Atlantic Ocean during the Last Glacial Maximum. Therefore, we infer that, in addition to changes in the Southern Ocean, processes in the North Atlantic Ocean enhanced the uptake of CO2 and synergistically contributed to the low atmospheric CO2 during ice ages.

  13. Tropical-Subpolar Linkages in the North Atlantic during the last Glacial Period

    NASA Astrophysics Data System (ADS)

    Vautravers, M. J.; Hodell, D. A.

    2010-12-01

    We studied millennial-scale changes in planktonic foraminifera assemblages from the last glacial period in a high-resolution core (KN166-14-JPC13) recovered from the southern part of the Gardar Drift in the subpolar North Atlantic. Similar to recent findings reported by Jonkers et al. (2010), we also found that the sub-polar North Atlantic Ocean experienced some seasonal warming during each of the Heinrich Events (HEs). In addition, increasing abundances of tropical species are found just prior to the IRD event marking the end of each Bond cycle, suggesting that summer warming may have been involved in triggering Heinrich events. We suggest that tropical-subtropical water transported via the Gulf Stream and North Atlantic Drift may have triggered the collapse of large NH ice-shelves. Sharp decreases in polar species are tied to abrupt warming following Heinrich Events as documented in Greenland Ice cores and other marine records in the North Atlantic. The record bears a strong resemblance to the tropical record of Cariaco basin (Peterson et al., 2000), suggesting strong tropical-subpolar linkages in the glacial North Atlantic. Enhanced spring productivity, possibly related to eddy activity along the Subpolar Front, is recorded by increased shell size, high δ13C in G. bulloides and other biological indices early during the transition from HE stadials to the following interstadial.

  14. Meridional Overturning circulation at 26N and the North Atlantic heat COntent (MONACO)

    NASA Astrophysics Data System (ADS)

    Wells, Neil C.; Hirschi, Joel; Ivchenko, Vladimir; King, Brian; Josey, Simon

    2010-05-01

    The main goal of MONACO is to understand the links between the meridional overturning circulation (MOC) and the meridional heat transport (MHT) from the RAPID-WATCH observing system, and the subannual to interannual variability of oceanic heat content (OHC) inferred from Argo floats and sea surface temperatures (SSTs) in the North Atlantic. We have calculated the MHT variability in the North Atlantic for the 1999 to 2009 period, and the MOC observations are available from April 2004 to April 2008. The largest OHC signal is the seasonal cycle. Its amplitude and phase is similar to the seasonal heat uptake and release through the air-sea heat fluxes. However, North Atlantic MHT changes and air-sea fluxes can differ by more than 1PW (1015W) for periods extending over several months, suggesting that MHT fluctuations may leave a sizable imprint on the OHC. Lag correlations between deseasoned OHC and MOC variability suggest that the MOC is leading North Atlantic OHC changes by about 8 months. Similarly, we find that MOC leads the development of a tripolar SST pattern in the North Atlantic by 6 months. However, since these correlations are based on the short April 2004 and April 2008 period, and it is not clear yet whether the observed MOC - OHC, and MOC - SST links are robust.

  15. Statistical Aspects of Tropical Cyclone Activity in the North Atlantic Basin, 1945-2010

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    2012-01-01

    Examined are statistical aspects of the 715 tropical cyclones that formed in the North Atlantic basin during the interval 1945-2010. These 715 tropical cyclones include 306 storms that attained only tropical storm strength, 409 hurricanes, 179 major or intense hurricanes, and 108 storms that struck the US coastline as hurricanes. Comparisons made using 10-year moving average (10-yma) values between tropical cyclone parametric values and surface air and ENSO-related parametric values indicate strong correlations to exist, in particular, against the Armagh Observatory (Northern Ireland) surface air temperature, the Atlantic Multi-decadal Oscillation (AMO) index, the Atlantic Meridional Mode (AMM) index, and the North Atlantic Oscillation (NAO) index, in addition to the Oceanic Ni o index (ONI) and Quasi-Biennial Oscillation (QBO) indices. Also examined are the decadal variations of the tropical cyclone parametric values and a look ahead towards the 2012 hurricane season and beyond.

  16. Connection between South Mediterranean climate and North African atmospheric circulation during the last 50,000 yr BP North Atlantic cold events

    NASA Astrophysics Data System (ADS)

    Bout-Roumazeilles, V.; Combourieu Nebout, N.; Peyron, O.; Cortijo, E.; Landais, A.; Masson-Delmotte, V.

    2007-12-01

    High-resolution clay mineralogical analyses were performed on sediment deposited during the last 50,000 yr in the Alboran sea (ODP Site 976). The clay mineral record is compared with pollen assemblages and with annual precipitation (Pann) and mean temperatures of the coldest month (MTCO) reconstructed with the modern analog technique (MAT). Enhanced contribution of palygorskite, a typical wind-blown clay mineral, characterizes the North Atlantic cold climatic events. Coeval development of the semi-arid vegetation (Artemisia rich) associated with a drastic fall of reconstructed precipitations and temperatures, suggest cold and arid continental conditions in the West Mediterranean area during North Atlantic cold events. The clay mineral association, especially the palygorskite content and the illite-to-kaolinite ratio, indicate western Morocco as one of the major source of the clay-size fraction during the North Atlantic cold events. The maximum abundance of Artemisia associated with the presence of Argania pollen both indicate Morocco as the main origin for pollen during these cold periods. The comparison of these pollen and clay mineral-specific features allows us to pinpoint western Morocco as the dominant source of wind-blown particles during North Atlantic cold events. These specific mineralogical composition and palynological assemblages reveal enhanced aridity over North Africa and intensification of winds favouring dust erosion and transport from North Africa toward the Alboran Sea during the North Atlantic cold events. According to atmospheric models, such a meridian transport (1) likely results from the development of strong and stable anticyclonic conditions over the tropical Atlantic and North Africa, similar to today's summer meteorological configuration and (2) implies a northward position of the westerly winds during North Atlantic cold events. Finally the synoptic situation over the West Mediterranean during the North Atlantic cold events is compared

  17. Mantle Redox Conditions in the North Atlantic Igneous Province

    NASA Astrophysics Data System (ADS)

    Heister, L. E.; Gras, M. A.; Lesher, C. E.

    2004-12-01

    The North Atlantic igneous province (NAIP) has long been viewed as a region of anomalous mantle upwelling related to plume activity, continental rifting, and a heterogeneous mantle source. Prior to continental rifting in the Tertiary, the northern portion of the region was the site of closure of the Iapetus ocean basin. This tectonic event may have contributed to heterogeneities within the upper mantle and altered its oxidation state relative to the ambient mantle. Vanadium has been shown to be a useful indicator of redox conditions due to its multiple valence states (e.g. [1-2]). In mantle minerals, vanadium becomes increasingly incompatible under more oxidizing conditions [3]. Because both scandium and vanadium are moderately incompatible during melting, the Sc/V ratio of primitive basalts can be used to investigate the oxidation state of the mantle [1-3]. We have examined the Sc/V ratios of primitive lavas from the mid-Atlantic ridge (MAR), Iceland, and the East Greenland margin to determine if there are spatial or temporal variations in the oxidation state of the NAIP mantle. The Sc/V ratios for MAR basalts are 0.13-0.20 (GEOROC chemical database); while Icelandic basalts range from 0.10-0.25 with an average of 0.16 (1 σ =0.05). The entire range of Sc/V ratios of the Paleogene East Greenland basalts is 0.07-0.17 with an average of 0.10 (1 σ = 0.05). The Sc/V ratios of Icelandic basalts are similar to MAR basalts, but the East Greenland lavas are distinctly lower than both the MAR and Iceland. The Sc/V ratio also can vary as a function of mean pressure of melting (i.e. spinel versus garnet lherzolite). To test the relative importance of melting systematics, source composition, and oxygen fugacity on the Sc/V systematics for NAIP basalts, we incorporated the oxygen-fugacity-dependent V mineral-melt partitioning data of [3] into the polybaric decompression melting model REEBOX [4]. The best-fit model parameters for the majority of the Iceland and MAR basalts

  18. 75 FR 35432 - Atlantic Highly Migratory Species; North and South Atlantic Swordfish Quotas

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-22

    ... fishing for swordfish in the Atlantic Ocean, including the Caribbean Sea and Gulf of Mexico, by... 5, 2007 (72 FR 56929). The proposed adjusted quota for the South Atlantic swordfish, after... certification reads: NMFS published a final rule on October 5, 2007 (72 FR 56929) that established the...

  19. 78 FR 12705 - Atlantic Highly Migratory Species; North and South Atlantic 2013 Commercial Swordfish Quotas

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-25

    ... in the Atlantic Ocean, including the Caribbean Sea and Gulf of Mexico. This action implements ICCAT... coastal states on the Atlantic including the Gulf of Mexico and the Caribbean Sea. Pursuant to 15 CFR 930... prepared for the 2012 Swordfish Quota Specifications Final Rule (July 31, 2012; 77 FR 45273). The...

  20. Dynamics of North Atlantic Deep Water masses during the Holocene

    NASA Astrophysics Data System (ADS)

    Hoogakker, Babette A. A.; Chapman, Mark R.; McCave, I. Nick; Hillaire-Marcel, Claude; Ellison, Christopher R. W.; Hall, Ian R.; Telford, Richard J.

    2011-12-01

    High resolution flow speed reconstructions of two core sites located on Gardar Drift in the northeast Atlantic Basin and Orphan Knoll in the northwest Atlantic Basin reveal a long-term decrease in flow speed of Northeast Atlantic Deep Water (NEADW) after 6,500 years. Benthic foraminiferal oxygen isotopes of sites currently bathed in NEADW show a 0.2‰ depletion after 6,500 years, shortly after the start of the development of a carbon isotope gradient between NEADW and Norwegian Sea Deep Water. We consider these changes in near-bottom flow vigor and benthic foraminiferal isotope records to mark a significant reorganization of the Holocene deep ocean circulation, and attribute the changes to a weakening of NEADW flow during the mid to late Holocene that allowed the shoaling of Lower Deep Water and deeper eastward advection of Labrador Sea Water into the northeast Atlantic Basin.

  1. Did accelerated North American ice sheet melt contribute to the 8.2 ka cooling event ?

    NASA Astrophysics Data System (ADS)

    Matero, Ilkka S. O.; Gregoire, Lauren J.; Ivanović, Ruža F.; Tindall, Julia C.; Haywood, Alan M.

    2016-04-01

    The 8.2 ka event was an abrupt cooling of the Northern Hemisphere 8,200 years ago. It is an almost ideal case study to benchmark the sensitivity of climate models to freshening of the North Atlantic by ice sheet melt (Schmidt and LeGrande, 2005). The event is attributed to the outburst of North American proglacial lakes into the Labrador Sea, causing a slow-down in Atlantic overturning circulation and cooling of 1-2.5 °C around the N. Atlantic (Alley and Ágústsdóttir,2005). Climate models fail to simulate the ~150 year duration of the event when forced with a sudden (0.5 to 5 years) drainage of the lakes (Morrill et al., 2013a). This could be because of missing forcings. For example, the separation of ice sheet domes around the Hudson Bay is thought to have produced a pronounced acceleration in ice sheet melt through a saddle collapse mechanism around the time of the event (Gregoire et al., 2012). Here we investigate whether this century scale acceleration of melt contributed to the observed climatic perturbation, using the coupled Ocean-Atmosphere climate model HadCM3. We designed and ran a set of simulations with temporally variable ice melt scenarios based on a model of the North American ice sheet. The simulated magnitude and duration of the cold period is controlled by the duration and amount of freshwater introduced to the ocean. With a 100-200 year-long acceleration of ice melt up to a maximum of 0.61 Sv, we simulate 1-3 °C cooling in the North Atlantic and ~0.5-1 °C cooling in Continental Europe; which are similar in magnitude to the ~1-2 °C cooling estimated from records for these areas (Morrill et al., 2013b). Some of the observed features are however not reproduced in our experiments, such as the most pronounced cooling of ~6 °C observed in central Greenland (Alley and Ágústsdóttir, 2005). The results suggest that the ~150 year North Atlantic and European cooling could be caused by ~200 years of accelerated North American ice sheet melt. This

  2. Intensified impact of tropical Atlantic SST on the western North Pacific summer climate under a weakened Atlantic thermohaline circulation

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Lee, June-Yi; Lu, Riyu; Dong, Buwen; Ha, Kyung-Ja

    2015-10-01

    The tropical North Atlantic (TNA) sea surface temperature (SST) has been identified as one of regulators on the boreal summer climate over the western North Pacific (WNP), in addition to SSTs in the tropical Pacific and Indian Oceans. The major physical process proposed is that the TNA warming induces a pair of cyclonic circulation anomaly over the eastern Pacific and negative precipitation anomalies over the eastern to central tropical Pacific, which in turn lead to an anticyclonic circulation anomaly over the western to central North Pacific. This study further demonstrates that the modulation of the TNA warming to the WNP summer climate anomaly tends to be intensified under background of the weakened Atlantic thermohaline circulation (THC) by using a water-hosing experiment. The results suggest that the weakened THC induces a decrease in thermocline depth over the TNA region, resulting in the enhanced sensitivity of SST variability to wind anomalies and thus intensification of the interannual variation of TNA SST. Under the weakened THC, the atmospheric responses to the TNA warming are westward shifted, enhancing the anticyclonic circulation and negative precipitation anomaly over the WNP. This study supports the recent finding that the negative phase of the Atlantic multidecadal oscillation after the late 1960s has been favourable for the strengthening of the connection between TNA SST variability and WNP summer climate and has important implications for seasonal prediction and future projection of the WNP summer climate.

  3. A description of the tides in the Eastern North Atlantic

    NASA Astrophysics Data System (ADS)

    Fanjul, Enrique Alvarez; Gómez, Begoña Pérez; Sánchez-Arévalo, Ignacio Rodríguez

    A description of the Eastern North Atlantic tidal dynamics (in a region spanning from 20°N to 48°N in latitude and from 34°W to 0° in longitude) is obtained by means of new in situ measurements and numerical modelling based on TOPEX/POSEIDON-derived data sets. The main source of measurements is the tide gauge network REDMAR (RED de MAReógrafos de Puertos del Estado), operative since July 1992 and managed by Clima Marítimo (Puertos del Estado). Results derived from the harmonic analysis of the first years of measurements are presented and compared with model results. In order to obtain a global picture of the tides in the region, a large compilation of harmonic constants obtained from other institutes is included. The availability of new TOPEX/POSEIDON-derived harmonic constants data sets provides a chance to include the benefits derived from satellite altimetry in high resolution regional applications of numerical models. Richard Ray's tidal model (Ray et al., 1994), based on a response type tidal analysis of TOPEX/POSEIDON data, was employed within a model of the studied area. The numerical model employed is HAMSOM, a 3-D finite difference code developed both by the Institut für Meereskunde (Hamburg University) and Clima Marítimo. Results from simulations of seven major harmonics are presented, providing a comprehensive view of tidal dynamics, including current information. The results of tidal simulations show good agreement between semidiurnal harmonic components and the values measured by both coastal and pelagic tidal gauges and by current meters. The modelled diurnal constituents show larger relative differences with measurements than semidiurnal harmonics, especially concerning the phase lags. The non-linear transfer of energy from semidiurnal to higher order harmonics, such as M 4 and M 6, was mapped. Those transfers were found to be important only in two areas: the French continental shelf in the Bay of Biscay and the widest part of the African

  4. North Atlantic Margins: Case studies of Magmatic Continental Breakup

    NASA Astrophysics Data System (ADS)

    Eccles, J. D.; White, R. S.; Christie, P. A. F.

    2012-04-01

    Continental breakup between Europe and Greenland was accompanied by the rapid eruption of the > 1 million cubic kilometres of extruded basalts forming North Atlantic Igneous Province. With episodes of extension in the region dating back to the Devonian, rifting finally proceeded to full breakup and oceanic spreading in the Paleocene. Flood basalt units flowed up to 150 km over pre-existing sedimentary basins, discrete volcanic centres formed and intrusion into the thinned continental crust occurred. Marine seismic investigations utilising industry-leading seismic reflection imaging technologies and large deployments of ocean bottom seismometers across the Faroes and Hatton Bank margins have been used to better resolve margin structure and composition, improving our understanding of breakup processes. Seismic reflection imaging reveals sub-aerial and submarine seaward-dipping reflector sequences tracking the interplay of uplift (transient and permanent), crustal loading through extrusion and ongoing extension. Lower crustal reflectors, cross-cutting the continental fabric and interpreted as intrusions, are observed within the narrow continent-ocean transition. P-wave tomography of wide-angle reflections and refractions, recorded to offsets of up to ~200 km, reveals unusually thick oceanic crust with lower crustal velocities in excess of those expected for MORB compositions. High P-wave velocities are attributed to magnesium-rich compositions which, combined with the large oceanic crustal thickness, would be consistent with an elevated mantle temperature (~150°C higher than 'normal') at the time of breakup. Vp/Vs ratios derived from tomography of converted shear wave phases also support high magnesium melt composition. P-wave velocities and Vp/Vs ratios across the continent-ocean transition show a mixing trend between magnesium-rich gabbroic compositions (100% for oceanic crust) and compositions consistent with the Lewisian gneiss basement or Early Proterozoic

  5. Alkalinity distribution in the western North Atlantic Ocean margins

    NASA Astrophysics Data System (ADS)

    Cai, Wei-Jun; Hu, Xinping; Huang, Wei-Jen; Jiang, Li-Qing; Wang, Yongchen; Peng, Tsung-Hung; Zhang, Xin

    2010-08-01

    Total alkalinity (TA) distribution and its relationship with salinity (S) along the western North Atlantic Ocean (wNAO) margins from the Labrador Sea to tropical areas are examined in this study. Based on the observed TA-S patterns, the mixing processes that control alkalinity distribution in these areas can be categorized into a spectrum of patterns that are bracketed by two extreme mixing types, i.e., alongshore current-dominated and river-dominated. Alongshore current-dominated mixing processes exhibit a segmented mixing line with a shared mid-salinity end-member. In such cases (i.e., Labrador Sea, Gulf of Maine, etc.), the y-intercept of the high salinity segment of the mixing line is generally higher than the local river alkalinity values, and it reflects the mixing history of the alongshore current. In contrast, in river-dominated mixing (Amazon River, Caribbean Sea, etc.), good linear relationships between alkalinity and salinity are generally observed, and the zero salinity intercepts of the TA-S regressions roughly match those of the regional river alkalinity values. TA-S mixing lines can be complicated by rapid changes in the river end-member value and by another river nearby with a different TA value (e.g., Mississippi-Atchafalaya/Gulf of Mexico). In the wNAO margins, regression intercepts and river end-members have a clear latitudinal distribution pattern, increasing from a low of ˜300 μmol kg-1 in the Amazon River plume to a high value between ˜500-1100 μmol kg-1 in the middle and high latitude margins. The highest value of ˜2400 μmol kg-1 is observed in the Mississippi River influenced areas. In addition to mixing control, biological processes such as calcification and benthic alkalinity production may also affect ocean margin alkalinity distribution. Therefore, deriving inorganic carbon system information in coastal oceans using alkalinity-salinity relationships, in particular, those of generic nature, may lead to significant errors.

  6. Variability of Fram Strait Ice Flux and North Atlantic Oscillation

    NASA Technical Reports Server (NTRS)

    Kwok, Ron

    1999-01-01

    An important term in the mass balance of the Arctic Ocean sea ice is the ice export. We estimated the winter sea ice export through the Fram Strait using ice motion from satellite passive microwave data and ice thickness data from moored upward looking sonars. The average winter area flux over the 18-year record (1978-1996) is 670,000 square km, approximately 7% of the area of the Arctic Ocean. The winter area flux ranges from a minimum of 450,000 sq. km in 1984 to a maximum of 906,000 sq km in 1995. The daily, monthly and interannual variabilities of the ice area flux are high. There is an upward trend in the ice area flux over the 18-year record. The average winter volume flux over the winters of October 1990 through May 1995 is 1745 cubic km ranging from a low of 1375 cubic km in 1990 to a high of 2791 cubic km in 1994. The sea-level pressure gradient across the Fram Strait explains more than 80% of the variance in the ice flux over the 18-year record. We use the coefficients from the regression of the time-series of area flux versus pressure gradient across the Fram Strait and ice thickness data to estimate the summer area and volume flux. The average 12-month area flux and volume flux are 919,000 sq km and 2366 cubic km. We find a significant correlation (R =0.86) between the area flux and positive phases of the North Atlantic Oscillation (NAO) index over the months of December through March. Correlation between our six years of volume flux estimates and the NAO index gives R =0.56. During the high NAO years, a more intense Icelandic low increases the gradient in the sea-level pressure by almost 1 mbar across the Fram Strait thus increasing the atmospheric forcing on ice transport. Correlation is reduced during the negative NAO years because of decreased dominance of this large-scale atmospheric pattern on the sea-level pressure gradient across the Fram Strait. Additional information is contained in the original.

  7. Use of stable lead isotopes to characterize the sources of anthropogenic lead in North Atlantic surface waters

    SciTech Connect

    Veron, A.J. Univ. of Delaware, Newark, DE ); Church, T.M. ); Patterson, C.C. ); Flegal, A.R. Univ. of California, Santa Cruz, CA )

    1994-08-01

    Stable lead isotopes are used to illustrate the impact of surface water circulation on dissolved lead distribution in North Atlantic surface waters during oligotrophic conditions. Using stable lead isotopic signatures from (1) the Sargasso Sea and (2) direct tropospheric deposition to the North Atlantic, the authors estimate that 10-40% of the lead accumulated in surface waters of the European Basin is transported from the western North Atlantic by the North Atlantic Current. South of 50[degrees]N, lead appears to be primarily distributed by the Subtropical North Atlantic Gyre that extends well beyond the western basins to 30[degrees]W in the North African Basin (at 30-40[degrees]N). There are different lead isotopic signatures between the subtropical gyre of the Guiana and western Guinea Basins, which suggests that the Inter Tropical Convergence Zone acts as an efficient barrier limiting chemical exchanges between the gyre and the equatorial currents.

  8. Evolution of a reassortant North American gull influenza virus lineage: drift, shift and stability

    PubMed Central

    2013-01-01

    Background The role of gulls in the ecology of avian influenza (AI) is different than that of waterfowl. Different constellations of subtypes circulate within the two groups of birds and AI viruses isolated from North American gulls frequently possess reassortant genomes with genetic elements from both North America and Eurasian lineages. A 2008 isolate from a Newfoundland Great Black-backed Gull contained a mix of North American waterfowl, North American gull and Eurasian lineage genes. Methods We isolated, sequenced and phylogenetically compared avian influenza viruses from 2009 Canadian wild birds. Results We analyzed six 2009 virus isolates from Canada and found the same phylogenetic lineage had persisted over a larger geographic area, with an expanded host range that included dabbling and diving ducks as well as gulls. All of the 2009 virus isolates contained an internal protein coding set of genes of the same Eurasian lineage genes except PB1 that was from a North American lineage, and these genes continued to evolve by genetic drift. We show evidence that the 2008 Great Black-backed Gull virus was derived from this lineage with a reassortment of a North American PA gene into the more stable core set of internal protein coding genes that has circulated in avian populations for at least 2 years. From this core, the surface glycoprotein genes have switched several times creating H13N6, H13N2, and H16N3 subtypes. These gene segments were from North American lineages except for the H16 and N3 vRNAs. Conclusions This process appears similar to genetic shifts seen with swine influenza where a stable “triple reassortant internal gene” core has circulated in swine populations with genetic shifts occurring with hemaggluttinin and neuraminidase proteins getting periodically switched. Thus gulls may serve as genetic mixing vessels for different lineages of avian influenza, similar to the role of swine with regards to human influenza. These findings illustrate the

  9. Evolution of a reassortant North American gull influenza virus lineage: drift, shift and stability

    USGS Publications Warehouse

    Hall, Jeffrey S.; TeSlaa, Joshua L.; Nashold, Sean W.; Halpin, Rebecca A.; Stockwell, Timothy; Wentworth, David E.; Dugan, Vivien; Ip, Hon S.

    2013-01-01

    Background: The role of gulls in the ecology of avian influenza (AI) is different than that of waterfowl. Different constellations of subtypes circulate within the two groups of birds and AI viruses isolated from North American gulls frequently possess reassortant genomes with genetic elements from both North America and Eurasian lineages. A 2008 isolate from a Newfoundland Great Black-backed Gull contained a mix of North American waterfowl, North American gull and Eurasian lineage genes. Methods: We isolated, sequenced and phylogenetically compared avian influenza viruses from 2009 Canadian wild birds. Results: We analyzed six 2009 virus isolates from Canada and found the same phylogenetic lineage had persisted over a larger geographic area, with an expanded host range that included dabbling and diving ducks as well as gulls. All of the 2009 virus isolates contained an internal protein coding set of genes of the same Eurasian lineage genes except PB1 that was from a North American lineage, and these genes continued to evolve by genetic drift. We show evidence that the 2008 Great Black-backed Gull virus was derived from this lineage with a reassortment of a North American PA gene into the more stable core set of internal protein coding genes that has circulated in avian populations for at least 2 years. From this core, the surface glycoprotein genes have switched several times creating H13N6, H13N2, and H16N3 subtypes. These gene segments were from North American lineages except for the H16 and N3 vRNAs. Conclusions: This process appears similar to genetic shifts seen with swine influenza where a stable "triple reassortant internal gene" core has circulated in swine populations with genetic shifts occurring with hemaggluttinin and neuraminidase proteins getting periodically switched. Thus gulls may serve as genetic mixing vessels for different lineages of avian influenza, similar to the role of swine with regards to human influenza. These findings illustrate the

  10. Depth Profiles of Persistent Organic Pollutants in the North and Tropical Atlantic Ocean.

    PubMed

    Sun, Caoxin; Soltwedel, Thomas; Bauerfeind, Eduard; Adelman, Dave A; Lohmann, Rainer

    2016-06-21

    Little is known of the distribution of persistent organic pollutants (POPs) in the deep ocean. Polyethylene passive samplers were used to detect the vertical distribution of truly dissolved POPs at two sites in the Atlantic Ocean. Samplers were deployed at five depths covering 26-2535 m in the northern Atlantic and Tropical Atlantic, in approximately one year deployments. Samplers of different thickness were used to determine the state of equilibrium POPs reached in the passive samplers. Concentrations of POPs detected in the North Atlantic near the surface (e.g., sum of 14 polychlorinated biphenyls, PCBs: 0.84 pg L(-1)) were similar to previous measurements. At both sites, PCB concentrations showed subsurface maxima (tropical Atlantic Ocean -800 m, North Atlantic -500 m). Currents seemed more important in moving POPs to deeper water masses than the biological pump. The ratio of PCB concentrations in near surface waters (excluding PCB-28) between the two sites was inversely correlated with congeners' subcooled liquid vapor pressure, in support of the latitudinal fractionation. The results presented here implied a significant amount of HCB is stored in the Atlantic Ocean (4.8-26% of the global HCB environmental burdens), contrasting traditional beliefs that POPs do not reach the deep ocean. PMID:27174500

  11. Depth Profiles of Persistent Organic Pollutants in the North and Tropical Atlantic Ocean.

    PubMed

    Sun, Caoxin; Soltwedel, Thomas; Bauerfeind, Eduard; Adelman, Dave A; Lohmann, Rainer

    2016-06-21

    Little is known of the distribution of persistent organic pollutants (POPs) in the deep ocean. Polyethylene passive samplers were used to detect the vertical distribution of truly dissolved POPs at two sites in the Atlantic Ocean. Samplers were deployed at five depths covering 26-2535 m in the northern Atlantic and Tropical Atlantic, in approximately one year deployments. Samplers of different thickness were used to determine the state of equilibrium POPs reached in the passive samplers. Concentrations of POPs detected in the North Atlantic near the surface (e.g., sum of 14 polychlorinated biphenyls, PCBs: 0.84 pg L(-1)) were similar to previous measurements. At both sites, PCB concentrations showed subsurface maxima (tropical Atlantic Ocean -800 m, North Atlantic -500 m). Currents seemed more important in moving POPs to deeper water masses than the biological pump. The ratio of PCB concentrations in near surface waters (excluding PCB-28) between the two sites was inversely correlated with congeners' subcooled liquid vapor pressure, in support of the latitudinal fractionation. The results presented here implied a significant amount of HCB is stored in the Atlantic Ocean (4.8-26% of the global HCB environmental burdens), contrasting traditional beliefs that POPs do not reach the deep ocean.

  12. Gaidropsarus (Gadidae, Teleostei) of the North Atlantic Ocean: a brief phylogenetic review.

    PubMed

    Francisco, S M; Robalo, J I; Stefanni, S; Levy, A; Almada, V C

    2014-08-01

    The phylogenetic relationships among the North Atlantic Gaidropsarus and between the three Gaidropsarinae genera Gaidropsarus, Ciliata and Enchelyopus are reviewed with the hitherto most comprehensive taxonomic sampling of this group. Phylogenetic results (maximum parsimony, maximum likelihood and Bayesian inference) based on nuclear (rhodopsin) and concatenated mitochondrial (12s, 16s and cytb) markers clearly support this subfamily. For the north-eastern Atlantic species of Gaidropsarus, two previously unreported clades were strongly supported, clarifying the relationships within the genus, and revealing fewer distinct taxa in the north Atlantic Gaidropsarus than previously stipulated. The data challenge the specific status of Gaidropsarus mediterraneus and Gaidropsarus guttatus and raise doubts concerning the distinctiveness of other species. A taxonomic revision of the genus is suggested. PMID:24961593

  13. Statistical Aspects of the North Atlantic Basin Tropical Cyclones: Trends, Natural Variability, and Global Warming

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    2007-01-01

    Statistical aspects of the North Atlantic basin tropical cyclones for the interval 1945- 2005 are examined, including the variation of the yearly frequency of occurrence for various subgroups of storms (all tropical cyclones, hurricanes, major hurricanes, U.S. landfalling hurricanes, and category 4/5 hurricanes); the yearly variation of the mean latitude and longitude (genesis location) of all tropical cyclones and hurricanes; and the yearly variation of the mean peak wind speeds, lowest pressures, and durations for all tropical cyclones, hurricanes, and major hurricanes. Also examined is the relationship between inferred trends found in the North Atlantic basin tropical cyclonic activity and natural variability and global warming, the latter described using surface air temperatures from the Armagh Observatory Armagh, Northern Ireland. Lastly, a simple statistical technique is employed to ascertain the expected level of North Atlantic basin tropical cyclonic activity for the upcoming 2007 season.

  14. Meridional fluxes of dissolved organic matter in the North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Walsh, John J.; Carder, Kendall L.; Mueller-Karger, Frank E.

    1992-01-01

    Biooptical estimates of gelbstoff and a few platinum measurements of dissolved organic carbon (DOCpt) are used to construct a budget of the meridional flux of DOC and dissolved organic nitrogen (DON) across 36 deg 25 min N in the North Atlantic from previous inverse models of water and element transport. Distinct southward subsurface fluxes of dissolved organic matter within subducted shelf water, cabelled slope water, and overturned basin water are inferred. Within two cases of a positive gradient of DOCpt between terrestrial/shelf and offshore stocks, the net equatorward exports of O2 and DOCpt from the northern North Atlantic yield molar ratios of 2.1 to 9.1, compared to the expected Redfield O2/C ratio of 1.3. It is concluded that some shelf export of DOC, with a positive gradient between coastal and oceanic stocks, as well as falling particles, are required to balance carbon, nitrogen, and oxygen budgets of the North Atlantic.

  15. The Influence of North Atlantic Valves and Gateways on Neogene Climate Change

    NASA Astrophysics Data System (ADS)

    Wright, J. D.

    2015-12-01

    Our current proxies for pCO2 suggest Neogene levels were relatively constant (~300 ± 100 ppm) except for the middle Miocene Climatic Optimum with estimates approaching 400 ± 100 ppm. Yet, the East Antarctic Ice Sheet became a polar ice sheet and permanent feature on Earth while large-scale Northern Hemisphere ice sheets waxed and waned with scant differences in pCO2. Three possibilities to explain these observations are: 1) our pCO2 proxies are incorrect; 2) Earth's climate is far more sensitive than our current model simulations suggest; or 3) tectonic differences overprinted accepted climate sensitivity to pCO2. Two marine gateways that influenced Neogene deep-water circulation are the Greenland-Scotland Ridge and the Central American Isthmus (CAI). Driven by mantle plume variations under Iceland, the GSR acted as a regulator of Northern Component Water (NCW, analogous to NADW) by controlling access to the dense polar waters to the north. During the latest Miocene and early Pliocene, mean depths along the GSR and NCW production were at their greatest. By the late Pliocene (~3 Ma), mantle plume activity increased and NCW production waned. Most researchers have focused on surface water changes (e.g., salinity) in relating closure of the CAI to Pliocene climate change. However, I propose that its primary influence came with the elimination of low-latitude, deep-water connection between the Atlantic and Pacific. Combined with vigorous NCW production, closure of the CAI re-distributed nutrients between the oceans. Carbon isotope and Cd/Ca profiles indicate that "modern" basin-to-basin differences started during the latest Miocene and were fully developed in the Pliocene. The South Atlantic path for NCW also delivered heat to the Southern Ocean, facilitating sea ice changes, as indicated by biosiliceous patterns. These tectonic boundary changes and their affects on surface and deep water circulation contributed to the Pliocene pause in global cooling that began in

  16. Large fluctuations of dissolved oxygen in the Indian and Pacific oceans during Dansgaard-Oeschger oscillations caused by variations of North Atlantic Deep Water subduction

    USGS Publications Warehouse

    Schmittner, A.; Galbraith, E.D.; Hostetler, S.W.; Pedersen, Thomas F.; Zhang, R.

    2007-01-01

    Paleoclimate records from glacial Indian and Pacific oceans sediments document millennial-scale fluctuations of subsurface dissolved oxygen levels and denitrification coherent with North Atlantic temperature oscillations. Yet the mechanism of this teleconnection between the remote ocean basins remains elusive. Here we present model simulations of the oxygen and nitrogen cycles that explain how changes in deepwater subduction in the North Atlantic can cause large and synchronous variations of oxygen minimum zones, throughout the Northern Hemisphere of the Indian and Pacific oceans, consistent with the paleoclimate records. Cold periods in the North Atlantic are associated with reduced nutrient delivery to the upper Indo-Pacific oceans, thereby decreasing productivity. Reduced export production diminishes subsurface respiration of organic matter leading to higher oxygen concentrations and less denitrification. This effect of reduced oxygen consumption dominates at low latitudes. At high latitudes in the Southern Ocean and North Pacific, increased mixed layer depths and steepening of isopycnals improve ocean ventilation and oxygen supply to the subsurface. Atmospheric teleconnections through changes in wind-driven ocean circulation modify this basin-scale pattern regionally. These results suggest that changes in the Atlantic Ocean circulation, similar to those projected by climate models to possibly occur in the centuries to come because of anthropogenic climate warming, can have large effects on marine ecosystems and biogeochemical cycles even in remote areas. Copyright 2007 by the American Geophysical Union.

  17. Effect of abyssal circulation changes on Oligocene to Miocene benthic foraminifera in the North Atlantic

    SciTech Connect

    Katz, M.E.; Miller, K.G.

    1985-01-01

    Benthic foraminiferal ranges at western North Atlantic Sites 563 and 558 show: 1) gradual Oligocene last occurrences in response to subsidence from the upper to lower abyssal zones; 2) a preponderance of extinctions in the early middle Miocene (about 15.5-13.5 Ma). Comparison of relative and absolute abundance changes at Site 563 sows that percentages of some taxa (e.g. Nuttallides umbonifera) reliably reflect their accumulations while percentages of others vary independently. Regional abundance changes include: 1) maxima N. umbonifera in the middle Oligocene of the deepest sites (10 and 119); 2) increased Planulina wuellerstorfi in the early middle Miocene; 3) increased N. umbonifera in the late middle Miocene. Seismic stratigraphic and delta/sup 13/C evidence indicates a northern bottom-water source for the North Atlantic throughout much of the Oligocene and Miocene. Benthic foraminifera apparently responded to bottom-water changes inferred from carbon isotopic comparisons. The extinction of relict Paleogene taxa and the ascendancy of P. wuellerstorfi in the middle Miocene apparently correlate with increased advection into the eastern Atlantic, subsidence of the Iceland-Faeroe Ridge and increased North Atlantic carbonate sedimentation. The authors speculate that this faunal reorganization was in response to global ocean chemistry changes resulting from increased ventilation of the North Atlantic.

  18. Sub-decadal North Atlantic Oscillation variability in observations and the Kiel Climate Model

    NASA Astrophysics Data System (ADS)

    Reintges, Annika; Latif, Mojib; Park, Wonsun

    2016-07-01

    The North Atlantic Oscillation (NAO) is the dominant mode of winter climate variability in the North Atlantic sector. The corresponding index varies on a wide range of timescales, from days and months to decades and beyond. Sub-decadal NAO variability has been well documented, but the underlying mechanism is still under discussion. Other indices of North Atlantic sector climate variability such as indices of sea surface and surface air temperature or Arctic sea ice extent also exhibit pronounced sub-decadal variability. Here, we use sea surface temperature and sea level pressure observations, and the Kiel Climate Model to investigate the dynamics of the sub-decadal NAO variability. The sub-decadal NAO variability is suggested to originate from dynamical large-scale air-sea interactions. The adjustment of the Atlantic Meridional Overturning Circulation to previous surface heat flux variability provides the memory of the coupled mode. The results stress the role of coupled feedbacks in generating sub-decadal North Atlantic sector climate variability, which is important to multiyear climate predictability in that region.

  19. Atlantic Multidecadal Oscillation (AMO) modulates dynamics of small pelagic fishes and ecosystem regime shifts in the eastern North and Central Atlantic

    NASA Astrophysics Data System (ADS)

    Alheit, Jürgen; Licandro, Priscilla; Coombs, Steve; Garcia, Alberto; Giráldez, Ana; Santamaría, Maria Teresa Garcia; Slotte, Aril; Tsikliras, Athanassios C.

    2014-03-01

    Dynamics of abundance and migrations of populations of small pelagic clupeoid fish such as anchovy (Engraulis encrasicolus), sardine (Sardina pilchardus), sardinella (Sardinella aurita), sprat (Sprattus sprattus) and herring (Clupea harengus) in the eastern North and Central Atlantic between Senegal and Norway vary in synchrony with the warm and cool phases of the Atlantic Multidecadal Oscillation (AMO). This is shown by compiling retrospective data on fish catches and anecdotal observations, which in some cases date back to the mid-19th century. The AMO is defined as the de-trended mean of North Atlantic (0-60°N) sea surface temperature anomalies. However, it is not primarily the temperature which drives the dynamics of the small pelagic fish populations. Instead, the AMO seems to be a proxy for complex processes in the coupled atmosphere-ocean system of the North Atlantic. This is manifested in large-scale changes in strength and direction of the current system that move water masses around the North Atlantic and likely involves the North Atlantic Oscillation (NAO), the Atlantic Meridional Overturning Circulation (AMOC), the Mediterranean Overflow Water (MOW) and the subpolar gyre (SPG). The contractions and expansions of the SPG apparently play a key role. This was particularly obvious in the mid-1990s, when the SPG abruptly contracted with the result that warm subtropical water masses moved to the north and east. Small pelagic fish populations in the eastern North and Central Atlantic, including those in the Mediterranean responded quickly by changing abundances and migrating northwards. It seems that the complex ocean-atmosphere changes in the mid-1990s, which are described in the text in detail, caused a regime shift in the ecosystems of the eastern North and Central Atlantic and the small pelagic clupeoid fish populations are the sentinels of this shift.

  20. Climate variability in the North Atlantic on decadal and multi-decadal time scales: A numerical study

    NASA Astrophysics Data System (ADS)

    Cheng, Wei

    maintaining this oscillation. One is the delay of the North Atlantic overturning strength relative to the deep water formation rate in the deep water production region; the other is the delay of the associated SST and surface heat flux anomalies in the sinking region relative to the overturning amplitude itself. The sea surface temperature signal associated with the THC oscillation bears some resemblance to an SST interdecadal pattern extracted from observational data (Kushnir, 1993). Accompanying anomalies of northern hemispheric surface air temperature have positive values over the Pacific and Atlantic Oceans and negative values over the Eurasian and North American continents. In addition to anomalies in sea surface temperature and surface air temperature, there are also variations in atmospheric flow pattern over the North Atlantic, namely, an anomalous northerly flow over the Labrador Sea when the THC circulation is strong.

  1. Lithospheric models of the North American continent

    NASA Astrophysics Data System (ADS)

    Tesauro, Magdala; Kaban, Mikhail; Mooney, Walter; Cloetingh, Sierd

    2015-04-01

    We constructed NACr14, a 3D model of the North American (NA) crust, based on the most recent seismic data from the USGS database. In comparison with the global crustal model CRUST 1.0, NACr14 is more heterogeneous, showing a larger spatial variability of the thickness and average velocities of the crustal layers. Velocities of the lower crust vary in a larger range than those of the other layers, while the thickness of all the three layers is on average between 11 and 13 km. The largest velocities of the crystalline crust (>6.6 km/s) reflect the presence of a 7.x layer (>7.0 km/s) in the lowermost part of the crust. Using NACr2014, a regional (NA07) and a global (SL201sv) tomography model, and gravity data, we apply an iterative technique, which jointly interprets seismic tomography and gravity data, to estimate temperature and compositional variations in the NA upper mantle. The results obtained demonstrate that temperature of the cratonic mantle is up to 150°C higher than when using a uniform compositional model. The differences between the two tomography models influence the results more strongly than possible changes of the depth distribution of compositional variations. Strong negative compositional density anomalies, corresponding to Mg # >92, characterize the upper mantle of the northwestern part of the Superior craton and the central part of the Slave and Churchill craton. The Proterozoic upper mantle of the western and more deformed part of the NA cratons, appears weakly depleted (Mg# ~91) when NA07 is used, in agreement with the results based on the interpretation of xenolith data. When we use SL2013sv, the same areas are locally characterized by high density bodies, which might be interpreted as the effect due to fragments of subducted slabs, as those close to the suture of the Appalachians and Grenville province. We used the two thermal models to estimate the integrated strength and the effective elastic thickness (Te) of the lithosphere. In the

  2. Imported Dust in North American Skies

    NASA Video Gallery

    NASA and university scientists have made the first measurement-based estimate of the amount and composition of tiny airborne particles that arrive in the air over North America each year. With a 3D...

  3. The North Atlantic Ocean as habitat for Calanus finmarchicus: Environmental factors and life history traits

    NASA Astrophysics Data System (ADS)

    Melle, Webjørn; Runge, Jeffrey; Head, Erica; Plourde, Stéphane; Castellani, Claudia; Licandro, Priscilla; Pierson, James; Jonasdottir, Sigrun; Johnson, Catherine; Broms, Cecilie; Debes, Høgni; Falkenhaug, Tone; Gaard, Eilif; Gislason, Astthor; Heath, Michael; Niehoff, Barbara; Nielsen, Torkel Gissel; Pepin, Pierre; Stenevik, Erling Kaare; Chust, Guillem

    2014-12-01

    Here we present a new, pan-Atlantic compilation and analysis of data on Calanus finmarchicus abundance, demography, dormancy, egg production and mortality in relation to basin-scale patterns of temperature, phytoplankton biomass, circulation and other environmental characteristics in the context of understanding factors determining the distribution and abundance of C. finmarchicus across its North Atlantic habitat. A number of themes emerge: (1) the south-to-north transport of plankton in the northeast Atlantic contrasts with north-to-south transport in the western North Atlantic, which has implications for understanding population responses of C. finmarchicus to climate forcing, (2) recruitment to the youngest copepodite stages occurs during or just after the phytoplankton bloom in the east whereas it occurs after the bloom at many western sites, with up to 3.5 months difference in recruitment timing, (3) the deep basin and gyre of the southern Norwegian Sea is the centre of production and overwintering of C. finmarchicus, upon which the surrounding waters depend, whereas, in the Labrador/Irminger Seas production mainly occurs along the margins, such that the deep basins serve as collection areas and refugia for the overwintering populations, rather than as centres of production, (4) the western North Atlantic marginal seas have an important role in sustaining high C. finmarchicus abundance on the nearby coastal shelves, (5) differences in mean temperature and chlorophyll concentration between the western and eastern North Atlantic are reflected in regional differences in female body size and egg production, (6) regional differences in functional responses of egg production rate may reflect genetic differences between western and eastern populations, (7) dormancy duration is generally shorter in the deep waters adjacent to the lower latitude western North Atlantic shelves than in the east, (8) there are differences in stage-specific daily mortality rates between

  4. North Atlantic Basin Tropical Cyclone Activity in Relation to Temperature and Decadal- Length Oscillation Patterns

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    2009-01-01

    Yearly frequencies of North Atlantic basin tropical cyclones, their locations of origin, peak wind speeds, average peak wind speeds, lowest pressures, and average lowest pressures for the interval 1950-2008 are examined. The effects of El Nino and La Nina on the tropical cyclone parametric values are investigated. Yearly and 10-year moving average (10-yma) values of tropical cyclone parameters are compared against those of temperature and decadal-length oscillation, employing both linear and bi-variate analysis, and first differences in the 10-yma are determined. Discussion of the 2009 North Atlantic basin hurricane season, updating earlier results, is given.

  5. Deglacial Subsurface Temperature Change in the Tropical North Atlantic Linked to Atlantic Meridional Overturning Circulation Variability

    NASA Astrophysics Data System (ADS)

    Schmidt, M. W.; Hertzberg, J. E.; Them, T. R.; Parker, A. O.; Chang, P.

    2011-12-01

    Coupled ocean-atmosphere modeling experiments conducted under both the present and Last Glacial Maximum (LGM) conditions indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly coupled to abrupt tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes (Zhang, 2007; Chang et al., 2008; Chiang et al., 2008; Otto-Bliesner and Brady, 2009). While a slowdown of AMOC in these experiments results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger warming due to rapid reorganizations of ocean circulation patterns (Wan et al., 2009). To test the hypothesis that subsurface temperature change in the TNA is coupled to AMOC variability across abrupt climate events over the last deglacial, we reconstruct Mg/Ca-temperature and δ18O records from both surface (Globigerinoides ruber, upper mixed layer) and sub-thermocline dwelling (Globorotalia truncatulinoides, 350-500 m depth) planktonic foraminifera, as well as from the benthic species Cibicidoides pachyderma in the southern Caribbean Sea sediment core VM12-107 (11.33 °N, 66.63 °W; 1079 m; 18 cm/kyr sedimentation rate). Reconstructed sea surface temperatures (SSTs) indicate a gradual warming in the TNA starting at ~19 kyr BP with small cold reversals of ~1.5 °C during Heinrich Event 1 (H1) and the Younger Dryas (YD). In contrast, LGM subsurface temperatures were as much as 2.5 °C warmer than Late Holocene values and H1 and the YD are marked by the warmest subsurface temperatures characterized by abrupt temperature increases as large as 4-5 °C. In addition, benthic Mg/Ca ratios during the YD and H1 increase by 50% relative to Holocene intervals, suggesting significant warming extending to 1079 m water depth across these events. Comparison of our subsurface temperature records with the Bermuda Rise 231Pa/230Th proxy record of AMOC variability (McManus et al., 2004) indicates a strong correlation between

  6. Fifty-seventh supplement to the American Ornithologists' Union Check-list of North American Birds

    USGS Publications Warehouse

    Chesser, R. Terry; Burns, Kevin J; Cicero, Carla; Dunn, Jon L.; Kratter, Andrew W.; Lovette, Irby J.; Rasmussen, Pamela C.; Remsen, J.V.; Rising, James D.; Stotz, Douglas F.; Winker, Kevin

    2016-01-01

    This is the 16th supplement since publication of the 7th edition of the Check-list of North American Birds (American Ornithologists' Union [AOU] 1998). It summarizes decisions made between April 15, 2015, and April 15, 2016, by the AOU's Committee on Classification and Nomenclature—North and Middle America. The Committee has continued to operate in the manner outlined in the 42nd Supplement (AOU 2000).

  7. 75 FR 57407 - Atlantic Highly Migratory Species; North and South Atlantic Swordfish Quotas

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-21

    ... fishing for swordfish in the Atlantic Ocean, including the Caribbean Sea and Gulf of Mexico, by... specific measures laid out in the proposed rule can be found in 75 FR 35432 (June 22, 2010) and are...

  8. Extinction rates in North American freshwater fishes, 1900-2010

    USGS Publications Warehouse

    Burkhead, Noel M.

    2012-01-01

    Widespread evidence shows that the modern rates of extinction in many plants and animals exceed background rates in the fossil record. In the present article, I investigate this issue with regard to North American freshwater fishes. From 1898 to 2006, 57 taxa became extinct, and three distinct populations were extirpated from the continent. Since 1989, the numbers of extinct North American fishes have increased by 25%. From the end of the nineteenth century to the present, modern extinctions varied by decade but significantly increased after 1950 (post-1950s mean = 7.5 extinct taxa per decade). In the twentieth century, freshwater fishes had the highest extinction rate worldwide among vertebrates. The modern extinction rate for North American freshwater fishes is conservatively estimated to be 877 times greater than the background extinction rate for freshwater fishes (one extinction every 3 million years). Reasonable estimates project that future increases in extinctions will range from 53 to 86 species by 2050.

  9. Extinction rates in North American freshwater fishes, 1900-2010

    USGS Publications Warehouse

    Burkhead, Noel M.

    2012-01-01

    Widespread evidence shows that the modern rates of extinction in many plants and animals exceed background rates in the fossil record. In the present article, I investigate this issue with regard to North American freshwater fishes. From 1898 to 2006, 57 taxa became extinct, and three distinct populations were extirpated from the continent. Since 1989, the numbers of extinct North American fishes have increased by 25%. From the end of the nineteenth century to the present, modern extinctions varied by decade but significantly increased after 1950 (post-1950s mean = 7.5 extinct taxa per decade). The modern extinction rate for North American freshwater fishes is conservatively estimated to be 877 times greater than the background extinction rate for freshwater fishes (one extinction every 3 million years). Reasonable estimates project that future increases in extinctions will range from 53 to 86 species by 2050.

  10. Elemental ratios and enrichment factors in aerosols from the US-GEOTRACES North Atlantic transects

    NASA Astrophysics Data System (ADS)

    Shelley, Rachel U.; Morton, Peter L.; Landing, William M.

    2015-06-01

    The North Atlantic receives the highest aerosol (dust) input of all the oceanic basins. Dust deposition provides essential bioactive elements, as well as pollution-derived elements, to the surface ocean. The arid regions of North Africa are the predominant source of dust to the North Atlantic Ocean. In this study, we describe the elemental composition (Li, Na, Mg, Al, P, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Cd, Sn, Sb, Cs, Ba, La, Ce, Nd, Pb, Th, U) of the bulk aerosol from samples collected during the US-GEOTRACES North Atlantic Zonal Transect (2010/11) in order to highlight the differences between a Saharan dust end-member and the reported elemental composition of the upper continental crust (UCC), and the implications this has for identifying trace element enrichment in aerosols across the North Atlantic basin. As aerosol titanium (Ti) is less soluble than aerosol aluminum (Al), it is a more conservative tracer for lithogenic aerosols and trace element-to-Ti ratios. However, the presence of Ti-rich fine aerosols can confound the interpretation of elemental enrichments, making Al a more robust tracer of aerosol lithogenic material in this region.

  11. Volcanic forcing of the North Atlantic Oscillation over the last 2,000 years

    NASA Astrophysics Data System (ADS)

    Breitenbach, Sebastian F. M.; Ridley, Harriet E.; Lechleitner, Franziska A.; Asmerom, Yemane; Rehfeld, Kira; Prufer, Keith M.; Kennett, Douglas J.; Aquino, Valorie V.; Polyak, Victor; Goswami, Bedartha; Marwan, Norbert; Haug, Gerald H.; Baldini, James U. L.

    2015-04-01

    The North Atlantic Oscillation (NAO) is a principal mode of atmospheric circulation in the North Atlantic realm (Hurrell et al. 2003) and influences rainfall distribution over Europe, North Africa and North America. Although observational data inform us on multi-annual variability of the NAO, long and detailed paleoclimate datasets are required to understand the mechanisms and full range of its variability and the spatial extent of its influence. Chronologies of available proxy-based NAO reconstructions are often interdependent and cover only the last ~1,100 years, while longer records are characterized by low sampling resolution and chronological constraints. This complicates the reconstruction of regional responses to NAO changes. We present data from a 2,000 year long sub-annual carbon isotope record from speleothem YOK-I from Yok Balum Cave, Belize, Central America. YOK-I has been extensively dated using U-series (Kennett et al. 2012). Monitoring shows that stalagmite δ13C in Yok Balum cave is governed by infiltration changes associated with tropical wet season rainfall. Higher (lower) δ13C values reflect drier (wetter) conditions related to Intertropical Convergence Zone position and trade winds intensity. Comparison with NAO reconstructions (Proctor et al. 2000, Trouet et al. 2009, Wassenburg et al. 2013) reveals that YOK-I δ13C sensitively records NAO-related rainfall dynamics over Belize. The Median Absolute Deviation (MAD) of δ13C extends NAO reconstructions to the last 2,000 years and indicates that high latitude volcanic aerosols force negative NAO phases. We infer that volcanic aerosols modify inter-hemispheric temperature contrasts at multi-annual scale, resulting in meridional relocation of the ITCZ and the Bermuda-Azores High, altering NAO and tropical rainfall patterns. Decade-long dry periods in the 11th and the late 18th century relate to major high northern latitude eruptions and exemplify the climatic response to volcanic forcing by

  12. Latest Quaternary palaeoceanographic change in the eastern North Atlantic based upon a dinoflagellate cyst event ecostratigraphy.

    PubMed

    Harland, Rex; Polovodova Asteman, Irina; Morley, Audrey; Morris, Angela; Harris, Anthony; Howe, John A

    2016-05-01

    The analyses of dinoflagellate cyst records, from the latest Quaternary sediments recovered from DSDP Core 610A taken on the Feni Ridge in the southern Rockall Trough, and part of core MD01-2461 on the continental margin of the Porcupine Seabight in the eastern North Atlantic Ocean, has provided evidence for significant oceanographic change encompassing the Last Glacial Maximum (LGM) and part of the Holocene. This together with other published records has led to a regional evaluation of oceanographic change in the eastern North Atlantic over the past 68 ka, based upon a distinctive dinoflagellate event ecostratigraphy. These changes reflect changes in the surface waters of the North Atlantic Current (NAC), and perhaps the deeper thermohaline Atlantic Meridional Overturning Circulation (AMOC), driving fundamental regime changes within the phytoplanktonic communities. Three distinctive dinoflagellate cyst associations based upon both factor and cluster analyses have been recognised. Associations characterised by Bitectatodinium tepikiense (between 61.1 ± 6.2 to 13.4 ± 1.1 ka BP), Nematosphaeropsis labyrinthus (between 10.5 ± 0.3 and 11.45 ± 0.8 ka. BP), and the cyst of Protoceratium reticulatum (between 8.5 ± 0.9 and 5.2 ± 1.3 ka. BP) indicate major change within the eastern North Atlantic oceanography. The transitions between these changes occur over a relatively short time span (c.1.5 ka), given our sampling resolution, and have the potential to be incorporated into an event stratigraphy through the latest Quaternary as recommended by the INTIMATE (INTegrating Ice core, MArine and TErrestrial records) group. The inclusion of a dinoflagellate cyst event stratigraphy would highlight changes within the phytoplankton of the North Atlantic Ocean as a fully glacial world changed to our present interglacial.

  13. Latest Quaternary palaeoceanographic change in the eastern North Atlantic based upon a dinoflagellate cyst event ecostratigraphy.

    PubMed

    Harland, Rex; Polovodova Asteman, Irina; Morley, Audrey; Morris, Angela; Harris, Anthony; Howe, John A

    2016-05-01

    The analyses of dinoflagellate cyst records, from the latest Quaternary sediments recovered from DSDP Core 610A taken on the Feni Ridge in the southern Rockall Trough, and part of core MD01-2461 on the continental margin of the Porcupine Seabight in the eastern North Atlantic Ocean, has provided evidence for significant oceanographic change encompassing the Last Glacial Maximum (LGM) and part of the Holocene. This together with other published records has led to a regional evaluation of oceanographic change in the eastern North Atlantic over the past 68 ka, based upon a distinctive dinoflagellate event ecostratigraphy. These changes reflect changes in the surface waters of the North Atlantic Current (NAC), and perhaps the deeper thermohaline Atlantic Meridional Overturning Circulation (AMOC), driving fundamental regime changes within the phytoplanktonic communities. Three distinctive dinoflagellate cyst associations based upon both factor and cluster analyses have been recognised. Associations characterised by Bitectatodinium tepikiense (between 61.1 ± 6.2 to 13.4 ± 1.1 ka BP), Nematosphaeropsis labyrinthus (between 10.5 ± 0.3 and 11.45 ± 0.8 ka. BP), and the cyst of Protoceratium reticulatum (between 8.5 ± 0.9 and 5.2 ± 1.3 ka. BP) indicate major change within the eastern North Atlantic oceanography. The transitions between these changes occur over a relatively short time span (c.1.5 ka), given our sampling resolution, and have the potential to be incorporated into an event stratigraphy through the latest Quaternary as recommended by the INTIMATE (INTegrating Ice core, MArine and TErrestrial records) group. The inclusion of a dinoflagellate cyst event stratigraphy would highlight changes within the phytoplankton of the North Atlantic Ocean as a fully glacial world changed to our present interglacial. PMID:27441285

  14. Longevity records of North American birds: Coerebinae through Estrildidae

    USGS Publications Warehouse

    Klimkiewicz, M.K.; Futcher, A.G.

    1987-01-01

    This is the fourth paper of a 4-part series detailing the longevity records of marked North American birds. The previous three papers can be found in the Journal of Field Ornithology, Volumes 53 and 54. Prio to this series only one definitive paper ( Kennard 1975) had been written on North American taxa. Records for 84 taxa are included in this paper. Thirty are birds older than those listed by Kennard. Thirty-nine are new records and 9 are those listed in Kennard.

  15. Origin and evolution of North American polyploid Silene (Caryophyllaceae).

    PubMed

    Popp, Magnus; Oxelman, Bengt

    2007-03-01

    Nuclear DNA sequences from introns of the low-copy nuclear gene family encoding the second largest subunit of RNA polymerases and the ribosomal internal transcribed spacer (ITS) regions, combined with the psbE-petL spacer and the rps16 intron from the chloroplast genome were used to infer origins and phylogenetic relationships of North American polyploid Silene species and their closest relatives. Although the vast majority of North American Silene species are polyploid, which contrasts to the diploid condition dominating in other parts of the world, the phylogenetic analyses rejected a single origin of the North American polyploids. One lineage consists of tetraploid Silene menziesii and its diploid allies. A second lineage, Physolychnis s.l., consists of Arctic, European, Asian, and South American taxa in addition to the majority of the North American polyploids. The hexaploid S. hookeri is derived from an allopolyploidization between these two lineages. The tetraploid S. nivea does not belong to any of these lineages, but is closely related to the European diploid S. baccifera. The poor resolution within Physolychnis s.l. may be attributed to rapid radiation, recombination among homoeologues, homoplasy, or any combination of these factors. No extant diploid donors could be identified in Physolychnis s.l. PMID:21636405

  16. Sea Ice and Hydrographic Variability in the Northwest North Atlantic

    NASA Astrophysics Data System (ADS)

    Fenty, I. G.; Heimbach, P.; Wunsch, C. I.

    2010-12-01

    Sea ice anomalies in the Northwest North Atlantic's Labrador Sea are of climatic interest because of known and hypothesized feedbacks with hydrographic anomalies, deep convection/mode water formation, and Northern Hemisphere atmospheric patterns. As greenhouse gas concentrations increase, hydrographic anomalies formed in the Arctic Ocean associated with warming will propagate into the Labrador Sea via the Fram Strait/West Greenland Current and the Canadian Archipelago/Baffin Island Current. Therefore, understanding the dynamical response of sea ice in the basin to hydrographic anomalies is essential for the prediction and interpretation of future high-latitude climate change. Historically, efforts to quantify the link between the observed sea ice and hydrographic variability in the region has been limited due to in situ observation paucity and technical challenges associated with synthesizing ocean and sea ice observations with numerical models. To elaborate the relationship between sea ice and ocean variability, we create three one-year (1992-1993, 1996-1997, 2003-2004) three-dimensional time-varying reconstructions of the ocean and sea ice state in Labrador Sea and Baffin Bay. The reconstructions are syntheses of a regional coupled 32 km ocean-sea ice model with a suite of contemporary in situ and satellite hydrographic and ice data using the adjoint method. The model and data are made consistent, in a least-squares sense, by iteratively adjusting several model control variables (e.g., ocean initial and lateral boundary conditions and the atmospheric state) to minimize an uncertainty-weighted model-data misfit cost function. The reconstructions reveal that the ice pack attains a state of quasi-equilibrium in mid-March (the annual sea ice maximum) in which the total ice-covered area reaches a steady state -ice production and dynamical divergence along the coasts balances dynamical convergence and melt along the pack’s seaward edge. Sea ice advected to the

  17. North American drought: Reconstructions, causes, and consequences

    NASA Astrophysics Data System (ADS)

    Cook, Edward R.; Seager, Richard; Cane, Mark A.; Stahle, David W.

    2007-03-01

    Severe drought is the greatest recurring natural disaster to strike North America. A remarkable network of centuries-long annual tree-ring chronologies has now allowed for the reconstruction of past drought over North America covering the past 1000 or more years in most regions. These reconstructions reveal the occurrence of past "megadroughts" of unprecedented severity and duration, ones that have never been experienced by modern societies in North America. There is strong archaeological evidence for the destabilizing influence of these past droughts on advanced agricultural societies, examples that should resonate today given the increasing vulnerability of modern water-based systems to relatively short-term droughts. Understanding how these megadroughts develop and persist is a timely scientific problem. Very recently, climate models have succeeded in simulating all of the major droughts over North America from the Civil War to the severe 1998-2004 drought in the western U.S. These numerical experiments indicate the dominating importance of tropical Pacific Ocean sea surface temperatures (SSTs) in determining how much precipitation falls over large parts of North America. Of central importance to drought formation is the development of cool "La Niña-like" SSTs in the eastern tropical Pacific region. This development appears to be partially linked to changes in radiative forcing over that region, which affects the Bjerknes feedback mechanism of the ENSO cycle there. Paradoxically, warmer conditions over the tropical Pacific region lead to the development of cool La Niña-like SSTs there, which is drought inducing over North America. Whether or not this process will lead to a greater prevalence of drought in the future as the world warms due to accumulating greenhouse gases is unclear at this time.

  18. North American snake envenomation in the dog and cat.

    PubMed

    Gilliam, Lyndi L; Brunker, Jill

    2011-11-01

    Snake envenomation can be a cause of significant morbidity in dogs and cats in North America. Being familiar with the venomous snakes in your area and understanding the mechanisms of action of their venom will allow for successful treatment of envenomation cases. Treatment of snake envenomation revolves around supportive care in mild to moderate cases and venom neutralization with antivenom in severe cases. Dogs and cats envenomated by North American snakes have a good prognosis if treated appropriately.

  19. The Continental Margins of the Western North Atlantic.

    ERIC Educational Resources Information Center

    Schlee, John S.; And Others

    1979-01-01

    Presents an interpretation of geological and geophysical data, which provides a summary of the structural and sedimentary history of the United States Atlantic Margin. The importance of an understanding of the development of the outer continental shelf to future hydrocarbon exploration is detailed. (BT)

  20. Hydrological change in Southern Europe responding to increasing North Atlantic overturning during Greenland Stadial 1

    PubMed Central

    Bartolomé, Miguel; Moreno, Ana; Sancho, Carlos; Stoll, Heather M.; Cacho, Isabel; Spötl, Christoph; Belmonte, Ánchel; Edwards, R. Lawrence; Cheng, Hai; Hellstrom, John C.

    2015-01-01

    Greenland Stadial 1 (GS-1) was the last of a long series of severe cooling episodes in the Northern Hemisphere during the last glacial period. Numerous North Atlantic and European records reveal the intense environmental impact of that stadial, whose origin is attributed to an intense weakening of the Atlantic Meridional Overturning Circulation in response to freshening of the North Atlantic. Recent high-resolution studies of European lakes revealed a mid–GS-1 transition in the climatic regimes. The geographical extension of such atmospheric changes and their potential coupling with ocean dynamics still remains unclear. Here we use a subdecadally resolved stalagmite record from the Northern Iberian Peninsula to further investigate the timing and forcing of this transition. A solid interpretation of the environmental changes detected in this new, accurately dated, stalagmite record is based on a parallel cave monitoring exercise. This record reveals a gradual transition from dry to wet conditions starting at 12,500 y before 2000 A.D. in parallel to a progressive warming of the subtropical Atlantic Ocean. The observed atmospheric changes are proposed to be led by a progressive resumption of the North Atlantic convection and highlight the complex regional signature of GS-1, very distinctive from previous stadial events. PMID:25964366

  1. Hydrological change in Southern Europe responding to increasing North Atlantic overturning during Greenland Stadial 1.

    PubMed

    Bartolomé, Miguel; Moreno, Ana; Sancho, Carlos; Stoll, Heather M; Cacho, Isabel; Spötl, Christoph; Belmonte, Ánchel; Edwards, R Lawrence; Cheng, Hai; Hellstrom, John C

    2015-05-26

    Greenland Stadial 1 (GS-1) was the last of a long series of severe cooling episodes in the Northern Hemisphere during the last glacial period. Numerous North Atlantic and European records reveal the intense environmental impact of that stadial, whose origin is attributed to an intense weakening of the Atlantic Meridional Overturning Circulation in response to freshening of the North Atlantic. Recent high-resolution studies of European lakes revealed a mid-GS-1 transition in the climatic regimes. The geographical extension of such atmospheric changes and their potential coupling with ocean dynamics still remains unclear. Here we use a subdecadally resolved stalagmite record from the Northern Iberian Peninsula to further investigate the timing and forcing of this transition. A solid interpretation of the environmental changes detected in this new, accurately dated, stalagmite record is based on a parallel cave monitoring exercise. This record reveals a gradual transition from dry to wet conditions starting at 12,500 y before 2000 A.D. in parallel to a progressive warming of the subtropical Atlantic Ocean. The observed atmospheric changes are proposed to be led by a progressive resumption of the North Atlantic convection and highlight the complex regional signature of GS-1, very distinctive from previous stadial events. PMID:25964366

  2. Dynamics of Mid-Palaeocene North Atlantic rifting linked with European intra-plate deformations.

    PubMed

    Nielsen, Søren B; Stephenson, Randell; Thomsen, Erik

    2007-12-13

    The process of continental break-up provides a large-scale experiment that can be used to test causal relations between plate tectonics and the dynamics of the Earth's deep mantle. Detailed diagnostic information on the timing and dynamics of such events, which are not resolved by plate kinematic reconstructions, can be obtained from the response of the interior of adjacent continental plates to stress changes generated by plate boundary processes. Here we demonstrate a causal relationship between North Atlantic continental rifting at approximately 62 Myr ago and an abrupt change of the intra-plate deformation style in the adjacent European continent. The rifting involved a left-lateral displacement between the North American-Greenland plate and Eurasia, which initiated the observed pause in the relative convergence of Europe and Africa. The associated stress change in the European continent was significant and explains the sudden termination of a approximately 20-Myr-long contractional intra-plate deformation within Europe, during the late Cretaceous period to the earliest Palaeocene epoch, which was replaced by low-amplitude intra-plate stress-relaxation features. The pre-rupture tectonic stress was large enough to have been responsible for precipitating continental break-up, so there is no need to invoke a thermal mantle plume as a driving mechanism. The model explains the simultaneous timing of several diverse geological events, and shows how the intra-continental stratigraphic record can reveal the timing and dynamics of stress changes, which cannot be resolved by reconstructions based only on plate kinematics. PMID:18075591

  3. Transport and outflow to the North Atlantic in the lower marine troposphere during ICARTT 2004

    NASA Astrophysics Data System (ADS)

    Davis, S. R.; Talbot, R.; Mao, H.

    2012-01-01

    An analysis of pollution plumes emitted from sources in the Northeastern US was based on observations from the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) 2004 field campaign. Particular attention was given to the relation of these plumes to coastal transport patterns in lower tropospheric layers throughout the Gulf of Maine (GOM) and their contribution to large-scale pollution outflow from the North American continent. Using measurements obtained during a series of flights of the NOAA WP-3D and the NASA DC-8, a unique quasi-lagrangian case study was conducted for a freshly emitted plume emanating from the New York City source region in late July 2004. The initial development of this plume stemmed from the accumulation of boundary layer pollutants within a coastal residual layer where weak synoptic forcing triggered its advection by mean southwesterly flow. As the plume tracked into the GOM, analysis showed that the plume layer vertical structure evolved into an internal boundary layer form, with signatures of steep vertical gradients in temperature, moisture and wind speed often resulting in periodic turbulence. This structure remained well-defined during the plume study, allowing for the detachment of the plume layer from the surface and thus minimal deposition and plume-sea surface exchange. In contrast, lateral mixing with other low-level plumes was significant during its transit and facilitated in part by persistent shear driven turbulence which further contributed to the high spatial variability in trace gas mixing ratios. The impact of the plume inland was assessed using observations from the AIRMAP air quality network. This impact was noticeably detected as a contribution to poor surface ozone conditions and significant elevations of other major pollutants to levels equaling the highest observed that summer. Further contributions to larger-scale outflow across the North Atlantic was also observed and analyzed.

  4. Lagrangian analysis of low altitude anthropogenic plume processing across the North Atlantic

    NASA Astrophysics Data System (ADS)

    Real, E.; Law, K. S.; Schlager, H.; Roiger, A.; Huntrieser, H.; Methven, J.; Cain, M.; Holloway, J.; Neuman, J. A.; Ryerson, T.; Flocke, F.; de Gouw, J.; Atlas, E.; Donnelly, S.; Parrish, D.

    2008-12-01

    The photochemical evolution of an anthropogenic plume from the New-York/Boston region during its transport at low altitudes over the North Atlantic to the European west coast has been studied using a Lagrangian framework. This plume, originally strongly polluted, was sampled by research aircraft just off the North American east coast on 3 successive days, and then 3 days downwind off the west coast of Ireland where another aircraft re-sampled a weakly polluted plume. Changes in trace gas concentrations during transport are reproduced using a photochemical trajectory model including deposition and mixing effects. Chemical and wet deposition processing dominated the evolution of all pollutants in the plume. The mean net photochemical O3 production is estimated to be -5 ppbv/day leading to low O3 by the time the plume reached Europe. Model runs with no wet deposition of HNO3 predicted much lower average net destruction of -1 ppbv/day O3, arising from increased levels of NOx via photolysis of HNO3. This indicates that wet deposition of HNO3 is indirectly responsible for 80% of the net destruction of ozone during plume transport. If the plume had not encountered precipitation, it would have reached Europe with O3 concentrations of up to 80 to 90 ppbv and CO between 120 and 140 ppbv. Photochemical destruction also played a more important role than mixing in the evolution of plume CO due to high levels of O3 and water vapour showing that CO cannot always be used as a tracer for polluted air masses, especially in plumes transported at low altitudes. The results also show that, in this case, an increase in O3/CO slopes can be attributed to photochemical destruction of CO and not to photochemical O3 production as is often assumed.

  5. Lagrangian analysis of low level anthropogenic plume processing across the North Atlantic

    NASA Astrophysics Data System (ADS)

    Real, E.; Law, K.; Schlager, H.; Roiger, A.; Huntrieser, H.; Methven, J.; Cain, M.; Holloway, J.; Neuman, J. A.; Ryerson, T.; Flocke, F.; de Gouw, J.; Atlas, E.; Donnelly, S.; Parrish, D.

    2008-04-01

    The photochemical evolution of an anthropogenic plume from the New-York/Boston region during its transport at low altitudes over the North Atlantic to the European west coast has been studied using a Lagrangian framework. This plume, originally strongly polluted, was sampled by research aircraft just off the North American east coast on 3 successive days, and 3 days downwind off the west coast of Ireland where another aircraft re-sampled a weakly polluted plume. Changes in trace gas concentrations during transport were reproduced using a photochemical trajectory model including deposition and mixing effects. Chemical and wet deposition processing dominated the evolution of all pollutants in the plume. The mean net O3 production was evaluated to be -5 ppbv/day leading to low values of O3 by the time the plume reached Europe. Wet deposition of nitric acid was responsible for an 80% reduction in this O3 production. If the plume had not encountered precipitation, it would have reached the Europe with O3 levels up to 80-90 ppbv, and CO levels between 120 and 140 ppbv. Photochemical destruction also played a more important role than mixing in the evolution of plume CO due to high levels of both O3 and water vapour showing that CO cannot always be used as a tracer for polluted air masses, especially for plumes transported at low altitudes. The results also show that, in this case, an important increase in the O3/CO slope can be attributed to chemical destruction of CO and not to photochemical O3 production as is often assumed.

  6. Dynamics of Mid-Palaeocene North Atlantic rifting linked with European intra-plate deformations.

    PubMed

    Nielsen, Søren B; Stephenson, Randell; Thomsen, Erik

    2007-12-13

    The process of continental break-up provides a large-scale experiment that can be used to test causal relations between plate tectonics and the dynamics of the Earth's deep mantle. Detailed diagnostic information on the timing and dynamics of such events, which are not resolved by plate kinematic reconstructions, can be obtained from the response of the interior of adjacent continental plates to stress changes generated by plate boundary processes. Here we demonstrate a causal relationship between North Atlantic continental rifting at approximately 62 Myr ago and an abrupt change of the intra-plate deformation style in the adjacent European continent. The rifting involved a left-lateral displacement between the North American-Greenland plate and Eurasia, which initiated the observed pause in the relative convergence of Europe and Africa. The associated stress change in the European continent was significant and explains the sudden termination of a approximately 20-Myr-long contractional intra-plate deformation within Europe, during the late Cretaceous period to the earliest Palaeocene epoch, which was replaced by low-amplitude intra-plate stress-relaxation features. The pre-rupture tectonic stress was large enough to have been responsible for precipitating continental break-up, so there is no need to invoke a thermal mantle plume as a driving mechanism. The model explains the simultaneous timing of several diverse geological events, and shows how the intra-continental stratigraphic record can reveal the timing and dynamics of stress changes, which cannot be resolved by reconstructions based only on plate kinematics.

  7. Sports or Athletics: A North American Dilemma.

    ERIC Educational Resources Information Center

    Murray, J. Alex, Ed.

    This book reports on the 15th Annual Canadian American Seminar, the purpose of which was to explore the widening gulf between sports and athletics, and to examine and predict trends in the U.S. and Canada. The seminar presentations are divided into six sessions, plus the Frank Boland Memorial Lecture delivered by Jesse Owens. Each session includes…

  8. The Political Economy of North American Indians.

    ERIC Educational Resources Information Center

    Moore, John H., Ed.

    This book presents 12 papers that proceed from the idea that Native American history in the United States and Canada is best understood not as an Indian-European cultural conflict but as an economic conflict between communal and capitalist modes of production. Three chapters are of particular educational interest. "Political Economy in…

  9. Gases and Aerosols over North America and the Atlantic: First results from INTEX-A

    NASA Technical Reports Server (NTRS)

    Singh, Hanwant B.

    2005-01-01

    Intercontinental Chemical Transport Experiment (INTEX; http://cloud1.arc.nasa.gov) is an ongoing two-phase integrated atmospheric field experiment being performed over North America (NA). Its first phase (INTEX-A) was performed in the summer of 2004 and the second phase (INTEX-B) is planned for the early spring of 2006. The main goal is to characterize the sources and distribution of gases and aerosols over NA and to understand their transport and transformation on transcontinental/intercontinental scales in order to assess their impact on air quality and climate. Central to achieving this goal is the need to relate space-based observations with those from airborne and surface platforms. During JNTEX-A, NASA s DC-8 was joined by some dozen other aircraft from a large number of European (U. K., France, and Germany) and North American partners to explore the composition of the troposphere over NA and the Atlantic in a coordinated manner. Global and regional models along with satellite observations were extensively used to plan, coordinate, and implement this field mission. Aircraft were instrumented to measure a comprehensive suite of gases and aerosols utilizing in-situ and remote sensors. The NASA DC-8 alone was equipped with some 20 instruments capable of measuring species at concentrations as low as 10(exp -15) v/v. Measurements included major atmospheric gaseous constituents (O3, NO(x), HNO3, HNO4, PANS, SO2, VOC/OVOC, CO, and CO2), free radicals and precursors (OH, HO2, H2O2, HCHO), aerosols and radiation (microphysics, composition, optical depth, radiative flux), as well as multiple tracers of pollution. Validation of instruments aboard Terra, Aqua, and Envisat satellites was given high priority. Some of the highest pollution levels were present in the upper troposphere due to widespread deep convection. Although unexpected, frequent instances of Asian pollution over NA were encountered during these summer months. The soil uptake of CO2 over NA was

  10. The Influence of the North Atlantic Oscillation on Tropospheric Distributions of Ozone and Carbon Monoxide.

    NASA Astrophysics Data System (ADS)

    Knowland, K. E.; Doherty, R. M.; Hodges, K.

    2015-12-01

    The influence of the North Atlantic Oscillation (NAO) on the tropospheric distributions of ozone (O3) and carbon monoxide (CO) has been quantified. The Monitoring Atmospheric Composition and Climate (MACC) Reanalysis, a combined meteorology and composition dataset for the period 2003-2012 (Innes et al., 2013), is used to investigate the composition of the troposphere and lower stratosphere in relation to the location of the storm track as well as other meteorological parameters over the North Atlantic associated with the different NAO phases. Cyclone tracks in the MACC Reanalysis compare well to the cyclone tracks in the widely-used ERA-Interim Reanalysis for the same 10-year period (cyclone tracking performed using the tracking algorithm of Hodges (1995, 1999)), as both are based on the European Centre for Medium-Range Weather Forecasts' (ECMWF) Integrated Forecast System (IFS). A seasonal analysis is performed whereby the MACC reanalysis meteorological fields, O3 and CO mixing ratios are weighted by the monthly NAO index values. The location of the main storm track, which tilts towards high latitudes (toward the Arctic) during positive NAO phases to a more zonal location in the mid-latitudes (toward Europe) during negative NAO phases, impacts the location of both horizontal and vertical transport across the North Atlantic and into the Arctic. During positive NAO seasons, the persistence of cyclones over the North Atlantic coupled with a stronger Azores High promotes strong horizontal transport across the North Atlantic throughout the troposphere. In all seasons, significantly more intense cyclones occur at higher latitudes (north of ~50°C) during the positive phase of the NAO and in the southern mid-latitudes during the negative NAO phase. This impacts the location of stratospheric intrusions within the descending dry airstream behind the associated cold front of the extratropical cyclone and the venting of low-level pollution up into the free troposphere within

  11. A spatially explicit estimate of the prewhaling abundance of the endangered North Atlantic right whale.

    PubMed

    Monsarrat, Sophie; Pennino, M Grazia; Smith, Tim D; Reeves, Randall R; Meynard, Christine N; Kaplan, David M; Rodrigues, Ana S L

    2016-08-01

    The North Atlantic right whale (NARW) (Eubalaena glacialis) is one of the world's most threatened whales. It came close to extinction after nearly a millennium of exploitation and currently persists as a population of only approximately 500 individuals. Setting appropriate conservation targets for this species requires an understanding of its historical population size, as a baseline for measuring levels of depletion and progress toward recovery. This is made difficult by the scarcity of records over this species' long whaling history. We sought to estimate the preexploitation population size of the North Atlantic right whale and understand how this species was distributed across its range. We used a spatially explicit data set on historical catches of North Pacific right whales (NPRWs) (Eubalaena japonica) to model the relationship between right whale relative density and the environment during the summer feeding season. Assuming the 2 right whale species select similar environments, we projected this model to the North Atlantic to predict how the relative abundance of NARWs varied across their range. We calibrated these relative abundances with estimates of the NPRW total prewhaling population size to obtain high and low estimates for the overall NARW population size prior to exploitation. The model predicted 9,075-21,328 right whales in the North Atlantic. The current NARW population is thus <6% of the historical North Atlantic carrying capacity and has enormous potential for recovery. According to the model, in June-September NARWs concentrated in 2 main feeding areas: east of the Grand Banks of Newfoundland and in the Norwegian Sea. These 2 areas may become important in the future as feeding grounds and may already be used more regularly by this endangered species than is thought. PMID:26632250

  12. A spatially explicit estimate of the prewhaling abundance of the endangered North Atlantic right whale.

    PubMed

    Monsarrat, Sophie; Pennino, M Grazia; Smith, Tim D; Reeves, Randall R; Meynard, Christine N; Kaplan, David M; Rodrigues, Ana S L

    2016-08-01

    The North Atlantic right whale (NARW) (Eubalaena glacialis) is one of the world's most threatened whales. It came close to extinction after nearly a millennium of exploitation and currently persists as a population of only approximately 500 individuals. Setting appropriate conservation targets for this species requires an understanding of its historical population size, as a baseline for measuring levels of depletion and progress toward recovery. This is made difficult by the scarcity of records over this species' long whaling history. We sought to estimate the preexploitation population size of the North Atlantic right whale and understand how this species was distributed across its range. We used a spatially explicit data set on historical catches of North Pacific right whales (NPRWs) (Eubalaena japonica) to model the relationship between right whale relative density and the environment during the summer feeding season. Assuming the 2 right whale species select similar environments, we projected this model to the North Atlantic to predict how the relative abundance of NARWs varied across their range. We calibrated these relative abundances with estimates of the NPRW total prewhaling population size to obtain high and low estimates for the overall NARW population size prior to exploitation. The model predicted 9,075-21,328 right whales in the North Atlantic. The current NARW population is thus <6% of the historical North Atlantic carrying capacity and has enormous potential for recovery. According to the model, in June-September NARWs concentrated in 2 main feeding areas: east of the Grand Banks of Newfoundland and in the Norwegian Sea. These 2 areas may become important in the future as feeding grounds and may already be used more regularly by this endangered species than is thought.

  13. Modeling ozone plumes observed downwind of New York City over the North Atlantic Ocean during the ICARTT field campaign

    NASA Astrophysics Data System (ADS)

    Lee, S.-H.; Kim, S.-W.; Trainer, M.; Frost, G. J.; McKeen, S. A.; Cooper, O. R.; Flocke, F.; Holloway, J. S.; Neuman, J. A.; Ryerson, T.; Senff, C. J.; Swanson, A. L.; Thompson, A. M.

    2011-07-01

    photochemically fresh and aged NYC plumes, implying the possibility of long-range transport of O3 over the stable MBL over the North Atlantic Ocean in association with NOx regeneration mechanism. The impact of chemical initial and boundary conditions (IC/BCs) on modelled O3 urban plumes was investigated in terms of the background O3 level and the vertical structure of the urban plumes. Simulations with dynamic ("time-variant") chemical IC/BCs enhanced the O3 level by 2-12 ppbv on average in the atmospheric layer below 3 km, showing better agreement with the observed NYC plumes and biomass-burning plumes than the simulation with prescribed static IC/BCs. The simulation including MOZART-4 chemical IC/BCs and Alaskan/Canadian wildfire emissions compared better to the observed O3 profiles in the upper atmospheric layer (>~3 km) than models that only accounted for North American anthropogenic/biogenic and wildfire contributions to background ozone. The comparison between models and observations show that chemical IC/BCs must be properly specified to achieve accurate model results.

  14. Modeling ozone plumes observed downwind of New York City over the North Atlantic Ocean during the ICARTT field campaign

    NASA Astrophysics Data System (ADS)

    Lee, S.-H.; Kim, S.-W.; Trainer, M.; Frost, G. J.; McKeen, S. A.; Cooper, O. R.; Flocke, F.; Holloway, J. S.; Neuman, J. A.; Ryerson, T.; Senff, C. J.; Swanson, A. L.; Thompson, A. M.

    2011-05-01

    photochemically fresh and aged NYC plumes, implying the possibility of long-range transport of O3 over the stable MBL over the North Atlantic Ocean in association with NOx regeneration mechanism. The impact of chemical initial and boundary conditions (IC/BCs) on modelled O3 urban plumes was investigated in terms of the background O3 level and the vertical structure of the urban plumes. Simulations with dynamic chemical IC/BCs enhanced the O3 level by 2-12 ppbv on average in the atmospheric layer below 3 km, showing better agreement with the observed NYC plumes and biomass-burning plumes than the simulation with prescribed static IC/BCs. The simulation including MOZART-4 chemical IC/BCs and Alaskan/Canadian wildfire emissions compared better to the observed O3 profiles in the upper atmospheric layer (>~3 km) than models that only accounted for North American anthropogenic/biogenic and wildfire contributions to background ozone. The comparison between models and observations show that chemical IC/BCs must be properly specified to achieve accurate model results.

  15. Rare earth element transport in the western North Atlantic inferred from Nd isotopic observations

    NASA Technical Reports Server (NTRS)

    Piepgras, D. J.; Wasserburg, G. J.

    1987-01-01

    The relationship between the Nd isotopic composition in the Atlantic waters and the origin and circulation of the water masses was investigated. Samples were collected in the western North Atlantic between 7 and 54 deg N. The isotopic composition (Nd-143/Nd-144 ratios) showed extensive vertical structure at all locations. In regions where a thermocline was well-developed, large isotopic shifts were observed across the base of the thermocline, while regions without a thermocline were characterized by much more gradual shifts in isotopic composition with depth. The data reveal an excellent correlation between the Nd isotopic distribution in the western North Atlantic water column and the distribution of water masses identified from temperature and salinity measurements.

  16. Building International Research Partnerships in the North Atlantic-Arctic Region

    NASA Astrophysics Data System (ADS)

    Benway, Heather M.; Hofmann, Eileen; St. John, Michael

    2014-09-01

    The North Atlantic-Arctic region, which is critical to the health and socioeconomic well being of North America and Europe, is susceptible to climate-driven changes in circulation, biogeochemistry, and marine ecosystems. The need for strong investment in the study of biogeochemical and ecosystem processes and interactions with physical processes over a range of time and space scales in this region was clearly stated in the 2013 Galway Declaration, an intergovernmental statement on Atlantic Ocean cooperation (http://europa.eu/rapid/press-release_IP-13-459_en.htm). Subsequently, a workshop was held to bring together researchers from the United States, Canada, and Europe with expertise across multiple disciplines to discuss an international research initiative focused on key features, processes, and ecosystem services (e.g., Atlantic Meridional Overturning Circulation, spring bloom dynamics, fisheries, etc.) and associated sensitivities to climate changes.

  17. Global Cosmic Ray Intensity Changes, Solar Activity Variations and Geomagnetic Disturbances as North Atlantic Hurricane Precursors

    NASA Astrophysics Data System (ADS)

    Kavlakov, S. P.

    It was shown that specific changes of the sunspots (SS) number, cosmic ray (CR) intensity and geomagnetic activity indices AP and KP were statistically noticeable in the interval of 30 days before the appearance of a cyclonic rotational system over the North Atlantic, developing gradually in a major hurricane.

  18. Stratigraphic potential of Bolboforma significantly increased by new finds in the North Atlantic and South Pacific

    USGS Publications Warehouse

    Poag, C. Wylie; Karowe, A. I.

    1986-01-01

    Until now, the genus Bolboforma, a problematic group of calcareous microfossils, has been recorded only in Oligocene to Pliocene marine sedimentary rocks, chiefly in the eastern North Atlantic region. We add to this eastern North Atlantic record six new sites and eleven undescribed species from the continental slopes of Ireland and Morocco. More significantly, we record, for the first time, abundant assemblages of Bolboforma on the western side of the North Atlantic and in the western South Pacific. Seven boreholes on the continental shelf and slope of New Jersey and Virginia contain ten species, three of which are new. Two species are present in two outcrops in eastern Mississippi and four are present in a borehole in the coastal plain of Virginia. On the Lord Howe Rise, west of New Zealand, a DSDP corehole has yielded a rich assemblage including four undescribed species. In addition to expanding the geographic distribution of Bolboforma, our work extends the known stratigraphic range downward into the upper Eocene on both sides of the North Atlantic and in the western South Pacific. Our findings firmly support the inference of a planktonic life style for Bolboforma, which implies a significant potential for biostratigraphic, paleobiogeographic, and paleoenvironmental studies, on both a local and global scale. We recommend a concerted effort to further document the nature and distribution of Bolboforma.

  19. Nearshore marine benthic invertebrates moving north along the U.S. Atlantic coast

    EPA Science Inventory

    Numerous species have shifted their ranges north in response to global warming. We examined 21 years (1990-2010) of marine benthic invertebrate data from the National Coastal Assessment’s monitoring of nearshore waters along the US Atlantic coast. Data came from three bioge...

  20. Cenozoic unconformities and depositional supersequences of North Atlantic continental margins: testing the Vail model

    SciTech Connect

    Poag, C.W.; Ward, L.W.

    1987-02-01

    Integrated outcrop, borehole, and seismic reflection stratigraphy from the US and Irish margins of the North Atlantic basin reveals a framework of Cenozoic depositional supersequences and interregional unconformities that resembles the Vail depositional model. Paleobathymetric and paleoceanographic analyses of associated microfossil assemblages indicate a genetic link between the depositional framework and the relative position of sea level.

  1. Climate change impact on seaweed meadow distribution in the North Atlantic rocky intertidal.

    PubMed

    Jueterbock, Alexander; Tyberghein, Lennert; Verbruggen, Heroen; Coyer, James A; Olsen, Jeanine L; Hoarau, Galice

    2013-05-01

    The North-Atlantic has warmed faster than all other ocean basins and climate change scenarios predict sea surface temperature isotherms to shift up to 600 km northwards by the end of the 21st century. The pole-ward shift has already begun for many temperate seaweed species that are important intertidal foundation species. We asked the question: Where will climate change have the greatest impact on three foundational, macroalgal species that occur along North-Atlantic shores: Fucus serratus, Fucus vesiculosus, and Ascophyllum nodosum? To predict distributional changes of these key species under three IPCC (Intergovernmental Panel on Climate Change) climate change scenarios (A2, A1B, and B1) over the coming two centuries, we generated Ecological Niche Models with the program MAXENT. Model predictions suggest that these three species will shift northwards as an assemblage or "unit" and that phytogeographic changes will be most pronounced in the southern Arctic and the southern temperate provinces. Our models predict that Arctic shores in Canada, Greenland, and Spitsbergen will become suitable for all three species by 2100. Shores south of 45° North will become unsuitable for at least two of the three focal species on both the Northwest- and Northeast-Atlantic coasts by 2200. If these foundational species are unable to adapt to the rising temperatures, they will lose their centers of genetic diversity and their loss will trigger an unpredictable shift in the North-Atlantic intertidal ecosystem. PMID:23762521

  2. Micropaleontological evidence for increased meridional heat transport in the North Atlantic Ocean during the pliocene

    USGS Publications Warehouse

    Dowsett, H.J.; Cronin, T. M.; Poore, R.Z.; Thompson, R.S.; Whatley, R.C.; Wood, A.M.

    1992-01-01

    The Middle Pliocene (???3 million years ago) has been identified as the last time the Earth was significantly warmer than it was during the Last Interglacial and Holocene. A quantitative micropaleontological paleotemperature transect from equator to high latitudes in the North Atlantic indicates that Middle Pliocene warmth involved increased meridional oceanic heat transport.

  3. Genetic discontinuity among regional populations of Lophelia perfusa in the North Atlantic Ocean

    USGS Publications Warehouse

    Morrison, Cheryl L.

    2011-01-01

    Knowledge of the degree to which populations are connected through larval dispersal is imperative to effective management, yet little is known about larval dispersal ability or population connectivity in Lophelia pertusa, the dominant framework-forming coral on the continental slope in the North Atlantic Ocean. Using nine microsatellite DNA markers, we assessed the spatial scale and pattern of genetic connectivity across a large portion of the range of L. pertusa in the North Atlantic Ocean. A Bayesian modeling approach found four distinct genetic groupings corresponding to ocean regions: Gulf of Mexico, coastal southeastern U.S., New England Seamounts, and eastern North Atlantic Ocean. An isolation-by-distance pattern was supported across the study area. Estimates of pairwise population differentiation were greatest with the deepest populations, the New England Seamounts (average FST = 0.156). Differentiation was intermediate with the eastern North Atlantic populations (FST = 0.085), and smallest between southeastern U.S. and Gulf of Mexico populations (FST = 0.019), with evidence of admixture off the southeastern Florida peninsula. Connectivity across larger geographic distances within regions suggests that some larvae are broadly dispersed. Heterozygote deficiencies were detected within the majority of localities suggesting deviation from random mating. Gene flow between ocean regions appears restricted, thus, the most effective management scheme for L. pertusa involves regional reserve networks

  4. Genetic discontinuity among regional populations of Lophelia pertusa in the North Atlantic Ocean

    USGS Publications Warehouse

    Morrison, C.L.; Ross, S.W.; Nizinski, M.S.; Brooke, S.; Jarnegren, J.; Waller, R.G.; Johnson, R.L.; King, T.L.

    2011-01-01

    Knowledge of the degree to which populations are connected through larval dispersal is imperative to effective management, yet little is known about larval dispersal ability or population connectivity in Lophelia pertusa, the dominant framework-forming coral on the continental slope in the North Atlantic Ocean. Using nine microsatellite DNA markers, we assessed the spatial scale and pattern of genetic connectivity across a large portion of the range of L. pertusa in the North Atlantic Ocean. A Bayesian modeling approach found four distinct genetic groupings corresponding to ocean regions: Gulf of Mexico, coastal southeastern U. S., New England Seamounts, and eastern North Atlantic Ocean. An isolation-by-distance pattern was supported across the study area. Estimates of pairwise population differentiation were greatest with the deepest populations, the New England Seamounts (average FST = 0.156). Differentiation was intermediate with the eastern North Atlantic populations (FST = 0.085), and smallest between southeastern U. S. and Gulf of Mexico populations (FST = 0.019), with evidence of admixture off the southeastern Florida peninsula. Connectivity across larger geographic distances within regions suggests that some larvae are broadly dispersed. Heterozygote deficiencies were detected within the majority of localities suggesting deviation from random mating. Gene flow between ocean regions appears restricted, thus, the most effective management scheme for L. pertusa involves regional reserve networks. ?? 2011 US Government.

  5. 77 FR 25892 - Security Zones; North Atlantic Treaty Organization (NATO) Summit, Chicago, IL

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-02

    ... proposed rule (77 FR 13232) that would establish four separate security zones in the Chicago Harbor and Chicago River during the NATO Summit. This statement is incorrect. The Coast Guard received one comment... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA87 Security Zones; North Atlantic Treaty Organization...

  6. Whales, Dolphins, and Porpoises of the Western North Atlantic: A Guide to Their Identification.

    ERIC Educational Resources Information Center

    Leatherwood, Stephen; And Others

    This field guide is designed to permit observers to identify the cetaceans (whales, dolphins, and porpoises) they see in western North Atlantic, including the Caribbean Sea, the Gulf of Mexico, and the coastal waters of the United States and Canada. The animals described are not grouped by scientific relationships but by similarities in appearance…

  7. North Atlantic meridional overturning circulation variations from GRACE ocean bottom pressure anomalies

    NASA Astrophysics Data System (ADS)

    Landerer, Felix W.; Wiese, David N.; Bentel, Katrin; Boening, Carmen; Watkins, Michael M.

    2015-10-01

    Concerns about North Atlantic Meridional Overturning Circulation (NAMOC) changes imply the need for a continuous, large-scale observation capability to detect changes on interannual to decadal time scales. Here we present the first measurements of Lower North Atlantic Deep Water (LNADW) transport changes using only time-variable gravity observations from Gravity Recovery and Climate Experiment (GRACE) satellites from 2003 until now. Improved monthly gravity field retrievals allow the detection of North Atlantic interannual bottom pressure anomalies and LNADW transport estimates that are in good agreement with those from the Rapid Climate Change-Meridional Overturning Circulation and Heatflux Array (RAPID/MOCHA). Concurrent with the observed AMOC transport anomalies from late 2009 through early 2010, GRACE measured ocean bottom pressures changes in the 3000-5000 m deep western North Atlantic on the order of 20 mm-H2O (200 Pa), implying a southward volume transport anomaly in that layer of approximately -5.5 sverdrup. Our results highlight the efficacy of space gravimetry for observing AMOC variations to evaluate latitudinal coherency and long-term variability.

  8. Cenozoic unconformities and depositional supersequences of North Atlantic continental margins: testing the Vail model

    USGS Publications Warehouse

    Poag, C. Wylie; Ward, Lauck W.

    1987-01-01

    Integrated outcrop, borehole, and seismic reflection stratigraphy from the U.S. and Irish margins of the North Atlantic basin reveals a framework of Cenozoic depositional supersequences and interregional unconformities that resembles the Vail depositional model. Paleo-bathymetric and paleoceanographic analyses of associated microfossil assemblages indicate a genetic link between the depositional framework and the relative position of sea level.

  9. Cadmium in the North Atlantic: Implication for global cadmium-phosphorus relationship

    NASA Astrophysics Data System (ADS)

    Wu, Jingfeng; Roshan, Saeed

    2015-06-01

    Dissolved cadmium (Cd) distribution was determined in the tropical-subtropical North Atlantic along GEOTRACES GA03 section (US GEOTRACES 2010 and 2011 cruises). A pronounced mid-depth Cd maximum extends from the productive tropical eastern North Atlantic where subsurface waters in the upper themocline are depleted in dissolved oxygen. At this Cd maximum, Cd depletion relative to phosphate (PO4) is observed in the Cd vs. PO4 plot, but the relative Cd depletion is not present in the plot of Cd:PO4 ratio vs depth. The apparent relative Cd depletion at the Cd maximum appears to reflect a depth-dependent variation of Cd:PO4 ratio commonly observed in the world ocean. Such depth dependent variation of Cd:PO4 ratio may result from the regeneration of Cd from Cd-poor particulate organic carbon (POC) in the upper ocean and from Cd-rich POC in the deep ocean. The vertical Cd regeneration may lead to the observed difference in deep water Cd:PO4 ratio between the North Atlantic and North Pacific, if Cd to phosphorus ratio in the POC flux to the deep ocean is higher in the Pacific than in the Atlantic.

  10. Surface temperatures of the Mid-Pliocene North Atlantic Ocean: Implications for future climate

    USGS Publications Warehouse

    Dowsett, H.J.; Chandler, M.A.; Robinson, M.M.

    2009-01-01

    The Mid-Pliocene is the most recent interval in the Earth's history to have experienced warming of the magnitude predicted for the second half of the twenty-first century and is, therefore, a possible analogue for future climate conditions. With continents basically in their current positions and atmospheric CO2 similar to early twenty-first century values, the cause of Mid-Pliocene warmth remains elusive. Understanding the behaviour of the North Atlantic Ocean during the Mid-Pliocene is integral to evaluating future climate scenarios owing to its role in deep water formation and its sensitivity to climate change. Under the framework of the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) sea surface reconstruction, we synthesize Mid-Pliocene North Atlantic studies by PRISM members and others, describing each region of the North Atlantic in terms of palaeoceanography. We then relate Mid-Pliocene sea surface conditions to expectations of future warming. The results of the data and climate model comparisons suggest that the North Atlantic is more sensitive to climate change than is suggested by climate model simulations, raising the concern that estimates of future climate change are conservative. ?? 2008 The Royal Society.

  11. WATERFOWL-HABITAT ASSOCIATIONS DURING WINTER IN A URBAN NORTH ATLANTIC ESTUARY

    EPA Science Inventory

    Coastal habitats near urban centres in North Atlantic estuaries often support substantial numbers of wintering waterfowl, but little is known of the effects of landscape setting and urbanisation on habitat use. We conducted surveys of waterfowl at 32 wintering sites in Narraganse...

  12. Carbon Cycling in the Arctic Archipelago: The Export of Pacific Carbon to the North Atlantic

    NASA Astrophysics Data System (ADS)

    Shadwick, E. H.; Papakyriakou, T.; Prowe, A. E. F.; Leong, D.; Moore, S.; Thomas, H.

    2009-04-01

    The Arctic Ocean is expected to be disproportionately sensitive to climatic changes, and thought to be an area where such changes might be detected. The Arctic hydrological cycle is influenced by: runoff and precipitation, sea ice formation/melting, and the inflow of saline waters from Bering and Fram Straits and the Barents Sea Shelf. Pacific water is recognizable as low salinity water, with high concentrations of dissolved inorganic carbon (DIC), flowing from the Arctic Ocean to the North Atlantic via the Canadian Arctic Archipelago. We present DIC data from an east-west section through the Archipelago, as part of the Canadian International Polar Year initiatives. The fractions of Pacific and Arctic Ocean waters leaving the Archipelago and entering Baffin Bay, and subsequently the North Atlantic, are computed. The eastward transport of carbon from the Pacific, via the Arctic, to the North Atlantic is estimated. Altered mixing ratios of Pacific and freshwater in the Arctic Ocean have been recorded in recent decades. Any climatically driven alterations in the composition of waters leaving the Arctic Archipelago may have implications for anthropogenic CO2 uptake, and hence ocean acidification, in the subpolar and temperate North Atlantic.

  13. Carbon cycling in the Arctic Archipelago: the export of Pacific carbon to the North Atlantic

    NASA Astrophysics Data System (ADS)

    Shadwick, E. H.; Papakyriakou, T.; Prowe, A. E. F.; Leong, D.; Moore, S. A.; Thomas, H.

    2009-01-01

    The Arctic Ocean is expected to be disproportionately sensitive to climatic changes, and is thought to be an area where such changes might be detected. The Arctic hydrological cycle is influenced by: runoff and precipitation, sea ice formation/melting, and the inflow of saline waters from Bering and Fram Straits and the Barents Sea Shelf. Pacific water is recognizable as intermediate salinity water, with high concentrations of dissolved inorganic carbon (DIC), flowing from the Arctic Ocean to the North Atlantic via the Canadian Arctic Archipelago. We present DIC data from an east-west section through the Archipelago, as part of the Canadian International Polar Year initiatives. The fractions of Pacific and Arctic Ocean waters leaving the Archipelago and entering Baffin Bay, and subsequently the North Atlantic, are computed. The eastward transport of carbon from the Pacific, via the Arctic, to the North Atlantic is estimated. Altered mixing ratios of Pacific and freshwater in the Arctic Ocean have been recorded in recent decades. Any climatically driven alterations in the composition of waters leaving the Arctic Archipelago may have implications for anthropogenic CO2 uptake, and hence ocean acidification, in the subpolar and temperate North Atlantic.

  14. Climate change impact on seaweed meadow distribution in the North Atlantic rocky intertidal.

    PubMed

    Jueterbock, Alexander; Tyberghein, Lennert; Verbruggen, Heroen; Coyer, James A; Olsen, Jeanine L; Hoarau, Galice

    2013-05-01

    The North-Atlantic has warmed faster than all other ocean basins and climate change scenarios predict sea surface temperature isotherms to shift up to 600 km northwards by the end of the 21st century. The pole-ward shift has already begun for many temperate seaweed species that are important intertidal foundation species. We asked the question: Where will climate change have the greatest impact on three foundational, macroalgal species that occur along North-Atlantic shores: Fucus serratus, Fucus vesiculosus, and Ascophyllum nodosum? To predict distributional changes of these key species under three IPCC (Intergovernmental Panel on Climate Change) climate change scenarios (A2, A1B, and B1) over the coming two centuries, we generated Ecological Niche Models with the program MAXENT. Model predictions suggest that these three species will shift northwards as an assemblage or "unit" and that phytogeographic changes will be most pronounced in the southern Arctic and the southern temperate provinces. Our models predict that Arctic shores in Canada, Greenland, and Spitsbergen will become suitable for all three species by 2100. Shores south of 45° North will become unsuitable for at least two of the three focal species on both the Northwest- and Northeast-Atlantic coasts by 2200. If these foundational species are unable to adapt to the rising temperatures, they will lose their centers of genetic diversity and their loss will trigger an unpredictable shift in the North-Atlantic intertidal ecosystem.

  15. Biofuels and North American agriculture--implications for the health and safety of North American producers.

    PubMed

    Gunderson, Paul D

    2008-01-01

    This decade has provided North American agricultural producers with opportunity to not only produce fiber and food, but also fuel and other industrial products. The drivers incenting this development could be sustained well into the future, therefore workforce safety and health implications are likely to persist for some time. Within production agriculture, the 'feedstock growth and harvest cycle' and 'transport' sectors possess the changing exposures experienced by workers. The Conference explored the following exposures: distiller's grains and bio-processing byproducts, spent catalyst, solvent brine, microbial agents, genetically modified organisms, discharge effluent, H2O dilutes, change in cropping patterns and resultant use of different seeding and harvest technologies, pests (whether target or non-target), and rural traffic resulting from concentrated movement of massive quantities of biomass and grain. Other issues of a more general public health nature such as watershed implications, other environmental impacts, emissions, uneven economic development potential, public safety issues associated with transport of both fuel and other industrial products, and rural emergency medical service need were explored. And, agronomic impacts were noted, including tillage change, potassium buildup in soil, nutrient depletion, sedimentation and erosion of tillable soil, and local esthetics. It was concluded that rural venues for formation and exploration of public policy need to be created.

  16. The Impact of the AMO on North Atlantic Tropical Cyclone Activity in the 21st Century

    NASA Astrophysics Data System (ADS)

    LaRow, T.; Stefanova, L. B.

    2013-05-01

    In the North Atlantic Ocean, tropical cyclone (TC) activity exhibits a quasi multidecadal cycle with large interannual variability superimposed on the low frequency multidecadal TC cycle. The cause of the low frequency multidecadal TC cycle is not completely understood and there is scientific debate as to whether or not the observed increase in measures of Atlantic TC activity in past decades is attributable to increased SSTs caused by anthropogenic forcing, is part of a natural low frequency cycle, or perhaps some combination of both. One low frequency SST mode of variability in the North Atlantic is the Atlantic Multidecadal Oscillation (AMO). The AMO is approximately a 70-year cycle of North Atlantic SSTs with about a 0.49°C range in temperature which is larger than either the range in interannual to decadal variability (0.46°C) or the trend from 1870-1999 (0.38°C). Prediction of the AMO, due to a combination of its unforced nature and model imperfections, is only possible to some degree for the nearest decade, or in a probabilistic sense. Statistical analysis shows that during the positive phase of the AMO, North Atlantic hurricane activity tends to be enhanced, especially major hurricanes. In this study, we examine TC activity in two 20-yr time periods (2020-2039 and 2080-2099) using SSTs from the CMIP5 RCP4.5 scenario simulation as prescribed lower boundary conditions in the FSU/COAPS atmospheric general circulation model. The AMO signal from the CMIP5 SSTs is removed and replaced with the observed maximum positive and negative amplitude phases of the AMO obtained from the HadISST dataset. Examination of the impacts of the AMO phases and anthropogenic warming on future TC activity will be discussed.

  17. Medicinal history of North American Veratrum

    PubMed Central

    Chandler, Christopher M.

    2014-01-01

    Plants belonging to the genus Veratrum have been used throughout history for their medicinal properties. During the nineteenth and twentieth centuries, phytochemical investigations revealed a host of steroidal alkaloids in Veratrum species, some of which are potent bioactives. This review discusses Veratrum species that grow in North America with a focus on the medicinal history of these plants and the steroidal alkaloids they contain. While significant reviews have been devoted to singularly describing the plant species within the genus Veratrum (botany), the staggering breadth of alkaloids isolated from these and related plants (phytochemistry), and the intricacies of how the various alkaloids act on their biological targets (physiology and biochemistry), this review will straddle the margins of the aforementioned disciplines in an attempt to provide a unified, coherent picture of the Veratrum plants of North America and the medicinal uses of their bioactive steroidal alkaloids. PMID:25379034

  18. The decline of North American freshwater fishes

    USGS Publications Warehouse

    Walsh, Stephen J.; Jelks, Howard L.; Burkhead, Noel M.

    2009-01-01

    North America has a broad array of freshwater ecosystems because of the continent's complex geography and geological history. Within a multitude of habitats—that include streams, large rivers, natural lakes, springs, and wetlands—rich assemblages of fishes reside, representing diverse taxonomic groups with unique ecological requirements. They face an unprecedented conservation crisis.1 In the last few decades, the proportion of inland fishes of North America, which are considered imperiled or extinct, increased from 20 to 40%.2 Although extinctions have occurred, many species and populations are declining in range size and abundance. The fish biota of the continent as a whole remains diverse; however, we can take action to stem any further declines.

  19. Building a North American Spatial Data Infrastructure

    USGS Publications Warehouse

    Coleman, D.J.; Nebert, D.D.

    1998-01-01

    This paper addresses the state of spatial data infrastructures within North America in late 1997. After providing some background underlying the philosophy and development of the SDI concept, the authors discuss effects of technology, institutions, and standardization that confront the cohesive implementation of a common infrastructure today. The paper concludes with a comparative framework and specific examples of elements and initiatives defining respective spatial data infrastructure initiatives in the United States and Canada.

  20. Pb isotopes in surficial pelagic sediments from the North Atlantic

    NASA Technical Reports Server (NTRS)

    Hamelin, B.; Grousset, F.; Sholkovitz, E. R.

    1990-01-01

    The concentration of Pb and its isotopic composition were measured in samples from the surface of sea-water sediments obtained from the northeastern Atlantic, the Sargasso Sea, and the U.S. continental shelf, with the purpose of investigating changes in Pb sources due to the anthropogenic perturbation that took place in modern times. It was found that the anthropogenic Pb input to marine sediments due to the increase of Pb contamination over the ocean during the last century could be identified in all these samples. However, samples from eastern and western Atlantic had very different Pb isotopic profiles, each reflecting the character of anthropogenic Pb emissions from the European and U.S. industries, respectively.

  1. Origins of the 1988 north american drought.

    PubMed

    Trenberth, K E; Branstator, G W; Arkin, P A

    1988-12-23

    The 1988 summer drought in the United States was the most extensive in many years. Because the drought developed in different places at different times, not all regional effects can be traced to the same cause. Along the West Coast and in the northwestern United States drought conditions developed during 1987 in association with the 1986 to 1987 El Niño in the tropical Pacific Ocean. Record low rainfalls from April to June 1988 led to rapid development of drought in the North Central United States. Strong anticyclonic conditions and a northward displaced jet stream in the upper atmosphere over North America throughout this period were only part of pronounced and distinctive wavetrain of anomalies in the atmospheric circulation that appeared to emanate from the tropical Pacific. Below average sea surface temperatures along the equator in the Pacific in the northern spring of 1988, combined with warmer than normal water from 10 degrees to 20 degrees N, led to a northward displaced but still active intertropical convergence zone (ITCZ) southeast of Hawaii. Results from a steady-state planetarywave atmospheric model indicate that the atmospheric heating anomalies associated with the displaced ITCZ can force an anomalous wavetrain across North America similar to that observed. Land surface processes probably contributed to the severity and persistence of the drought; however, the large-scale atmospheric circulation perturbations associated with natural variations in the coupled atmosphere-ocean system in the tropical Pacific were most likely the primary cause. PMID:17730574

  2. Detrital sources and water mass circulation in the tropical North Atlantic during the Late Cretaceous to Paleogene

    NASA Astrophysics Data System (ADS)

    Martin, E. E.; Pugh, E.; Kamenov, G. D.; MacLeod, K. G.

    2014-12-01

    Seawater Nd isotopes from fossil fish teeth in Campanian to Paleogene calcareous claystone on Demerara Rise in the tropical North Atlantic record a change from epsilon Nd values of -17 to -11 during the late Maastrichtian. This shift has been identified in three different Ocean Drilling Program (ODP) sites that span from 600 to 1500 m paleodepths (ODP sites 1259, 1260 and 1261) and has been interpreted as a transition from a warm saline intermediate water mass formed on the South American margin, referred to as Demerara Bottom Water, to a source from the North Atlantic. A study of corresponding detrital Sr, Nd and Pb isotopes was undertaken to confirm the isotopic values derived from fish teeth record water mass compositions rather than diagenesis or boundary exchange. Several leaching procedures designed to remove Fe-Mn oxide coatings and the seawater signature they carry from the detrital fractions were tested. Sr isotopic data indicate a 0.02 M hydroxylamine hydrochloride (HH) leach was ineffective at removing the Fe-Mn oxides whereas a 1.0 M HH leach produced detrital Sr isotopic values that were consistent for all three sites and plotted farther from the seawater value. Detrital isotopic results can be divided into three intervals: 1) 73 - 66 Ma, when DBW is present, 2) 66 - 61 Ma, during the transition to North Atlantic sources, and 3) <61 Ma, when North Atlantic sources appear to dominate. During interval 1, detrital Nd isotopes increase gradually, while Sr and Pb isotopic ratios are relatively constant. Leading into interval 2, detrital Nd isotopes are fairly constant while there is a stepwise increase in Sr and Pb isotopes. Leading into interval 3, there is a large increase in Nd and decrease in Sr isotopes and a slight decrease in Pb isotopes. The subtle differences in the timing of changes in fish teeth and detrital Nd isotopes suggest the seawater signal is responding to changes in water mass rather than changes in sediment composition (boundary

  3. Thanksgiving Address of the North American Indian Ohenton Kariwatehkwen.

    ERIC Educational Resources Information Center

    Mitchell, Watenriio (Michael), Comp.; And Others

    Translated by the North American Indian Travelling College, this traditional Thanksgiving Address is delivered before and after all meetings and ceremonies of the Iroquois people. Through this address, the Creator is introduced into a ceremony, social dance, or council, and, at the end of the meeting, the address brings the minds of the people…

  4. 10. Historic American Buildings Survey Photocopy BASEMENT PLAN, NORTH ELEVATION, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. Historic American Buildings Survey Photocopy BASEMENT PLAN, NORTH ELEVATION, ARCHITECT'S ORIGINAL PLAN Restricted: Not to be reproduced without written permission from Beinecke Rare Books Library, Yale University, New Haven, Conn. - John Pitkin Norton House, 52 Hillhouse Avenue, New Haven, New Haven County, CT

  5. North American Indians: Smithsonian Institution Teacher's Resource Guide.

    ERIC Educational Resources Information Center

    National Museum of Natural History, Washington, DC.

    This teacher's resource guide produced by the National Museum of Natural History (Smithsonian Institution) is a collection of materials about North American Indians covering 3 categories, including an introduction, selected bibliographies, and a listing photographs and portraits. Additionally, there is a collecting of answers to questions that…

  6. The North American Free Trade Agreement. Headline Series No. 299.

    ERIC Educational Resources Information Center

    Grayson, George W.

    This document discusses the North American Free Trade Agreement (NAFTA) as a debate over the wisdom of opening the southern United States border to the free flow of goods and services between the United States and Mexico. The book is divided into six chapters. The first is a basic introduction to the development of the idea of a free trade…

  7. North-American Microtektites are More Oxidised than Tektites

    NASA Astrophysics Data System (ADS)

    Giuli, G.; Cicconi, M. R.; Eeckhout, S. G.; Koeberl, C.; Glass, B. P.; Pratesi, G.; Paris, E.

    2012-03-01

    Microtektites from the Australasian and Ivory Coast strewn fields (SF) show low values of the Fe^3^+/Fe_t_o_t ratio, comparable to tektites from the same SF. In contrast, microtektites from the North American SF show a wider range (from 0 to 0.75).

  8. The 2011 North American strawberry symposium: an introduction

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The 2011 Symposium was held in conjunction with the 32nd North American Strawberry Growers Association (NASGA) Annual Conference on 8-11 Feb. 2011, at the Doubletree Hotel in Tampa, FL. The scientific program was conducted over two days and featured five sessions of oral and poster presentations sp...

  9. Strange country this: lesbianism and North American Indian tribes.

    PubMed

    Grahn, J

    1986-05-01

    This article is an exploration of historical names and functions of gay and lesbian people among traditional North American Indian tribes. Some detailed descriptions of individual offices are included, such as "manly hearted" women and shamanic cross-dressing men, as well as the original definition of "dyke" and "ceremonial lesbian" as described by Paula Gunn Allen (Laguna Pueblo). PMID:3531323

  10. Cardiovascular Health Promotion in North Florida African-American Churches.

    ERIC Educational Resources Information Center

    Turner, Lori W.; And Others

    1995-01-01

    This article describes cardiovascular problems of minority populations, exploring ways that churches can help their communities and describing the outcomes of a model intervention on four African American churches in rural north Florida. Positive outcomes were observed, particularly regarding community members' participation in health promotion…

  11. 9. Historic American Buildings Survey April 1959 REAR (NORTH) ELEVATION ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. Historic American Buildings Survey April 1959 REAR (NORTH) ELEVATION FROM THE N. W. - Southeast Area Survey, 600-602 & 1100 G Street (House), 1002,1006 Eye Street (House), 808-810,812-814, & 1016 K Street (House), 817-819 L Street (House), Washington, District of Columbia, DC

  12. Depressed Affect and Historical Loss among North American Indigenous Adolescents

    ERIC Educational Resources Information Center

    Whitbeck, Les B.; Walls, Melissa L.; Johnson, Kurt D.; Morrisseau, Allan D.; McDougall, Cindy M.

    2009-01-01

    This study reports on the prevalence and correlates of perceived historical loss among 459 North American Indigenous adolescents aged 11-13 years from the northern Midwest of the United States and central Canada. The adolescents reported daily or more thoughts of historical loss at rates similar to their female caretakers. Confirmatory factor…

  13. Annotated Bibliography of Articles Pertaining to Native North Americans.

    ERIC Educational Resources Information Center

    Saskatchewan Univ., Saskatoon. Indian and Northern Curriculum Resources Centre.

    The annotated bibliography is designed to help a person find information about American Indians, Metis, and Eskimos of North America. It attempts to categorize and separate fields of interests. The books, magazines, and newspaper articles were printed from 1959-1971. Approximately 335 references are listed. Addresses are in the Appendix. The…

  14. Teaching Culture in a North American Context: Halloween Revisited.

    ERIC Educational Resources Information Center

    Mollica, Anthony; And Others

    1996-01-01

    Notes that information presented in dialog form in a foreign language lends itself more easily to conversation than does intricate narrative prose. Using background information on Halloween, the article adapts the text to present information about the target culture as well as to humorously present facts about the North American festivity.…

  15. A Canadian Lens on Facilitating Factors for North American Partnerships

    ERIC Educational Resources Information Center

    Olson, Christa Lee

    2013-01-01

    What does it take to develop and maintain effective international education partnerships between institutions in the Canada, Mexico, and United States? This was a driving question for the qualitative study funded by a Fulbright-Enders-Garcia grant examining the relationship between North American partnerships and campus internationalization.…

  16. Sex Education Attitudes and Outcomes among North American Women

    ERIC Educational Resources Information Center

    Williams, Monnica T.; Bonner, Laura

    2006-01-01

    Attitudes and outcomes of sex education received by North American women are examined via an Internet survey (N = 1,400). Mean age was 19.5, with 24% reporting one or more unplanned pregnancies. Women were more satisfied with sex education from informal sources than from parents, schools, and physicians. Those receiving sex education from parents…

  17. 3. Historic American Buildings Survey UNDATED EXTERIOR SHOWING NORTH AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. Historic American Buildings Survey UNDATED EXTERIOR SHOWING NORTH AND EAST FACADES (View B) This view shows clapboards on gable end and therefore, predates View A which shows shingles in upper gable From the collection of Mrs. L. T. Hazall, descendent of Rev. Woodward - Reverend John Woodward House, 409 Forbes Avenue, New Haven, New Haven County, CT

  18. 12. Historic American Buildings Survey L. C. Durette, Photographer NORTH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. Historic American Buildings Survey L. C. Durette, Photographer NORTH EAST CORNER POST, 2d FLOOR, SHOWING MOULDING OF ORIGINAL SET BACK CUT AWAY. ON THE EAST SIDE THE MOULDING REMAINS - Doe Garrison, Lamprey River & Great Bay, Newmarket, Rockingham County, NH

  19. Cultural Values in Latin and North American Cities

    ERIC Educational Resources Information Center

    Manaster, Guy J.; Ahumada, Isa

    1971-01-01

    Study was conducted among adolescents in Puerto Rico, and replicated earlier studies in Buenos Aires and Chicago. Implications were drawn from frequencies in San Juan and compared with the Latin passive" pattern in Buenos Aires and the North American active" pattern in Chicago. (DM)

  20. Highlights of the North American CF Conference 2013.

    PubMed

    Walshaw, Martin

    2014-06-01

    This is a personal selection of papers that were presented at the 27th North American Cystic Fibrosis Conference held in Salt Lake City in October 2013. The papers discussed in this review are thought to be of particular interest to CF caregivers in the UK. PMID:24821547

  1. Wave climate variability in the North Atlantic in recent decades in the winter period using numerical modeling

    NASA Astrophysics Data System (ADS)

    Markina, M. Yu.; Gavrikov, A. V.

    2016-05-01

    The study focuses on investigating significant wave height, including both mean and extreme values, in the North Atlantic in winter during the period from 1979 to 2010. We perform a 32-year wind wave hindcast for the North Atlantic using a spectral ocean wave model (WaveWatch III) and a high-resolution nonhydrostatic atmospheric model (WRF-ARW), which provides the wind forcing function. Analysis of the 32-year hindcast of wave characteristics in the North Atlantic reveals stronger mean and extreme waves simulated with high resolution modeling systems and identifies significant downward trends in the mean significant wave height in the subpolar North Atlantic. Such trends were not found in the wave characteristics from ERA-Interim reanalysis. At the same time, the 32-year hindcast did not confirm the statistically significance of strong positive trends in the central Atlantic diagnosed by ERA-Interim reanalysis; differences between the reanalysis and hindcast are discussed.

  2. On which timescales do gas transfer velocities control North Atlantic CO2 flux variability?

    NASA Astrophysics Data System (ADS)

    Couldrey, Matthew P.; Oliver, Kevin I. C.; Yool, Andrew; Halloran, Paul R.; Achterberg, Eric P.

    2016-05-01

    The North Atlantic is an important basin for the global ocean's uptake of anthropogenic and natural carbon dioxide (CO2), but the mechanisms controlling this carbon flux are not fully understood. The air-sea flux of CO2, F, is the product of a gas transfer velocity, k, the air-sea CO2 concentration gradient, ΔpCO2, and the temperature- and salinity-dependent solubility coefficient, α. k is difficult to constrain, representing the dominant uncertainty in F on short (instantaneous to interannual) timescales. Previous work shows that in the North Atlantic, ΔpCO2 and k both contribute significantly to interannual F variability but that k is unimportant for multidecadal variability. On some timescale between interannual and multidecadal, gas transfer velocity variability and its associated uncertainty become negligible. Here we quantify this critical timescale for the first time. Using an ocean model, we determine the importance of k, ΔpCO2, and α on a range of timescales. On interannual and shorter timescales, both ΔpCO2 and k are important controls on F. In contrast, pentadal to multidecadal North Atlantic flux variability is driven almost entirely by ΔpCO2; k contributes less than 25%. Finally, we explore how accurately one can estimate North Atlantic F without a knowledge of nonseasonal k variability, finding it possible for interannual and longer timescales. These findings suggest that continued efforts to better constrain gas transfer velocities are necessary to quantify interannual variability in the North Atlantic carbon sink. However, uncertainty in k variability is unlikely to limit the accuracy of estimates of longer-term flux variability.

  3. On which timescales do gas transfer velocities control North Atlantic CO2 flux variability?

    NASA Astrophysics Data System (ADS)

    Couldrey, Matthew; Oliver, Kevin; Yool, Andrew; Halloran, Paul; Achterberg, Eric

    2016-04-01

    The North Atlantic is an important basin for the global ocean's uptake of anthropogenic and natural carbon dioxide (CO2), but the mechanisms controlling this carbon flux are not fully understood. The air-sea flux of CO2, F, is the product of a gas transfer velocity, k, the air-sea CO2concentration gradient, ΔpCO2, and the temperature and salinity-dependent solubility coefficient, α. k is difficult to constrain, representing the dominant uncertainty in F on short (instantaneous to interannual) timescales. Previous work shows that in the North Atlantic, ΔpCO2and k both contribute significantly to interannual F variability, but that k is unimportant for multidecadal variability. On some timescale between interannual and multidecadal, gas transfer velocity variability and its associated uncertainty become negligible. Here, we quantify this critical timescale for the first time. Using an ocean model, we determine the importance of k, ΔpCO2and α on a range of timescales. On interannual and shorter timescales, both ΔpCO2and k are important controls on F. In contrast, pentadal to multidecadal North Atlantic flux variability is driven almost entirely by ΔpCO2; k contributes less than 25%. Finally, we explore how accurately one can estimate North Atlantic F without a knowledge of non-seasonal k variability, finding it possible for interannual and longer timescales. These findings suggest that continued efforts to better constrain gas transfer velocities are necessary to quantify interannual variability in the North Atlantic carbon sink. However, uncertainty in k variability is unlikely to limit the accuracy of estimates of longer term flux variability.

  4. 76 FR 36892 - Atlantic Highly Migratory Species; 2011 North and South Atlantic Swordfish Quotas

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-23

    ... 2011 fishing year to account for 2010 underharvests and landings. This proposed rule incorporates International Commission for the Conservation of Atlantic Tunas (ICCAT) recommendations 10-02 and 09-03 into the quota adjustments for the 2011 fishing year. These recommendations extend, through the 2011 fishing...

  5. 77 FR 45273 - Atlantic Highly Migratory Species; North and South Atlantic Swordfish Quotas and Management Measures

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-31

    ... Caribbean Sea and Gulf of Mexico. DATES: Effective on August 30, 2012. ADDRESSES: Copies of the supporting... a CK minimum size measurement of 25 inches. The proposed rule (77 FR 25669, May 1, 2012) and draft... FR 56929) analyzed the impacts resulting from Recommendation 06-03 for South Atlantic...

  6. 76 FR 56120 - Atlantic Highly Migratory Species; North and South Atlantic Swordfish Quotas

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-12

    ..., including the Caribbean Sea and Gulf of Mexico, by establishing annual quotas. The effects on commercial and... species, and other species (including swordfish) targeted in high seas fisheries or incidentally captured in tuna fisheries, in the Atlantic Ocean and its adjacent seas. The ICCAT Commission can, on...

  7. 78 FR 28758 - Atlantic Highly Migratory Species; North and South Atlantic 2013 Commercial Swordfish Quotas

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-16

    ..., including the Caribbean Sea and Gulf of Mexico. This action implements ICCAT recommendations, consistent... Specifications Final Rule (July 31, 2012; 77 FR 45273). The impacts resulting from the 2013 South Atlantic... Quota Specification Final Rule (October 5, 2007; 72 FR 56929). The quota adjustments in this final...

  8. 77 FR 25669 - Atlantic Highly Migratory Species; North and South Atlantic Swordfish Quotas and Management Measures

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-01

    ... the Caribbean Sea and Gulf of Mexico. This action implements ICCAT recommendations, consistent with... (AA). On October 2, 2006, NMFS published in the Federal Register (71 FR 58058) final regulations... the conservation of tuna and tuna-like species in the Atlantic Ocean and adjacent seas....

  9. Biogeography and divergent patterns of body size disparification in North American minnows.

    PubMed

    Martin, Samuel D; Bonett, Ronald M

    2015-12-01

    Body size is one of the most important traits influencing an organism's ecology and a major axis of evolutionary change. We examined body size disparification in the highly speciose North American minnows (Cyprinidae), which exhibit diverse body sizes and ecologies, including the giant piscivorous pikeminnows. We estimated a novel phylogeny for 285 species based on a supermatrix alignment of seven mitochondrial and ten nuclear genes, and used this to reconstruct ancestral body sizes (log-total length) and ancestral area. Additionally, given that fishes inhabiting Pacific drainages have historically been subjected to frequent local extinctions due to periodic flooding, droughts, and low drainage connectivity, we also compared body size disparification between the highly speciose Atlantic drainages and comparatively depauperate Pacific drainages. We found that dispersal between Atlantic and Pacific drainages has been infrequent and generally occurred in minnows with southerly distributions, where drainage systems are younger and less stable. The long isolation between Atlantic and Pacific drainages has allowed for divergent patterns of morphological disparification; we found higher rates of body size disparification in minnows from the environmentally harsher Pacific drainages. We propose several possible explanations for the observed patterns of size disparification in the context of habitat stability, niche space, and species diversification. PMID:26210938

  10. Skeleton of Extinct North American Sea Mink ( Mustela macrodon)

    NASA Astrophysics Data System (ADS)

    Mead, Jim I.; Spiess, Arthur E.; Sobolik, Kristin D.

    2000-03-01

    Mustela macrodon (extinct sea mink) is known only from prehistoric and historic Native American shell middens dating less than 5100 years old along coastal islands of the Gulf of Maine, northeastern North America. The species is distinct from all known extant subspecies of M. vison (American mink) but still belongs to the North American subgenus Vison. Metric comparisons between M. macrodon and five subspecies of M. vison, using skull, mandible, humerus, radius, femur, and tibia skeletal elements, show that M. macrodon is larger in overall size and robustness and is proportionately larger in the dental region. Many habitat-related parallels exist between coastal island mink of the Gulf of Maine and those of the Alexander Archipelago, southeastern Alaska, where the overall largest living subspecies of mink is found (M. v. nesolestes).

  11. Minor floods of 1938 in the North Atlantic States

    USGS Publications Warehouse

    ,

    1947-01-01

    Five noteworthy floods occurred during 1938 in the North Atlantic States. The first flood was in January, the others were in June, July, August, and September. The floods of January, June, and August were relatively local events in Connecticut, New Jersey, and New York, respectively. The floods of July and September were widespread, reaching from New Jersey and New York to New Hampshire in generally coincident locations. The flood of September, the most severe, is described in appropriate detail in Water-Supply Paper 867; the others in this volume are in separate sections arranged chronologically. Extraordinary floods in Connecticut during January 1938 resulted from a critical combination of warm rainfall and virtual overnight melting of the accumulated snowfall of winter. Seven small streams in central and western Connecticut rose to levels on January 25 higher than those reached during the great floods of March 1936. Crest discharge of these streams approximated 100 second-feet per square mile. Ice cover was loosened and sent downstream in recurrent jams. In general, the larger rivers did not attain extraordinary stages. The Connecticut River at Hartford peaked at a stage 3.6 feet above ordinary flood level. Direct damage by the flood was relatively small. Snow cover on January 20, at the beginning of the rains, varied from 0.25 inch along the coast to 2.75 inches water equivalent in the northern part of the State. Precipitation between January 24 and 26 exceeded 2.75 inches in only three small areas. Total supply as water in snow and precipitation did not exceed 4.8 inches over any tributary area. Maximum measured flood run-off was 2.7 inches. The flood of June 1938 in New Jersey was the immediate result of a 30-hour rainstorm on June 26-27 that centered along a line extending from Odessa, Del., to Milton, N. J. Storm rainfall exceeded 5 inches over a total area of 2,900 square miles. River stages in the central parts of the storm area rose to levels that

  12. North American snake and scorpion envenomations.

    PubMed

    Wilbeck, Jennifer; Gresham, Chip

    2013-06-01

    Envenomations by snakes and scorpions in North America, although uncommon, do occur, and the victims may seek medical treatment. Combined, snake and scorpion encounters result in more than 25,000 calls a year to poison centers. Although some similarities exist with respect to general signs of envenomation and treatment, specific nuances distinguish the medical care to be anticipated and therapies available. Regardless of geographic practice area, exposures will occur that may result in a significant envenomation. This article provides critical care nurses with fundamental knowledge of varied snake and scorpion envenomation presentations and treatments to assist in optimizing patient outcomes. PMID:23692937

  13. 78 FR 26349 - Notice of Commissioner and Staff Attendance at North American Electric Reliability Corporation...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-06

    ... Energy Regulatory Commission Notice of Commissioner and Staff Attendance at North American Electric... the Commission and/or Commission staff may attend the following meetings: North American Electric... Compliance Committee, Finance and Audit Committee, and Standards Oversight and Technology Committee...

  14. 75 FR 4374 - North American Electric Reliability Corporation; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-27

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission North American Electric Reliability Corporation; Notice of Filing January 20, 2010. Take notice that on January 19, 2010, North American Electric Reliability Corporation...

  15. Variability of cyclones over the North Atlantic and Europe since 1871

    NASA Astrophysics Data System (ADS)

    Welker, C.; Martius, O.

    2012-04-01

    The scarce availability of long-term atmospheric data series has so far limited the analysis of low-frequency activity and intensity changes of cyclones over the North Atlantic and Europe. A novel reanalysis product, the Twentieth Century Reanalysis (20CR; Compo et al., 2011), spanning 1871 to present, offers potentially a very valuable resource for the analysis of the decadal-scale variability of cyclones over the North Atlantic sector and Europe. In the 20CR, only observations of synoptic surface pressure were assimilated. Monthly sea surface temperature and sea ice distributions served as boundary conditions. An Ensemble Kalman Filter assimilation technique was applied. "First guess" fields were obtained from an ensemble (with 56 members) of short-range numerical weather prediction forecasts. We apply the cyclone identification algorithm of Wernli and Schwierz (2006) to this data set, i.e. to each individual ensemble member. This enables us to give an uncertainty estimation of our findings. We find that 20CR shows a temporally relatively homogeneous representation of cyclone activity over Europe and great parts of the North Atlantic. Pronounced decadal-scale variability is found both in the frequency and intensity of cyclones over the North Atlantic and Europe. The low-frequency variability is consistently represented in all ensemble members. Our analyses indicate that in the past approximately 140 years the variability of cyclone activity and intensity over the North Atlantic and Europe can principally be associated with the North Atlantic Oscillation and secondary with a pattern similar to the East Atlantic pattern. Regionally however, the correlation between cyclone activity and these dominant modes of variability changes over time. Compo, G. P., J. S. Whitaker, P. D. Sardeshmukh, N. Matsui, R. J. Allan, X. Yin, B. E. Gleason, R. S. Vose, G. Rutledge, P. Bessemoulin, S. Brönnimann, M. Brunet, R. I. Crouthamel, A. N. Grant, P. Y. Groisman, P. D. Jones, M. C

  16. Decadal-Scale Tropical North Atlantic Climate Variability Recorded in Slow Growing Cape Verde Corals

    NASA Astrophysics Data System (ADS)

    Moses, C. S.; Swart, P. K.; Dodge, R. E.; Helmle, K. P.; Thorrold, S.

    2002-12-01

    The decadal to century scale climate variability of the tropical North Atlantic has major implications for both neighboring coastal and inland areas. Changes in patterns of sea surface temperature (SST) and SST anomalies (SSTA) in the tropical North Atlantic are known to affect rainfall in Florida, South America, and sub-Saharan Africa, as well as the number of major hurricanes formed in the Atlantic. Because of the significance of these connections, it is important to further increase our predictive capacity for the recognition of trends and cycles in tropical North Atlantic SST and SSTA. Located at 15° N latitude off the west coast of sub-Saharan Africa, the Cape Verde Islands are an ideal geographic location to search for records of the Tropical North Atlantic Index (TNA). Such patterns are present in proxy indicators of climate (O, C, Sr/Ca and Mg/Ca) recorded in the skeletons of slow growing corals, such as Siderastrea radians, found in Cape Verde (growth rate = 1-2 mm/yr). These corals represent an archive for SST and SSTA records that exceed the instrumental period of the eastern tropical North Atlantic. We cored corals from several different locations within the Cape Verde archipelago and analyzed them for stable isotopes (δ13C and δ18O) and minor elements (Sr, Mg, and Ba). The δ18O signal present in these corals shows a distinct relationship to the TNA over the better part of the last 100 years. In addition, the δ18O record in several of these corals also records the onset of the latest Sahel (11°-18° N in Africa) drought which began in 1970. The Sr/Ca and Mg/Ca records of these corals indicate a slight warming of the waters around Cape Verde during the last 100 years, as well as accurately recording the El Niño events of 1982-83 and 1997-98. The correlations present between the records in these corals and the known instrumental record for the eastern tropical North Atlantic suggests that the fluctuations recorded in the proxy indicators may be

  17. The timing of the last deglaciation in North Atlantic climate records.

    PubMed

    Waelbroeck, C; Duplessy, J C; Michel, E; Labeyrie, L; Paillard, D; Duprat, J

    2001-08-16

    To determine the mechanisms governing the last deglaciation and the sequence of events that lead to deglaciation, it is important to obtain a temporal framework that applies to both continental and marine climate records. Radiocarbon dating has been widely used to derive calendar dates for marine sediments, but it rests on the assumption that the 'apparent age' of surface water (the age of surface water relative to the atmosphere) has remained constant over time. Here we present new evidence for variation in the apparent age of surface water (or reservoir age) in the North Atlantic ocean north of 40 degrees N over the past 20,000 years. In two cores we found apparent surface-water ages to be larger than those of today by 1,230 +/- 600 and 1,940 +/- 750 years at the end of the Heinrich 1 surge event (15,000 years BP) and by 820 +/- 430 to 1,010 +/- 340 years at the end of the Younger Dryas cold episode. During the warm Bølling-Allerød period, between these two periods of large reservoir ages, apparent surface-water ages were comparable to present values. Our results allow us to reconcile the chronologies from ice cores and the North Atlantic marine records over the entire deglaciation period. Moreover, the data imply that marine carbon dates from the North Atlantic north of 40 degrees N will need to be corrected for these highly variable effects.

  18. Invasion of the red seaweed Heterosiphonia japonica spans biogeographic provinces in the Western North Atlantic Ocean.

    PubMed

    Newton, Christine; Bracken, Matthew E S; McConville, Megan; Rodrigue, Katherine; Thornber, Carol S

    2013-01-01

    The recent invasion of the red alga Heterosiphonia japonica in the western North Atlantic Ocean has provided a unique opportunity to study invasion dynamics across a biogeographical barrier. Native to the western North Pacific Ocean, initial collections in 2007 and 2009 restricted the western North Atlantic range of this invader to Rhode Island, USA. However, through subtidal community surveys, we document the presence of Heterosiphonia in coastal waters from Maine to New York, USA, a distance of more than 700 km. This geographical distribution spans a well-known biogeographical barrier at Cape Cod, Massachusetts. Despite significant differences in subtidal community structure north and south of Cape Cod, Heterosiphonia was found at all but two sites surveyed in both biogeographic provinces, suggesting that this invader is capable of rapid expansion over broad geographic ranges. Across all sites surveyed, Heterosiphonia comprised 14% of the subtidal benthic community. However, average abundances of nearly 80% were found at some locations. As a drifting macrophyte, Heterosiphonia was found as intertidal wrack in abundances of up to 65% of the biomass washed up along beaches surveyed. Our surveys suggest that the high abundance of Heterosiphonia has already led to marked changes in subtidal community structure; we found significantly lower species richness in recipient communities with higher Heterosiphona abundances. Based on temperature and salinity tolerances of the European populations, we believe Heterosiphonia has the potential to invade and alter subtidal communities from Florida to Newfoundland in the western North Atlantic.

  19. The influence of cut off lows on sulfate burdens over the North Atlantic during April, 1987

    SciTech Connect

    Benkovitz, C.M.; Miller, M.A.; Schwartz, S.E.; Kwon, O.U.

    2001-01-14

    The authors have presented examples from a modeling study of the development of sulfur burdens over North America, the North Atlantic Ocean and Europe during April, 1987 using observation-derived meteorological data to represent the actual conditions for this period, focusing on the influence of cut-off lows on SO{sub 2} and sulfate column burdens over the North Atlantic Ocean. The analysis demonstrates that these systems can serve either as sources or sinks of sulfate, and that the major factor governing their resulting effect is the position during its formative stages relative to (a) sources of moisture, and (b) sulfur emissions, which regulates the availability of sulfur, cloud liquid water for sulfur oxidation, and the amount of precipitation for sulfate removal produced in the later stages of the life cycle.

  20. Century-scale variability of Coralline Algal Calcification Rates in the North Pacific and North Atlantic

    NASA Astrophysics Data System (ADS)

    Halfar, J.; Chan, P.; Adey, W.; Hetzinger, S.; Williams, B.; Steneck, R.; Lebednik, P.

    2012-04-01

    Ocean acidification may inhibit calcification pathways of marine plants and animals. Recently, it has been suggested that aragonitic tropical corals and other marine calcifiers already exhibit declining calcification rates. Greater oceanic CO2 uptake at mid-to-high latitudes may result in greater inhibition of calcium carbonate secretion in subarctic organisms than in those at lower latitudes. Such inhibition may be particularly evident in the metabolically expensive high Mg-calcite skeletons of the shallow-water, habitat-forming coralline algae. It has been shown that biogenic high Mg-calcites exceed the solubility of aragonite at approximately 12 mol% MgCO3. Here we present the first century-scale records of calcification rates in the coralline alga Clathromorphum sp. from the North Pacific/Bering Sea region and the subarctic NW Atlantic. Clathromorphum forms annual growth increments in its massive skeleton and is known to have a lifespan of up to several centuries. The seasonal MgCO3 range in Clathromorphum from our subarctic collection sites fluctuates between 10-15 mol%. Century-long time series of calcification rates - the product of skeletal density and linear extension - were generated at submonthly resolution using Micro Computer Tomography. Results indicate that coralline algal calcification rates display multidecadal cycles that covary with regional climate indices such as the Pacific Decadal Oscillation. Unlike studies of other marine calcifiers, this study has not detected a significant decline in calcification rates during the past decades. This is likely attributable to Clathromorphum calcification being metabolically driven, with the organism maintaining significant physiological control over both placement and dissolution of carbonate. Most carbonate in Clathromorphum cells is deposited along an inner wall embedded in an organic matrix of very small, radially-placed high magnesium calcite crystals.

  1. Phylogeny of North American Powassan virus.

    PubMed

    Ebel, G D; Spielman, A; Telford, S R

    2001-07-01

    To determine whether Powassan virus (POW) and deer tick virus (DTV) constitute distinct flaviviral populations transmitted by ixodid ticks in North America, we analysed diverse nucleotide sequences from 16 strains of these viruses. Two distinct genetic lineages are evident, which may be defined by geographical and host associations. The nucleotide and amino acid sequences of lineage one (comprising New York and Canadian POW isolates) are highly conserved across time and space, but those of lineage two (comprising isolates from deer ticks and a fox) are more variable. The divergence between lineages is much greater than the variation within either lineage, and lineage two appears to be more diverse genetically than is lineage one. Application of McDonald-Kreitman tests to the sequences of these strains indicates that adaptive evolution of the envelope protein separates lineage one from lineage two. The two POW lineages circulating in North America possess a pattern of genetic diversity suggesting that they comprise distinct subtypes that may perpetuate in separate enzootic cycles. PMID:11413377

  2. Gulf Stream variability in western North Atlantic off Cape Lookout, North Carolina

    NASA Astrophysics Data System (ADS)

    Pedersen, A. B.; Seidenkrantz, M.-S.; Mienis, F.; Fischel, A.; Frank, N.; Hebbeln, D.

    2012-04-01

    outflow to the North Atlantic weakened the thermohaline circulation, which was especially clear in zone 2. Around 8200 years the thermohaline circulation was even more reduced, due to a meltwater pulse of lake Agassiz and Ojibway. At this time the foraminifera indicate that the current at Cape Lookout was very weak.

  3. North American vegetation patterns observed with the NOAA-7 advanced very high resolution radiometer. [North America

    NASA Technical Reports Server (NTRS)

    Goward, S. N.; Tucker, C. J.; Dye, D. G.

    1985-01-01

    Spectral vegetation index measurements derived from remotely sensed observations show great promise as a means to improve knowledge of land vegetation patterns. The daily, global observations acquired by the advanced very high resolution radiometer, a sensor on the current series of U.S. National Oceanic and Atmospheric Administration meteorological satellites, may be particularly well suited for global studies of vegetation. Preliminary results from analysis of North American observations, extending from April to November 1982, show that the vegetation index patterns observed correspond to the known seasonality of North American natural and cultivated vegetation. Integration of the observations over the growing season produced measurements that are related to net primary productivity patterns of the major North American natural vegetation formations. Regions of intense cultivation were observed as anomalous areas in the integrated growing season measurements. Significant information on seasonality, annual extent and interannual variability of vegetation photosynthetic activity at continental and global scales can be derived from these satellite observations.

  4. Incursions of southern-sourced water into the deep North Atlantic during late Pliocene glacial intensification

    NASA Astrophysics Data System (ADS)

    Lang, David C.; Bailey, Ian; Wilson, Paul A.; Chalk, Thomas B.; Foster, Gavin L.; Gutjahr, Marcus

    2016-05-01

    The circulation and internal structure of the oceans exert a strong influence on Earth's climate because they control latitudinal heat transport and the segregation of carbon between the atmosphere and the abyss. Circulation change, particularly in the Atlantic Ocean, is widely suggested to have been instrumental in the intensification of Northern Hemisphere glaciation when large ice sheets first developed on North America and Eurasia during the late Pliocene, approximately 2.7 million years ago. Yet the mechanistic link and cause/effect relationship between ocean circulation and glaciation are debated. Here we present new records of North Atlantic Ocean structure using the carbon and neodymium isotopic composition of marine sediments recording deep water for both the Last Glacial to Holocene (35-5 thousand years ago) and the late Pliocene to earliest Pleistocene (3.3-2.4 million years ago). Our data show no secular change. Instead we document major southern-sourced water incursions into the deep North Atlantic during prominent glacials from 2.7 million years ago. Our results suggest that Atlantic circulation acts as a positive feedback rather than as an underlying cause of late Pliocene Northern Hemisphere glaciation. We propose that, once surface Southern Ocean stratification and/or extensive sea-ice cover was established, cold-stage expansions of southern-sourced water such as those documented here enhanced carbon dioxide storage in the deep ocean, helping to increase the amplitude of glacial cycles.

  5. Influence of prolonged Anomalies in North Atlantic Sea Surface Temperature on Winter Windstorms

    NASA Astrophysics Data System (ADS)

    Höschel, Ines; Schuster, Mareike; Grieger, Jens; Ulbrich, Uwe

    2016-04-01

    The focus of this presentation is on decadal scale variations in the frequency and in the intensity of mid-latitude winter windstorms. Projections for the end of the next century are often beyond the time horizon of business, thus there is an increasing interest on decadal prediction, especially for infrastructural planning and in the insurance industry. One source of decadal predictability is the Atlantic multidecadal variability (AMV), a change in the sea surface temperature of the North Atlantic, strongly linked to the meridional overturning circulation. Correlation patterns between annual AMV-indices and annual mean of geopotential height at 500 hPa in reanalysis data show an anti-correlation in the North Atlantic. That is, during AMV warm phases the North Atlantic Oscillation (NAO) is more negative. Consequently, AMV should influence the characteristics of winter windstorms at multi-year scales. For the presented investigations a 10-member ensemble of 38-year-long idealized simulations with the atmosphere model ECHAM6 with lower boundary conditions, representing warm and cool phases of the AMV, is used. In the idealized simulations, the anti-correlation between AMV and NAO is well represented. For the identification of winter windstorms an objective wind tracking algorithm based on the exceedance of the local 98th percentile of 10m wind speed is applied. Storms under AMV-warm and AMV-cool conditions will be compared in terms of storm track density and probability distribution of storm characteristics.

  6. The intertropical convergence zone modulates intense hurricane strikes on the western North Atlantic margin

    PubMed Central

    van Hengstum, Peter J.; Donnelly, Jeffrey P.; Fall, Patricia L.; Toomey, Michael R.; Albury, Nancy A.; Kakuk, Brian

    2016-01-01

    Most Atlantic hurricanes form in the Main Development Region between 9°N to 20°N along the northern edge of the Intertropical Convergence Zone (ITCZ). Previous research has suggested that meridional shifts in the ITCZ position on geologic timescales can modulate hurricane activity, but continuous and long-term storm records are needed from multiple sites to assess this hypothesis. Here we present a 3000 year record of intense hurricane strikes in the northern Bahamas (Abaco Island) based on overwash deposits in a coastal sinkhole, which indicates that the ITCZ has likely helped modulate intense hurricane strikes on the western North Atlantic margin on millennial to centennial-scales. The new reconstruction closely matches a previous reconstruction from Puerto Rico, and documents a period of elevated intense hurricane activity on the western North Atlantic margin from 2500 to 1000 years ago when paleo precipitation proxies suggest that the ITCZ occupied a more northern position. Considering that anthropogenic warming is predicted to be focused in the northern hemisphere in the coming century, these results provide a prehistoric analog that an attendant northern ITCZ shift in the future may again return the western North Atlantic margin to an active hurricane interval. PMID:26906670

  7. The intertropical convergence zone modulates intense hurricane strikes on the western North Atlantic margin.

    PubMed

    van Hengstum, Peter J; Donnelly, Jeffrey P; Fall, Patricia L; Toomey, Michael R; Albury, Nancy A; Kakuk, Brian

    2016-01-01

    Most Atlantic hurricanes form in the Main Development Region between 9°N to 20°N along the northern edge of the Intertropical Convergence Zone (ITCZ). Previous research has suggested that meridional shifts in the ITCZ position on geologic timescales can modulate hurricane activity, but continuous and long-term storm records are needed from multiple sites to assess this hypothesis. Here we present a 3000 year record of intense hurricane strikes in the northern Bahamas (Abaco Island) based on overwash deposits in a coastal sinkhole, which indicates that the ITCZ has likely helped modulate intense hurricane strikes on the western North Atlantic margin on millennial to centennial-scales. The new reconstruction closely matches a previous reconstruction from Puerto Rico, and documents a period of elevated intense hurricane activity on the western North Atlantic margin from 2500 to 1000 years ago when paleo precipitation proxies suggest that the ITCZ occupied a more northern position. Considering that anthropogenic warming is predicted to be focused in the northern hemisphere in the coming century, these results provide a prehistoric analog that an attendant northern ITCZ shift in the future may again return the western North Atlantic margin to an active hurricane interval. PMID:26906670

  8. The intertropical convergence zone modulates intense hurricane strikes on the western North Atlantic margin

    NASA Astrophysics Data System (ADS)

    van Hengstum, Peter J.; Donnelly, Jeffrey P.; Fall, Patricia L.; Toomey, Michael R.; Albury, Nancy A.; Kakuk, Brian

    2016-02-01

    Most Atlantic hurricanes form in the Main Development Region between 9°N to 20°N along the northern edge of the Intertropical Convergence Zone (ITCZ). Previous research has suggested that meridional shifts in the ITCZ position on geologic timescales can modulate hurricane activity, but continuous and long-term storm records are needed from multiple sites to assess this hypothesis. Here we present a 3000 year record of intense hurricane strikes in the northern Bahamas (Abaco Island) based on overwash deposits in a coastal sinkhole, which indicates that the ITCZ has likely helped modulate intense hurricane strikes on the western North Atlantic margin on millennial to centennial-scales. The new reconstruction closely matches a previous reconstruction from Puerto Rico, and documents a period of elevated intense hurricane activity on the western North Atlantic margin from 2500 to 1000 years ago when paleo precipitation proxies suggest that the ITCZ occupied a more northern position. Considering that anthropogenic warming is predicted to be focused in the northern hemisphere in the coming century, these results provide a prehistoric analog that an attendant northern ITCZ shift in the future may again return the western North Atlantic margin to an active hurricane interval.

  9. A reversal of climatic trends in the North Atlantic since 2005

    NASA Astrophysics Data System (ADS)

    Robson, Jon; Ortega, Pablo; Sutton, Rowan

    2016-07-01

    In the mid-1990s the North Atlantic subpolar gyre warmed rapidly, which had important climate impacts such as increased hurricane numbers and changes to rainfall over Africa, Europe and North America. Evidence suggests that the warming was largely due to a strengthening of the ocean circulation, particularly the Atlantic Meridional Overturning Circulation. Since the mid-1990s direct and indirect measurements have suggested a decline in the strength of the ocean circulation, which is expected to lead to a reduction in northward heat transport. Here we show that since 2005 a large volume of the upper North Atlantic Ocean has cooled significantly by approximately 0.45 °C or 1.5 × 1022 J, reversing the previous warming trend. By analysing observations and a state-of-the-art climate model, we show that this cooling is consistent with a reduction in the strength of the ocean circulation and heat transport, linked to record low densities in the deep Labrador Sea. The low density in the deep Labrador Sea is primarily due to deep ocean warming since 1995, but a long-term freshening also played a role. The observed upper ocean cooling since 2005 is not consistent with the hypothesis that anthropogenic aerosols directly drive Atlantic temperatures.

  10. Optimisation of A 1d-ecosystem Model To Observations In The North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Schartau, M.; Oschlies, A.

    An optimisation experiment is performed with a vertically resolved, nitrogen based ecosystem model, comprising four state variables (1D-NPZD model): dissolved inor- ganic nitrogen (N), phytoplankton (P), herbivorous zooplankton (Z) and detritus (D). Parameter values of the NPZD-model are optimised while regarding observational data from three locations in the North Atlantic simultaneously: Bermuda Atlantic Time-series Study (BATS), data of the North Atlantic Bloom Experiment (NABE) and observations from Ocean Weather Ship-India (OWS-INDIA). The simultaneous opti- misation yields a best parameter set which can be utilized for basin wide simulations in coupled physical-biological (general circulation) models of the North Atlantic. After optimisation of the 1D-NPZD model, systematic discrepancies between 14C-fixation rates and modelled primary production are emphasized. Using the optimal parame- ter estimates for coupled 3D-simulations, the biogeochemical fluxes show substantial differences in contrast to previous model results. For instance, rapid recycling of or- ganic matter enhances primary production rates. This becomes most evident within the oligotrophic regions of the subtropical gyre.

  11. The intertropical convergence zone modulates intense hurricane strikes on the western North Atlantic margin.

    PubMed

    van Hengstum, Peter J; Donnelly, Jeffrey P; Fall, Patricia L; Toomey, Michael R; Albury, Nancy A; Kakuk, Brian

    2016-01-01

    Most Atlantic hurricanes form in the Main Development Region between 9°N to 20°N along the northern edge of the Intertropical Convergence Zone (ITCZ). Previous research has suggested that meridional shifts in the ITCZ position on geologic timescales can modulate hurricane activity, but continuous and long-term storm records are needed from multiple sites to assess this hypothesis. Here we present a 3000 year record of intense hurricane strikes in the northern Bahamas (Abaco Island) based on overwash deposits in a coastal sinkhole, which indicates that the ITCZ has likely helped modulate intense hurricane strikes on the western North Atlantic margin on millennial to centennial-scales. The new reconstruction closely matches a previous reconstruction from Puerto Rico, and documents a period of elevated intense hurricane activity on the western North Atlantic margin from 2500 to 1000 years ago when paleo precipitation proxies suggest that the ITCZ occupied a more northern position. Considering that anthropogenic warming is predicted to be focused in the northern hemisphere in the coming century, these results provide a prehistoric analog that an attendant northern ITCZ shift in the future may again return the western North Atlantic margin to an active hurricane interval.

  12. Salt transport in the Subpolar Gyre amplifies North Atlantic climate variability

    NASA Astrophysics Data System (ADS)

    Born, Andreas; Stocker, Thomas F.; Britt Sandø, Anne

    2016-04-01

    Transport of salt in the Irminger Current, the northern branch of the Atlantic Subpolar Gyre coupling the eastern and western subpolar North Atlantic, plays an important role for climate variability across a wide range of time scales. High-resolution ocean modeling and observations indicate that salinities in the eastern subpolar North Atlantic decrease with enhanced circulation of the North Atlantic subpolar gyre. This has led to the perception that a stronger SPG also transports less salt westward, which would weaken deep convection in the Labrador Sea and thus the gyre itself. In this study, we analyze a regional ocean model and a comprehensive global coupled climate model, and show that a stronger SPG transports more salt in the Irminger Current irrespective of lower salinities in its source region. The additional salt converges in the Labrador Sea and the Irminger Basin by eddy transports, increases surface salinity in the western SPG, and favors more intense deep convection. This is part of a positive feedback mechanism with large implications for climate variability and predictability.

  13. Structure of the North American Atlantic Continental Margin.

    USGS Publications Warehouse

    Schlee, J.S.; Klitgord, K.K.

    1986-01-01

    Off E N America, where the structure of the continental margin is essentially constructional, seismic profiles have approximated geologic cross sections up to 10-15km below the sea floor and revealed major structural and stratigraphic features that have regional hydrocarbon potential. These features include a) a block-faulted basement hinge zone; b) a deep, broad, rifted basement filled with clastic sediment and salt; and c) a buried paleoshelf-edge complex that has many forms. The mapping of seismostratigraphic units over the continental shelf, slope, and rise has shown that the margin's developmental state included infilling of a rifted margin, buildup of a carbonate platform, and construction of an onlapping continental-rise wedge that was accompanied by erosion of the slope. -from Authors

  14. Comparative ecology of North Atlantic shores: do differences in players matter for process?

    PubMed

    Jenkins, Stuart R; Moore, Pippa; Burrows, Michael T; Garbary, David J; Hawkins, Stephen J; Ingólfsson, Agnar; Sebens, Kenneth P; Snelgrove, Paul V R; Wethey, David S; Woodin, Sarah A

    2008-11-01

    The contrasting histories of the western and eastern shores of the North Atlantic Ocean provide an excellent opportunity to consider the implications of past events for present ecological processes and the functioning of marine ecosystems. Similarities and differences in assemblage composition have been driven by large-scale events, such as the trans-Arctic interchange, which has shaped the species pool, and cycles of glaciation, which have determined phases of local or regional extinction and colonization. More recently, anthropogenically induced invasions and local extinctions have significantly altered biogeographic distributions. Here we consider for both hard and soft substrata how the presence or absence of key taxa influences the outcomes of trophic and other biological interactions, and evaluate the consequences for community structure and ecosystem functioning. On intertidal hard substratum shores, biodiversity of epilithic microphagous grazers differs across latitudinal and longitudinal scales. Diversity is high in southern Europe but declines to the north and across the Atlantic. Lower diversity and the absence of patellid limpets in Iceland and the northwest Atlantic compared to Europe result in differences in consumer pressure, and an apparent contrast in the importance of herbivory vs. competitive interactions and predation pressure as community structuring processes. Interestingly, despite differences in "process," community patterns are remarkably similar between the east and west. On soft sediment shores, there are conspicuous geographic differences in importance of bioturbators and large digging predators. Hemichordates can be abundant and important infaunal bioturbators in the western Atlantic, but they generally play a much reduced role in the eastern Atlantic. In addition, the number and diversity of digging predators on western Atlantic shores is high; the horseshoe crab, swimming portunid crabs, large whelks, excavating waterfowl, and an

  15. Early arrival of Southern Source Water in the deep North Atlantic prior to Heinrich event 2

    NASA Astrophysics Data System (ADS)

    Gutjahr, Marcus; Lippold, JöRg

    2011-06-01

    The Atlantic Meridional Overturning Circulation (AMOC) plays an important role in the Northern Hemisphere climate system. Significant interest went into the question of how excessive freshwater input through melting of continental ice can affect its overturning vigor and, hence, heat supply, to higher northern latitudes. Such forcing can be tested by investigating its behavior during extreme iceberg discharge events into the open North Atlantic during the last glacial period, the so-called Heinrich events (HE). Here we present neodymium (Nd) isotope compositions of past seawater, a sensitive chemical water mass tag, extracted from sediments of Ocean Drilling Program Site 1063 in the western North Atlantic (Bermuda Rise), covering the period surrounding HE 2, the Last Glacial Maximum, and the early deglaciation. These data are compared with a record of the kinematic circulation tracer (231Pa/230Th)xs extracted from the same sediment core. Both tracers indicate significant circulation changes preceding intense ice rafting during HE 2 by almost 2 kyr. Moreover, the Nd isotope record suggests the presence of deeply ventilating North Atlantic Deep Water early during Marine Isotope Stage 2 until it was replaced by Southern Source Water at ˜27 ka. The early switch to high (Pa/Th)xs and radiogenic ɛNd in relation to intensified ice rafting during HE 2 suggests that ice rafting into the open North Atlantic during major HE 2 was preceded by an early change of the AMOC. This opens the possibility that variations in AMOC contributed to or even triggered the ice sheet instability rather than merely responding to it.

  16. Phylogeographic surveys and apomictic genetic connectivity in the North Atlantic red seaweed Mastocarpus stellatus.

    PubMed

    Li, Jing-Jing; Hu, Zi-Min; Liu, Ruo-Yu; Zhang, Jie; Liu, Shao-Lun; Duan, De-Lin

    2016-01-01

    The North Atlantic red alga Mastocarpus stellatus is characterized by two life histories (sexual-type and direct-type), which correspond to two geographically isolated breeding groups. These features enable M. stellatus to be an interesting model to investigate how environmental shift and apomictic propagation have influenced its population genetic structure, historical demography and distribution dynamic. To test these ideas, we obtained 456 specimens from 15 locations on both sides of the North Atlantic and sequenced portion of the nuclear internal transcribed spacer (ITS), mitochondrial cox2-3 region (COX) and plastid RuBisCo spacer (RLS). Median-joining networks and ML trees inferred from COX and RLS consistently revealed two gene lineages (mtDNA: CN, CS; cpDNA: RN, RS). The concatenated COX and RLS markers yielded three cytotypes: a northern CN-RN, a southern CS-RS and a mixed cytotype CS-RN, which enabled us to roughly separate samples into D (direct-type life-cycle) and S (sexual-type life-cycle) groups (northern CN-RN and mixed cytotype CS-RN=D; southern CS-RS=S). Pairwise FST analysis of the D group revealed a high level of genetic differentiation both along European coasts and across the Atlantic basin. Bayesian skyline plots (BSPs) and IMa analyses indicated that M. stellatus underwent slight demographic expansion at the late-Pleistocene, with the beginning of divergence between lineages dating to c. 0.189Ma (95%HPD: 0.083-0.385Ma). IMa analyses also revealed asymmetric genetic exchange among European populations and a predominant postglacial trans-Atlantic migration from Norway and Galway Bay to North America. Our study highlights the importance of phylogeographic approaches to discover the imprints of climate change, life histories and gene flow in driving population genetic connectivity and biogeographic distribution of intertidal seaweeds in the North Atlantic.

  17. Deglacial Ocean Circulation Scheme at Intermediate Depths in the Tropical North Atlantic

    NASA Astrophysics Data System (ADS)

    Xie, R. C.; Marcantonio, F.; Schmidt, M. W.

    2014-12-01

    In the modern Atlantic Ocean, intermediate water circulation is largely governed by the southward flowing upper North Atlantic Deep Water (NADW) and the northward return flow Antarctic Intermediate Water (AAIW). During the last deglaciation, it is commonly accepted that the southward flow Glacial North Atlantic Intermediate Water, the glacial analogue of NADW, contributed significantly to past variations in intermediate water circulation. However, to date, there is no common consensus of the role AAIW played during the last deglaciation, especially across abrupt climate events such as the Heinrich 1 and the Younger Dryas. This study aims to reconstruct intermediate northern- and southern-sourced water circulation in the tropical North Atlantic during the past 22 kyr and attempts to confine the boundary between AAIW and northern-sourced intermediate waters in the past. High-resolution Nd isotopic compositions (ɛNd thereafter) of fish debris and bulk sediment acid-reductive leachate from the Southern Caribbean (VM12-107; 1079 m) are inconsistent, again casting concerns, as already raised by recent studies, on the reliability of the leachate method in extracting seawater ɛNd signature. This urges the need to carefully verify the seawater ɛNd integrity in sediment acid-reductive leachate in various oceanic settings. Fish debris Nd isotope record in our study displays a two-step decreasing trend from the early deglaciation to early Holocene. We interpret this as recording a two-step deglacial recovery of the upper NADW, given the assumption on a more radiogenic glacial northern-sourced water is valid. Comparing with authigenic ɛNd records in the Florida Straits [1] and the Demarara Rise [2], our new fish debris ɛNd results suggest that, in the tropical western North Atlantic, glacial and deglacial AAIW never penetrated beyond the lower depth limit of modern AAIW. [1] Xie et al., GCA (140) 2014; [2] Huang et al., EPSL (389) 2014

  18. Phylogeographic surveys and apomictic genetic connectivity in the North Atlantic red seaweed Mastocarpus stellatus.

    PubMed

    Li, Jing-Jing; Hu, Zi-Min; Liu, Ruo-Yu; Zhang, Jie; Liu, Shao-Lun; Duan, De-Lin

    2016-01-01

    The North Atlantic red alga Mastocarpus stellatus is characterized by two life histories (sexual-type and direct-type), which correspond to two geographically isolated breeding groups. These features enable M. stellatus to be an interesting model to investigate how environmental shift and apomictic propagation have influenced its population genetic structure, historical demography and distribution dynamic. To test these ideas, we obtained 456 specimens from 15 locations on both sides of the North Atlantic and sequenced portion of the nuclear internal transcribed spacer (ITS), mitochondrial cox2-3 region (COX) and plastid RuBisCo spacer (RLS). Median-joining networks and ML trees inferred from COX and RLS consistently revealed two gene lineages (mtDNA: CN, CS; cpDNA: RN, RS). The concatenated COX and RLS markers yielded three cytotypes: a northern CN-RN, a southern CS-RS and a mixed cytotype CS-RN, which enabled us to roughly separate samples into D (direct-type life-cycle) and S (sexual-type life-cycle) groups (northern CN-RN and mixed cytotype CS-RN=D; southern CS-RS=S). Pairwise FST analysis of the D group revealed a high level of genetic differentiation both along European coasts and across the Atlantic basin. Bayesian skyline plots (BSPs) and IMa analyses indicated that M. stellatus underwent slight demographic expansion at the late-Pleistocene, with the beginning of divergence between lineages dating to c. 0.189Ma (95%HPD: 0.083-0.385Ma). IMa analyses also revealed asymmetric genetic exchange among European populations and a predominant postglacial trans-Atlantic migration from Norway and Galway Bay to North America. Our study highlights the importance of phylogeographic approaches to discover the imprints of climate change, life histories and gene flow in driving population genetic connectivity and biogeographic distribution of intertidal seaweeds in the North Atlantic. PMID:26528630

  19. 78 FR 18333 - North American Electric Reliability Corporation; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-26

    ... Energy Regulatory Commission North American Electric Reliability Corporation; Notice of Filing Take notice that on March 15, 2013, the North American Electric Reliability Corporation (NERC) submitted a... Commission) in North American Electric Reliability Corporation, 138 FERC ] 61,193 (2012) (March 15...

  20. 78 FR 9687 - North American Electric Reliability Corporation; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-11

    ... Energy Regulatory Commission North American Electric Reliability Corporation; Notice of Filing Take notice that on February 1, 2013, the North American Electric Reliability Corporation (NERC) submitted a... North American Electric Reliability Corporation, 141 FERC ] 61,086 (2012) (November 2 Order). Any...