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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. 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.

  4. 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.

  5. Variations in North American Summer Precipitation Driven by the Atlantic Multidecadal Oscillation

    NASA Astrophysics Data System (ADS)

    Hu, Q. S.; Feng, S.; Oglesby, R. J.

    2010-12-01

    Understanding the development and persistence of atmospheric circulation regimes during the Atlantic Multidecadal Oscillation (AMO) and how these regimes and associated summer rainfall patterns are modulated by higher frequency (e.g., interannual) forcing is essential for improving our understanding and prediction of summer precipitation variations in North America. In this study, a general circulation model (GCM) is used to gain such understanding. Two experimental runs are conducted with SST anomalies imposed in the North Atlantic Ocean that represent the warm and cold phases of the AMO. Climatological SST were used elsewhere. The results yield summer (June, July and August) precipitation anomalies in North America that closely match observed anomaly patterns. Drier/wetter conditions occur over most of America during the warm/cold phase of the AMO. During the warm phase of the AMO, the summer season North Atlantic Subtropical High pressure system (NASH) weakens. This induces a three-cell circulation anomaly pattern in the western U.S., the western subtropical North Atlantic, and the eastern subtropical North Pacific. Accompanying these circulation anomalies is increased summer rainfall in both the southeastern U.S. and in the North American monsoon region, but decreased precipitation in most of North America, particularly the central U.S. In the cold phase of the AMO, the NASH is enhanced, and the circulation anomalies feature a broad region of anomalous southerly flow from the Gulf of Mexico into the U.S. Great Plains and anomalous northerly flow in the northern Great Plains. This contributes to enhanced precipitation for most of the central U.S. During both phases, the near-surface as well as the mid and upper troposphere act in concert to discourage (in the warm phase of the AMO) and encourage (in cold phase) summer precipitation development in central and western North America.

  6. The spring relationship between the Pacific-North American pattern and the North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

    Soulard, Nicholas; Lin, Hai

    2017-01-01

    The Pacific-North American pattern (PNA) and North Atlantic Oscillation (NAO) are two dominant modes of low-frequency variability in the Northern Hemisphere winter. Generally these two patterns are separable and uncorrelated in both space and time. However, dating back to the 1970s there have been studies which have linked the Aleutian and Icelandic low intensities, and shown that a significant temporal correlation does, on occasion, occur. Each of these semi-permanent low pressure systems is a part of the PNA and NAO patterns, respectively, and therefore, given a link between the two semi-permanent low pressure systems, we explore whether a link between the PNA and NAO also appears. Recently studies have found such a link during the winters of certain decades. The present study, documents an observed relationship between the PNA and NAO which is consistently present during the spring and early summer. This relationship is shown to be due to the fact that the PNA and NAO are spatially overlapping projections of the same pattern of variability, given by the first EOF of 500 hPa geopotential height. Both the PNA and NAO patterns correlate more strongly to the first EOF's spatial pattern, resembling the Aleutian low-Icelandic low seesaw pattern, than the rotated EOF (REOF) loading patterns used to compute their respective indices. Furthermore, when the two patterns are correlated, the effect of El-Nino on the Northern Hemisphere is separate from the pattern associated with the PNA. Finally, we examine a 21-year period in the winter for which the PNA and NAO are significantly correlated, and find that the conclusions drawn from the spring hold true. The results presented herein demonstrate that defining the PNA and NAO based upon typical loading patterns may not be the ideal approach; especially given that the patterns are spatially similar and covary in time.

  7. A biomarker approach to assessing xenobiotic exposure in Atlantic tomcod from the North American Atlantic coast.

    PubMed Central

    Wirgin, I I; Grunwald, C; Courtenay, S; Kreamer, G L; Reichert, W L; Stein, J E

    1994-01-01

    We determined levels of hepatic cytochrome P4501A (CYP1A) mRNA, hepatic DNA adducts, and fluorescent aromatic compounds (FACs) in bile, a measure of exposure to polyaromatic hydrocarbons, in Atlantic tomcod from six river systems ranging from highly polluted to relatively pristine on the northeast North American coast (the Hudson River, New York; the St. Lawrence River, Quebec; the Miramichi River, New Brunswick; the Saco and Royal rivers, Maine; and the Margaree River, Nova Scotia). Hudson River tomcod showed the greatest response for all parameters, and tomcod from the Margaree River exhibited the least response. Tomcod from the Miramichi River exhibited marked induction of CYP1A mRNA but low levels of hepatic DNA adducts and biliary FACs, whereas fish from the St. Lawrence River showed no induction of CYP1A mRNA and moderately elevated levels of DNA adducts and biliary FACs. In tomcod from the Hudson and Miramichi rivers, the levels of CYP1A mRNA were 28 times and 14 times, respectively, as great as the levels in fish from the St. Lawrence, Saco/Royal, and Margaree rivers. Mean levels of DNA adducts varied from 120 nmol adducts/mol bases in Hudson River tomcod to < 3 nmol adducts/mol bases in fish from the Miramichi and Margaree rivers. Concentrations of FACs in the bile of tomcod from the Hudson and St. Lawrence rivers were 8 and 1.8 times, respectively, as great as the concentrations in tomcod from the Miramichi River and Margaree River. In tomcod from the Hudson River, all three biomarkers were markedly elevated; in the St. Lawrence River two biomarkers were elevated, in the Miramichi River one was elevated, but no biomarker was substantially elevated in fish from the Saco/Royal and Margaree rivers. Elevated levels of hepatic DNA adducts and biliary FACs in tomcod from the Hudson River suggest increased exposure to PAHs, consistent with previous studies. Images p764-a Figure 1. Figure 2. a Figure 2. b Figure 2. c Figure 3. Figure 4. Figure 5. a Figure 5. b

  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. Chromosomal differences between European and North American Atlantic salmon discovered by linkage mapping and supported by fluorescence in situ hybridization analysis

    PubMed Central

    2012-01-01

    Background Geographical isolation has generated a distinct difference between Atlantic salmon of European and North American Atlantic origin. The European Atlantic salmon generally has 29 pairs of chromosomes and 74 chromosome arms whereas it has been reported that the North American Atlantic salmon has 27 chromosome pairs and an NF of 72. In order to predict the major chromosomal rearrangements causing these differences, we constructed a dense linkage map for Atlantic salmon of North American origin and compared it with the well-developed map for European Atlantic salmon. Results The presented male and female genetic maps for the North American subspecies of Atlantic salmon, contains 3,662 SNPs located on 27 linkage groups. The total lengths of the female and male linkage maps were 2,153 cM and 968 cM respectively, with males characteristically showing recombination only at the telomeres. We compared these maps with recently published SNP maps from European Atlantic salmon, and predicted three chromosomal reorganization events that we then tested using fluorescence in situ hybridization (FISH) analysis. The proposed rearrangements, which define the differences in the karyotypes of the North American Atlantic salmon relative to the European Atlantic salmon, include the translocation of the p arm of ssa01 to ssa23 and polymorphic fusions: ssa26 with ssa28, and ssa08 with ssa29. Conclusions This study identified major chromosomal differences between European and North American Atlantic salmon. However, while gross structural differences were significant, the order of genetic markers at the fine-resolution scale was remarkably conserved. This is a good indication that information from the International Cooperation to Sequence the Atlantic salmon Genome, which is sequencing a European Atlantic salmon, can be transferred to Atlantic salmon from North America. PMID:22928605

  10. Species Profiles. Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (North Atlantic). American Shad.

    DTIC Science & Technology

    1986-07-01

    overfishing . The 2865,49 2,092 Atlantic coast catches are greatest in 1929 13,95209 Chesapeake Bay (Table 7). 1930 10,373 Present Fishery 1931 11,336...rostrata), and birds. At sea, adult water teeperatures of 12 to 18 °C, or shad fall prey to seals, sharks, 54 to 64 OF (Leggett and Whitney bluefin ... tuna (Thunnus thynnus), 1972). Leim (1924) claimed that kingfish (Scomberomorus regalS), and American shad eggs hatch in 12 to 15 porpoises (Scott and

  11. Integrated mercury monitoring program for temperate estuarine and marine ecosystems on the North American Atlantic coast.

    PubMed

    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

    2008-12-01

    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 U.S. 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.

  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. New evidence for geologically instantaneous emplacement of earliest Jurassic Central Atlantic magmatic province basalts on the North American margin

    NASA Astrophysics Data System (ADS)

    Hames, W. E.; Renne, P. R.; Ruppel, C.

    2000-09-01

    Dikes in the southeastern United States represent a major component of the Central Atlantic magmatic province and record kinematics of Pangean breakup near the critical, predrift junction of three major continental masses. Until now, the age of these dikes had not been determined with the same precision as those of Central Atlantic magmatic province basalts on other parts of the circum-Atlantic margin. Our new results for three dike samples from the South Carolina Piedmont yield plateau ages of 198.8 ± 2.2, 199.5 ± 1.8, and 199.7 ± 1.5 Ma. For comparison, we present new age determinations of the benchmark Watchung flows I and III of the Newark basin: 201.0 ± 2.1 and 198.8 ± 2.0 Ma, respectively. Collectively, these data suggest that basaltic volcanism responsible for the dikes, flows, and sills of eastern North America occurred within ˜1 m.y. of 200 Ma. The timing, brief duration, and extent of the Central Atlantic magmatism imply that it may have been causally related to Triassic-Jurassic mass extinctions. The distribution and timing of this magmatism and the absence of regional uplift or an identifiable hotspot track lead us to favor strong lithospheric control on the origin of the Central Atlantic magmatic province, consistent with the modern generation of plume incubation or edge-driven convection models.

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

    PubMed

    Kurath, G; Winton, J R; Dale, O B; Purcell, M K; Falk, K; Busch, R A

    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.

  1. 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.

  2. 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.

  3. 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...

  4. 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

  5. 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

  6. Conservation genomics of anadromous Atlantic salmon across its North American range: outlier loci identify the same patterns of population structure as neutral loci.

    PubMed

    Moore, Jean-Sébastien; Bourret, Vincent; Dionne, Mélanie; Bradbury, Ian; O'Reilly, Patrick; Kent, Matthew; Chaput, Gérald; Bernatchez, Louis

    2014-12-01

    Anadromous Atlantic salmon (Salmo salar) is a species of major conservation and management concern in North America, where population abundance has been declining over the past 30 years. Effective conservation actions require the delineation of conservation units to appropriately reflect the spatial scale of intraspecific variation and local adaptation. Towards this goal, we used the most comprehensive genetic and genomic database for Atlantic salmon to date, covering the entire North American range of the species. The database included microsatellite data from 9142 individuals from 149 sampling locations and data from a medium-density SNP array providing genotypes for >3000 SNPs for 50 sampling locations. We used neutral and putatively selected loci to integrate adaptive information in the definition of conservation units. Bayesian clustering with the microsatellite data set and with neutral SNPs identified regional groupings largely consistent with previously published regional assessments. The use of outlier SNPs did not result in major differences in the regional groupings, suggesting that neutral markers can reflect the geographic scale of local adaptation despite not being under selection. We also performed assignment tests to compare power obtained from microsatellites, neutral SNPs and outlier SNPs. Using SNP data substantially improved power compared to microsatellites, and an assignment success of 97% to the population of origin and of 100% to the region of origin was achieved when all SNP loci were used. Using outlier SNPs only resulted in minor improvements to assignment success to the population of origin but improved regional assignment. We discuss the implications of these new genetic resources for the conservation and management of Atlantic salmon in North America.

  7. North Atlantic Nordic Seas exchanges

    NASA Astrophysics Data System (ADS)

    Hansen, B.; Østerhus, S.

    2000-02-01

    The northeastern part of the North Atlantic is unique in the sense that it is much warmer in the surface than other ocean areas at similar latitudes. The main reason for this is the large northward transport of heat that extends to high latitudes and crosses the Greenland-Scotland Ridge to enter the Nordic Seas and the Arctic. There the warm Atlantic water is converted to colder water masses that return southwards over the ridge partly as surface outflows and partly as overflows through the deep passages across the ridge. In this paper, the state of knowledge on the exchanges especially across the eastern part of the Greenland-Scotland Ridge is reviewed based on results from the ICES NANSEN (North Atlantic-Norwegian Sea Exchanges) project, from the Nordic WOCE project and from other sources. The accumulated evidence allows us to describe the exchanges in fair detail; the origins of the waters, the patterns of their flow towards and over the ridge and their ultimate fate. There is also increasing information on temporal variations of the exchanges although dynamical changes are still not well understood. Quantitative estimates for the volume transport of most of the overflow branches seem reasonably well established, and transport measurements of the Atlantic inflows to the Nordic Seas are approaching acceptable levels of confidence which allows preliminary budgets to be presented. The deep overflows are driven by pressure gradients set up by the formation of deep and intermediate water. The dominance of deep overflows over surface outflows in the water budget argues that this thermohaline forcing also dominates over direct wind stress and estuarine forcing in driving the Atlantic water inflow across the Greenland-Scotland Ridge, while wind stress seems to influence the characteristics and distribution of the Atlantic water north of the ridge.

  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. Perianal North American blastomycosis.

    PubMed

    Taub, Abigail L; Nelsen, David D; Nasser, Rana; Stratman, Erik J

    2015-08-01

    Cutaneous North American blastomycosis most often results from the hematogenous spread of Blastomyces dermatitidis following pulmonary infection. Cutaneous lesions, which may be either verrucous or ulcerative plaques, commonly occur on or around orifices contiguous to the respiratory tract. We report the case of a 57-year-old man with cutaneous North American blastomycosis who presented with a well-demarcated, firm, moist, verrucous perianal plaque 4 months following the onset of a prolonged upper respiratory tract infection. Dissemination of B dermatitidis to the perianal skin is rare, but North American blastomycosis should be considered in the broad differential diagnosis of perianal lesions in any patients who have lived in or traveled to endemic regions.

  10. 22 CFR 120.31 - North Atlantic Treaty Organization.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... DEFINITIONS § 120.31 North Atlantic Treaty Organization. North Atlantic Treaty Organization (NATO) is..., France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Lithuania, Luxembourg, The Netherlands,...

  11. 22 CFR 120.31 - North Atlantic Treaty Organization.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... DEFINITIONS § 120.31 North Atlantic Treaty Organization. North Atlantic Treaty Organization (NATO) is..., France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Lithuania, Luxembourg, The Netherlands,...

  12. Significant enhancements of nitrogen oxides, black carbon, and ozone in the North Atlantic lower free troposphere resulting from North American boreal wildfires

    NASA Astrophysics Data System (ADS)

    Val MartíN, M.; Honrath, R. E.; Owen, R. C.; Pfister, G.; Fialho, P.; Barata, F.

    2006-12-01

    Extensive wildfires burned in northern North America during summer 2004, releasing large amounts of trace gases and aerosols into the atmosphere. Emissions from these wildfires frequently impacted the PICO-NARE station, a mountaintop site situated 6-15 days downwind from the fires in the Azores Islands. To assess the impacts of the boreal wildfire emissions on the levels of aerosol black carbon (BC), nitrogen oxides and O3 downwind from North America, we analyzed measurements of CO, BC, total reactive nitrogen oxides (NOy), NOx (NO + NO2) and O3 made from June to September 2004 in combination with MOZART chemical transport model simulations. Long-range transport of boreal wildfire emissions resulted in large enhancements of CO, BC, NOy and NOx, with levels up to 250 ppbv, 665 ng m-3, 1100 pptv and 135 pptv, respectively. Enhancement ratios relative to CO were variable in the plumes sampled, most likely because of variations in wildfire emissions and removal processes during transport. Analyses of ΔBC/ΔCO, ΔNOy/ΔCO and ΔNOx/ΔCO ratios indicate that NOy and BC were on average efficiently exported in these plumes and suggest that decomposition of PAN to NOx was a significant source of NOx. High levels of NOx suggest continuing formation of O3 in these well-aged plumes. O3 levels were also significantly enhanced in the plumes, reaching up to 75 ppbv. Analysis of ΔO3/ΔCO ratios showed distinct behaviors of O3 in the plumes, which varied from significant to lower O3 production. We identify several potential reasons for the complex effects of boreal wildfire emissions on O3 and conclude that this behavior needs to be explored further in the future. These observations demonstrate that boreal wildfire emissions significantly contributed to the NOx and O3 budgets in the central North Atlantic lower free troposphere during summer 2004 and imply large-scale impacts on direct radiative forcing of the atmosphere and on tropospheric NOx and O3.

  13. Holocene Geomagnetic Change in the Northern North Atlantic

    NASA Astrophysics Data System (ADS)

    Stoner, J. S.; Channell, J. E.; Mazaud, A.; Xuan, C.; Strano, S. E.; Olafsdottir, S.; Jennings, A. E.

    2012-12-01

    High-resolution and well-dated paleomagnetic records constrain the geomagnetism of the Holocene North Atlantic. These records comprise ultra-high resolution sediment records from lakes (Haukadalsvatn, Iceland) and from continental margins (MD99-2269, N Iceland shelf; MD99-2322, E. Greenland), and from high accumulating (>50 cm/kyr) deep-sea sediments from the Eirik Drift, Labrador Sea (IODP Site U1305). Similarities among these directional paleomagnetic secular variation (PSV) records from very different environments imply that the records provide robust reconstructions of the paleo-geomagnetic field. Assuming that the age of magnetization is best defined by PSV in the highest sedimentation rate (>200 cm /kyr) records, allows us to place northern North Atlantic PSV and relative paleointensity (RPI) into a regional context. Northern North Atlantic PSV and RPI are more consistent with European than North American records, and the evolution of virtual geomagnetic poles (VGP) are temporally and longitudinally similar too global reconstructions, though with much larger latitudinal variations. The largest deviation from a geocentric axial dipole, in contrast to the usual assumption, is observed during times of highest field intensities in the North Atlantic and globally, while the highest rates of VGP change are associated with North Atlantic field intensity lows. These observations are consistent with the hypothesis that PSV results from temporal oscillations of flux concentrations (lobes) at a few recurrent locations.

  14. 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.

  15. Silver in the far North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Rivera-Duarte, I.; Flegal, A. R.; Sañudo-Wilhelmy, S. A.; Véron, A. J.

    Total (unfiltered) silver concentrations in higher latitudes of the North Atlantic (52-68°N) are reported for the second Intergovernmental Oceanographic Commission (IOC) Global Investigation of Pollutants in the Marine Environment (GIPME) baseline survey of 1993. These silver concentrations (0.69-7.2 pM) are oceanographically consistent with those (0.24-9.6 pM) previously reported for lower latitudes in the eastern North and South Atlantic ( Flegal et al., 1995). However, surface (⩽200 m) water concentrations of silver (0.69-4.6 pM) in the northern North Atlantic waters are, on average, ten-fold larger than those (0.25 pM) considered natural background concentrations in surface waters of the central Atlantic. In contrast, variations in deep far North Atlantic silver concentrations are associated with discrete water masses. Consequently, the cycling of silver in the far North Atlantic appears to be predominantly controlled by external inputs and the advection of distinct water masses, in contrast to the nutrient-like biogeochemical cycling of silver observed in the central Atlantic and Pacific oceans.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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)...

  2. 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)...

  3. 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)...

  4. 78 FR 61844 - North Atlantic Coast Comprehensive Study

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-04

    ... No: 2013-24237] DEPARTMENT OF DEFENSE Department of the Army; Corps of Engineers North Atlantic Coast... in the preparation of the North Atlantic Coast Comprehensive Study (Hurricane Sandy). The USACE is preparing a report that will be submitted to Congress in 2015. The goals of the North Atlantic...

  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. Diagnosing overflow waters in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Guo, Chuncheng; Ilicak, Mehmet; Bentsen, Mats; Fer, Ilker

    2015-04-01

    Danmark Strait overflow water (DSOW) and Iceland Faroe overflow water (ISOW) are important for the formation and transformation of deep waters in the North Atlantic. In this work the volume transport, variability, and pathways of DSOW and ISOW are diagnosed using the one degree ocean-ice coupled Norwegian Earth System Model (NorESM) that is forced by CORE2 inter-annual forcing. The oceanic component (MICOM) features an isopycnal coordinate that is referenced to 2000 db. The issues related to the coarse resolution such as the southward transport of ISOW to the western European Basin, the lack of overflow water in the western North Atlantic, and the western boundary detachment of the deep western boundary current are addressed. The effects of diapycnal mixing on the behavior of overflow descent at Denmark Strait and Faroe Bank Channel and its downstream evolution are examined.

  11. 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.

  12. 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.

  13. 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.

  14. Skilful predictions of the winter North Atlantic Oscillation one year ahead

    NASA Astrophysics Data System (ADS)

    Dunstone, Nick; Smith, Doug; Scaife, Adam; Hermanson, Leon; Eade, Rosie; Robinson, Niall; Andrews, Martin; Knight, Jeff

    2016-11-01

    The winter North Atlantic Oscillation is the primary mode of atmospheric variability in the North Atlantic region and has a profound influence on European and North American winter climate. Until recently, seasonal variability of the North Atlantic Oscillation was thought to be largely driven by chaotic and inherently unpredictable processes. However, latest generation seasonal forecasting systems have demonstrated significant skill in predicting the North Atlantic Oscillation when initialized a month before the onset of winter. Here we extend skilful dynamical model predictions to more than a year ahead. The skill increases greatly with ensemble size due to a spuriously small signal-to-noise ratio in the model, and consequently larger ensembles are projected to further increase the skill in predicting the North Atlantic Oscillation. We identify two sources of skill for second-winter forecasts of the North Atlantic Oscillation: climate variability in the tropical Pacific region and predictable effects of solar forcing on the stratospheric polar vortex strength. We also identify model biases in Arctic sea ice that, if reduced, may further increase skill. Our results open possibilities for a range of new climate services, including for the transport, energy, water management and insurance sectors.

  15. 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

  16. 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.

  17. 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.

  18. 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}).

  19. The North Atlantic subpolar gyre and the marine migration of Atlantic salmon Salmo salar: the 'Merry-Go-Round' hypothesis.

    PubMed

    Dadswell, M J; Spares, A D; Reader, J M; Stokesbury, M J W

    2010-08-01

    One model for marine migration of Atlantic salmon Salmo salar proposes that North American and southern European stocks (<62 degrees N) move directly to feeding grounds off west Greenland, then overwinter in the Labrador Sea, whereas northern European stocks (>62 degrees N) utilize the Norwegian Sea. An alternate model proposes that both North American and European stocks migrate in the North Atlantic Subpolar Gyre (NASpG) where S. salar enter the NASpG on their respective sides of the Atlantic, and travel counterclockwise within the NASpG until returning to natal rivers. A review of data accumulated during the last 50 years suggests a gyre model is most probable. Freshwater parr metamorphose into smolts which have morphological, physiological and behavioural adaptations of epipelagic, marine fishes. Former high-seas fisheries were seasonally sequential and moved in the direction of NASpG currents, and catches were highest along the main axis of the NASpG. Marking and discrimination studies indicate mixed continental origin feeding aggregations on both sides of the Atlantic. Marked North American smolts were captured off Norway, the Faroe Islands, east and west Greenland, and adults tagged at the Faroes were recovered in Canadian rivers. Marked European smolts were recovered off Newfoundland and Labrador, west and east Greenland, and adults tagged in the Labrador Sea were captured in European rivers. High Caesium-137 ((137)Cs) levels in S. salar returning to a Quebec river suggested 62.3% had fed at or east of Iceland, whereas levels in 1 sea-winter (SW) Atlantic Canada returnees indicated 24.7% had fed east of the Faroes. Lower levels of (137)Cs in returning 1SW Irish fish suggest much of their growth occurred in the western Atlantic. These data suggest marine migration of S. salar follows a gyre model and is similar to other open-ocean migrations of epipelagic fishes.

  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. 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... National Oceanic and Atmospheric Administration 50 CFR Part 635 RIN 0648-XV31 Atlantic Highly Migratory Species; North and South Atlantic Swordfish Quotas AGENCY: National Marine Fisheries Service...

  3. 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... National Oceanic and Atmospheric Administration 50 CFR Part 635 RIN 0648-XV31 Atlantic Highly Migratory Species; North and South Atlantic Swordfish Quotas AGENCY: National Marine Fisheries Service...

  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 Central

    Wirth, Thierry; Bernatchez, Louis

    2003-01-01

    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. PMID:12713741

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

    PubMed

    Wirth, Thierry; Bernatchez, Louis

    2003-04-07

    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.

  7. An overview of the North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

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

    The North Atlantic Oscillation (NAO) is one of the most prominent and recurrent patterns of atmospheric circulation variability. It dictates climate variability from the eastern seaboard of the United States to Siberia and from the Arctic to the subtropical Atlantic, especially during boreal winter, so variations in the NAO are important to society and for the environment. Understanding the processes that govern this variability is, therefore, of high priority, especially in the context of global climate change. This review, aimed at a scientifically diverse audience, provides general background material for the other chapters in the monograph, and it synthesizes some of their central points. It begins with a description of the spatial structure of climate and climate variability, including how the NAO relates to other prominent patterns of atmospheric circulation variability. There is no unique way to define the spatial structure of the NAO, or thus its temporal evolution, but several common approaches are illustrated. The relationship between the NAO and variations in surface temperature, storms and precipitation, and thus the economy, as well as the ocean and ecosystem responses to NAO variability, are described. Although the NAO is a mode of variability internal to the atmosphere, indices of it exhibit decadal variability and trends. That not all of its variability can be attributed to intraseasonal stochastic atmospheric processes points to a role for external forcings and, perhaps, a small but useful amount of predictability. The surface, stratospheric and anthropogenic processes that may influence the phase and amplitude of the NAO are reviewed.

  8. Microwave responses of the western North Atlantic

    NASA Technical Reports Server (NTRS)

    Stacey, J. M.; Girard, M. A.

    1985-01-01

    Features and objects in the Western North Atlantic Ocean - the Eastern Seaboard of the United States - are observed from Earth orbit by passive microwaves. The intensities of their radiated flux signatures are measured and displayed in color as a microwave flux image. The features of flux emitting objects such as the course of the Gulf Stream and the occurrence of cold eddies near the Gulf Stream are identified by contoured patterns of relative flux intensities. The flux signatures of ships and their wakes are displayed and discussed. Metal data buoys and aircraft are detected. Signal to clutter ratios and probabilities of detection are computed from their measured irradiances. Theoretical models and the range equations that explain passive microwave detection using the irradiances of natural sources are summarized.

  9. North Atlantic Finite Element Ocean Modeling

    NASA Astrophysics Data System (ADS)

    Veluthedathekuzhiyil, Praveen

    This thesis presents a modified version of the Finite Element Ocean Model (FEOM) developed at Alfred Wegener Institute for Polar and Marine Research (AWI) for the North Atlantic Ocean. A reasonable North Atlantic Ocean simulation is obtained against the observational data sets in a Control simulation (CS) where the surface boundary conditions are relaxed to a climatology. The vertical mixing in the model was tuned to represent convection in the model, also the horizontal mixing and diffusion coefficients to represent the changes in the resolution of the model’s unstructured grid. In addition, the open boundaries in the model are treated with a sponge layer where tracers are relaxed to climatology. The model is then further modified to accept the atmospheric flux forcing at the surface boundary with an added net heat flux correction and freshwater forcing from major rivers that are flowing into the North Atlantic Ocean. The impact of this boundary condition on the simulation results is then analyzed and shows many improvements albeit the drift in tracer properties around the Gulf Stream region remains as that of the CS case. However a comparison of the vertical sections at Cape Desolation and Cape Farewell with the available observational data sets shows many improvements in this simulation compared to that of the CS case. But the freshwater content in the Labrador Sea interior shows a continued drift as that of the CS case with an improvement towards the 10th model year. A detailed analysis of the boundary currents around the Labrador Sea shows the weak offshore transport of freshwater from the West Greenland Current (WGC) as one of the causes. To further improve the model and reasonably represent the boundary currents and associated sub-grid scale eddies in the model, a modified sub-grid scale parameterization based on Gent and McWilliams, (1990) is adopted. The sensitivity of using various approaches in the thickness diffusion parameter ( Kgm) for this

  10. Dissipation effects in North Atlantic Ocean modeling

    NASA Astrophysics Data System (ADS)

    Dietrich, D. E.; Mehra, A.; Haney, R. L.; Bowman, M. J.; Tseng, Y. H.

    2004-03-01

    Numerical experiments varying lateral viscosity and diffusivity between 20 and 150 m2/s in a North Atlantic Ocean (NAO) model having 4th-order accurate numerics, in which the dense deep current system (DCS) from the northern seas and Arctic Ocean is simulated directly show that Gulf Stream (GS) separation is strongly affected by the dissipation of the DCS. This is true even though the separation is highly inertial with large Reynolds number for GS separation flow scales. We show that realistic NAO modeling requires less than 150 m2/s viscosity and diffusivity in order to maintain the DCS material current with enough intensity to get realistic GS separation near Cape Hatteras (CH). This also demands accurate, low dissipation numerics, because of the long transit time (1-10 years) of DCS material from its northern seas and Arctic Ocean source regions to the Cape Hatteras region and the small lateral and vertical scales of DCS.

  11. Waveform Tomography of the North Atlantic Region

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    The enormous volumes of newly available, broadband seismic data and the continuing development of waveform tomography techniques present us with an opportunity to resolve the structure of North Atlantic at a new level of detail. Dynamics of the North Atlantic Ridge and the Iceland Hotspot, evolution of the passive margins on both sides of the ocean, and the nature of the upper-mantle flow beneath the region are some of the important fundamental problems that we can make progress on using new, more detailed and accurate models of seismic structure and anisotropy within the lithosphere and underlying mantle. We assemble a very large waveform dataset including all publicly available data in the region, from both permanent and temporary seismic networks and experiments conducted in Northern and Western Europe, Iceland, Canada, USA, Greenland and Russia. The tomographic model is constrained by vertical-component waveform fits, computed using the Automated Multimode Inversion of surface, S and multiple S waves. Each seismogram fit provides a set of linear equations describing 1D average velocity perturbations with respect to a 3D reference velocity model within an approximate sensitivity region between the source and the receiver. The equations are then combined into a large linear system and jointly inverted for a model of shear- and compressional-wave speeds and azimuthal anisotropy within the lithosphere and underlying mantle. The isotropic-average shear speeds reflect the temperature and composition at depth, offering important new information on both regional- and basin-scale lithospheric structure and evolution. Azimuthal anisotropy provides evidence on the past and present deformation in the lithosphere and asthenosphere beneath the region, which can be interpreted together with other evidence from geological and geophysical data and recent plate kinematic models.

  12. North American Natural Gas Markets

    SciTech Connect

    Not Available

    1988-12-01

    This report sunnnarizes the 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. 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...

  14. Origin of Quasi-decadal North Atlantic Oscillation Variability

    NASA Astrophysics Data System (ADS)

    Reintges, Annika; Latif, Mojib; Park, Wonsun

    2015-04-01

    The North Atlantic Oscillation (NAO) is the leading mode of internal atmospheric variability in the North Atlantic sector. It depicts significant quasi-decadal variability that is well documented, but the underlying mechanism is still under discussion. Other quantities in the North Atlantic sector such as sea surface temperature (SST) exhibit variability on a similar timescale. Here we present results from a global climate model which simulates the quasi-decadal NAO and North Atlantic SST variability consistent with observations. The quasi-decadal NAO variability is suggested to originate from large-scale air-sea interactions, where the Atlantic Meridional Overturning Circulation (AMOC) basically sets the timescale. Wind-driven ocean circulation changes provide a fast positive feedback on North Atlantic SST through anomalous Ekman currents and the establishment of an "intergyre" gyre. A delayed negative feedback on SST is accomplished through surface heat flux-driven changes of the AMOC and associated heat transport. The results stress the importance of both wind-induced and thermohaline-induced changes in the ocean circulation for quasi-decadal climate variability in the North Atlantic sector.

  15. 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.

  16. 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

  17. Modeling with Data Assimilation in the North Atlantic (DAMEE)

    DTIC Science & Technology

    1997-09-30

    and various data assimilation techniques. Exploring and implementing the best data assimilation methods with coupled models would be the final step for accurate, efficient forecasts of the North Atlantic Basin.

  18. Invasion of the abyssal North Atlantic by modern anthropogenic lead

    NASA Astrophysics Data System (ADS)

    Alleman, L. Y.; Véron, A. J.; Church, T. M.; Flegal, A. R.; Hamelin, B.

    While anthropogenic emissions have dramatically elevated lead concentrations in the North Atlantic troposphere and surface waters by orders of magnitude above natural levels [Murozumi et al., 1969; Schaule and Patterson, 1983; Boyle et al., 1986], it has been assumed that the relatively low lead levels in North Atlantic abyssal waters are not yet contaminated [Schaule and Patterson, 1981; Flegal and Patterson, 1983]. That misperception is redressed by the following stable lead isotopic composition data which reveal the advective transport of industrial lead into those deep basin waters through the formation of North Atlantic Deep Water (NADW). Additionally, spatial gradients in the isotopic signatures of anthropogenic lead within the North Atlantic abyss appear to serve as transient tracers of contaminant penetration rates.

  19. North Atlantic Treaty Organization, the United States, and International Legitimacy

    DTIC Science & Technology

    2014-05-22

    8. 42Following the signing of the Treaty of Versailles in 1919, the Albanian State was created but with only one-half of the Albanian population...NORTH ATLANTIC TREATY ORGANIZATION, THE UNITED STATES, AND INTERNATIONAL LEGITIMACY A Monograph by MAJ Mark Van Gelder...North Atlantic Treaty Organization, The United States, and International Legitimacy 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT

  20. 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.

  1. Carbon disulfide measurements in the atmosphere of the western North Atlantic and the northwestern South Atlantic Oceans

    NASA Technical Reports Server (NTRS)

    Bandy, Alan R.; Thornton, Donald C.; Johnson, James E.

    1993-01-01

    Carbon disulfide (CS2) measurements were made over the western and equatorial North Atlantic Ocean and the northwestern and equatorial South Atlantic Ocean. Carbon disulfide was in the range 0.4-50 pptrv in the atmosphere of the western North Atlantic Ocean. Emissions from anthropogenic sources and wet lands were found to be important although anthropogenic sources were 4-6 times larger than biogenic sources. The flux of CS2 from eastern North America between 30 and 39 deg latitude was estimated to be 2 x 10(exp 8)g/yr or sulfur. The anthropogenic contribution was 1.8 x 10(exp 8)g/yr of sulfur whereas the contribution of marshes was 0.2 x 10(exp 8)g/yr of sulfur. Sources of CS2 at high latitudes in the northern hemisphere were comparatively weak. Carbon disulfide levels in the western South Atlantic Ocean between -5 and 1 deg latitude were in the range 0.2-6 pptrv. Most of the CS2 appeared to come from biomass burning in Africa. Carbon disulfide was much higher close to shore suggesting that the South American continent was a significant source although too few data were available to quantify it. On ferry lights from Wallops, Virginia to Natal, Brazil, CS2 levels at the ferry altitude of about 6 km averaged 1.2 pptrv. This background CS2 was adequate to account for all the carbonyl sulfide (OCS) in the atmosphere.

  2. 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.

  3. 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.

  4. "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.

  5. 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.

  6. 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)...

  7. Decadal predictions of the North Atlantic CO2 uptake

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

  8. 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

  9. The Relation between the North Atlantic Oscillation and SSTs in the North Atlantic Basin.

    NASA Astrophysics Data System (ADS)

    Wang, Weile; Anderson, Bruce T.; Kaufmann, Robert K.; Myneni, Ranga B.

    2004-12-01

    The authors use the notion of Granger causality to investigate the relationship between the North Atlantic Oscillation (NAO) index and the sea surface temperatures (SSTs) over the Northern Hemisphere. The Granger causality analysis ensures that any apparent oceanic influence upon the atmosphere (as measured by the NAO) is provided by the ocean and is not related to preexisting conditions within the NAO itself (and vice versa when looking at the atmospheric influence upon the ocean). Although this statistical technique does not imply physical forcing of one field on the other, it is generally more reliable compared to the simple lead/lagged correlation. Using this technique, the authors find that on seasonal time scales, the preceding NAO anomalies' influence on the wintertime SST field is rather restricted. Conversely, preceding SST anomalies have a statistically significant causal effect on the wintertime NAO. However, the causal relation between preceding SSTs and the wintertime NAO is limited to the Gulf Stream extension; in contrast to the canonical tripole SST pattern typically associated with the NAO, the authors do not find that SST anomalies in either the Greenland or subtropical regions have a significant causal effect on the NAO. These results suggest that the Gulf Stream SSTs have an important influence in initiating disturbances of the atmospheric circulation over the wintertime North Atlantic.


  10. 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

  11. 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.

  12. Spatial variability of the North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

    Magnusdottir, G.

    2012-04-01

    The North Atlantic Oscillation (NAO) is a seesaw in mass (or anticorrelation in pressure) between a northern center of action, located close to Iceland, and a southern center of action, located close to the Azores. It is assumed to have a fixed spatial structure during winter and an index of time variability is measured, the NAO index. However, it is well documented that there was a shift in location of the northern center of action of the NAO from the two decades 1958-1977 to the two decades of 1978-1997. In this talk we examine dynamical changes associated with the aforementioned shift in the northern center of action of the NAO. We then go on to examine variability in the location of both centers of action over a longer time period, or from 1871. The analysis results in two possible approaches to understanding the evolution of the NAO. First, we define an additional index (to the NAO index), the angle index, to describe decadal atmospheric variability in the region associated with spatial shifts in the centers of action of the NAO. The angle index measures the angle that the great circle connecting the two centers makes with the meridian running through the northern center. It gives supplemental information to the NAO index alone. In light of the slow movement of the NAO, one may need more than the one dominating climate pattern to describe low-frequency atmospheric variability in the region. However, it is conceptually attractive as well as economical to summarize atmospheric low-frequency variability by referring to one climate pattern, especially when one is examining interactions with other parts of the climate system such as sea-ice variability. As our second approach we are developing an alternative to the static EOF-based (or correlation based) definition of the NAO. Our work to develop a dynamic statistical model to characterize the evolution of the NAO will be briefly described.

  13. Variability and predictability of the North Atlantic wave climate

    NASA Astrophysics Data System (ADS)

    Woolf, D. K.; Challenor, P. G.; Cotton, P. D.

    2002-10-01

    Wave climate across the ocean basins can be described using satellite altimetry; here, we concentrate on the North Atlantic region. Waves in the North Atlantic are strongly seasonal and peak in the winter season. The northeastern sector of the Atlantic and adjoining shelf seas also exhibit exceptionally high interannual variability in the winter, with monthly average significant wave height varying by up to a factor of 2 from one year to the next. The strength and geographical distribution of variability is broadly consistent throughout the winter months (December-March). A large fraction of these wave height anomalies is associated with a single pattern of pressure anomalies that resembles the North Atlantic Oscillation (NAO). A predictor based on NAO dependence is "trained" from relatively recent satellite data and then tested against earlier satellite and in situ data. The predictor is successful in large areas of the North Atlantic, confirming a robust relationship between wave height anomalies and the NAO over the last few decades. A substantial rise (up to 0.6 m) in monthly mean wave heights on the northeastern Atlantic during the latter part of the twentieth century is attributable to changes in the NAO. Substantial residual anomalies in wave heights exist after the influence of the NAO has been subtracted; these are partly explained by a second pair of North Atlantic patterns in wave height anomalies and sea level pressure anomalies. This "East Atlantic" pattern is particularly influential in midwinter and affects the southern part of the northeastern sector (including the region of Seven Stones Light Vessel).

  14. 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.

  15. 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

  16. 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

    2016-06-03

    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.

  17. 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

  18. 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.

  19. 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

  20. Space Radar Image of North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This is a radar image showing surface features on the open ocean in the northeast Atlantic Ocean. There is no land mass in this image. The purple line in the lower left of the image is the stern wake of a ship. The ship creating the wake is the bright white spot on the middle, left side of the image. The ship's wake is about 28 kilometers (17 miles) long in this image and investigators believe that is because the ship may be discharging oil. The oil makes the wake last longer and causes it to stand out in this radar image. A fairly sharp boundary or front extends from the lower left to the upper right corner of the image and separates two distinct water masses that have different temperatures. The different water temperature affects the wind patterns on the ocean. In this image, the light green area depicts rougher water with more wind, while the purple area is calmer water with less wind. The dark patches are smooth areas of low wind, probably related to clouds along the front, and the bright green patches are likely due to ice crystals in the clouds that scatter the radar waves. The overall 'fuzzy' look of this image is caused by long ocean waves, also called swells. Ocean radar imagery allows the fine detail of ocean features and interactions to be seen, such as the wake, swell, ocean front and cloud effects, which can then be used to enhance the understanding of ocean dynamics on smaller and smaller scales. The image is centered at 42.8 degrees north latitude, 26.2 degrees west longitude and shows an area approximately 35 kilometers by 65 kilometers (22 by 40 miles). The colors in the image are assigned to different frequencies and polarizations of the radar as follows: red is L-band horizontally transmitted, horizontally received; green is C-band horizontally transmitted, horizontally received; blue is L-band vertically transmitted, vertically received. This image was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR

  1. 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.

  2. 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

  3. 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.

  4. 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...

  5. 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…

  6. Circulation and north atlantic deep water formation rates based on evolution of the cfc signal in the north atlantic ocean

    NASA Astrophysics Data System (ADS)

    Smethie, W.; Lebel, D.

    2003-04-01

    The first high quality CFC measurements in the North Atlantic were made in 1981 as part of the TTO program. The WOCE survey in 1996-1998 provided the first synoptic CFC survey of the entire North Atlantic, but CFC measurements were made throughout the North Atlantic on a non-synoptic basis prior to WOCE. The pre-WOCE and WOCE CFC data sets will be compared on a regional basis using maps of concentrations on neutral density surfaces, maps of CFC-11 inventories, and plots of CFCs verses potential temperature for the major components of NADW. Circulation patterns and time scales inferred from the CFC distributions will be presented. The CFC inventories reflect the formation rate of a given water mass and formation rates calculated from the CFC inventories will be presented and compared for pre-WOCE and WOCE data.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

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

    PubMed

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

    2015-07-20

    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 (δ(13)C) and oxygen (δ(18)O) isotope records from the Southeast Atlantic-a key region for monitoring the southern extent of NADW. Using these data, together with other δ(13)C and δ(18)O 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. Eight centuries of north atlantic ocean atmosphere variability

    PubMed

    Black; Peterson; Overpeck; Kaplan; Evans; Kashgarian

    1999-11-26

    Climate in the tropical North Atlantic is controlled largely by variations in the strength of the trade winds, the position of the Intertropical Convergence Zone, and sea surface temperatures. A high-resolution study of Caribbean sediments provides a subdecadally resolved record of tropical upwelling and trade wind variability spanning the past 825 years. These results confirm the importance of a decadal (12- to 13-year) mode of Atlantic variability believed to be driven by coupled tropical ocean-atmosphere dynamics. Although a well-defined interdecadal mode of variability does not appear to be characteristic of the tropical Atlantic, there is evidence that century-scale variability is substantial. The tropical Atlantic may also have been involved in a major shift in Northern Hemisphere climate variability that took place about 700 years ago.

  18. 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.)

  19. 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...

  20. 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.

  1. Phylogeography of a widespread North American migratory songbird (Setophaga ruticilla).

    PubMed

    Colbeck, Gabriel J; Gibbs, H Lisle; Marra, Peter P; Hobson, Keith; Webster, Michael S

    2008-01-01

    Genetic analyses for many widespread North American species have revealed significant east-west differentiation, indicating that many survived through the Pleistocene in 2 glacial refugia-1 in the eastern and 1 in the western part of the continent. It remains unclear, however, whether other areas may have served as important glacial refugia. Moreover, many such species exhibit widespread genetic similarity within eastern and western regions because of recent expansion from small refugial populations, making it difficult to evaluate current-day levels of gene flow. In this study, we used mitochondrial DNA (mtDNA) control region sequence and amplified fragment length polymorphism markers to survey genetic variation in a widespread migratory bird, the American redstart (Setophaga ruticilla). mtDNA analyses revealed a pattern that contrasts with that found for most other widespread species studied to date: most redstart populations across North America appear to have spread out from a single glacial refugium, possibly located in the southeastern United States, whereas populations in far-eastern Canada may have survived in a second glacial refugium located on the now-submerged Atlantic coastal shelf off the coast of Newfoundland. A pattern of isolation by distance in mtDNA suggested some constraints on current-day gene flow among extant redstart populations. This study thus reveals a recent evolutionary history for this species that differs from that of most other widespread North American passerines and provides evidence for limited gene flow in a species with potentially large dispersal distances.

  2. 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.

  3. Toxaphene in minke whales (Balaenoptera acutorostrata) from the North Atlantic.

    PubMed

    Gouteux, B; Muir, D C G; Backus, S; Born, E W; Dietz, R; Haug, T; Metcalfe, T; Metcalfe, C; Øien, N

    2008-05-01

    Toxaphene contamination of minke whales (Balaenoptera acutorostrata) from North Atlantic waters was examined for the first time. Total toxaphene and SigmaCHB (sum of 11 chlorobornanes) concentrations in blubber samples ranged from 170+/-110 and 41+/-39 ng/g lipid weight (l.w.) for female minke whales from southeastern Greenland to 5800+/-4100 and 1100+/-780 ng/g l.w. for males from the North Sea, respectively. Very large variations in toxaphene concentrations among sampling areas were observed suggesting a spatial segregation of minke whales. However, much of the apparent geographical discrimination was explained by the seasonal fluctuation of animal fat mass. Patterns of CHBs in males revealed that recalcitrant CHBs were in higher proportions in animals from the more easterly areas than in animals from the more westerly areas. This trend may be influenced by the predominance of the US, over the European, input of toxaphene to North Atlantic waters.

  4. 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

    ... measurement of 25 inches. This recommendation was adopted by ICCAT based on the most recent North Atlantic... lead to a lower available quota relative to the current adjusted quota. This lower level of adjusted... current adjusted quota of 4,406.4 mt dw. Therefore, this proposed action could result in annual...

  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

    ... Tunas (Commission) Recommendation 11-02, which maintains the U.S. North Atlantic swordfish base quota allocation, reduces the annual underharvest carryover from 50 to 25 percent of the base quota, establishes an... a CK minimum size measurement of 25 inches. The proposed rule (77 FR 25669, May 1, 2012) and...

  6. 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. 

  7. 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.

  8. 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

  9. The North Atlantic Oscillation: A dominant factor in variations of oceanic circulation systems of the Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Dvoryaninov, G. S.; Kubryakov, A. A.; Sizov, A. A.; Stanichny, S. V.; Shapiro, N. B.

    2016-01-01

    On the basis of altimetry data, the dynamics of the interaction between the subtropical anticyclonic (SA) and subpolar cyclonic (SC) gyres of the North Atlantic is considered. It is shown that the westerlies in the lower troposphere represented by the North Atlantic Oscillation (NAO) index are the main factor responsible for the dynamics of the gyres, which controls the inflow of warm Atlantic water into the Polar basin.

  10. 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.

  11. Annually resolved North Atlantic marine climate over the last millennium

    NASA Astrophysics Data System (ADS)

    Reynolds, D. J.; Scourse, J. D.; Halloran, P. R.; Nederbragt, A. J.; Wanamaker, A. D.; Butler, P. G.; Richardson, C. A.; Heinemeier, J.; Eiríksson, J.; Knudsen, K. L.; Hall, I. R.

    2016-12-01

    Owing to the lack of absolutely dated oceanographic information before the modern instrumental period, there is currently significant debate as to the role played by North Atlantic Ocean dynamics in previous climate transitions (for example, Medieval Climate Anomaly-Little Ice Age, MCA-LIA). Here we present analyses of a millennial-length, annually resolved and absolutely dated marine δ18O archive. We interpret our record of oxygen isotope ratios from the shells of the long-lived marine bivalve Arctica islandica (δ18O-shell), from the North Icelandic shelf, in relation to seawater density variability and demonstrate that solar and volcanic forcing coupled with ocean circulation dynamics are key drivers of climate variability over the last millennium. During the pre-industrial period (AD 1000-1800) variability in the sub-polar North Atlantic leads changes in Northern Hemisphere surface air temperatures at multi-decadal timescales, indicating that North Atlantic Ocean dynamics played an active role in modulating the response of the atmosphere to solar and volcanic forcing.

  12. Annually resolved North Atlantic marine climate over the last millennium

    PubMed Central

    Reynolds, D. J.; Scourse, J. D.; Halloran, P. R.; Nederbragt, A. J.; Wanamaker, A. D.; Butler, P. G.; Richardson, C. A.; Heinemeier, J.; Eiríksson, J.; Knudsen, K. L.; Hall, I. R.

    2016-01-01

    Owing to the lack of absolutely dated oceanographic information before the modern instrumental period, there is currently significant debate as to the role played by North Atlantic Ocean dynamics in previous climate transitions (for example, Medieval Climate Anomaly-Little Ice Age, MCA-LIA). Here we present analyses of a millennial-length, annually resolved and absolutely dated marine δ18O archive. We interpret our record of oxygen isotope ratios from the shells of the long-lived marine bivalve Arctica islandica (δ18O-shell), from the North Icelandic shelf, in relation to seawater density variability and demonstrate that solar and volcanic forcing coupled with ocean circulation dynamics are key drivers of climate variability over the last millennium. During the pre-industrial period (AD 1000–1800) variability in the sub-polar North Atlantic leads changes in Northern Hemisphere surface air temperatures at multi-decadal timescales, indicating that North Atlantic Ocean dynamics played an active role in modulating the response of the atmosphere to solar and volcanic forcing. PMID:27922004

  13. Eddy length scales in the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Eden, Carsten

    2007-06-01

    Eddy length scales are calculated from satellite altimeter products and in an eddy-resolving model of the North Atlantic Ocean. Four different measures for eddy length scales are derived from kinetic energy densities in wave number space and spatial decorrelation scales. Observational estimates and model simulation agree well in all these measures near the surface. As found in previous studies, all length scales are, in general, decreasing with latitude. They are isotropic and proportional to the local first baroclinic Rossby radius (Lr) north of about 30°N, while south of 30°N (or for Lr > 30 km), zonal length scales tend to be larger than meridional ones, and (scalar) length scales show no clear relation to Lr anymore. Instead, they appear to be related to the local Rhines scale. In agreement with a recent theoretical prediction by Theiss [2004], the observed and simulated pattern of eddy length scales appears to be indicative of two different dynamical regimes in the North Atlantic: anisotropic turbulence in the subtropics and isotropic turbulence in the subpolar North Atlantic. Both regions can be roughly characterized by the ration between Lr and the Rhines scales (LR), with LR > Lr in the isotropic region and LR < Lr in the anisotropic region. The critical latitude that separates both regions, i.e., where LR = Lr, is about 30°N.

  14. 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.

  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.

  16. 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

  17. North American Natural Gas Vision

    DTIC Science & Technology

    2005-01-01

    revamping research and development by increasing the movement of technologies like solar , wind, and geothermal energy to the market, while...compete directly with PGPB pipelines. However, they help to eliminate bottlenecks in the PGPB system. The Energia Mayakan pipeline is the most...Energy Outlook (U.S.EIA) AGA American Gas Association Bcf Billion cubic feet CBM Coalbed methane CRE Comisión Regulatoria de Energia

  18. 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

  19. Oxygen dynamics in the North Atlantic subtropical gyre

    NASA Astrophysics Data System (ADS)

    Cianca, A.; Santana, R.; Hartman, S. E.; Martín-González, J. M.; González-Dávila, M.; Rueda, M. J.; Llinás, O.; Neuer, S.

    2013-09-01

    Dissolved oxygen (DO) in the ocean is a tracer for most ocean biogeochemical processes including net community production and remineralization of organic matter which in turn constrains the biological carbon pump. Knowledge of oxygen dynamics in the North Atlantic Ocean is mainly derived from observations at the Bermuda Atlantic Time-series Study (BATS) site located in the western subtropical gyre which may skew our view of the biogeochemistry of the subtropical North Atlantic. This study presents and compares a 15 yr record of DO observations from ESTOC (European Station for Time-Series in the Ocean, Canary Islands) in the eastern subtropical North Atlantic with the 20 yr record at BATS. Our estimate for net community production of oxygen was 2.3±0.4 mol O2 m-2 yr-1 and of oxygen consumption was -2.3±0.5 mol O2 m-2 yr-1 at ESTOC, and 4 mol O2 m-2 yr-1 and -4.4±1 mol m-2 yr-1 at BATS, respectively. These values were determined by analyzing the time-series using the Discrete Wavelet Transform (DWT) method. These flux values agree with similar estimates from in-situ observational studies but are higher than those from modeling studies. The difference in net oxygen production rates supports previous observations of a lower carbon export in the eastern compared to the western subtropical Atlantic. The inter-annual analysis showed clear annual cycles at BATS whereas longer cycles of nearly 4 years were apparent at ESTOC. The DWT analysis showed trends in DO anomalies dominated by long-term perturbations at a basin scale for the consumption zones at both sites, whereas yearly cycles dominated the production zone at BATS. The long-term perturbations found are likely associated with ventilation of the main thermocline, affecting the consumption and production zones at ESTOC.

  20. 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…

  1. 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…

  2. 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,…

  3. 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…

  4. 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…

  5. The North American Indian and the Eskimo.

    ERIC Educational Resources Information Center

    San Francisco Unified School District, CA.

    This is a selected bibliography of some good and some outstanding audio-visual educational materials in the library of the Educational Materials Bureau, Audio-Visual Education Section, that may be considered of particular interest in the study of the North American Indian, the Eskimo, and in the fields of ethnology and anthropology. The…

  6. An Assessment of North American Nursing.

    ERIC Educational Resources Information Center

    Commission on Graduates of Foreign Nursing Schools, Philadelphia, PA.

    This document, prepared under the auspices of the Trilateral Initiative for North American Nursing, a professional organization of nursing, examines and compares nursing standards in Canada, Mexico, and the United States. The report focuses on first-level, general nurses and advanced or specialty practice nurses, and is organized in four parts:…

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

    PubMed

    Straneo, Fiammetta; Heimbach, Patrick

    2013-12-05

    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.

  8. Synchronous climate changes in antarctica and the north atlantic

    PubMed

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

    1998-10-02

    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.

  9. 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.

  10. 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.

  11. Constraining Mid Pliocene North Atlantic Warming Using a Multiproxy Approach

    NASA Astrophysics Data System (ADS)

    Dowsett, H.; Robinson, M.; Dwyer, G.; Cronin, T.; Chandler, M.

    2005-12-01

    Relatively high sea surface temperature during the mid Pliocene (~3.0 Ma) has been documented in many oceanic regions. Constraining the magnitude, variability, and regional extent of warming is critical for modeling experiments being undertaken based upon reconstruction of mid Pliocene conditions. A comprehensive re-evaluation of the mid Pliocene of the North Atlantic region using a multiproxy approach that includes quantitative planktic foraminifer analysis, and Mg:Ca paleothermometry on Neogloboquadrina pachyderma and Globigerina bulloides yields new insights into conditions occurring 3 million years ago. While the overall pattern of warming documented by the PRISM (Pliocene Research, Interpretation, and Synoptic Mapping) Project remains unchanged, mean regional warming in the North Atlantic may have been underestimated in earlier reconstructions. Model simulations using maximum and minimum probable SST reconstructions provide a more useful measure of the spatial variability of mid-Pliocene warmth and should produce more realistic model simulations.

  12. 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.

  13. 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.

  14. Marine biogeochemical responses to the North Atlantic Oscillation in a coupled climate model

    NASA Astrophysics Data System (ADS)

    Patara, Lavinia; Visbeck, Martin; Masina, Simona; Krahmann, Gerd; Vichi, Marcello

    2011-07-01

    In this study a coupled ocean-atmosphere model containing interactive marine biogeochemistry is used to analyze interannual, lagged, and decadal marine biogeochemical responses to the North Atlantic Oscillation (NAO), the dominant mode of North Atlantic atmospheric variability. The coupled model adequately reproduces present-day climatologies and NAO atmospheric variability. It is shown that marine biogeochemical responses to the NAO are governed by different mechanisms according to the time scale considered. On interannual time scales, local changes in vertical mixing, caused by modifications in air-sea heat, freshwater, and momentum fluxes, are most relevant in influencing phytoplankton growth through light and nutrient limitation mechanisms. At subpolar latitudes, deeper mixing occurring during positive NAO winters causes a slight decrease in late winter chlorophyll concentration due to light limitation and a 10%-20% increase in spring chlorophyll concentration due to higher nutrient availability. The lagged response of physical and biogeochemical properties to a high NAO winter shows some memory in the following 2 years. In particular, subsurface nutrient anomalies generated by local changes in mixing near the American coast are advected along the North Atlantic Current, where they are suggested to affect downstream chlorophyll concentration with 1 year lag. On decadal time scales, local and remote mechanisms act contemporaneously in shaping the decadal biogeochemical response to the NAO. The slow circulation adjustment, in response to NAO wind stress curl anomalies, causes a basin redistribution of heat, freshwater, and biogeochemical properties which, in turn, modifies the spatial structure of the subpolar chlorophyll bloom.

  15. Wave speed structure of the eastern North American margin

    NASA Astrophysics Data System (ADS)

    Savage, B.; Covellone, B. M.; Shen, Y.

    2017-02-01

    The eastern North American margin (ENAM) is the result of nearly a billion years of continental collision and rifting. To the west of this margin lies thick continental lithosphere of the North American craton, and to the east is oceanic lithosphere in the Atlantic. The substantial changes in lithosphere thickness at this boundary are thought to drive asthenosphere upwelling along the edge of the continent. Through iterative, full-waveform, ambient noise tomography, we observe a heterogeneous low wave speed margin along the continent in the upper mantle. Multiple low wave speed features imaged within the margin are consistent with asthenospeheric upwelling due to edge-driven convection. Also within the margin are high wave speed anomalies that maybe the remnants of eclogitic delamination of the Appalachian crustal root, which contribute to convection at the margin. Edge driven, small-scale convection keeps the margin weak and thus controls the large scale plate tectonic patterns and the crustal deformation. The imaged mantle wave speed anomalies, interpreted as edge-driven convection, correlate with and may increase the likelihood of damaging earthquakes in the eastern portion of North America.

  16. Meridional Circulation in the Tropical North Atlantic

    DTIC Science & Technology

    1993-01-01

    nominally located at 1 I°N was carried out in March 1989. In this paper relative geostrophic velocities are computed from these data via the thermal wind...from these analysis techniques is presented, and indicates a North Brazil Current transport of nearly 12 Sv. Transports of the shallow waters are found...Schematic circulation patterns of the NADW and AABW are also presented. The deep waters of the western basin are dominated by a cyclonic recirculation

  17. 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... Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA) grant proposals for recommendation to the Migratory Bird Conservation Commission (Commission). This meeting...

  18. 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... Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA) grant proposals for recommendation to the Migratory Bird Conservation Commission (Commission). This meeting...

  19. 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... Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA) grant proposals for recommendation to the Migratory Bird Conservation Commission (Commission). This meeting...

  20. 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... Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA) grant proposals for recommendation to the Migratory Bird Conservation Commission (Commission). This meeting...

  1. 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... Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA) grant proposals for recommendation to the Migratory Bird Conservation Commission (Commission). This meeting...

  2. 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... Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA) grant proposals for recommendation to the Migratory Bird Conservation Commission (Commission). This meeting...

  3. North American Society for Pediatric and Adolescent Gynecology

    MedlinePlus

    ... removeClass('notactive'); autoPlay();}); }); About NASPAG The North American Society for Pediatric and Adolescent Gynecology (NASPAG), founded in ... Bayer/NASPAG Young Investigator Grant The North American Society for Pediatric and Adolescent Gynecology (NASPAG) has partnered ...

  4. Intercontinental transport of tropospheric ozone: A study of its seasonal variability across the North Atlantic utilizing tropospheric ozone residuals and its relationship to the North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

    Creilson, J. K.; Fishman, J.; Wozniak, A. E.

    2003-08-01

    Using the empirically-corrected tropospheric ozone residual (TOR) technique, which utilizes coincident observations of total ozone from the Total Ozone Mapping Spectrometer (TOMS) and stratospheric ozone profiles from the Solar Backscattered Ultraviolet (SBUV) instruments, the seasonal and regional distribution of tropospheric ozone across the North Atlantic from 1979-2000 is examined. Its relationship to the North Atlantic Oscillation (NAO) is also analyzed as a possible transport mechanism across the North Atlantic. Monthly climatologies of tropospheric ozone for five different regions across the North Atlantic exhibit strong seasonality. The correlation between these monthly climatologies of the TOR and adjacent ozonesonde profiles in both Region 1 (eastern North America-western North Atlantic) and Region 5 (eastern North Atlantic-western Europe) are highly significant (R values of +0.98 and +0.96, respectively) and help to validate the use of satellite retrievals of tropospheric ozone. Distinct springtime interannual variability over North Atlantic Region 5 (eastern North Atlantic-western Europe) is particularly evident and exhibits similar variability to the positive phase of the NAO (R=+0.61, ρ =<0.01). Positive phases of the NAO are indicative of a stronger Bermuda-Azores high and a stronger Icelandic low and thus faster more zonal flow across the North Atlantic from west to east. This flow regime appears to be causing the transport of tropospheric ozone across the North Atlantic and onto Europe. The consequence of such transport is the impact on a downwind region's ability to meet their ozone attainment goals. This link between the positive phase of the NAO and increased tropospheric ozone over Region 5 could be an important tool for prediction of such pollution outbreaks.

  5. 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.

  6. The Biological Carbon Pump in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Sanders, Richard; Henson, Stephanie A.; Koski, Marja; De La Rocha, Christina L.; Painter, Stuart C.; Poulton, Alex J.; Riley, Jennifer; Salihoglu, Baris; Visser, Andre; Yool, Andrew; Bellerby, Richard; Martin, Adrian P.

    2014-12-01

    Mediated principally by the sinking of organic rich particles from the upper ocean, the Biological Carbon Pump (BCP) is a significant component of the global carbon cycle. It transfers roughly 11 Gt C yr-1 into the ocean's interior and maintains atmospheric carbon dioxide at significantly lower levels than would be the case if it did not exist. More specifically, export by the BCP in the North Atlantic is ∼0.55-1.94 Gt C yr-1. A rich set of observations suggests that a complex set of processes drives this export. However, significant uncertainties exist regarding the BCP in the North Atlantic, including both the magnitude of the downward flux and the ecological, chemical and physical processes by which it is sustained and controlled. Our lack of detailed mechanistic understanding has also hindered modelling attempts to quantify and predict changes to the BCP. In this paper, we assess current knowledge concerning the BCP in the North Atlantic in order to identify priorities for future research, as well as suggesting how they might be addressed.

  7. 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.

  8. 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.

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

    PubMed

    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.

  10. 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

  11. 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.

  12. Unstable Air-Sea Interaction in the Extratropical North Atlantic

    NASA Technical Reports Server (NTRS)

    Hakkinen, Sirpa

    1999-01-01

    The possibility of coupled modes in the extratropical North Atlantic has fascinated the climate community since 1960's. A significant aspect of such modes is an unstable air-sea interaction, also called positive feedback, where disturbances between the atmosphere and ocean grow unbound. If a delayed response exists before the negative feedback takes effect, an oscillatory behaviour will develop. Here we explore the relationship between heat flux (positive upward) and sea surface temperature (SST). Positive feedback is characterized by a cross-correlation between the two where correlation maintains a negative sign whether SST or heat flux leads. We use model results and observations to argue that in the North Atlantic there exist regions with positive feedback. The two main locations coincide with the well-known north-south SST dipole where anomalies of opposite sign occupy areas east of Florida and north-east of Newfoundland. We show that oceanic dynamics, wave propagation and advection, give rise to oceanic anomalies in these regions. Subsequently these anomalies are amplified by atmosphere- ocean interaction: thus a positive feedback.

  13. Late Holocene climate reorganisation and the North American Monsoon

    NASA Astrophysics Data System (ADS)

    Jones, Matthew D.; Metcalfe, Sarah E.; Davies, Sarah J.; Noren, Anders

    2015-09-01

    The North American Monsoon (NAM) provides the majority of rainfall for central and northern Mexico as well as parts of the south west USA. The controls over the strength of the NAM in a given year are complex, and include both Pacific and Atlantic systems. We present here an annually resolved proxy reconstruction of NAM rainfall variability over the last ˜6 ka, from an inwash record from the Laguna de Juanacatlán, Mexico. This high resolution, exceptionally well dated record allows changes in the NAM through the latter half of the Holocene to be investigated in both time and space domains, improving our understanding of the controls on the system. Our analysis shows a shift in conditions between c. 4 and 3 ka BP, after which clear ENSO/PDO type forcing patterns are evident.

  14. 46 CFR 42.30-35 - The Winter North Atlantic Load Line.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 2 2014-10-01 2014-10-01 false The Winter North Atlantic Load Line. 42.30-35 Section 42... FOREIGN VOYAGES BY SEA Zones, Areas, and Seasonal Periods § 42.30-35 The Winter North Atlantic Load Line. (a) The part of the North Atlantic referred to in § 42.20-75(d)(1) comprises: (1) That part of...

  15. 46 CFR 42.30-35 - The Winter North Atlantic Load Line.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 2 2013-10-01 2013-10-01 false The Winter North Atlantic Load Line. 42.30-35 Section 42... FOREIGN VOYAGES BY SEA Zones, Areas, and Seasonal Periods § 42.30-35 The Winter North Atlantic Load Line. (a) The part of the North Atlantic referred to in § 42.20-75(d)(1) comprises: (1) That part of...

  16. 46 CFR 42.30-35 - The Winter North Atlantic Load Line.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 2 2012-10-01 2012-10-01 false The Winter North Atlantic Load Line. 42.30-35 Section 42... FOREIGN VOYAGES BY SEA Zones, Areas, and Seasonal Periods § 42.30-35 The Winter North Atlantic Load Line. (a) The part of the North Atlantic referred to in § 42.20-75(d)(1) comprises: (1) That part of...

  17. 46 CFR 42.30-35 - The Winter North Atlantic Load Line.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false The Winter North Atlantic Load Line. 42.30-35 Section 42... FOREIGN VOYAGES BY SEA Zones, Areas, and Seasonal Periods § 42.30-35 The Winter North Atlantic Load Line. (a) The part of the North Atlantic referred to in § 42.20-75(d)(1) comprises: (1) That part of...

  18. 46 CFR 42.30-35 - The Winter North Atlantic Load Line.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 2 2011-10-01 2011-10-01 false The Winter North Atlantic Load Line. 42.30-35 Section 42... FOREIGN VOYAGES BY SEA Zones, Areas, and Seasonal Periods § 42.30-35 The Winter North Atlantic Load Line. (a) The part of the North Atlantic referred to in § 42.20-75(d)(1) comprises: (1) That part of...

  19. Measuring currents between North Atlantic and Nordic seas

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2012-06-01

    The fluxes of water from the North Atlantic to the Nordic seas provide a measure of the water that flows into and out of the global ocean as part of the meridional overturning circulation. The meridional overturning circulation, which carries warm water in the Atlantic from the tropics northward and brings cold dense water back southward, is a key part of global ocean circulation and a strong influence on climate; some research has suggested that the meridional overturning circulation could slow down as the global climate warms. Using an acoustic Doppler current profiler mounted in the high seas ferry Norröna to repeatedly measure the currents in the Faroe-Shetland Channel and over the Iceland-Faroe Ridge, Rossby and Flagg report on 3 years of weekly measurements that provide a new, accurate measure of the exchange of water between the North Atlantic and Nordic seas. The observations will be useful in understanding the meridional overturning circulation. (Geophysical Research Letters, doi:10.1029/2012GL051269, 2012)

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

    PubMed

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

    2006-10-05

    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.

  1. Remote impact of North Atlantic sea surface temperature on rainfall in southwestern China during boreal spring

    NASA Astrophysics Data System (ADS)

    Li, Gang; Chen, Jiepeng; Wang, Xin; Luo, Xia; Yang, Daoyong; Zhou, Wen; Tan, Yanke; Yan, Hongming

    2017-03-01

    As an important oceanic signal, the North Atlantic sea surface temperature (SST) affects not only the climate variability over East China and Northeast China but also can affect climate variability over southwestern China (SWC). Based on station rainfall data and reanalysis datasets, the present study investigates the relationship of North Atlantic SST with SWC rainfall during boreal spring for the period 1979-2016. The results show that there is a significant positive correlation between North Atlantic SST and SWC rainfall during boreal spring. The atmospheric circulation over southern Asia associated with North Atlantic SST is favorable for positive rainfall anomalies. Further analyses show that North Atlantic SST can induce a North Atlantic-western Russia-western Tibetan Plateau-SWC (NRTC) teleconnection wave train from upper level to low level. At low level, two anomalous anticyclones are found over the mid-high latitude of North Atlantic and the western Tibetan Plateau, and two anomalous cyclones are observed over the western Russia and Bay of Bengal (BOB), respectively. The NRTC teleconnection wave train plays a bridging role between the North Atlantic SST and SWC rainfall during boreal spring. Both the observational analysis and two numerical experiments suggest that the North Atlantic SST during boreal spring can induce an anomalous cyclone over BOB by the NRTC teleconnection pattern. The anomalous cyclone over BOB favors moisture transport to SWC, accompanying with significant anomalous ascending motion, and thus results in positive rainfall anomalies in SWC during boreal spring.

  2. Weather and Climate Prediction for the North American Monsoon

    NASA Astrophysics Data System (ADS)

    Krishnamurti, T. N.; Chakraborty, A.

    2005-05-01

    Some of the major elements of the North American monsoon include the onset and seasonal behavior of precipitation, the moisture sources, orographic responses, effects of sea surface temperature (SST) anomalies over the Gulf of Mexico, Pacific and Atlantic Oceans, and the teleconnection with the intertropical convergence zone (ITCZ). This study addresses these issues on the medium range (a week) to seasonal (3 month) time scales. Our approach is one of constructing ensemble forecasts that include 11 weather models for the medium range and 13 coupled atmosphere-ocean models for seasonal time scales. The metrics for forecasts evaluation include deterministic measures such as RMS error and anomaly correlation, and probabilistic measures such as the equitable threat scores and Briar skill scores. The ensemble forecast approach includes a conventional FSU superensemble for weather and a variant called the synthetic superensemble for the seasonal climate. These superensemble strings covering a 13-year period show that it is possible to predict some of the important features of the North American monsoon at a higher skill with the superensemble compared to the participating member models.

  3. 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.

  4. Understanding and predicting changes in North Atlantic Sea Surface Temperature

    NASA Astrophysics Data System (ADS)

    Yeager, S. G.

    The mechanisms associated with sea surface temperature variability in the North Atlantic are explored using observation-based reconstructions of the historical surface states of the atmosphere and ocean as well as simulations run with the Community Earth System Model, version 1 (CESM1). The relationship between air-sea heat flux and SST between 1948 and 2009 yields evidence of a positive heat flux feedback at work in the subpolar gyre region on quasi-decadal timescales. Warming of the high latitude Atlantic precedes an atmospheric response which resembles a negative NAO state. The historical flux data set is used to estimate temporal variations in North Atlantic deep water formation which suggest that NAO variations drove strong decadal changes in thermohaline circulation strength in the last half century. Model simulations corroborate the observation-based inferences that substantial changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC) ensued as a result of NAO-driven water mass perturbations, and that changes in the large-scale ocean circulation played a significant role in modulating North Atlantic SST. Surface forcing perturbation experiments show that the simulated low-frequency AMOC variability is mainly driven by turbulent buoyancy forcing over the Labrador Sea region, and that the decadal ocean variability, in uncoupled experiments, derives from low-frequency variability in the overlying atmospheric state. Surface momentum forcing accounts for most of the interannual variability in AMOC at all latitudes, and also most of the decadal AMOC variability south of the Equator. We show that the latter relates to the trend in wind stress forcing of the Southern Ocean, but that Southern Ocean forcing explains very little of the North Atlantic signal. The sea surface height in the Labrador Sea is identified as a strongly buoyancy-forced observable which supports its use as a monitor of AMOC strength. The dynamics which characterize the

  5. 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

  6. Tritium distributions in an isopycnic model of the North Atlantic

    NASA Astrophysics Data System (ADS)

    Jia, Yanli; Richards, Kelvin J.

    1996-05-01

    An ocean general circulation model with an isopycnic coordinate in the vertical is used to simulate the North Atlantic circulation. Tritium and helium are injected into the model after an initial spin-up phase to assist our understanding of the model response and to validate the model itself by comparing the model data with available tracer observations. In this paper, the distribution of tritium is presented and compared with observations in 1972 (Geochemical Ocean Sections Study) and 1981 (Transient Tracers in the Ocean (TTO)). The vertical penetration of tritium in the model compares well with observations, reflecting the ventilation patterns in the subtropical and subpolar gyres and the deep overflows from the Greenland and Norwegian basin through the Denmark Strait and across the Iceland-Faeroes rise. However, the distributions of tritium on various isopycnic layers do show discrepancies with observations, and the magnitude of tritium concentration is too high in the model. It is found that the model produces a pronounced maximum tritium concentration in the interior of the North Atlantic subtropical gyre in 1972, which is not observed. The presence of this maximum suggests that the ratio of diffusion to advection timescales (the Péclet number) is too high in the model. A simple two-dimensional advection-diffusion model is used to explore the relationships between the distributions of tritium and the timescales of advection and diffusion processes. These experiments suggest an upper bound on the Péclet number. A further experiment using the Atlantic isopycnic model with a decreased Péclet number shows some improvement to the distribution of tritium on the isopycnic layers. Comparisons of tritium-helium age in 1981 between the model results and TTO data show that the model has a too rapid circulation. The lack of mixing by eddies in the model is also believed to be partially responsible for the discrepancies between the modeled tritium distributions and the

  7. 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.

  8. 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.

  9. The North Atlantic Tritium and Radiocarbon Transients 1972-1983

    NASA Astrophysics Data System (ADS)

    Göte Östlund, H.; Rooth, Claes G. H.

    1990-11-01

    Deep ventilation and water mass transformation processes in the North Atlantic, on decadal time scales, are illustrated by the evolving distribution patterns of anthropogenic tritium and radiocarbon. Data from two quasisynoptic surveys of the interior of the North Atlantic, the Geochemical Ocean Sections Study (GEOSECS) and complementary oceanographic observation projects in 1972, and the Transient Tracers in the Oceans (TTO) in 1981 and 1983, are presented in comparative cross sections and maps representing conditions roughly one and two decades, respectively, after the first major tracer injections. The discussion emphasizes comparisons of the decay corrected tritium concentration fields, which show several distinct regimes of transient evolution, including examples of surprising constancy in some regional patterns. While largely supportive of previous qualitative ideas about transport patterns, these results also suggest that the patterns of deep water injection in high latitudes must have undergone a major change around or soon after the time of GEOSECS (1972), involving a major increase in supply of Upper North Atlantic Deep Water. The near-surface waters show strong signatures of tropical (low tritium) influence in the southwestern and western part of the subtropical gyre, while the northeastern part is influenced by continued tritium input from Arctic surface waters. Strong evidence for distinct sub-basin-scale interior circulation domains is found in the fact that the major distribution regime transitions seen in the GEOSECS data are observed again in TTO, and thus maintained through the second decade of the transient. The radiocarbon data set, which reflects the addition to the natural background distribution, supports the significance also on longer time scales of the mid-depth regime transition around 30°N latitude.

  10. Oxygen trends over five decades in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Stendardo, I.; Gruber, N.

    2012-11-01

    We investigate long-term trends in dissolved oxygen in the North Atlantic from 1960 to 2009 on the basis of a newly assembled high-quality dataset consisting of oxygen data from three different sources: CARINA, GLODAP and the World Ocean Database. Oxygen trends are determined along isopycnal surfaces for eight regions and five water masses using a general least-squares linear regression method that accounts for temporal auto-correlation. Our results show a significant decrease of oxygen in the Upper (UW), Mode (MW) and Intermediate (IW) waters in almost all regions over the last 5 decades. Over the same period, oxygen increased in the Lower Intermediate Water (LIW) and Labrador Sea Water (LSW) throughout the North Atlantic. The observed oxygen decreases in the MW and IW of the northern and eastern regions are largely driven by changes in circulation and/or ventilation, while changes in solubility are the main driver for the oxygen decrease in the UW and the increases in the LIW and LSW. From 1960 until 2009 the UW, MW, and IW horizons have lost a total of -57 ± 34 Tmol, while the LIW and LSW horizons have gained 46 ± 47 Tmol, integrating to a roughly constant oxygen inventory in the North Atlantic. Comparing our oxygen trends with those of the oceanic heat content, we find an O2 to heat change ratio of -3.6 ± 2.8 nmol J-1 for the UW, MW and IW, and a ratio of -2.8 ± 3.4 nmol J-1 for the LIW and LSW. These ratios are substantially larger than those expected from solubility alone.

  11. Predictability and numerical modelling of the North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

    Bojariu, Roxana; Gimeno, Luis

    2003-10-01

    The North Atlantic Oscillation (NAO) is the dominant pattern of atmospheric circulation variability in the extratropical Northern Hemisphere and it is a major controlling factor in basic meteorological variables such as surface wind, temperature and precipitation which have large socioeconomic impacts on energy, agriculture, industry, traffic and human health throughout the whole of Europe and eastern North America. Because of this dominant impact on the weather and climate of the wealthiest areas of the planet, there is a growing interest in quantifying the possible limits of predictability of the phenomenon and the ability of the climate numerical models of simulating it. This paper reviews recent work on predictability and methods of numerical modelling of the North Atlantic Oscillation used to simulate the phenomenon. Atmospheric models with no orography or land-sea contrasts are able to capture the main feature of the NAO; however, to capture any interannual or interdecadal variability of the NAO, atmospheric general circulation models (AGCM) with seasonally varying sea surface temperature (SSTs) forcing are required. Still, no model reproduces the recent observed upward trend in the NAO index, suggesting that either the models are deficient or external forcing such as man-made effects are responsible for this feature. Predictive patterns have been identified in the Atlantic SSTs preceding specific phases of the NAO by up to 6 months, in the atmospheric temperatures anomalies in the previous November, in the Eurasian snow cover and in the sea-ice extent over Arctic. The use of simulations based on ensemble prediction to estimate potential predictability shows the possibility of capturing the upward trend of the NAO and suggests that multiannual to multidecadal variations in the NAO are more predictable than interannual fluctuations.

  12. 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.

  13. 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.

  14. The Impact of North-South Shifts in the Sahel on North Atlantic Climate

    NASA Astrophysics Data System (ADS)

    Murphy, L.; Clement, A. C.; Mahowald, N. M.; Albani, S.; Swart, P. K.; Arienzo, M. M.

    2013-12-01

    Cool periods in the North Atlantic have been linked to hydrological changes over the Sahel region. It has been postulated that the Sahara-Sahel border shifted southwards during the last Heinrich event, which resulted in the semi-arid Sahel becoming more arid. This would drive changes in dust emission rates over North Africa. In fact proxy data indicates North Africa was dustier during the last Heinrich event than during the LGM. Recent analysis of CMIP5 models suggests the Western Sahel may become drier later this century. This may be analogous to past changes that have occurred in this region. Here we examine the implications of a southward shift in the Sahara-Sahel border in the Community Earth System Model version 1 (CESM1). Imposed changes in soil erodibility over the Sahel region results in greater dust emission rates and transport across the tropical Atlantic. Greater dust loading cools local sea surface temperatures and may have implications on the Atlantic Meridional Overturning Circulation. Our idealized runs can be used to understand how changes in dust forced climate change during the past as well as how potential future hydrological changes over the western Sahel can impact Atlantic climate.

  15. Constraining the North Atlantic circulation with tritium data

    NASA Technical Reports Server (NTRS)

    Memery, Laurent; Wunsch, Carl

    1990-01-01

    The North Atlantic circulation derived from an inverse calculation by singular-value decomposition is tested against the historical record of tritium. A forward calculation of the tritium transient is performed using the circulation model, published estimates of atmospheric injection rates, and plausible estimates of the tracer history at the open boundaries of the model. The results do not agree with observations of the interior distributions of tritium. Consideration is given to the possibility of improving the agreement by modifying the atmospheric injection rates and the initial estimates of open boundary time histories, treating the boundary conditions as control variables.

  16. Sea Level Variation at the North Atlantic Ocean from Altimetry

    NASA Astrophysics Data System (ADS)

    Vigo, I.; Sanchez-Reales, J. M.; Belda, S.

    2012-12-01

    About twenty years of multi-satellite radar altimeter data are analyzed to investigate the sea-level variation (SLV) of the North Atlantic Ocean. In particular seasonal variations and inter-seasonal trends are studied. Sea surface temperature and ice mass lost variations at Greenland are investigated as potential contributors of SLV in the case. It was found a quadratic acceleration term to be significant at some areas mainly located at the sub-polar gyre region. Results are consistent with changes in temperature data.

  17. Intercontinental transport of tropospheric ozone: a study of its seasonal variability across the North Atlantic utilizing tropospheric ozone residuals and its relationship to the North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

    Creilson, J. K.; Fishman, J.; Wozniak, A. E.

    2003-11-01

    Using the empirically-corrected tropospheric ozone residual (TOR) technique, which utilizes coincident observations of total ozone from the Total Ozone Mapping Spectrometer (TOMS) and stratospheric ozone profiles from the Solar Backscattered Ultraviolet (SBUV) instruments, the seasonal and regional distribution of tropospheric ozone across the North Atlantic from 1979-2000 is examined. Its relationship to the North Atlantic Oscillation (NAO) is also analyzed as a possible transport mechanism across the North Atlantic. Monthly climatologies of tropospheric ozone for five different regions across the North Atlantic exhibit strong seasonality. The correlation between these monthly climatologies of the TOR and ozonesonde profiles at nearby sites in both eastern North America and western Europe are highly significant (R values of +0.98 and +0.96 respectively) and help to validate the use of satellite retrievals of tropospheric ozone. Distinct springtime interannual variability over North Atlantic Region 5 (eastern North Atlantic-western Europe) is particularly evident and exhibits similar variability to the positive phase of the NAO (R=+0.61, r=<0.01). Positive phases of the NAO are indicative of a stronger Bermuda-Azores high and a stronger Icelandic low and thus faster more zonal flow across the North Atlantic from west to east. This flow regime appears to be causing the transport of tropospheric ozone across the North Atlantic and onto Europe. The consequence of such transport is the impact on a downwind region's ability to meet their ozone attainment goals. This link between the positive phase of the NAO and increased tropospheric ozone over Region 5 could be an important tool for prediction of such pollution outbreaks.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  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. 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.

  6. 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.

  7. Solar forcing synchronizes decadal North Atlantic climate variability

    PubMed Central

    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

  8. Numerical Simulation of North Atlantic Sea Ice Variability, 1951 - 1980

    NASA Technical Reports Server (NTRS)

    Walsh, J. E.

    1984-01-01

    A two-level dynamic-thermodynamic sea ice model is used to simulate the growth, drift and decay of sea ice in the Northern Hemisphere during a 30-year period, 1951 to 1980. The model is run with a daily timestep on a 222 km grid and is forced by interanually varying fields of geostrophic wind and temperature-derived thermodynamic fluxes. The objective is a quantitative description of large-scale sea ice variability in terms of the dynamic and thermodynamic processes responsible for the fluctuations, especially in the North Atlantic where sea ice represents a substantial input of fresh water. The fields of ice velocity and thickness contain strong seasonal as well as interannual variability. The mean drift pattern results in thicknesses of 4 to 5 m offshore of northern Canada and Greenland, while winter thicknesses of approximately 2 m are typical of Alaskan. Eurasian and East Greenland coastal waters. The 30-year mean fields are characterized by ecessive ice in the North Atlantic during winter and by a summer retreat that is more rapid than observed.

  9. Interdecadal Trichodesmium variability in cold North Atlantic waters

    NASA Astrophysics Data System (ADS)

    Rivero-Calle, Sara; Del Castillo, Carlos E.; Gnanadesikan, Anand; Dezfuli, Amin; Zaitchik, Benjamin; Johns, David G.

    2016-11-01

    Studies of the nitrogen cycle in the ocean generally assume that the distribution of the marine diazotroph, Trichodesmium, is restricted to warm, tropical, and subtropical oligotrophic waters. Here we show evidence that Trichodesmium are widely distributed in the North Atlantic. We report an approximately fivefold increase during the 1980s and 1990s in Trichodesmium presence near the British Isles with respect to the average over the last 50 years. A potential explanation is an increase in the Saharan dust source starting in the 1980s, coupled with changes in North Atlantic winds that opened a pathway for dust transport. Results from a coarse-resolution model in which winds vary but iron deposition is climatologically fixed suggest frequent nitrogen limitation in the region and reversals of the Portugal current, but it does not simulate the observed changes in Trichodesmium. Our results suggest that Trichodesmium may be capable of growth at temperatures below 20°C and challenge assumptions about their latitudinal distribution. Therefore, we need to reevaluate assumptions about the temperature limitations of Trichodesmium and the dinitrogen (N2) fixation capabilities of extratropical strains, which may have important implications for the global nitrogen budget.

  10. 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.

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

    USGS Publications Warehouse

    ,

    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. Changes in Sea Surface Temperature and North Atlantic Hurricane Activities

    NASA Astrophysics Data System (ADS)

    Nazari, R.; Mahani, S.; Khanbilvardi, R.

    2006-05-01

    People of United States from Maine to Texas in the years 1995 to 2005 experienced the highest level of North Atlantic hurricane activity in the reliable collected data and reports in compare with the generally low activity of the previous two decays (1970 to 1994). The greater activity might be a consequence of instantaneous changes in North Atlantic Sea Surface Temperature (SST) and air temperature. This thermal energy of increased Sea Surface Temperature (warm water) is known as tropical cyclone heat potential (TCHP) partly powers a hurricane and has been called hurricane fuel. In primary steps of this research we are trying to examine the association of variation of Sea Surface Temperature (SST), Sea Surface Height (SSH) and air temperature in the past decades with changes in hurricane number, duration and intensity. Preliminary analysis demonstrated that there is correlation between global warming and the occurrence of hurricanes because of the anticipated enhancement of energy available to the storms due to higher sea surface temperatures. The goal is to characterize and specify significant factors on tropical storms to improve the capability of predicting a hurricane and its damages to human lives and the economy. This information can be used to advise strategies for warning and also minimizing the magnitude of hurricane destruction, damages, and life losses.

  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. 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.

  15. 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.

  16. North Atlantic westerlies variability from ships' logbooks: 1685-2008

    NASA Astrophysics Data System (ADS)

    Barriopedro, David; Gallego, David; García-Herrera, Ricardo

    2014-05-01

    A monthly index based on the persistence of the westerly wind over the English Chanel is constructed for 1685-2008 using daily data from ships' logbooks and marine meteorological datasets. This Westerly Index (WI) provides the longest instrumental record of atmospheric circulation currently available. Anomalous WI values are associated with climatic signals in temperature and precipitation over large areas of Europe, which are stronger for precipitation than for temperature and in winter and summer than in transitional seasons. Overall, the WI series reveal that the frequency of the westerlies in the eastern Atlantic during the 20th century or the Late Maunder Minimum was not exceptional in the context of the last three centuries. The WI provides additional and complementary information to the North Atlantic Oscillation (NAO) indices. Thus, there is a significant year-round signature on precipitation and a seasonal-dependent temperature signal associated with the WI that is partially missed by the NAO indices. Although the WI reveals an overall good temporal agreement with the winter and high-summer NAO, there are several multidecadal periods of weakened correlation during the industrial era. These decoupled periods are interpreted on the basis of several sources of non-stationarity affecting the centres of the variability of the North Atlantic and their teleconnections. Comparisons with long instrumental indices extending back to the 17th century suggest that similar situations have occurred in the past, which call for caution when reconstructing the past atmospheric circulation from climatic proxies. In fact, there is a generally poor correlation of the WI with purely proxy-generated indices of the NAO.

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 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 Atlantic Right Whales. 224.105 Section 224.105 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE... AND ANADROMOUS SPECIES § 224.105 Speed restrictions to protect North Atlantic Right Whales. (a)...

  3. 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 Atlantic Right Whales. 224.105 Section 224.105 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE... AND ANADROMOUS SPECIES § 224.105 Speed restrictions to protect North Atlantic Right Whales. (a)...

  4. 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 Atlantic Right Whales. 224.105 Section 224.105 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE... AND ANADROMOUS SPECIES § 224.105 Speed restrictions to protect North Atlantic Right Whales. (a)...

  5. Chest CT Features of North American Paragonimiasis

    PubMed Central

    Henry, Travis S.; Lane, Michael A.; Weil, Gary J.; Bailey, Thomas C.; Bhalla, Sanjeev

    2013-01-01

    OBJECTIVE The purpose of this study was to characterize the chest CT findings of North American paragonimiasis due to Paragonimus kellicotti in the largest (to our knowledge) case series reported to date and to compare the findings with those reported for paragonimiasis infections in other regions. MATERIALS AND METHODS A retrospective review was performed of chest CT examinations of eight patients with North American paragonimiasis treated at our institution between 2006 and 2010. Findings were characterized by site of involvement, including lungs and pleura, heart and pericardium, lymph nodes, and upper abdomen. RESULTS The most common chest CT findings in this case series were pleural effusions and internal mammary and cardiophrenic lymphadenopathy. Pulmonary parenchymal findings included peripheral lung nodules of 1–3.5 cm in size with surrounding ground-glass opacity; many nodules had a linear track to the pleural surface that may correspond to the worm’s burrow tunnel. Pericardial involvement (5/8 patients) and omental inflammation (5/7 patients), which are uncommon in Asian paragonimiasis, were common in this series. CONCLUSION Pleural and pulmonary features of North American paragonimiasis are generally similar to those reported from Asia. The presence of a track between a pulmonary nodule and the pleura may help distinguish paragonimiasis from mimickers, including chronic eosinophilic pneumonia, tuberculosis, fungal infection, or malignancy. Pericarditis, lymphadenopathy, and omental inflammation were more common in our series than in reports on paragonimiasis from other regions. These differences may be related to the infecting parasite species or to the fact that radiologic examinations in the present series were performed relatively early in the course of infection. PMID:22528896

  6. 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.

  7. 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.

  8. North American Natural Gas Markets. Volume 1

    SciTech Connect

    Not Available

    1988-12-01

    This report sunnnarizes the 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.

  9. 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.

  10. Linking Agulhas Leakage Variability and North Atlantic Climate MIS 1-5a

    NASA Astrophysics Data System (ADS)

    Dyez, K. A.; Zahn, R.; Hall, I. R.

    2014-12-01

    Agulhas leakage of warm, salty water from the Indian Ocean to the South Atlantic is suggested to have altered Atlantic meridional overturning and climate in the North Atlantic. One way to assess such linkages with North Atlantic climate variability is to examine the past Agulhas hydrography via high-resolution marine records from the Agulhas Bank slope. Here we present one such hydrographic estimate from the Agulhas Bank slope in the Atlantic sector of the Agulhas Corridor using planktic foraminiferal (Globigerinoides ruber) δ18O and Mg/Ca-derived SST to estimate surface salinity. By focusing on the last 80,000 years this is the first quantitative fine-scale Agulhas leakage record that overlaps in time with the Greenland ice core record of abrupt climate changes in the North Atlantic region. Periods of enhanced Agulhas Corridor salinity occur at Northern Hemisphere cool periods (glacial termination and Heinrich meltwater events) and are followed by rapid northern hemisphere warming. We show that the timing of maximal salinity events in relation to periods of North Atlantic freshwater perturbation is consistent with the concept suggested by climate models that Agulhas salinity oscillations could provide buoyancy compensation for the Atlantic and potentially even trigger increased convective activity in the North Atlantic, thereby restoring Atlantic overturning circulation after relatively weak states.

  11. Temperature responses of some North Atlantic Cladophora species (Chlorophyceae) in relation to their geographic distribution

    NASA Astrophysics Data System (ADS)

    Cambridge, M.; Breeman, A. M.; van Oosterwijk, R.; van den Hoek, C.

    1984-09-01

    The temperature responses for growth and survival have been experimentally tested for 6 species of the green algal genus Cladophora (Chlorophyceae; Cladophorales) (all isolated from Roscoff, Brittany, France, one also from Connecticut, USA), selected from 4 distribution groups, in order to determine which phase in the annual temperature regime might prevent the spread of a species beyond its present latitudinal range on the N. Atlantic coasts. For five species geographic limits could be specifically defined as due to a growth limit in the growing season or to a lethal limit in the adverse season. These species were: (1) C. coelothrix (Amphiatlantic tropical to warm temperate), with a northern boundary on the European coasts formed by a summer growth limit near the 12°C August isotherm. On the American coasts sea temperatures should allow its occurrence further north. (2) C. vagabunda (Amphiatlantic tropical to temperate), with a northern boundary formed by a summer growth limit near the 15°C August isotherm on both sides of the Atlantic. (3) C. dalmatica, as for C. vagabunda. (4) C. hutchinsiae (Mediterranean-Atlantic warm temperate), with a northern boundary formed by a summer growth limit near the 12°C August isotherm, and possibly also a winter lethal limit near the 6°C February isotherm; and a southern boundary formed by a southern lethal limit near the 26°C August isotherm. It is absent from the warm temperate American coast because its lethal limits, 5° and 30°C, are regularly reached there. (5) Preliminary data for C. rupestris (Amphiatlantic temperate), suggest the southeastern boundary on the African coast to be a summer lethal limit near the 26°C August isotherm; the southwestern boundary on the American coast lies on the 20°C August isotherm. For one species, C. albida, the experimental growth and survival range was wider than expected from its geographic distribution, and reasons to account for this are suggested.

  12. 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.

  13. Abundant proteorhodopsin genes in the North Atlantic Ocean.

    PubMed

    Campbell, Barbara J; Waidner, Lisa A; Cottrell, Matthew T; Kirchman, David L

    2008-01-01

    Proteorhodopsin (PR) is a light-driven proton pump that has been found in a variety of marine bacteria, including Pelagibacter ubique, a member of the ubiquitous SAR11 clade. The goals of this study were to explore the diversity of PR genes and to estimate their abundance in the North Atlantic Ocean using quantitative polymerase chain reaction (QPCR). We found that PR genes in the western portion of the Sargasso Sea could be grouped into 27 clusters, but five clades had the most sequences. Sets of specific QPCR primers were designed to examine the abundance of PR genes in the following four of the five clades: SAR11 (P. ubique and other SAR11 Alphaproteobacteria), BACRED17H8 (Alphaproteobacteria), HOT2C01 (Alphaproteobacteria) and an uncultured subgroup of the Flavobacteria. Two groups (SAR11 and HOT2C01) dominated PR gene abundance in oligotrophic waters, but were significantly less abundant in nutrient- and chlorophyll-rich waters. The other two groups (BACRED17H8 and Flavobacteria subgroup NASB) were less abundant in all waters. Together, these four PR gene types were found in 50% of all bacteria in the Sargasso Sea. We found a significant negative correlation between total PR gene abundance and nutrients and chlorophyll but no significant correlation with light intensity for three of the four PR types in the depth profiles north of the Sargasso Sea. Our data suggest that PR is common in the North Atlantic Ocean, especially in SAR11 bacteria and another marine alphaproteobacterial group (HOT2C01), and that these PR-bearing bacteria are most abundant in oligotrophic waters.

  14. 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.

  15. Historical genomics of North American maize.

    PubMed

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

    2012-07-31

    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.

  16. 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.

  17. 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.

  18. Pathways of high-latitude dust in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Baddock, Matthew C.; Mockford, Tom; Bullard, Joanna E.; Thorsteinsson, Throstur

    2017-02-01

    The contribution of mineral dust from high-latitude sources has remained an under-examined feature of the global dust cycle. Dust events originating at high latitudes can provide inputs of aeolian sediment to regions lying well outside the subtropical dust belt. Constraining the seasonal variability and preferential pathways of dust from high-latitude sources is important for understanding the potential impacts that the dust may have on wider environmental systems, such as nearby marine or cryospheric domains. This study quantifies dust pathways from two areas exhibiting different emission dynamics in the north and south of Iceland, which is a prominent Northern Hemisphere dust source. The analysis uses air parcel trajectory modelling, and for the first time for high-latitude sources, explicitly links all trajectory simulations to time-specific (meteorological) observations of suspended dust. This approach maximises the potential for trajectories to represent dust, and illustrates that trajectory climatologies not limited to dust can grossly overestimate the potential for dust transport. Preferential pathways emerge that demonstrate the role of Iceland in supplying dust to the Northern Atlantic and sub-Arctic oceans. For dust emitted from northern sources, a dominant route exists to the northeast, into the Norwegian, Greenland and Barents Seas, although there is also potential for delivery to the North Atlantic in summer months. From the southern sources, the primary pathway extends into the North Atlantic, with a high density of trajectories extending as far south as 50°N, particularly in spring and summer. Common to both southern and northern sources is a pathway to the west-southwest of Iceland into the Denmark Strait and towards Greenland. For trajectories simulated at ≤500 m, the vertical development of dust plumes from Iceland is limited, likely due to the stable air masses of the region suppressing the potential for vertical motion. Trajectories rarely

  19. 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.

  20. Solar wind: A possible factor driving the interannual sea surface temperature tripolar mode over North Atlantic

    NASA Astrophysics Data System (ADS)

    Xiao, Ziniu; Li, Delin

    2016-06-01

    The effect of solar wind (SW) on the North Atlantic sea surface temperature (SST) in boreal winter is examined through an analysis of observational data during 1964-2013. The North Atlantic SSTs show a pronounced meridional tripolar pattern in response to solar wind speed (SWS) variations. This pattern is broadly similar to the leading empirical orthogonal function (EOF) mode of interannual variations in the wintertime SSTs over North Atlantic. The time series of this leading EOF mode of SST shows a significant interannual period, which is the same as that of wintertime SWS. This response also appears as a compact north-south seesaw of sea level pressure and a vertical tripolar structure of zonal wind, which simultaneously resembles the North Atlantic Oscillation (NAO) in the overlying atmosphere. As compared with the typical low SWS winters, during the typical high SWS winters, the stratospheric polar night jet (PNJ) is evidently enhanced and extends from the stratosphere to the troposphere, even down to the North Atlantic Ocean surface. Notably, the North Atlantic Ocean is an exclusive region in which the SW signal spreads downward from the stratosphere to the troposphere. Thus, it seems that the SW is a possible factor for this North Atlantic SST tripolar mode. The dynamical process of stratosphere-troposphere coupling, together with the global atmospheric electric circuit-cloud microphysical process, probably accounts for the particular downward propagation of the SW signal.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. Amplified North Atlantic warming in the late Pliocene by changes in Arctic gateways

    NASA Astrophysics Data System (ADS)

    Otto-Bliesner, Bette L.; Jahn, Alexandra; Feng, Ran; Brady, Esther C.; Hu, Aixue; Löfverström, Marcus

    2017-01-01

    Under previous reconstructions of late Pliocene boundary conditions, climate models have failed to reproduce the warm sea surface temperatures reconstructed in the North Atlantic. Using a reconstruction of mid-Piacenzian paleogeography that has the Bering Strait and Canadian Arctic Archipelago Straits closed, however, improves the simulation of the proxy-indicated warm sea surface temperatures in the North Atlantic in the Community Climate System Model. We find that the closure of these small Arctic gateways strengthens the Atlantic Meridional Overturning Circulation, by inhibiting freshwater transport from the Pacific to the Arctic Ocean and from the Arctic Ocean to the Labrador Sea, leading to warmer sea surface temperatures in the North Atlantic. This indicates that the state of the Arctic gateways may influence the sensitivity of the North Atlantic climate in complex ways, and better understanding of the state of these Arctic gateways for past time periods is needed.

  7. 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.

  8. 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%.

  9. 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.

  10. 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.

  11. 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.

  12. Synchronized terrestrial-atmospheric deglacial records around the North Atlantic

    SciTech Connect

    Bjoerck, S.; Rasmussen, T.L.; Kromer, B.

    1996-11-15

    On the basis of synchronization of three carbon-14 ({sup 14}C)-dated lacustrine sequences from Sweden with tree ring and ice core records, the absolute age of the Younger Dryas-Preboreal climatic shift was determined to be 11,450 to 11,390 {plus_minus} 80 years before the present. A 150-year-long cooling in the early Preboreal, associated with rising {Delta} {sup 14}C values, is evident in all records and indicates an ocean ventilation change. This cooling is similar to earlier deglacial coolings, and box-model calculations suggest that they all may have been the result of increased freshwater forcing that inhibited the strength of the North Atlantic heat conveyor, although the Younger Dryas may have been begun as an anomalous meltwater event. 53 refs., 8 figs., 1 tab.

  13. 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.

  14. Extreme wave parameters under North Atlantic extratropical cyclones

    NASA Astrophysics Data System (ADS)

    Ponce de León, S.; Guedes Soares, C.

    2014-09-01

    A characterization of extreme wave parameters during extratropical cyclones in the Northern hemisphere is made from WAM wave model hindcasts. In February 2007 two extratropical storms were observed in the North Atlantic and the wave fields associated with them are modeled in this paper. Wave buoy and satellite altimetry data were used to validate the WAM hindcast results. The distribution of the Benjamin-Feir index (BFI), kurtosis and the ratio of maximum wave height to significant wave height (abnormality index) around the eye of the two extratropical cyclones is studied. It is found that under these conditions the BFI and kurtosis are significantly larger mainly in the fourth quadrant and also when the wind direction is aligned with the wave propagation direction. In these regions the probability of occurrence of abnormal waves is higher.

  15. 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

  16. 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.

  17. Plastic accumulation in the North Atlantic subtropical gyre.

    PubMed

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

    2010-09-03

    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.

  18. 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.

  19. 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.

  20. 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

  1. 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

  2. Variability of North Sea pH and CO2 in response to North Atlantic Oscillation forcing

    NASA Astrophysics Data System (ADS)

    Salt, Lesley A.; Thomas, Helmuth; Prowe, A. E. Friederike; Borges, Alberto V.; Bozec, Yann; Baar, Hein J. W.

    2013-12-01

    biological activity causes a distinct seasonality of surface water pH in the North Sea, which is a strong sink for atmospheric CO2 via an effective shelf pump. The intimate connection between the North Sea and the North Atlantic Ocean suggests that the variability of the CO2 system of the North Atlantic Ocean may, in part, be responsible for the observed variability of pH and CO2 in the North Sea. In this work, we demonstrate the role of the North Atlantic Oscillation (NAO), the dominant climate mode for the North Atlantic, in governing this variability. Based on three extensive observational records covering the relevant levels of the NAO index, we provide evidence that the North Sea pH and CO2 system strongly responds to external and internal expressions of the NAO. Under positive NAO, the higher rates of inflow of water from the North Atlantic Ocean and the Baltic outflow lead to a strengthened north-south biogeochemical divide. The limited mixing between the north and south leads to a steeper gradient in pH and partial pressure of CO2 (pCO2) between the two regions in the productive period. This is exacerbated further when coinciding with higher sea surface temperature, which concentrates the net community production in the north through shallower stratification. These effects can be obscured by changing properties of the constituent North Sea water masses, which are also influenced by NAO. Our results highlight the importance of examining interannual trends in the North Sea CO2 system with consideration of the NAO state.

  3. Adaptive model of plankton dynamics for the North Atlantic

    NASA Astrophysics Data System (ADS)

    Pahlow, Markus; Vézina, Alain F.; Casault, Benoit; Maass, Heidi; Malloch, Louise; Wright, Daniel G.; Lu, Youyu

    2008-02-01

    Plankton ecosystems in the North Atlantic display strong regional and interannual variability in productivity and trophic structure, which cannot be captured by simple plankton models. Additional compartments subdividing functional groups can increase predictive power, but the high number of parameters tends to compromise portability and robustness of model predictions. An alternative strategy is to use property state variables, such as cell size, normally considered constant parameters in ecosystem models, to define the structure of functional groups in terms of both behaviour and response to physical forcing. This strategy may allow us to simulate realistically regional and temporal differences among plankton communities while keeping model complexity at a minimum. We fit a model of plankton and DOM dynamics globally and individually to observed climatologies at three diverse locations in the North Atlantic. Introducing additional property state variables is shown to improve the model fit both locally and globally, make the model more portable, and help identify model deficiencies. The zooplankton formulation exerts strong control on model performance. Our results suggest that the current paradigm on zooplankton allometric functional relationships might be at odds with observed plankton dynamics. Our parameter estimation resulted in more realistic estimates of parameters important for primary production than previous data assimilation studies. Property state variables generate complex emergent functional relationships, and might be used like tracers to differentiate between locally produced and advected biomass. The model results suggest that the observed temperature dependence of heterotrophic growth efficiency [Rivkin, R.B., Legendre, L., 2001. Biogenic carbon cycling in the upper ocean: effects of microbial respiration. Science 291 (5512) 2398-2400] could be an emergent relation due to intercorrelations among temperature, nutrient concentration and growth

  4. 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.

  5. North Atlantic Abyssal Circulation During Heinrich Event 1

    NASA Astrophysics Data System (ADS)

    Burke, A.; Marchal, O.; Francois, R.

    2007-12-01

    Pa-231/Th-230 ratios in three sediment cores from the North Atlantic have been used to infer changes in the meridional overturning circulation (MOC) over the past 20 kyr. The large Pa-231/Th-230 ratios (approaching the production ratio of the two radionuclides in the water column) during Heinrich Event 1 (H1) in core OCE326-GGC5 off of the Bermuda rise have been interpreted in terms of a reduced export of Pa-231 to the Southern Ocean owing to a slow-down of the MOC (McManus et al., Nature, 2004). Similar observations have been found in core SU81-18 from the Iberian continental margin (Gherardi et al., EPSL, 2005). The Pa-231/Th-230 record for core DAPC2 from the Norwegian Sea also has elevated values during H1, although variations in the flux of biogenic opal might be an important factor in controlling Pa-231/Th-230 ratios in the sediment (Hall et al., GRL, 2006). Here we will use an inverse method to combine Pa-231/Th-230 observations for H1 in these three cores with a model of the abyssal circulation in the North Atlantic basin. Two null hypotheses will be tested. The first null hypothesis is that the Pa-231/Th-230 data are consistent with the modern circulation. The second is that these data are consistent with a state of no flow in the abyssal region. In testing each hypothesis, due regard will be given to the uncertainties in both the Pa-231/Th-230 data and the model equations. By comparing the adjustments in the Pa-231/Th-230 values that are necessary to bring them into consistency with the modern circulation (hypothesis 1) and the state of rest (hypothesis 2), insight into the dynamical information contained in these data will be gained.

  6. 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.

  7. The alkenone temperature signal in western North Atlantic surface waters

    NASA Astrophysics Data System (ADS)

    Conte, M. H.; Weber, J. C.; King, L. L.; Wakeham, S. G.

    2001-12-01

    Haptophyte algae-derived long-chain C 37-C 39 alkenones and alkyl alkenoates were analyzed in euphotic zone particulate matter collected over a 7 yr period at the Oceanic Flux Program/Bermuda Atlantic Time Series (OFP/BATS) site in the western Sargasso Sea. Surface water temperatures at the site range annually from 19 to 29°C. Alkenone concentrations ranged from < 0.1 ng L -1 in summer to > 100 ng L -1 following the passage of storms. Highest seasonal concentrations occurred during the late winter and spring. Under stratified conditions, alkenone concentrations in the surface mixed layer (0-20 m) were generally 2 to 4 times higher than in the deep fluorescent maximum (75-110 m), consistent with Emiliania huxleyi concentration profiles (Haidar and Thierstein, 2001) and indicated that alkenone production primarily occurs within the upper euphotic zone in this region. Alkenone compound distributions and the temperature calibrations of C 37 and C 38 methyl and ethyl alkenone unsaturation (U 37K', U 38MeK, and U 38EtK, respectively) were remarkably similar to that observed in an E. huxleyi strain previously isolated from the same area (Conte et al., 1998), providing strong evidence that E. huxleyi is the predominant alkenone synthesizer and that characteristics exhibited by randomly isolated clones in culture are, in many cases, consistent with those of populations in the region of origin. The Bermuda calibration of U 37K' vs. water temperature (U 37K' = -1.9835 + 0.2004T - 0.0034T 2, r 2 = 0.95, n = 91) is nonlinear and falls along the same trendline as euphotic zone particulates from warm (> 15°C) waters of the eastern North Atlantic (Conte and Eglinton, 1993) and Mediterranean (Ternois et al., 1997). The combined North Atlantic temperature calibration (U 37K' = - 1.1365 + 0.1257T - 0.0018T 2, r 2 = 0.963, n = 134) differs significantly from published coretop sediment calibrations (Rosell-Melé et al., 1995; Müller et al., 1998) based on sea surface temperature

  8. 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... Conservation Council will meet to select North American Wetlands Conservation Act grant proposals for recommendation to the Migratory Bird Conservation Commission. This meeting is open to the public, and...

  9. 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…

  10. 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 (draft Plan Revision) for public review. We request review and comment on the draft Plan Revision...

  11. 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.

  12. Cephalometric floating norms for North American adults.

    PubMed

    Franchi, L; Baccetti, T; McNamara, J A

    1998-12-01

    Floating norms provide a method of analysis that uses the variability of the associations among suitable cephalometric measures, on the basis of a regression model combining both sagittal and vertical skeletal parameters. This study establishes floating norms for the description of the individual skeletal pattern in North American adults. The method is based on the correlations among the following craniofacial measurements: SNA, SNB, NL-NSL, ML-NSL, and NSBa. The results are given in a graphical box-like form. This easy, practical procedure allows for the identification of either individual harmonious craniofacial features or anomalous deviations from the individual norm. The use of cephalometric floating norms may be helpful for diagnosis and treatment planning in orthognathic surgery and dentofacial orthopedics.

  13. 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.

  14. 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.

  15. 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.

  16. Lithospheric layering in the North American craton.

    PubMed

    Yuan, Huaiyu; Romanowicz, Barbara

    2010-08-26

    How cratons-extremely stable continental areas of the Earth's crust-formed and remained largely unchanged for more than 2,500 million years is much debated. Recent studies of seismic-wave receiver function data have detected a structural boundary under continental cratons at depths too shallow to be consistent with the lithosphere-asthenosphere boundary, as inferred from seismic tomography and other geophysical studies. Here we show that changes in the direction of azimuthal anisotropy with depth reveal the presence of two distinct lithospheric layers throughout the stable part of the North American continent. The top layer is thick ( approximately 150 km) under the Archaean core and tapers out on the surrounding Palaeozoic borders. Its thickness variations follow those of a highly depleted layer inferred from thermo-barometric analysis of xenoliths. The lithosphere-asthenosphere boundary is relatively flat (ranging from 180 to 240 km in depth), in agreement with the presence of a thermal conductive root that subsequently formed around the depleted chemical layer. Our findings tie together seismological, geochemical and geodynamical studies of the cratonic lithosphere in North America. They also suggest that the horizon detected in receiver function studies probably corresponds to the sharp mid-lithospheric boundary rather than to the more gradual lithosphere-asthenosphere boundary.

  17. North Atlantic Oscillation and timing of spring migration in birds.

    PubMed Central

    Hüppop, Ommo; Hüppop, Kathrin

    2003-01-01

    Migrant birds have been trapped on the island of Helgoland (southeastern North Sea) since 1909, with methods and sampling effort remaining unchanged throughout the last four decades. In 12 short/medium-distance migrants and 12 long-distance migrants (23 passerines plus the European woodcock) sample sizes were sufficient to calculate mean spring passage (msp) times and to relate these to climate change. All but one species, passing Helgoland en route to their breeding areas (mainly in Scandinavia), show a trend towards earlier msp-time, which is significant in 7 short/medium-distance migrants and 10 long-distance migrants. The msp-times advanced by 0.05-0.28 days per year, short/medium-distance migrants not differing from long-distance migrants. In 23 out of the 24 species, earlier msp-times coincide with local warmer msp-temperatures (significantly in 11 and 7 species of the two groups, respectively). Even more striking is the relation to a large-scale phenomenon, the North Atlantic Oscillation (NAO), during the last four decades. Again, in 23 out of the 24 species, an earlier msp-time coincides with higher NAO indices (significantly in 9 and 12 species, respectively). The NAO index can also explain differences and similarities in spring migration strategies, as well as migration routes within Europe. PMID:12614571

  18. 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...

  19. 78 FR 33857 - Meeting Announcements: North American Wetlands Conservation Council; Neotropical Migratory Bird...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-05

    ...; 91100-3740-GRNT 7C] Meeting Announcements: North American Wetlands Conservation Council; Neotropical... meetings. SUMMARY: The North American Wetlands Conservation Council (Council) will meet to select North American Wetlands Conservation Act (NAWCA) grant proposals for recommendation to the Migratory...

  20. 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...

  1. 75 FR 65624 - Notice of Attendance at North American Electric Reliability Corporation Meetings

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-26

    ... Energy Regulatory Commission Notice of Attendance at North American Electric Reliability Corporation... Commission and Commission staff may attend the following North American Electric Reliability Corporation... Reliability Corporation; Docket No. RC08-5, North American Electric Reliability Corporation; Docket No....

  2. 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...

  3. Changes in North Atlantic circulation at the end of the Cretaceous greenhouse interval

    NASA Astrophysics Data System (ADS)

    MacLeod, K. G.; Isaza Londoño, C.; Martin, E. E.; Jiménez Berrocoso, Á.; Basak, C.

    2011-11-01

    The mechanics of ocean circulation during the Late Cretaceous greenhouse interval remain contested, with the role of North Atlantic Deep Water in ocean circulation particularly debated: the relative warming of the North Atlantic during the termination of the greenhouse interval has been attributed to heat piracy from North Atlantic Deep Water formation, but the sources of Cretaceous deep water have been difficult to resolve. Nd isotopes as captured by seafloor sediments and expressed as εNd(t) reflect the region in which the water mass was formed. Here we present εNd(t) measurements from Cretaceous- to Palaeogene-aged sediments from four cores in the tropical North Atlantic. Before 69Myr ago, we find extremely low εNd(t) values of about -16, consistent with the presence of a warm, saline deep water mass formed in the low latitudes. By 62Myr ago, εNd(t) values had risen to -11, similar to values reported from the northern North Atlantic over the past 65 million years, but lower than most contemporaneous values in the South Atlantic and Pacific oceans. We therefore suggest that the εNd(t) shift reflects the increasing influence of a northern-sourced water mass at this site, indicating the onset or intensification of deep- or intermediate-water formation in the North Atlantic 69Myr ago. Our findings support the heat piracy model and imply that circulation patterns during the greenhouse interval were different from those of the subsequent relatively temperate interval.

  4. 77 FR 16538 - Endangered and Threatened Species; Initiation of 5-Year Review for the North Atlantic Right Whale...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-21

    ...; Initiation of 5-Year Review for the North Atlantic Right Whale and the North Pacific Right Whale AGENCY... review of North Atlantic right whale (Eubalaena glacialis) and North Pacific right whale (Eubalaena... of any such information on these whales that has become available since the last status review...

  5. Thermomechanical model of the North American lithosphere

    NASA Astrophysics Data System (ADS)

    Tesauro, Magdala; Kaban, Mikhail; Cloetingh, Sierd; Mooney, Walter

    2014-05-01

    An integrated thermomechanical model of the lithosphere has been constructed based on various data sets and method. A consistent 3D model of the North American crust is based on the most recent seismic data from the USGS database. To this aim, we (1) defined the geometry of the main geological provinces of North America, (2) selected and evaluated the reliability of seismic crustal models in the database, (3) estimated the P-wave seismic velocity and thickness of the upper, middle and lower crust for each geological province. Temperature variations in the upper mantle have been estimated, taking into account compositional changes in cratonic regions, by applying a new inversion technique, which jointly interpret seismic velocities and gravity data. First, we inverted two tomography models into temperatures, using a uniform composition representative of a 'Primitive' mantle, which was affected by a small amount of melt extraction. In the next step, the thermal component of the density was estimated according to these initial thermal fields and was subtracted from the total density, to obtain the compositional component. These preliminary results might be affected by compositional changes of the cratonic upper mantle, usually depleted in heavy constituents. Then, the gravity effect of temperature variations is estimated and removed from the mantle gravity anomalies. The residual (temperature free) mantle anomalies are used to evaluate compositional changes in the cratonic mantle. We re-estimated the temperatures, using this new composition, and repeat calculations of the thermal and compositional density variations. These steps are reiterated until the convergence is reached. The results show that the upper mantle of the Archean North American cratons is characterized by temperatures higher than ~150°C compared to the initial thermal model, and by strong negative compositional density anomalies (-0.03 g/cm3), corresponding to Mg # (100xMg/(Mg+Fe)) >92. In turn, in

  6. 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.

  7. American Children in North-East Scotland

    ERIC Educational Resources Information Center

    Wedgeworth, Vickie S. E.

    1977-01-01

    Explores differences in the attitudes of American students attending the American School in Aberdeen, which was established for expatriate Americans and follows an American curriculum, and American students attending local Scotish schools. Focuses on acculturation, ethnocentrism, stereotyping, the sense of national identity, as well as to see how…

  8. 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.

  9. Climatology and Atmospheric Chemistry of Non-Methane Hydrocarbon Emissions over the North Atlantic

    NASA Astrophysics Data System (ADS)

    Helmig, Detlev; Hueber, Jacques; Munoz, Mauricio; Mazzoleni, Claudio; Mazzoleni, Lynn; Owen, Robert; Val-Martin, Maria; Fialho, Paulo

    2013-04-01

    Non-methane hydrocarbons (NMHC) spanning the C2-C7 volatility range have been monitored at the Pico Mountain Observatory, located at 2,225 m a.s.l., on Pico Island, in the Azores, Portugal, since 2004. Observations at this site, due to the topography, location, and height of the station, during most times reflect long-range transport of air from the continents bordering the North Atlantic. The multi-year data records show that NMHC mole fractions exhibit regular annual cycles with winter maxima and summer minima. Short-term variability of the data is driven by transport events typically lasting 2-5 days. During these events NMHC absolute levels show significant increases over their seasonal background. NMHC ratios were applied to estimate the degree of photochemical processing and transport time to the station. Transport events identified from the NMHC data were then analyzed for emission source region and transport pathway using HYSPLIT model outputs. The multi-year observations were applied to develop a seasonality of the pollution transport to Pico and contributing source regions. These analyses show that emissions from the North American continent are the primary cause for elevated NMHC levels observed at the station. Most identified transport events originate from urban areas; biomass burning transport from boreal North America was identified in a few selected cases during late summer. Emissions in air transported from Europe and Africa were encountered only on a few occasions.

  10. 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.

  11. Interannual oscillations and the weather over the North Atlantic

    NASA Astrophysics Data System (ADS)

    Feliks, Yizhak; Robertson, Andrew; Ghil, Michael

    2014-05-01

    The interannual oscillations have small amplitude with respect to the amplitudes of mid-latitude weather systems, like the winter cyclones. Thus it is not clear how these weak oscillations affect the weather systems. We explore this problem over the North Atlantic basin (NAB) by using the NCEP-NCAR reanalysis on a 2.5x2.5 degree grid for 1949-2012. We partition the North Atlantic into into four rectangular regions, divided by the 45 W meridian and the 40 N parallel. The winter average (DJFM) of the daily transient kinetic energy of the geostrophic wind (GTKE) over these four quadrants was calculated at the 500-hPa level. The mean of the GTKE over each region shows prominent year-to-year variability. The GTKE variability contains three oscillatory modes, with periods of 8.7, 5.6 and 2.7 years. These oscillatory modes are highly significant statistically and close in period to the interannual oscillations found in the North Atlantic Oscillation (NAO) index (Feliks et al. 2010, 2013). The correlations between the winter average of the NAO index and the spatial GTKE average in the four quadrants are: NE = 0.82, SE = -0.79, NW = 0.54 and SW = -0.56. So the role of the NAO is significantly more prominent as expected in the eastern NAB, and there is a phase opposition between the northern and southern quadrants. The absolute value of the GTKE in the NE is larger by an order of magnitude than in the SE. The interannual oscillatory modes of the GTKE in the NE and those of the NAO index are completely synchronized. Only in the winter does the spatial average of the GTKE over any quadrant exceed a threshold value of 220 m2s-2; this value corresponds roughly to the presence of a strong winter storm within the given quadrant. The number of days during which the GTKE exceeds this value changes significantly from year to year; it is between 6 to 83 days in the NE quadrant and between 0 and 1 day in the SE quadrant. This number of days correlates with the NAO index at 0.85; the

  12. 75 FR 67960 - North American Electric Reliability Corporation; Notice of Compliance Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-04

    ...] North American Electric Reliability Corporation; Notice of Compliance Filing October 28, 2010. Take notice that on October 25, 2010, the North American Electric Reliability Corporation (NERC), submitted...

  13. North Atlantic Current variability and associated mixing at the Mid-Atlantic Ridge (observed)

    NASA Astrophysics Data System (ADS)

    Walter, M.; Mertens, C.; Dengler, M.; Rhein, M.

    2012-12-01

    Observational evidence for enhanced turbulent energy dissipation at sites of topography- mesoscale flow interaction indicates the possible role of fronts and eddies as energy source for mixing. In consequence, changes in the (upper ocean) flow field must have an impact on stratification and circulation in the deep ocean as patterns of mixing and water mass transformation may be altered by changing the locations of flow-topography interactions. In the north Atlantic, the North Atlantic Current (NAC) that crosses the Mid-Atlantic Ridge (MAR) between 48° and 54°N is known to shift its position and develop different branch modes in response to the prevalent wind field. Strength and positioning of the branches is modulated by the slowly varying eddy field and corresponds to the gaps in the MAR: the northern branch, also known as subpolar front (SPF) crosses the ridge at the latitude of the Charlie-Gibbs Fracture Zone (CGFZ), the southern branches are less restricted and more eddy dominated, but tend to align with the Faraday or Maxwell Fracture Zones. We use repeated observations of hydrography and currents at the SPF west of the Mid-Atlantic Ridge to investigate the temporal variability of the spatial distribution of finescale variance and derived properties (as diapycnal diffusivity and integrated energy dissipation) in their relation to the position of the NAC. The CTD and lowered ADCP observations were carried out during three (summer) cruises in 2008, 2010, and 2011. During the 2008 cruise, additional microstructure data was collected at three stations, used to validate dissipation rates from a shear/strain parameterization in the upper 1200 m. The orientation of the repeat section is roughly in southeast-northwest direction, starting at about 48°N and ending near the western exit of the CGFZ. The position of the NAC shows considerable differences between the three realizations. In 2008, a single branch mode was found, with the SPF approximately at 50°30'N. In

  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. 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.

  16. North Atlantic sea surface temperature, solar activity and the climate of Northern Fennoscandia

    NASA Astrophysics Data System (ADS)

    Ogurtsov, M.; Lindholm, M.; Jalkanen, R.; Veretenenko, S. V.

    2017-02-01

    Seven proxies of summer temperature in Northern Fennoscandia, sea surface temperature in the North Atlantic and solar activity were analyzed over AD 1567-1986. A stable and significant positive correlation between summer temperatures in Northern Fennoscandia and sea surface temperature in the North Atlantic is shown to exist during the entire time interval. In addition, a significant correlation between solar activity and (a) summer temperature in Northern Fennoscandia as well as (b) surface temperature in the North Atlantic was found during AD 1715-1986. Throughout 1567-1715 correlation is less significant and has an opposite sign. Thus we show that the variation of sea surface temperature in the North Atlantic could be a physical agent, which transferred solar influence on Northern Fennoscandian temperature at least during AD 1715-1986.

  17. 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.

  18. 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.

  19. The Population Consequences of Disturbance Model Application to North Atlantic Right Whales (Eubalaena Glacialis)

    DTIC Science & Technology

    2013-09-30

    in beaked and sperm whales (R. Rolland, PI; ONR # N000141110540), and a study on the detection and use of hormones from right whale respiratory...1 The Population Consequences of Disturbance Model Application to North Atlantic Right Whales (Eubalaena Glacialis) Scott D. Kraus, Amy R...the revised approach is called PCOD (Population Consequences Of Disturbance) . In North Atlantic right whales (Eubalaena glacialis), extensive data on

  20. North Atlantic tropical cyclone track migration since 1550 A.D. revealed using a Belizean stalagmite

    NASA Astrophysics Data System (ADS)

    Baldini, Lisa; Baldini, James; Frappier, Amy; Ridley, Harriet; Asmerom, Yemane; Prufer, Keith; Breitenbach, Sebastian; Aquino, Valorie; Polyak, Victor; Awe, Jaime

    2015-04-01

    A gradual shift in the geographic distribution of hurricanes and tropical storms from the western Caribbean to the US Atlantic Coast between 1550 and 1983 A.D. is revealed by an annually-resolved, 456-year record of tropical cyclone (TC) activity reconstructed using sub-annually resolved carbon and oxygen isotope ratios in stalagmite YOK-G from Yok Balum Cave, southern Belize. Annual geochemical cycles combined with 230Th dating provide excellent chronological control, and the hurricane season signal intensity is reconstructed using seasonally-specific isotope ratios. The stalagmite hurricane season signal correlates very well with HURDAT2 western Caribbean TC count over the calibration period (1945-1983) as well as over the 25-year verification period. Our record suggests very few TCs affected the western Caribbean in the mid-1500s, but that this was followed by gradually rising western Caribbean TC activity that peaked during the Little Ice Age (LIA). Western Caribbean TC activity then decreases gradually from the mid-1600s to present day, with abrupt shifts at 1790 A.D. and 1870 A.D. Comparison with basin-wide TC reconstructions reveals a northward shift in the geographic distribution of TC impacts over the past few hundred years, from dominantly western Caribbean during the LIA to substantially more along the North American Atlantic margin during the 20th Century. Our reconstruction suggests that NAO variability played a major role in driving these shifts in dominant storm tracks through time.

  1. Magnetic Anomalies Between 35 N and 55 N in the North Atlantic: Identification and Implications

    NASA Astrophysics Data System (ADS)

    Luis, J.; Miranda, J. M.

    2005-12-01

    In this work we present a new approach to the detailed identification and interpretation of the magnetic isochrones 5, 6, 13, 18, 20, 22, 22, 23, 24, 25, 26, 28, 29, 30, 32, 33 and 33r on the Eurasian as well as on the American plate, between 55° N and 35° N in the North Atlantic. The identifications were based on a continuous reduction to the pole new technique. From the detailed reconstruction of magnetic isochrones and flow lines, we show that the East Azores Fracture Zone cannot be considered as homologous to the Pico Fracture Zone, implying that a significant amount of the Azores plateau was formed as an independent lithospheric band accreted to the Eurasian plate between the time of anomaly 22 (49 Ma) and ~5 (10 Ma). Based on magnetic anomalies and morphological constrains we reconstruct the previous configurations of the Azores plateau. In particular, we extend a previous study of the Mid-Atlantic Ridge (MAR) for the period 0-10 Ma to a wider time interval into a schematic evolution model for the Azores Triple Junction area. The new isochrones identifications and computation of Euler rotation poles have also implications in the movement of the ancient Iberia plate. Contrary to the currently accepted belief that its movement with respect to the Eurasia plate ended about the time of anomaly 6 (20 Ma), we found no evidences of any movement after the time of anomaly 18 (~38 Ma).

  2. 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

  3. 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.

  4. The Transient Tracers in the Ocean (TTO) program: The North Atlantic Study, 1981; The Tropical Atlantic Study, 1983

    NASA Astrophysics Data System (ADS)

    Brewer, Peter G.; Sarmiento, Jorge L.; Smethie, William M.

    1985-01-01

    The scientific papers here collected result from the Transient Tracers in the Ocean (TTO) program. The two parts of this major geochemical and physical oceanographie expedition took place in the North Atlantic Ocean in 1981 and in the Tropical Atlantic in 1983 on the research vessel Knorr of the Woods Hole Oceanographie Institution. The expeditions, sponsored by the National Science Foundation and the U.S. Department of Energy (North Atlantic only), were designed to observe the passage of man-made geochemical tracers into the interior of the ocean. The foundations for such an experiment were laid in the 1972-1978 GEOSECS program. Here, for the first time, a systematic survey revealed the penetration into the thermocline and deep ocean of the products of man's military/industrial activities, principally tritium and carbon-14 resulting from atmospheric testing of nuclear weapons, which terminated with the nuclear test ban treaty in 1962.

  5. 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

    2011-11-07

    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.

  6. 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

  7. The temporal evolution of North American kimberlites

    NASA Astrophysics Data System (ADS)

    Heaman, Larry M.; Kjarsgaard, Bruce A.; Creaser, Robert A.

    2004-09-01

    North American kimberlite magmatism spans a period of time in excess of 1 billion years from Mesoproterozoic kimberlites in the Lake Superior and James Bay Lowlands region of Ontario to Eocene kimberlites in the Lac de Gras field, N.W.T. Based on a compilation of more than 150 robust radiometric age determinations, several distinct kimberlite emplacement patterns are recognized. In general, the temporal pattern of kimberlite emplacement in North America can be broadly subdivided into five domains: (1) a Mesoproterozoic kimberlite province in central Ontario, (2) an Eocambrian/Cambrian Labrador Sea Province in northern Québec and Labrador, (3) an eastern Jurassic Province, (4) a central Cretaceous corridor and (5) a western mixed domain that includes two Type-3 kimberlite provinces (i.e. multiple periods of kimberlite emplacement preserved in the Slave and Wyoming cratons). For some provinces the origin of kimberlite magmatism can be linked to known mantle heat sources such as mantle plume hotspots and upwelling asthenosphere attendant with continental rifting. For example, the timing and location of Mesoproterozoic kimberlites in North America coincides with and slightly precedes the timing of 1.1 Ga intracontinental rifting that culminated in the Midcontinent Rift centered in the Lake Superior region. Many of the kimberlites in the Eocambrian/Cambrian Labrador Sea province were emplaced soon after the opening of the Iapetus Ocean at about 615 Ma and may also be linked to mantle upwelling associated with continental rifting. The eastern Jurassic kimberlites record an age progression where magmatism youngs in a southeast direction from the ˜200 Ma Rankin Inlet kimberlites to the 155-126 Ma Timiskaming kimberlites. The location of several kimberlite fields and clusters in Ontario and Québec lie along a continental extension of the Great Meteor hotspot track and represents one of the best examples in the world of kimberlite magmatism triggered by mantle plumes. The

  8. 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

  9. 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

  10. 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

  11. 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

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

    PubMed

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

    2010-08-01

    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

  13. A chlorofluorocarbon section in the eastern North Atlantic

    NASA Astrophysics Data System (ADS)

    Doney, Scott C.; Bullister, John L.

    1992-11-01

    We present the distributions of two chlorofluorocarbons (CFCs) CFC-11 and CFC-12, measured as part of a hydrographic section between Iceland and the equator during July and August 1988. CFC-tagged water has filled the entire subpolar water column and subtropical thermocline in the eastern North Atlantic. Measurable CFC concentrations are observed at the ocean bottom as far south as 35°N, and the CFC penetration depth shoals to ≈750 m in the tropics. Specific features in the CFC distributions include a clear signal of Labrador Sea mid-depth ventilation, a CFC-enriched overflow water boundary current along the Iceland slope, and a mid-depth, equatorial plume of upper North Atlantic Water. The CFC data are used, in conjuction with the hydrographic data from the cruise, to illustrate the ventilation time-scales and pathways for the water masses in the eastern basin. A subsurface CFC maximum at about 100-200 m depth in the subtropics is shown to be a by-product of the heating and degassing of the seasonal thermocline and of the temperature sensitivity of CFC solubility. The CFC concentrations in the subpolar mode water are undersaturated by 15-18% relative to the atmosphere, reflecting the age of the mode waters and the very deep winter mixed layers in the eastern subpolar gyre. The CFC concentrations in the oxygen minimum off tropical Africa are much lower than the concentrations in the subtropical gyre, supporting previous work that suggests that isolation and enhanced productivity both contribute to the formation of the tropical oxygen minimum. In addition, the CFC inventories at the tropical stations have increased between 1982 and 1983 (TTO/TAS) and the summer of 1988 at a slower rate relative to the subtropical inventories over the same period. Thermocline oxygen utilization rates calculated from the CFC concentration data range from 5 to 10 μmol kg -1y -1 and are in line with previous estimates for the eastern subtropical thermocline. The low CFC

  14. Exercise prescription--North American experience.

    PubMed Central

    Shephard, R. J.

    1978-01-01

    The principles of exercise prescription are reviewed with respect to North American experience. The required regimen must be safe, therapeutically effective, and ensure a high rate of compliance. Precautions to increase the safety of exercise are discussed. Cardiac emergencies are sufficiently rare events (less than 1 in 200,000 hours even in post-coronary classes) that the need for immediate medical supervision of a well-designed programme can be questioned. The prime determinant of the response to training is the intensity of effort relative to the individual's initial fitness. Post-coronary patients often have a great potential for training due to their previous inactivity, but this will not be realised if the prescribed exercise is of insufficient intensity. Exercise programmes are plagued by a high 'drop-out' rate; 50% of normal middle-aged volunteers are lost in 6 months, and even with post-coronary programmes losses can be 60--70% over 4 years. Simple suggestions are made for improving compliance with the required exercise prescription. PMID:444812

  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. Dynamics of North American breeding bird populations

    NASA Astrophysics Data System (ADS)

    Keitt, Timothy H.; Stanley, H. Eugene

    1998-05-01

    Population biologists have long been interested in the variability of natural populations. One approach to dealing with ecological complexity is to reduce the system to one or a few species, for which meaningful equations can be solved. Here we explore an alternative approach, by studying the statistical properties of a data set containing over 600 species, namely the North American breeding bird survey. The survey has recorded annual species abundances over a 31-year period along more than 3,000 observation routes. We now analyse the dynamics of population variability using this data set, and find scaling features in common with inanimate systems composed of strongly interacting subunits. Specifically, we find that the distribution of changes in population abundance over a one-year interval is remarkably symmetrical, with long tails extending over six orders of magnitude. The variance of the population over a time series increases as a power-law with increasing time lag, indicating long-range correlation in population size fluctuations. We also find that the distribution of species lifetimes (the time between colonization and local extinction) within local patches is a power-law with an exponential cutoff imposed by the finite length of the time series. Our results provide a quantitative basis for modelling the dynamics of large species assemblages.

  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. Incidental oligotrophication of North American Great Lakes.

    PubMed

    Evans, Mary Anne; Fahnenstiel, Gary; Scavia, Donald

    2011-04-15

    Phytoplankton production is an important factor in determining both ecosystem stability and the provision of ecosystem goods and services. The expansive and economically important North American Great Lakes are subjected to multiple stressors and understanding their responses to those stresses is important for understanding system-wide ecological controls. Here we show gradual increases in spring silica concentration (an indicator of decreasing growth of the dominant diatoms) in all basins of Lakes Michigan and Huron (USA and Canadian waters) between 1983 and 2008. These changes indicate the lakes have undergone gradual oligotrophication coincident with and anticipated by nutrient management implementation. Slow declines in seasonal drawdown of silica (proxy for seasonal phytoplankton production) also occurred, until recent years, when lake-wide responses were punctuated by abrupt decreases, putting them in the range of oligotrophic Lake Superior. The timing of these dramatic production drops is coincident with expansion of populations of invasive dreissenid mussels, particularly quagga mussels, in each basin. The combined effect of nutrient mitigation and invasive species expansion demonstrates the challenges facing large-scale ecosystems and suggest the need for new management regimes for large ecosystems.

  19. 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.

  20. 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.

  1. 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.

  2. [Medical services on an inspection ship in the north Atlantic].

    PubMed

    Kjaer, A

    1990-10-29

    The Danish Naval Inspection Ships sail in the North Atlantic waters with a doctor on board. The object of this investigation was to illustrate the medical services on board and to elucidate the significance of various factors to predict seeking medical advice. During a period of three months, all of the medical services and certain basic factors were registered. The crew was interviewed about consumption of alcohol and tobacco, previous life at sea and family background. A total of 305 consultations were used by the crew of 72 men. This figure is five times the anticipated figure in general practice. Low rank and low age were predictors for frequent medical consultations. The diagnosis groups of traumata/injuries, dermatological conditions and disease in the nervous system or organs of sense were relatively overrepresented. A series of factors may possibly have influenced the pattern of seeking medical help so that this differs from general practice. It is concluded that the dangerous working environment and poor possibilities for good hygiene are important factors whereas the mental stress is of lesser significance.

  3. Extreme storm activity in North Atlantic and European region

    NASA Astrophysics Data System (ADS)

    Vyazilova, N.

    2010-09-01

    The extreme storm activity study over North Atlantic and Europe includes the analyses of extreme cyclone (track number, integral cyclonic intensity) and extreme storm (track number) during winter and summer seasons in the regions: 1) 55°N-80N, 50°W-70°E; 2) 30°N-55°N, 50°W-70°E. Extreme cyclones were selected based on cyclone centre pressure (P<=970 mbar). Extreme storms were selected from extreme cyclones based on wind velocity on 925 mbar. The Bofort scala was used for this goal. Integral cyclonic intensity (for region) includes the calculation cyclone centers number and sum of MSLP anomalies in cyclone centers. The analyses based on automated cyclone tracking algorithm, 6-hourly MSLP and wind data (u and v on 925 gPa) from the NCEP/NCAR reanalyses from January 1948 to March 2010. The comparision of mean, calculated for every ten years, had shown, that in polar region extreme cyclone and storm track number, and integral cyclonic intensity gradually increases and have maximum during last years (as for summer, as for winter season). Every ten years means for summer season are more then for winter season, as for polar, as for tropical region. Means (ten years) for tropical region are significance less then for polar region.

  4. 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.

  5. Genetic differentiation among North Atlantic killer whale populations.

    PubMed

    Foote, Andrew D; Vilstrup, Julia T; De Stephanis, Renaud; Verborgh, Philippe; Abel Nielsen, Sandra C; Deaville, Robert; Kleivane, Lars; Martín, Vidal; Miller, Patrick J O; Oien, Nils; Pérez-Gil, Monica; Rasmussen, Morten; Reid, Robert J; Robertson, Kelly M; Rogan, Emer; Similä, Tiu; Tejedor, Maria L; Vester, Heike; Víkingsson, Gísli A; Willerslev, Eske; Gilbert, M Thomas P; Piertney, Stuart B

    2011-02-01

    Population genetic structure of North Atlantic killer whale samples was resolved from differences in allele frequencies of 17 microsatellite loci, mtDNA control region haplotype frequencies and for a subset of samples, using complete mitogenome sequences. Three significantly differentiated populations were identified. Differentiation based on microsatellite allele frequencies was greater between the two allopatric populations than between the two pairs of partially sympatric populations. Spatial clustering of individuals within each of these populations overlaps with the distribution of particular prey resources: herring, mackerel and tuna, which each population has been seen predating. Phylogenetic analyses using complete mitogenomes suggested two populations could have resulted from single founding events and subsequent matrilineal expansion. The third population, which was sampled at lower latitudes and lower density, consisted of maternal lineages from three highly divergent clades. Pairwise population differentiation was greater for estimates based on mtDNA control region haplotype frequencies than for estimates based on microsatellite allele frequencies, and there were no mitogenome haplotypes shared among populations. This suggests low or no female migration and that gene flow was primarily male mediated when populations spatially and temporally overlap. These results demonstrate that genetic differentiation can arise through resource specialization in the absence of physical barriers to gene flow.

  6. Abrupt cooling over the North Atlantic in modern climate models

    PubMed Central

    Sgubin, Giovanni; Swingedouw, Didier; Drijfhout, Sybren; Mary, Yannick; Bennabi, Amine

    2017-01-01

    Observations over the 20th century evidence no long-term warming in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future abrupt SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG warming trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models' varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This event occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future abrupt SPG cooling, entailing crucial implications for observation and adaptation policy. PMID:28198383

  7. Anatomical predictions of hearing in the North Atlantic right whale.

    PubMed

    Parks, Susan E; Ketten, Darlene R; O'Malley, Jennifer T; Arruda, Julie

    2007-06-01

    Some knowledge of the hearing abilities of right whales is important for understanding their acoustic communication system and possible impacts of anthropogenic noise. Traditional behavioral or physiological techniques to test hearing are not feasible with right whales. Previous research on the hearing of marine mammals has shown that functional models are reliable estimators of hearing sensitivity in marine species. Fundamental to these models is a comprehensive analysis of inner ear anatomy. Morphometric analyses of 18 inner ears from 13 stranded North Atlantic right whales (Eubalaena glacialis) were used for development of a preliminary model of the frequency range of hearing. Computerized tomography was used to create two-dimensional (2D) and 3D images of the cochlea. Four ears were decalcified and sectioned for histologic measurements of the basilar membrane. Basilar membrane length averaged 55.7 mm (range, 50.5 mm-61.7 mm). The ganglion cell density/mm averaged 1,842 ganglion cells/mm. The thickness/width measurements of the basilar membrane from slides resulted in an estimated hearing range of 10 Hz-22 kHz based on established marine mammal models. Additional measurements from more specimens will be necessary to develop a more robust model of the right whale hearing range.

  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. Circulation Across 52w In The North Atlantic

    NASA Astrophysics Data System (ADS)

    Hall, M.; Joyce, T.; Pickart, R.; Smethie, W.

    The zonal circulation across the 52W meridian in the North Atlantic is described, as deduced from hydrographic and ADCP data. The data were collected in a 1997 cruise as part of the World Ocean Circulation Experiment, from the Grand Banks southeast of Newfoundland down to Suriname, South America (near 7 deg N, 53.5 deg W), and included shipboard and lowered ADCP (SADCP and LADCP) data along with hydro- graphic, nutrient, and CFC data. To analyze the circulation, first, geostrophic velocity shear was calculated using the hydrographic data. Next, an initial reference level ve- locity for each station pair was obtained by comparison of the geostrophic shear with the SADCP and LADCP data. Finally, an inverse calculation was applied, which con- served mass and silica within prescribed tolerance levels in 17 neutral density layers as well as overall. Because LADCP data were lacking over a crucial subset of stations in the northern Deep Western Boundary Current and throughout the Gulf Stream sys- tem, error bars on the final circulation are necessarily large. This result emphasizes the importance of collecting LADCP data concurrently with hydrographic data. Results will be presented in terms of velocity sections, transport streamfunctions, and total transports for major currents. Most surprising in the results is the strength of the deep circulation away from the boundary currents.

  10. Abrupt cooling over the North Atlantic in modern climate models.

    PubMed

    Sgubin, Giovanni; Swingedouw, Didier; Drijfhout, Sybren; Mary, Yannick; Bennabi, Amine

    2017-02-15

    Observations over the 20th century evidence no long-term warming in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future abrupt SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG warming trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models' varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This event occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future abrupt SPG cooling, entailing crucial implications for observation and adaptation policy.

  11. Abrupt cooling over the North Atlantic in modern climate models

    NASA Astrophysics Data System (ADS)

    Sgubin, Giovanni; Swingedouw, Didier; Drijfhout, Sybren; Mary, Yannick; Bennabi, Amine

    2017-02-01

    Observations over the 20th century evidence no long-term warming in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future abrupt SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG warming trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models' varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This event occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future abrupt SPG cooling, entailing crucial implications for observation and adaptation policy.

  12. 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.

  13. 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...

  14. 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

    2012-06-12

    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.

  15. 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

  16. Impact of the December North Atlantic Oscillation on the following February East Asian trough

    NASA Astrophysics Data System (ADS)

    Qiao, Shaobo; Feng, Guolin

    2016-09-01

    During winter, the December North Atlantic Oscillation (NAO) has an impact on the following February East Asian trough (EAT), and a significant positive correlation exists between them. It is shown that the circulation anomalies affected by the December NAO for December and for the following January are primarily confined to the Euro-Atlantic sector while they extend to East Asia during the following February, and this is related to anomalous wave trains originating from the southwestern Atlantic and spreading to the northeastern Atlantic, northern Europe, western Siberia, and East Asia. When the NAO is positive phase in December, the sea surface temperature (SST) tripole pattern is forced by persistence positive NAO from December to the following January, contributing to pronounced positive SST anomalies in midlatitude areas of the North Atlantic during the following February. The pronounced positive SST anomalies found during this period can generate feedback for atmospheric anomalies, and the westerly winds are enhanced (reduced) to the north (south) side of the positive SST anomalies, which result from strengthened (weakened) baroclinicity there. In addition, the Rossby wave source over the northeastern Atlantic shows a positive anomaly, establishing a link between the positive SST anomalies in midlatitude areas of the North Atlantic and the deepened EAT downstream.

  17. 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.

  18. The North West African Margin Magnetic Anomaly revisited : implications for the initial evolution of the Central Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Sahabi, M.; Olivet, J.-L.; Aslanian, D.; Patriat, M.; Géli, L.; Matias, L.; Réhault, J.-P.; Malod, J.; Bouabdelli, M.

    2003-04-01

    Due to the lack of data from the North West African margin, the Mesozïc evolution of the Central Atlantic is still controversial. Existing plate kinematics (Le Pichon et al, 1977), Wissmann and Roger (1982), Olivet et al, 1984, Klitgord and Schouten, 1986) reconstructions do not explain the characteristics of the S1 Magnetic Anomaly, nor the the presence and geometry of salt basins on the margins off NW Marocco and off Mauritania. We present a new magnetic compilation detailing the correspondance between the different conjugated magnetic anomalies that exist on each side of the Central Atlantic : the East Coast (ECMA), Brunswick (BMA) and Blake Spur (BSMA) Magnetic Anomalies on the American side, and the S1 and West African Coast (WACMA) magnetic anomalies on the African side. In addition, using all available, academic, seismic data, we mapped the ocenawards extension of the salt province of the 200 Ma old Seine Abyssal Plain basin, off Marocco, which is considered as autochtonous.

  19. 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.

  20. Genetics Home Reference: North American Indian childhood cirrhosis

    MedlinePlus

    ... Facebook Share on Twitter Your Guide to Understanding Genetic Conditions Search MENU Toggle navigation Home Page Search ... Conditions Genes Chromosomes & mtDNA Resources Help Me Understand Genetics Home Health Conditions North American Indian childhood cirrhosis ...

  1. 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

  2. Intersocietal Relationships by Evolutionary Levels among North American Indians.

    ERIC Educational Resources Information Center

    Price, John A.

    1983-01-01

    Extends use of evolutionary theory in understanding developmental processes within societies for examining patterns occuring between societies. Emphasizes North American Indian situations. Examines four degrees of intersocietal integration: first contact, low, medium and high. (MH)

  3. 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

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

    MedlinePlus

    North American Society for Pediatric Gastroenterology, Hepatology and Nutrition Skip to Navigation NASPGHAN Annual Meeting and Postgraduate ... Fellows Concise Review of Pediatric Gastroenterology, Hepatology and Nutrition (Second Edition) An e-book is posted on ...

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. Phenomena of pulsation tectonics related to the breakup of the eastern north American continental margin

    NASA Astrophysics Data System (ADS)

    Sheridan, Robert E.

    1983-05-01

    New data from the recent IPOD drilling of DSDP Site 534 in the Blake-Bahama Basin give a definite age for the spreading-center shift involved in the breakup of the North American Atlantic margin. A basal Callovian age (~ 155 m.y.) is determined for the Blake Spur magnetic anomaly marking this spreadingcenter shift that signals the birth of the modern North Atlantic Ocean. This is some 20 m.y. younger than previously thought. An implication of this younger age for the Blake Spur event is that very high spreading rates are now required for the Jurassic outer magnetic quiet zone along the North American margin. This association of a relatively high spreading rate with a magnetic quiet zone is similar to that for the mid-Cretaceous and implies a link between the processes controlling plate spreading, which are in the upper mantle, and the processes controlling the magnetic field, which are in the outer core. A theory of pulsation tectonics involving the cyclic eruption of plumes of hot mantle material from the lowermost mantle could explain the correlation. Plumes carry heat away from the core-mantle boundary and later reach the asthenosphere and lithosphere to induce faster spreading. The pulse of fast spreading in the Jurassic apparently followed the breakup of continents bordering the North Atlantic Ocean. Other pulses of fast spreading appear to correlate with major ocean openings on various parts of the globe, implying that this might be a prevalent process. Rifting of passive margins may be controlled by the more fundamental global processes described by the theory of pulsation tectonics.

  11. 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

  12. 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

  13. 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).

  14. 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.

  15. 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

  16. The 'individualization' of large North American mammals.

    PubMed

    Ruth, J L; Fain, S R

    1993-01-01

    The enforcement of wildlife laws and the captive breeding of threatened/endangered species requires the ability to identify individual animals. DNA profiles of a variety of large North American mammals, birds, and fish were generated using ten different oligonucleotide probes. The probes tested were four multilocus probes [33.6, 33.15, JE46, and (TGTC)5] and six 'human unilocus' probes [MS1 (D1S7), CMM101 (D14S13), YNH24 (D2S44), EFD52 (D17S26), TBQ7 (D10S28), and MS43 (D12S11). Each of the probes was chemically synthesized, and labeled by the attachment of alkaline phosphatase; after hybridization, the probes were detected by chemiluminescence catalyzed by the enzyme. Initial screening against zoo blots including samples of bear, wolf, large cat, wild sheep, deer, birds, marine mammals, and fish indicated that three multilocus probes [33.15, 33.6, (TGTC)5] gave informative patterns containing 15-40 bands for most or all of the animals tested, as did two of the 'human unilocus' probes (MS1 and CMM101). The other five probes appeared informative only in some species (for example, YNH24 against canids). Subsequent screenings of populations within species were used to determine genetic diversity by analysis of observed bandsharing (S). Large heterologous populations, such as white-tailed deer, exhibited highly diverse band patterns (S < or = 0.2). Geographically isolated and/or genetically constricted animals, such as endangered Mexican wolves, Tule elk, and Columbian white-tailed deer, exhibited much higher frequencies of bandsharing (0.6 < or = S < or = 0.95).(ABSTRACT TRUNCATED AT 250 WORDS)

  17. 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.

  18. 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.

  19. Motivations of North American Indians in Athletic Games.

    ERIC Educational Resources Information Center

    Pesavento, Wilma J.

    This is a report on the motives of North American Indians in holding their athletic games. Data were researched from "Annual Reports of the Bureau of American Ethnology" published between 1881 and 1933. Anthropologists, artifact collectors, artist-writers, and historians provided primary evidential sources for athletic game motivation.…

  20. THE NORTH AMERICAN MERCURY MODEL INTER-COMPARISON STUDY (NAMMIS)

    EPA Science Inventory

    This paper describes the North American Mercury Model Inter-comparison Study (NAMMIS). The NAMMIS is an effort to apply atmospheric Hg models in a tightly constrained testing environment with a focus on North America. With each model using the same input data sets for initial co...

  1. Model investigations of the North Atlantic spring bloom initiation

    NASA Astrophysics Data System (ADS)

    Kuhn, Angela M.; Fennel, Katja; Mattern, Jann Paul

    2015-11-01

    The spring bloom - a massive growth of phytoplankton that occurs annually during the spring season in mid and high latitudes - plays an important role in carbon export to the deep ocean. The onset of this event has been explained from bottom-up and top-down perspectives, exemplified by the "critical-depth" and the "dilution-recoupling" hypotheses, respectively. Both approaches differ in their key expectations about how seasonal fluctuations of the mixed layer affect the plankton community. Here we assess whether the assumptions inherent to these hypotheses are met inside a typical onedimensional Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) model, optimized to best represent climatological annual cycles of satellite-based phytoplankton biomass in the Subpolar North Atlantic. The optimized model is used in idealized experiments that isolate the effects of mixed layer fluctuations and zooplankton grazing, in order to elucidate their significance. We analyzed the model sensitivity qualitatively and using a second-order Taylor series decomposition of the model equations. Our results show that the conceptual bases of both bottom-up and top-down approaches are required to explain the process of blooming; however, neither of their bloom initiation mechanisms fully applies in the experiments. We find that a spring bloom can develop in the absence of mixed layer fluctuations, and both its magnitude and timing seem to strongly depend on nutrient and light availability. Furthermore, although zooplankton populations modulate the phytoplankton concentrations throughout the year, directly prescribed and physically driven changes in zooplankton grazing do not produce significant time shifts in bloom initiation, as hypothesized. While recognizing its limitations, our study emphasizes the processes that require further testing in order to discern among competing hypotheses.

  2. Ships' logbooks and North Atlantic air circulation reconstructions 1685 - 1750

    NASA Astrophysics Data System (ADS)

    Wheeler, D.; Ward, C.; Wilkinson, C.; Garcia-Herrera, R.

    2010-09-01

    Much attention has been given to the study of documentary records that chronicle climatic events in Europe over the past half-millennium and more. It is inevitable that such sources have focussed on events on land. Hitherto it has often been assumed that correspondingly useful and contemporary material is not available for the oceans. This assumption is incorrect, and recent activities by the authors of this contribution have drawn increasingly wide attention to the vast fund of information available in the logbooks of ships, and particularly those of the Royal Navy. For the pre-instrumental period, which can be taken as before the mid-nineteenth century, some 120,000 logbooks reside in British archives containing over 20,000,000 days of observations of wind force and direction. This presentation takes a sub-sample of this huge collection and confines its attention to the North East Atlantic region, focussing on the seas around the British Isles. A daily record of wind force and direction has been abstracted and worked up into monthly-aggregated values for the period 1685 to 1750. We review the changing nature of air circulations over this critical period, which includes the Maunder Minimum and the years of gradual but by no means consistent warming that marked the first half of the eighteenth century. Conclusions are drawn about the fashion in which the organisation of the air circulations are reflected in, and help to, explain the temperature fluctuations of that period. Conclusions are also drawn concerning the changing patterns of wind strength and

  3. Seismic Imaging of Thermohaline Circulation in the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Falder, M.; White, N. J.; Sheen, K. L.; Caulfield, C. P.

    2012-12-01

    We present seismic reflection images of the full water column acquired during a 2010 cruise in the North Atlantic Ocean on the RSS James Cook. A total of 2600 km of seismic data with a horizontal resolution of ~10 m were acquired, including two long transects > 1000 km long. These transects extend from Hatton Bank to the Greenland shelf and cross smooth, intermediate and rough bathymetry. Coeval, expendable conductivity-temperature-depth probes and ADCP measurements permit hydrographic calibration of the seismic images. Seismic processing included dense (~ 1.5 km) velocity picking and iterative pre-stack depth migration, which optimised the acoustic velocity model and increased our confidence in the depth conversion. On both transects, we observe thermohaline structures, such as eddies, fronts and internal waves, together with lateral changes in geometry and reflective character. In places, the amplitude and character of the internal waves may be affected by interaction with rough bathymetry. The largest mesoscale eddy is 60 km in diameter, occurring between 300 and 1100 m depth. Asymmetric reflections wrap around this feature. ADCP data demonstrate that this eddy rotates clockwise at 0.4 m/s in agreement with previous studies. Spectral analysis of internal waves show the classic transition from a Garrett-Munk to a Kolmogorov/Bachelor slope, allowing diapycnal diffusivity estimates to be made. In this way, we hope to test the paradigm that enhanced mixing rates occur over rougher bathymetry in oceanic basins. These long transects are rich in detail and we hope that a quantitative analysis will yield useful physical oceanographic insights.

  4. 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.

  5. A Subtropical North Atlantic Regional Atmospheric Moisture Budget

    NASA Astrophysics Data System (ADS)

    Bingham, F.; D'Addezio, J. M.

    2014-12-01

    The synergistic effects of evaporation (E), precipitation (P), and Ekman transport make the SPURS (Salinity Processes in the Upper Ocean Regional Study) region in the subtropical North Atlantic (15-30°N, 30-45°W) the ideal location for the world's highest open ocean sea surface salinity. Using the MERRA and ERA-Interim atmospheric reanalyses, we reproduce the mean hydrologic state of the atmosphere over the SPURS region since 1979 and roughly deduce the change in salinity across the meridional domain due solely to interactions between E-P and Ekman transport. Our findings suggest a region that is highly evaporative at a mean rate of 4.87 mm/day with a standard deviation of 1.2 mm/day and little seasonality. Precipitation is much more variable with an annual fall maximum around 3 mm/day but only a mean rate of 1.37 mm/day with a standard deviation of 1.46 mm/day. The resulting E-P variable has a mean rate of 3.50 mm/day with a standard deviation of 1.92 mm/day and matches well with the moisture flux divergence term although the former is typically larger by a small margin. Strong prevailing easterly trade winds generate northward Ekman transports that advect water northward to the salinity maximum around 25°N. A short calculation shows that atmospheric moisture dynamics could potentially account for almost half of the change in salinity between 15°N and 25°N giving an estimate of the role that surface freshwater flux plays in the maintenance of the salinity maximum.

  6. A subtropical North Atlantic regional atmospheric moisture budget

    NASA Astrophysics Data System (ADS)

    D'Addezio, Joseph M.; Bingham, Frederick M.

    2014-12-01

    The synergistic effects of evaporation (E), precipitation (P), and Ekman transport make the Salinity Processes in the Upper Ocean Regional Study (SPURS-1) region in the subtropical North Atlantic (15-30°N, 30-45°W) the natural location for the world's highest open ocean SSS maximum. Using the MERRA and ERA-Interim atmospheric reanalyses, we reproduce the mean hydrologic state of the atmosphere over the SPURS-1 region since 1979 and roughly deduce the change in salinity across the meridional domain due solely to interactions between E-P and Ekman transport. Our findings suggest a region that is highly evaporative at a mean rate of 4.87 mm/d with a standard deviation of 1.2 mm/d and little seasonality. Precipitation is much more variable with an annual fall maximum around 3 mm/d but only a mean rate of 1.37 mm/d with a standard deviation of 1.46 mm/d. The resulting E-P variable has a mean rate of 3.50 mm/d with a standard deviation of 1.92 mm/d and matches well with the moisture flux divergence term although the former is typically larger by a small margin. Strong prevailing easterly trade winds generate northward Ekman transports that advect water toward the salinity maximum around 25°N. A short calculation shows that atmospheric moisture dynamics could potentially account for about one third of the change in salinity between 15°N and 25°N giving an estimate of the role that surface freshwater flux plays in the maintenance of the salinity maximum.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. North Atlantic climate evolution through the Plio-Pleistocene climate transitions

    NASA Astrophysics Data System (ADS)

    Lawrence, K. T.; Sosdian, S.; White, H. E.; Rosenthal, Y.

    2010-12-01

    During the Plio-Pleistocene, the Earth witnessed the growth of large northern hemisphere ice sheets and profound changes in both North Atlantic and global climate. Here, we present a ~ 3.2 Myr long, orbitally-resolved alkenone sea surface temperature (SST) record from Deep Sea Drilling Project (DSDP) Site 607 (41°N, 33°W, water depth 3427 m) in the North Atlantic Ocean. We employ a multi-proxy approach comparing these new observations with existing bottom water temperature (BWT) and stable isotope time series from the same site and SST time series from other sites, shedding new light on Plio-Pleistocene climate change. North Atlantic temperature records show a long-term cooling with two major steps occurring during the late Pliocene (3.1 to 2.4 Ma) and the mid-Pleistocene (1.5 to 0.8 Ma), closely timed with intervals of major change in northern hemisphere ice sheets. Existing evidence suggests that the late Pliocene cooling may have been caused by a thresholded response to secular changes in atmospheric carbon dioxide (CO 2). While an explanation for the mid-Pleistocene cooling may involve glacial-interglacial changes in atmospheric CO 2, it seems to also require a change in the behavior of the ice sheets themselves. North Atlantic climate responses were closely phased with benthic oxygen isotope (δ 18O) changes during the "41 kyr world," indicating a strong common northern hemisphere high latitude imprint on North Atlantic climate signals. After the mid-Pleistocene transition (MPT), North Atlantic SST records and the Site 607 benthic carbon isotope (δ 13C) record are more closely phased with δ 18O, whereas BWT significantly leads δ 18O in the 100 kyr band, suggesting a shift from a northern to a southern hemisphere influence on North Atlantic BWT. We propose that the expansion of the West Antarctic ice sheet (WAIS) across the MPT increased the production and export of Antarctic Bottom Water from the Southern Ocean and subsequently controlled its incursion

  12. The Variation of Tropical Cyclone Rainfall within the North Atlantic and Pacific as Observed from Satellites

    NASA Technical Reports Server (NTRS)

    Rodgers, Edward; Pierce, Harold; Adler, Robert

    1999-01-01

    Tropical cyclone monthly rainfall amounts are estimated from passive microwave satellite observations in the North Atlantic and in three equal geographical regions of the North Pacific (i.e., Western, Central, and Eastern North Pacific). These satellite-derived rainfall amounts are used to assess the impact of tropical cyclone rainfall in altering the geographical, seasonal, and inter-annual distribution of the 1987-1989, 1991-1998 North Atlantic and Pacific rainfall during June-November when tropical cyclones are most abundant. To estimate these tropical cyclone rainfall amounts, mean monthly rain rates are derived from the Defence Meteorological Satellite Program (DMSP) Special Sensor Microwave/ Radiometer (SSM/I) observations within 444 km radius of the center of those North Atlantic and Pacific tropical cyclones that reached storm stage and greater. These rain rate observations are then multiplied by the number of hours in a given month. Mean monthly rainfall amounts are also constructed for all the other North Atlantic and Pacific raining systems during this eleven year period for the purpose of estimating the geographical distribution and intensity of rainfall contributed by non-tropical cyclone systems. Further, the combination of the non-tropical cyclone and tropical cyclone (i.e., total) rainfall is constructed to delineate the fractional amount that tropical cyclones contributed to the total North Pacific rainfall.

  13. Multi-decadal uptake of carbon dioxide into subtropical mode water of the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Bates, N. R.

    2012-07-01

    Natural climate variability impacts the multi-decadal uptake of anthropogenic carbon dioxide (Cant) into the North Atlantic Ocean subpolar and subtropical gyres. Previous studies have shown that there is significant uptake of CO2 into subtropical mode water (STMW) of the North Atlantic. STMW forms south of the Gulf Stream in winter and constitutes the dominant upper-ocean water mass in the subtropical gyre of the North Atlantic Ocean. Observations at the Bermuda Atlantic Time-series Study (BATS) site near Bermuda show an increase in dissolved inorganic carbon (DIC) of +1.51 ± 0.08 μmol kg-1 yr-1 between 1988 and 2011, but also an increase in ocean acidification indicators such as pH at rates (-0.0022 ± 0.0002 yr-1) higher than the surface ocean (Bates et al., 2012). It is estimated that the sink of CO2 into STMW was 0.985 ± 0.018 Pg C (Pg = 1015 g C) between 1988 and 2011 (70 ± 1.8% of which is due to uptake of Cant). The sink of CO2 into the STMW is 20% of the CO2 uptake in the North Atlantic Ocean between 14°-50° N (Takahashi et al., 2009). However, the STMW sink of CO2 was strongly coupled to the North Atlantic Oscillation (NAO), with large uptake of CO2 into STMW during the 1990s during a predominantly NAO positive phase. In contrast, uptake of CO2 into STMW was much reduced in the 2000s during the NAO neutral/negative phase. Thus, NAO induced variability of the STMW CO2 sink is important when evaluating multi-decadal changes in North Atlantic Ocean CO2 sinks.

  14. Variability of shelf sea pH and surface water CO2 in response to North Atlantic Oscillation forcing

    NASA Astrophysics Data System (ADS)

    Salt, L.; Thomas, H.; Prowe, A. E. F.; Borges, A. V.; de Baar, H. J. W.

    2012-04-01

    High biological activity causes a distinct seasonality of surface water pH in the North Sea, which has been identified as a strong sink for atmospheric CO2 via a particularly effective shelf pump. The intimate connection between the North Sea and the North Atlantic suggests that the variability of the CO2 system of the North Atlantic Ocean may in part be responsible for the observed, but hitherto poorly understood variability of pH and CO2 in the North Sea. Here we investigate the role of the North Atlantic Oscillation (NAO), the dominant climate mode for the North Atlantic hemisphere in governing this variability. Based on three extensive observational records covering the relevant levels of the NAO index, we provide evidence that the North Sea pH and CO2 system strongly responds to external and internal expressions of the NAO. We argue that under NAO+ conditions higher rates of inflow of water from the North Atlantic Ocean limits seasonal shoaling of the summer mixed layer in the northern North Sea, diminishing the biological potential to lower pCO2 and raise pH. In addition the faster circulation of the North Sea enhances the shelf pump efficiency. These clear patterns are obscured by changing properties of the North Sea waters, masking or enforcing these effects on various time scales. Such controls indicate that inter-annual trends in the North Sea CO2 system must be carefully examined with consideration to the North Atlantic Oscillation.

  15. 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.

  16. Influence of the North Atlantic dipole on climate changes over Eurasia

    NASA Astrophysics Data System (ADS)

    Serykh, I. V.

    2016-11-01

    In this paper, some hydrophysical and meteorological characteristics of negative (1948-1976 and 1999-2015) and positive (1977-1998) phases of the Pacific Decadal Oscillation (PDO) and Interdecadal Pacific Oscillation (IPO) in the North Atlantic and Eurasia are constructed and investigated. Specifically, the near-surface temperature, sea-level atmospheric pressure, wind speed, heat content of the upper 700 m ocean layer, water temperature and salinity at various depths, the latent and sensible heat fluxes from the ocean to the atmosphere are analyzed. The fields obtained are in good agreement and complement each other. This gives important information about the hydrometeorological conditions in the region under study. Analysis of these data has shown that in the upper 1000 m North Atlantic layer there is a thermal dipole which can be interpreted as an oceanic analog of the atmospheric North Atlantic Oscillation (NAO). An index of the North Atlantic Dipole (NAD) as the difference between the mean heat contents in the upper 700 m oceanic layer between the regions (50°-70° N; 60°-10° W) and (20°-40° N; 80°-30° W) is proposed. A possible physical mechanism of the internal oscillations with a quasi-60-year period in the North Atlantics- Eurasia system of ocean-atmosphere interactions is discussed.

  17. 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.

  18. 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.

  19. Pleistocene effects on North American songbird evolution

    PubMed Central

    Klicka, J.; Zink, R. M.

    1999-01-01

    Recent studies have used comparisons of mitochondrial DNA (mtDNA) sequence divergence among populations and species to test existing hypotheses about avian evolution during the Pleistocene epoch. In 1998, Avise and Walker concluded that the Pleistocene was an important time for avian evolution, including the initiation of phylogeographic separations and the completion of speciation events that began in the Pliocene. The study implied that these conclusions conflicted with the study, in 1997, by Klicka and Zink, which concluded that most species pairs previously thought to have originated in the past 250 000 years were much older. The two studies are complementary in the sense that Avise and Walker dealt primarily with phylogeographic (intraspecific) separations. Furthermore, Klicka and Zink concentrated on the inception of divergences whereas the Avise and Walker focused on the timing of the completion of speciation. To accomplish this, Avise and Walker analysed 'phylogroups', geographically coherent subsets of biological species in which mtDNA haplotypes exhibit reciprocal monophyly. The study used the average interphylogroup mtDNA distance (0.027), calibrated at 2% per million years, to conclude that speciation required on average one million years to complete. Hence, speciation events begun in the Late Pliocene would have been completed in the mid- to late Pleistocene. Although we appreciate the extended nature of the speciation process and Avise and Walker's insightful attempt to estimate its duration, we conclude that their value was an overestimate by a factor of two. In particular we question whether phylogroups can be used in the novel evolutionary role that Avise and Walker envisioned, because of the vagaries of taxonomic practices and lack of consensus regarding species concepts. To extend their analysis of intraspecific, phylogeographic separations, we compiled previously analysed and newly available data for divergence times for North American songbird

  20. 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.

  1. Reconstruction of pollutant lead transport and input in the western north atlantic area during the past century

    NASA Astrophysics Data System (ADS)

    Desenfant, F.; Camoin, G. F.; Veron, A.

    2003-04-01

    There are only few available proxies for marine transport of continental aerosols. Although pelagic sediments can record past deposition, they are not suitable for seasonal and/or interannual detailed records due to low sedimentation rates. We have studied trace metal deposition and associated air mass circulation based on coral records. Indeed, the skeleton of zooxanthellate scleractinian corals represents a potentially important database for the record of environmental parameters. It is used more frequently for paleoenvirronment reconstruction so far in tropical zones, for which only a few sources of information are available. Shen et al (1988 -- Chemical Geology) have demonstrated the capability of these coral skeletons to record anthropogenic lead transport and deposition to the North American basin, in Bermuda. We have collected massive corals from the Caribbean in order to determine the anthropogenic impact of industrial emissions in the western North Atlantic during the past century. Sources and atmospheric circulation are considered at regional and basin scale depending on the location of the sampling sites in the northern (Puerto Rico) and western (Martinique, Guadeloupe) Caribbean. Here we use the capability of lead and its stable isotopes to trace the continental origin of anthropogenic sources and its transport within the North Atlantic troposphere. Measurements of lattice bound lead in sequential coral bands have revealed temporal changes in lead concentration and lead isotope ratios. Anthropogenic perturbations are clearly evidenced at all sites of the Caribbean area, linked to increase of industrial activities and the use of leaded gasoline in the US and Western Europe. Specific variations are related to regional inputs and seasonal changes in air mass circulation. The latter are determined and coupled to lead variations using stable isotope records (O) and meteorological index (North Atlantic Oscillation). Such coral records also provide reliable

  2. 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

  3. 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

  4. North American influence on atmospheric carbon dioxide data collected at Sable Island, Canada

    NASA Astrophysics Data System (ADS)

    Worthy, Douglas E. J.; Higuchi And, Kaz; Chan, Douglas

    2003-04-01

    Continuous and flask measurements of atmospheric CO2 taken at Sable Island from August 1992 to April 1993 are presented and characterised as a function of air mass origin. The atmospheric environment over Sable Island (43°56'N, 60°01'W) is continuously influenced by the complex meteorology of synoptic systems moving off North America. This makes the interpretation of the Sable Island CO2 data difficult. However, trajectory analysis shows distinct quantitative differences between the statistics of CO2 measurements associated with air masses from "North America" (regions of high anthropogenic and terrestrial biospheric fluxes associated with much of the United States and the southern half of Canada) and of those associated with air masses from the "Arctic/North Atlantic" (regions of few terrestrial fluxes and oceans associated with the northern half of Canada and the Atlantic Ocean). When the continuous CO2 data are segregated into these two trajectory sectors for the period of observation, air masses originating in the North American sector show a higher CO2 mixing ratio by ˜2 ppm in winter and lower by ˜3 ppm in summer, compared to air masses arriving from the other sector. Furthermore, the continuous Sable Island CO2 measurements show a detectable monthly mean (August/September) diurnal cycle with an amplitude of ˜2 ppm, with a minimum occurring on average around noon local time. Given the timing of the observed diurnal minimum and the lack of vegetation on the island, this indicates that the diurnal pattern observed at Sable Island is a diffused remnant of diurnal cycles transported from the main North American continent. These characteristic details are not captured by the discrete flask sampling program on the island.

  5. 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

  6. A teleconnection between Atlantic sea surface temperature and eastern and central North Pacific tropical cyclones

    NASA Astrophysics Data System (ADS)

    Patricola, Christina M.; Saravanan, R.; Chang, Ping

    2017-01-01

    The El Niño-Southern Oscillation (ENSO) is a major source of seasonal tropical cyclone (TC) predictability in both local and remote ocean basins. Unusually warm eastern-central equatorial Pacific sea surface temperature (SST) during El Niño tends to enhance eastern and central North Pacific (ECNP) TCs and suppress Atlantic TCs. Here we demonstrate that Atlantic SST variability likewise influences remote TC activity in the eastern-central Pacific through a Walker Circulation-type response analogous to the ENSO-Atlantic TC teleconnection, using observations and 27 km resolution tropical channel model (TCM) simulations. Observed and simulated ECNP TC activity is reduced during the positive Atlantic Meridional Mode (AMM), which is characterized by warm northern and cool southern tropical Atlantic SST anomalies, and vice versa during the negative AMM. Large ensembles of TCM simulations indicate that SST variability, rather than internal atmospheric variability, drives extreme ECNP hurricane seasons.

  7. On the Currents and Transports Connected with the Atlantic Meridional Overtuning Circulation in the Subpolar North Atlantic

    DTIC Science & Technology

    2013-08-14

    evaporation, precipitation, and river runoffs and the sea surface salinity (SSS) is restored to the GDEM climatology with a restoring strength V of 15 m/30...In an upper layer, the North Atlantic Current (NAC), along with recircu- lations, carries warm and saline water from the Gulf Stream into the SPNA. An...extends meridionally from 28S to the Fram Strait at 80N. No inflow/ outflow is prescribed at the northern and southern boundaries. Within a buffer zone

  8. Cooling of the North Atlantic by Saharan Dust

    NASA Technical Reports Server (NTRS)

    Lau, K. M.; Kim, K. M.

    2007-01-01

    Using aerosol optical depth, sea surface temperature, top-of-the-atmosphere solar radiation flux, and oceanic mixed-layer depth from diverse data sources that include NASA satellites, NCEP reanalysis, in situ observations, as well as long-term dust records from Barbados, we examine the possible relationships between Saharan dust and Atlantic sea surface temperature. Results show that the estimated anomalous cooling pattern of the Atlantic during June 2006 relative to June 2005 due to attenuation of surface solar radiation by Saharan dust remarkably resemble observations, accounting for approximately 30-40% of the observed change in sea surface temperature. Historical data analysis show that there is a robust negative correlation between atmospheric dust loading and Atlantic SST consistent with the notion that increased (decreased) Saharan dust is associated with cooling (warming) of the Atlantic during the early hurricane season (July- August-September).

  9. 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.

  10. The role of clouds in driving North Atlantic multi-decadal climate variability in observations and models

    NASA Astrophysics Data System (ADS)

    Clement, A. C.; Bellomo, K.; Murphy, L.

    2013-12-01

    Large scale warming and cooling periods of the North Atlantic is known as the Atlantic Multidecadal Oscillation (AMO). The pattern of warming and cooling in the North Atlantic Ocean over the 20th century that has a characteristic spatial structure with maximum warming in the mid-latitudes and subtropics. This has been most often attributed to changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC), which in turn affects poleward heat transport. A recent modeling study by Booth et al. (2012), however, suggested that aerosols can explain both the spatial pattern and temporal history of Atlantic SST through indirect effects of aerosols on cloud cover; although this idea is controversial (Zhang et al., 2013). We have found observational evidence that changes in cloud amount can drive SST changes on multi-decadal timescale. We hypothesize that a positive local feedback between SST and cloud radiative effect amplifies SST and gives rise to the observed pattern of SST change. During cool North Atlantic periods, a southward shift of the ITCZ strengthens the trade winds in the tropical North Atlantic and increases low-level cloud cover, which acts to amplify the SST cooling in the North Atlantic. During warm periods in the North Atlantic, the opposite response occurs. We are testing whether the amplitude of this feedback is realistically simulated in the CMIP5 models, and whether inter-model differences in the amplitude of the feedback can explain differences in model simulations of Atlantic multi-decadal variability.

  11. Abrupt transitions in the NAO control of explosive North Atlantic cyclone development

    NASA Astrophysics Data System (ADS)

    Gómara, Iñigo; Rodríguez-Fonseca, Belén; Zurita-Gotor, Pablo; Ulbrich, Sven; Pinto, Joaquim G.

    2016-11-01

    Explosive cyclones are intense extra-tropical low pressure systems featuring large deepening rates. In the Euro-Atlantic sector, they are a major source of life-threatening weather impacts due to their associated strong wind gusts, heavy precipitation and storm surges. The wintertime variability of the North Atlantic cyclonic activity is primarily modulated by the North Atlantic Oscillation (NAO). In this study, we investigate the interannual and multi-decadal variability of explosive North Atlantic cyclones using track density data from two reanalysis datasets (NCEP and ERA-40) and a control simulation of an atmosphere/ocean coupled General Circulation Model (GCM—ECHAM5/MPIOM1). The leading interannual and multi-decadal modes of variability of explosive cyclone track density are characterized by a strengthening/weakening pattern between Newfoundland and Iceland, which is mainly modulated by the NAO at both timescales. However, the NAO control of interannual cyclone variability is not stationary in time and abruptly fluctuates during periods of 20-25 years long both in NCEP and ECHAM5/MPIOM1. These transitions are accompanied by structural changes in the leading mode of explosive cyclone variability, and by decreased/enhanced baroclinicity over the sub-polar/sub-tropical North Atlantic. The influence of the ocean is apparently important for both the occurrence and persistence of such anomalous periods. In the GCM, the Atlantic Meridional Overturning Circulation appears to influence the large-scale baroclinicity and explosive cyclone development over the North Atlantic. These results permit a better understanding of explosive cyclogenesis variability at different climatic timescales and might help to improve predictions of these hazardous events.

  12. Mechanisms of the atmospheric response to North Atlantic multidecadal variability: a model study

    NASA Astrophysics Data System (ADS)

    Msadek, Rym; Frankignoul, Claude; Li, Laurent Z. X.

    2011-04-01

    The atmospheric circulation response to decadal fluctuations of the Atlantic meridional overturning circulation (MOC) in the IPSL climate model is investigated using the associated sea surface temperature signature. A SST anomaly is prescribed in sensitivity experiments with the atmospheric component of the IPSL model coupled to a slab ocean. The prescribed SST anomaly in the North Atlantic is the surface signature of the MOC influence on the atmosphere detected in the coupled simulation. It follows a maximum of the MOC by a few years and resembles the model Atlantic multidecadal oscillation. It is mainly characterized by a warming of the North Atlantic south of Iceland, and a cooling of the Nordic Seas. There are substantial seasonal variations in the geopotential height response to the prescribed SST anomaly, with an East Atlantic Pattern-like response in summer and a North Atlantic oscillation-like signal in winter. In summer, the response of the atmosphere is global in scale, resembling the climatic impact detected in the coupled simulation, albeit with a weaker amplitude. The zonally asymmetric or eddy part of the response is characterized by a trough over warm SST associated with changes in the stationary waves. A diagnostic analysis with daily data emphasizes the role of transient-eddy forcing in shaping and maintaining the equilibrium response. We show that in response to an intensified MOC, the North Atlantic storm tracks are enhanced and shifted northward during summer, consistent with a strengthening of the westerlies. However the anomalous response is weak, which suggests a statistically significant but rather modest influence of the extratropical SST on the atmosphere. The winter response to the MOC-induced North Atlantic warming is an intensification of the subtropical jet and a southward shift of the Atlantic storm track activity, resulting in an equatorward shift of the polar jet. Although the SST anomaly is only prescribed in the Atlantic ocean

  13. The effect of the Mediterranean Overflow Water on the North Atlantic

    NASA Astrophysics Data System (ADS)

    Aldama Campino, Aitor; Döös, Kristofer

    2015-04-01

    The Mediterranean Overflow Water is created due to an excess of evaporation over precipitation and river runoffs in the Mediterranean Sea. As a result, the incoming surface waters from the Atlantic become denser and saltier. These waters return to the Atlantic through Gibraltar Strait and start mixing with the surrounding waters in the vicinity of the Gulf of Cadiz forming a warm and saline tongue of water, which spreads westward. In this exchange of waters between the Atlantic and the Mediterranean, other magnitudes such as heat and salt are transported. In the last case, the salt transport between the two basins shows a variability with a period of few decades. These oscillations produce two different states, one where the Mediterranean exports salt to the Atlantic and another where the Mediterranean imports salt from it. The Mediterranean-Atlantic system alternates these two states. The aim of this study is to analyse the effects of these multidecadal oscillations on the North Atlantic. This study is performed using data from the climate model EC-EARTH run under pre-industrial conditions, where the greenhouse gas forcing is constant. Different magnitudes such as the total salt and volume transport through Gibraltar Strait, salinity profiles in the vicinity of the Gulf of Cadiz, the net freshwater fluxes in the Mediterranean basin are studied. The analysis of the total salt transport through Gibraltar show periods where salt is imported from the Atlantic and vice versa. Our guess is that the Mediterranean Sea acts as a reservoir which alternates between exporting and importing salt from the North Atlantic through the strait. The impact of this salt transport in Gibraltar on the total salt transport of the Atlantic is studied. The results show a larger impact of the outgoing salt transport on the total Atlantic salt transport north of Gibraltar strait (in a region between 40°N-50°N). These results oppose the ones obtained when the impact of the outgoing salt

  14. 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.

  15. 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.

  16. 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.

  17. Glacier response to North Atlantic climate variability during the Holocene

    NASA Astrophysics Data System (ADS)

    Balascio, N. L.; D'Andrea, W. J.; Bradley, R. S.

    2015-12-01

    Small glaciers and ice caps respond rapidly to climate variations, and records of their past extent provide information on the natural envelope of past climate variability. Millennial-scale trends in Holocene glacier size are well documented and correspond with changes in Northern Hemisphere summer insolation. However, there is only sparse and fragmentary evidence for higher-frequency variations in glacier size because in many Northern Hemisphere regions glacier advances of the past few hundred years were the most extensive and destroyed the geomorphic evidence of ice growth and retreat during the past several thousand years. Thus, most glacier records have been of limited use for investigating centennial-scale climate forcing and feedback mechanisms. Here we report a continuous record of glacier activity for the last 9.5 ka from southeast Greenland derived from high-resolution measurements on a proglacial lake sediment sequence. Physical and geochemical parameters show that the glaciers responded to previously documented Northern Hemisphere climatic excursions, including the "8.2 ka" cooling event, the Holocene Thermal Maximum, Neoglacial cooling, and 20th century warming. In addition, the sediments indicate centennial-scale oscillations in glacier size during the late Holocene. Beginning at 4.1 ka, a series of abrupt glacier advances occurred, each lasting ~100 years and followed by a period of retreat, that were superimposed on a gradual trend toward larger glacier size. Thus, while declining summer insolation caused long-term cooling and glacier expansion during the late Holocene, climate system dynamics resulted in repeated episodes of glacier expansion and retreat on multi-decadal to centennial timescales. These episodes coincided with ice rafting events in the North Atlantic Ocean and periods of regional ice cap expansion, which confirms their regional significance and indicates that considerable glacier activity on these timescales is a normal feature of

  18. 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.

  19. 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.

  20. Impacts of the QBO on the North Atlantic and Mediterranean storm tracks: An energetic perspective

    NASA Astrophysics Data System (ADS)

    Asbaghi, Ghorban; Joghataei, Mohammad; Mohebalhojeh, Ali R.

    2017-01-01

    Impacts of the quasi-biennial oscillation (QBO) on the energetics of the North Atlantic and Mediterranean storm tracks are discussed. The daily National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis data for the period 1953-2015 are used to evaluate the spatial distribution of eddy kinetic energy (EKE) and the main factors involved in generation, conversion, and propagation of the EKE in the westerly and easterly phases of the QBO. Results are presented for both early and late winter to uncover intraseasonal variations of the impact. It is shown that the QBO exerts a marked influence on the Mediterranean storm track in early winter, which is of the same order of its impact on the North Atlantic storm track. Further, the impact on the Mediterranean storm track is rather local in early winter but more influenced by variations in the North Atlantic storm track in late winter.

  1. 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.

  2. A Climatological Perspective on U.S. Rainfall and North Atlantic Tropical Cyclones

    NASA Astrophysics Data System (ADS)

    Luitel, B. N.; Villarini, G.; Vecchi, G. A.; Murakami, H.; Zhang, W.

    2015-12-01

    North Atlantic tropical cyclones (TCs) are major contributors to annual precipitation over large areas of the United States, in particular along the Gulf Coast, Florida and the Eastern Seaboard. Studies have shown large inter-annual as well as decadal variations in rainfall associated with TCs, but there is limited evidence concerning the possible factors controlling these variations. In this study we focus on rainfall associated with North Atlantic TCs and its impact over the continental United States during the period of 1948 - 2013. Results are based on gridded daily rainfall provided by the Climate Prediction Center (Daily US Unified Gauge-Based Analysis of Precipitation). Based on this 66-year record, we will show the areas of the United States that are more susceptible to TC-rainfall. Moreover, we will also examine the role played by different climate phenomena (e.g., the North Atlantic Oscillation, El Nino - Southern Oscillation) in controlling the interannual variability of TC rainfall

  3. 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.

  4. Edge Driven Convection along the Eastern North American Margin from Ambient Noise Tomography

    NASA Astrophysics Data System (ADS)

    Savage, B. K.; Covellone, B. M.; Shen, Y.

    2014-12-01

    The eastern North American margin is the result of nearly a billion years of continental collision and rifting. Here we present a new wave speed model of the eastern North American margin from full-wave ambient noise tomography with the USArray data. Transitions in lithosphere thickness occur at the intersection of the North American craton to the west and the Atlantic Ocean basin. We observe a continuous low wave speed feature at the edge of the continent between depths of 120 and 190 km into the Earth. The dramatic change in lithosphere thickness at this boundary may drive asthenosphere upwelling along the edge of the continent. Edge driven convection is hypothesized as the result of induced mantle convection due to plate motions and abrupt thickness changes in the lithosphere. Additionally, the insulating effect of large continents has been hypothesized to result in the formation of "hot" convection cells along their boundaries. Localized higher amplitude slow anomalies are seen adjacent to Maryland and Virginia and offshore of South Carolina and Georgia; these may be the locales of enhanced edge driven convection that exploits weaknesses in the lithosphere from past episodes of volcanism. Additionally, a large slow wave speed anomaly beneath New England continues offshore aligned with the New England Seamount chain, and is possibly a remnant of the Monteregian hot spot active 100 - 120 Ma. Slow wave speeds extending to depths greater than 50 km reflect thickened continental crust in the Appalachians.

  5. Higher Laurentide and Greenland ice sheets strengthen the North Atlantic ocean circulation

    NASA Astrophysics Data System (ADS)

    Gong, Xun; Zhang, Xiangdong; Lohmann, Gerrit; Wei, Wei; Zhang, Xu; Pfeiffer, Madlene

    2015-07-01

    During the last glacial-interglacial cycle, changes in the large-scale North Atlantic ocean circulation occurred, and at the same time topography of the Laurentide and Greenland ice sheets also varied. In this study, we focus on detecting the changes of the North Atlantic gyres, western boundary current, and the Atlantic meridional overturning circulation (AMOC) corresponding to different Laurentide and Greenland ice sheet topographies. Using an Earth System Model, we conducted simulations for five climate states with different ice sheet topographies: Pre-industrial, Mid Holocene, Last Glacial Maximum, 32 kilo years before present and Eemian interglacial. Our simulation results indicate that higher topographies of the Laurentide and Greenland ice sheets strengthen surface wind stress curl over the North Atlantic ocean, intensifying the subtropical and subpolar gyres and the western boundary currents. The corresponding decrease in sea surface height from subtropical to subpolar favors a stronger AMOC. An offshore shift of the Gulf Stream is also identified during the glacial periods relative to that during the Pre-industrial due to lower sea levels, explaining a weaker glacial Gulf Stream detected in proxy data. Meanwhile, the North Atlantic gyres and AMOC demonstrate a positively correlated relation under each of the climate conditions with higher ice sheets.

  6. 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.

  7. North Atlantic meridional overturning circulation variations from GRACE ocean bottom pressure anomalie

    NASA Astrophysics Data System (ADS)

    Landerer, F. W.; Wiese, D. N.; Bentel, K.; Boening, C.; Watkins, M. M.

    2015-12-01

    The important role of the North-Atlantic Meridonal Overturning Circulation (AMOC) for regional as well as global climate is well recognized. Concerns about potential future AMOC changes imply the need for a continuous, large-scale observation capability to detect any such changes on interannual to decadal time scales. Here, we present the first measurements of lower North-Atlantic-Deep-Water (LNADW) monthly transport changes using only space-based time-variable gravity observations from Gravity Recovery and Climate Experiment (GRACE) satellites, continuously covering the time period from 2003 until now. Improved monthly gravity field retrievals allow the detection of North Atlantic interannual bottom pressure anomalies and yield LNADW transport estimates that are in good agreement with those from the ocean in-situ RAPID-MOCA array at 26.5N. 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 of -20 mm-H2O, implying a southward volume transport anomaly in that layer of approximately -5.5 Sv. Our results highlight the efficacy of space-gravimetry to observe and detect meridional ocean transport variations that can potentially be retrieved over all latitude ranges in the Atlantic.

  8. Enhanced North Atlantic deep convection preceding Heinrich 1 glacial ice sheet destabilization

    NASA Astrophysics Data System (ADS)

    Seidenkrantz, Marit-Solveig; Kuijpers, Antoon; Lindgreen, Holger

    2015-04-01

    The Labrador Sea is a crucial center of action for North Atlantic meridional overturning circulation. This region is characterized in winter by strong cold and dry winds from land or ice surfaces inducing large heat and moisture fluxes at the ocean-atmosphere interface. Particularly in late winter these conditions favor deep-convection processes leading to the formation of a relatively homogeneous and oxygen-rich intermediate water mass (Labrador Sea Water, LSW) spreading to other parts of the North Atlantic at water depths between about 1,000 and 2,000 m. Sedimentary records from the Labrador Sea have previously indicated here the presence of North Atlantic Deep Water during periods in between glacial ('Heinrich') ice-rafting events. The present sediment core investigation based on clay mineralogical analysis and study of the benthic foraminiferal fauna shows a significant oxygenation event at 18000 cal.yrs BP recorded both in the Labrador Sea and at the northern margin of Rockall Trough at 2381 m and 1286 m water depth, respectively. We conclude this ventilation pulse to be related to a period of enhanced deep convection and formation of glacial North Atlantic Intermediate Water occupying those parts of the water column presently affected under conditions of strong LSW formation. This ventilation event implies an early, significant re-activation of North Atlantic meridional overturning circulation after the Last Glacial Maximum immediately prior to Heinrich 1 large-scale ice-sheet destabilization. This scenario points to an oceanic trigger mechanism for large-scale glacial iceberg surges around the northern North Atlantic, which involves enhanced northward ocean (sub)surface heat transport and subsequent enhanced bottom melting of floating outlet glaciers and ice shelves.

  9. 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

  10. 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...

  11. Interannual variability of temperature at a depth of 125 meters in the North Atlantic Ocean

    SciTech Connect

    Levitus, S.; Boyer, T.P.; Antonov, J.I.

    1994-10-07

    Analyses of historical ocean temperature data at a depth of 125 meters in the North Atlantic Ocean indicate that from 1950-1990 the subtropical and subartic gyres exhibited linear trends that were opposite in phase. In addition, multivariate analyses of yearly mean temperature anomaly fields between 20{degrees}N and 70{degrees}N in the North Atlantic show a characteristic space-time temperature oscillation from 1947 to 1990. A quasidecadal oscillation, first-identified at Ocean Weather Station C, is part of a basin-wide feature. Gyre and basin-scale variations such as these provide the observational basis for climate diagnostic and modeling studies.

  12. Interannual variability of temperature at a depth of 125 meters in the north atlantic ocean.

    PubMed

    Levitus, S; Antonov, J I; Boyer, T P

    1994-10-07

    Analyses of historical ocean temperature data at a depth of 125 meters in the North Atlantic Ocean indicate that from 1950 to 1990 the subtropical and subarctic gyres exhibited linear trends that were opposite in phase. In addition, multivariate analyses of yearly mean temperature anomaly fields between 20 degrees N and 70 degrees N in the North Atlantic show a characteristic space-time temperature oscillation from 1947 to 1990. A quasidecadal oscillation, first identified at Ocean Weather Station C, is part of a basin-wide feature. Gyre and basin-scale variations such as these provide the observational basis for climate diagnostic and modeling studies.

  13. 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.

  14. 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

  15. 14 CFR Appendix C to Part 91 - Operations in the North Atlantic (NAT) Minimum Navigation Performance Specifications (MNPS) Airspace

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 2 2012-01-01 2012-01-01 false Operations in the North Atlantic (NAT) Minimum Navigation Performance Specifications (MNPS) Airspace C Appendix C to Part 91 Aeronautics and... North Atlantic (NAT) Minimum Navigation Performance Specifications (MNPS) Airspace Section 1 NAT...

  16. 14 CFR Appendix C to Part 91 - Operations in the North Atlantic (NAT) Minimum Navigation Performance Specifications (MNPS) Airspace

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 2 2014-01-01 2014-01-01 false Operations in the North Atlantic (NAT) Minimum Navigation Performance Specifications (MNPS) Airspace C Appendix C to Part 91 Aeronautics and... North Atlantic (NAT) Minimum Navigation Performance Specifications (MNPS) Airspace Section 1 NAT...

  17. 14 CFR Appendix C to Part 91 - Operations in the North Atlantic (NAT) Minimum Navigation Performance Specifications (MNPS) Airspace

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 2 2013-01-01 2013-01-01 false Operations in the North Atlantic (NAT) Minimum Navigation Performance Specifications (MNPS) Airspace C Appendix C to Part 91 Aeronautics and... North Atlantic (NAT) Minimum Navigation Performance Specifications (MNPS) Airspace Section 1 NAT...

  18. 14 CFR Appendix C to Part 91 - Operations in the North Atlantic (NAT) Minimum Navigation Performance Specifications (MNPS) Airspace

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 2 2011-01-01 2011-01-01 false Operations in the North Atlantic (NAT) Minimum Navigation Performance Specifications (MNPS) Airspace C Appendix C to Part 91 Aeronautics and... North Atlantic (NAT) Minimum Navigation Performance Specifications (MNPS) Airspace Section 1 NAT...

  19. 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).

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. 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.

  5. Strategic Implications of the North American Free Trade Agreement (NAFTA)

    DTIC Science & Technology

    1993-04-01

    Follow-on bilateral agreements with the United States brought investment and swift growth in exports. When Carlos Salinas de Gortari was elected...Free Trade Agreement (FTA), 5 President Salinas , joined Canadian Prime Minister Mulroney and U.S. President Bush in formally proposing the North...Mexico had completed negotiation of the North American Free Trade Agreement. President Bush, Prime Minister Mulroney, and President Salinas signed the

  6. 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.

  7. 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.

  8. 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

  9. Variability of the North Atlantic Current: high resolution model data versus in situ measurements

    NASA Astrophysics Data System (ADS)

    Breckenfelder, Tilia; Rhein, Monika; Roessler, Achim; Behrens, Erik; Böning, Claus; Biastoch, Arne; Mertens, Christian

    2015-04-01

    The North Atlantic Current (NAC) provides an important heat source for the relatively warm winters in Western Europe by bringing warm and salty tropical/subtropical water into the subpolar gyre of the North Atlantic. The NAC is the northward extension of the Gulfstream and its warm and salty water form the warm upper branch of the Atlantic Meridional Overturning Circulation (AMOC). The NAC crosses the Mid-Atlantic Ridge (MAR) via the Charlie-Gibbs, Faraday and Maxwell Fracture Zones between 47° and 53°N. Along that section an array of four inverted echo sounders with bottom pressure sensors (PIES) are deployed since 2006 and combined with altimetry to quantify the NAC transport and its variability. The observed transport time series is compared to the high resolution output of the VIKING20 model, a 1/20° North Atlantic model which is embedded in a global model of 1/4° resolution (ORCA25) via a two-way nesting. We compare the horizontal and vertical flow fields, the mean transport and the variability as well as the water mass characteristics.

  10. Synchronous response of marine plankton ecosystems to climate in the Northeast Atlantic and the North Sea

    NASA Astrophysics Data System (ADS)

    Goberville, Eric; Beaugrand, Gregory; Edwards, Martin

    2014-01-01

    Over the last few decades, global warming has accelerated both the rate and magnitude of changes observed in many functional units of the Earth System. In this context, plankton are sentinel organisms because they are sensitive to subtle levels of changes in temperature and might help in identifying the current effects of climate change on pelagic ecosystems. In this paper, we performed a comparative approach in two regions of the North Atlantic (i.e. the Northeast Atlantic and the North Sea) to explore the relationships between changes in marine plankton, the regional physico-chemical environment and large-scale hydro-climatic forcing using four key indices: the North Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO), the East Atlantic (EA) pattern and Northern Hemisphere Temperature (NHT) anomalies. Our analyses suggest that long-term changes in the states of the two ecosystems were synchronous and correlated to the same large-scale hydro-climatic variables: NHT anomalies, the AMO and to a lesser extent the EA pattern. No significant correlation was found between long-term ecosystem modifications and the state of the NAO. Our results suggest that the effect of climate on these ecosystems has mainly occurred in both regions through the modulation of the thermal regime.

  11. 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…

  12. 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…

  13. Variation among early North American crania.

    PubMed

    Jantz, R L; Owsley, D W

    2001-02-01

    The limited morphometric work on early American crania to date has treated them as a single, temporally defined group. This paper addresses the question of whether there is significant variability among ancient American crania. A sample of 11 crania (Spirit Cave, Wizards Beach, Browns Valley, Pelican Rapids, Prospect, Wet Gravel male, Wet Gravel female, Medicine Crow, Turin, Lime Creek, and Swanson Lake) dating from the early to mid Holocene was available. Some have recent accelerator mass spectrometry (AMS) dates, while others are dated geologically or archaeologically. All are in excess of 4500 BP, and most are 7000 BP or older. Measurements follow the definitions of Howells [(1973) Cranial variation in man, Cambridge: Harvard University). Some crania are incomplete, but 22 measurements were common to all fossils. Cranial variation was examined by calculating the Mahalanobis distance between each pair of fossils, using a pooled within sample covariance matrix estimated from the data of Howells. The distance relationships among crania suggest the presence of at least three distinct groups: 1) a middle Archaic Plains group (Turin and Medicine Crow), 2) a Paleo/Early Archaic Great Lakes/Plains group (Browns Valley, Pelican Rapids, Lime Creek), and 3) a spatially and temporally heterogeneous group that includes the Great Basin/Pacific Coast (Spirit Cave, Wizards Beach, Prospect) and Nebraska (Wet Gravel specimens and Swanson Lake). These crania were also compared to Howells' worldwide recent sample, which was expanded by including six additional American Indian samples. None of the fossils, except for the Wet Gravel male, shows any particular affinity to recent Native Americans; their greatest similarities are with Europe, Polynesia, or East Asia. Several crania would be atypical in any recent population for which we have data. Browns Valley, Pelican Rapids, and Lime Creek are the most distinctive. They provide evidence for the presence of an early population that

  14. 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.

  15. Vegetation/oceanographic changes in the mid-latitudes of southwestern North Atlantic during the Holocene

    NASA Astrophysics Data System (ADS)

    Naughton, Filipa; Keigwin, Lloyd; Oliveira, Dulce; Desprat, Stephanie; Abrantes, Fatima

    2013-04-01

    The direct correlation between terrestrial (pollen) and marine (planktonic δ18O) proxies from a slope core (KNR 178-2 JPC 32), retrieved in the Cape Hatteras (35°58.58'N, 74°42.77'W, 1006 m), provide substantial information on the Eastern North American vegetation response to the Holocene climate and oceanographic changes of the western North Atlantic. The end of the last glacial-interglacial transition is marked by the gradual replacement of the Boreal forest and herbs by temperate trees reflecting a general warming. Within this overall gradual warming, several abrupt vegetation shifts reveal episodes of relative cool and warm events. The most notorious continental warming of this transition, occurred at around 9650 cal yr BP and is synchronous with the increase of sea surface temperature as revealed by the planktonic foraminifera δ18O. The first maxima of temperate trees expansion, reflecting one of the most warmest events within the Holocene, occurred between 8700 and 7200 cal yr BP. Within this period 4 abrupt vegetation and hydrological changes suggest centennial scale returning cool conditions, being the most extreme detected at around 8400 cal yr BP. Between 7200 and 5300 cal yr BP temperate trees were partially replaced by hemlock suggesting a relative cool episode. The re-expansion of temperate trees marking a climatic warming is detected between 5300 and 2500 cal yr BP. Within this interval it is detected an important change in both vegetation and hydrology, marking a relative long lasting cooling between 4100 and 3550 cal yr BP. Finally the last 2500 cal yr BP is marked by important vegetation and hydrological shifts reflecting important climatic changes.

  16. Hydrogen peroxide in the marine atmospheric boundary layer during the Atlantic Stratocumulus Transition Experiment/Marine Aerosol and Gas Exchange experiment in the eastern subtropical North Atlantic

    NASA Astrophysics Data System (ADS)

    Martin, Daniel; Tsivou, Maria; Bonsang, Bernard; Abonnel, Christian; Carsey, Thomas; Springer-Young, Margie; Pszenny, Alex; Suhre, Karsten

    1997-03-01

    Gas phase H2O2 was measured in surface air on the NOAA ship Malcolm Baldrige from June 8 to 27, 1992 (Julian days 160-179), during the Atlantic Stratocumulus Transition Experiment/Marine Aerosol and Gas Exchange experiment in the eastern subtropical North Atlantic region. Average H2O2 mixing ratios observed were 0.63±0.28 ppbv, ranging between detection limit and 1.5 ppbv. For the entire experiment, only weak or no correlation was found between H2O2 mixing ratio and meteorological parameters (pressure, temperature, humidity, or UV radiation flux) as well as with tracers of continental air masses (CO, black carbon, radon). The average daily H2O2 cycle for the entire period exhibits a maximum of 0.8±0.3 ppbv near sunset and a minimum of 0.4±0.2 ppbv 4-5 hours after sunrise. Several clear H2O2 diurnal variations have been observed, from which a first-order removal rate of about 1×10-5 s-1 for H2O2 can be inferred from nighttime measurements. This rate compares well with those deduced from measurements taken at Cape Grim (Tasmania, 41°S) and during the Soviet-American Gas and Aerosol III experiment (equatorial Pacific Ocean).

  17. 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)

  18. Overview of North American stored product research

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Major locations for stored product research in North America are in Winnipeg, Manitoba, Canada, and Manhattan, Kansas, USA. Recent personnel changes and research areas are reviewed. One of the pressing research areas in the U.S. is reducing the need for fumigations in flour mills and evaluating alte...

  19. 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.

  20. 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.

  1. North Atlantic circulation and reservoir age changes over the past 41,000 years

    NASA Astrophysics Data System (ADS)

    Stern, Joseph V.; Lisiecki, Lorraine E.

    2013-07-01

    on the timing of Atlantic meridional overturning circulation (AMOC) changes during the last deglaciation are fundamental to understanding the climate's rapid response to insolation forcing. However, uncertainty about high-latitude North Atlantic (HLNA) radiocarbon reservoir ages has previously precluded robust age model development for this critical region. HLNA reservoir ages also serve as a proxy for AMOC strength. We present regionally averaged HLNA reservoir ages for 0 to 41 thousand years before the present (kyr BP) based on over 500 radiocarbon dates from 33 North Atlantic cores. An early deglacial increase to >1000 14C yr reservoir ages between 18.5 and 16.5 kyr BP suggests reduced AMOC before peak Heinrich Stadial 1 (HS1) ice-rafted debris (IRD). A rapid decrease in reservoir ages coincident with the IRD maximum at 16 kyr BP indicates strong stratification of the upper water column caused by massive freshwater release.

  2. Distinguishing molecular characteristics of aerosol water soluble organic matter from the 2011 trans-North Atlantic US GEOTRACES cruise

    NASA Astrophysics Data System (ADS)

    Wozniak, A. S.; Willoughby, A. S.; Gurganus, S. C.; Hatcher, P. G.

    2014-08-01

    The molecular characteristics of aerosol organic matter (OM) determines to a large extent its impacts on the atmospheric radiative budget and ecosystem function in terrestrial and aquatic environments, yet the OM molecular details of aerosols from different sources are not well established. Aerosol particulate samples with North American-influenced, North African-influenced, and marine (minimal recent continental influence) air mass back trajectories were collected as part of the 2011 trans-North Atlantic US GEOTRACES cruise and analyzed for their water soluble OM (WSOM) molecular characteristics using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. Principal component analysis (PCA) separated the samples into five groups defined by distinct molecular formula characteristics. An abundance of nitrogen containing compounds with molecular formulas consistent with amino acid derivatives defined the two samples comprising the primary marine group (henceforth referred to as Primary Marine), which suggest a primary marine biological source to their WSOM in spite of their North American-influenced air mass trajectories. A second group of samples (aged marine, henceforth referred to as Aged Marine) with marine air mass trajectories was characterized by an abundance of low O / C (0.15-0.45) sulfur containing compounds consistent with organosulfate compounds formed via secondary aging reactions in the atmosphere. Several samples having North American-influenced air mass trajectories formed another group again characterized by organosulfate and nitrooxyorganosulfate type compounds with higher O / C ratios (0.5-1.0) than the Aged Marine samples reflecting the combustion influence from the North American continent. All the samples with North African-influenced air mass trajectories were grouped together in the PCA and were characterized by a lack of heteroatom (N, S, P) containing molecular formulas covering a wide O / C range (0

  3. Genetic Structure and the North American Postglacial Expansion of the Barnacle, Semibalanus balanoides

    PubMed Central

    O’Brien, Megan A.; Schmidt, Paul S.; Rand, David M.

    2012-01-01

    Population genetic characteristics are shaped by the life-history traits of organisms and the geologic history of their habitat. This study provides a neutral framework for understanding the population dynamics and opportunities for selection in Semibalanus balanoides, a species that figures prominently in ecological and evolutionary studies in the Atlantic intertidal. We used mitochondrial DNA (mtDNA) control region (N = 131) and microsatellite markers (∼40 individuals/site/locus) to survey populations of the broadly dispersing acorn barnacle from 8 sites spanning 800 km of North American coast and 1 site in Europe. Patterns of mtDNA sequence evolution were consistent with larger population sizes in Europe and population expansion at the conclusion of the last ice age, approximately 20 000 years ago, in North America. A significant portion of mitochondrial diversity was partitioned between the continents (φST = 0.281), but there was only weak structure observed from mtDNA within North America. Microsatellites showed significant structuring between the continents (FST = 0.021) as well as within North America (FST = 0.013). Isolation by distance in North America was largely driven by a split between populations south of Cape Cod and all others (P < 10−4). The glacial events responsible for generating allelic diversity at mtDNA and microsatellites may also be responsible for generating selectable variation at metabolic enzymes in S. balanoides. PMID:21885571

  4. Genetic structure and the North American postglacial expansion of the barnacle, Semibalanus balanoides.

    PubMed

    Flight, Patrick A; O'Brien, Megan A; Schmidt, Paul S; Rand, David M

    2012-01-01

    Population genetic characteristics are shaped by the life-history traits of organisms and the geologic history of their habitat. This study provides a neutral framework for understanding the population dynamics and opportunities for selection in Semibalanus balanoides, a species that figures prominently in ecological and evolutionary studies in the Atlantic intertidal. We used mitochondrial DNA (mtDNA) control region (N = 131) and microsatellite markers (∼40 individuals/site/locus) to survey populations of the broadly dispersing acorn barnacle from 8 sites spanning 800 km of North American coast and 1 site in Europe. Patterns of mtDNA sequence evolution were consistent with larger population sizes in Europe and population expansion at the conclusion of the last ice age, approximately 20 000 years ago, in North America. A significant portion of mitochondrial diversity was partitioned between the continents (ϕ(ST) = 0.281), but there was only weak structure observed from mtDNA within North America. Microsatellites showed significant structuring between the continents (F(ST) = 0.021) as well as within North America (F(ST) = 0.013). Isolation by distance in North America was largely driven by a split between populations south of Cape Cod and all others (P < 10(-4)). The glacial events responsible for generating allelic diversity at mtDNA and microsatellites may also be responsible for generating selectable variation at metabolic enzymes in S. balanoides.

  5. 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.

  6. Evaluation of CMIP5 20th century simulations for North American climate

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    The Coupled Model Inter-comparison Project phase 5 (CMIP5) provides an unprecedented set of model results for improved understanding of climate processes and feedbacks, anthropogenic impacts and potential future changes. In particular, evaluations of the model historical simulations are crucial for assessing model fidelity and are a necessary prerequisite for instilling confidence in their future projections. This study synthesizes results from the NOAA CMIP5 Task Force on 20th century model evaluations for the climate of North America and related climate processes. We evaluate the models for a range of features at spatial scales from continental to regional and for a variety of time scales from intra-seasonal to multi-decadal variability and teleconnections with North American climate. In general the models capture the main features of North American climate including seasonal precipitation, air temperature and sea surface temperature. The hydrological cycle is also reasonably well simulated for the main characteristics of atmospheric moisture convergence and seasonality of the surface water budget but the latter is subject to the biases in precipitation. The spatial distribution of growing season length and number of frost days are generally well simulated, with biases highest in western regions. The frequency of hydroclimate extreme events is not well represented by the models. The skill of the models in representing climatologies of regional processes, such as the Great Plains low-level jet, the North American monsoon and cool season North Atlantic extra-tropical cyclones, is variable and can often be attributed to model resolution. In terms of climate variability, the multi-model ensemble does reasonably well at reproducing observed variability in several aspects, but does less well at capturing observed teleconnections. For intra-seasonal variability, almost half of the models examined can reproduce observed variability in the eastern Pacific and most models

  7. The Response of the Indian Monsoon to North Atlantic Freshwater Forcing

    NASA Astrophysics Data System (ADS)

    Morrill, C.; Otto-Bliesner, B. L.

    2006-12-01

    Paleoclimate records indicate that during some past abrupt climate changes, such as Dansgaard-Oeschger cycles and the 8.2 ka event, the Indian monsoon weakened and temperatures in the North Atlantic fell. It has been hypothesized that pulses of freshwater added to the North Atlantic could have led to this remote climate response in Asia. However, the physical mechanisms for the teleconnection have yet to be determined. To test this hypothesis, we present results from two experiments using the National Center for Atmospheric Research (NCAR) coupled Community Climate System Model, version 3. In these experiments, we applied a 1 Sverdrup (1x106 m3/s) freshwater hosing over the North Atlantic between 50 and 70 degrees N for 100 years. The two experiments used boundary conditions relevant for 8.5 ka and 21 ka (Last Glacial Maximum). Both simulations show a statistically significant decrease in summer precipitation over India following freshwater addition to the North Atlantic. Precipitation in June-July-August decreases 40 % in the 21 ka simulation and 20 % in the 8.5 ka simulation. We will discuss whether these simulations provide support for any of the proposed pathways for the teleconnection. These include: an increase in Eurasian snowcover, an increase in sea surface temperatures in the Indian Ocean, or a reduction in the temperature gradient across the tropical Pacific.

  8. Surface temperatures of the Mid-Pliocene North Atlantic Ocean: Implications for future climate

    USGS Publications Warehouse

    Dowsett, Harry J.; Chandler, Mark A.; Robinson, Marci 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.

  9. 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.

  10. Climate change impact on seaweed meadow distribution in the North Atlantic rocky intertidal

    PubMed Central

    Jueterbock, Alexander; Tyberghein, Lennert; Verbruggen, Heroen; Coyer, James A; Olsen, Jeanine L; Hoarau, Galice

    2013-01-01

    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

  11. Freshwater variations in the North Atlantic from in situ salinity measurements

    NASA Astrophysics Data System (ADS)

    Boyer, T.; Levitus, S.; Antonov, J.; Locarnini, R.; Garcia, H.; Mishonov, A.

    2006-12-01

    Salinity data from bottle samples, CTD casts, moored buoys, profiling float, Towed CTDs, gliders and drifting buoys are used to calculate variations in freshwater in the North Atlantic Ocean (0-80N) for the period 1955- 2006. Data from the World Ocean Database 2005 (WOD05) are averaged over running 5-year periods (pentads) after the annual cycle is removed by subtracting the monthly climatological salinity. The climatological salinity fields used are from the World Ocean Atlas 2005 (WOA05). From these salinity anomaly fields, freshwater anomaly fields are calculated for different portions of the North Atlantic Ocean. As previously reported, the upper 2000 meters of thesubpolar North Atlantic and Nordic Seas experienced a large increase of freshwater between the late 1960s and the early 1990s. After reaching a peak around 1991-1995 pentad, this area has experienced a large and steady decrease in freshwater which continues through the first half of 2006. The North Atlantic as a whole has experienced a decrease of freshwater over the time period of the study over the top 1500 meters of the water column. Different depth layers in the water column are studied to ascertain at which layers the change in freshwater is occuring.

  12. Regional model simulation of the North Atlantic cyclone Caroline and comparisons with satellite data

    NASA Astrophysics Data System (ADS)

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

    2003-03-01

    An individual regional model simulation of cyclone Caroline has been carried out to study water cycle components over the North Atlantic Ocean. The uncertainties associated with quantitative estimates of the water cycle components are highlighted by a comparison of the model results with SSM/I (Special Sensor Microwave Imager) satellite data.

  13. 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…

  14. 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.

  15. 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.

  16. Optimum multiparameter analysis of the water mass structure in the western North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Hinrichsen, Hans-Harald; Tomczak, Matthias

    1993-06-01

    Hydrographic data of temperature, salinity, oxygen, nitrate, phosphate, and silicate at 81 stations with 435 samples on 3 sections between the Azores, the Grand Banks of Newfoundland, and the Bermuda Islands are used to determine the mixing of water masses by optimum multiparameter analysis over the depth range 100-1500 m. The method optimally utilizes all information from our hydrographic data set by solving an overdetermined set of linear mixing equations for all parameters using the method of least squares residuals. It is shown that the method gives quantitative information on the influence of the various water masses of the western North Atlantic. The Gulf Stream and the North Atlantic Current appear as broad bands transporting large amounts of Western North Atlantic Central Water at their warm flank. Western Subarctic Intermediate Water and Shelf Water supplied by the Labrador Current and containing significant amounts of Labrador Current Water are found on their inshore side. The area of the Azores front is found in the vicinity of the Comer Seamounts, where the uniform water mass distribution of the Sargasso Sea changes into a more complex structure that reflects the influence of water masses originating in the Labrador Sea. Small-scale structures, like eddies or Gulf Stream rings, are also detectable by this analysis method. Comparison with dynamic height analysis supports the circulation pattern of the North Atlantic Current as a continuation of the Gulf Stream, and of the southeastward flowing Azores Current originating in the area of the Southeast Newfoundland Rise.

  17. 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...

  18. 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.

  19. 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...

  20. 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.

  1. 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

  2. Evaluation of the heat balance constituents of the upper mixed layer in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Polonsky, A. B.; Sukhonos, P. A.

    2016-11-01

    Different physical mechanisms which cause interannual and interdecadal temperature anomalies in the upper mixed layer (UML) of the North Atlantic are investigated using the data of ORA-S3 reanalysis for the period of 1959-2011. It is shown that the annual mean heat budget in UML is mainly caused by the balance between advective heat transfer and horizontal turbulent mixing (estimated as a residual term in the equation of thermal balance). The local UML temperature change and contribution from the heat fluxes on the lower boundary of the UML to the heat budget of the upper layer are insignificant for the time scale under consideration. The contribution of the heat fluxes on the upper UML boundary to the low-frequency variability of the upper layer temperature in the whole North Atlantic area is substantially less than 30%. Areas like the northwestern part of the Northern Subtropical Anticyclonic Gyre (NSAG), where their contribution exceeds 30-60%, are exceptions. The typical time scales of advective heat transfer variability are revealed. In the NSAG area, an interannual variability associated with the North Atlantic Oscillation dominates, while in the North Atlantic subpolar gyre, an interdecadal variability of advective transfers with periods of more than 30 years prevails.

  3. Cenozoic unconformities and depositional supersequences of North Atlantic continental margins: Testing the Vail model

    NASA Astrophysics Data System (ADS)

    Poag, C. Wylie; Ward, Lauck W.

    1987-02-01

    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.

  4. 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.

  5. Near-Inertial and Thermal Upper Ocean Response to Atmospheric Forcing in the North Atlantic Ocean

    DTIC Science & Technology

    2010-06-01

    water is then subducted as the ocean restratifies during spring, and advected throughout the subtropical gyre by the large scale wind driven circulation...Luther, and W. C. Patzert, 1992: The heat budget in the north atlantic subtropical frontal zone . J. Geophys. Res., 97 (C11), 17 947–17 959. 131 Price, J

  6. 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 Atlantic Right Whales. 224.105 Section 224.105 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE MARINE MAMMALS ENDANGERED...

  7. 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 Atlantic Right Whales. 224.105 Section 224.105 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE MARINE MAMMALS ENDANGERED...

  8. Soviet Assessments of North American Air Defense

    DTIC Science & Technology

    1986-06-01

    London: Brassey ’ s Defense Publications). Jacobs, John J. (1983). "SAGE Overview." Annals of the History of Comotir. Vol. 5, No. 3, 323-28. -113- Kalugin...U.S. Early Warning Technology. MIT Center for International Studies, paper prepared for the Defense Advanced Research Projects Agency. Peresada, S . A...OF NCIH J N2 991 AMERICAN AIR DEFENSE John W. R. Lepingwell Research Report No. 86-2 Department of Political Science and Center for International

  9. 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.

  10. Medicinal history of North American Veratrum.

    PubMed

    Chandler, Christopher M; McDougal, Owen M

    2014-09-01

    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.

  11. 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

  12. 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.

  13. 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

  14. Implementing the North American Industry Classification System at BLS.

    ERIC Educational Resources Information Center

    Walker, James A.; Murphy, John B.

    2001-01-01

    The United States, Canada, and Mexico developed the North American Industry Classification System, which captures new and emerging industries, uses a unified concept to define industries, and is a consistent and comparable tool for measuring the nations' economies. Despite initial conversion difficulties, the new system will be a more accurate way…

  15. 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

  16. 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…

  17. 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…

  18. Stresses and Strains within the "Stable" North American Plate

    NASA Technical Reports Server (NTRS)

    Engeln, Joe

    1995-01-01

    This paper presents a final report on "Stresses and Strains within the "Stable" North American Plate". The topics include: 1) Strain rates near the New Madrid seismic zone; 2) Signal Processing of intermediate term data; and 3) Transform fault stresses and strains. The paper also includes graphs of the stress and strain distributions.

  19. 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

  20. 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…

  1. 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...

  2. 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…

  3. 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…

  4. 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.…

  5. The Graduate Teaching Assistant (GTA): Lessons from North American Experience

    ERIC Educational Resources Information Center

    Park, Chris

    2004-01-01

    The employment of graduate students on a part-time basis to help with the teaching of undergraduates is growing in the UK and many higher education institutions are confronted with challenges about how best to do this. UK institutions have much to learn from North American experience of appointing graduate teaching assistants (GTAs), and this…

  6. 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.

  7. 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.

  8. The 2007 North Atlantic spring bloom in operational analysis from the TOPAZ system

    NASA Astrophysics Data System (ADS)

    Samuelsen, A.; Bertino, L.; Hansen, C.

    2009-02-01

    A reanalysis of the North Atlantic spring bloom in 2007 was produced using the real-time analyses from the TOPAZ (Towards an Operational Prediction system for the North Atlantic European coastal Zones) North Atlantic and Arctic forecasting system. The TOPAZ system uses a hybrid coordinate general circulation ocean model and assimilates physical observations: sea surface anomalies, sea surface temperatures, and sea-ice concentrations using the Ensemble Kalman Filter. This ocean model was coupled to an ecosystem model, NORWECOM (Norwegian Ecological Model System), and the TOPAZ-NORWECOM coupled model was run throughout the spring and summer of 2007. The ecosystem model was run online, restarting from analyzed physical fields (result after data assimilation) every 7 days. Biological variables were not assimilated in the model. The forecast was compared to remotely sensed chlorophyll and in-situ data. The impact of physical data assimilation on the ecosystem model was determined by comparing the results to those from a model without assimilation of physical data. The regions of focus are the North Atlantic and the Arctic Ocean. The results show that the model reproduces a realistic annual cycle, but the chlorophyll concentrations tend to be too low during winter and spring and too high during summer. Surface nutrients on the other hand are generally too low throughout the year. Assimilation of physical variables does not affect the results from the ecosystem model significantly. The differences between the weekly mean values of chlorophyll are normally within 5-10% during the summer months, and the maximum difference of ~20% occurs in the Arctic, also during summer. Special attention was paid to the nutrient input from the North Atlantic to the Nordic Seas and the impact of ice-assimilation on the ecosystem. The ice-assimilation increased the phytoplankton concentration: because there was less ice in the assimilation run, this increased both the mixing of nutrients

  9. 76 FR 62802 - North American Electric Reliability Corporation; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-11

    ... 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 Take notice that on September 30, 2011, the North American Electric Reliability Corporation (NERC) filed...

  10. 75 FR 81601 - North American Electric Reliability Corporation; Notice of Compliance Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-28

    ... Energy Regulatory Commission North American Electric Reliability Corporation; Notice of Compliance Filing December 20, 2010. Take notice that on December 1, 2010, North American Electric Reliability Corporation... Violation Severity Levels for Available Transfer Capability Reliability Standards. \\1\\ Mandatory...

  11. 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 11, 2013, the North American Electric Reliability Corporation and SERC Reliability... (FERC or Commission) in Regional Reliability Standard PRC-006-SERC-01--Automatic Underfrequency...

  12. 75 FR 29336 - North American Electric Reliability Corporation; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-25

    ... Energy Regulatory Commission North American Electric Reliability Corporation; Notice of Filing May 18, 2010. Take notice that on May 17, 2010, North American Electric Reliability Corporation (NERC... Infrastructure Protection (CIP) Reliability Standards, in compliance with to the Commission's March 18,...

  13. 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...

  14. Populations estimates of North American shorebirds, 2006

    USGS Publications Warehouse

    Morrison, R.I. Guy; McCaffery, Brian J.; Gill, Robert E.; Skagen, Susan K.; Jones, Stephanie L.; Page, Gary W.; Gratto-Trevor, Cheri L.; Andres, Brad A.

    2006-01-01

    This paper provides updates on population estimates for 52 species of shorebirds, involving 75 taxa, occurring in North America. New information resulting in a changed estimate is available for 39 of the 75 taxa (52%), involving 24 increases and 15 decreases. The preponderance of increased estimates is likely the result of improved estimates rather than actual increases in numbers. Many shorebird species/taxa are considered to be declining: current information on trends indicates negative trends outnumbered increasing trends by 42 to 2, with unknown or stable trends for 31 taxa.

  15. 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...

  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. 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

  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. Spreading of released sulphur hexafluoride into the North Atlantic through the Faroe Bank Channel

    NASA Astrophysics Data System (ADS)

    Jeansson, E.; Olsson, K. A.; Messias, M.-J.; Kristiansen, R.; Hansen, B.

    2003-04-01

    The Faroe Shetland Channel and the Faroe Bank Channel constitute the deepest connection between the Nordic Seas and the North Atlantic. Dense water formed within the Nordic Seas is transported through these channels into the North Atlantic as Iceland Scotland Overflow Water. A release of the tracer sulphur hexafluoride (SF_6) into the central Greenland Sea in summer 1996 has made it possible to follow intermediate water from the Greenland Sea around the Nordic Seas and into connecting areas. Monitoring for SF_6 has now taken place for four years in the surroundings of the Faroe Islands. The released tracer was for the first time observed north of the Faroes in early 1999, indicating a transport time from the Greenland Sea of around 2.5 years. This study investigate the incorporation of the tracer into the overflow based on observations of SF_6 just north of the Faroes, in the Faroe Bank Channel and at positions just downstream of the ridge, in the North Atlantic.

  20. Invasion of the Red Seaweed Heterosiphonia japonica Spans Biogeographic Provinces in the Western North Atlantic Ocean

    PubMed Central

    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. PMID:23638018