Science.gov

Sample records for north atlantic marine

  1. 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...

  2. 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.

  3. Prevalence of marine debris in marine birds from the North Atlantic.

    PubMed

    Provencher, Jennifer F; Bond, Alexander L; Hedd, April; Montevecchi, William A; Muzaffar, Sabir Bin; Courchesne, Sarah J; Gilchrist, H Grant; Jamieson, Sarah E; Merkel, Flemming R; Falk, Knud; Durinck, Jan; Mallory, Mark L

    2014-07-15

    Marine birds have been found to ingest plastic debris in many of the world's oceans. Plastic accumulation data from necropsies findings and regurgitation studies are presented on 13 species of marine birds in the North Atlantic, from Georgia, USA to Nunavut, Canada and east to southwest Greenland and the Norwegian Sea. Of the species examined, the two surface plungers (great shearwaters Puffinus gravis; northern fulmars Fulmarus glacialis) had the highest prevalence of ingested plastic (71% and 51%, respectively). Great shearwaters also had the most pieces of plastics in their stomachs, with some individuals containing as many of 36 items. Seven species contained no evidence of plastic debris. Reporting of baseline data as done here is needed to ensure that data are available for marine birds over time and space scales in which we see changes in historical debris patterns in marine environments (i.e. decades) and among oceanographic regions.

  4. 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...

  5. 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.

  6. North Atlantic summers have warmed more than winters since 1353, and the response of marine zooplankton

    PubMed Central

    Kamenos, Nicholas A.

    2010-01-01

    Modeling and measurements show that Atlantic marine temperatures are rising; however, the low temporal resolution of models and restricted spatial resolution of measurements (i) mask regional details critical for determining the rate and extent of climate variability, and (ii) prevent robust determination of climatic impacts on marine ecosystems. To address both issues for the North East Atlantic, a fortnightly resolution marine climate record from 1353–2006 was constructed for shallow inshore waters and compared to changes in marine zooplankton abundance. For the first time summer marine temperatures are shown to have increased nearly twice as much as winter temperatures since 1353. Additional climatic instability began in 1700 characterized by ∼5–65 year climate oscillations that appear to be a recent phenomenon. Enhanced summer-specific warming reduced the abundance of the copepod Calanus finmarchicus, a key food item of cod, and led to significantly lower projected abundances by 2040 than at present. The faster increase of summer marine temperatures has implications for climate projections and affects abundance, and thus biomass, near the base of the marine food web with potentially significant feedback effects for marine food security. PMID:21148422

  7. First Annually Resolved Marine Temperature Series For The Last 1000 Years From The North Atlantic

    NASA Astrophysics Data System (ADS)

    Reynolds, D.; Scourse, J. D.; Richardson, C.; Hall, I. R.; Butler, P.; Nederbragt, A.; Wanamaker, A. D.; Becker, J.

    2013-12-01

    There remain very few high-resolution records of marine climate variability covering the last 1000 years; annually-resolved series have hitherto been confined to coral archives from the low latitude oceans and do not cover the full millennium. We have constructed a 1357-year crossdated sclerochronology based on annual growth increments in the long-lived bivalve mollusc Arctica islandica, collected by dredge from the temperate North Atlantic (Grimsey, North Icelandic shelf, 80 m water depth; Butler et al. 2013). We present here annual- to sub-annually-resolved oxygen isotope data from the last 1000 years of this absolute chronology. Radiocarbon analysis of the series demonstrates variability in the marine reservoir effect (ΔR) controlled by Atlantic vs. Arctic water masses (Irminger Current, East Icelandic Current) with enhanced ingress of Irminger Current water during the Medieval Climate Anomaly and since AD 1900; the Little Ice Age is conversely characterized by Arctic water masses (Wanamaker et al. 2012). We use the ΔR variability to correct for the isotopic content of seawater (δ18Ow) and hence convert δ18Oshell to seawater temperature at 80m, a calibration supported by comparison with instrumental series. This reveals the evolution of North Atlantic seawater temperatures over the last 1000 years in unprecedented detail and provides a basis for the comparison of marine with terrestrial series at the same resolution for the first time.

  8. Marine biogenic source of atmospheric organic nitrogen in the subtropical North Atlantic.

    PubMed

    Altieri, Katye E; Fawcett, Sarah E; Peters, Andrew J; Sigman, Daniel M; Hastings, Meredith G

    2016-01-26

    Global models estimate that the anthropogenic component of atmospheric nitrogen (N) deposition to the ocean accounts for up to a third of the ocean's external N supply and 10% of anthropogenic CO2 uptake. However, there are few observational constraints from the marine atmospheric environment to validate these findings. Due to the paucity of atmospheric organic N data, the largest uncertainties related to atmospheric N deposition are the sources and cycling of organic N, which is 20-80% of total N deposition. We studied the concentration and chemical composition of rainwater and aerosol organic N collected on the island of Bermuda in the western North Atlantic Ocean over 18 mo. Here, we show that the water-soluble organic N concentration ([WSON]) in marine aerosol is strongly correlated with surface ocean primary productivity and wind speed, suggesting a marine biogenic source for aerosol WSON. The chemical composition of high-[WSON] aerosols also indicates a primary marine source. We find that the WSON in marine rain is compositionally different from that in concurrently collected aerosols, suggesting that in-cloud scavenging (as opposed to below-cloud "washout") is the main contributor to rain WSON. We conclude that anthropogenic activity is not a significant source of organic N to the marine atmosphere over the North Atlantic, despite downwind transport from large pollution sources in North America. This, in conjunction with previous work on ammonium and nitrate, leads to the conclusion that only 27% of total N deposition to the global ocean is anthropogenic, in contrast to the 80% estimated previously. PMID:26739561

  9. Marine biogenic source of atmospheric organic nitrogen in the subtropical North Atlantic

    PubMed Central

    Altieri, Katye E.; Fawcett, Sarah E.; Peters, Andrew J.; Sigman, Daniel M.; Hastings, Meredith G.

    2016-01-01

    Global models estimate that the anthropogenic component of atmospheric nitrogen (N) deposition to the ocean accounts for up to a third of the ocean’s external N supply and 10% of anthropogenic CO2 uptake. However, there are few observational constraints from the marine atmospheric environment to validate these findings. Due to the paucity of atmospheric organic N data, the largest uncertainties related to atmospheric N deposition are the sources and cycling of organic N, which is 20–80% of total N deposition. We studied the concentration and chemical composition of rainwater and aerosol organic N collected on the island of Bermuda in the western North Atlantic Ocean over 18 mo. Here, we show that the water-soluble organic N concentration ([WSON]) in marine aerosol is strongly correlated with surface ocean primary productivity and wind speed, suggesting a marine biogenic source for aerosol WSON. The chemical composition of high-[WSON] aerosols also indicates a primary marine source. We find that the WSON in marine rain is compositionally different from that in concurrently collected aerosols, suggesting that in-cloud scavenging (as opposed to below-cloud “washout”) is the main contributor to rain WSON. We conclude that anthropogenic activity is not a significant source of organic N to the marine atmosphere over the North Atlantic, despite downwind transport from large pollution sources in North America. This, in conjunction with previous work on ammonium and nitrate, leads to the conclusion that only 27% of total N deposition to the global ocean is anthropogenic, in contrast to the 80% estimated previously. PMID:26739561

  10. North Atlantic Circulation

    NASA Astrophysics Data System (ADS)

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

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

  11. A quantitative micropaleontologic method for shallow marine peleoclimatology: Application to Pliocene deposits of the western North Atlantic Ocean

    USGS Publications Warehouse

    Cronin, T. M.; Dowsett, H.J.

    1990-01-01

    A transfer function was developed to estimate summer and winter paleotemperatures for arctic to tropical regions of the western North Atlantic Ocean using fossil ostracode assemblages. Q-mode factor analysis was run on ostracode assemblages from 100 modern bottom sediment samples from continental shelves of North America, Greenland and the Caribbean using 59 ostracode taxa. Seven factors accounting for 80% of the variance define assemblages that correspond to frigid, subfrigid, cold temperate, mild temperate, warm temperate, subtropical and tropical climatic zones. Multiple regression of the factor matrix against observed February and August bottom temperatures yielded an astracode transfer function with an accuracy of about ??2??C. The transfer function was used to reconstruct middle Pliocene (3.5-3.0 Ma) shallow marine climates of the western North Atlantic during the marine transgression that deposited the Yorktown Formation (Virginia and North Carolina), the Duplin Formation (South and North Carolina) and the Pinecrest beds (Florida). Middle Pliocene paleowater temperatures in Virginia averaged 19??C in August and 13.5??C in February, about 5??C to 8??C warmer than at comparable depths off Virginia today. August and February water temperatures in North Carolina were 23??C and 13.4??C, in South Carolina about 23??C and 13.5??C and in southern Florida about 24.6??C and 15.4??C. Marine climates north of 35??N were warmer than today; south of 35??N, they were about the same or slightly cooler. Thermal gradients along the coast were generally not as steep as they are today. The North Atlantic transfer function can be applied to other shallow marine Pliocene and Pleistocene deposits of eastern North America. ?? 1990 Elsevier Science Publishers B.V.

  12. The Radiative Role of Free Tropospheric Aerosols and Marine Clouds over the Central North Atlantic

    SciTech Connect

    Mazzoleni, Claudio; Kumar, Sumit; Wright, Kendra; Kramer, Louisa; Mazzoleni, Lynn; Owen, Robert; Helmig, Detlev

    2014-12-09

    The scientific scope of the project was to exploit the unique location of the Pico Mountain Observatory (PMO) located in the summit caldera of the Pico Volcano in Pico Island in the Azores, for atmospheric studies. The observatory, located at 2225m a.s.l., typically samples free tropospheric aerosols laying above the marine low-level clouds and long-range transported from North America. The broad purpose of this research was to provide the scientific community with a better understanding of fundamental physical processes governing the effects of aerosols on radiative forcing and climate; with the ultimate goal of improving our abilities to understand past climate and to predict future changes through numerical models. The project was 'exploratory' in nature, with the plan to demonstrate the feasibility of deploying for the first time, an extensive aerosol research package at PMO. One of the primary activities was to test the deployment of these instruments at the site, to collect data during the 2012 summer season, and to further develop the infrastructure and the knowledge for performing novel research at PMO in follow-up longer-term aerosol-cloud studies. In the future, PMO could provide an elevated research outpost to support the renewed DOE effort in the Azores that was intensified in 2013 with the opening of the new sea-level ARM-DOE Eastern North Atlantic permanent facility at Graciosa Island. During the project period, extensive new data sets were collected for the planned 2012 season. Thanks to other synergistic activities and opportunities, data collection was then successfully extended to 2013 and 2014. Highlights of the scientific findings during this project include: a) biomass burning contribute significantly to the aerosol loading in the North Atlantic free troposphere; however, long-range transported black carbon concentrations decreased substantially in the last decade. b) Single black carbon particles – analyzed off-line at the electron

  13. Temperature tolerance and energetics: a dynamic energy budget-based comparison of North Atlantic marine species

    PubMed Central

    Freitas, Vânia; Cardoso, Joana F. M. F.; Lika, Konstadia; Peck, Myron A.; Campos, Joana; Kooijman, Sebastiaan A. L. M.; van der Veer, Henk W.

    2010-01-01

    Temperature tolerance and sensitivity were examined for some North Atlantic marine species and linked to their energetics in terms of species-specific parameters described by dynamic energy budget (DEB) theory. There was a general lack of basic information on temperature tolerance and sensitivity for many species. Available data indicated that the ranges in tolerable temperatures were positively related to optimal growth temperatures. However, no clear relationships with temperature sensitivity were established and no clear differences between pelagic and demersal species were observed. The analysis was complicated by the fact that for pelagic species, experimental data were completely absent and even for well-studied species, information was incomplete and sometimes contradictory. Nevertheless, differences in life-history strategies were clearly reflected in parameter differences between related species. Two approaches were used in the estimation of DEB parameters: one based on the assumption that reserve hardly contributes to physical volume; the other does not make this assumption, but relies on body-size scaling relationships, using parameter values of a generalized animal as pseudo-data. Temperature tolerance and sensitivity seemed to be linked with the energetics of a species. In terms of growth, relatively high temperature optima, sensitivity and/or tolerance were related to lower relative assimilation rates as well as lower maintenance costs. Making the step from limited observations to underlying mechanisms is complicated and extrapolations should be carefully interpreted. Special attention should be devoted to the estimation of parameters using body-size scaling relationships predicted by the DEB theory. PMID:20921053

  14. Sources and sinks of acetone, methanol, and acetaldehyde in North Atlantic marine air

    NASA Astrophysics Data System (ADS)

    Lewis, A. C.; Hopkins, J. R.; Carpenter, L. J.; Stanton, J.; Read, K. A.; Pilling, M. J.

    2005-08-01

    Measurements of acetone, methanol, acetaldehyde and a range of non-methane hydrocarbons have been made in North Atlantic marine air at the Mace Head observatory. Under maritime conditions the combination of OVOCs (acetone, methanol and acetaldehyde) contributed up to 85% of the total mass of measured non methane organics in air and up to 80% of the OH radical organic sink, when compared with the sum of all other organic compounds including non-methane hydrocarbons, DMS and OH-reactive halocarbons (trichloromethane and tetrachloroethylene). The observations showed anomalies in the variance and abundance of acetaldehyde and acetone over that expected for species with a remote terrestrial emission source and OH controlled chemical lifetime. A detailed model incorporating an explicit chemical degradation mechanism indicated in situ formation during air mass transport was on timescales longer than the atmospheric lifetime of precursor hydrocarbons or primary emission. The period over which this process was significant was similar to that of airmass motion on intercontinental scales, and formation via this route may reproduce that of a widespread diffuse source. The model indicates that continued short chain OVOC formation occurs many days from the point of emission, via longer lived intermediates of oxidation such as organic peroxides and long chain alcohols.

  15. Glacial history of the North Atlantic marine snail, Littorina saxatilis, inferred from distribution of mitochondrial DNA lineages.

    PubMed

    Panova, Marina; Blakeslee, April M H; Miller, A Whitman; Mäkinen, Tuuli; Ruiz, Gregory M; Johannesson, Kerstin; André, Carl

    2011-01-01

    The North Atlantic intertidal gastropod, Littorina saxatilis (Olivi, 1792), exhibits extreme morphological variation between and within geographic regions and has become a model for studies of local adaptation; yet a comprehensive analysis of the species' phylogeography is lacking. Here, we examine phylogeographic patterns of the species' populations in the North Atlantic and one remote Mediterranean population using sequence variation in a fragment of the mitochondrial cytochrome b gene (607 bp). We found that, as opposed to many other rocky intertidal species, L. saxatilis has likely had a long and continuous history in the Northwest Atlantic, including survival during the last glacial maximum (LGM), possibly in two refugia. In the Northeast Atlantic, several areas likely harboured refugial populations that recolonized different parts of this region after glacial retreat, resulting in strong population structure. However, the outlying monomorphic Venetian population is likely a recent anthropogenic introduction from northern Europe and not a remnant of an earlier wider distribution in the Mediterranean Sea. Overall, our detailed phylogeography of L. saxatilis adds an important piece to the understanding of Pleistocene history in North Atlantic marine biota as well as being the first study to describe the species' evolutionary history in its natural range. The latter contribution is noteworthy because the snail has recently become an important model species for understanding evolutionary processes of speciation; thus our work provides integral information for such endeavours. PMID:21412417

  16. Glacial history of the North Atlantic marine snail, Littorina saxatilis, inferred from distribution of mitochondrial DNA lineages.

    PubMed

    Panova, Marina; Blakeslee, April M H; Miller, A Whitman; Mäkinen, Tuuli; Ruiz, Gregory M; Johannesson, Kerstin; André, Carl

    2011-01-01

    The North Atlantic intertidal gastropod, Littorina saxatilis (Olivi, 1792), exhibits extreme morphological variation between and within geographic regions and has become a model for studies of local adaptation; yet a comprehensive analysis of the species' phylogeography is lacking. Here, we examine phylogeographic patterns of the species' populations in the North Atlantic and one remote Mediterranean population using sequence variation in a fragment of the mitochondrial cytochrome b gene (607 bp). We found that, as opposed to many other rocky intertidal species, L. saxatilis has likely had a long and continuous history in the Northwest Atlantic, including survival during the last glacial maximum (LGM), possibly in two refugia. In the Northeast Atlantic, several areas likely harboured refugial populations that recolonized different parts of this region after glacial retreat, resulting in strong population structure. However, the outlying monomorphic Venetian population is likely a recent anthropogenic introduction from northern Europe and not a remnant of an earlier wider distribution in the Mediterranean Sea. Overall, our detailed phylogeography of L. saxatilis adds an important piece to the understanding of Pleistocene history in North Atlantic marine biota as well as being the first study to describe the species' evolutionary history in its natural range. The latter contribution is noteworthy because the snail has recently become an important model species for understanding evolutionary processes of speciation; thus our work provides integral information for such endeavours.

  17. Getting it right for the North Atlantic right whale (Eubalaenaglacialis): a last opportunity for effective marine spatial planning?

    PubMed

    Petruny, Loren M; Wright, Andrew J; Smith, Courtney E

    2014-08-15

    The North Atlantic right whale (Eubalaena glacialis) faces increasing pressure from commercial shipping traffic and proposed marine renewable energy developments. Drawing upon the successful Stellwagen Bank National Marine Sanctuary model, we propose a multi-stakeholder marine spatial planning process that considers both appropriate positioning of offshore wind farms and redefining commercial shipping lanes relative to whale migration routes: placement of wind turbines within certain right whale habitats may prove beneficial for the species. To that end, it may be advisable to initially relocate the shipping lanes for the benefit of the whales prior to selecting wind energy areas. The optimal end-state is the commercial viability of renewable energy, as well as a safe shipping infrastructure, with minimal risk of collision and exposure to shipping noise for the whales. This opportunity to manage impacts on right whales could serve as a model for other problematic interactions between marine life and commercial activities. PMID:24998798

  18. Getting it right for the North Atlantic right whale (Eubalaenaglacialis): a last opportunity for effective marine spatial planning?

    PubMed

    Petruny, Loren M; Wright, Andrew J; Smith, Courtney E

    2014-08-15

    The North Atlantic right whale (Eubalaena glacialis) faces increasing pressure from commercial shipping traffic and proposed marine renewable energy developments. Drawing upon the successful Stellwagen Bank National Marine Sanctuary model, we propose a multi-stakeholder marine spatial planning process that considers both appropriate positioning of offshore wind farms and redefining commercial shipping lanes relative to whale migration routes: placement of wind turbines within certain right whale habitats may prove beneficial for the species. To that end, it may be advisable to initially relocate the shipping lanes for the benefit of the whales prior to selecting wind energy areas. The optimal end-state is the commercial viability of renewable energy, as well as a safe shipping infrastructure, with minimal risk of collision and exposure to shipping noise for the whales. This opportunity to manage impacts on right whales could serve as a model for other problematic interactions between marine life and commercial activities.

  19. Persistent marine debris in the North Sea, Northwest Atlantic Ocean, Wider Caribbean Area, and the West Coast of Baja California. Final report

    SciTech Connect

    Heneman, B.

    1988-07-01

    Information on persistent marine debris (including plastics, glass, metal, and tar) in four study areas (North Sea, northwest Atlantic Ocean, Wider Caribbean Area, and the west coast of Baja California) was obtained through literature searches, a mailed survey, correspondence, interviews, and personal observations. All of the study areas except Baja California were found to have severe marine debris problems.

  20. 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

  1. TRACEing Last Glacial Period (25-80 ka b2k) tephra horizons within North Atlantic marine cores and exploring links to the Greenland ice-cores

    NASA Astrophysics Data System (ADS)

    Abbott, P. M.; Davies, S. M.; Griggs, A. J.; Bourne, A. J.; Cook, E.; Pearce, N. J. G.; Austin, W. E. N.; Chapman, M.; Hall, I. R.; Purcell, C. S.; Scourse, J. D.; Rasmussen, T. L.

    2015-12-01

    Tephrochronology is a powerful technique for the correlation and synchronisation of disparate palaeoclimatic records from different depositional environments and has considerable potential for testing climatic phasing. For example, the relative timing of atmospheric and marine changes caused by the abrupt climatic events that punctuated the last glacial period within the North Atlantic region. Here we report on efforts to establish a framework of tephra horizons within North Atlantic marine sequences that can correlate these records and if traced in the Greenland ice-cores can act as isochronous tie-lines. Investigations have been conducted on a network of marine cores from a number of sites across the North Atlantic. Tephra horizons have been identified using cryptotephra extraction techniques more commonly applied to the study of terrestrial sequences. There are two main challenges with assessing cryptotephras in the glacial North Atlantic; i) determining the transportation processes and ii) assessing the influence of secondary reworking processes and the stratigraphic integrity of the isochrons. These processes and their influence are investigated for each cryptotephra using shard size variations, major element heterogeneity and co-variance of IRD input for some cores. Numerous Icelandic cryptophras have been successfully identified in the marine records and we will discuss the integration of a number of these with an isochronous nature into a marine tephra framework and how potential correlations to the Greenland ice-core tephra framework are determined. Spatial patterns in the nature of tephra records that are emerging from the core network will be highlighted to outline some of the key areas that could be explored in the future. In addition, the synchronisation of multiple North Atlantic records to the Greenland ice-cores using the North Atlantic Ash Zone II to test the synchroneity of an abrupt cooling in the North Atlantic will be discussed.

  2. Are Known Cyanotoxins Involved in the Toxicity of Picoplanktonic and Filamentous North Atlantic Marine Cyanobacteria?

    PubMed Central

    Frazão, Bárbara; Martins, Rosário; Vasconcelos, Vitor

    2010-01-01

    Eight marine cyanobacteria strains of the genera Cyanobium, Leptolyngbya, Oscillatoria, Phormidium, and Synechococcus were isolated from rocky beaches along the Atlantic Portuguese central coast and tested for ecotoxicity. Strains were identified by morphological characteristics and by the amplification and sequentiation of the 16S rDNA. Bioactivity of dichloromethane, methanol and aqueous extracts was assessed by the Artemia salina bioassay. Peptide toxin production was screened by matrix assisted laser desorption/ionization time of flight mass spectrometry. Molecular analysis of the genes involved in the production of known cyanotoxins such as microcystins, nodularins and cylindrospermopsin was also performed. Strains were toxic to the brine shrimp A. salina nauplii with aqueous extracts being more toxic than the organic ones. Although mass spectrometry analysis did not reveal the production of microcystins or other known toxic peptides, a positive result for the presence of mcyE gene was found in one Leptolyngbya strain and one Oscillatoria strain. The extensive brine shrimp mortality points to the involvement of other unknown toxins, and the presence of a fragment of genes involved in the cyanotoxin production highlight the potential risk of cyanobacteria occurrence on the Atlantic coast. PMID:20631874

  3. Year-round measurements of nitrogen oxides and ozone in the tropical North Atlantic marine boundary layer

    NASA Astrophysics Data System (ADS)

    Lee, J. D.; Moller, S. J.; Read, K. A.; Lewis, A. C.; Mendes, L.; Carpenter, L. J.

    2009-11-01

    A highly sensitive chemiluminescence instrument has been deployed to measure nitric oxide (NO) and nitrogen dioxide (NO2) at the Cape Verde Atmospheric Observatory in the remote tropical North Atlantic marine boundary layer (MBL). Using two different methods, the instrument was assessed to have a detection limit of around 1.8 parts per trillion by volume (pptv) for NO and 5.5 pptv for NO2 for hour-long integration periods. The overall accuracy was estimated at ˜18% for NO and 30% for NO2. Measurements of NO, NO2, and ozone (O3) over a period of 12 months in 2007 show very low levels of NOx (typically <30 pptv) and net daytime ozone destruction on most days of the measurement period. Air originating over Africa exhibited the highest levels of NOx (˜35 pptv) and reduced daily O3 destruction, with O3 production observed on a few days. Air that had not originated over Africa showed lower NOx levels (˜25 pptv), with greater observed O3 destruction. A dependence of the observed O3 destruction on NO mixing ratios, averaged over all air masses, was observed and reproduced using a simple box model. The model results imply that the presence of between 17 and 34 pptv of NO (depending on the month) would be required to turn the tropical North Atlantic from an O3 destroying to an O3 producing regime.

  4. Transport and outflow to the North Atlantic in the lower marine troposphere during ICARTT 2004

    NASA Astrophysics Data System (ADS)

    Davis, S. R.; Talbot, R.; Mao, H.

    2012-01-01

    An analysis of pollution plumes emitted from sources in the Northeastern US was based on observations from the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) 2004 field campaign. Particular attention was given to the relation of these plumes to coastal transport patterns in lower tropospheric layers throughout the Gulf of Maine (GOM) and their contribution to large-scale pollution outflow from the North American continent. Using measurements obtained during a series of flights of the NOAA WP-3D and the NASA DC-8, a unique quasi-lagrangian case study was conducted for a freshly emitted plume emanating from the New York City source region in late July 2004. The initial development of this plume stemmed from the accumulation of boundary layer pollutants within a coastal residual layer where weak synoptic forcing triggered its advection by mean southwesterly flow. As the plume tracked into the GOM, analysis showed that the plume layer vertical structure evolved into an internal boundary layer form, with signatures of steep vertical gradients in temperature, moisture and wind speed often resulting in periodic turbulence. This structure remained well-defined during the plume study, allowing for the detachment of the plume layer from the surface and thus minimal deposition and plume-sea surface exchange. In contrast, lateral mixing with other low-level plumes was significant during its transit and facilitated in part by persistent shear driven turbulence which further contributed to the high spatial variability in trace gas mixing ratios. The impact of the plume inland was assessed using observations from the AIRMAP air quality network. This impact was noticeably detected as a contribution to poor surface ozone conditions and significant elevations of other major pollutants to levels equaling the highest observed that summer. Further contributions to larger-scale outflow across the North Atlantic was also observed and analyzed.

  5. Tropical North Atlantic subsurface warming events as a fingerprint for AMOC variability during Marine Isotope Stage 3

    NASA Astrophysics Data System (ADS)

    Parker, Andrew O.; Schmidt, Matthew W.; Chang, Ping

    2015-11-01

    The role of Atlantic Meridional Overturning Circulation (AMOC) as the driver of Dansgaard-Oeschger (DO) variability that characterized Marine Isotope Stage 3 (MIS 3) has long been hypothesized. Although there is ample proxy evidence suggesting that DO events were robust features of glacial climate, there is little data supporting a link with AMOC. Recently, modeling studies and subsurface temperature reconstructions have suggested that subsurface warming across the tropical North Atlantic can be used to fingerprint a weakened AMOC during the deglacial because a reduction in the strength of the western boundary current allows warm salinity maximum water of the subtropical gyre to enter the deep tropics. To determine if AMOC variability played a role during the DO cycles of MIS 3, we present new, high-resolution Mg/Ca and δ18O records spanning 24-52 kyr from the near-surface dwelling planktonic foraminifera Globigerinoides ruber and the lower thermocline dwelling planktonic foraminifera Globorotalia truncatulinoides in Southern Caribbean core VM12-107 (11.33°N, 66.63°W, 1079 m depth). Our subsurface Mg/Ca record reveals abrupt increases in Mg/Ca ratios (the largest equal to a 4°C warming) during the interstadial-stadial transition of most DO events during this period. This change is consistent with reconstructions of subsurface warming events associated with cold events across the deglacial using the same core. Additionally, our data support the conclusion reached by a recently published study from the Florida Straits that AMOC did not undergo significant reductions during Heinrich events 2 and 3. This record presents some of the first high-resolution marine sediment derived evidence for variable AMOC during MIS 3.

  6. Challenges in integrative approaches to modelling the marine ecosystems of the North Atlantic: Physics to fish and coasts to ocean

    NASA Astrophysics Data System (ADS)

    Holt, Jason; Icarus Allen, J.; Anderson, Thomas R.; Brewin, Robert; Butenschön, Momme; Harle, James; Huse, Geir; Lehodey, Patrick; Lindemann, Christian; Memery, Laurent; Salihoglu, Baris; Senina, Inna; Yool, Andrew

    2014-12-01

    It has long been recognised that there are strong interactions and feedbacks between climate, upper ocean biogeochemistry and marine food webs, and also that food web structure and phytoplankton community distribution are important determinants of variability in carbon production and export from the euphotic zone. Numerical models provide a vital tool to explore these interactions, given their capability to investigate multiple connected components of the system and the sensitivity to multiple drivers, including potential future conditions. A major driver for ecosystem model development is the demand for quantitative tools to support ecosystem-based management initiatives. The purpose of this paper is to review approaches to the modelling of marine ecosystems with a focus on the North Atlantic Ocean and its adjacent shelf seas, and to highlight the challenges they face and suggest ways forward. We consider the state of the art in simulating oceans and shelf sea physics, planktonic and higher trophic level ecosystems, and look towards building an integrative approach with these existing tools. We note how the different approaches have evolved historically and that many of the previous obstacles to harmonisation may no longer be present. We illustrate this with examples from the on-going and planned modelling effort in the Integrative Modelling Work Package of the EURO-BASIN programme.

  7. 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

  8. Remote sensing in the coastal and marine environment. Proceedings of the US North Atlantic Regional Workshop

    NASA Technical Reports Server (NTRS)

    Zaitzeff, J. B. (Editor); Cornillon, P. (Editor); Aubrey, D. A. (Editor)

    1980-01-01

    Presentations were grouped in the following categories: (1) a technical orientation of Earth resources remote sensing including data sources and processing; (2) a review of the present status of remote sensing technology applicable to the coastal and marine environment; (3) a description of data and information needs of selected coastal and marine activities; and (4) an outline of plans for marine monitoring systems for the east coast and a concept for an east coast remote sensing facility. Also discussed were user needs and remote sensing potentials in the areas of coastal processes and management, commercial and recreational fisheries, and marine physical processes.

  9. Properties of cloud condensation nuclei (CCN) in the trade wind marine boundary layer of the western North Atlantic

    NASA Astrophysics Data System (ADS)

    Kristensen, Thomas B.; Müller, Thomas; Kandler, Konrad; Benker, Nathalie; Hartmann, Markus; Prospero, Joseph M.; Wiedensohler, Alfred; Stratmann, Frank

    2016-03-01

    Cloud optical properties in the trade winds over the eastern Caribbean Sea have been shown to be sensitive to cloud condensation nuclei (CCN) concentrations. The objective of the current study was to investigate the CCN properties in the marine boundary layer (MBL) in the tropical western North Atlantic, in order to assess the respective roles of inorganic sulfate, organic species, long-range transported mineral dust and sea-salt particles. Measurements were carried out in June-July 2013, on the east coast of Barbados, and included CCN number concentrations, particle number size distributions and offline analysis of sampled particulate matter (PM) and sampled accumulation mode particles for an investigation of composition and mixing state with transmission electron microscopy (TEM) in combination with energy-dispersive X-ray spectroscopy (EDX). During most of the campaign, significant mass concentrations of long-range transported mineral dust was present in the PM, and influence from local island sources can be ruled out. The CCN and particle number concentrations were similar to what can be expected in pristine marine environments. The hygroscopicity parameter κ was inferred, and values in the range 0.2-0.5 were found during most of the campaign, with similar values for the Aitken and the accumulation mode. The accumulation mode particles studied with TEM were dominated by non-refractory material, and concentrations of mineral dust, sea salt and soot were too small to influence the CCN properties. It is highly likely that the CCN were dominated by a mixture of sulfate species and organic compounds.

  10. Contrasted ocean conditions in the northwest North Atlantic during marine isotope stages (MIS) 11, 5e and 1

    NASA Astrophysics Data System (ADS)

    de Vernal, Anne; Fréchette, Bianca; Hillaire-Marcel, Claude

    2014-05-01

    Cores raised during the IODP Expedition 303 in the north Atlantic were analysed to document paleoceanographical conditions during recent interglacials (cf. Hillaire-Marcel et al., Marine Geol. 2011). Two key sites illustrate conditions in the inner vs outer Labrador Sea, respectively at the southwest Greenland margin (Eirik Ridge Site 1305; 57° N-48° W) and the southern Labrador rise (Orphan Knoll Site 1302/1303; 50° N-45° W). Special attention was paid to marine isotope stages (MIS) 11 (ca. 424-324 ka), 5e (ca. 128-117 ka) and the Holocene (last 11,000 years). The microfossil content of sediments (dinocyst notably) and the isotopic composition of foraminifers indicate significant differences in the conditions that prevailed during these 3 interglacial stages. Optimal conditions with regard to sea-surface temperatures (SSTs) prevailed during MIS 5e (anomalies of about + 5° C) at both sites. However, occurrence of ice rafted debris (IRD) and variations in salinity suggest meltwater discharge along the Greenland and Labrador margins during the last interglacial. On the contrary, during MIS 11, SSTs were similar to modern off Greenland or slightly lower at Orphan Knoll, but salinity was higher at both sites and IRD close to nil, whereas both sites are presently under iceberg routes. Stable oxygen isotope values in the mesopelagic Neogloboquadrina pachyderma left coiled (Npl), are generally not unlike values observed during MIS 9 or 7, i.e., slightly higher than those which characterized MIS 5e and the present interglacial, particularly in the outer Labrador Sea. This points to either a higher salinity and or a lower temperature in the subsurface water layer occupied by Npl. Low IRD, high salinity together with relatively high 18O values in foraminifers suggest limited influence of meltwater from ice cap and sea ice during MIS 11, especially the first part of the interglacial.

  11. TRACEing Last Glacial Period (25-80 ka b2k) Tephra Horizons between North Atlantic marine-cores and the Greenland ice-cores

    NASA Astrophysics Data System (ADS)

    Abbott, Peter; Davies, Siwan; Griggs, Adam; Bourne, Anna; Cook, Eliza; Austin, William; Chapman, Mark; Hall, Ian; Purcell, Catriona; Rasmussen, Tine; Scourse, James

    2014-05-01

    Tephrochronological investigations are currently being undertaken on a network of marine cores from a range of locations and depositional settings within the North Atlantic. This work forms a component of the ERC-funded project Tephra constraints on Rapid Climate Events (TRACE). The main aim of this project is to utilise isochronous tephra horizons as direct tie-lines to correlate North Atlantic marine sequences and the Greenland ice-cores to determine the relative timing of oceanic and atmospheric changes associated with the rapid climate events that dominated the last glacial period. Early comparisons of six North Atlantic marine records (MD99-2251, MD04-2820CQ, MD04-2829CQ, MD04-2822, MD01-2461 and JM11-19PC) and the Greenland ice-cores highlight six tephra horizons common to the ice record and one or more marine sequences. These horizons are within GS-3 (26,740 ± 390 a b2k and 29,130 ± 456 a b2k), GS-9 (38,300 ± 703 a b2k), GS-10 (40,220 ± 792 a b2k) and GS-12 (43,680 ± 877 a b2k) and the widespread North Atlantic Ash Zone II (55,380 ± 1184 a b2k). New high-resolution proxy information from MD04-2820CQ allows us to explore the relative timing of climatic changes between the Goban Spur, North Atlantic and Greenland over GI-12 to GI-8 using two tephra correlations that link the records. Tephra horizons have been identified in the marine records through the successful use of cryptotephra extraction techniques more commonly applied to the study of terrestrial sequences. All horizons have an Icelandic source with horizons of both rhyolitic and basaltic composition isolated. The acquisition of high-resolution profiles of shard concentration and comprehensive geochemical characterisations for horizons is vital to this work. This allows us to disentangle the processes that transported material to core sites, which can include primary airfall, sea-ice rafting and iceberg rafting, and the potential impact of secondary reworking processes such as bottom current

  12. Tephra constraints on Rapid Climate Events (TRACE): precise correlation of marine and ice-core records during the last glacial period in the North Atlantic region

    NASA Astrophysics Data System (ADS)

    Davies, S. M.; Griggs, A. J.; Abbott, P. M.; Bourne, A. J.; Purcell, C. S.; Hall, I. R.; Scourse, J. D.

    2014-12-01

    Little has challenged our understanding of climate change more so than the abruptness with which large-scale shifts in temperature occurred during the last glacial period. Atmospheric temperature jumps occurring within decades over Greenland were closely matched by rapid changes in North Atlantic sea surface temperatures and major re-organisation of the deep ocean circulation. Although these climatic instabilities are well-documented in various proxy records, the causal mechanisms of such short-lived oscillations remain poorly understood, largely due to the dating uncertainties that prevent the integration of different archives. Synchronisation of palaeoclimate records on a common timescale is inherently problematic, and unravelling the lead/lag responses (hence cause and effect) between the Earth's climate components is currently beyond our reach. TRACE - a 5 year project funded by the European Research Council - exploits the use of microscopic traces of tephra deposits to precisely correlate the Greenland ice-cores with North Atlantic marine records. Here we draw upon examples of how these time-lines can be used to constrain the lead/lag responses between the atmospheric and oceanic systems during the last glacial period. High-resolution proxy data from North Atlantic marine cores MD04-2829CQ from the Rosemary Bank and MD04 2820CQ from the Goban Spur are integrated with the Greenland ice-cores according to the position of common tephra isochrons. These direct tie-lines allow us to focus in detail on the relative timing of rapid warming transitions between Greenland and the North Atlantic ocean during the last glacial period.

  13. Polybrominated diphenyl ethers (PBDEs) in marine mammals from Arctic and North Atlantic regions, 1986-2009.

    PubMed

    Rotander, Anna; van Bavel, Bert; Polder, Anuschka; Rigét, Frank; Auðunsson, Guðjón Atli; Gabrielsen, Geir Wing; Víkingsson, Gísli; Bloch, Dorete; Dam, Maria

    2012-04-01

    A selection of PBDE congeners was analyzed in pooled blubber samples of pilot whale (Globicephala melas), ringed seal (Phoca hispida), minke whale (Balaenoptera acutorostrata), fin whale (Balaenoptera physalus), harbor porpoise (Phocoena phocoena), hooded seal (Cystophora cristata) and Atlantic white-sided dolphin (Lagenorhynchus acutus), covering a time period of more than 20 years (1986-2009). The analytes were extracted and cleaned-up using open column extraction and multi-layer silica gel column chromatography, and the analysis was performed on a GC-MS system operating in the NCI mode. The highest PBDE levels were found in the toothed whale species pilot whale and white-sided dolphin, and the lowest levels in fin whales and ringed seals. One-sided analyses of variance (ANOVA) followed by Tukey comparisons of means were applied to test for differences between years and sampling areas. Due to inter-year sampling variability, only general comparisons of PBDE concentrations between different sampling areas could be made. Differences in PBDE concentrations between three sampling periods, from 1986 to 2007, were evaluated in samples of pilot whales, ringed seals, white-sided dolphins and hooded seals. The highest PBDE levels were found in samples from the late 1990s or beginning of 2000, possibly reflecting the increase in the global production of technical PBDE mixtures in the 1990s. The levels of BDE #153 and #154 increased relative to the total PBDE concentration in some of the species in recent years, which may indicate an increased relative exposure to higher brominated congeners. In order to assess the effect of measures taken in legally binding international agreements, it is important to continuously monitor POPs such as PBDEs in sub-Arctic and Arctic environments. PMID:21802148

  14. Influence of small-scale North Atlantic sea surface temperature patterns on the marine boundary layer and free troposphere: a study using the atmospheric ARPEGE model

    NASA Astrophysics Data System (ADS)

    Piazza, Marie; Terray, Laurent; Boé, Julien; Maisonnave, Eric; Sanchez-Gomez, Emilia

    2016-03-01

    A high-resolution global atmospheric model is used to investigate the influence of the representation of small-scale North Atlantic sea surface temperature (SST) patterns on the atmosphere during boreal winter. Two ensembles of forced simulations are performed and compared. In the first ensemble (HRES), the full spatial resolution of the SST is maintained while small-scale features are smoothed out in the Gulf Stream region for the second ensemble (SMTH). The model shows a reasonable climatology in term of large-scale circulation and air-sea interaction coefficient when compared to reanalyses and satellite observations, respectively. The impact of small-scale SST patterns as depicted by differences between HRES and SMTH shows a strong meso-scale local mean response in terms of surface heat fluxes, convective precipitation, and to a lesser extent cloudiness. The main mechanism behind these statistical differences is that of a simple hydrostatic pressure adjustment related to increased SST and marine atmospheric boundary layer temperature gradient along the North Atlantic SST front. The model response to small-scale SST patterns also includes remote large-scale effects: upper tropospheric winds show a decrease downstream of the eddy-driven jet maxima over the central North Atlantic, while the subtropical jet exhibits a significant northward shift in particular over the eastern Mediterranean region. Significant changes are simulated in regard to the North Atlantic storm track, such as a southward shift of the storm density off the coast of North America towards the maximum SST gradient. A storm density decrease is also depicted over Greenland and the Nordic seas while a significant increase is seen over the northern part of the Mediterranean basin. Changes in Rossby wave breaking frequencies and weather regimes spatial patterns are shown to be associated to the jets and storm track changes.

  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. 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.

  18. The distribution of atmospheric black carbon in the marine boundary layer over the North Atlantic and the Russian Arctic Seas in July - October 2015

    NASA Astrophysics Data System (ADS)

    Shevchenko, Vladimir P.; Kopeikin, Vladimir M.; Evangeliou, Nikolaos; Novigatsky, Alexander N.; Pankratova, Natalia V.; Starodymova, Dina P.; Stohl, Andreas; Thompson, Rona

    2016-04-01

    Black carbon (BC) particles are highly efficient at absorbing visible light, which has a large potential impact on Arctic climate. However, measurement data on the distribution of BC in the atmosphere over the North Atlantic and the Russian Arctic Seas are scarce. We present measurement data on the distribution of atmospheric BC in the marine boundary layer of the North Atlantic and Baltic, North, Norwegian, Barents, White, Kara and Laptev Seas from research cruises during July 23 to October 6, 2015. During the 62nd and 63rd cruises of the RV "Akademik Mstislav Keldysh" air was filtered through Hahnemuhle fineart quarz-microfibre filters. The mass of BC on the filter was determined by measurement of the attenuation of a beam of light transmitted through the filter. Source areas were estimated by backwards trajectories of air masses calculated using NOAA's HYSPLIT model (http://www.arl.noaa.gov/ready.html) and FLEXPART model (http://www.flexpart.eu). During some parts of the cruises, air masses arrived from background areas of high latitudes, and the measured BC concentrations were low. During other parts of the cruise, air masses arrived from industrially developed areas with strong BC sources, and this led to substantially enhanced measured BC concentrations. Model-supported analyses are currently performed to use the measurement data for constraining the emission strength in these areas.

  19. The Marine Isotope Stage 19 in the mid-latitude North Atlantic Ocean: astronomical signature and intra-interglacial variability

    NASA Astrophysics Data System (ADS)

    Ferretti, Patrizia; Crowhurst, Simon J.; Naafs, B. David A.; Barbante, Carlo

    2015-01-01

    Since the seminal work by Hays et al. (1976), a plethora of studies has demonstrated a correlation between orbital variations and climatic change. However, information on how changes in orbital boundary conditions affected the frequency and amplitude of millennial-scale climate variability is still fragmentary. The Marine Isotope Stage (MIS) 19, an interglacial centred at around 785 ka, provides an opportunity to pursue this question and test the hypothesis that the long-term processes set up the boundary conditions within which the short-term processes operate. Similarly to the current interglacial, MIS 19 is characterised by a minimum of the 400-kyr eccentricity cycle, subdued amplitude of precessional changes, and small amplitude variations in insolation. Here we examine the record of climatic conditions during MIS 19 using high-resolution stable isotope records from benthic and planktonic foraminifera from a sedimentary sequence in the North Atlantic (Integrated Ocean Drilling Program Expedition 306, Site U1313) in order to assess the stability and duration of this interglacial, and evaluate the climate system's response in the millennial band to known orbitally induced insolation changes. Benthic and planktonic foraminiferal δ18O values indicate relatively stable conditions during the peak warmth of MIS 19, but sea-surface and deep-water reconstructions start diverging during the transition towards the glacial MIS 18, when large, cold excursions disrupt the surface waters whereas low amplitude millennial scale fluctuations persist in the deep waters as recorded by the oxygen isotope signal. The glacial inception occurred at ˜779 ka, in agreement with an increased abundance of tetra-unsaturated alkenones, reflecting the influence of icebergs and associated meltwater pulses and high-latitude waters at the study site. After having combined the new results with previous data from the same site, and using a variety of time series analysis techniques, we evaluate

  20. Investigating population genetic structure in a highly mobile marine organism: the minke whale Balaenoptera acutorostrata acutorostrata in the North East Atlantic.

    PubMed

    Quintela, María; Skaug, Hans J; Øien, Nils; Haug, Tore; Seliussen, Bjørghild B; Solvang, Hiroko K; Pampoulie, Christophe; Kanda, Naohisa; Pastene, Luis A; Glover, Kevin A

    2014-01-01

    Inferring the number of genetically distinct populations and their levels of connectivity is of key importance for the sustainable management and conservation of wildlife. This represents an extra challenge in the marine environment where there are few physical barriers to gene-flow, and populations may overlap in time and space. Several studies have investigated the population genetic structure within the North Atlantic minke whale with contrasting results. In order to address this issue, we analyzed ten microsatellite loci and 331 bp of the mitochondrial D-loop on 2990 whales sampled in the North East Atlantic in the period 2004 and 2007-2011. The primary findings were: (1) No spatial or temporal genetic differentiations were observed for either class of genetic marker. (2) mtDNA identified three distinct mitochondrial lineages without any underlying geographical pattern. (3) Nuclear markers showed evidence of a single panmictic population in the NE Atlantic according STRUCTURE's highest average likelihood found at K = 1. (4) When K = 2 was accepted, based on the Evanno's test, whales were divided into two more or less equally sized groups that showed significant genetic differentiation between them but without any sign of underlying geographic pattern. However, mtDNA for these individuals did not corroborate the differentiation. (5) In order to further evaluate the potential for cryptic structuring, a set of 100 in silico generated panmictic populations was examined using the same procedures as above showing genetic differentiation between two artificially divided groups, similar to the aforementioned observations. This demonstrates that clustering methods may spuriously reveal cryptic genetic structure. Based upon these data, we find no evidence to support the existence of spatial or cryptic population genetic structure of minke whales within the NE Atlantic. However, in order to conclusively evaluate population structure within this highly mobile

  1. Investigating Population Genetic Structure in a Highly Mobile Marine Organism: The Minke Whale Balaenoptera acutorostrata acutorostrata in the North East Atlantic

    PubMed Central

    Quintela, María; Skaug, Hans J.; Øien, Nils; Haug, Tore; Seliussen, Bjørghild B.; Solvang, Hiroko K.; Pampoulie, Christophe; Kanda, Naohisa; Pastene, Luis A.; Glover, Kevin A.

    2014-01-01

    Inferring the number of genetically distinct populations and their levels of connectivity is of key importance for the sustainable management and conservation of wildlife. This represents an extra challenge in the marine environment where there are few physical barriers to gene-flow, and populations may overlap in time and space. Several studies have investigated the population genetic structure within the North Atlantic minke whale with contrasting results. In order to address this issue, we analyzed ten microsatellite loci and 331 bp of the mitochondrial D-loop on 2990 whales sampled in the North East Atlantic in the period 2004 and 2007–2011. The primary findings were: (1) No spatial or temporal genetic differentiations were observed for either class of genetic marker. (2) mtDNA identified three distinct mitochondrial lineages without any underlying geographical pattern. (3) Nuclear markers showed evidence of a single panmictic population in the NE Atlantic according STRUCTURE's highest average likelihood found at K = 1. (4) When K = 2 was accepted, based on the Evanno's test, whales were divided into two more or less equally sized groups that showed significant genetic differentiation between them but without any sign of underlying geographic pattern. However, mtDNA for these individuals did not corroborate the differentiation. (5) In order to further evaluate the potential for cryptic structuring, a set of 100 in silico generated panmictic populations was examined using the same procedures as above showing genetic differentiation between two artificially divided groups, similar to the aforementioned observations. This demonstrates that clustering methods may spuriously reveal cryptic genetic structure. Based upon these data, we find no evidence to support the existence of spatial or cryptic population genetic structure of minke whales within the NE Atlantic. However, in order to conclusively evaluate population structure within this highly mobile

  2. Endangered North Atlantic right whales (Eubalaena glacialis) experience repeated, concurrent exposure to multiple environmental neurotoxins produced by marine algae.

    PubMed

    Doucette, Gregory J; Mikulski, Christina M; King, Kristen L; Roth, Patricia B; Wang, Zhihong; Leandro, Luis F; DeGrasse, Stacey L; White, Kevin D; De Biase, Daniela; Gillett, Roxanne M; Rolland, Rosalind M

    2012-01-01

    The western North Atlantic population of right whales (Eubalaena glacialis) is one of the most critically endangered of any whale population in the world. Among the factors considered to have potentially adverse effects on the health and reproduction of E. glacialis are biotoxins produced by certain microalgae responsible for causing harmful algal blooms. The worldwide incidence of these events has continued to increase dramatically over the past several decades and is expected to remain problematic under predicted climate change scenarios. Previous investigations have demonstrated that N. Atlantic right whales are being exposed to at least two classes of algal-produced environmental neurotoxins-paralytic shellfish toxins (PSTs) and domoic acid (DA). Our primary aims during this six-year study (2001-2006) were to assess whether the whales' exposure to these algal biotoxins occurred annually over multiple years, and to what extent individual whales were exposed repeatedly and/or concurrently to one or both toxin classes. Approximately 140 right whale fecal samples obtained across multiple habitats in the western N. Atlantic were analyzed for PSTs and DA. About 40% of these samples were attributed to individual whales in the North Atlantic Right Whale Catalog, permitting analysis of biotoxin exposure according to sex, age class, and reproductive status/history. Our findings demonstrate clearly that right whales are being exposed to both of these algal biotoxins on virtually an annual basis in multiple habitats for periods of up to six months (April through September), with similar exposure rates for females and males (PSTs: ∼70-80%; DA: ∼25-30%). Notably, only one of 14 lactating females sampled did not contain either PSTs or DA, suggesting the potential for maternal toxin transfer and possible effects on neonatal animals. Moreover, 22% of the fecal samples tested for PSTs and DA showed concurrent exposure to both neurotoxins, leading to questions of interactive

  3. Endangered North Atlantic right whales (Eubalaena glacialis) experience repeated, concurrent exposure to multiple environmental neurotoxins produced by marine algae.

    PubMed

    Doucette, Gregory J; Mikulski, Christina M; King, Kristen L; Roth, Patricia B; Wang, Zhihong; Leandro, Luis F; DeGrasse, Stacey L; White, Kevin D; De Biase, Daniela; Gillett, Roxanne M; Rolland, Rosalind M

    2012-01-01

    The western North Atlantic population of right whales (Eubalaena glacialis) is one of the most critically endangered of any whale population in the world. Among the factors considered to have potentially adverse effects on the health and reproduction of E. glacialis are biotoxins produced by certain microalgae responsible for causing harmful algal blooms. The worldwide incidence of these events has continued to increase dramatically over the past several decades and is expected to remain problematic under predicted climate change scenarios. Previous investigations have demonstrated that N. Atlantic right whales are being exposed to at least two classes of algal-produced environmental neurotoxins-paralytic shellfish toxins (PSTs) and domoic acid (DA). Our primary aims during this six-year study (2001-2006) were to assess whether the whales' exposure to these algal biotoxins occurred annually over multiple years, and to what extent individual whales were exposed repeatedly and/or concurrently to one or both toxin classes. Approximately 140 right whale fecal samples obtained across multiple habitats in the western N. Atlantic were analyzed for PSTs and DA. About 40% of these samples were attributed to individual whales in the North Atlantic Right Whale Catalog, permitting analysis of biotoxin exposure according to sex, age class, and reproductive status/history. Our findings demonstrate clearly that right whales are being exposed to both of these algal biotoxins on virtually an annual basis in multiple habitats for periods of up to six months (April through September), with similar exposure rates for females and males (PSTs: ∼70-80%; DA: ∼25-30%). Notably, only one of 14 lactating females sampled did not contain either PSTs or DA, suggesting the potential for maternal toxin transfer and possible effects on neonatal animals. Moreover, 22% of the fecal samples tested for PSTs and DA showed concurrent exposure to both neurotoxins, leading to questions of interactive

  4. Increasing levels of long-chain perfluorocarboxylic acids (PFCAs) in Arctic and North Atlantic marine mammals, 1984-2009.

    PubMed

    Rotander, Anna; Kärrman, Anna; van Bavel, Bert; Polder, Anuschka; Rigét, Frank; Auðunsson, Guðjón Atli; Víkingsson, Gísli; Gabrielsen, Geir Wing; Bloch, Dorete; Dam, Maria

    2012-01-01

    Temporal variations in concentrations of perfluorinated carboxylic acids (PFCAs) and sulfonic acids (PFSAs), including perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) structural isomers, were examined in livers of pilot whale (Globicephala melas), ringed seal (Phoca hisida), minke whale (Balaenoptera acutorostrata), harbor porpoise (Phocoena phocoena), hooded seal (Cystophora cristata), Atlantic white-sided dolphin (Lagenorhynchus acutus) and in muscle tissue of fin whales (Balaenoptera physalus). The sampling spanned over 20 years (1984-2009) and covered a large geographical area of the North Atlantic and West Greenland. Liver and muscle samples were homogenized, extracted with acetonitrile, cleaned up using hexane and solid phase extraction (SPE), and analyzed by liquid chromatography with negative electrospray tandem mass spectrometry (LC-MS/MS). In general, the levels of the long-chained PFCAs (C9-C12) increased whereas the levels of PFOS remained steady over the studied period. The PFOS isomer pattern in pilot whale liver was relatively constant over the sampling years. However, in ringed seals there seemed to be a decrease in linear PFOS (L-PFOS) with time, going from 91% in 1984 to 83% in 2006. PMID:22051347

  5. 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.

  6. On the North Atlantic Circulation

    NASA Astrophysics Data System (ADS)

    Schmitz, William J.; McCartney, Michael S.

    1993-02-01

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

  7. 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

  8. 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

  9. 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

  10. 78 FR 56151 - Safety Zone, North Atlantic Ocean; Virginia Beach, VA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-12

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

  11. Solubilities of Al, Pb, Cu, and Zn in rain sampled in the marine environment over the North Atlantic Ocean and Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Lim, B.; Jickells, T. D.; Colin, J. L.; Losno, R.

    1994-09-01

    Chemical processes controlling the dissolved and particulate phase distribution of crustal (Al) and noncrustal metals (Pb, Cu, and Zn) appear to differ in marine precipitation sampled over the North Atlantic Ocean and Mediterranean Sea. Dissolved Al appears to be in equilibrium with a trivalent Al salt at rainwater pH < 5.1, whereas dissolved Pb, Cu, and Zn concentrations are probably controlled by adsorption/desorption processes in which rainwater particulates provide surface-active sorption sites. In both processes, rainwater pH is a critical parameter. Results suggest that in marine precipitation with pH < 5, > 80% of the total Pb, Cu, and Zn concentrations are delivered to the surface oceans in the dissolved form. For a corresponding pH range, Al solubility varies from <5% to >60%. Over the wider observed pH range (of 3.5 to 6.9), the solubilities of Pb, Cu, Zn, and Al are highly variable. The use of mean trace metal solubilities for the assessment of dissolved atmospheric trace metal wet deposition fluxes, and their effects on surface ocean biogeochemistry should be constrained by taking into account rainwater pH in future estimates in global models.

  12. Millennial-scale versus long-term dynamics in the surface and subsurface of the western North Atlantic Subtropical Gyre during Marine Isotope Stage 5

    NASA Astrophysics Data System (ADS)

    Bahr, André; Nürnberg, Dirk; Karas, Cyrus; Grützner, Jens

    2013-12-01

    Subtropical Gyres are an important constituent of the ocean-atmosphere system due to their capacity to store vast amounts of warm and saline waters. Here we decipher the sensitivity of the (sub)surface North Atlantic Subtropical Gyre with respect to orbital and millennial scale climate variability between ~ 140 and 70 ka, Marine Isotope Stage (MIS) 5. Using (isotope) geochemical proxy data from surface and thermocline dwelling foraminifers from Blake Ridge off the west coast of North America (ODP Site 1058) we show that the oceanographic development at subsurface (thermocline) level is substantially different from the surface ocean. Most notably, surface temperatures and salinities peak during the penultimate deglaciation (Termination II) and early MIS 5e, implying that subtropical surface ocean heat and salt accumulation might have resulted from a sluggish northward heat transport. In contrast, maximum thermocline temperatures are reached during late MIS 5e when surface temperatures are already declining. We argue that the subsurface warming originated from intensified Ekman downwelling in the Subtropical Gyre due to enhanced wind stress. During MIS 5a-d a tight interplay of the subtropical upper ocean hydrography to high latitude millennial-scale cold events can be observed. At Blake Ridge, the most pronounced of these high latitude cold events are related to surface warming and salt accumulation in the (sub)surface. Similar to Termination II, heat accumulated in the Subtropical Gyre probably due to a reduced Atlantic Meridional Overturning Circulation. Additionally, a southward shift and intensification of the subtropical wind belts lead to a decrease of on-site precipitation and enhanced evaporation, coupled to intensified gyre circulation. Subsequently, the northward advection of this warm and saline water likely contributed to the fast resumption of the overturning circulation at the end of these high latitude cold events.

  13. Idiomarina atlantica sp. nov., a marine bacterium isolated from the deep sea sediment of the North Atlantic Ocean.

    PubMed

    Du, Juan; Lai, Qiliang; Liu, Yang; Du, Yaping; Liu, Xiupian; Sun, Fengqin; Shao, Zongze

    2015-02-01

    An aerobic Gram-negative, slightly curved rod-shaped and non-motile bacterium, designated G5_TVMV8_7(T), was isolated from the deep sea sediment sample of the North Atlantic Ocean. Strain G5_TVMV8_7(T) displayed growth at 4-45 °C (optimum, 25-35 °C), at pH 6.0-11.0 (optimum, 7.0-8.0) and in 1.0-15.0 % (w/v) NaCl (optimum, 3.0-5.0 %). Phylogenetic analysis based on the 16S rRNA gene sequences indicated that strain G5_TVMV8_7(T) belongs to the genus Idiomarina, sharing the highest similarity with Idiomarina salinarum ISL-52(T) (97.4 %) and I. homiensis PO-M2(T) (97.1 %) followed by other validly described species of the genus Idiomarina (96.9-93.5 %). The G + C content of the genomic DNA was found to be 50.2 mol %. The digital DNA-DNA hybridization value between strain G5_TVMV8_7(T) and I. salinarum ISL-52(T) was 17.70 ± 2.24 %. The average nucleotide identity values between strain G5_TVMV8_7T and I. salinarum ISL-52(T) was found to be 70.03 %. The major fatty acids were C16:0 (12.7 %), iso-C15:0 (11.5 %) and Sum In Feature 8 (C18:1 ω7c/ω6c) (13.5 %). The predominant respiratory quinone was identified as Q-8, and the polar lipids as diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol including several unidentified polar lipids. Based on the genotypic and phenotypic results, a new species Idiomarina atlantica is proposed. The type strain is G5_TVMV8_7(T) (= MCCC 1A10513(T) = KCTC 42141(T)).

  14. 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.

  15. CCN in the marine environment: Results from two intensive measurement campaigns - The Eastern North Atlantic (Mace Head) and The Southern Ocean (PEGASO cruise)

    NASA Astrophysics Data System (ADS)

    Ovadnevaite, Jurgita; Fossum, Kirsten; Ceburnis, Darius; Dall'Osto, Manuel; Simo, Rafel; O'Dowd, Colin

    2016-04-01

    Marine aerosol occurring in cloud condensation nucleus (CCN) sizes suggest that it may contribute notably to the CCN population [1, 2], but further cloud droplet number concentration would strongly depend on the ambient (cloud) conditions, such as available water content, supersaturation and competition between the CCN of different composition [3]. Since the global importance of marine aerosol particles to the cloud formation was postulated several decades ago [4], it has progressed from the evaluation of the nss-sulphate and sea salt effects to an acknowledgement of the significant role of organic aerosol [5]. It was demonstrated that primary marine organics, despite its hydrophobic nature, can possess the high CCN activation efficiency, resulting in the efficient cloud formation [6]. Results from two intensive measurement campaigns in The Eastern North Atlantic (Mace Head) and The Southern Ocean (PEGASO cruise) is presented here with the main focus on ssCCN dependence on aerosol chemical composition and, especially, origin and sources of marine organic. We investigate the activation of sea spray composed of the sea salt and externally mixed with nss-sulphate as well as the sea spray highly enriched in organics, stressing the importance of the latter to the formation of the cloud droplets. We also explore the suitability of existing theories to explain the marine aerosol activation to CCN. Acknowledgments The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) project BACCHUS under grant agreement n° 603445; Spanish Ministry of Economy and Competitiveness (MINECO) as part of the PEGASO (Ref.: CTM2012-37615) and BIO-NUC (Ref.: CGL2013-49020-R); HEA-PRTLI4;EC ACTRIS. [1] Meskhidze & Nenes (2006) Science 314, 1419-1423. [2] Sorooshian et al. (2009) Global Biogeochemical Cycles 23, GB4007. [3] O'Dowd et al. (1999) Quarterly Journal of the Royal Meteorological Society 125, 1295-1313. [4] Charlson

  16. Molecular distributions and isotopic compositions of marine aerosols over the western North Atlantic: Dicarboxylic acids, ketoacids, α-dicarbonyls (glyoxal and methylglyoxal), fatty acids, sugars, and SOA tracers

    NASA Astrophysics Data System (ADS)

    Kawamura, K.; Ono, K.; Tachibana, E.; Quinn, P.; Bates, T. S.

    2013-12-01

    Marine aerosols were collected over the western North Atlantic from off the coast of Boston to Bermuda during the WACS (Western Atlantic Climate Study) cruise of R/V Ronald H. Brown in August 2012 using a high volume air sampler and pre-combusted quartz fiber filters. Aerosol filter samples (n=5) were analyzed for OC/EC, major inorganic ions, low molecular weight dicarboxylic acids and various secondary organic aerosol (SOA) tracers using carbon analyzer, ion chromatograph, GC/FID and GC/MS, respectively. Homologous series (C2-C12) of dicarboxylic acids (31-335 ng m-3) were detected with a predominance of oxalic acid. Total carbon and nitrogen and their stable isotope ratios were determined as well as stable carbon isotopic compositions of individual diacids using IRMS. Diacids were found to be the most abundant compound class followed by monoterpene-SOA tracers > isoprene-SOA tracers > sugar compounds > ketoacids > fatty alcohols > fatty acids > α-dicarbonyls > aromatic acids > n-alkanes. The concentrations of these compounds were higher in the coastal site and decreased in the open ocean. However, diacids stayed relatively high even in the remote ocean. Interestingly, contributions of oxalic acid to total aerosol carbon increased from the coast (2.3%) to the remote ocean (5.6%) during long-range atmospheric transport. Stable carbon isotopic composition of oxalic acid increased from the coast (-17.5‰) to open ocean (-12.4‰), suggesting that photochemical aging of organic aerosols occurred during the atmospheric transport over the ocean. Stable carbon isotope ratios of bulk aerosol carbon also increased from the coast near Boston to the open ocean near Bermuda.

  17. Climatic controls on water vapor deuterium excess in the marine boundary layer of the North Atlantic based on 500 days of in situ, continuous measurements

    NASA Astrophysics Data System (ADS)

    Steen-Larsen, Hans Christian; Sveinbjörnsdottir, Arny E.; Peters, Andrew; Masson-Delmotte, Valerie

    2015-04-01

    Continuous, in situ measurements of water vapor isotopic composition have been conducted in the North Atlantic, Bermuda Islands (32.26°N 64.88°W) between November 2011 and June 2013, using a cavity-ringdown-spectrometer water vapor isotope analyzer and an autonomous self-designed calibration system. Meticulous calibration allows us to reach an accuracy and precision on 10 minute average of δ18O, δD, and d-excess of respectively 0.14‰, 0.85‰, and 1.1‰, verified using two parallel instruments with independent calibration. As a result of more than 500 days with 6-hourly data the relationships between deuterium excess, relative humidity (rh), sea surface temperature (SST), wind speed and direction are assessed. From the whole dataset, 84% of d-excess variance is explained by a strong linear relationship with relative humidity. The slope of this relationship (-42.6 ± 0.4 ‰ per % (rh)) is similar to the theoretical prediction of Merlivat and Jouzel (1979) for SST between 20°C and 30°C. However, in contrast with theory, no effect of wind speed could be detected on the relationship between d-excess and relative humidity. Separating the dataset into winter, spring, summer, and autumn seasons reveals different linear relationships between d-excess and humidity. Changes in wind directions are observed to affect the relationships between d-excess and humidity. The observed seasonal variability in the relationship between d-excess and relative humidity underlines the importance of long-term monitoring to accurately separate signals of local evaporation from signals associated with moisture advection. Steen-Larsen, H. C., Sveinbjörnsdottir, A. E., Peters, A. J., Masson-Delmotte, V., Guishard, M. P., Hsiao, G., Jouzel, J., Noone, D., Warren, J. K., and White, J. W. C.: Climatic controls on water vapor deuterium excess in the marine boundary layer of the North Atlantic based on 500 days of in situ, continuous measurements, Atmos. Chem. Phys., 14, 7741-7756, doi:10

  18. Climatic Controls on Water Vapor Deuterium Excess in the Marine Boundary Layer of the North Atlantic Based on 500 Days of in Situ, Continuous Measurements

    NASA Astrophysics Data System (ADS)

    Steen-Larsen, H. C.; Sveinbjörnsdottir, A. E.; Peters, A.; Masson-Delmotte, V.

    2014-12-01

    Continuous, in situ measurements of water vapor isotopic composition have been conducted in the North Atlantic, Bermuda Islands (32.26°N 64.88°W) between November 2011 and June 2013, using a cavity-ringdown-spectrometer water vapor isotope analyzer and an autonomous self-designed calibration system. Meticulous calibration allows us to reach an accuracy and precision on 10 minute average of d18O, dD, and d-excess of respectively 0.14‰, 0.85‰, and 1.1‰, verified using two parallel instruments with independent calibration. As a result of more than 500 days with 6-hourly data the relationships between deuterium excess, relative humidity (rh), sea surface temperature (SST), wind speed and direction are assessed. From the whole dataset, 84% of d-excess variance is explained by a strong linear relationship with relative humidity. The slope of this relationship (-42.6 ± 0.4 ‰ per % (rh)) is similar to the theoretical prediction of Merlivat and Jouzel (1979) for SST between 20ºC and 30ºC. However, in contrast with theory, no effect of wind speed could be detected on the relationship between d-excess and relative humidity. Separating the dataset into winter, spring, summer, and autumn seasons reveals different linear relationships between d-excess and humidity. Changes in wind directions are observed to affect the relationships between d-excess and humidity. The observed seasonal variability in the relationship between d-excess and relative humidity underlines the importance of long-term monitoring to accurately separate signals of local evaporation from signals associated with moisture advection. Steen-Larsen, H. C., Sveinbjörnsdottir, A. E., Peters, A. J., Masson-Delmotte, V., Guishard, M. P., Hsiao, G., Jouzel, J., Noone, D., Warren, J. K., and White, J. W. C.: Climatic controls on water vapor deuterium excess in the marine boundary layer of the North Atlantic based on 500 days of in situ, continuous measurements, Atmos. Chem. Phys., 14, 7741-7756, doi:10

  19. Influence of small-scale North Atlantic surface temperature on the marine boundary layer and free atmosphere : a study using the ARPEGE model

    NASA Astrophysics Data System (ADS)

    Piazza, M.; Terray, L.; Boe, J.

    2012-12-01

    In recent years, high resolution satellite observations have renewed interest in air-sea coupling over sea surface temperature (SST) fronts, showing that sharp SST gradients can influence surface wind. Warm small-scale SST anomalies are associated with positive surface wind anomalies, and conversely. Two theoretical mechanisms have been proposed to be involved in the generation of surface wind anomalies : the effects of local surface pressure gradients and marine atmospheric boundary layer stability changes. Not only surface fields are affected but also precipitation. This suggests a strong impact of SST fronts on the free troposphere and eventually on the large-scale atmospheric circulation. In this presentation, those mechanisms are further explored over the North Atlantic thanks to the high resolution (0.25°x0.25°) global atmospheric model ARPEGE forced by observed high resolution SST (NOAA_OI dataset), from January 2003 to July 2011. In order to analyze the effects of small-scale SST in the North Atlantic, two simulations are compared : a control simulation (HRES) with a full high resolution SST, and a perturbed simulation (SMTH) with spatially smoothed SST in the Gulfstream region (Figure a). First, the capability of the model to represent the air-sea interaction has been evaluated against satellite observations (QuickScat for surface winds and AMSR-E for SST). The air-sea interaction coefficient is defined as the regression coefficient between SST anomalies and wind speed anomalies for spatially high-pass filtered fields. Results from the HRES simulation show a strong and realistic air-sea interaction coefficient, especially in winter. Then, the seasonal comparison between HRES and SMTH shows that small-scale SST structures drive anomalies of wind speed, vorticity and convergence at the surface. The surface heat budget is investigated. It shows an average increase of 30% of turbulent heat fluxes at the surface in HRES compared to SMTH. Precipitation

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

    NASA Astrophysics Data System (ADS)

    Hurrell, James W.; Deser, Clara

    2009-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Hurrell, James W.; Deser, Clara

    2010-02-01

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

  2. 77 FR 5398 - Safety Zone; Atlantic Intracoastal Waterway, Vicinity of Marine Corps Base, Camp Lejeune, NC

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-03

    ... Marine Corps Base, Camp Lejeune, NC AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The... Marine Corps Base (MCB) Camp Lejeune, North Carolina, which encompasses the navigable waters of the AICW...; Atlantic Intracoastal Waterway, Vicinity of Marine Corps Base, Camp Lejeune, NC in the Federal Register...

  3. 78 FR 34879 - Special Local Regulations for Marine Events, Atlantic City Offshore Race, Atlantic Ocean...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-11

    ... City Offshore Race, Atlantic Ocean; Atlantic City, NJ AGENCY: Coast Guard, DHS. ACTION: Temporary final... to only one recurring marine event, held on the Atlantic Ocean, offshore of Atlantic City, New Jersey... Atlantic Ocean near Atlantic City, New Jersey, during the event. DATES: This rule will be effective on...

  4. Coccolithophores as proxy of seawater changes at orbital-to-millennial scale during middle Pleistocene Marine Isotope Stages 14-9 in North Atlantic core MD01-2446

    NASA Astrophysics Data System (ADS)

    Marino, Maria; Maiorano, Patrizia; Tarantino, Francesca; Voelker, Antje; Capotondi, Lucilla; Girone, Angela; Lirer, Fabrizio; Flores, José-Abel; Naafs, B. David A.

    2014-06-01

    Quantitative coccolithophore analyses were performed in core MD01-2446, located in the midlatitude North Atlantic, to reconstruct climatically induced sea surface water conditions throughout Marine Isotope Stages (MIS) 14-9. The data are compared to new and available paleoenvironmental proxies from the same site as well as other nearby North Atlantic records that support the coccolithophore signature at glacial-interglacial to millennial climate scale. Total coccolithophore absolute abundance increases during interglacials but abruptly drops during the colder glacial phases and deglaciations. Coccolithophore warm water taxa (wwt) indicate that MIS11c and MIS9e experienced warmer and more stable conditions throughout the whole photic zone compared to MIS13. MIS11 was a long-lasting warmer and stable interglacial characterized by a climate optimum during MIS11c when a more prominent influence of the subtropical front at the site is inferred. The wwt pattern also suggests distinct interstadial and stadial events lasting about 4-10 kyr. The glacial increases of Gephyrocapsa margereli-G. muellerae 3-4 µm along with higher values of Corg, additionally supported by the total alkenone abundance at Site U1313, indicate more productive surface waters, likely reflecting the migration of the polar front into the midlatitude North Atlantic. Distinctive peaks of G. margereli-muellerae (>4 µm), C. pelagicus pelagicus, Neogloboquadrina pachyderma left coiling, and reworked nannofossils, combined with minima in total nannofossil accumulation rate, are tracers of Heinrich-type events during MIS12 and MIS10. Additional Heinrich-type events are suggested during MIS12 and MIS14 based on biotic proxies, and we discuss possible iceberg sources at these times. Our results improve the understanding of mid-Brunhes paleoclimate and the impact on phytoplankton diversity in the midlatitude North Atlantic region.

  5. 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.

  6. North Atlantic forcing of tropical Indian Ocean climate.

    PubMed

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

    2014-05-01

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

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  9. 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.

  10. Distribution of marine birds on the mid- and North-Atlantic US outer continental shelf. Technical progress report, January 1978-July 1980

    SciTech Connect

    Powers, K.D.; Pittman, G.L.; Fitch, S.J.

    1980-09-01

    The species composition, distribution, and abundance of marine birds on continental shelf waters from Cape Hatteras to the Bay of Fundy were examined using ships-of-opportunity. Northern Fulmar, Cory's Shearwater, Greater Shearwater, Sooty Shearwater, Wilson's Storm-Petrel, Gannet, Red Phalarope, Great Black-backed Gull, Herring Gull, and Black-legged Kittiwake were the most abundant and common species. These species were ecologically dominant within the bird community in numbers and biomass. Georges Bank and Gulf of Marine regions generally had greatest estimates of standing stock and biomass; whereas, in the Middle Atlantic region these estimates were consistently lowest. Species diversity throughout the study area was greatest in spring and least in fall. Oceanic fronts at the continental shelf break and at Nantucket Shoals influenced the distribution of Wilson's Storm-Petrels and Red Phalaropes. Fishing activities were particularly important to Larus gull distribution. Fishes, squids, and crustaceans were the most important groups of prey items in diets of nine bird species. An oiled bird or pollution index was developed. According to the index, frequency of oiled birds was greatest in winter and spring, and gulls made up the majority of species with oiled plumages.

  11. 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)...

  12. 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)...

  13. 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)...

  14. 22 CFR 120.31 - North Atlantic Treaty Organization.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

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

  15. 22 CFR 120.31 - North Atlantic Treaty Organization.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

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

  16. Ocean Current Boundry, North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    1992-01-01

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

  17. The North Atlantic Treaty Organization at 40.

    ERIC Educational Resources Information Center

    Baker, John A.

    1989-01-01

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

  18. Origins of the North Atlantic Treaty.

    ERIC Educational Resources Information Center

    Rotter, Andrew J.

    1983-01-01

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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Marine Boundary Layer Processes Constrained by Multi-Year Concomitant In-Situ Water Vapor and Precipitation Isotope Measurements from Land-Based and Ship-Based Monitoring Sites in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Steen-Larsen, H. C.; Benetti, M.; Sveinbjörnsdottir, A. E.; Peters, A.; Hayden, M.

    2015-12-01

    In the global hydrological cycle the marine boundary layer plays a key role. Understanding and constraining the processes governing the water vapor isotopic composition is therefore crucial in order to improve future projection of climate change. We present here concomitant in-situ water vapor and precipitation isotope measurements carried out for several years at monitoring stations across the North Atlantic. Our observations have been carried out in different climate regions, which allow us to characterize the influence of sea surface temperature, and across several years, which allow us to separate the seasonal influence. Using this extensive dataset we focus specifically on the parameterization of the kinetic effects during evaporation from the ocean surface. We address the observed apparent lack of wind speed and sea surface temperature effect on the marine boundary layer water vapor isotopic composition by comparing the formulation by Merlivat and Jouzel (1979) and the formulation by Craig and Gordon (1964) against our water vapor and precipitation isotope observations and using calculations of backwards trajectories.

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

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

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

  7. Barcoding Atlantic Canada's commonly encountered marine fishes.

    PubMed

    McCusker, M R; Denti, D; Van Guelpen, L; Kenchington, E; Bentzen, P

    2013-03-01

    Marine fishes from the northwest Atlantic Ocean were analysed to determine whether barcoding was effective at identifying species. Our data included 177 species, 136 genera, 81 families and 28 orders. Overall, 88% of nominal species formed monophyletic clusters based on >500 bp of the CO1 region, and the average bootstrap value for these species was 98%. Although clearly effective, the percentage of species that were distinguishable with barcoding based on the criterion of reciprocal monophyletic clusters was slightly lower than has been documented in other studies of marine fishes. Eelpouts, sculpins and rocklings proved to be among the most challenging groups for barcoding, although we suspect that difficult identifications based on traditional (morphology based) taxonomy played a role. Within several taxa, speciation may have occurred too recently for barcoding to be effective (e.g. within Sebastes, Thunnus and Ammodytes) or the designation of distinct species may have been erroneous (e.g. within Antimora and Macrourus). Results were consistent with previous work recognizing particularly high levels of divergence within certain taxa, some of which have been recognized as distinct species (e.g. Osmerus mordax and Osmerus dentex; and Liparis gibbus and Liparis bathyarcticus), and some of which have not (e.g. within Halargyreus johnsonii and within Mallotus villosus). The results from this study suggest that morphology-based identification and taxonomy can be challenging in marine fishes, even within a region as well characterized as Atlantic Canada. Barcoding proved to be a very useful tool for species identification that will likely find a wide range of applications, including the fisheries trade, studies of range expansion, ecological analyses and population assessments.

  8. Ocean Modeling of the North Atlantic

    NASA Technical Reports Server (NTRS)

    Seminar, A. J.

    1984-01-01

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

  9. 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

  10. 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.

  11. 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.

  12. 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

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

    PubMed

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

    2011-11-01

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

  14. 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.

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

    NASA Astrophysics Data System (ADS)

    Visbeck, M.

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

  16. The timing of the last deglaciation in North Atlantic climate records.

    PubMed

    Waelbroeck, C; Duplessy, J C; Michel, E; Labeyrie, L; Paillard, D; Duprat, J

    2001-08-16

    To determine the mechanisms governing the last deglaciation and the sequence of events that lead to deglaciation, it is important to obtain a temporal framework that applies to both continental and marine climate records. Radiocarbon dating has been widely used to derive calendar dates for marine sediments, but it rests on the assumption that the 'apparent age' of surface water (the age of surface water relative to the atmosphere) has remained constant over time. Here we present new evidence for variation in the apparent age of surface water (or reservoir age) in the North Atlantic ocean north of 40 degrees N over the past 20,000 years. In two cores we found apparent surface-water ages to be larger than those of today by 1,230 +/- 600 and 1,940 +/- 750 years at the end of the Heinrich 1 surge event (15,000 years BP) and by 820 +/- 430 to 1,010 +/- 340 years at the end of the Younger Dryas cold episode. During the warm Bølling-Allerød period, between these two periods of large reservoir ages, apparent surface-water ages were comparable to present values. Our results allow us to reconcile the chronologies from ice cores and the North Atlantic marine records over the entire deglaciation period. Moreover, the data imply that marine carbon dates from the North Atlantic north of 40 degrees N will need to be corrected for these highly variable effects.

  17. 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.

  18. 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.

  19. 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.

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

    PubMed

    Rutberg; Hemming; Goldstein

    2000-06-22

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  2. 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}).

  3. 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.

  4. Revisiting the use of δ15N in meso-scale studies of marine food webs by considering spatio-temporal variations in stable isotopic signatures - The case of an open ecosystem: The Bay of Biscay (North-East Atlantic)

    NASA Astrophysics Data System (ADS)

    Chouvelon, T.; Spitz, J.; Caurant, F.; Mèndez-Fernandez, P.; Chappuis, A.; Laugier, F.; Le Goff, E.; Bustamante, P.

    2012-08-01

    Most of the recent framework directives and environmental policies argue for the development and the use of indicators - notably trophodynamic indicators - that should be able to follow ecosystems' evolution in space and time, particularly under anthropogenic perturbations. In the last decades, the use of stable carbon and nitrogen isotopes ratios has increased exponentially, particularly in studies of marine ecosystems' trophic structure and functioning. This method is principally based on the assumption that the isotopic composition of a consumer directly reflects that of its food. Nevertheless, few studies have attempted to define the limits of this tool, before using it and drawing ecological conclusions from isotopic analysis. This study aimed to assess the importance of considering spatio-temporal variations in isotopic signatures of consumers when using δ13C and especially δ15N values in open ecosystems with complex food webs, using the Bay of Biscay (North-East Atlantic) as a case study. To this end, more than 140 species from this marine ecosystem were analysed for the isotopic signatures in their muscle tissue. They were sampled from coastal to oceanic and deep-sea areas and at different latitudes, to evaluate spatial variations of isotopic signatures. Selected species were also sampled over several years and in two seasons to account for inter-annual and seasonal variations. In the Bay of Biscay temperate ecosystem, which is subject to both coastal and oceanic influences - two main river inputs and upwelling areas - , δ13C and δ15N values significantly decreased from inshore to offshore species, and to a lesser extent from benthic to pelagic organisms. River discharges appeared to be the first factor influencing δ13C and δ15N values in consumers. From the important spatial variations detected in δ15N values in particular, we suggest that in such contrasted ecosystem, nitrogen isotopic ratios may also be revisited as an indicator of the feeding

  5. 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)

  6. 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

  7. 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.

  8. Building International Research Partnerships in the North Atlantic-Arctic Region

    NASA Astrophysics Data System (ADS)

    Benway, Heather M.; Hofmann, Eileen; St. John, Michael

    2014-09-01

    The North Atlantic-Arctic region, which is critical to the health and socioeconomic well being of North America and Europe, is susceptible to climate-driven changes in circulation, biogeochemistry, and marine ecosystems. The need for strong investment in the study of biogeochemical and ecosystem processes and interactions with physical processes over a range of time and space scales in this region was clearly stated in the 2013 Galway Declaration, an intergovernmental statement on Atlantic Ocean cooperation (http://europa.eu/rapid/press-release_IP-13-459_en.htm). Subsequently, a workshop was held to bring together researchers from the United States, Canada, and Europe with expertise across multiple disciplines to discuss an international research initiative focused on key features, processes, and ecosystem services (e.g., Atlantic Meridional Overturning Circulation, spring bloom dynamics, fisheries, etc.) and associated sensitivities to climate changes.

  9. "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.

  10. Hierarchical population structure and habitat differences in a highly mobile marine species: the Atlantic spotted dolphin.

    PubMed

    Viricel, Amélia; Rosel, Patricia E

    2014-10-01

    Recent molecular studies have shown that highly mobile species with continuous distributions can exhibit fine-scale population structure. In this context, we assessed genetic structure within a marine species with high dispersal potential, the Atlantic spotted dolphin (Stenella frontalis). Using 19 microsatellite loci and mitochondrial control region sequences, population structure was investigated in the western North Atlantic, the Gulf of Mexico and the Azores Islands. Analyses of the microsatellite data identified four distinct genetic clusters, which were supported by the control region sequences. The highest level of divergence was seen between two clusters corresponding to previously described morphotypes that inhabit oceanic and shelf waters. The combined morphological and genetic evidence suggests these two lineages are on distinct evolutionary trajectories and could be considered distinct subspecies despite their parapatry. Further analysis of the continental shelf cluster resulted in three groups: animals inhabiting shelf waters in the western North Atlantic, the eastern Gulf of Mexico and the western Gulf of Mexico. Analyses of environmental data indicate the four genetic clusters inhabit distinct habitats in terms of depth and sea surface temperature. Contemporary dispersal rate estimates suggest all of these populations should be considered as distinct management units. Conversely, no significant genetic differentiation was observed between S. frontalis from offshore waters of the western North Atlantic and the Azores, which are separated by approximately 4500 km. Overall, the hierarchical structure observed within the Atlantic spotted dolphin shows that the biogeography of the species is complex because it is not shaped solely by geographic distance. PMID:25256360

  11. Hierarchical population structure and habitat differences in a highly mobile marine species: the Atlantic spotted dolphin.

    PubMed

    Viricel, Amélia; Rosel, Patricia E

    2014-10-01

    Recent molecular studies have shown that highly mobile species with continuous distributions can exhibit fine-scale population structure. In this context, we assessed genetic structure within a marine species with high dispersal potential, the Atlantic spotted dolphin (Stenella frontalis). Using 19 microsatellite loci and mitochondrial control region sequences, population structure was investigated in the western North Atlantic, the Gulf of Mexico and the Azores Islands. Analyses of the microsatellite data identified four distinct genetic clusters, which were supported by the control region sequences. The highest level of divergence was seen between two clusters corresponding to previously described morphotypes that inhabit oceanic and shelf waters. The combined morphological and genetic evidence suggests these two lineages are on distinct evolutionary trajectories and could be considered distinct subspecies despite their parapatry. Further analysis of the continental shelf cluster resulted in three groups: animals inhabiting shelf waters in the western North Atlantic, the eastern Gulf of Mexico and the western Gulf of Mexico. Analyses of environmental data indicate the four genetic clusters inhabit distinct habitats in terms of depth and sea surface temperature. Contemporary dispersal rate estimates suggest all of these populations should be considered as distinct management units. Conversely, no significant genetic differentiation was observed between S. frontalis from offshore waters of the western North Atlantic and the Azores, which are separated by approximately 4500 km. Overall, the hierarchical structure observed within the Atlantic spotted dolphin shows that the biogeography of the species is complex because it is not shaped solely by geographic distance.

  12. High resolution variations of the main detrital supply in the north Atlantic ocean (core MD95-2014) within marine isotopic stage 3

    NASA Astrophysics Data System (ADS)

    Bout-Roumazeilles, V.; Turpin, M.; Daux, V.; Labeyrie, L.

    2003-04-01

    The core MD95-2014 (IMAGES V) is located on the southern margin of Iceland at 2397 meters depth, on the Gardar sedimentary drift. This evolution of the drift is directly linked to the main deep circulation patterns, and is under the influence of the Iceland Scotland Overflow Water (ISOW). On the Gardar drift, the main terrigenous supply originates from Iceland. The aim of this study is to retrace the main variations of the detrital supply at high resolution within marine isotopic stage 3, in relation with rapid climatic events as Heinrich events and/or Dansgaard/Oeschger oscillations.The mineralogical and geochemical composition of the fine terrigenous components from the core MD95-2014 were determined by X-ray diffraction and ICP-AES and AAS. The coarse fraction associated to Heinrich events was separated and optically determined, in order to constrain the origin of the main ice-rafted detritus. The results indicate that the fine terrigenous fraction is mainly composed of smectite and illite. The others clay minerals (chlorite, kaolinite and mixed-layers minerals) are less abundant. According to geochemical data, the smectite originate from the basic volcanic rocks of Iceland, whereas illite is characteristics of acid rocks, probably from fennoscandinavia or british islands.On the glacial/interglacial scale, the icelandic supply of smectite is enhanced during interglacial stages (MIS 1 and 5) whereas continental supply of illite characterized the glacial periods (MIS 2 and 6). Such variations of the main terrigenous supply have been previously linked with the evolution of the ISOW between glacial and interglacial periods (Bout-Roumazeilles et al., 2002).The results also indicate that the Heinrich events and the stadials are marked by an increased continental supply (illite, chlorite, kaolinite and mixed-layers) whereas the interstadials are enriched in smectite. The coarse fraction recovered within the Heinrich levels are mainly of basaltic nature, except for the

  13. Final Report of the Mid-Atlantic Marine Wildlife Surveys, Modeling, and Data

    SciTech Connect

    Saracino-Brown, Jocelyn; Smith, Courtney; Gilman, Patrick

    2013-07-01

    The Wind Program hosted a two-day workshop on July 24-25, 2012 with scientists and regulators engaged in marine ecological survey, modeling, and database efforts pertaining to the waters of the Mid-Atlantic region. The workshop was planned by Federal agency, academic, and private partners to promote collaboration between ongoing offshore ecological survey efforts, and to promote the collaborative development of complementary predictive models and compatible databases. The meeting primarily focused on efforts to establish and predict marine mammal, seabird, and sea turtle abundance, density, and distributions extending from the shoreline to the edge of the Exclusive Economic Zone between Nantucket Sound, Massachusetts and Cape Hatteras, North Carolina.

  14. Decadal predictions of the North Atlantic CO2 uptake.

    PubMed

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

    2016-01-01

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

  15. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  17. 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.

  18. 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.

  19. Latest Quaternary palaeoceanographic change in the eastern North Atlantic based upon a dinoflagellate cyst event ecostratigraphy.

    PubMed

    Harland, Rex; Polovodova Asteman, Irina; Morley, Audrey; Morris, Angela; Harris, Anthony; Howe, John A

    2016-05-01

    The analyses of dinoflagellate cyst records, from the latest Quaternary sediments recovered from DSDP Core 610A taken on the Feni Ridge in the southern Rockall Trough, and part of core MD01-2461 on the continental margin of the Porcupine Seabight in the eastern North Atlantic Ocean, has provided evidence for significant oceanographic change encompassing the Last Glacial Maximum (LGM) and part of the Holocene. This together with other published records has led to a regional evaluation of oceanographic change in the eastern North Atlantic over the past 68 ka, based upon a distinctive dinoflagellate event ecostratigraphy. These changes reflect changes in the surface waters of the North Atlantic Current (NAC), and perhaps the deeper thermohaline Atlantic Meridional Overturning Circulation (AMOC), driving fundamental regime changes within the phytoplanktonic communities. Three distinctive dinoflagellate cyst associations based upon both factor and cluster analyses have been recognised. Associations characterised by Bitectatodinium tepikiense (between 61.1 ± 6.2 to 13.4 ± 1.1 ka BP), Nematosphaeropsis labyrinthus (between 10.5 ± 0.3 and 11.45 ± 0.8 ka. BP), and the cyst of Protoceratium reticulatum (between 8.5 ± 0.9 and 5.2 ± 1.3 ka. BP) indicate major change within the eastern North Atlantic oceanography. The transitions between these changes occur over a relatively short time span (c.1.5 ka), given our sampling resolution, and have the potential to be incorporated into an event stratigraphy through the latest Quaternary as recommended by the INTIMATE (INTegrating Ice core, MArine and TErrestrial records) group. The inclusion of a dinoflagellate cyst event stratigraphy would highlight changes within the phytoplankton of the North Atlantic Ocean as a fully glacial world changed to our present interglacial. PMID:27441285

  20. Decline of the marine ecosystem caused by a reduction in the Atlantic overturning circulation.

    PubMed

    Schmittner, Andreas

    2005-03-31

    Reorganizations of the Atlantic meridional overturning circulation were associated with large and abrupt climatic changes in the North Atlantic region during the last glacial period. Projections with climate models suggest that similar reorganizations may also occur in response to anthropogenic global warming. Here I use ensemble simulations with a coupled climate-ecosystem model of intermediate complexity to investigate the possible consequences of such disturbances to the marine ecosystem. In the simulations, a disruption of the Atlantic meridional overturning circulation leads to a collapse of the North Atlantic plankton stocks to less than half of their initial biomass, owing to rapid shoaling of winter mixed layers and their associated separation from the deep ocean nutrient reservoir. Globally integrated export production declines by more than 20 per cent owing to reduced upwelling of nutrient-rich deep water and gradual depletion of upper ocean nutrient concentrations. These model results are consistent with the available high-resolution palaeorecord, and suggest that global ocean productivity is sensitive to changes in the Atlantic meridional overturning circulation. PMID:15800620

  1. 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.

  2. Holocene dynamics of North Atlantic Deep Water Masses

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  3. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    PubMed

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

    2016-01-01

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

  6. 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

  7. Marine biodiversity in the Atlantic and Pacific coasts of South America: knowledge and gaps.

    PubMed

    Miloslavich, Patricia; Klein, Eduardo; Díaz, Juan M; Hernández, Cristián E; Bigatti, Gregorio; Campos, Lucia; Artigas, Felipe; Castillo, Julio; Penchaszadeh, Pablo E; Neill, Paula E; Carranza, Alvar; Retana, María V; Díaz de Astarloa, Juan M; Lewis, Mirtha; Yorio, Pablo; Piriz, María L; Rodríguez, Diego; Yoneshigue-Valentin, Yocie; Gamboa, Luiz; Martín, Alberto

    2011-01-01

    The marine areas of South America (SA) include almost 30,000 km of coastline and encompass three different oceanic domains--the Caribbean, the Pacific, and the Atlantic--ranging in latitude from 12∘N to 55∘S. The 10 countries that border these coasts have different research capabilities and taxonomic traditions that affect taxonomic knowledge. This paper analyzes the status of knowledge of marine biodiversity in five subregions along the Atlantic and Pacific coasts of South America (SA): the Tropical East Pacific, the Humboldt Current,the Patagonian Shelf, the Brazilian Shelves, and the Tropical West Atlantic, and it provides a review of ecosystem threats and regional marine conservation strategies. South American marine biodiversity is least well known in the tropical subregions (with the exception of Costa Rica and Panama). Differences in total biodiversity were observed between the Atlantic and Pacific oceans at the same latitude. In the north of the continent, the Tropical East Pacific is richer in species than the Tropical West Atlantic, however, when standardized by coastal length, there is very little difference among them. In the south, the Humboldt Current system is much richer than the Patagonian Shelf. An analysis of endemism shows that 75% of the species are reported within only one of the SA regions, while about 22% of the species of SA are not reported elsewhere in the world. National and regional initiatives focusing on new exploration, especially to unknown areas and ecosystems, as well as collaboration among countries are fundamental to achieving the goal of completing inventories of species diversity and distribution.These inventories will allow accurate interpretation of the biogeography of its two oceanic coasts and latitudinal trends,and will also provide relevant information for science based policies. PMID:21304960

  8. A peak and decline in North Atlantic CO2 uptake

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  9. 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.

  10. Causes and projections of abrupt climate-driven ecosystem shifts in the North Atlantic.

    PubMed

    Beaugrand, Grégory; Edwards, Martin; Brander, Keith; Luczak, Christophe; Ibanez, Frederic

    2008-11-01

    Warming of the global climate is now unequivocal and its impact on Earth' functional units has become more apparent. Here, we show that marine ecosystems are not equally sensitive to climate change and reveal a critical thermal boundary where a small increase in temperature triggers abrupt ecosystem shifts seen across multiple trophic levels. This large-scale boundary is located in regions where abrupt ecosystem shifts have been reported in the North Atlantic sector and thereby allows us to link these shifts by a global common phenomenon. We show that these changes alter the biodiversity and carrying capacity of ecosystems and may, combined with fishing, precipitate the reduction of some stocks of Atlantic cod already severely impacted by exploitation. These findings offer a way to anticipate major ecosystem changes and to propose adaptive strategies for marine exploited resources such as cod in order to minimize social and economic consequences.

  11. Incursions of southern-sourced water into the deep North Atlantic during late Pliocene glacial intensification

    NASA Astrophysics Data System (ADS)

    Lang, David C.; Bailey, Ian; Wilson, Paul A.; Chalk, Thomas B.; Foster, Gavin L.; Gutjahr, Marcus

    2016-05-01

    The circulation and internal structure of the oceans exert a strong influence on Earth's climate because they control latitudinal heat transport and the segregation of carbon between the atmosphere and the abyss. Circulation change, particularly in the Atlantic Ocean, is widely suggested to have been instrumental in the intensification of Northern Hemisphere glaciation when large ice sheets first developed on North America and Eurasia during the late Pliocene, approximately 2.7 million years ago. Yet the mechanistic link and cause/effect relationship between ocean circulation and glaciation are debated. Here we present new records of North Atlantic Ocean structure using the carbon and neodymium isotopic composition of marine sediments recording deep water for both the Last Glacial to Holocene (35-5 thousand years ago) and the late Pliocene to earliest Pleistocene (3.3-2.4 million years ago). Our data show no secular change. Instead we document major southern-sourced water incursions into the deep North Atlantic during prominent glacials from 2.7 million years ago. Our results suggest that Atlantic circulation acts as a positive feedback rather than as an underlying cause of late Pliocene Northern Hemisphere glaciation. We propose that, once surface Southern Ocean stratification and/or extensive sea-ice cover was established, cold-stage expansions of southern-sourced water such as those documented here enhanced carbon dioxide storage in the deep ocean, helping to increase the amplitude of glacial cycles.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

    Hill, D. J.

    2013-12-01

    The strong warming seen in records of mid-Pliocene sea surface temperature (SST) in the North Atlantic has proved difficult to reproduce in climate model simulations. The results of the Pliocene Model Intercomparison Project (PlioMIP) Experiment 2 fail to produce a single simulation with North Atlantic sea surface temperatures (SSTs) as high as those indicated by the PRISM3 (Pliocene Research, Interpretation and Synoptic Mapping) data set. Direct comparisons between the data and models are hampered by differing techniques used in palaeoenvironmental reconstruction and physical climate simulations. However, even if current simulations are not directly comparable to the reconstructions of the North Atlantic, something must have forced these particularly high temperatures for at least parts of the mid-Pliocene warm period. The boundary condition changes defined in the PlioMIP Experiment 2 protocol are limited to CO2, ice sheets, vegetation, land area change due to sea level rise and orography. Apart from small orographic changes imposed outside of the ice sheet regions, the rest of these factors would be expected to change under future anthropogenic climate change. As such the IPCC (Intergovernmental Panel on Climate Change) has referred to the mid-Pliocene as 'an accessible example of a world that is similar in many respects to ... the late 21st century'. However, there are a number of different palaeogeographic changes documented in published literature that are not incorporated into the PRISM3 palaeoenvironmental reconstruction used as model boundary conditions, particularly in the North Atlantic region. Although some of these would be expected under future climate change, e.g. a reduction in North Atlantic icebergs, many would not. Changes in the intensity of Icelandic mantle plume upwelling have resulted in changes in the sill depth of the Greenland-Scotland ridge over at least the last 40 million years. Pleistocene glacial erosion has created new ocean areas in

  14. 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.

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

    PubMed

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

    2015-04-16

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

  16. Avian influenza ecology in North Atlantic sea ducks: Not all ducks are created equal

    USGS Publications Warehouse

    Hall, Jeffrey S.; Russell, Robin E.; Franson, J. Christian; Soos, Catherine; Dusek, Robert J.; Allen, R. Bradford; Nashold, Sean W.; Teslaa, Joshua L.; Jónsson, Jón Einar; Ballard, Jennifer R.; Harms, Naomi Jnae; Brown, Justin D.

    2015-01-01

    Wild waterfowl are primary reservoirs of avian influenza viruses (AIV). However the role of sea ducks in the ecology of avian influenza, and how that role differs from freshwater ducks, has not been examined. We obtained and analyzed sera from North Atlantic sea ducks and determined the seroprevalence in those populations. We also tested swab samples from North Atlantic sea ducks for the presence of AIV. We found relatively high serological prevalence (61%) in these sea duck populations but low virus prevalence (0.3%). Using these data we estimated that an antibody half-life of 141 weeks (3.2 years) would be required to attain these prevalences. These findings are much different than what is known in freshwater waterfowl and have implications for surveillance efforts, AIV in marine environments, and the roles of sea ducks and other long-lived waterfowl in avian influenza ecology.

  17. Avian Influenza Ecology in North Atlantic Sea Ducks: Not All Ducks Are Created Equal

    PubMed Central

    Hall, Jeffrey S.; Russell, Robin E.; Franson, J. Christian; Soos, Catherine; Dusek, Robert J.; Allen, R. Bradford; Nashold, Sean W.; TeSlaa, Joshua L.; Jónsson, Jón Eínar; Ballard, Jennifer R.; Harms, Naomi Jane; Brown, Justin D.

    2015-01-01

    Wild waterfowl are primary reservoirs of avian influenza viruses (AIV). However the role of sea ducks in the ecology of avian influenza, and how that role differs from freshwater ducks, has not been examined. We obtained and analyzed sera from North Atlantic sea ducks and determined the seroprevalence in those populations. We also tested swab samples from North Atlantic sea ducks for the presence of AIV. We found relatively high serological prevalence (61%) in these sea duck populations but low virus prevalence (0.3%). Using these data we estimated that an antibody half-life of 141 weeks (3.2 years) would be required to attain these prevalences. These findings are much different than what is known in freshwater waterfowl and have implications for surveillance efforts, AIV in marine environments, and the roles of sea ducks and other long-lived waterfowl in avian influenza ecology. PMID:26677841

  18. Avian Influenza Ecology in North Atlantic Sea Ducks: Not All Ducks Are Created Equal.

    PubMed

    Hall, Jeffrey S; Russell, Robin E; Franson, J Christian; Soos, Catherine; Dusek, Robert J; Allen, R Bradford; Nashold, Sean W; TeSlaa, Joshua L; Jónsson, Jón Eínar; Ballard, Jennifer R; Harms, Naomi Jane; Brown, Justin D

    2015-01-01

    Wild waterfowl are primary reservoirs of avian influenza viruses (AIV). However the role of sea ducks in the ecology of avian influenza, and how that role differs from freshwater ducks, has not been examined. We obtained and analyzed sera from North Atlantic sea ducks and determined the seroprevalence in those populations. We also tested swab samples from North Atlantic sea ducks for the presence of AIV. We found relatively high serological prevalence (61%) in these sea duck populations but low virus prevalence (0.3%). Using these data we estimated that an antibody half-life of 141 weeks (3.2 years) would be required to attain these prevalences. These findings are much different than what is known in freshwater waterfowl and have implications for surveillance efforts, AIV in marine environments, and the roles of sea ducks and other long-lived waterfowl in avian influenza ecology.

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

  20. Projected pH reductions by 2100 might put deep North Atlantic biodiversity at risk

    NASA Astrophysics Data System (ADS)

    Gehlen, M.; Séférian, R.; Jones, D. O. B.; Roy, T.; Roth, R.; Barry, J.; Bopp, L.; Doney, S. C.; Dunne, J. P.; Heinze, C.; Joos, F.; Orr, J. C.; Resplandy, L.; Segschneider, J.; Tjiputra, J.

    2014-12-01

    This study aims to evaluate the potential for impacts of ocean acidification on North Atlantic deep-sea ecosystems in response to IPCC AR5 Representative Concentration Pathways (RCPs). Deep-sea biota is likely highly vulnerable to changes in seawater chemistry and sensitive to moderate excursions in pH. Here we show, from seven fully coupled Earth system models, that for three out of four RCPs over 17% of the seafloor area below 500 m depth in the North Atlantic sector will experience pH reductions exceeding -0.2 units by 2100. Increased stratification in response to climate change partially alleviates the impact of ocean acidification on deep benthic environments. We report on major pH reductions over the deep North Atlantic seafloor (depth >500 m) and at important deep-sea features, such as seamounts and canyons. By 2100, and under the high CO2 scenario RCP8.5, pH reductions exceeding -0.2 (-0.3) units are projected in close to 23% (~15%) of North Atlantic deep-sea canyons and ~8% (3%) of seamounts - including seamounts proposed as sites of marine protected areas. The spatial pattern of impacts reflects the depth of the pH perturbation and does not scale linearly with atmospheric CO2 concentration. Impacts may cause negative changes of the same magnitude or exceeding the current target of 10% of preservation of marine biomes set by the convention on biological diversity, implying that ocean acidification may offset benefits from conservation/management strategies relying on the regulation of resource exploitation.

  1. 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.

  2. 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.)

  3. 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...

  4. Using Species-Area Relationships to Inform Baseline Conservation Targets for the Deep North East Atlantic

    PubMed Central

    Foster, Nicola L.; Foggo, Andrew; Howell, Kerry L.

    2013-01-01

    Demands on the resources of the deep-sea have increased in recent years. Consequently, the need to create and implement a comprehensive network of Marine Protected Areas (MPAs) to help manage and protect these resources has become a global political priority. Efforts are currently underway to implement MPA networks in the deep North East Atlantic. To ensure these networks are effective, it is essential that baseline information be available to inform the conservation planning process. Using empirical data, we calculated conservation targets for sessile benthic invertebrates in the deep North East Atlantic for consideration during the planning process. We assessed Species-Area Relationships across two depth bands (200–1100 m and 1100–1800 m) and nine substrata. Conservation targets were predicted for each substratum within each depth band using z-values obtained from fitting a power model to the Species-Area Relationships of observed and estimated species richness (Chao1). Results suggest an MPA network incorporating 10% of the North East Atlantic’s deep-sea area would protect approximately 58% and 49% of sessile benthic species for the depth bands 200–1100 m and 1100–1800 m, respectively. Species richness was shown to vary with substratum type indicating that, along with depth, substratum information needs to be incorporated into the conservation planning process to ensure the most effective MPA network is implemented in the deep North East Atlantic. PMID:23527053

  5. Early arrival of Southern Source Water in the deep North Atlantic prior to Heinrich event 2

    NASA Astrophysics Data System (ADS)

    Gutjahr, Marcus; Lippold, JöRg

    2011-06-01

    The Atlantic Meridional Overturning Circulation (AMOC) plays an important role in the Northern Hemisphere climate system. Significant interest went into the question of how excessive freshwater input through melting of continental ice can affect its overturning vigor and, hence, heat supply, to higher northern latitudes. Such forcing can be tested by investigating its behavior during extreme iceberg discharge events into the open North Atlantic during the last glacial period, the so-called Heinrich events (HE). Here we present neodymium (Nd) isotope compositions of past seawater, a sensitive chemical water mass tag, extracted from sediments of Ocean Drilling Program Site 1063 in the western North Atlantic (Bermuda Rise), covering the period surrounding HE 2, the Last Glacial Maximum, and the early deglaciation. These data are compared with a record of the kinematic circulation tracer (231Pa/230Th)xs extracted from the same sediment core. Both tracers indicate significant circulation changes preceding intense ice rafting during HE 2 by almost 2 kyr. Moreover, the Nd isotope record suggests the presence of deeply ventilating North Atlantic Deep Water early during Marine Isotope Stage 2 until it was replaced by Southern Source Water at ˜27 ka. The early switch to high (Pa/Th)xs and radiogenic ɛNd in relation to intensified ice rafting during HE 2 suggests that ice rafting into the open North Atlantic during major HE 2 was preceded by an early change of the AMOC. This opens the possibility that variations in AMOC contributed to or even triggered the ice sheet instability rather than merely responding to it.

  6. Barriers to Gene Flow in the Marine Environment: Insights from Two Common Intertidal Limpet Species of the Atlantic and Mediterranean

    PubMed Central

    Sá-Pinto, Alexandra; Branco, Madalena S.; Alexandrino, Paulo B.; Fontaine, Michaël C.; Baird, Stuart J. E.

    2012-01-01

    Knowledge of the scale of dispersal and the mechanisms governing gene flow in marine environments remains fragmentary despite being essential for understanding evolution of marine biota and to design management plans. We use the limpets Patella ulyssiponensis and Patella rustica as models for identifying factors affecting gene flow in marine organisms across the North-East Atlantic and the Mediterranean Sea. A set of allozyme loci and a fragment of the mitochondrial gene cytochrome C oxidase subunit I were screened for genetic variation through starch gel electrophoresis and DNA sequencing, respectively. An approach combining clustering algorithms with clinal analyses was used to test for the existence of barriers to gene flow and estimate their geographic location and abruptness. Sharp breaks in the genetic composition of individuals were observed in the transitions between the Atlantic and the Mediterranean and across southern Italian shores. An additional break within the Atlantic cluster separates samples from the Alboran Sea and Atlantic African shores from those of the Iberian Atlantic shores. The geographic congruence of the genetic breaks detected in these two limpet species strongly supports the existence of transpecific barriers to gene flow in the Mediterranean Sea and Northeastern Atlantic. This leads to testable hypotheses regarding factors restricting gene flow across the study area. PMID:23239977

  7. Barriers to gene flow in the marine environment: insights from two common intertidal limpet species of the Atlantic and Mediterranean.

    PubMed

    Sá-Pinto, Alexandra; Branco, Madalena S; Alexandrino, Paulo B; Fontaine, Michaël C; Baird, Stuart J E

    2012-01-01

    Knowledge of the scale of dispersal and the mechanisms governing gene flow in marine environments remains fragmentary despite being essential for understanding evolution of marine biota and to design management plans. We use the limpets Patella ulyssiponensis and Patella rustica as models for identifying factors affecting gene flow in marine organisms across the North-East Atlantic and the Mediterranean Sea. A set of allozyme loci and a fragment of the mitochondrial gene cytochrome C oxidase subunit I were screened for genetic variation through starch gel electrophoresis and DNA sequencing, respectively. An approach combining clustering algorithms with clinal analyses was used to test for the existence of barriers to gene flow and estimate their geographic location and abruptness. Sharp breaks in the genetic composition of individuals were observed in the transitions between the Atlantic and the Mediterranean and across southern Italian shores. An additional break within the Atlantic cluster separates samples from the Alboran Sea and Atlantic African shores from those of the Iberian Atlantic shores. The geographic congruence of the genetic breaks detected in these two limpet species strongly supports the existence of transpecific barriers to gene flow in the Mediterranean Sea and Northeastern Atlantic. This leads to testable hypotheses regarding factors restricting gene flow across the study area.

  8. 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.

  9. Trace elements in the atmosphere over the North Atlantic

    NASA Astrophysics Data System (ADS)

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

    1995-01-01

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

  10. Century-scale variability of Coralline Algal Calcification Rates in the North Pacific and North Atlantic

    NASA Astrophysics Data System (ADS)

    Halfar, J.; Chan, P.; Adey, W.; Hetzinger, S.; Williams, B.; Steneck, R.; Lebednik, P.

    2012-04-01

    Ocean acidification may inhibit calcification pathways of marine plants and animals. Recently, it has been suggested that aragonitic tropical corals and other marine calcifiers already exhibit declining calcification rates. Greater oceanic CO2 uptake at mid-to-high latitudes may result in greater inhibition of calcium carbonate secretion in subarctic organisms than in those at lower latitudes. Such inhibition may be particularly evident in the metabolically expensive high Mg-calcite skeletons of the shallow-water, habitat-forming coralline algae. It has been shown that biogenic high Mg-calcites exceed the solubility of aragonite at approximately 12 mol% MgCO3. Here we present the first century-scale records of calcification rates in the coralline alga Clathromorphum sp. from the North Pacific/Bering Sea region and the subarctic NW Atlantic. Clathromorphum forms annual growth increments in its massive skeleton and is known to have a lifespan of up to several centuries. The seasonal MgCO3 range in Clathromorphum from our subarctic collection sites fluctuates between 10-15 mol%. Century-long time series of calcification rates - the product of skeletal density and linear extension - were generated at submonthly resolution using Micro Computer Tomography. Results indicate that coralline algal calcification rates display multidecadal cycles that covary with regional climate indices such as the Pacific Decadal Oscillation. Unlike studies of other marine calcifiers, this study has not detected a significant decline in calcification rates during the past decades. This is likely attributable to Clathromorphum calcification being metabolically driven, with the organism maintaining significant physiological control over both placement and dissolution of carbonate. Most carbonate in Clathromorphum cells is deposited along an inner wall embedded in an organic matrix of very small, radially-placed high magnesium calcite crystals.

  11. Extratropical North Atlantic SST influence on Sahel rainfall

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Chiang, J. C.

    2013-12-01

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

  12. North Atlantic ecosystem sensitivity to Holocene shifts in Meridional Overturning Circulation

    NASA Astrophysics Data System (ADS)

    Douarin, Mélanie; Elliot, Mary; Noble, Stephen R.; Moreton, Steven G.; Long, David; Sinclair, Daniel; Henry, Lea-Anne; Roberts, J. Murray

    2016-01-01

    Rapid changes in North Atlantic climate over the last millennia were driven by coupled sea surface/atmospheric processes and rates of deep water formation. Holocene climate changes, however, remain poorly documented due to a lack of high-resolution paleoclimate records, and their impacts on marine ecosystems remain unknown. We present a 4500 year absolute-dated sea surface radiocarbon record from northeast Atlantic cold-water corals. In contrast to the current view that surface ocean changes occurred on millennial-scale cycles, our record shows more abrupt changes in surface circulation. Changes were centered at 3.4, 2.7, 1.7, and 1.2 kyr B.P. and associated with atmospheric reorganization. Solar irradiance may have influenced these anomalies but changes in North Atlantic deep water convection are likely to have amplified these signals. Critically, we provide the first evidence that these perturbations in Atlantic Meridional Overturning Circulation led to the decline of cold-water coral ecosystems from 1.2 to ~ 0.1 kyr B.P.

  13. The diversity of cyanomyovirus populations along a North-South Atlantic Ocean transect.

    PubMed

    Jameson, Eleanor; Mann, Nicholas H; Joint, Ian; Sambles, Christine; Mühling, Martin

    2011-11-01

    Viruses that infect the marine cyanobacterium Prochlorococcus have the potential to impact the growth, productivity, diversity and abundance of their hosts. In this study, changes in the microdiversity of cyanomyoviruses were investigated in 10 environmental samples taken along a North-South Atlantic Ocean transect using a myoviral-specific PCR-sequencing approach. Phylogenetic analyses of 630 viral g20 clones from this study, with 786 published g20 sequences, revealed that myoviral populations in the Atlantic Ocean had higher diversity than previously reported, with several novel putative g20 clades. Some of these clades were detected throughout the Atlantic Ocean. Multivariate statistical analyses did not reveal any significant correlations between myoviral diversity and environmental parameters, although myoviral diversity appeared to be lowest in samples collected from the north and south of the transect where Prochlorococcus diversity was also lowest. The results were correlated to the abundance and diversity of the co-occurring Prochlorococcus and Synechococcus populations, but revealed no significant correlations to either of the two potential host genera. This study provides evidence that cyanophages have extremely high and variable diversity and are distributed over large areas of the Atlantic Ocean.

  14. Solar forcing of North Atlantic surface temperature and salinity over the past millennium

    NASA Astrophysics Data System (ADS)

    Moffa-Sánchez, Paola; Born, Andreas; Hall, Ian R.; Thornalley, David J. R.; Barker, Stephen

    2014-04-01

    There were several centennial-scale fluctuations in the climate and oceanography of the North Atlantic region over the past 1,000 years, including a period of relative cooling from about AD 1450 to 1850 known as the Little Ice Age. These variations may be linked to changes in solar irradiance, amplified through feedbacks including the Atlantic meridional overturning circulation. Changes in the return limb of the Atlantic meridional overturning circulation are reflected in water properties at the base of the mixed layer south of Iceland. Here we reconstruct thermocline temperature and salinity in this region from AD 818 to 1780 using paired δ18O and Mg/Ca ratio measurements of foraminifer shells from a subdecadally resolved marine sediment core. The reconstructed centennial-scale variations in hydrography correlate with variability in total solar irradiance. We find a similar correlation in a simulation of climate over the past 1,000 years. We infer that the hydrographic changes probably reflect variability in the strength of the subpolar gyre associated with changes in atmospheric circulation. Specifically, in the simulation, low solar irradiance promotes the development of frequent and persistent atmospheric blocking events, in which a quasi-stationary high-pressure system in the eastern North Atlantic modifies the flow of the westerly winds. We conclude that this process could have contributed to the consecutive cold winters documented in Europe during the Little Ice Age.

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

    PubMed Central

    Vermeij, Geerat J

    2005-01-01

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

  16. 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.

  17. Comparative ecology of North Atlantic shores: do differences in players matter for process?

    PubMed

    Jenkins, Stuart R; Moore, Pippa; Burrows, Michael T; Garbary, David J; Hawkins, Stephen J; Ingólfsson, Agnar; Sebens, Kenneth P; Snelgrove, Paul V R; Wethey, David S; Woodin, Sarah A

    2008-11-01

    The contrasting histories of the western and eastern shores of the North Atlantic Ocean provide an excellent opportunity to consider the implications of past events for present ecological processes and the functioning of marine ecosystems. Similarities and differences in assemblage composition have been driven by large-scale events, such as the trans-Arctic interchange, which has shaped the species pool, and cycles of glaciation, which have determined phases of local or regional extinction and colonization. More recently, anthropogenically induced invasions and local extinctions have significantly altered biogeographic distributions. Here we consider for both hard and soft substrata how the presence or absence of key taxa influences the outcomes of trophic and other biological interactions, and evaluate the consequences for community structure and ecosystem functioning. On intertidal hard substratum shores, biodiversity of epilithic microphagous grazers differs across latitudinal and longitudinal scales. Diversity is high in southern Europe but declines to the north and across the Atlantic. Lower diversity and the absence of patellid limpets in Iceland and the northwest Atlantic compared to Europe result in differences in consumer pressure, and an apparent contrast in the importance of herbivory vs. competitive interactions and predation pressure as community structuring processes. Interestingly, despite differences in "process," community patterns are remarkably similar between the east and west. On soft sediment shores, there are conspicuous geographic differences in importance of bioturbators and large digging predators. Hemichordates can be abundant and important infaunal bioturbators in the western Atlantic, but they generally play a much reduced role in the eastern Atlantic. In addition, the number and diversity of digging predators on western Atlantic shores is high; the horseshoe crab, swimming portunid crabs, large whelks, excavating waterfowl, and an

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

    NASA Astrophysics Data System (ADS)

    Brown, Eric L.; Lesher, Charles E.

    2014-11-01

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

  19. Bathymetric terrain model of the Atlantic margin for marine geological investigations

    USGS Publications Warehouse

    Andrews, Brian D.; Chaytor, Jason D.; ten Brink, Uri S.; Brothers, Daniel S.; Gardner, James V.; Lobecker, Elizabeth A.; Calder, Brian R.

    2016-01-01

    A bathymetric terrain model of the Atlantic margin covering almost 725,000 square kilometers of seafloor from the New England Seamounts in the north to the Blake Basin in the south is compiled from existing multibeam bathymetric data for marine geological investigations. Although other terrain models of the same area are extant, they are produced from either satellite-derived bathymetry at coarse resolution (ETOPO1), or use older bathymetric data collected by using a combination of single beam and multibeam sonars (Coastal Relief Model). The new multibeam data used to produce this terrain model have been edited by using hydrographic data processing software to maximize the quality, usability, and cartographic presentation of the combined 100-meter resolution grid. The final grid provides the largest high-resolution, seamless terrain model of the Atlantic margin..

  20. Hydrographic changes in the subpolar North Atlantic at the MCA to LIA transition

    NASA Astrophysics Data System (ADS)

    Divine, Dmitry; Miettinen, Arto; Husum, Katrine; Koc, Nalan

    2016-04-01

    A network of four marine sediment cores from the northern North Atlantic is used to study hydrographic changes in surface water masses during the last 2000 years with a special focus on the Medieval Climate Anomaly (MCA) to the Little Ice Age (LIA) transition. Three of the cores are recovered from the sites located on main pathways of warm Atlantic water to the Arctic: M95-2011 (Vøring plateau, Norwegian Sea), Rapid-21 COM and LO-14 (Reykjanes Ridge, south of Iceland). The fourth core MD99-2322 is from the SE Greenland shelf (Denmark Strait), and it is influenced by the cold water outflow from the Arctic. The cores were analyzed continuously for planktonic diatoms with a high decadal to subdecadal temporal resolution. Past changes in the spatial distribution of surface water masses have been studied identifying factors, or typical species compositions, in downcore diatom assemblages. To derive the factors a Q-mode factor analysis has been applied to the extended modern calibration data set of 184 surface sediment samples from the North Atlantic, the Labrador Sea, the Nordic Seas, and Baffin Bay. SSTs have also been reconstructed using transfer functions. Variations of the reconstructed SSTs and loadings of major contributing factors reveal a complex regional pattern of changes in the structure of circulation during the MCA/LIA transition (1200-1400 AD). In the Norwegian Sea, the factors associated with assemblages typical for warmer and saline North Atlantic waters are partly displaced by colder and fresher water dwelling diatoms suggesting an eastward migration of mixed Arctic/Atlantic water masses into the Norwegian Sea. The two cores south of Iceland show a westward propagation of a warm water pulse as evidenced by the dominance of assemblages, which today are typical for the waters ca 5° further south than the current study sites. At the SE Greenland shelf an abrupt shift (ca. 50 years) in factors associated with different sea ice zone dwelling diatoms

  1. Climate influence on Vibrio and associated human diseases during the past half-century in the coastal North Atlantic.

    PubMed

    Vezzulli, Luigi; Grande, Chiara; Reid, Philip C; Hélaouët, Pierre; Edwards, Martin; Höfle, Manfred G; Brettar, Ingrid; Colwell, Rita R; Pruzzo, Carla

    2016-08-23

    Climate change is having a dramatic impact on marine animal and plant communities but little is known of its influence on marine prokaryotes, which represent the largest living biomass in the world oceans and play a fundamental role in maintaining life on our planet. In this study, for the first time to our knowledge, experimental evidence is provided on the link between multidecadal climatic variability in the temperate North Atlantic and the presence and spread of an important group of marine prokaryotes, the vibrios, which are responsible for several infections in both humans and animals. Using archived formalin-preserved plankton samples collected by the Continuous Plankton Recorder survey over the past half-century (1958-2011), we assessed retrospectively the relative abundance of vibrios, including human pathogens, in nine areas of the North Atlantic and North Sea and showed correlation with climate and plankton changes. Generalized additive models revealed that long-term increase in Vibrio abundance is promoted by increasing sea surface temperatures (up to ∼1.5 °C over the past 54 y) and is positively correlated with the Northern Hemisphere Temperature (NHT) and Atlantic Multidecadal Oscillation (AMO) climatic indices (P < 0.001). Such increases are associated with an unprecedented occurrence of environmentally acquired Vibrio infections in the human population of Northern Europe and the Atlantic coast of the United States in recent years. PMID:27503882

  2. Climate influence on Vibrio and associated human diseases during the past half-century in the coastal North Atlantic.

    PubMed

    Vezzulli, Luigi; Grande, Chiara; Reid, Philip C; Hélaouët, Pierre; Edwards, Martin; Höfle, Manfred G; Brettar, Ingrid; Colwell, Rita R; Pruzzo, Carla

    2016-08-23

    Climate change is having a dramatic impact on marine animal and plant communities but little is known of its influence on marine prokaryotes, which represent the largest living biomass in the world oceans and play a fundamental role in maintaining life on our planet. In this study, for the first time to our knowledge, experimental evidence is provided on the link between multidecadal climatic variability in the temperate North Atlantic and the presence and spread of an important group of marine prokaryotes, the vibrios, which are responsible for several infections in both humans and animals. Using archived formalin-preserved plankton samples collected by the Continuous Plankton Recorder survey over the past half-century (1958-2011), we assessed retrospectively the relative abundance of vibrios, including human pathogens, in nine areas of the North Atlantic and North Sea and showed correlation with climate and plankton changes. Generalized additive models revealed that long-term increase in Vibrio abundance is promoted by increasing sea surface temperatures (up to ∼1.5 °C over the past 54 y) and is positively correlated with the Northern Hemisphere Temperature (NHT) and Atlantic Multidecadal Oscillation (AMO) climatic indices (P < 0.001). Such increases are associated with an unprecedented occurrence of environmentally acquired Vibrio infections in the human population of Northern Europe and the Atlantic coast of the United States in recent years.

  3. Anthropogenic climate change drives shift and shuffle in North Atlantic phytoplankton communities.

    PubMed

    Barton, Andrew D; Irwin, Andrew J; Finkel, Zoe V; Stock, Charles A

    2016-03-15

    Anthropogenic climate change has shifted the biogeography and phenology of many terrestrial and marine species. Marine phytoplankton communities appear sensitive to climate change, yet understanding of how individual species may respond to anthropogenic climate change remains limited. Here, using historical environmental and phytoplankton observations, we characterize the realized ecological niches for 87 North Atlantic diatom and dinoflagellate taxa and project changes in species biogeography between mean historical (1951-2000) and future (2051-2100) ocean conditions. We find that the central positions of the core range of 74% of taxa shift poleward at a median rate of 12.9 km per decade (km⋅dec(-1)), and 90% of taxa shift eastward at a median rate of 42.7 km⋅dec(-1) The poleward shift is faster than previously reported for marine taxa, and the predominance of longitudinal shifts is driven by dynamic changes in multiple environmental drivers, rather than a strictly poleward, temperature-driven redistribution of ocean habitats. A century of climate change significantly shuffles community composition by a basin-wide median value of 16%, compared with seasonal variations of 46%. The North Atlantic phytoplankton community appears poised for marked shift and shuffle, which may have broad effects on food webs and biogeochemical cycles. PMID:26903635

  4. Anthropogenic climate change drives shift and shuffle in North Atlantic phytoplankton communities

    PubMed Central

    Barton, Andrew D.; Finkel, Zoe V.; Stock, Charles A.

    2016-01-01

    Anthropogenic climate change has shifted the biogeography and phenology of many terrestrial and marine species. Marine phytoplankton communities appear sensitive to climate change, yet understanding of how individual species may respond to anthropogenic climate change remains limited. Here, using historical environmental and phytoplankton observations, we characterize the realized ecological niches for 87 North Atlantic diatom and dinoflagellate taxa and project changes in species biogeography between mean historical (1951–2000) and future (2051–2100) ocean conditions. We find that the central positions of the core range of 74% of taxa shift poleward at a median rate of 12.9 km per decade (km⋅dec−1), and 90% of taxa shift eastward at a median rate of 42.7 km⋅dec−1. The poleward shift is faster than previously reported for marine taxa, and the predominance of longitudinal shifts is driven by dynamic changes in multiple environmental drivers, rather than a strictly poleward, temperature-driven redistribution of ocean habitats. A century of climate change significantly shuffles community composition by a basin-wide median value of 16%, compared with seasonal variations of 46%. The North Atlantic phytoplankton community appears poised for marked shift and shuffle, which may have broad effects on food webs and biogeochemical cycles. PMID:26903635

  5. Anthropogenic climate change drives shift and shuffle in North Atlantic phytoplankton communities.

    PubMed

    Barton, Andrew D; Irwin, Andrew J; Finkel, Zoe V; Stock, Charles A

    2016-03-15

    Anthropogenic climate change has shifted the biogeography and phenology of many terrestrial and marine species. Marine phytoplankton communities appear sensitive to climate change, yet understanding of how individual species may respond to anthropogenic climate change remains limited. Here, using historical environmental and phytoplankton observations, we characterize the realized ecological niches for 87 North Atlantic diatom and dinoflagellate taxa and project changes in species biogeography between mean historical (1951-2000) and future (2051-2100) ocean conditions. We find that the central positions of the core range of 74% of taxa shift poleward at a median rate of 12.9 km per decade (km⋅dec(-1)), and 90% of taxa shift eastward at a median rate of 42.7 km⋅dec(-1) The poleward shift is faster than previously reported for marine taxa, and the predominance of longitudinal shifts is driven by dynamic changes in multiple environmental drivers, rather than a strictly poleward, temperature-driven redistribution of ocean habitats. A century of climate change significantly shuffles community composition by a basin-wide median value of 16%, compared with seasonal variations of 46%. The North Atlantic phytoplankton community appears poised for marked shift and shuffle, which may have broad effects on food webs and biogeochemical cycles.

  6. Multidecadal Atlantic climate variability and its impact on marine pelagic communities

    NASA Astrophysics Data System (ADS)

    Harris, Victoria; Edwards, Martin; Olhede, Sofia C.

    2014-05-01

    compelling evidence for the hypothesis that cold water species are gradually being replaced by more temperate species in the North Atlantic. This may have detrimental effects for the entire marine ecosystem, by affecting on organisms such as fish larva for example. The second group, a phytoplankton subset consisting primarily of diatom species, is primarily influenced by the AMO rather than the average temperature trend. This result highlights the importance of natural oscillations to certain functional groups, in particular those subgroups which are less directly metabolically affected by changes in temperature.

  7. What drives seasonal change in oligotrophic area in the subtropical North Atlantic?

    NASA Astrophysics Data System (ADS)

    Dave, Apurva C.; Barton, Andrew D.; Lozier, M. Susan; McKinley, Galen A.

    2015-06-01

    The oligotrophic regions of the subtropical gyres cover a significant portion of the global ocean, and exhibit considerable but poorly understood intraseasonal, interannual, and longer-term variations in spatial extent. Here using historical observations of surface ocean nitrate, wind, and currents, we have investigated how horizontal and vertical supplies of nitrate control seasonal changes in the size and shape of oligotrophic regions of the subtropical North Atlantic. In general, the oligotrophic region of the subtropical North Atlantic is associated with the region of weak vertical supply of nitrate. Though the total vertical supply of nitrate here is generally greater than the total horizontal supply, we find that seasonal expansion and contraction of the oligotrophic region is consistent with changes in horizontal supply of nitrate. In this dynamic periphery of the subtropical gyre, the seasonal variations in chlorophyll are linked to variations in horizontal nitrate supply that facilitate changes in intracellular pigment concentrations, and to a lesser extent, phytoplankton biomass. Our results suggest that horizontal transports of nutrient are crucial in setting seasonal cycles of chlorophyll in large expanses of the subtropical North Atlantic, and may play a key and underappreciated role in regulating interannual variations in these globally important marine ecosystems.

  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. 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.

  10. Natural versus anthropogenic factors affecting low-level cloud albedo over the North Atlantic

    NASA Technical Reports Server (NTRS)

    Falkowski, Paul G.; Kim, Yongseung; Kolber, Zbigniew; Wilson, Cara; Wirick, Creighton; Cess, Robert

    1992-01-01

    Cloud albedo plays a key role in regulating earth's climate. Cloud albedo depends on column-integrated liquid water content and the density of cloud condensation nuclei, which consists primarily of submicrometer-sized aerosol sulfate particles. A comparison of two independent satellite data sets suggests that, although anthropogenic sulfate emissions may enhance cloud albedo immediately adjacent to the east coast of the United States, over the central North Atlantic Ocean the variability in albedo can be largely accounted for by natural marine and atmospheric processes that probably have remained relatively constant since the beginning of the industrial revolution.

  11. Links between viruses and prokaryotes throughout the water column along a North Atlantic latitudinal transect.

    PubMed

    De Corte, Daniele; Sintes, Eva; Yokokawa, Taichi; Reinthaler, Thomas; Herndl, Gerhard J

    2012-08-01

    Viruses are an abundant, diverse and dynamic component of marine ecosystems and have a key role in the biogeochemical processes of the ocean by controlling prokaryotic and phytoplankton abundance and diversity. However, most of the studies on virus-prokaryote interactions in marine environments have been performed in nearshore waters. To assess potential variations in the relation between viruses and prokaryotes in different oceanographic provinces, we determined viral and prokaryotic abundance and production throughout the water column along a latitudinal transect in the North Atlantic. Depth-related trends in prokaryotic and viral abundance (both decreasing by one order of magnitude from epi- to abyssopelagic waters), and prokaryotic production (decreasing by three orders of magnitude) were observed along the latitudinal transect. The virus-to-prokaryote ratio (VPR) increased from ~19 in epipelagic to ~53 in the bathy- and abyssopelagic waters. Although the lytic viral production decreased significantly with depth, the lysogenic viral production did not vary with depth. In bathypelagic waters, pronounced differences in prokaryotic and viral abundance were found among different oceanic provinces with lower leucine incorporation rates and higher VPRs in the North Atlantic Gyre province than in the provinces further north and south. The percentage of lysogeny increased from subpolar regions toward the more oligotrophic lower latitudes. Based on the observed trends over this latitudinal transect, we conclude that the viral-host interactions significantly change among different oceanic provinces in response to changes in the biotic and abiotic variables. PMID:22258100

  12. Magnetoclimatology: Teleconnection between the Siberian loess record and North Atlantic Heinrich events

    NASA Astrophysics Data System (ADS)

    Evans, M. E.; Rutter, N. W.; Catto, N.; Chlachula, J.; Nyvlt, D.

    2003-06-01

    New environmental magnetic data from loess and paleosol successions in outcrops in the upper reaches of the Ob River drainage, southern Siberia, track the major climatic variations over the last glacial-interglacial cycle. Profiles of magnetic susceptibility and alternating deposition of loess and soil-formation events correspond to oxygen isotope stages 1 5. The magnetic-susceptibility data, in association with the stratigraphic succession, confirm that the wind-vigor magnetoclimatological model is a viable alternative to the classic pedogenic model. Interpretation of magnetic-susceptibility data from loess- paleosol successions must therefore consider eolian dynamics, available source materials, and transport directions, in addition to pedogenic processes. Rapid magnetic fluctuations are also observed. These are identified—for the first time in Siberian records—as the signature of the abrupt cold pulses responsible for the Heinrich layers in North Atlantic marine sediments. The data thus form a component of climatic teleconnections across the Northern Hemisphere, allowing correlations to be made among (1) Siberian magnetic susceptibility stratigraphy, (2) data recorded from other loess-paleosol successions in China, European Russia, Europe, and North America, (3) North Atlantic ice-rafted detritus, and (4) sea-surface temperatures derived from molecular stratigraphy of marine sediments off the northwest coast of Africa.

  13. VIEW OF SOUTH ELEVATION OF MARINE BARRACKS, LOOKING NORTH NORTHWEST. ...

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

    VIEW OF SOUTH ELEVATION OF MARINE BARRACKS, LOOKING NORTH NORTHWEST. - Naval Computer & Telecommunications Area Master Station, Eastern Pacific, Radio Transmitter Facility Lualualei, Marine Barracks, Intersection of Tower Drive & Morse Street, Makaha, Honolulu County, HI

  14. OBLIQUE VIEW OF FRONT ELEVATION OF MARINE BARRACKS, LOOKING NORTH. ...

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

    OBLIQUE VIEW OF FRONT ELEVATION OF MARINE BARRACKS, LOOKING NORTH. - Naval Computer & Telecommunications Area Master Station, Eastern Pacific, Radio Transmitter Facility Lualualei, Marine Barracks, Intersection of Tower Drive & Morse Street, Makaha, Honolulu County, HI

  15. VIEW OF NORTH ELEVATION OF MARINE BARRACKS, LOOKING SOUTHEAST. ...

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

    VIEW OF NORTH ELEVATION OF MARINE BARRACKS, LOOKING SOUTHEAST. - Naval Computer & Telecommunications Area Master Station, Eastern Pacific, Radio Transmitter Facility Lualualei, Marine Barracks, Intersection of Tower Drive & Morse Street, Makaha, Honolulu County, HI

  16. 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

  17. 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.

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

    PubMed

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

    2014-06-13

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  20. How does the connectivity between populations mediate range limits of marine invertebrates? A case study of larval dispersal between the Bay of Biscay and the English Channel (North-East Atlantic)

    NASA Astrophysics Data System (ADS)

    Ayata, Sakina-Dorothée; Lazure, Pascal; Thiébaut, Éric

    2010-10-01

    For many marine species, larval dispersal plays a crucial role in population persistence, re-colonization of disturbed areas, and distribution of species range limits through the control of population connectivity. Along the French Atlantic coast (NE Atlantic), a biogeographical transition zone has been reported between temperate and cold-temperate marine faunal assemblages. Hydrodynamics in this area are highly complex and variable including numerous mesoscale features (e.g. river plumes, fronts, upwellings, low salinity lenses), which could constrain larval transport and connectivity. In this context, the aim of this study was to assess how hydrodynamic conditions and biological traits influence larval transport and contribute to population connectivity along the biogeographical transition zone between the Bay of Biscay and the English Channel. A coupled bio-physical individual-based model was used at a regional scale to track larval trajectories under realistic hydroclimatic conditions (tides, river run-offs, and meteorological conditions) and for some common life-history traits. Larval particles were released monthly from February to August for the years 2001 to 2005, from 16 spawning populations corresponding to the main bays and estuaries of the study area. Two planktonic larval durations (2 vs. 4 weeks) and three vertical distributions (no swimming behaviour, diel vertical migration, and ontogenic vertical migration) were considered. Dispersal kernels were described by 17 parameters and analysed in a multivariate approach to calculate connectivity matrices and indices. The main factors responsible for the variability of the dispersal kernels were the spawning month in relation to the seasonal variations in river run-offs and wind conditions, the planktonic larval duration, the spawning population location, and the larval behaviour. No significant inter-annual variability was observed. Self-retention rates were high and larval exchanges occurred mainly within

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

    NASA Astrophysics Data System (ADS)

    Boyd, Jessica; Saunders, Mark

    2016-04-01

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

  2. 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

  3. Latitudinal variation in virus-induced mortality of phytoplankton across the North Atlantic Ocean.

    PubMed

    Mojica, Kristina D A; Huisman, Jef; Wilhelm, Steven W; Brussaard, Corina P D

    2016-02-01

    Viral lysis of phytoplankton constrains marine primary production, food web dynamics and biogeochemical cycles in the ocean. Yet, little is known about the biogeographical distribution of viral lysis rates across the global ocean. To address this, we investigated phytoplankton group-specific viral lysis rates along a latitudinal gradient within the North Atlantic Ocean. The data show large-scale distribution patterns of different virus groups across the North Atlantic that are associated with the biogeographical distributions of their potential microbial hosts. Average virus-mediated lysis rates of the picocyanobacteria Prochlorococcus and Synechococcus were lower than those of the picoeukaryotic and nanoeukaryotic phytoplankton (that is, 0.14 per day compared with 0.19 and 0.23 per day, respectively). Total phytoplankton mortality (virus plus grazer-mediated) was comparable to the gross growth rate, demonstrating high turnover rates of phytoplankton populations. Virus-induced mortality was an important loss process at low and mid latitudes, whereas phytoplankton mortality was dominated by microzooplankton grazing at higher latitudes (>56°N). This shift from a viral-lysis-dominated to a grazing-dominated phytoplankton community was associated with a decrease in temperature and salinity, and the decrease in viral lysis rates was also associated with increased vertical mixing at higher latitudes. Ocean-climate models predict that surface warming will lead to an expansion of the stratified and oligotrophic regions of the world's oceans. Our findings suggest that these future shifts in the regional climate of the ocean surface layer are likely to increase the contribution of viral lysis to phytoplankton mortality in the higher-latitude waters of the North Atlantic, which may potentially reduce transfer of matter and energy up the food chain and thus affect the capacity of the northern North Atlantic to act as a long-term sink for CO2. PMID:26262815

  4. Latitudinal variation in virus-induced mortality of phytoplankton across the North Atlantic Ocean.

    PubMed

    Mojica, Kristina D A; Huisman, Jef; Wilhelm, Steven W; Brussaard, Corina P D

    2016-02-01

    Viral lysis of phytoplankton constrains marine primary production, food web dynamics and biogeochemical cycles in the ocean. Yet, little is known about the biogeographical distribution of viral lysis rates across the global ocean. To address this, we investigated phytoplankton group-specific viral lysis rates along a latitudinal gradient within the North Atlantic Ocean. The data show large-scale distribution patterns of different virus groups across the North Atlantic that are associated with the biogeographical distributions of their potential microbial hosts. Average virus-mediated lysis rates of the picocyanobacteria Prochlorococcus and Synechococcus were lower than those of the picoeukaryotic and nanoeukaryotic phytoplankton (that is, 0.14 per day compared with 0.19 and 0.23 per day, respectively). Total phytoplankton mortality (virus plus grazer-mediated) was comparable to the gross growth rate, demonstrating high turnover rates of phytoplankton populations. Virus-induced mortality was an important loss process at low and mid latitudes, whereas phytoplankton mortality was dominated by microzooplankton grazing at higher latitudes (>56°N). This shift from a viral-lysis-dominated to a grazing-dominated phytoplankton community was associated with a decrease in temperature and salinity, and the decrease in viral lysis rates was also associated with increased vertical mixing at higher latitudes. Ocean-climate models predict that surface warming will lead to an expansion of the stratified and oligotrophic regions of the world's oceans. Our findings suggest that these future shifts in the regional climate of the ocean surface layer are likely to increase the contribution of viral lysis to phytoplankton mortality in the higher-latitude waters of the North Atlantic, which may potentially reduce transfer of matter and energy up the food chain and thus affect the capacity of the northern North Atlantic to act as a long-term sink for CO2.

  5. GLANAM (Glaciated North Atlantic Margins): A Marie Curie Initial Training Network between Norway, the UK & Denmark

    NASA Astrophysics Data System (ADS)

    Petter Sejrup, Hans; Oline Hjelstuen, Berit

    2015-04-01

    GLANAM (Glaciated North Atlantic Margins) is an Initial Training Network (ITN) funded under the EU Marie Curie Programme. It comprises 10 research partners from Norway, UK and Denmark, including 7 University research teams, 1 industrial full partner and 2 industrial associate partners. The GLANAM network will employ and train 15 early career researchers (Fellows). The aim of GLANAM is to improve the career prospects and development of young researchers in both the public and private sector within the field of earth science, focusing on North Atlantic glaciated margins. The young scientists will perform multi-disciplinary research and receive training in geophysics, remote sensing, GIS, sedimentology, geomorphology, stratigraphy, geochemistry and numerical modeling through three interconnected work packages that collectively address knowledge gaps related to the large, glacial age, sedimentary depocentres on the North Atlantic margin. The 15 Fellows will work on projects that geographically extend from Ireland in the south to the High Arctic. Filling these gaps will not only result in major new insights regarding glacial age processes on continental margins in general, but will also provide paleoclimate information essential for understanding the role of marine-based ice sheets in the climate system and for the testing of climate models. GLANAM brings together leading European research groups working on glaciated margins in a coordinated and collaborative research and training project. Focusing on the North Atlantic margins, this coordinated approach will lead to a major advance in the understanding of glaciated margins more widely and will fundamentally strengthen European research and build capacity in this field.

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

    PubMed Central

    2014-01-01

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

  7. Synchronous climate changes in antarctica and the north atlantic

    PubMed

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

    1998-10-01

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

  8. 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.

  9. 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.

  10. Synchronous climate changes in antarctica and the north atlantic

    PubMed

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

    1998-10-01

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

  11. 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.

  12. The arctic mirage and the early north atlantic.

    PubMed

    Sawatzky, H L; Lehn, W H

    1976-06-25

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

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

    PubMed

    Straneo, Fiammetta; Heimbach, Patrick

    2013-12-01

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

  14. North Atlantic ocean circulation and abrupt climate change during the last glaciation

    NASA Astrophysics Data System (ADS)

    Henry, L. G.; McManus, J. F.; Curry, W. B.; Roberts, N. L.; Piotrowski, A. M.; Keigwin, L. D.

    2016-07-01

    The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ13C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean’s persistent, central role in abrupt glacial climate change.

  15. North Atlantic ocean circulation and abrupt climate change during the last glaciation.

    PubMed

    Henry, L G; McManus, J F; Curry, W B; Roberts, N L; Piotrowski, A M; Keigwin, L D

    2016-07-29

    The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ(13)C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in abrupt glacial climate change.

  16. North Atlantic ocean circulation and abrupt climate change during the last glaciation.

    PubMed

    Henry, L G; McManus, J F; Curry, W B; Roberts, N L; Piotrowski, A M; Keigwin, L D

    2016-07-29

    The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ(13)C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in abrupt glacial climate change. PMID:27365315

  17. North Atlantic overturning and climate response to meltwater forcing during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Muschitiello, Francesco; Dokken, Trond; Väliranta, Minna; Björck, Svante; Davies, Siwan; Luoto, Tomi; Schenk, Frederik; Smittenberg, Rienk; Reimer, Paula; Wohlfarth, Barbara

    2016-04-01

    The last deglaciation (˜18-11 kyr BP) is an important analog to investigate the response of the Atlantic Meridional Overturning Circulation (AMOC) to future ice-sheet melting and its impact on regional climate change. In this study we present synchronised terrestrial and marine proxy records that provide insight into freshwater run-off and climate variability in the eastern North Atlantic during the last deglaciation. The reconstructions show that atmospheric circulation rather than freshwater forcing primarily controls the stability of the AMOC. However, catastrophic meltwater drainage from the Scandinavian continent may have solicited complex feedbacks necessary to account for the rapid large-scale hydro-climate shifts and the major weakening of the overturning circulation system at the onset of the Younger Dryas stadial.

  18. Atlantic cooling associated with a marine biotic crisis during the mid-Cretaceous period

    NASA Astrophysics Data System (ADS)

    McAnena, A.; Flögel, S.; Hofmann, P.; Herrle, J. O.; Griesand, A.; Pross, J.; Talbot, H. M.; Rethemeyer, J.; Wallmann, K.; Wagner, T.

    2013-07-01

    Most of the marine biotic crises that occurred during the hot Mesozoic era have been linked to episodes of extreme warmth. Others, however, may have occurred during cooler intervals that interrupted Cretaceous greenhouse warmth. There are some indications of cooling in the late Aptian (116-114Myr ago), but it has not been definitively linked to biotic crisis. Here we assess the timing and magnitude of late Aptian cooling and its association with biotic crises using a suite of geochemical and micropalaeontological assessments from a marine sediment core from the North Atlantic Ocean as well as global biogeochemical modelling. Sea surface temperatures derived from the TEX86 proxy suggest that surface waters cooled by about 5°C during the two million years, coincident with a positive δ13C excursion of approximately 2‰ in carbonates and organic carbon. Surface productivity was enhanced during this period, but the abundance of planktonic foraminifera and nannoconid phytoplankton declined. Our simulations with a biogeochemical model indicate that the δ13C excursion associated with the cooling could be explained by the burial of about 812,000 gigatons of carbon over 2.5 million years. About 50% of the this carbon burial occurred in the Atlantic, Southern and Tethys ocean basins. We conclude that global cooling during greenhouse conditions can cause perturbations to marine ecosystems and biogeochemical cycles at scales comparable to those associated with global warming.

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

    PubMed

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

    2012-07-01

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

  20. Squid as nutrient vectors linking Southwest Atlantic marine ecosystems

    NASA Astrophysics Data System (ADS)

    Arkhipkin, Alexander I.

    2013-10-01

    Long-term investigations of three abundant nektonic squid species from the Southwest Atlantic, Illex argentinus, Doryteuthis gahi and Onykia ingens, permitted to estimate important population parameters including individual growth rates, duration of ontogenetic phases and mortalities. Using production model, the productivity of squid populations at different phases of their life cycle was assessed and the amount of biomass they convey between marine ecosystems as a result of their ontogenetic migrations was quantified. It was found that squid are major nutrient vectors and play a key role as transient 'biological pumps' linking spatially distinct marine ecosystems. I. argentinus has the largest impact in all three ecosystems it encounters due to its high abundance and productivity. The variable nature of squid populations increases the vulnerability of these biological conveyers to overfishing and environmental change. Failure of these critical biological pathways may induce irreversible long-term consequences for biodiversity, resource abundance and spatial availability in the world ocean.

  1. The 14C age of glacial North Atlantic surface waters: Greenland Interstadial Events 2-13

    NASA Astrophysics Data System (ADS)

    Austin, William; Hibbert, Fiona; Bard, Edouard; Bryant, Charlotte

    2016-04-01

    We present an updated compilation of surface ocean (Globigerina bulloides) AMS 14C ages for Greenland Interstadials (GI) 2-13, spanning the interval 25,000 - 45,000 cal BP from the mid-latitude NE Atlantic Ocean. New data from two marine sediment cores located 83 km apart in the NE Atlantic are presented: MD95-2006 (Barra Fan; 57°01.82 N, 10°03.48 W; 2120m water depth) and MD04-2822 (Rockall Trough; 56°50.54 N, 11°22.96 W; 2344m water depth) as well as published data from core MD95-2042 (Iberian Margin; 37°45'N, 10°10'W, 3146 m water depth). Replicated sea surface temperature (SST) records show evidence for abrupt warming events; we correlate these directly to the D/O cycles of the Greenland (NGRIP) ice-core oxygen isotope record. We test the proposed synchronization of two of these records using three geochemically distinct tephra isochrones (NAAZ-1, Fugloyarbanki and NAAZ-2). Our data provide a potentially useful new surface ocean composite record of 14C age from the mid-latitude North Atlantic, suggesting broadly consistent interstadial 14C age data from all three records; and highlight the advantage of tuning mid-latitude SST records to Greenland (tested with tephra isochrones where possible) when constructing marine age-models through this time interval.

  2. Developing an acoustic method for reducing North Atlantic right whale (Eubalaena glacialis) ship strike mortality along the United States eastern seaboard

    NASA Astrophysics Data System (ADS)

    Mullen, Kaitlyn Allen

    strike mortality within United States waters. I recommend that future work include additional prototype modifications and testing, application for a marine mammal scientific take authorization permit to test the modified prototype on multiple mysticete species, and continued interfacing of the prototype with evolving United States North Atlantic right whale ship strike reduction policies.

  3. Mapping the Origins of Chromophoric Dissolved Organic Matter in the North Atlantic Subtropical Gyre

    NASA Astrophysics Data System (ADS)

    McDonald, N.; Logendran, V.; Evans, D. G.; Peters, A.; Nelson, N. B.

    2010-12-01

    The chromophoric or "light-absorbing" fraction of dissolved organic matter plays a significant role in the regulation of the underwater light field. In the North Atlantic subtropical gyre, it's origins vary, and include contributions from both terrestrial and marine sources. Furthermore, within the fraction of marine-origin CDOM, there are distinctions between that of local origin and that coming from other regions via transport through water masses or through atmospheric deposition. As the optical and chemical properties of CDOM depend largely on its source, an analysis of its origins could lead to a better understanding of processes in the North Atlantic subtropical gyre. For this analysis, we have used absorption data from CDOM measurements collected repeatedly for a number of years at the BATS site in the Sargasso Sea. Samples have been collected at the same series of depths ranging from surface waters to 4200 meters. The samples were analyzed using a dual beam spectrophotometer to obtain absorption spectra. The slope parameter, S, provides more in depth information about the source of CDOM than does the absorption spectra alone, and thus we have used it as well as the slope ratio, Sr, for differentiating between different types of CDOM. Slope ratios were obtained by selecting portions of the spectral slope at wavelength ranges, which have been found to be indicative of CDOM originating from a particular source. For example, it can be used to distinguish marine CDOM formed locally in the Sargasso Sea from that which has been formed further north in the Atlantic and then subducted and transported to the Sargasso. There are various other methods for ascertaining the sources of CDOM, and the most comprehensive model for CDOM in the North Atlantic is likely obtained using a combination of all of them. Excitation-emission matrix spectra (EEMS) have been performed on samples from the same site in the Sargasso Sea to corroborate findings from the S and Sr analyses

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  5. Human Activities on the Deep Seafloor in the North East Atlantic: An Assessment of Spatial Extent

    PubMed Central

    Benn, Angela R.; Weaver, Philip P.; Billet, David S. M.; van den Hove, Sybille; Murdock, Andrew P.; Doneghan, Gemma B.; Le Bas, Tim

    2010-01-01

    Background Environmental impacts of human activities on the deep seafloor are of increasing concern. While activities within waters shallower than 200 m have been the focus of previous assessments of anthropogenic impacts, no study has quantified the extent of individual activities or determined the relative severity of each type of impact in the deep sea. Methodology The OSPAR maritime area of the North East Atlantic was chosen for the study because it is considered to be one of the most heavily impacted by human activities. In addition, it was assumed data would be accessible and comprehensive. Using the available data we map and estimate the spatial extent of five major human activities in the North East Atlantic that impact the deep seafloor: submarine communication cables, marine scientific research, oil and gas industry, bottom trawling and the historical dumping of radioactive waste, munitions and chemical weapons. It was not possible to map military activities. The extent of each activity has been quantified for a single year, 2005. Principal Findings Human activities on the deep seafloor of the OSPAR area of the North Atlantic are significant but their footprints vary. Some activities have an immediate impact after which seafloor communities could re-establish, while others can continue to make an impact for many years and the impact could extend far beyond the physical disturbance. The spatial extent of waste disposal, telecommunication cables, the hydrocarbon industry and marine research activities is relatively small. The extent of bottom trawling is very significant and, even on the lowest possible estimates, is an order of magnitude greater than the total extent of all the other activities. Conclusions/Significance To meet future ecosystem-based management and governance objectives for the deep sea significant improvements are required in data collection and availability as well as a greater awareness of the relative impact of each human activity

  6. 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.

  7. A biogeochemical study of the coccolithophore, Emiliania huxleyi, in the North Atlantic

    SciTech Connect

    Holligan, P.M.; Fernandez, E.; Aiken, J.; Burkill, P.H. ); Balch, W.M. ); Boyd, P. ); Finch, M. ); Groom, S.B. ); Malin, G. ); Muller, K. )

    1993-12-01

    Coccolithophores are a diverse group of marine phytoplankton that produce external plates, or coccoliths, of calcium carbonate. They are widely distributed in all oceans except polar waters, and are the major and often dominant component of calcite of marine sediments. Their ecology and physiology are poorly known. This paper reports on the first of two cruises to investigate the productivity and biogeochemical significance of Emiliania huxleyi in the North Atlantic. This focused on optics and air-sea gas exchange and provides the general context for more detailed analyses of the observations on the CO2 system in surface waters and on the production of organic matter and calcium carbonate by coccolithophores. 74 refs., 13 figs., 1 tab.

  8. Characterization of marine mammals and turtles in the mid- and north-Atlantic areas of the US Outer Continental Shelf: executive summary for 1979. Final report 1979-81

    SciTech Connect

    Not Available

    1981-04-01

    The program's objectives are as follows: (1) to determine which species of marine mammals and marine turtles inhabit and/or migrate through the study area; (2) to identify, delineate and describe areas of importance (feeding, breeding, calving, etc.) to marine mammals and marine turtles in the study area; (3) to determine the temporal and spatial distribution of marine mammals and marine turtles in the study area; (4) to estimate the size of and extent of marine mammal and marine turtle populations in the study area; and (5) to emphasize the above item 1-4 for those species classified as threatened or endangered by the Department of Interior and Department of Commerce.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Sun, J.

    2010-12-01

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

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

    PubMed

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

    2006-10-01

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

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

    PubMed

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

    2006-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  14. 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

  15. Biogeochemical cycling of cadmium isotopes along a high-resolution section through the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Conway, Tim M.; John, Seth G.

    2015-01-01

    Cadmium (Cd) is a bioactive trace element in the oceans, with a nutrient-like distribution that closely matches dissolved phosphate. Seawater-dissolved stable Cd isotope ratios (δ114Cd) are a relatively new parameter, which show much promise for furthering our understanding of the biogeochemical cycling of Cd in the oceans. Here we present a high-resolution paired section of dissolved Cd concentrations and dissolved δ114Cd from 21 open-ocean stations along the US GEOTRACES GA03 transect through the North Atlantic Ocean. Dissolved Cd concentrations along the section are strongly influenced by water-mass distribution and the cycling of Cd. The highest dissolved Cd concentrations (400-540 pmol kg-1) are associated with Antarctic-sourced water masses, whilst biological uptake in the surface ocean results in a strong vertical gradient in dissolved Cd towards the surface, reaching as low as 0.03 pmol kg-1 in western surface waters. Dissolved δ114Cd is also characterized by a vertical gradient from ∼+0.2‰ in the deep ocean to +2‰ to +5‰ in the Cd-depleted surface ocean (relative to NIST SRM 3108). This variability in δ114Cd can be ascribed to mixing of Antarctic and North Atlantic water masses, together with fractionation due to in situ biological uptake of light Cd in the very surface ocean. Subtle deviations from this overall pattern of dissolved Cd concentration and dissolved δ114Cd are observed within low-oxygen waters off North Africa, where a dissolved Cd deficit relative to phosphate is associated with higher dissolved δ114Cd values. Together with elevated particulate Cd and Ba, this suggests that Cd sulfide precipitation is occurring within the water column of the North Atlantic, constituting a potentially important sink for isotopically light Cd. Additionally, the first measurements of dissolved δ114Cd within a hydrothermal plume at the Mid-Atlantic Ridge show that Cd is scavenged from the dissolved phase, leaving the remnant dissolved Cd

  16. Parasites as biological tags in marine fisheries research: European Atlantic waters.

    PubMed

    Mackenzie, K; Hemmingsen, W

    2015-01-01

    Studies of the use of parasites as biological tags for stock identification and to follow migrations of marine fish, mammals and invertebrates in European Atlantic waters are critically reviewed and evaluated. The region covered includes the North, Baltic, Barents and White Seas plus Icelandic waters, but excludes the Mediterranean and Black Seas. Each fish species or ecological group of species is treated separately. More parasite tag studies have been carried out on Atlantic herring Clupea harengus than on any other species, while cod Gadus morhua have also been the subject of many studies. Other species that have been the subjects of more than one study are: blue whiting Micromesistius poutassou, whiting Merlangius merlangus, haddock Melanogrammus aeglefinus, Norway pout Trisopterus esmarkii, horse mackerel Trachurus trachurus and mackerel Scomber scombrus. Other species are dealt with under the general headings redfishes, flatfish, tunas, anadromous fish, elasmobranchs, marine mammals and invertebrates. A final section highlights how parasites can be, and have been, misused as biological tags, and how this can be avoided. It also reviews recent developments in methodology and parasite genetics, considers the potential effects of climate change on the distributions of both hosts and parasites, and suggests host-parasite systems that should reward further research.

  17. Mercury in the North Atlantic Ocean: The U.S. GEOTRACES zonal and meridional sections

    NASA Astrophysics Data System (ADS)

    Bowman, Katlin L.; Hammerschmidt, Chad R.; Lamborg, Carl H.; Swarr, Gretchen

    2015-06-01

    Mercury (Hg) in the ocean undergoes many chemical transformations, including in situ production of monomethylmercury (MMHg), the form that biomagnifies in marine food webs. Because the ocean is a primary and dynamic reservoir of Hg cycling at earth's surface and the principal source of human MMHg exposures through seafood, it is important to understand the distribution of Hg and its chemical species in marine environments. We examined total Hg, elemental Hg (Hg0), MMHg, and dimethylmercury (DMHg) with fully resolved high-resolution profiles during the U.S. GEOTRACES zonal and meridional sections of the North Atlantic Ocean (GEOTRACES GA03). Total Hg in filtered water had both scavenged- and nutrient-type vertical distributions, whereas concentrations of DMHg, Hg0, and filtered MMHg were increased in the oxygen deficient zone of the permanent thermocline across the basin, relative to water above and often below. Total Hg and MMHg on suspended particles accounted for less than 10% of total concentrations. The TAG hydrothermal vent on the Mid-Atlantic Ridge (MAR) was a source of total Hg and MMHg to nearby waters with apparent scavenging and Hg transformation occurring in the buoyant plume. Uniquely, we observed significant horizontal segregation of filtered total Hg and MMHg, DMHg, and Hg0 in North Atlantic Deep Water (NADW) between younger water on the western and older water on the eastern side of the MAR. Relative to eastern NADW, Hg concentrations in western NADW were greater, on average, by 1.14× for filtered total Hg, 1.6× for Hg0, 2.5× for filtered MMHg, and 2.6× for DMHg. Total Hg enrichment in deep water of the western basin may have resulted from downwelling of anthropogenic Hg during NADW formation. Enrichment of MMHg, DMHg, and Hg0 in western basin NADW may be explained by either greater Hg substrate availability or greater methylation and reduction potentials in younger deep waters.

  18. Modeling Mesoscale Eddies in the North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Chao, Yi

    1999-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Haekkinen, Sirpa

    2001-01-01

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

  20. The JGOFS North Atlantic Bloom Experiment: An overview

    NASA Technical Reports Server (NTRS)

    Ducklow, Hugh W.

    1992-01-01

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

  1. Isohaline Salinity Budget of the North Atlantic Salinity Maximum

    NASA Astrophysics Data System (ADS)

    Bryan, F.; Bachman, S.

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Dacre, H.; Gray, S.

    2009-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Dacre, H.; Gray, S.

    2009-04-01

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

  4. Coupling Between Deglacial Shifts in the Position of the North Atlantic Arctic Front and Precipitation in Western Europe

    NASA Astrophysics Data System (ADS)

    Boessenkool, K. P.; Brinkhuis, H.; Visscher, H.

    2001-12-01

    As a response to a northern position of the Arctic Front, the present-day climate of western Europe is strongly moderated by the presence of the Gulf Stream and its extensions. The ocean currents transport warm and saline water of equatorial-Atlantic origin to the northeastern Atlantic seaboard. Prevailing westerly winds carry the warm and moist maritime air from the North Atlantic to the down-wind regions in Europe. Deglacial changes in North Atlantic sea-surface temperature (SST) associated with southward shifts in the position of the Arctic Front (up to ~30\\deg. mainly along the Northeast Atlantic seaboard) have affected the temperature, wind, and precipitation regimes in the North Atlantic borderlands. Effects are long since known to be most prominent in western Europe, and throughout this area considerable advances have been made to specify a variety of proxy records of fluctuations in terrestrial surface temperature. In marked contrast, patterns of deglacial fluctuations in precipitation in western Europe are still poorly investigated, despite their intimate relation to temperature and wind regime. Deglacial precipitation rates are known to be strongly influenced by changes in the North Atlantic SST. Low SSTs and sea-ice cool the maritime air masses, reducing their moisture-bearing capacity. Distinctive episodes of lowered SST, such as the Younger Dryas (YD) stadial, may have caused considerable aridification in large parts of western Europe. Simulation studies with atmospheric general circulation models (AGCMs; Renssen et al., 1996) demonstrate strong surface westerlies and connected cyclonic depressions during YD winters in the North Atlantic region. In order to corroborate the concept of an intensified westerly cyclonic activity during the YD and a concomitant increase in wintertime precipitation in southwestern Europe, we studied a succession of deglacial palynological assemblages of a marine sediment core (SO75-6KL) from the western Iberian margin

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

    PubMed

    Sutton, Rowan T; Hodson, Daniel L R

    2005-07-01

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

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

    PubMed

    Sutton, Rowan T; Hodson, Daniel L R

    2005-07-01

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

  7. The age and chronostratigraphical significance of North Atlantic Ash zone II

    NASA Astrophysics Data System (ADS)

    Austin, William E. N.; Wilson, Lindsay J.; Hunt, John B.

    2004-02-01

    Rhyolitic tephra with the geochemical characteristics of North Atlantic Ash Zone (NAAZ) II are described from the giant piston core MD95-2006 from the northeast Atlantic Ocean. Shard size distribution indicates that the tephra represent a wind-sorted, primary air-fall deposit, but with a mode close to 200 m they are too coarse to be air-fall deposits at the core site, which lies ca. 1000 km from the possible tephra source. Randomly sampled shards reveal a single geochemical population belonging to the Icelandic transitional alkali magma series, suggesting that they are unlikely to represent ice rafted debris derived from Icelandic icebergs. The tephra probably represent air-fall deposits, transported to the core site by sea ice within the northeast Atlantic gyre. The NAAZ II peak coincides with the rapid climate transition (cooling) at the end of interstadial 15, which can be assigned an age of 53 260+/-2660 yr BP from direct correlation with the Greenland ice-core (GISP2) record. A comparison of the MD95-2006 Neogloboquadrina pachyderma (sinistral) relative abundance and GISP2 18O records, relative to the NAAZ II isochron, suggests that this climatic event was synchronous across the North Atlantic. By direct correlation of interstadial maxima between the two records, the GISP2 time-scale is transferred to MD95-2006. Comparison of corrected and calibrated radiocarbon ages derived from monospecific foraminifers with the GISP2 ages at the same stratigraphical horizon suggest major age differences. These probably result from large variations in atmospheric 14C concentration and highlight the significant uncertainties associated with radiocarbon calibration during marine isotope stage 3. Copyright

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

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

  11. 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.

  12. Proxy Applications of Pa/Th Investigated with Scavenging Chemistry in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Hayes, C. T.; Fleisher, M. Q.; Anderson, R. F.; Lam, P. J.; Ohnemus, D.; Huang, K. F.; Robinson, L. F.; Lu, Y.; Cheng, H.; Edwards, R. L.; Moran, S. B.

    2014-12-01

    The natural radionuclides 231Pa and 230Th have potential value as proxies of past biological productivity in the marine sediment record. In addition to its use as a circulation proxy, the particulate Pa/Th ratio has been suggested to monitor total particle flux and/or diatom productivity via processes related to the scavenging, or the adsorptive removal of these elements onto particles. We investigate the nature of scavenging using trans-Atlantic measurements from GEOTRACES of dissolved (<0.45 μm) and particulate (0.8-51 μm) 231Pa and 230Th, together with major particle composition. We find widespread impact of intense scavenging by authigenic Fe/Mn oxides, in the form of hydrothermal particles emanating from the Mid-Atlantic ridge and particles resuspended from reducing conditions near the seafloor off the coast of West Africa. Biogenic opal was not a significant scavenging phase for either element, essentially because of its low abundance at the studied sites. In the context of the paleo-record, the particulate Pa/Th ratio responds most significantly to scavenging intensity, caused by either biotic or abiotic processes. In the modern setting at least, the influence of North Atlantic Deep Water circulation on Pa/Th is apparently outweighed. The Pa/Th proxy, therefore, is best used in conjunction with other information to support the cause for past changes in scavenging intensity.

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

    USGS Publications Warehouse

    PRISM Project Members

    1996-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Kozar, Michael; Misra, Vasubandhu

    2015-04-01

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

  15. 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.

  16. 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.

  17. 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.

  18. Solar forcing synchronizes decadal North Atlantic climate variability.

    PubMed

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

    2015-01-01

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

  19. Early Oligocene initiation of North Atlantic Deep Water formation

    NASA Astrophysics Data System (ADS)

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

    2001-04-01

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

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

    PubMed

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

    2001-04-19

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

  1. North Atlantic Oscillation records in Siberian tree rings

    NASA Astrophysics Data System (ADS)

    Sidorova, Olga; Saurer, Matthias; Siegwolf, Rolf

    2010-05-01

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

  2. 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.

  3. 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

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

    PubMed

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

    2016-05-01

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

  5. 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.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    Glueck, Mary F.; Stockton, Charles W.

    2001-10-01

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

  8. 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.

  9. Marine debris ingestion by albatrosses in the southwest Atlantic Ocean.

    PubMed

    Jiménez, Sebastián; Domingo, Andrés; Brazeiro, Alejandro; Defeo, Omar; Phillips, Richard A

    2015-07-15

    Plastics and other marine debris affect wildlife through entanglement and by ingestion. We assessed the ingestion of marine debris by seven albatross species in the southwest Atlantic by analyzing stomach contents of birds killed in fisheries. Of the 128 specimens examined, including four Diomedea species (n=78) and three Thalassarche species (n=50), 21 (16.4%) contained 1-4 debris items, mainly in the ventriculus. The most common type was plastic fragments. Debris was most frequent in Diomedea species (25.6%) and, particularly, Diomedea sanfordi (38.9%) and very rare in Thalassarche species (2.0%), presumably reflecting differences in foraging behavior or distribution. Frequency of occurrence was significantly higher in male than female Diomedea albatrosses (39.3% vs. 18.0%). Although levels of accumulated debris were relatively low overall, and unlikely to result in gut blockage, associated toxins might nevertheless represent a health risk for Diomedea albatrosses, compounding the negative impact of other human activities on these threatened species. PMID:25986654

  10. Marine debris ingestion by albatrosses in the southwest Atlantic Ocean.

    PubMed

    Jiménez, Sebastián; Domingo, Andrés; Brazeiro, Alejandro; Defeo, Omar; Phillips, Richard A

    2015-07-15

    Plastics and other marine debris affect wildlife through entanglement and by ingestion. We assessed the ingestion of marine debris by seven albatross species in the southwest Atlantic by analyzing stomach contents of birds killed in fisheries. Of the 128 specimens examined, including four Diomedea species (n=78) and three Thalassarche species (n=50), 21 (16.4%) contained 1-4 debris items, mainly in the ventriculus. The most common type was plastic fragments. Debris was most frequent in Diomedea species (25.6%) and, particularly, Diomedea sanfordi (38.9%) and very rare in Thalassarche species (2.0%), presumably reflecting differences in foraging behavior or distribution. Frequency of occurrence was significantly higher in male than female Diomedea albatrosses (39.3% vs. 18.0%). Although levels of accumulated debris were relatively low overall, and unlikely to result in gut blockage, associated toxins might nevertheless represent a health risk for Diomedea albatrosses, compounding the negative impact of other human activities on these threatened species.

  11. A statistical analysis of North East Atlantic (submicron) aerosol size distributions

    NASA Astrophysics Data System (ADS)

    Dall'Osto, M.; Monahan, C.; Greaney, R.; Beddows, D. C. S.; Harrison, R. M.; Ceburnis, D.; O'Dowd, C. D.

    2011-12-01

    The Global Atmospheric Watch research station at Mace Head (Ireland) offers the possibility to sample some of the cleanest air masses being imported into Europe as well as some of the most polluted being exported out of Europe. We present a statistical cluster analysis of the physical characteristics of aerosol size distributions in air ranging from the cleanest to the most polluted for the year 2008. Data coverage achieved was 75% throughout the year. By applying the Hartigan-Wong k-Means method, 12 clusters were identified as systematically occurring. These 12 clusters could be further combined into 4 categories with similar characteristics, namely: coastal nucleation category (occurring 21.3 % of the time), open ocean nucleation category (occurring 32.6% of the time), background clean marine category (occurring 26.1% of the time) and anthropogenic category (occurring 20% of the time) aerosol size distributions. The coastal nucleation category is characterised by a clear and dominant nucleation mode at sizes less than 10 nm while the open ocean nucleation category is characterised by a dominant Aitken mode between 15 nm and 50 nm. The background clean marine aerosol exhibited a clear bimodality in the sub-micron size distribution, with although it should be noted that either the Aitken mode or the accumulation mode may dominate the number concentration. However, peculiar background clean marine size distributions with coarser accumulation modes are also observed during winter months. By contrast, the continentally-influenced size distributions are generally more monomodal (accumulation), albeit with traces of bimodality. The open ocean category occurs more often during May, June and July, corresponding with the North East (NE) Atlantic high biological period. Combined with the relatively high percentage frequency of occurrence (32.6%), this suggests that the marine biota is an important source of new nano aerosol particles in NE Atlantic Air.

  12. 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...

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. Net community production in the North Atlantic Ocean derived from Volunteer Observing Ship data

    NASA Astrophysics Data System (ADS)

    Ostle, Clare; Johnson, Martin; Landschützer, Peter; Schuster, Ute; Hartman, Susan; Hull, Tom; Robinson, Carol

    2015-01-01

    The magnitude of marine plankton net community production (NCP) is indicative of both the biologically driven exchange of carbon dioxide between the atmosphere and the surface ocean and the export of organic carbon from the surface ocean to the ocean interior. In this study the seasonal variability in the NCP of five biogeochemical regions in the North Atlantic was determined from measurements of surface water dissolved oxygen and dissolved inorganic carbon (DIC) sampled from a Volunteer Observing Ship (VOS). The magnitude of NCP derived from dissolved oxygen measurements (NCPO2) was consistent with previous geochemical estimates of NCP in the North Atlantic, with an average annual NCPO2 of 9.5 ± 6.5 mmol O2 m-2 d-1. Annual NCPO2 did not vary significantly over 35° of latitude and was not significantly different from NCP derived from DIC measurements (NCPDIC). The relatively simple method described here is applicable to any VOS route on which surface water dissolved oxygen concentrations can be accurately measured, thus providing estimates of NCP at higher spatial and temporal resolution than currently achieved.

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  19. Biogeographical Patterns of Marine Benthic Invertebrates Along the Atlantic Coast of the Northeastern USA

    EPA Science Inventory

    Aim Examine the biogeography of marine benthic invertebrates of the Atlantic coast of the northeastern USA, compare the results to historical biogeographic studies, define physical-chemical factors affecting species distributions, and provide biogeographic information needed to ...

  20. Glyoxal and Methylglyoxal in Atlantic Seawater and marine Aerosol Particles

    NASA Astrophysics Data System (ADS)

    van Pinxteren, Manuela; Herrmann, Hartmut

    2014-05-01

    )). References: Sinreich et al., Ship-based detection of glyoxal over the remote tropical Pacific Ocean. Atmos. Chem. Phys. 10(23), 11359-11371 (2010). van Pinxteren and Herrmann, Glyoxal and Methylglyoxal in Atlantic Seawater and marine Aerosol Particles: Method development and first application during the Polarstern cruise ANT XXVII/4. Atmos. Chem. Phys. 13, 11791-11802 (2013).

  1. Basin-scale coherence in phenology of shrimps and phytoplankton in the North Atlantic Ocean.

    PubMed

    Koeller, P; Fuentes-Yaco, C; Platt, T; Sathyendranath, S; Richards, A; Ouellet, P; Orr, D; Skúladóttir, U; Wieland, K; Savard, L; Aschan, M

    2009-05-01

    Climate change could lead to mismatches between the reproductive cycles of marine organisms and their planktonic food. We tested this hypothesis by comparing shrimp (Pandalus borealis) egg hatching times and satellite-derived phytoplankton bloom dynamics throughout the North Atlantic. At large spatial and long temporal (10 years or longer) scales, hatching was correlated with the timing of the spring phytoplankton bloom. Annual egg development and hatching times were determined locally by bottom water temperature. We conclude that different populations of P. borealis have adapted to local temperatures and bloom timing, matching egg hatching to food availability under average conditions. This strategy is vulnerable to interannual oceanographic variability and long-term climatic changes.

  2. Oligocene-Miocene biostratigraphy, magnetostratigraphy, and isotopic stratigraphy of the western North Atlantic

    NASA Astrophysics Data System (ADS)

    Miller, Kenneth G.; Aubry, Marie-Pierre; Khan, M. J.; Melillo, A. J.; Kent, D. V.; Berggren, W. A.

    1985-04-01

    Magnetostratigraphic records from western North Atlantic Deep Sea Drilling Project (DSDP) Sites 563 and 558 are correlated with the geomagnetic polarity time scale (GPTS; Berggren et al., 1984a, 1984b) using marine magnetic anomalies and selected biostratigraphic datum levels. The magnetochronology established is used to make direct magnetobiostratigraphic correlations that agree with previous Oligocene early Miocene studies. However, we show that Zones NN8 partim and NN9 and associated Epoch 11 correlate with Magnetic Anomaly 5 (= Chron C5n). This contrasts with previous indirect correlations of Epoch 11 with Anomaly 5A and requires an upward adjustment of 1.5 2.0 m.y. for middle late Miocene calcareous nannofossil zones. We correlate the middle/late Miocene boundary with Zone NN8 and earliest Chron C5n (10.4 Ma). *Present address: Peshawar University, Peshawar, Pakistan

  3. 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

  4. North Atlantic Deep Water cools the southern hemisphere

    NASA Astrophysics Data System (ADS)

    Crowley, Thomas J.

    1992-08-01

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

  5. 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.

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

    PubMed

    Wirth, Thierry; Bernatchez, Louis

    2003-04-01

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

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

    PubMed

    Wares, J P; Cunningham, C W

    2001-12-01

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

  8. 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.

  9. Monitoring the North Atlantic using ocean colour data

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    PubMed

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

    2008-03-27

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

  11. Temperature signature of high latitude Atlantic boundary currents revealed by marine mammal-borne sensor and Argo data

    NASA Astrophysics Data System (ADS)

    Grist, Jeremy P.; Josey, Simon A.; Boehme, Lars; Meredith, Michael P.; Davidson, Fraser J. M.; Stenson, Garry B.; Hammill, Mike O.

    2011-08-01

    Results from the development and analysis of a novel temperature dataset for the high latitude North-West Atlantic are presented. The new 1° gridded dataset (“ATLAS”) has been produced from about 13,000 Argo and 48,000 marine mammal (hooded seal, harp seal, grey seal and beluga) profiles spanning 2004-8. These data sources are highly complementary as marine mammals greatly enhance shelf region coverage where Argo floats are absent. ATLAS reveals distinctive boundary current related temperature minima in the Labrador Sea (-1.1°C) and at the east Greenland coast (1.8°C), largely absent in the widely-used Levitus'09 and EN3v2a datasets. The ATLAS 0-500 m average temperature is lower than Levitus'09 and EN3v2a by up to 3°C locally. Differences are strongest from 0-300 m and persist at reduced amplitude from 300-500 m. Our results clearly reveal the value of marine mammal-borne sensors for a reliable description of the North-West Atlantic at a time of rapid change.

  12. 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.

  13. 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

  14. An investigation of Ekman upwelling in the North Atlantic

    NASA Technical Reports Server (NTRS)

    Mcclain, Charles R.; Firestone, James

    1993-01-01

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

  15. 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.

  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. The North Atlantic Oscillation system and plant phenology.

    PubMed

    Hubálek, Zdenek

    2016-05-01

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

  18. 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.

  19. 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.

  20. 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.

  1. Diversity and distribution of single-stranded DNA phages in the North Atlantic Ocean.

    PubMed

    Tucker, Kimberly P; Parsons, Rachel; Symonds, Erin M; Breitbart, Mya

    2011-05-01

    Knowledge of marine phages is highly biased toward double-stranded DNA (dsDNA) phages; however, recent metagenomic surveys have also identified single-stranded DNA (ssDNA) phages in the oceans. Here, we describe two complete ssDNA phage genomes that were reconstructed from a viral metagenome from 80 m depth at the Bermuda Atlantic Time-series Study (BATS) site in the northwestern Sargasso Sea and examine their spatial and temporal distributions. Both genomes (SARssφ1 and SARssφ2) exhibited similarity to known phages of the Microviridae family in terms of size, GC content, genome organization and protein sequence. PCR amplification of the replication initiation protein (Rep) gene revealed narrow and distinct depth distributions for the newly described ssDNA phages within the upper 200 m of the water column at the BATS site. Comparison of Rep gene sequences obtained from the BATS site over time revealed changes in the diversity of ssDNA phages over monthly time scales, although some nearly identical sequences were recovered from samples collected 4 years apart. Examination of ssDNA phage diversity along transects through the North Atlantic Ocean revealed a positive correlation between genetic distance and geographic distance between sampling sites. Together, the data suggest fundamental differences between the distribution of these ssDNA phages and the distribution of known marine dsDNA phages, possibly because of differences in host range, host distribution, virion stability, or viral evolution mechanisms and rates. Future work needs to elucidate the host ranges for oceanic ssDNA phages and determine their ecological roles in the marine ecosystem. PMID:21124487

  2. Effects of body condition on buoyancy in endangered North Atlantic right whales.

    PubMed

    Nousek-McGregor, Anna E; Miller, Carolyn A; Moore, Michael J; Nowacek, Douglas P

    2014-01-01

    Buoyancy is an important consideration for diving marine animals, resulting in specific ecologically relevant adaptations. Marine mammals use blubber as an energy reserve, but because this tissue is also positively buoyant, nutritional demands have the potential to cause considerable variation in buoyancy. North Atlantic right whales Eubalaena glacialis are known to be positively buoyant as a result of their blubber, and the thickness of this layer varies considerably, but the effect of this variation on buoyancy has not been explored. This study compared the duration and rate of ascending and descending glides, recorded with an archival tag, with blubber thickness, measured with an ultrasound device, in free-swimming right whales. Ascending whales with thicker blubber had shorter portions of active propulsion and longer passive glides than whales with thinner blubber, suggesting that blubber thickness influences buoyancy because the buoyant force is acting in the same direction as the animal's movement during this phase. Whales with thinner layers also used similar body angles and velocities when traveling to and from depth, while those with thicker layers used shallower ascent angles but achieved higher ascent velocities. Such alterations in body angle may help to reduce the cost of transport when swimming against the force of buoyancy in a state of augmented positive buoyancy, which represents a dynamic response to reduce the energetic consequences of physiological changes. These results have considerable implications for any diving marine animal during periods of nutritional stress, such as during seasonal migrations and annual variations in prey availability.

  3. Regional Model Simulations of Cyclones Over The North Atlantic

    NASA Astrophysics Data System (ADS)

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

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

  4. Link between North Atlantic wave climate and circulation changes

    SciTech Connect

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

    1994-12-31

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

  5. 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.

  6. Variability and Sources of Tropospheric Aerosols Over the North Atlantic in Fall: A Model Analysis in Support of the NASA NAAMES Earth-Venture Suborbital-2 Mission

    NASA Astrophysics Data System (ADS)

    Liu, H.; Moore, R.; Hostetler, C. A.; Ferrare, R. A.; Fairlie, T. D.; Hu, Y.; Chen, G.; Johnson, M. S.; Gantt, B.; Jaegle, L.

    2015-12-01

    The North Atlantic Aerosols and Marine Ecosystems Study (NAAMES) is a five-year Earth-Venture Suborbital-2 Mission to characterize the plankton ecosystems and their influences on remote marine aerosols, boundary layer clouds, and their implications for climate in the North Atlantic, with the first field deployment in November 2015. While marine-sourced aerosols have been shown to make important contributions to surface aerosol loading, cloud condensation nuclei and ice nuclei concentrations over remote marine and coastal regions, it is still a challenge to differentiate the marine biogenic aerosol signal from the strong influence of continental pollution outflow. As a pre-mission analysis, we examine here the spatiotemporal variability and quantify the sources of tropospheric aerosols over the North Atlantic during November 2008 using a state-of-the-art chemical transport model (GEOS-Chem). The model is driven by the Modern-Era Retrospective analysis for Research and Applications (MERRA at 2°×2.5° horizontal resolution) from the NASA Global Modeling Assimilation Office (GMAO). It includes sulfate-nitrate-ammonium aerosol thermodynamics coupled to ozone-NOx-hydrocarbon-aerosol chemistry, mineral dust, sea salt, elemental and organic carbon aerosols, especially a recently implemented parameterization for the marine primary organic aerosol emission. The simulated aerosols over the North Atlantic are evaluated with available satellite (e.g., MODIS) observations of aerosol optical depths (AOD) and surface aerosol measurements. We diagnose transport pathways for continental pollution outflow over the North Atlantic using carbon monoxide, an excellent tracer for anthropogenic pollution transport. Simulations indicate that, along the NAAMES nominal ship and flight tracks (40°W, 40-57°N), episodic pollution transport associated with frontal passages occurs at both the surface and free troposphere, with periods of relatively unperturbed marine air as indicated by

  7. Opening of the Arctic-North Atlantic Gateway

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

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

  8. Influence of environmental changes in the north-western Atlantic Ocean on a parasite, Echinorhynchus gadi (Acanthocephala) of Atlantic cod ( Gadus morhua) occurring off coastal Labrador, Canada.

    PubMed

    Khan, R A

    2008-09-01

    A study was conducted to determine the influence of environmental change on an endoparasite, Echinorhynchus gadi (Acanthocephala) of Atlantic cod (Gadus morhua) over a 30-year period off the coast of Labrador in the north-western Atlantic, North Atlantic Fisheries Organization subareas 2J-3K. Cod, once an abundant fish species that had been commercially exploited for many decades, declined precipitously during the mid-1980s onwards. This decline was attributed to climatic changes that affected the entire food chain from zooplankton to fish, sea birds and marine mammals. A monitoring programme was introduced, sampling cod by otter trawling using research vessels. The fish, after capture, were frozen at - 20 degrees C, subsequently thawed and the digestive tract removed and examined for the parasite in 2006. Data from samples taken in 1976, 1980-81, 1986, 1990, 2000 and 2003 were compared statistically with those collected in 2006. The results indicate a decline in the prevalence and mean abundance of E. gadi in 1986 with a minimum in 2000 but increasing gradually in 2003 and 2006. These changes were coincident initially with a decline of oceanic temperature and the entire food web, including capelin (Mallotus villosus), a preferred prey of cod and primary source of E. gadi. The increase in prevalence and mean abundance of the parasite in 2006 were associated with an increase of oceanic temperature and the return of small schools of capelin to offshore areas. Cod older than 4 years harboured a greater abundance of E. gadi than younger fish, while no difference was observed between the sexes. The results suggest that the abundance of E. gadi can be useful as a bioindicator of environmental changes in the north-western Atlantic.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Park, Taewook; Park, Wonsun; Latif, Mojib

    2016-04-01

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

  11. Palynological evidence for a southward shift of the North Atlantic Current at ~2.6 Ma during the intensification of late Cenozoic Northern Hemisphere glaciation

    NASA Astrophysics Data System (ADS)

    Hennissen, Jan A. I.; Head, Martin J.; De Schepper, Stijn; Groeneveld, Jeroen

    2014-06-01

    The position of the North Atlantic Current (NAC) during the intensification of Northern Hemisphere glaciation (iNHG) has been evaluated using dinoflagellate cyst assemblages and foraminiferal geochemistry from a ~260 kyr interval straddling the base of the Quaternary System from two sites: eastern North Atlantic Deep Sea Drilling Project Site 610 in the path of the present NAC and central North Atlantic Integrated Ocean Drilling Program Site U1313 in the subtropical gyre. Stable isotope and foraminiferal Mg/Ca analyses confirm cooling near the marine isotope stage (MIS) G7-G6 transition (2.74 Ma). However, a continued dominance of the dinoflagellate cyst Operculodinium centrocarpum sensu Wall and Dale (1966) indicates an active NAC in the eastern North Atlantic for a further 140 kyr. At MIS 104 (~2.60 Ma), a profound dinoflagellate cyst assemblage turnover indicates NAC shutdown in the eastern North Atlantic, implying elevated atmospheric pressure over the Arctic and a resulting shift in the westerlies that would have driven the NAC. These findings challenge recent suggestions that there was no significant southward shift of the NAC or the Arctic Front during iNHG, and reveal a fundamental climatic reorganization near the base of the Quaternary.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

    Saito, M. A.; Noble, A.

    2012-12-01

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

  14. North East Atlantic Tsunamis Related with Gloria Fault

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  15. Coralline algal Barium as indicator for 20th century northwestern North Atlantic surface ocean freshwater variability

    PubMed Central

    Hetzinger, S.; Halfar, J.; Zack, T.; Mecking, J. V.; Kunz, B. E.; Jacob, D. E.; Adey, W. H.

    2013-01-01

    During the past decades climate and freshwater dynamics in the northwestern North Atlantic have undergone major changes. Large-scale freshening episodes, related to polar freshwater pulses, have had a strong influence on ocean variability in this climatically important region. However, little is known about variability before 1950, mainly due to the lack of long-term high-resolution marine proxy archives. Here we present the first multidecadal-length records of annually resolved Ba/Ca variations from Northwest Atlantic coralline algae. We observe positive relationships between algal Ba/Ca ratios from two Newfoundland sites and salinity observations back to 1950. Both records capture episodical multi-year freshening events during the 20th century. Variability in algal Ba/Ca is sensitive to freshwater-induced changes in upper ocean stratification, which affect the transport of cold, Ba-enriched deep waters onto the shelf (highly stratified equals less Ba/Ca). Algal Ba/Ca ratios therefore may serve as a new resource for reconstructing past surface ocean freshwater changes. PMID:23636135

  16. Subsurface warming in the subpolar North Atlantic during rapid climate events in the Early and Mid-Pleistocene

    NASA Astrophysics Data System (ADS)

    Hernández-Almeida, Iván; Sierro, Francisco; Cacho, Isabel; Abel Flores, José

    2014-05-01

    A new high-resolution reconstruction of the temperature and salinity of the subsurface waters using paired Mg/Ca-δ18O measurements on the planktonic foraminifera Neogloboquadrina pachyderma sinistrorsa (sin.) was conducted on a deep-sea sediment core in the subpolar North Atlantic (Site U1314). This study aims to reconstruct millennial-scale subsurface hydrography variations during the Early and Mid-Pleistocene (MIS 31-19). These rapid climate events are characterized by abrupt shifts between warm/cold conditions, and ice-sheet oscillations, as evidenced by major ice rafting events recorded in the North Atlantic sediments (Hernández-Almeida et al., 2012), similar to those found during the Last Glacial period (Marcott et al, 2011). The Mg/Ca derived paleotemperature and salinity oscillations prior and during IRD discharges at Site U1314 are related to changes in intermediate circulation. The increases in Mg/Ca paleotemperatures and salinities during the IRD event are preceded by short episodes of cooling and freshening of subsurface waters. The response of the AMOC to this perturbation is an increased of warm and salty water coming from the south, transported to high latitudes in the North Atlantic beneath the thermocline. This process is accompanied by a southward shift in the convection cell from the Nordic Seas to the subpolar North Atlantic and better ventilation of the North Atlantic at mid-depths. Poleward transport of warm and salty subsurface subtropical waters causes intense basal melting and thinning of marine ice-shelves, that culminates in large-scale instability of the ice sheets, retreat of the grounding line and iceberg discharge. The mechanism proposed involves the coupling of the AMOC with ice-sheet dynamics, and would explain the presence of these fluctuations before the establishment of high-amplitude 100-kyr glacial cycles. Hernández-Almeida, I., Sierro, F.J., Cacho, I., Flores, J.A., 2012. Impact of suborbital climate changes in the North

  17. Medaka (Oryzias latipes) as a sentinel species for aquatic animals: Medaka cells exhibit a similar genotoxic response as North Atlantic right whale cells★

    PubMed Central

    Wise, John Pierce; Wise, Sandra S.; Goodale, Britton C.; Shaffiey, Fariba; Kraus, Scott; Walter, Ronald B.

    2015-01-01

    Hexavalent chromium (Cr(VI)) is emerging as a major concern for aquatic environments, particularly marine environments. Medaka (Oryzias latipes) has been used as a model species for human and aquatic health, including the marine environment, though few studies have directly compared toxicological responses in medaka to humans or other aquatic species. We used a medaka fin cell line to compare the genotoxic response of medaka to Cr(VI) to the response observed in North Atlantic right whale cells to see if responses in medaka were similar to those of other aquatic species, particularly aquatic mammals. We used the production of chromosomal aberrations as a measure of genotoxicity. We found that in medaka cells, concentrations of 1, 5 and 10 μM sodium chromate damaged 17, 32 and 43% of metaphases, respectively and these same concentrations 1, 2.5, 5 and 10 μM sodium chromate damaged 14, 24 and 49% of metaphases, respectively, in North Atlantic right whale lung cells and 11, 32 and 41% of metaphases, respectively, in North Atlantic right whale testes cells. These data show that genotoxic responses in medaka are comparable to those seen in North Atlantic right whale cells, consistent with the hypothesis that medaka are a useful model for other aquatic species. PMID:18930840

  18. Parasites as biological tags of marine, freshwater and anadromous fishes in North America from the Tropics to the Arctic.

    PubMed

    Marcogliese, David J; Jacobson, Kym C

    2015-01-01

    Parasites have been considered as natural biological tags of marine fish populations in North America for almost 75 years. In the Northwest Atlantic, the most studied species include Atlantic cod (Gadus morhua), Atlantic herring (Clupea harengus) and the redfishes (Sebastes spp.). In the North Pacific, research has centred primarily on salmonids (Oncorhynchus spp.). However, parasites have been applied as tags for numerous other pelagic and demersal species on both the Atlantic and Pacific coasts. Relatively few studies have been undertaken in the Arctic, and these were designed to discriminate anadromous and resident salmonids (Salvelinus spp.). Although rarely applied in fresh waters, parasites have been used to delineate certain fish stocks within the Great Lakes-St Lawrence River basin. Anisakid nematodes and the copepod Sphyrion lumpi frequently prove useful indicators in the Northwest Atlantic, while myxozoan parasites prove very effective on the coast and open seas of the Pacific Ocean. Relative differences in the ability of parasites to discriminate between fish stocks on the Pacific and Atlantic coasts may be due to oceanographic and bathymetric differences between regions. Molecular techniques used to differentiate populations and species of parasites show promise in future applications in the field.

  19. 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.

  20. 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.

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

    NASA Technical Reports Server (NTRS)

    Ruddiman, W. F.

    1984-01-01

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

  2. 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.

  3. 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.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Wood, Kimberly M.; Ritchie, Elizabeth A.

    2015-11-01

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

  7. Correlating Cordilleran Ice Sheet Collapse with North Atlantic Heinrich Events using Global Radiocarbon Plateaus.

    NASA Astrophysics Data System (ADS)

    Hendy, I. L.; Cosma, T.

    2006-12-01

    The small, ephemeral Cordilleran Ice Sheet, present in Alaska, British Columbia and northern Washington during the last glacial cycle is believed to have behaved differently than the larger Laurentice Ice Sheet to climate forcing. High quality chronology is required to understand the relationship between this ice sheet and global climate change. Presently MD02-2496 (48°58.47N: 127°02.14W; 1190m water depth) is the highest resolution paleoclimate record available for the last 50 Ka in the Pacific northwest and contains intervals of glacial-marine sedimentation. High resolution dating based on 36 radiocarbon dates provide a chronology that includes radiocarbon age plateaus, while planktonic foraminiferal stable isotopes offer a continuous record of climate change. Glacial-marine sediments collected from this site on the continental slope west of Vancouver Island, British Columbia, document three intervals of iceberg discharge during the last ~50 Ka. Gradually increasing quantities of ice rafted detritus (grains >250μm, g-1; IRD) followed by abrupt cessation within ~500 years is strongly suggestive of catastrophic iceberg discharge. The penultimate event is correlated to marine invasion of the Juan de Fuca Strait, and Puget Sound, while the final IRD event with that of Georgia Strait. We posit that these previously unknown IRD events represent repeated rapid iceberg discharge related to Cordilleran Ice Sheet collapse. The events occur near the end of radiocarbon plateaus at 13.35 ±90 and 14.05 ±70 14C Kyr BP (not reservoir corrected). If these plateaus correlate with the 12.2 and 13.3 14C Kyr BP plateaus recorded in Carriaco Basin and elsewhere, local reservoir ages can be calculated and vary between 1,150 and 1,550 years similar to those derived locally from glacial wood-shell pairs. Furthermore, if the plateaus result from reduced North Atlantic Deep Water export and consequently Heinrich Events, the Cordilleran IRD events are related to North Atlantic iceberg

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

    PubMed Central

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

    2002-01-01

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

  9. Ecosystem Models as Support to Eutrophication Management in the North Atlantic Ocean (EMoSEM)

    NASA Astrophysics Data System (ADS)

    Lacroix, Geneviève; Billen, Gilles; Desmit, Xavier; Garnier, Josette; Gypens, Nathalie; Lancelot, Christiane; Lenhart, Hermann; Los, Hans; Mateus, Marcos; Ménesguen, Alain; Neves, Ramiro; Troost, Tineke; van der Molen, Johan

    2013-04-01

    One of the leading challenges in marine science and governance is to improve scientific guidance of management measures to mitigate eutrophication nuisances in the EU seas. Existing approaches do not integrate the eutrophication process in space (continuum river-ocean) and in time (past, present and future status). A strong need remains for (i) knowledge/identification of all the processes that control eutrophication and its consequences, (ii) consistent and harmonized reference levels assigned to each eutrophication-related indicator, (iii) identification of the main rivers directly or indirectly responsible for eutrophication nuisances in specific areas, (iv) an integrated transboundary approach and (v) realistic and scientific-based nutrient reduction scenarios. The SEAS-ERA project EMoSEM aims to develop and combine the state-of-the-art modelling tools describing the river-ocean continuum in the North-East Atlantic (NEA) continental seas. This will allow to link the eutrophication nuisances in specific marine regions to anthropogenic inputs, trace back their sources up to the watersheds, then test nutrient reduction options that might be implemented in these watersheds, and propose consistent indicators and reference levels to assess the Good Environmental Status (GES). At the end, EMoSEM will deliver coupled river-coastal-sea mathematical models and will provide guidance to end-users (policy- and decision makers) for assessing and combating eutrophication problems in the NEA continental waters.

  10. Stratigraphy of Atlantic coastal margin of United States north of Cape Hatteras; brief survey

    USGS Publications Warehouse

    Perry, W.J.; Minard, J.P.; Weed, E.G.A.; Robbins, E.I.; Rhodehamel, E.C.

    1975-01-01

    A synthesis of studies of sea-floor outcrops of the sedimentary wedge beneath the northeastern United States continental shelf and slope and a reassessment of coastal plain Mesozoic stratigraphy, particularly of the coastal margin, provide insight for estimating the oil and gas potential and provide geologic control for marine seismic investigations of the Atlantic continental margin. The oldest strata known to crop out on the continental slope are late Campanian in age. The Cretaceous-Tertiary contact along the slope ranges from a water depth of 0.6 to 1.5 km south of Georges Bank to 1.8 km in Hudson Canyon. Few samples are available from Tertiary and Late Cretaceous outcrops along the slope. Sediments of the Potomac Group, chiefly of Early Cretaceous age, constitute a major deltaic sequence in the emerged coastal plain. This thick sequence lies under coastal Virginia, Maryland, Delaware, southeastern New Jersey, and the adjacent continental shelf. Marine sands associated with this deltaic sequence may be present seaward under the outer continental shelf. South of the Norfolk arch, under coastal North Carolina, carbonate rocks interfinger with Lower Cretaceous clastic strata. From all available data, Mesozoic correlations in coastal wells between coastal Virginia and Long Island have been revised. The Upper-Lower Cretaceous boundary is placed at the transition between Albian and Cenomanian floras. Potential hydrocarbon source beds are present along the coast in the subsurface sediments of Cretaceous age. Potential reservoir sandstones are abundant in this sequence.

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

    PubMed

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

    2008-05-01

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

  12. Efficient Transport of Nitric Acid in Urban Plumes Observed Over the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Neuman, J.; Parrish, D.; Trainer, M.; Brown, S.; Fehsenfeld, F.; Flocke, F.; Holloway, J.; Nowak, J.; Ryerson, T.; Stark, H.; Swanson, A.

    2005-12-01

    The processing of anthropogenic NOx emissions from urban and industrial sources was studied using data collected from an instrumented aircraft flying over the east coast of the United States and over the North Atlantic Ocean. Pollutants were sampled from the National Oceanic and Atmospheric Administration WP-3 aircraft during the International Consortium for Atmospheric Research on Transport and Transformation study in July and August, 2004. Fast response measurements of reactive nitrogen compounds and carbon monoxide (CO) were obtained in crosswind transects of urban plumes in the New York City and Boston source regions and up to 1600 km downwind. The magnitude and geographical extent of the effects of NOx and its oxidation products depend on the NOx oxidation rates and pathways and on the atmospheric lifetime and loss mechanisms of the resulting secondary products. In urban plumes that were sampled further than 200 km from New York City and Boston, nitric acid was always the most abundant reactive nitrogen species and usually accounted for over 80% of the sum of NOx and its oxidation products. During this study, frequently plumes were transported above the marine boundary layer at a few hundred meters altitude and were decoupled from the surface, which allowed efficient transport of nitric acid that is not commonly observed at the surface, in the continental boundary layer, or in the free troposphere. In plumes observed over the remote North Atlantic Ocean, nitric acid mixing ratios were high (up to 50 ppbv) and the ratio of CO to reactive nitrogen changed little with plume age, reflecting the small depositional loss of nitric acid. Many of the photochemically aged urban plumes were characterized by the presence of tens of ppbv of nitric acid for several days. As a consequence of the slow removal of nitric acid from these air masses, NOx can be reformed from nitric acid photolysis and OH oxidation. The efficient transport of nitric acid may also allow for

  13. Evolution of North Atlantic Passive Margins Controlled by the Iceland Mantle Plume

    NASA Astrophysics Data System (ADS)

    Parnell-Turner, R. E.; White, N. J.; Henstock, T.; Murton, B. J.; Jones, S. M.

    2015-12-01

    Evolution of North Atlantic passive margins has been profoundly influenced by the Iceland mantle plume over the past 60 Ma. Residual depth anomalies of oceanic lithosphere, long wavelength gravity anomalies and seismic tomographic models show that upwelling mantle material extends from Baffin Bay to Western Norway. At fringing passive margins such as Northwest Scotland, there is evidence for present-day dynamic support of the crust. The Iceland plume is bisected by the Reykjanes Ridge ridge, which acts as a tape-recorder of the temporal variability of the plume. We present regional seismic reflection profiles that traverse the oceanic basin between northwest Europe and Greenland. A diachronous pattern of V-shaped ridges and troughs are imaged beneath marine sediments, revealing a complete record of transient periodicity that can be traced continuously back to ~55 Myrs. This periodicity increases from ~3 to ~8 Ma with clear evidence for minor, but systematic, asymmetric crustal accretion. V-shaped ridges grow with time and reflect small (5-30°C) changes in mantle temperature, consistent with episodic generation of hot solitary waves triggered by growth of thermal boundary layer instabilities within the mantle. Our continuous record of convective activity suggests that the otherwise uniform thermal subsidence of sedimentary basins, which fringe the North Atlantic Ocean, has been punctuated by periods of variable dynamic topography. This record can explain a set of diverse observations from the geologic record. Paleogene unconformities in the Faroe-Shetland Basin, the punctuated deposition of contourite drifts and variations in deep-water current strength can all be explained by transient mantle plume behavior. These signals of convective activity should lead to improved insights into the fluid dynamics of the mantle, and into the evolution of volcanic passive margins.

  14. Spatially explicit estimates of stock size, structure and biomass of North Atlantic albacore Tuna (Thunnus alalunga)

    NASA Astrophysics Data System (ADS)

    Lehodey, P.; Senina, I.; Dragon, A.-C.; Arrizabalaga, H.

    2014-04-01

    The development of the ecosystem approach and models for the management of ocean marine resources requires easy access to standard validated datasets of historical catch data for the main exploited species. They are used to measure the impact of biomass removal by fisheries and to evaluate the models skills, while the use of standard dataset facilitates models inter-comparison. Unlike standard stock assessment models, new state-of-the-art ecosystem models require geo-referenced fishing data with highest possible spatial resolution. This study presents an application to the north Atlantic albacore tuna stock with a careful definition and validation of a spatially explicit fishing dataset prepared from publically available sources (ICCAT) for its use in a spatial ecosystem and population dynamics model (SEAPODYM) to provide the first spatially explicit estimate of albacore density in the North Atlantic by life stage. Density distributions are provided (http://doi.pangaea.de/10.1594/PANGAEA.831499) together with the fishing data used for these estimates http://doi.pangaea.de/10.1594/PANGAEA.830797, http://doi.pangaea.de/10.15 1594/PANGAEA.828168, http://doi.pangaea.de/10.1594/PANGAEA.828170, and http://doi.pangaea.de/10.1594/PANGAEA.828171 (see section Source Data References).

  15. Marine Wildlife Entanglement in North America.

    ERIC Educational Resources Information Center

    O'Hara, Kathryn; And Others

    The public has become increasingly aware that marine wildlife sometimes becomes entangled in fishing gear, such as dolphins in tuna nets. However, little is known about how widespread entanglement is and what its impacts are. If conclusions can be drawn from what few data do exist, the picture is an alarming one. Each year fishing activity causes…

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

    NASA Astrophysics Data System (ADS)

    Oppo, Delia W.; Lehman, Scott J.

    1995-10-01

    We generated ˜200-kyr-long proxy records of surface and deepwater variability from a subpolar North Atlantic core (V29-202), enabling us to assess the linkage between surface and deepwater changes on suborbital timescales. In particular, we used a benthic δ13C record to evaluate the deep water response to Dansgaard-Oeschger temperature oscillations and to Heinrich events, times of massive iceberg delivery to the North Atlantic. We found that the reduction of North Atlantic Deep Water (NADW) production was generally associated with cold or dropping sea surface temperatures (SSTs) as indicated by planktonic foraminiferal assemblages. The NADW contribution to the site did not drop appreciably during Heinrich events H4 through H2, probably because these events followed intervals of prolonged surface cooling already characterized by low rates of NADW production. By contrast NADW reduction appears to have been synchronous with H5. SST rise associated with both Dansgaard-Oeschger oscillations and Heinrich events was usually accompanied by increasing NADW strength. In a few cases the NADW recovery appeared to lag the SST rise; however, the apparent delay is most likely an artefact of the sedimentary record (low concentrations of benthic foraminifera). As a result of low benthic foraminiferal abundances during stage 6, the stage 6 benthic foraminiferal δ13C record is of lower resolution than the younger part of the record. The stage 6 proxy records for surface hydrography nevertheless reveal millennial-scale oscillations similar to those seen in stage 3. The available δ13C data suggest that NADW weakened in association with the cold portions of stage 6 SST oscillations. We also sought to confirm a recent study which concluded that there was little NADW variability during the peak of the last interglaciation, marine oxygen isotope substage 5e (Eemian). Isotope stage 5 was marked by a trend of increasing benthic δ13C in V29-202. Rising δ13C through isotope stage 5 is

  17. Contrails developed under frontal influences of the North Atlantic

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

  18. 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.

  19. 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.

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

    PubMed

    Häkkinen, Sirpa; Rhines, Peter B

    2004-04-23

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

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

    PubMed

    Caswell, H; Fujiwara, M; Brault, S

    1999-03-16

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

  3. 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.

  4. 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.

  5. N2O and CH4 distribution and fluxes in the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Rees, Andy; Brown, Ian; Shutler, Jamie; Ashton, Ian

    2016-04-01

    The world's oceans are a natural source of both N2O and CH4 contributing up to 30% and 10% of the global atmospheric emissions respectively. That said, marine sources are not well constrained owing to a paucity of observations. For both gases there are regional hotspots of production, often associated with upwelling areas and coastal environments, though the distribution of source and sink areas are often spatially and temporarily variable. Here we present data from the greater North Atlantic Ocean to examine factors affecting regional variability in the distribution of both gases and then provide an assessment of seasonal variability for the North East continental shelf region. The flux of gases between the ocean and atmosphere is described by the concentration gradient between the two phases and the gas transfer velocity, the determination of which is directly influenced by wind speed. The measurement of wind speed on ships at sea coincident with analyses of dissolved gases is prone to errors associated with the moving platform and turbulence associated with air masses at the sea surface. To address this problem we provide comparative estimates of the air-sea exchange of both gases determined by ship-based and remotely sensed measurements of wind speed and surface temperature.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

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

    SciTech Connect

    Hurrell, J.W.

    1995-08-01

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

  8. BRITICE-CHRONO and GLANAM: new exciting developments in the study of circum-North Atlantic ice sheets

    NASA Astrophysics Data System (ADS)

    Benetti, Sara; Clark, Chris D.; Petter Serjup, Hans

    2013-04-01

    This talk will present two newly funded projects on the reconstruction of former marine-based ice sheets bordering the North Atlantic Ocean and their effects on the surrounding continental margins. The NERC-funded BRITICE-CHRONO started in October 2012 and its consortium involves scientists from all over the UK with partners in Ireland, Canada and Norway. It aims to carry out a systematic campaign to collect and date material to constrain the timing and rates of change of the collapse of the former British-Irish Ice Sheet. This will be achieved by focussing on eight transects running from the shelf edge to a short distance onshore and acquiring marine and terrestrial samples for geochronometric dating. The sampling will be accomplished by two research cruises and eight fieldwork campaigns around UK and Ireland. The project will result in the world's best empirical reconstruction of a shrinking ice sheet, for use in improving ice sheet models, and to provide the long term context against which contemporary observations can be assessed. The FP7-funded Marie Curie Initial Training Networks GLANAM (Glaciated North Atlantic Margins) will start in April 2013 and aims at improving the career prospects and development of young researchers in both the public and private sector within the field of earth science, focusing specifically on North Atlantic glaciated margins. The training network comprises ten partner institutions, both academic and industrial, from Norway, UK and Denmark and will train eleven PhD and four postdoctoral researchers. The young scientists will perform multi-disciplinary research and receive training through three interconnected workpackages that collectively address knowledge gaps related to the glacial sedimentary depocentres on the North Atlantic margins. Filling these gaps will not only result in major new insights regarding glacial processes on continental margins in general, but critically will have particular impact on the exploitation of

  9. 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.

  10. Publications of the Branch of Atlantic Marine Geology for Calendar Year 1992

    USGS Publications Warehouse

    Mons-Wengler, Margaret C.; Oldale, Robert N.

    1993-01-01

    This U.S. Geological Survey Open-File Report contains a listing of publications authored or co-authored by members of the Branch of Atlantic Marine Geology and published in calendar year 1992. The Branch conducts a broad geologic and geophysical research and mapping program, primarily along the U.S. Atlantic Margin, in the Great Lakes, the Gulf of Mexico, the Caribbean and polar regions. A long range objective of this program is to develop a comprehensive understanding of the geology of the continental margin and a predictive capability to guide and assess the consequences of its use. Headquarters of the Branch of Atlantic Marine Geology are located in Woods Hole, MA., and personnel are located in Woods Hole, MA., St Petersburg, FL., Reston, VA., Denver, CO., and San Juan, Puerto Rico. A brochure describing the Branch of Atlantic Marine Geology may be obtained by writing to Chief, Branch of Atlantic Marine Geology, Quissett Campus, Woods Hole, MA 02543. Results of Branch investigations are distributed in a variety of ways, including maps, journal articles, abstracts and U.S.G.S. publications. Copies of U.S.G.S. Open File Reports may be obtained from the author. Book publications can be obtained from U.S. Geological Survey, Books and Reports Sales, Federal Center, Box 25425, Denver, CO 80225. Copies of U.S.G.S. Maps may be obtained from the U.S. Geological Survey, Map Sales, Federal Center, Box 25286, Denver, CO 80225.

  11. Publications of the Branch of Atlantic Marine Geology for Calendar Year 1990

    USGS Publications Warehouse

    Mons-Wengler, Margaret C.; Oldale, Robert N.

    1991-01-01

    This U.S. Geological Survey Open-File Report [extract] contains a listing of publications authored or co-authored by members of the Branch of Atlantic Marine Geology and published in calendar year 1990. The Branch conducts a broad geologic and geophysical research and mapping program, primarily along the U.S. Atlantic Margin, in the Great Lakes, the Gulf of Mexico, the Caribbean and polar regions. A long range objective of this program is to develop a comprehensive understanding of the geology of the continental margin and a predictive capability to guide and assess the consequences of its use. Headquarters of the Branch of Atlantic Marine Geology are located in Woods Hole, MA., and personnel are located in Woods Hole, MA., St Petersburg, FL., Reston, VA., Denver, CO., and San Juan, Puerto Rico. A brochure describing the Branch of Atlantic Marine Geology may be obtained by writing to Chief, Branch of Atlantic Marine Geology, Quissett Campus, Woods Hole, MA 02543. Results of Branch investigations are distributed in a variety of ways, including maps, journal articles, abstracts and U.S.G.S. publications. Copies of U.S.G.S. Open File Reports may be obtained from the author. Book publications can be obtained from U.S. Geological Survey, Books and Reports Sales, Federal Center, Box 25425, Denver, CO 80225. Copies of U.S.G.S. Maps may be obtained from the U.S. Geological Survey, Map Sales, Federal Center, Box 25286, Denver, CO 80225.

  12. Publications of the Branch of Atlantic Marine Geology for Calendar Year 1993

    USGS Publications Warehouse

    Mons-Wengler, Margaret C.; Oldale, Robert N.

    1994-01-01

    This U.S. Geological Survey Open-File Report [extract] contains a listing of publications authored or co-authored by members of the Branch of Atlantic Marine Geology and published in calendar year 1993. The Branch conducts a broad geologic and geophysical research and mapping program, primarily along the U.S. Atlantic Margin, in the Great Lakes, the Gulf of Mexico, the Caribbean and polar regions. A long range objective of this program is to develop a comprehensive understanding of the geology of the continental margin and a predictive capability to guide and assess the consequences of its use. Headquarters of the Branch of Atlantic Marine Geology are located in Woods Hole, MA., and personnel are located in Woods Hole, MA., St Petersburg, FL., Reston, VA., Denver, CO., and San Juan, Puerto Rico. A brochure describing the Branch of Atlantic Marine Geology may be obtained by writing to Chief, Branch of Atlantic Marine Geology, Quissett Campus, Woods Hole, MA 02543. Results of Branch investigations are distributed in a variety of ways, including maps, journal articles, abstracts and U.S.G.S. publications. Copies of U.S.G.S. Open File Reports may be obtained from the author. Book publications can be obtained from U.S. Geological Survey, Books and Reports Sales, Federal Center, Box 25425, Denver, CO 80225. Copies of U.S.G.S. Maps may be obtained from the U.S. Geological Survey, Map Sales, Federal Center, Box 25286, Denver, CO 80225.

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

    PubMed

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

    2012-01-01

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

  14. 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

  15. The isotopic signature and distribution of particulate iron in the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Revels, Brandi N.; Ohnemus, Daniel C.; Lam, Phoebe J.; Conway, Tim M.; John, Seth G.

    2015-06-01

    Iron (Fe) is a key micronutrient for life in the oceans. Particles play an important role in the marine biogeochemical cycling of Fe as a reservoir of marine Fe that may be directly accessible to phytoplankton, and as sources and sinks for seawater dissolved Fe. Here, we report the stable isotopic composition of Fe (δ56Fe) in suspended (0.8-51 μm) particles from the US GEOTRACES GA03 North Atlantic zonal transect, in order to facilitate a better understanding of the marine biogeochemical cycling of Fe. Data are presented both for a total digestion of the particles, and for 'ligand-leachable' phases of Fe using a newly-developed pH 8 oxalate-EDTA leach. For total particle digests, the mean δ56Fe across the whole GA03 section was 0.08±0.09‰ (1 S.D.) which is equivalent to the isotope composition of known lithogenic Fe sources to the ocean. In contrast, ligand-leachable Fe was generally lighter than continental material with a mean δ56Fe of -0.30±0.17‰ (1 S.D.). Our data also provide valuable insight into Fe biogeochemical cycling in several key regions. In the deep ocean, but above the depths where near-sediment nephloid layers are present, ligand-leachable Fe is isotopically lighter in the deep Western Basin compared to the deep Central and Eastern Basins suggesting differences in particle surface chemistry between resuspended seafloor sediments, which may predominate in the west, and Saharan dust that predominates in the center and in the east. Within a nephloid layer above reduced continental margin sediments in the Eastern Basin, below the Mauritanian upwelling region, we report the lowest particulate δ56Fe values for both total and ligand-leachable Fe, suggesting a transfer of isotopically light dissolved porewater Fe2+ to the particulate phase. In contrast, δ56Fe values within a nephloid layer near Bermuda are similar to values higher in the water column. Within a hydrothermal plume sampled at the TAG hydrothermal field on the mid-Atlantic Ridge

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

    NASA Astrophysics Data System (ADS)

    Zhang, Liping; Zhao, Chuanhu

    2015-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  18. Decadal variability of extreme wave height representing storm severity in the northeast Atlantic and North Sea since the foundation of the Royal Society

    NASA Astrophysics Data System (ADS)

    Santo, H.; Taylor, P. H.; Gibson, R.

    2016-09-01

    Long-term estimation of extreme wave height remains a key challenge because of the short duration of available wave data, and also because of the possible impact of climate variability on ocean waves. Here, we analyse storm-based statistics to obtain estimates of extreme wave height at locations in the northeast Atlantic and North Sea using the NORA10 wave hindcast (1958-2011), and use a 5 year sliding window to examine temporal variability. The decadal variability is correlated to the North Atlantic oscillation and other atmospheric modes, using a six-term predictor model incorporating the climate indices and their Hilbert transforms. This allows reconstruction of the historic extreme climate back to 1661, using a combination of known and proxy climate indices. Significant decadal variability primarily driven by the North Atlantic oscillation is observed, and this should be considered for the long-term survivability of offshore structures and marine renewable energy devices. The analysis on wave climate reconstruction reveals that the variation of the mean, 99th percentile and extreme wave climates over decadal time scales for locations close to the dominant storm tracks in the open North Atlantic are comparable, whereas the wave climates for the rest of the locations including the North Sea are rather different.

  19. Decadal variability of extreme wave height representing storm severity in the northeast Atlantic and North Sea since the foundation of the Royal Society

    PubMed Central

    Taylor, P. H.; Gibson, R.

    2016-01-01

    Long-term estimation of extreme wave height remains a key challenge because of the short duration of available wave data, and also because of the possible impact of climate variability on ocean waves. Here, we analyse storm-based statistics to obtain estimates of extreme wave height at locations in the northeast Atlantic and North Sea using the NORA10 wave hindcast (1958–2011), and use a 5 year sliding window to examine temporal variability. The decadal variability is correlated to the North Atlantic oscillation and other atmospheric modes, using a six-term predictor model incorporating the climate indices and their Hilbert transforms. This allows reconstruction of the historic extreme climate back to 1661, using a combination of known and proxy climate indices. Significant decadal variability primarily driven by the North Atlantic oscillation is observed, and this should be considered for the long-term survivability of offshore structures and marine renewable energy devices. The analysis on wave climate reconstruction reveals that the variation of the mean, 99th percentile and extreme wave climates over decadal time scales for locations close to the dominant storm tracks in the open North Atlantic are comparable, whereas the wave climates for the rest of the locations including the North Sea are rather different. PMID:27713662

  20. Update on geographic spread of invasive lionfishes (Pterois volitans [Linnaeus, 1758] and P. miles [Bennett, 1828]) in the Western North Atlantic Ocean, Caribbean Sea and Gulf of Mexico

    USGS Publications Warehouse

    Schofield, Pamela J.

    2010-01-01

    The Indo-Pacific lionfishes (Pterois volitans [Linnaeus, 1758] and P. miles [Bennett, 1828]: Family Scorpaenidae) are the first nonnative marine fishes to establish in the Western North Atlantic/Caribbean region. The chronology of the invasion was reported last year (Schofield 2009) using records from the US Geological Survey's Nonindigenous Aquatic Species database. This article provides an update of lionfish geographic spread (as of October 2010) and predictions of future range.

  1. Warmer, deeper, and greener mixed layers in the North Atlantic subpolar gyre over the last 50 years.

    PubMed

    Martinez, Elodie; Raitsos, Dionysios E; Antoine, David

    2016-02-01

    Shifts in global climate resonate in plankton dynamics, biogeochemical cycles, and marine food webs. We studied these linkages in the North Atlantic subpolar gyre (NASG), which hosts extensive phytoplankton blooms. We show that phytoplankton abundance increased since the 1960s in parallel to a deepening of the mixed layer and a strengthening of winds and heat losses from the ocean, as driven by the low frequency of the North Atlantic Oscillation (NAO). In parallel to these bottom-up processes, the top-down control of phytoplankton by copepods decreased over the same time period in the western NASG, following sea surface temperature changes typical of the Atlantic Multi-decadal Oscillation (AMO). While previous studies have hypothesized that climate-driven warming would facilitate seasonal stratification of surface waters and long-term phytoplankton increase in subpolar regions, here we show that deeper mixed layers in the NASG can be warmer and host a higher phytoplankton biomass. These results emphasize that different modes of climate variability regulate bottom-up (NAO control) and top-down (AMO control) forcing on phytoplankton at decadal timescales. As a consequence, different relationships between phytoplankton, zooplankton, and their physical environment appear subject to the disparate temporal scale of the observations (seasonal, interannual, or decadal). The prediction of phytoplankton response to climate change should be built upon what is learnt from observations at the longest timescales.

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

    NASA Astrophysics Data System (ADS)

    Delworth, T. L.

    2002-05-01

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

  3. 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.

  4. 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.

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

    PubMed

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

    2004-03-11

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

  6. Orbital and suborbital variability in North Atlantic bottom water temperature obtained from deep-sea ostracod Mg/Ca ratios

    USGS Publications Warehouse

    Cronin, T. M.; Dwyer, G.S.; Baker, P.A.; Rodriguez-Lazaro, J.; DeMartino, D.M.

    2000-01-01

    Magnesium/calcium (Mg/Ca) ratios were measured in the deep-sea ostracod (Crustacea) genus Krithe from Chain core 82-24-4PC from the western mid-Atlantic Ridge (3427 m) in order to estimate ocean circulation and bottom water temperature (BWT) variability over the past 200,000 years. Mg/Ca ratios have been used as a paleothermometer because the ratios are controlled primarily by ambient water temperatures at the time the organism secretes its adult carapace. Over the past two glacial-interglacial cycles, Mg/Ca values oscillated between about 7 mmol/mol and 12 mmol/mol, equivalent to a BWT range of 0 to > 3.5??C. The lowest values were obtained on specimens from glacial marine isotope stages (MISs) 2, 4 and 6; the highest values were obtained from specimens from the early part of the Holocene interglacial (MIS 1), and also from MISs 5 and 7. These trends suggest that BWTs in the North Atlantic Ocean fluctuate over orbital time scales. Suborbital variability in Mg/Ca ratios and BWT was also observed for the past 100,000 years. Ratios rose from ~8 mmol/mol to ~10 mmol/mol (implying a BWT increase of ~1 to 3??C) during 14 Mg/Ca excursions. The highest ratios were found in Krithe dated at approximately 32, 36-38, 43, 48, 73, 85 and 93 ka. Although the age model for the Chain 82-24-4PC and temporal resolution do not allow precise correlation, some of these deep-sea bottom temperature excursions appear to correspond to Heinrich events recorded in other regions of the North Atlantic and perhaps Dansgaard-Oeschger interstadial events recorded in Greenland ice cores. If confirmed, this would support the hypothesis that millennial-scale oscillations of climate in the North Atlantic are capable of affecting global climate via thermohaline circulation changes. (C) 2000 Elsevier Science B.V.

  7. Aerosol and CCN Concentrations under Extremely High DMS Levels over the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Deng, C.; Brooks, S. D.; Thornton, D. C.; Bell, T. G.; Saltzman, E. S.; De Bruyn, W. J.

    2013-12-01

    Despite numerous studies since the CLAW hypothesis was first suggested in 1987, the extent to which marine phytoplankton derived dimethyl sulfide (CH3SCH3, DMS) contributes to marine atmospheric aerosol populations and the ability of those aerosols to act as cloud condensation nuclei (CCN) remains unclear, especially over oceanic areas obviously influenced by continental sources. Here, we present data from a cruise aboard the R/V Knorr over the North Atlantic during June-July 2011which passed through areas of both high and low phytoplankton biomasses, as well as intermediate primary production bloom regions where extremely high DMS concentrations (over 1800 pptv) were observed. Continuous ambient measurements of aerosol concentration, cloud condensation nuclei (CCN) concentration, aerosol particle size distributions, and surface seawater and atmospheric dimethyl sulfide (DMS) concentrations were performed simultaneously during the three-week-cruise. Throughout the cruise, CCN concentrations were measured at a series of five supersaturation levels and used to derive the critical supersaturation required for aerosols to activate as CCN. Air masses have been classified into three different categories based on the 48-hr back trajectories, i.e., air mass influenced by continents, coasts and the open ocean. Aerosol concentrations have noticeably different patterns depending on the air mass paths. Continually high CCN and aerosol concentrations had been found to coincide with high DMS concentration over the open ocean, which may be explained by the nucleation and condensational growth in marine boundary layer (MBL) resulting from the oxidation products of DMS or primary aerosols from the sea surface. Calculation of DMS oxidation rates based on the variation of DMS in the lower atmosphere and sea-to-air flux measurement during the whole cruise verified that the influence of continental sources on marine atmosphere is significant during the majority of sample times

  8. Albatross species demonstrate regional differences in North Pacific marine contamination

    USGS Publications Warehouse

    Finkelstein, M.; Keitt, B.S.; Croll, D.A.; Tershy, B.; Jarman, Walter M.; Rodriguez-Pastor, S.; Anderson, D.J.; Sievert, P.R.; Smith, D.R.

    2006-01-01

    Recent concern about negative effects on human health from elevated organochlorine and mercury concentrations in marine foods has highlighted the need to understand temporal and spatial patterns of marine pollution. Seabirds, long-lived pelagic predators with wide foraging ranges, can be used as indicators of regional contaminant patterns across large temporal and spatial scales. Here we evaluate contaminant levels, carbon and nitrogen stable isotope ratios, and satellite telemetry data from two sympatrically breeding North Pacific albatross species to demonstrate that (1) organochlorine and mercury contaminant levels are significantly higher in the California Current compared to levels in the high-latitude North Pacific and (2) levels of organochlorine contaminants in the North Paci.c are increasing over time. Black-footed Albatrosses (Phoebastria nigripes) had 370-460% higher organochlorine (polychlorinated biphenyls [PCBs], dichlorodiphenyltrichloroethanes [DDTs]) and mercury body burdens than a closely related species, the Laysan Albatross (P. immutabilis), primarily due to regional segregation of their North Pacific foraging areas. PCBs (the sum of the individual PCB congeners analyzed) and DDE concentrations in both albatross species were 130-360% higher than concentrations measured a decade ago. Our results demonstrate dramatically high and increasing contaminant concentrations in the eastern North Pacific Ocean, a finding relevant to other marine predators, including humans. ?? 2006 by the Ecological Society of America.

  9. 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

  10. 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.

  11. Cryptic species in marine polychaete and their independent introduction from North America to Europe.

    PubMed

    Bastrop, R; Jürss, K; Sturmbauer, C

    1998-02-01

    The vast body of ballast water carried across oceans by freight ships represents a major source for the introduction of foreign species into marine ecosystems. The worm Marenzelleria viridis, originally found only in North America, appeared in estuaries of the North Sea in 1979 and 6 years later also in the Baltic, where it has developed into a major faunal element. Two competing hypotheses are discussed here: either both populations owe their presence to a single introductory event in the North Sea, or each population originated from a separate introduction. Our phylogeographic analysis of Baltic, North Sea and American Marenzelleria, based on mitochondrial 16S rDNA sequences (326-bp segment) of 98 individuals from 17 localities on the North American, North Sea, and Baltic coasts not only favors the two-event hypothesis, but also separates the locations of origin for the introductions. Eighteen mitochondrial genotypes were identified altogether. In agreement with allozyme data, three lineages were identified: genotypes assigned to the same lineage differed from each other by up to 5 point mutations, and those assigned to different lineages differed by up to 17. The existence of three morphologically indistinguishable, and thus cryptic, species is therefore suggested. The individuals from the Baltic Sea probably originated from the Atlantic coast of the United States between Chesapeake Bay and Georgia, and the North Sea populations may stem from the U.S. coast region north of Chesapeake Bay to Nova Scotia. Despite their similar morphologies, the two European Marenzelleria species may differ ecologically with respect to their preference for habitat salinity. Assuming that transport via ballast water occurs quite frequently, we hypothesize that both European cryptic species of Marenzelleria may originally have been introduced to both the North Sea and the Baltic Sea but that neither of them was able to proliferate in both water bodies owing to their differential

  12. Freshwater fluxes into the subpolar North Atlantic from secular trends in Arctic land ice mass balance

    NASA Astrophysics Data System (ADS)

    Bamber, J. L.; Enderlin, E. M.; Howat, I. M.; Wouters, B.; van den Broeke, M.

    2015-12-01

    Freshwater fluxes (FWF) from river runoff and precipitation minus evaporation for the pan Arctic seas are relatively well documented and prescribed in ocean GCMs. Fluxes from Greenland and Arctic glaciers and ice caps on the other hand are generally ignored, despite their potential impacts on ocean circulation and marine biology and growing evidence for changes to the hydrography of parts of the subpolar North Atlantic. In a previous study we determined the FWF from Greenland for the period 1958-2010 using a combination of observations and regional climate modeling. Here, we update the analysis with data from new satellite observations to extend the record both in space and time. The new FWF estimates cover the period 1958-2014 and include the Canadian, Russian and Norwegian Arctic (Svalbard) in addition to the contributions from Greenland. We combine satellite altimetry (including CryoSat 2) with grounding line flux data, regional climate modeling of surface mass balance and gravimetry to produce consistent estimates of solid ice and liquid FWF into the Arctic and North Atlantic Oceans. The total cumulative FWF anomaly from land ice mass loss started to increase significantly in the mid 1990s and now exceeds 5000 km^3, a value that is about half of the Great Salinity Anomaly of the 1970s. The majority of the anomaly is entering two key areas of deep water overturning in the Labrador and Irminger Seas, at a rate that has been increasing steadily over the last ~20 years. Since the mid 2000s, however, the Canadian Arctic archipelago has been making a significant contribution to the FW anomaly entering Baffin Bay. Tracer experiments with eddy-permitting ocean GCMs suggest that the FW input from southern Greenland and the Canadian Arctic should accumulate in Baffin Bay with the potential to affect geostrophic circulation, stratification in the region and possibly the strength of the Atlantic Meridional Overturning Circulation. We also examine the trajectory of

  13. Modeling the drift of massive icebergs to the subtropical North Atlantic

    NASA Astrophysics Data System (ADS)

    Condron, A.; Hill, J. C.

    2013-12-01

    New evidence from high-resolution seafloor bathymetry data indicates that massive (>300m thick) icebergs from the Laurentide Ice Sheet (LIS) drifted south to the tip of Florida during the last deglaciation. This finding is particularly exciting as it contradicts evidence from marine sediments that icebergs were mainly confined to the subpolar North Atlantic (50 - 70N) at this time. Indeed, the freshwater released from icebergs melting in the subpolar gyre is repeatedly cited as a main trigger for a slow-down of the Atlantic MOC in the past, and the possible cause of any climate cooling related to the melting of the Greenland Ice Sheet in the future. Using a sophisticated iceberg model (MITberg), coupled to a high (18-km; 1/6 deg.) resolution ocean model (MITgcm), we investigate the ocean circulation dynamics required to allow icebergs to drift to the southern tip of Florida. We find that icebergs only reach this location if they turn right at the Grand Banks of Newfoundland, and stay inshore of the Gulf Stream all the way to Florida. Modern-day circulation dynamics do not readily allow this to happen as cold, southward flowing, Labrador Current Water (important for iceberg survival) has little penetration south of Cape Hatteras. However, when a liquid meltwater flood is released from Hudson Bay at the same time, icebergs are rapidly transported (inshore of the Gulf Stream) in a narrow, buoyant, coastal current all the way to southern Florida. The meltwater and icebergs result in a significant freshening of the subtropical North Atlantic and weaken the strength of the Gulf Stream, suggesting such an event would have a large cooling effect on climate. We are only able to simulate the flow of meltwater and icebergs to the subtropics by modeling ocean circulation at a resolution that is 5 - 10 times higher than the majority of existing paleoclimate models; at lower resolutions the narrow, coastal boundary currents important for iceberg transport to the subtropics are

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

    Code of Federal Regulations, 2011 CFR

    2011-10-01

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

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

    Code of Federal Regulations, 2013 CFR

    2013-10-01

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

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

    Code of Federal Regulations, 2012 CFR

    2012-10-01

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

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

    Code of Federal Regulations, 2014 CFR

    2014-10-01

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

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

    Code of Federal Regulations, 2010 CFR

    2010-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Hartley, Ross; Roberts, Gareth; White, Nicky

    2013-04-01

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

  1. 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.

  2. 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.

  3. 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.

  4. The use of DNA barcoding to monitor the marine mammal biodiversity along the French Atlantic coast.

    PubMed

    Alfonsi, Eric; Méheust, Eleonore; Fuchs, Sandra; Carpentier, François-Gilles; Quillivic, Yann; Viricel, Amélia; Hassani, Sami; Jung, Jean-Luc

    2013-12-30

    In the last ten years, 14 species of cetaceans and five species of pinnipeds stranded along the Atlantic coast of Brittany in the North West of France. All species included, an average of 150 animals strand each year in this area. Based on reports from the stranding network operating along this coast, the most common stranding events comprise six cetacean species (Delphinus delphis, Tursiops truncatus, Stenella coeruleoalba, Globicephala melas, Grampus griseus, Phocoena phocoena)and one pinniped species (Halichoerus grypus). Rare stranding events include deep-diving or exotic species, such as arctic seals. In this study, our aim was to determine the potential contribution of DNA barcoding to the monitoring of marine mammal biodiversity as performed by the stranding network. We sequenced more than 500 bp of the 5' end of the mitochondrial COI gene of 89 animals of 15 different species (12 cetaceans, and three pinnipeds). Except for members of the Delphininae, all species were unambiguously discriminated on the basis of their COI sequences. We then applied DNA barcoding to identify some "undetermined" samples. With again the exception of the Delphininae, this was successful using the BOLD identification engine. For samples of the Delphininae, we sequenced a portion of the mitochondrial control region (MCR), and using a non-metric multidimentional scaling plot and posterior probability calculations we were able to determine putatively each species. We then showed, in the case of the harbour porpoise, that COI polymorphisms, although being lower than MCR ones, could also be used to assess intraspecific variability. All these results show that the use of DNA barcoding in conjunction with a stranding network could clearly increase the accuracy of the monitoring of marine mammal biodiversity. PMID:24453548

  5. The use of DNA barcoding to monitor the marine mammal biodiversity along the French Atlantic coast

    PubMed Central

    Alfonsi, Eric; Méheust, Eleonore; Fuchs, Sandra; Carpentier, François-Gilles; Quillivic, Yann; Viricel, Amélia; Hassani, Sami; Jung, Jean-Luc

    2013-01-01

    Abstract In the last ten years, 14 species of cetaceans and five species of pinnipeds stranded along the Atlantic coast of Brittany in the North West of France. All species included, an average of 150 animals strand each year in this area. Based on reports from the stranding network operating along this coast, the most common stranding events comprise six cetacean species (Delphinus delphis, Tursiops truncatus, Stenella coeruleoalba, Globicephala melas, Grampus griseus, Phocoena phocoena)and one pinniped species (Halichoerus grypus). Rare stranding events include deep-diving or exotic species, such as arctic seals. In this study, our aim was to determine the potential contribution of DNA barcoding to the monitoring of marine mammal biodiversity as performed by the stranding network. We sequenced more than 500 bp of the 5’ end of the mitochondrial COI gene of 89 animals of 15 different species (12 cetaceans, and three pinnipeds). Except for members of the Delphininae, all species were unambiguously discriminated on the basis of their COI sequences. We then applied DNA barcoding to identify some “undetermined” samples. With again the exception of the Delphininae, this was successful using the BOLD identification engine. For samples of the Delphininae, we sequenced a portion of the mitochondrial control region (MCR), and using a non-metric multidimentional scaling plot and posterior probability calculations we were able to determine putatively each species. We then showed, in the case of the harbour porpoise, that COI polymorphisms, although being lower than MCR ones, could also be used to assess intraspecific variability. All these results show that the use of DNA barcoding in conjunction with a stranding network could clearly increase the accuracy of the monitoring of marine mammal biodiversity. PMID:24453548

  6. Knowledge of marine fish trematodes of Atlantic and Eastern Pacific Oceans.

    PubMed

    Bray, Rodney A; Diaz, Pablo E; Cribb, Thomas H

    2016-03-01

    A brief summary of the early history of the study of Atlantic Ocean marine fish digeneans is followed by a discussion of the occurrence and distribution of these worms in the Atlantic Ocean and adjacent Eastern Pacific Ocean, using the Provinces of the 'Marine Ecoregions' delimited by Spalding et al. (Bioscience 57:573-583, 2007). The discussion is based on a database of 9,880 records of 1,274 species in 430 genera and 45 families. 8,633 of these records are from the Atlantic Ocean, including 1,125 species in 384 genera and 45 families. About 1,000 species are endemic to the Atlantic Ocean Basin. The most species-rich families in the Atlantic Ocean are the Opecoelidae Ozaki, 1925, Hemiuridae Looss, 1899 and Bucephalidae Poche, 1907, and the most wide-spread the Opecoelidae, Hemiuridae, Acanthocolpidae Lühe, 1906, Lepocreadiidae Odhner, 1905 and Lecithasteridae Odhner, 1905. A total of 109 species are shared by the Atlantic Ocean and the Eastern Pacific, made up of cosmopolitan, circum-boreal, trans-Panama Isthmus and Magellanic species. The lack of genetic evaluation of identifications is emphasised and the scope for much more work is stressed.

  7. New observational capabilities on atmospheric sciences of the Eastern North Atlantic (ENA) Graciosa island ARM facility

    NASA Astrophysics Data System (ADS)

    Nitschke, Kim; Ortega, Paul; Azevedo, Eduardo; Miller, Mark

    2016-04-01

    One source of uncertainty that thwarts accurate and comprehensive representation of the present and future climate in models is the response of shallow cloud systems to changes in atmospheric greenhouse gases and aerosols. Low clouds systems that prevail over subtropical oceans, in particular, play a critical role in boundary layer dynamics and in the global climate, despite being poorly represented in climate models. The Azores have been identified as an optimal site to conduct research aimed at better understanding the physical processes and life cycle of marine stratocumulus and other marine boundary layer clouds. The United States Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Program has been providing data to advance research from atmospheric observations at diverse climatic regimes around the world (http://www.arm.gov/) for over 20 years. Since 2009, the Azores has been included in this global program. The campaign of the ARM Mobile Facility at Graciosa Island, Azores, in the context of the Clouds, Aerosol and Precipitation in the Marine Boundary Layer (CAP-MBL) project, added the most extensive and comprehensive dataset of marine boundary layer (MBL) clouds to date. Solid preliminary findings from this valuable data set have been used to understand interactions between the cloud microphysical and macrophysical processes in marine boundary layer clouds that play a fundamental role in the cloud dynamics and precipitation, which in turn determine cloud radiative properties that impact on the energy balance of the Earth. Based upon the design and siting from the previous ARM Mobile Facility in support of CAP-MBL, the new Eastern North Atlantic (ENA) fixed site joined the global network of ARM Climate Research Facilities in October 2013. Since then, this user facility has augmented its baseline measurement capability to include a Ka-/W-Band scanning cloud radar, an X-Band precipitation radar and Raman and Doppler lidars. Coupled

  8. Carcass analog provides marine subsidies for macroinvertebrates and juvenile Atlantic 8 salmon in temperate oligotrophic streams

    USGS Publications Warehouse

    Guyette, Margaret Q.; Loftin, Cynthia S.; Zydlewski, Joseph; Cunjak, Richard

    2014-01-01

    Assimilation of nutrients from carcass analogues was both direct and indirect, and a nutrient legacy was evident in the second year of sampling. Incorporation of nutrients from the pellets at a range of heights in the food web demonstrated the potential for marine-derived subsidies to contribute to freshwater ecosystem processes in Atlantic salmon nursery streams.

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

    NASA Astrophysics Data System (ADS)

    Lienert, Fabian; Doblas-Reyes, Francisco J.

    2016-07-01

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

  10. 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.

  11. 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.

  12. The Influence of North Atlantic Valves and Gateways on Neogene Climate Change

    NASA Astrophysics Data System (ADS)

    Wright, J. D.

    2015-12-01

    Our current proxies for pCO2 suggest Neogene levels were relatively constant (~300 ± 100 ppm) except for the middle Miocene Climatic Optimum with estimates approaching 400 ± 100 ppm. Yet, the East Antarctic Ice Sheet became a polar ice sheet and permanent feature on Earth while large-scale Northern Hemisphere ice sheets waxed and waned with scant differences in pCO2. Three possibilities to explain these observations are: 1) our pCO2 proxies are incorrect; 2) Earth's climate is far more sensitive than our current model simulations suggest; or 3) tectonic differences overprinted accepted climate sensitivity to pCO2. Two marine gateways that influenced Neogene deep-water circulation are the Greenland-Scotland Ridge and the Central American Isthmus (CAI). Driven by mantle plume variations under Iceland, the GSR acted as a regulator of Northern Component Water (NCW, analogous to NADW) by controlling access to the dense polar waters to the north. During the latest Miocene and early Pliocene, mean depths along the GSR and NCW production were at their greatest. By the late Pliocene (~3 Ma), mantle plume activity increased and NCW production waned. Most researchers have focused on surface water changes (e.g., salinity) in relating closure of the CAI to Pliocene climate change. However, I propose that its primary influence came with the elimination of low-latitude, deep-water connection between the Atlantic and Pacific. Combined with vigorous NCW production, closure of the CAI re-distributed nutrients between the oceans. Carbon isotope and Cd/Ca profiles indicate that "modern" basin-to-basin differences started during the latest Miocene and were fully developed in the Pliocene. The South Atlantic path for NCW also delivered heat to the Southern Ocean, facilitating sea ice changes, as indicated by biosiliceous patterns. These tectonic boundary changes and their affects on surface and deep water circulation contributed to the Pliocene pause in global cooling that began in

  13. Does the Fukushima NPP disaster affect the caesium activity of North Atlantic Ocean fish?

    NASA Astrophysics Data System (ADS)

    Kanisch, G.; Aust, M.-O.

    2013-08-01

    Fillet samples of marine fish collected from the East/West Greenland currents (GC) and from the Baltic Sea (BS) have been investigated by gamma-ray spectrometry within the regular German monitoring programme. In samples of the second half of 2011, 134Cs traces have been detected that are suggested to originate from the Fukushima fallout that was deposited in March/April 2011 over the northern North Atlantic and accumulated by fish. The radionuclide 134Cs (half-life 2 yr) was indeed detected with quite small activities at about 0.0036 Bq kg-1 w.w. Existing box models describing the transport of Cs within seawater boxes of the northeast Atlantic allowed for estimation of 134Cs contributions from other sources, i.e. from the Chernobyl fallout and from discharges by the two major European nuclear reprocessing plants; both were negligible around Greenland, while for the Chernobyl fallout a small 134Cs background contribution to BS fish was estimated. Model results confirmed the level of 134C measured in BS fish and showed its maximum to have occurred in winter 2011/2012 followed by a continuous decrease. It was also determined that 134Cs activity, but not that of 134Cs, showed a significant negative correlation with sampling depth (150-400 m) of GC fish; this strengthens our Fukushima fallout assumption. As a result, the Fukushima fallout in these sea areas only marginally enhanced (GC: 4%; BS: 0.1%) pre-Fukushima levels of individual dose rates received by human fish consumers; the addition was around 0.001 μSv following the consumption of 10 kg of fish per year, which is not expected to cause concern according to present guidelines for radiation protection.

  14. Does the Fukushima NPP disaster affect the caesium activity of North Atlantic Ocean fish?

    NASA Astrophysics Data System (ADS)

    Kanisch, G.; Aust, M.-O.

    2013-03-01

    Fillet samples of marine fish collected from the East/West Greenland current (GC) and from the Baltic Sea (BS), have been investigated by gamma-ray spectrometry within the regular German monitoring program. In samples of the second half of 2011 134Cs traces have been detected, suggested to originate from the Fukushima fallout being deposited in March/April 2011 over the northern North Atlantic and accumulated by fish. The radionuclide 134Cs (half-live 2 yr) was indeed detected with quite small activities at about 0.0036 Bq kg-1 w.w. Existing box-models describing the transport of Cs within seawater boxes of the NE Atlantic allowed estimating that 134Cs contributions from other sources, i.e. from the Chernobyl fallout and from discharges by the two major European nuclear reprocessing plants, both were negligible around Greenland, while for the Chernobyl fallout a small 134Cs background contribution to BS fish was estimated. Model results confirmed the level of 134Cs measured in BS fish and showed its maximum to have occurred in winter 2011/2012 followed by a continuous decrease. It was also determined that 134Cs activity, but not that of 134Cs, showed a significant negative correlation with sampling depth (150-400 m) of GC fish; this strengthens our Fukushima fallout assumption. As a result, the Fukushima fallout in these sea areas only marginally enhanced (GC: 4%; BS: 0.1%) pre-Fukushima levels of individual dose rates received by human fish consumers; the addition was around 0.001 μSv following the consumption of 10 kg fish per year, which is not expected to cause concern according to present guidelines for radiation protection.

  15. Atmospheric Electric Field measurements at Eastern North Atlantic ARM Climate Research Facility: Global Electric Circuit Evolution

    NASA Astrophysics Data System (ADS)

    Lopes, Francisco; Silva, Hugo; Nitschke, Kim; Azevedo, Eduardo

    2016-04-01

    The Eastern North Atlantic (ENA) facility of the ARM programme (established an supported by the U.S. Department of Energy with the collaboration of the local government and University of the Azores), is located at Graciosa Island of the Azores Archipelago (39° N; 28° W). It constitutes a strategic observatory for Atmospheric Electricity since it is located in the Atlantic Ocean basin exposed to clean marine aerosol conditions which reduces the well known spectral signature of atmospheric pollution and enables the study of the so called Global Electrical Circuit (GEC). First evidences of the existence of a GEC affecting the Earth's Electric Environment has retrieved by the Carnegie cruise expedition, in what became known as the Carnegie Curve. Those measurements were made in the Ocean in several campaigns and the present studies aims at reconsidering measurements in similar conditions but in a long-term basis, at least 5 years. This will contribute to the understanding of the long-term evolution of the Ionospheric Potential (IP). In literature there is theoretical evidence that it is decreasing IP in strength, but that conjecture is still lacking valid experimental evidence. Moreover, to clearly identify the GEC signal two effects must be taken into account: the effect of surface radon gas variation, because the Azores Archipelago is a seismic active region the possible influence of Earthquakes cannot be discarded easily; the effect of short-term solar activity on the Atmospheric Electricity modulation, solar flares emitting solar particles (e.g., solar energetic protons) need to be considered in this study.

  16. The interplay between particulate and dissolved neodymium in the Western North Atlantic: First insights and interpretations

    NASA Astrophysics Data System (ADS)

    Stichel, T.; Kretschmer, S.; Lambelet, M.; van de Flierdt, T.; Rutgers van der Loeff, M.; Rijkenberg, M. J. A.; Gerringa, L. J.; De Baar, H. J. W.

    2014-12-01

    Dissolved neodymium (Nd) isotopes (expressed as ɛNd) have been widely used as a water mass tracer to reconstruct paleo ocean circulation. However, the marine geochemical cycle of Nd is not well understood. Unclear input mechanisms, scarcity of available data, and observed decoupling between dissolved ɛNd and Nd concentration patterns ([Nd]) are only a few of the unresolved issues. The latter is often referred to as the Nd paradox(e.g. Goldstein and Hemming 2003). Here we revisit this paradox with an unprecedented data set on particulate Nd isotope and concentration data from five stations along the Dutch GEOTRACES transect GA02 in the western North and equatorial Atlantic Ocean (cruises 64PE319 and 64PE321 from April to July 2010). Particulates were collected with in-situ pumps on 0.8 µm Supor filters and subjected to a total digestion procedure in the home laboratory. The particulates collected farthest north (Irminger Sea and Labrador Sea) show a strong affinity to the nearby land masses in their Nd isotope composition: Very negative values (ɛNd ≈-20) are observed in the Labrador Sea, which is surrounded by old continental rocks. More positive values of up to ɛNd ≈-4 are found east of Greenland probably derived from the Nansen Fjord Formation's basaltic rocks. In these two areas the particulate ɛNd is offset from dissolved Nd isotopes by up to 7.7 ɛ-units, but reveals a similar vertical distribution. Further downstream of the flow path of the North Atlantic Deep Water, dissolved and particulate Nd isotopic compositions in the water column seem to merge and become indistinguishable from one another south of Bermuda (BATS station). This seems to indicate that particulate and dissolved fractions exchange with increasing distance from source regions and age of water masses. Neodymium concentrations in particulates [pNd] are low (KD<5%) and invariant. However, most stations show a significant increase in [pNd] close to the seafloor, where [pNd] nearly

  17. Nonmethane hydrocarbons at Pico Mountain, Azores: 1. Oxidation chemistry in the North Atlantic region

    NASA Astrophysics Data System (ADS)

    Helmig, D.; Tanner, D. M.; Honrath, R. E.; Owen, R. C.; Parrish, D. D.

    2008-10-01

    Measurements of nonmethane hydrocarbons (NMHC) at the Pico Mountain observatory at 2225 m asl on Pico Island, Azores, Portugal, from August 2004 to August 2005 (in part overlapping with the field campaign of the International Consortium on Atmospheric Research on Transport and Transformation study) were used to investigate NMHC sources and seasonal oxidation chemistry in the central North Atlantic region. Levels of anthropogenic NMHC were characteristic of the marine free troposphere. Their concentrations were low compared to continental sites at higher northern latitudes, but higher than data reported from a similarly located Pacific mountain site at Mauna Loa Observatory, Hawaii. These higher NMHC levels are indicative of a greater influence of the adjacent continents on air composition at Pico. Substantially enhanced NMHC concentrations during the summers of 2004 and 2005 were attributed to long-range transport of biomass burning plumes originating from fires in northern Canada, Alaska, and Siberia. This finding exemplifies the continuing impact of biomass burning plumes on atmospheric composition and chemistry many days downwind of these emission sources. Seasonal cycles with lower NMHC concentrations and lower ratios of more reactive to less reactive NMHC during summer reflect the higher degree of photochemical processing occurring during transport. The NMHC concentrations indicate no significant role of chlorine atom oxidation on NMHC. Ozone above 35 ppbv was measured at Pico Mountain throughout all seasons. Enhanced ozone levels were observed in air that had relatively "fresh" photochemical signatures (e.g., ln [propane]/[ethane] > -2.5). During spring-summer air that was more processed ("older" air with ln [propane]/[ethane] < -2.5) on average had lower ozone levels (down to <20 ppbv). This relationship indicates that conditions in the lower free troposphere over the mid-North Atlantic during the spring and summer lead to net photochemical ozone destruction

  18. 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.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  1. 2 - 4 million years of sedimentary processes in the Labrador Sea: implication for North Atlantic stratigraphy

    NASA Astrophysics Data System (ADS)

    Mosher, D. C.; Saint-Ange, F.; Campbell, C.; Piper, D. J.

    2012-12-01

    Marine sedimentary records from the western North Atlantic show that a significant portion of sediment deposited since the Pliocene originated from the Canadian Shield. In the Labrador Sea, previous studies have shown that bottom currents .strongly influenced sedimentation during the Pliocene, while during the Quaternary, intensification of turbidity current flows related to meltwater events were a dominant factor in supplying sediment to the basin and in the development of the North Atlantic Mid-Ocean Channel (NAMOC). Despite understanding this general pattern of sediment flux, details regarding the transfer of sediment from the Labrador Shelf to deep water and from the Labrador Sea to the North Atlantic remain poorly understood. Our study focuses on sedimentary processes occurring along the Labrador margin since the Pliocene and their consequences on the margin architecture, connection to the NAMOC, and role in sediment flux from the Labrador basin to the Sohm Abyssal Plain. Piston core and high resolution seismic data reveal that during the Pliocene to mid Pleistocene, widespread slope failures led to mass transport deposition along the entire Labrador continental slope. After the mid Pleistocene, sedimentation along the margin was dominated by the combined effects of glaciation and active bottom currents. On the shelf, prograded sedimentary wedges filled troughs and agraded till sheets form intervening banks. On the slope, stacked glaciogenic fans developed seaward of transverse troughs between 400 and 2800 mbsl. On the lower slope, seismic data show thick sediment drifts capped by glacio-marine mud. This unit is draped by well stratified sediment and marks a switch from a contourite dominated regime to a turbidite dominated regime. This shift occurred around 0.5 - 0.8 ka and correlates to the intensification of glaciations. Late Pleistocene sediments on the upper slope consist of stratified sediments related to proglacial plume fall-out. Coarse grained

  2. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

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

  4. 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

  5. Constraints on values of biological parameters by observed turbulence in a quasi-2D phytoplankton model of the North Atlantic

    NASA Astrophysics Data System (ADS)

    Hahn-Woernle, Lisa; Dijkstra, Henk A.; van der Woerd, Hans J.

    2013-04-01

    Constraints on values of biological parameters by observed turbulence in a quasi-2D phytoplankton model of the North Atlantic Session and Session Number: Scaling and complex Physical and Biogeophysical Processes in the Atmosphere, Ocean and climate (NP3.1) Preferred Mode of Presentation: Oral Lisa Hahn-Woernle¹, Henk A. Dijkstra¹ & Hans J. van der Woerd² 1. Institute for Marine and Atmospheric research Utrecht, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands. 2. Institute for Environmental Studies, VU University, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands. During the STRATIPHYT cruises in Summer 2009 and Spring 2011 in-situ plankton and nutrient concentrations as well as upper-ocean turbulence characteristics were measured from Las Palmas to Reykjavik [1,2]. The measurements agree with previous findings that the incoming light intensity and the stratification of the upper ocean set important conditions for the initiation of the phytoplankton bloom close to the surface and also for a possible shift to a deep chlorophyll maximum below the mixed layer. These strong characteristic spatial patterns and temporal cycles of phytoplankton surface concentration are also observed in satellite images of chlorophyll-a concentration in the Northern Atlantic. To understand the meridional depth (upper 200 m) variation of the phytoplankton distributions, a quasi-2D phytoplankton model was used. The results indicate that with the given profiles of the turbulent vertical mixing coefficient, only a very limited interval for the biological model parameters leads to the observed depth of the phytoplankton maximum. [1] E. Jurado, H. van der Woerd and H. A. Dijkstra, Microstructure measurements along a quasi-meridional transect in the North Atlantic, J. Geophysical Res. Oceans, 117, C04016, doi:10.1029/2011JC007137, (2012). [2] E. Jurado, H. A. Dijkstra and H. van der Woerd, Microstructure observations during the spring 2011 STRATIPHYT-II cruise in the

  6. 75 FR 35432 - Atlantic Highly Migratory Species; North and South Atlantic Swordfish Quotas

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-22

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

  7. 78 FR 12705 - Atlantic Highly Migratory Species; North and South Atlantic 2013 Commercial Swordfish Quotas

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-25

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  9. Projected climate change impacts to the North Sea marine system

    NASA Astrophysics Data System (ADS)

    Schrum, Corinna

    2015-04-01

    Future climate change impacts to the North Sea marine system are driven by a combination of changes induced by the globally forced oceanic boundary conditions and the regional atmospheric and terrestrial changes. We reviewed the recent progress and the projected future change of the North Sea marine system as part of the North Sea Climate Change Assessment (NOSCCA) and focussed on three major aspects, namely the change of (i) sea level, the (ii) hydrographic and circulation changes of the North Sea and the (iii) changes in lower trophic level dynamics, biogeochemistry and ocean acidification. In recent years more and more regional climate change assessments became available for the North Sea and new developments contributed important understanding on regional processes mediating climate change impacts in the North Sea. Important new knowledge on regional future sea level change was gained by improved understanding of processes contributing to global sea level rise during the last decade. Assessment of climate change impacts to hydrography, circulation and biogeochemistry has benefited from new and advanced downscaling methods. The large number of regional studies enables now a critical review of the current knowledge on climate change impacts on the North Sea and allows the identification of challenges, robust changes, uncertainties and specific recommendations for future research. The long term trends in the climate conditions are superposed on the natural modes of variability and separating these to give a clear anthropogenic climate change signal is one of the 'grand challenges' of climate change impact studies in marine regions and of particular relevance for North Sea. The impact of natural variability on future annual average steric sea level, sea surface temperature and ocean acidification is less dominant compared to the climate change signal and their projected changes for the North Sea, namely rising future sea level, increasing surface temperature and

  10. Fungi Sailing the Arctic Ocean: Speciose Communities in North Atlantic Driftwood as Revealed by High-Throughput Amplicon Sequencing.

    PubMed

    Rämä, Teppo; Davey, Marie L; Nordén, Jenni; Halvorsen, Rune; Blaalid, Rakel; Mathiassen, Geir H; Alsos, Inger G; Kauserud, Håvard

    2016-08-01

    High amounts of driftwood sail across the oceans and provide habitat for organisms tolerating the rough and saline environment. Fungi have adapted to the extremely cold and saline conditions which driftwood faces in the high north. For the first time, we applied high-throughput sequencing to fungi residing in driftwood to reveal their taxonomic richness, community composition, and ecology in the North Atlantic. Using pyrosequencing of ITS2 amplicons obtained from 49 marine logs, we found 807 fungal operational taxonomic units (OTUs) based on clustering at 97 % sequence similarity cut-off level. The phylum Ascomycota comprised 74 % of the OTUs and 20 % belonged to Basidiomycota. The richness of basidiomycetes decreased with prolonged submersion in the sea, supporting the general view of ascomycetes being more extremotolerant. However, more than one fourth of the fungal OTUs remained unassigned to any fungal class, emphasising the need for better DNA reference data from the marine habitat. Different fungal communities were detected in coniferous and deciduous logs. Our results highlight that driftwood hosts a considerably higher fungal diversity than currently known. The driftwood fungal community is not a terrestrial relic but a speciose assemblage of fungi adapted to the stressful marine environment and different kinds of wooden substrates found in it.

  11. Fungi Sailing the Arctic Ocean: Speciose Communities in North Atlantic Driftwood as Revealed by High-Throughput Amplicon Sequencing.

    PubMed

    Rämä, Teppo; Davey, Marie L; Nordén, Jenni; Halvorsen, Rune; Blaalid, Rakel; Mathiassen, Geir H; Alsos, Inger G; Kauserud, Håvard

    2016-08-01

    High amounts of driftwood sail across the oceans and provide habitat for organisms tolerating the rough and saline environment. Fungi have adapted to the extremely cold and saline conditions which driftwood faces in the high north. For the first time, we applied high-throughput sequencing to fungi residing in driftwood to reveal their taxonomic richness, community composition, and ecology in the North Atlantic. Using pyrosequencing of ITS2 amplicons obtained from 49 marine logs, we found 807 fungal operational taxonomic units (OTUs) based on clustering at 97 % sequence similarity cut-off level. The phylum Ascomycota comprised 74 % of the OTUs and 20 % belonged to Basidiomycota. The richness of basidiomycetes decreased with prolonged submersion in the sea, supporting the general view of ascomycetes being more extremotolerant. However, more than one fourth of the fungal OTUs remained unassigned to any fungal class, emphasising the need for better DNA reference data from the marine habitat. Different fungal communities were detected in coniferous and deciduous logs. Our results highlight that driftwood hosts a considerably higher fungal diversity than currently known. The driftwood fungal community is not a terrestrial relic but a speciose assemblage of fungi adapted to the stressful marine environment and different kinds of wooden substrates found in it. PMID:27147245

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

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

  14. Alkalinity distribution in the western North Atlantic Ocean margins

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

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

  15. 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.

  16. 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.

  17. Oceanographic dynamics and the end of the last interglacial in the subpolar North Atlantic

    PubMed Central

    Mokeddem, Zohra; McManus, Jerry F.; Oppo, Delia W.

    2014-01-01

    The last interglacial interval was terminated by the inception of a long, progressive glaciation that is attributed to astronomically influenced changes in the seasonal distribution of sunlight over the earth. However, the feedbacks, internal dynamics, and global teleconnections associated with declining northern summer insolation remain incompletely understood. Here we show that a crucial early step in glacial inception involves the weakening of the subpolar gyre (SPG) circulation of the North Atlantic Ocean. Detailed new records of microfossil foraminifera abundance and stable isotope ratios in deep sea sediments from Ocean Drilling Program site 984 south of Iceland reveal repeated, progressive cold water-mass expansions into subpolar latitudes during the last peak interglacial interval, marine isotope substage 5e. These movements are expressed as a sequence of progressively extensive southward advances and subsequent retreats of a hydrographic boundary that may have been analogous to the modern Arctic front, and associated with rapid changes in the strength of the SPG. This persistent millennial-scale oceanographic oscillation accompanied a long-term cooling trend at a time of slowly declining northern summer insolation, providing an early link in the propagation of those insolation changes globally, and resulting in a rapid transition from extensive regional warmth to the dramatic instability of the subsequent ∼100 ka. PMID:25049405

  18. Lagged influence of North Atlantic Oscillation on population dynamics of a Mediterranean terrestrial salamander

    NASA Astrophysics Data System (ADS)

    Salvidio, Sebastiano; Oneto, Fabrizio; Ottonello, Dario; Pastorino, Mauro V.

    2016-04-01

    The North Atlantic Oscillation (NAO) is a large-scale climatic pattern that strongly influences the atmospheric circulation in the northern Hemisphere and by consequence the long-term variability of marine and terrestrial ecosystem over great part of northern Europe and western Mediterranean. In the Mediterranean, the effects of the NAO on vertebrates has been studied mainly on bird populations but was rarely analysed in ectothermic animals, and in particular in amphibians. In this study, we investigated the relationships between winter, spring and summer NAO indexes and the long-term population dynamics of the plethodontid salamander Speleomantes strinatii. This terrestrial salamander was monitored inside an artificial cave in NW Italy for 24 consecutive years. The relationships between seasonal NAO indexes and the salamander dynamics were assessed by cross-correlation function (CCF) analysis, after prewhitening the time series by autoregressive moving average statistical modelling. Results of CCF analyses indicated that the salamander abundance varied in relation to the one-year ahead winter NAO ( P = 0.018), while no relationships were found with spring and summer indexes. These results strengthen some previous findings that suggested a high sensitivity of temperate terrestrial amphibians to wintertime climatic conditions.

  19. Seasonal assemblages and short-lived blooms in coastal north-west Atlantic Ocean bacterioplankton.

    PubMed

    El-Swais, Heba; Dunn, Katherine A; Bielawski, Joseph P; Li, William K W; Walsh, David A

    2015-10-01

    Temperate oceans are inhabited by diverse and temporally dynamic bacterioplankton communities. However, the role of the environment, resources and phytoplankton dynamics in shaping marine bacterioplankton communities at different time scales remains poorly constrained. Here, we combined time series observations (time scales of weeks to years) with molecular analysis of formalin-fixed samples from a coastal inlet of the north-west Atlantic Ocean to show that a combination of temperature, nitrate, small phytoplankton and Synechococcus abundances are best predictors for annual bacterioplankton community variability, explaining 38% of the variation. Using Bayesian mixed modelling, we identified assemblages of co-occurring bacteria associated with different seasonal periods, including the spring bloom (e.g. Polaribacter, Ulvibacter, Alteromonadales and ARCTIC96B-16) and the autumn bloom (e.g. OM42, OM25, OM38 and Arctic96A-1 clades of Alphaproteobacteria, and SAR86, OM60 and SAR92 clades of Gammaproteobacteria). Community variability over spring bloom development was best explained by silicate (32%)--an indication of rapid succession of bacterial taxa in response to diatom biomass--while nanophytoplankton as well as picophytoplankton abundance explained community variability (16-27%) over the transition into and out of the autumn bloom. Moreover, the seasonal structure was punctuated with short-lived blooms of rare bacteria including the KSA-1 clade of Sphingobacteria related to aromatic hydrocarbon-degrading bacteria.

  20. Characteristics of gunshot sound displays by North Atlantic right whales in the Bay of Fundy.

    PubMed

    Parks, Susan E; Hotchkin, Cara F; Cortopassi, Kathryn A; Clark, Christopher W

    2012-04-01

    North Atlantic right whales (Eubalaena glacialis) produce a loud, broadband signal referred to as the gunshot sound. These distinctive sounds may be suitable for passive acoustic monitoring and detection of right whales; however, little is known about the prevalence of these sounds in important right whale habitats, such as the Bay of Fundy. This study investigates the timing and distribution of gunshot sound production on the summer feeding grounds using an array of five marine acoustic recording units deployed in the Bay of Fundy, Canada in mid-summer 2004 and 2005. Gunshot sounds were common, detected on 37 of 38 recording days. Stereotyped gunshot bouts averaged 1.5 h, with some bouts exceeding 7 h in duration with up to seven individuals producing gunshots at any one time. Bouts were more commonly detected in the late afternoon and evening than during the morning hours. Locations of gunshots in bouts indicated that whales producing the sounds were either stationary or showed directional travel, suggesting gunshots have different communication functions depending on behavioral context. These results indicate that gunshots are a common right whale sound produced during the summer months and are an important component in the acoustic communication system of this endangered species.

  1. Open ocean dead-zone 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.

    2014-12-01

    The intermittent appearances of low oxygen environments are a particular thread for marine ecosystems. Here we present first observations of unexpected low (<2 μmol kg-1) oxygen environments in the open waters of the eastern tropical North Atlantic, a region where typically oxygen concentration does not fall below 40 μmol kg-1. The low oxygen zones are created just below the mixed-layer, in the euphotic zone of high productive cyclonic and anticyclonic-modewater eddies. A dynamic boundary is created from the large swirl-velocity against the weak background flow. Hydrographic properties within the eddies are kept constant over periods of several months, while net respiration is elevated by a factor of 3 to 5 reducing the oxygen content. We repeatedly observed low oxygen eddies in the region. The direct impact on the ecosystem is evident from anomalous backscatter behaviour. Satellite derived global eddy statistics do not allow to estimate the large-scale impact of the eddies because their vertical structure (mixed-layer depth, euphotic depth) play a key role in creating the low oxygen environment.

  2. Oceanographic dynamics and the end of the last interglacial in the subpolar North Atlantic.

    PubMed

    Mokeddem, Zohra; McManus, Jerry F; Oppo, Delia W

    2014-08-01

    The last interglacial interval was terminated by the inception of a long, progressive glaciation that is attributed to astronomically influenced changes in the seasonal distribution of sunlight over the earth. However, the feedbacks, internal dynamics, and global teleconnections associated with declining northern summer insolation remain incompletely understood. Here we show that a crucial early step in glacial inception involves the weakening of the subpolar gyre (SPG) circulation of the North Atlantic Ocean. Detailed new records of microfossil foraminifera abundance and stable isotope ratios in deep sea sediments from Ocean Drilling Program site 984 south of Iceland reveal repeated, progressive cold water-mass expansions into subpolar latitudes during the last peak interglacial interval, marine isotope substage 5e. These movements are expressed as a sequence of progressively extensive southward advances and subsequent retreats of a hydrographic boundary that may have been analogous to the modern Arctic front, and associated with rapid changes in the strength of the SPG. This persistent millennial-scale oceanographic oscillation accompanied a long-term cooling trend at a time of slowly declining northern summer insolation, providing an early link in the propagation of those insolation changes globally, and resulting in a rapid transition from extensive regional warmth to the dramatic instability of the subsequent ∼ 100 ka. PMID:25049405

  3. [Demographic analysis of the blue shark, Prionace glauca, in the North Atlantic Ocean].

    PubMed

    Gao, Chun-xia; Dai, Xiao-jie; Tian, Si-quan; Wu, Feng; Zhu, Jiang-feng

    2016-02-01

    The blue shark, Prionace glauca, is the main by-catch species in tuna longline fishery. As one of top species in the oceanic food webs, the blue shark plays an important role in the marine ecosystem. Traditional stock assessment methods are difficult to accurately evaluate the population dynamic for this shark because of limited data. Based on life-history parameters of the blue shark in the North Atlantic, demographic analysis was employed to estimate the demographic parameters and evaluate the potential exploitation for the blue shark. Moreover, we discussed the relationship between age at first capture and critical value of fishing mortality corresponding to the value of intrinsic rate of natural increase 0. The results showed that the survival rate (S) of blue shark from 0.719 to 0.820, intrinsic rate of natural increase (r0) from 0.250 to 0.381, time of population doubling (tx2) from 1.819 to 2.773 years, reproduction rate per generation (R0) from 6.600 to 22.255, and generation time (G) from 8.498 to 10.162 years. The sensitivity analysis for the life history parameters revealed that the uncertainties of natural mortality existed in the first age class, age at maturity and maximum age had slight influence on the demographic parameters. Fishing mortality (Fc) increased with the age at first capture. When the age at first capture (tc) was more than five, there was no obvious relationship between Fc and tc.

  4. New Invertebrate Vectors for PST, Spirolides and Okadaic Acid in the North Atlantic

    PubMed Central

    Silva, Marisa; Barreiro, Aldo; Rodriguez, Paula; Otero, Paz; Azevedo, Joana; Alfonso, Amparo; Botana, Luis M.; Vasconcelos, Vitor

    2013-01-01

    The prevalence of poisoning events due to harmful algal blooms (HABs) has declined during the last two decades through monitoring programs and legislation, implemented mainly for bivalves. However, new toxin vectors and emergent toxins pose a challenge to public health. Several locations on the Portuguese coast were surveyed between 2009 and 2010 for three distinct biotoxin groups [saxitoxin (PST), spirolide (SPX) and okadaic acid (OA)], in 14 benthic species of mollusks and echinoderms. Our main goals were to detect new vectors and unravel the seasonal and geographical patterns of these toxins. PSTs were analyzed by the Lawrence method, SPXs by LC-MS/MS, and OA by LC-MS/MS and UPLC-MS/MS. We report 16 new vectors for these toxins in the North Atlantic. There were differences in toxin contents among species, but no significant geographical or seasonal patterns were found. Our results suggest that legislation should be adjusted to extend the monitoring of marine toxins to a wider range of species besides edible bivalves. PMID:23739043

  5. Sources and sinks of acetone, methanol, and acetaldehyde in North Atlantic air

    NASA Astrophysics Data System (ADS)

    Lewis, A. C.; Hopkins, J. R.; Carpenter, L. J.; Stanton, J.; Read, K. A.; Pilling, M. J.

    2005-03-01

    Measurements of acetone, methanol, acetaldehyde and a range of non-methane hydrocarbons have been made in North Atlantic marine air at the Mace Head observatory. Under maritime conditions the combination of OVOCs (acetone, methanol and 5 acetaldehyde) contributed up to 85% of the total mass of measured non methane organics in air and up to 80% of the OH radical organic sink, when compared with the sum of all other organic compounds including non-methane hydrocarbons, DMS and OH-reactive halocarbons (trichloromethane and tetrachloroethylene). The observations showed anomalies in the variance and abundance of acetaldehyde and acetone 10 over that expected for species with a remote terrestrial emission source and OH controlled chemical lifetime. A detailed model incorporating an explicit chemical degradation mechanism indicated in situ formation during air mass transport was on timescales longer than the atmospheric lifetime of precursor hydrocarbons or primary emission. The period over which this process was significant was similar to that of airmass mo15 tion on intercontinental scales, and formation via this route may reproduce that of a widespread diffuse source. The model indicates that continued short chain OVOC formation occurs many days from the point of emission, via longer lived intermediates of oxidation such as organic peroxides and long chain alcohols.

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

    PubMed

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

    2016-06-21

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

  7. 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.

  8. Gaidropsarus (Gadidae, Teleostei) of the North Atlantic Ocean: a brief phylogenetic review.

    PubMed

    Francisco, S M; Robalo, J I; Stefanni, S; Levy, A; Almada, V C

    2014-08-01

    The phylogenetic relationships among the North Atlantic Gaidropsarus and between the three Gaidropsarinae genera Gaidropsarus, Ciliata and Enchelyopus are reviewed with the hitherto most comprehensive taxonomic sampling of this group. Phylogenetic results (maximum parsimony, maximum likelihood and Bayesian inference) based on nuclear (rhodopsin) and concatenated mitochondrial (12s, 16s and cytb) markers clearly support this subfamily. For the north-eastern Atlantic species of Gaidropsarus, two previously unreported clades were strongly supported, clarifying the relationships within the genus, and revealing fewer distinct taxa in the north Atlantic Gaidropsarus than previously stipulated. The data challenge the specific status of Gaidropsarus mediterraneus and Gaidropsarus guttatus and raise doubts concerning the distinctiveness of other species. A taxonomic revision of the genus is suggested. PMID:24961593

  9. 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.

  10. 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.

  11. Impact of abrupt climate change in the tropical southeast Atlantic during Marine Isotope Stage (MIS) 3

    NASA Astrophysics Data System (ADS)

    Hessler, Ines; Steinke, Stephan; Groeneveld, Jeroen; Dupont, Lydie; Wefer, Gerold

    2011-12-01

    High resolution planktonic foraminifera Mg/Ca paleotemperatures and oxygen isotopes of seawater of Ocean Drilling Program (ODP) Site 1078 (off Angola) have been reconstructed and reveal insights into the seasonal thermal evolution of the Angola Current (AC), the Angola-Benguela Front (ABF), and the Benguela Current (BC) during the last glacial (50-23.5 ka BP). Special emphasis is put on time intervals possibly associated with the North Atlantic Heinrich Stadials (HS), which are thought to lead to an accumulation of heat in the South Atlantic due to a reduction of the Atlantic Meridional Overturning Circulation (AMOC). Within dating uncertainties, Globigerinoides ruber (pink) Mg/Ca-based sea surface temperature (SST) estimates that represent southern hemisphere summer surface conditions show several warming episodes that coincide with North Atlantic HS, thus supporting the concept of the bipolar thermal seesaw. In contrast, the Mg/Ca-based temperatures of Globigerina bulloides, representing the SST of the ABF/BC system during southern hemisphere winter, show no obvious response to the North Atlantic HS in the study area. We suggest that surface water cooling during the winter season is due to enhanced upwelling or upwelling of colder water masses which has most likely mitigated a warming of the ABF/BC system during HS. We further speculate that the seasonal asymmetry in our SST record results from seasonal differences in the dominance of atmospheric and oceanic teleconnections during periods of northern high latitude cooling.

  12. Effect of abyssal circulation changes on Oligocene to Miocene benthic foraminifera in the North Atlantic

    SciTech Connect

    Katz, M.E.; Miller, K.G.

    1985-01-01

    Benthic foraminiferal ranges at western North Atlantic Sites 563 and 558 show: 1) gradual Oligocene last occurrences in response to subsidence from the upper to lower abyssal zones; 2) a preponderance of extinctions in the early middle Miocene (about 15.5-13.5 Ma). Comparison of relative and absolute abundance changes at Site 563 sows that percentages of some taxa (e.g. Nuttallides umbonifera) reliably reflect their accumulations while percentages of others vary independently. Regional abundance changes include: 1) maxima N. umbonifera in the middle Oligocene of the deepest sites (10 and 119); 2) increased Planulina wuellerstorfi in the early middle Miocene; 3) increased N. umbonifera in the late middle Miocene. Seismic stratigraphic and delta/sup 13/C evidence indicates a northern bottom-water source for the North Atlantic throughout much of the Oligocene and Miocene. Benthic foraminifera apparently responded to bottom-water changes inferred from carbon isotopic comparisons. The extinction of relict Paleogene taxa and the ascendancy of P. wuellerstorfi in the middle Miocene apparently correlate with increased advection into the eastern Atlantic, subsidence of the Iceland-Faeroe Ridge and increased North Atlantic carbonate sedimentation. The authors speculate that this faunal reorganization was in response to global ocean chemistry changes resulting from increased ventilation of the North Atlantic.

  13. 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.

  14. Radon daughter disequilibria and lead systematics in the western North Atlantic

    NASA Astrophysics Data System (ADS)

    Hussain, N.; Church, T. M.; VéRon, Alain J.; Larson, R. E.

    1998-01-01

    Concentrations of 222Rn and 210Pb were measured in the North Atlantic troposphere in 1989 between April 12 and 28, during the Sulfide Experiment (SEX) Cruise I, and those of 222Rn, 210Pb and 210Po, between October 24 and November 9, during the SEX Cruise II. Concentrations of 210Pb and 210Po were also measured in the rain water, surface seawater, and marine microlayer collected during the SEX Cruise II Other data used and published previously include stable lead and its isotopes [Vèron et al., 1992, 1993] on parallel samples. Low 222Rn contents, of the order of 0.1 and 0.3 Bq m-3, were found in the marine air, while continental air showed nearly 10 times higher concentrations of 222Rn. These results corroborate with the air mass trajectory analyses and continental signatures of stable lead isotopes. Significant correlation is found between 222Rn and 210Pb on the aerosol, indicative of excess continental 222Rn supporting the ingrowth of 210Pb from the atmosphere, in spite of its first-order removal by precipitation. Correlation between 210Pb and stable Pb on the aerosol and in the precipitation document the source of pollutant lead from the continental surface. Mean residence times of marine aerosol based on 210Pb is estimated to be 5.4±1.8 days during the April cruise and 19.7±1.9 days during the October cause. Corresponding deposition velocity for 210Pb is estimated to be 1.9±1.9 cm s-1, a value that suggests the dominant role of precipitation scavenging, or aerosol scavenging by larger host phases such as dust or sea salt. Excess 210Po activities are found on the aerosol relative to what would be expected based on 210Pb and the aerosol residence times. In surface seawaters, deficiencies of 210Po are observed. Mechanisms of 210Po enrichment in atmospheric aerosol may include enrichments from the organic components of marine microlayer, sea-salt aerosol, dust, or air-sea exchange of volatile organo-polonium species.

  15. North Atlantic warming during Dansgaard-Oeschger events synchronous with Antarctic warming and out-of-phase with Greenland climate.

    PubMed

    Rasmussen, Tine L; Thomsen, Erik; Moros, Matthias

    2016-01-01

    The precise reason for the differences and out-of-phase relationship between the abrupt Dansgaard-Oeschger warmings in the Nordic seas and Greenland ice cores and the gradual warmings in the south-central Atlantic and Antarctic ice cores is poorly understood. Termed the bipolar seesaw, the differences are apparently linked to perturbations in the ocean circulation pattern. Here we show that surface and intermediate-depth water south of Iceland warmed gradually synchronously with the Antarctic warming and out of phase with the abrupt warming of the Nordic seas and over Greenland. The hinge line between areas showing abrupt and gradual warming was close to the Greenland-Scotland Ridge and the marine system appears to be a 'push-and-pull' system rather than a seesaw system. 'Pull' during the warm interstadials, when convection in the Nordic seas was active; 'push' during the cold stadials, when convection stopped and warm water from the south-central Atlantic pushed northward gradually warming the North Atlantic and Nordic seas. PMID:26847384

  16. North Atlantic warming during Dansgaard-Oeschger events synchronous with Antarctic warming and out-of-phase with Greenland climate

    PubMed Central

    Rasmussen, Tine L.; Thomsen, Erik; Moros, Matthias

    2016-01-01

    The precise reason for the differences and out-of-phase relationship between the abrupt Dansgaard-Oeschger warmings in the Nordic seas and Greenland ice cores and the gradual warmings in the south-central Atlantic and Antarctic ice cores is poorly understood. Termed the bipolar seesaw, the differences are apparently linked to perturbations in the ocean circulation pattern. Here we show that surface and intermediate-depth water south of Iceland warmed gradually synchronously with the Antarctic warming and out of phase with the abrupt warming of the Nordic seas and over Greenland. The hinge line between areas showing abrupt and gradual warming was close to the Greenland-Scotland Ridge and the marine system appears to be a ‘push-and-pull’ system rather than a seesaw system. ‘Pull’ during the warm interstadials, when convection in the Nordic seas was active; ‘push’ during the cold stadials, when convection stopped and warm water from the south-central Atlantic pushed northward gradually warming the North Atlantic and Nordic seas. PMID:26847384

  17. North Atlantic warming during Dansgaard-Oeschger events synchronous with Antarctic warming and out-of-phase with Greenland climate

    NASA Astrophysics Data System (ADS)

    Rasmussen, Tine L.; Thomsen, Erik; Moros, Matthias

    2016-02-01

    The precise reason for the differences and out-of-phase relationship between the abrupt Dansgaard-Oeschger warmings in the Nordic seas and Greenland ice cores and the gradual warmings in the south-central Atlantic and Antarctic ice cores is poorly understood. Termed the bipolar seesaw, the differences are apparently linked to perturbations in the ocean circulation pattern. Here we show that surface and intermediate-depth water south of Iceland warmed gradually synchronously with the Antarctic warming and out of phase with the abrupt warming of the Nordic seas and over Greenland. The hinge line between areas showing abrupt and gradual warming was close to the Greenland-Scotland Ridge and the marine system appears to be a ‘push-and-pull’ system rather than a seesaw system. ‘Pull’ during the warm interstadials, when convection in the Nordic seas was active; ‘push’ during the cold stadials, when convection stopped and warm water from the south-central Atlantic pushed northward gradually warming the North Atlantic and Nordic seas.

  18. Atlantic Multidecadal Oscillation (AMO) modulates dynamics of small pelagic fishes and ecosystem regime shifts in the eastern North and Central Atlantic

    NASA Astrophysics Data System (ADS)

    Alheit, Jürgen; Licandro, Priscilla; Coombs, Steve; Garcia, Alberto; Giráldez, Ana; Santamaría, Maria Teresa Garcia; Slotte, Aril; Tsikliras, Athanassios C.

    2014-03-01

    Dynamics of abundance and migrations of populations of small pelagic clupeoid fish such as anchovy (Engraulis encrasicolus), sardine (Sardina pilchardus), sardinella (Sardinella aurita), sprat (Sprattus sprattus) and herring (Clupea harengus) in the eastern North and Central Atlantic between Senegal and Norway vary in synchrony with the warm and cool phases of the Atlantic Multidecadal Oscillation (AMO). This is shown by compiling retrospective data on fish catches and anecdotal observations, which in some cases date back to the mid-19th century. The AMO is defined as the de-trended mean of North Atlantic (0-60°N) sea surface temperature anomalies. However, it is not primarily the temperature which drives the dynamics of the small pelagic fish populations. Instead, the AMO seems to be a proxy for complex processes in the coupled atmosphere-ocean system of the North Atlantic. This is manifested in large-scale changes in strength and direction of the current system that move water masses around the North Atlantic and likely involves the North Atlantic Oscillation (NAO), the Atlantic Meridional Overturning Circulation (AMOC), the Mediterranean Overflow Water (MOW) and the subpolar gyre (SPG). The contractions and expansions of the SPG apparently play a key role. This was particularly obvious in the mid-1990s, when the SPG abruptly contracted with the result that warm subtropical water masses moved to the north and east. Small pelagic fish populations in the eastern North and Central Atlantic, including those in the Mediterranean responded quickly by changing abundances and migrating northwards. It seems that the complex ocean-atmosphere changes in the mid-1990s, which are described in the text in detail, caused a regime shift in the ecosystems of the eastern North and Central Atlantic and the small pelagic clupeoid fish populations are the sentinels of this shift.

  19. Drivers of diel and regional variations of halocarbon emissions from the tropical North East Atlantic

    NASA Astrophysics Data System (ADS)

    Hepach, H.; Quack, B.; Ziska, F.; Fuhlbrügge, S.; Atlas, E. L.; Krüger, K.; Peeken, I.; Wallace, D. W. R.

    2014-02-01

    Methyl iodide (CH3I), bromoform (CHBr3) and dibromomethane (CH2Br2), which are produced naturally in the oceans, take part in ozone chemistry both in the troposphere and the stratosphere. The significance of oceanic upwelling regions for emissions of these trace gases in the global context is still uncertain although they have been identified as important source regions. To better quantify the role of upwelling areas in current and future climate, this paper analyzes major factors that influenced halocarbon emissions from the tropical North East Atlantic including the Mauritanian upwelling during the DRIVE expedition. Diel and regional variability of oceanic and atmospheric CH3I, CHBr3 and CH2Br2 was determined along with biological and physical parameters at six 24 h-stations. Low oceanic concentrations of CH3I from 0.1-5.4 pmol L-1 were equally distributed throughout the investigation area. CHBr3 and CH2Br2 from 1.0 to 42.4 pmol L-1 and to 9.4 pmol L-1, respectively were measured with maximum concentrations close to the Mauritanian coast. Atmospheric CH3I, CHBr3, and CH2Br2 of up to 3.3, 8.9, and 3.1 ppt, respectively were detected above the upwelling, as well as up to 1.8, 12.8, and 2.2 ppt at the Cape Verdean coast. While diel variability in CH3I emissions could be mainly ascribed to oceanic non-biological production, no main driver was identified for its emissions over the entire study region. In contrast, biological parameters showed the greatest influence on the regional distribution of sea-to-air fluxes of bromocarbons. The diel impact of wind speed on bromocarbon emissions increased with decreasing distance to the coast. The height of the marine atmospheric boundary layer (MABL) influenced halocarbon emissions via its influence on atmospheric mixing ratios. Oceanic and atmospheric halocarbons correlated well in the study region, and in combination with high oceanic CH3I, CHBr3 and CH2Br2 concentrations, local hot spots of atmospheric halocarbons could

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

    USGS Publications Warehouse

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

    2005-01-01

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

  1. 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

  2. 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.

  3. 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

  4. Recruitment Variability in North Atlantic Cod and Match-Mismatch Dynamics

    PubMed Central

    Kristiansen, Trond; Drinkwater, Kenneth F.; Lough, R. Gregory; Sundby, Svein

    2011-01-01

    Background Fisheries exploitation, habitat destruction, and climate are important drivers of variability in recruitment success. Understanding variability in recruitment can reveal mechanisms behind widespread decline in the abundance of key species in marine and terrestrial ecosystems. For fish populations, the match-mismatch theory hypothesizes that successful recruitment is a function of the timing and duration of larval fish abundance and prey availability. However, the underlying mechanisms of match-mismatch dynamics and the factors driving spatial differences between high and low recruitment remain poorly understood. Methodology/Principal Findings We used empirical observations of larval fish abundance, a mechanistic individual-based model, and a reanalysis of ocean temperature data from 1960 to 2002 to estimate the survival of larval cod (Gadus morhua). From the model, we quantified how survival rates changed during the warmest and coldest years at four important cod spawning sites in the North Atlantic. The modeled difference in survival probability was not large for any given month between cold or warm years. However, the cumulative effect of higher growth rates and survival through the entire spawning season in warm years was substantial with 308%, 385%, 154%, and 175% increases in survival for Georges Bank, Iceland, North Sea, and Lofoten cod stocks, respectively. We also found that the importance of match-mismatch dynamics generally increased with latitude. Conclusions/Significance Our analyses indicate that a key factor for enhancing survival is the duration of the overlap between larval and prey abundance and not the actual timing of the peak abundance. During warm years, the duration of the overlap between larval fish and their prey is prolonged due to an early onset of the spring bloom. This prolonged season enhances cumulative growth and survival, leading to a greater number of large individuals with enhanced potential for survival to recruitment

  5. Regime shifts in the Arctic North Atlantic during the Neoglacial revealed by seabirds and precipitation isotopes on Bjørnøya, Svalbard

    NASA Astrophysics Data System (ADS)

    D'Andrea, William J.; Hormes, Anne; Bakke, Jostein; Nicolaisen, Line

    2016-04-01

    The northeastern North Atlantic Ocean, and the Norwegian and Greenland Seas are subject to large hydrographic changes. These variations can influence oceanic heat transport to the Arctic, meridional overturning circulation, and atmospheric circulation patterns and thereby impact global climate patterns. Marine records suggest that numerous large-scale changes in the hydrography of the northern North Atlantic took place during the middle to late Holocene. We report a record of nitrogen and hydrogen isotope measurements from a lake sediment core from Bjørnøya, Svalbard (74.38°N, 19.02°E) that documents major regime shifts in the climate of the northern North Atlantic during the past 6,000 years. Bjørnøya is the nesting ground for one of the largest seabird populations in the North Atlantic. As top predators in the marine ecosystem, seabirds (and their guano) are enriched in 15N; during spring and summer months they deliver isotopically enriched nitrogen to nesting areas. We developed a record of seabird population changes on Bjørnøya based on the nitrogen isotope composition of sediments in a core collected from lake Ellasjøen. The record reveals multiple multicentennial scale changes in δ15N values (varying between ~8-12‰) that track past changes in the size of seabird populations. From the same sediment core, we also developed a record of δD of precipitation, using δD values of sedimentary n-alkanes. Past intervals with the largest inferred bird populations correspond with the most enriched δD of precipitation, which we interpret to represent a more Atlantic climate. Periods with reduced seabird populations correspond with intervals with more negative δD of precipitation and representing a more Arctic climate. Together, the nitrogen and hydrogen isotope records signify regime shifts in the oceanography, marine ecosystem, and atmospheric circulation of the northern North Atlantic that are related to variations in the strength of the subpolar gyre.

  6. 75 FR 57407 - Atlantic Highly Migratory Species; North and South Atlantic Swordfish Quotas

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-21

    ... fishing for swordfish in the Atlantic Ocean, including the Caribbean Sea and Gulf of Mexico, by... specific measures laid out in the proposed rule can be found in 75 FR 35432 (June 22, 2010) and are...

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

    PubMed

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

    2004-10-26

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

  8. 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.

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

    PubMed Central

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

    2004-01-01

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

  10. Invasion by a Japanese marine microorganism in western North America

    USGS Publications Warehouse

    McGann, M.; Sloan, D.; Cohen, A.N.

    2000-01-01

    The earliest record in western North America of Trochammina hadai Uchio, a benthic foraminifer common in Japanese estuaries, is from sediment collected in Puget Sound in 1971. It was first found in San Francisco Bay in sediment samples taken in 1983, and since 1986 has been collected at 91% of the sampled sites in the Bay, constituting up to 93% of the foraminiferal assemblage at individual sites. The species is also present in recent sediment samples from 12 other sites along the west coast of North America. The evidence indicates that T. hadai is a recent introduction to San Francisco Bay, and is probably also not native to the other North American sites. Trochammina hadai was probably transported from Japan in ships' ballast tanks, in mud associated with anchors, or in sediments associated with oysters imported for mariculture. Its remarkable invasion of San Francisco Bay suggests the potential for massive, rapid invasions by other marine microorganisms.

  11. Elemental ratios and enrichment factors in aerosols from the US-GEOTRACES North Atlantic transects

    NASA Astrophysics Data System (ADS)

    Shelley, Rachel U.; Morton, Peter L.; Landing, William M.

    2015-06-01

    The North Atlantic receives the highest aerosol (dust) input of all the oceanic basins. Dust deposition provides essential bioactive elements, as well as pollution-derived elements, to the surface ocean. The arid regions of North Africa are the predominant source of dust to the North Atlantic Ocean. In this study, we describe the elemental composition (Li, Na, Mg, Al, P, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Cd, Sn, Sb, Cs, Ba, La, Ce, Nd, Pb, Th, U) of the bulk aerosol from samples collected during the US-GEOTRACES North Atlantic Zonal Transect (2010/11) in order to highlight the differences between a Saharan dust end-member and the reported elemental composition of the upper continental crust (UCC), and the implications this has for identifying trace element enrichment in aerosols across the North Atlantic basin. As aerosol titanium (Ti) is less soluble than aerosol aluminum (Al), it is a more conservative tracer for lithogenic aerosols and trace element-to-Ti ratios. However, the presence of Ti-rich fine aerosols can confound the interpretation of elemental enrichments, making Al a more robust tracer of aerosol lithogenic material in this region.

  12. Molecular cloning and characterization of five opsin genes from the marine flatfish Atlantic halibut (Hippoglossus hippoglossus).

    PubMed

    Helvik, J V; Drivenes, O; Naess, T H; Fjose, A; Seo, H C

    2001-01-01

    Most molecular studies on the visual system in fish have been performed on freshwater teleosts such as goldfish and zebrafish where cones and rods appear simultaneously. Many marine fishes have long larval phase in the upper pelagic zone before transformation into a juvenile and a benthic life style. The retina at the larval stages consists of only single cone cells; later during metamorphosis double cones and rods develop. The flatfish Atlantic halibut (Hippoglossus hippoglossus) is a typical example of a marine species with such a two-step retina development. In this study, we have cloned five different opsins from Atlantic halibut larvae and juvenile retinas. Sequence comparisons with other opsins and phylogenetic analysis show that the five genes belong to the opsins of long-wavelength sensitive (L); middle-wavelength sensitive, M(Cone) and M(Rod); and short-wavelength sensitive, S(Blue) and S(Ultraviolet), respectively. In situ hybridization analysis reveals expression in double cone (L and M(Cone)), single cone (S(Blue) and S(Ultraviolet)), and rod (M(Rod)) types of photoreceptor cells in juvenile halibut retina. The visual system in Atlantic halibut seems therefore to have all four types of cone photoreceptors in addition to rod photoreceptors. This work shows for the first time molecular isolation of a complete set of retinal visual pigment genes from a marine teleost and describes the first cloning of an ultraviolet-sensitive opsin type from a marine teleost.

  13. 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

  14. Modeling ozone plumes observed downwind of New York City over the North Atlantic Ocean during the ICARTT field campaign

    NASA Astrophysics Data System (ADS)

    Lee, S.-H.; Kim, S.-W.; Trainer, M.; Frost, G. J.; McKeen, S. A.; Cooper, O. R.; Flocke, F.; Holloway, J. S.; Neuman, J. A.; Ryerson, T.; Senff, C. J.; Swanson, A. L.; Thompson, A. M.

    2011-07-01

    Transport and chemical transformation of well-defined New York City (NYC) urban plumes over the North Atlantic Ocean were studied using aircraft measurements collected on 20-21 July 2004 during the ICARTT (International Consortium for Atmospheric Research on Transport and Transformation) field campaign and WRF-Chem (Weather Research and Forecasting-Chemistry) model simulations. The strong NYC urban plumes were characterized by carbon monoxide (CO) mixing ratios of 350-400 parts per billion by volume (ppbv) and ozone (O3) levels of about 100 ppbv near New York City on 20 July in the WP-3D in-situ and DC-3 lidar aircraft measurements. On 21 July, the two aircraft captured strong urban plumes with about 350 ppbv CO and over 150 ppbv O3 (~160 ppbv maximum) about 600 km downwind of NYC over the North Atlantic Ocean. The measured urban plumes extended vertically up to about 2 km near New York City, but shrank to 1-1.5 km over the stable marine boundary layer (MBL) over the North Atlantic Ocean. The WRF-Chem model reproduced ozone formation processes, chemical characteristics, and meteorology of the measured urban plumes near New York City (20 July) and in the far downwind region over the North Atlantic Ocean (21 July). The quasi-Lagrangian analysis of transport and chemical transformation of the simulated NYC urban plumes using WRF-Chem results showed that the pollutants can be efficiently transported in (isentropic) layers in the lower atmosphere (<2-3 km) over the North Atlantic Ocean while maintaining a dynamic vertical decoupling by cessation of turbulence in the stable MBL. The O3 mixing ratio in the NYC urban plumes remained at 80-90 ppbv during nocturnal transport over the stable MBL, then grew to over 100 ppbv by daytime oxidation of nitrogen oxides (NOx = NO + NO2) with mixing ratios on the order of 1 ppbv. Efficient transport of reactive nitrogen species (NOy), specifically nitric acid (HNO3), was confirmed through the comparison of the CO/NOy ratio in

  15. Modeling ozone plumes observed downwind of New York City over the North Atlantic Ocean during the ICARTT field campaign

    NASA Astrophysics Data System (ADS)

    Lee, S.-H.; Kim, S.-W.; Trainer, M.; Frost, G. J.; McKeen, S. A.; Cooper, O. R.; Flocke, F.; Holloway, J. S.; Neuman, J. A.; Ryerson, T.; Senff, C. J.; Swanson, A. L.; Thompson, A. M.

    2011-05-01

    Transport and chemical transformation of well-defined New York City (NYC) urban plumes over the North Atlantic Ocean were studied using aircraft measurements collected on 20-21 July 2004 during the ICARTT (International Consortium for Atmospheric Research on Transport and Transformation) field campaign and WRF-Chem (Weather Research and Forecasting-Chemistry) model simulations. The strong NYC urban plumes were characterized by carbon monoxide (CO) mixing ratios of 350-400 parts per billion by volume (ppbv) and ozone (O3) levels of about 100 ppbv near New York City on 20 July in the WP-3D in-situ and DC-3 lidar aircraft measurements. On 21 July, the two aircraft captured strong urban plumes with about 350 ppbv CO and over 150 ppbv O3 (~160 ppbv maximum) about 600 km downwind of NYC over the North Atlantic Ocean. The measured urban plumes extended vertically up to about 2 km near New York City, but shrank to 1-1.5 km over the stable marine boundary layer (MBL) over the North Atlantic Ocean. The WRF-Chem model reproduced ozone formation processes, chemical characteristics, and meteorology of the measured urban plumes near New York City (20 July) and in the far downwind region over the North Atlantic Ocean (21 July). The quasi-Lagrangian analysis of transport and chemical transformation of the simulated NYC urban plumes using WRF-Chem results showed that the pollutants can be efficiently transported in (isentropic) layers in the lower atmosphere (<2-3 km) over the North Atlantic Ocean while maintaining a dynamic vertical decoupling by cessation of turbulence in the stable MBL. The O3 mixing ratio in the NYC urban plumes remained at 80-90 ppbv during nocturnal transport over the stable MBL, then grew to over 100 ppbv by daytime oxidation of nitrogen oxides (NOx = NO + NO2) with mixing ratios on the order of 1 ppbv. Efficient transport of reactive nitrogen species (NOy), specifically nitric acid (HNO3), was confirmed through the comparison of the CO/NOy ratio in

  16. Measurements of dimethyl sulfide and H2S over the western North Atlantic and the tropical Atlantic

    NASA Technical Reports Server (NTRS)

    Andreae, T. W.; Andreae, M. O.; Bingemer, H. G.; Leck, C.

    1993-01-01

    Airborne measurements of DMS and H2S were made off the east coast of the United States and over the tropical Atlantic off Brazil. Samples were collected through a fluorinated ethylene propylene Teflon inlet manifold. Dimethyl sulfide (DMS) was preconcentrated onto gold wool and analyzed by gas chromatography/flame photometric detection. H2S was collected on AgNO3-impregnated filters and determined by fluorescence quenching. Use of a new scrubber material (cotton) to remove negative interference on DMS measurements was investigated. Comparison with a Na2CO3/Anakrom scrubber gave good overall agreement. Only under extreme conditions, e.g., on flight 9 (continental air mass, low humidity, high O3, and low DMS values) did Na2CO3 show noticeable loss of DMS compared to cotton. On most flights, especially in marine air masses with high humidity and relatively low O3, the results from both scrubbers agreed well with each other and with other instruments used during the intercalibration. Off the U.S. East Coast, DMS levels showed strong dependence on air mass origin with high values (up to 83 ppt) in marine tropical air masses and low values (10-20 ppt) in continental and polar air. Over the tropical Atlantic, DMS ranged over 20-100 ppt in the mixed layer. Nighttime values were a factor of 1.6-2.3 higher than daytime levels. DMS decreased with altitude to less than 1 ppt at 4000 m. H2S in the mixed layer off the U.S. East Coast ranged from 10 to 200 ppt. Significant influence from terrestrial and pollution sources was evident. H2S in air masses originating over the eastern seaboard was much higher than in continental polar air or over the remote tropical continents. In contrast, over the tropical Atlantic, concentrations were very low (5-10 ppt), typical of truly marine air. Night/day ratios were about 1.4. No significant geographical variability was seen in H2S levels over the tropical Atlantic. The correlation of atmospheric Rn-222 and H2S was significant, with both

  17. Introduced marine species of the North Sea coasts

    NASA Astrophysics Data System (ADS)

    Reise, K.; Gollasch, S.; Wolff, W. J.

    1998-09-01

    About 80 non-indigenous species are assumed to have been introduced into the North Sea by transoceanic shipping and aquaculture. The number is certainly underestimated as most small organisms received insufficient attention at the species level. Also, the seafaring tradition of the North Sea countries is much longer than our biological surveys are. Most exotic invertebrates originate from the western Atlantic and were introduced by shipping, while most algae stem from the Pacific and came with the introduced oysters. A peak of newcomers was observed in the 1970s. Most of the arrivals became established in brackish environments, at harbor sites and in the vicinity of oyster farms, fouling on hard substrates or living as epibionts. A few live in sediments, are holoplanktonic or are parasites. At the open coast, approximately 6% of the macrobenthic species are exotics, while in estuaries their share is up to 20%. Most exotics have been encountered in the southern North Sea first, and many did not spread further north. About 25% of the established non-natives are widespread and attain locally high abundances. As a consequence, some inshore habitats are entirely dominated by exotics. The overall effect on the ecosystem seems to be more additive than one of displacement. This suggests that the coastal biota of the North Sea are quite capable of accommodating newcomers. However, this is no guarantee that the next introduced species may not cause severe ecological change or economic harm. There is a need to minimize the risk of unintentional introductions by ballast water treatment and by adhering to quarantine procedures in aquaculture. Current research on exotics in the North Sea is regarded as inadequate for proper evaluation and management requirements.

  18. 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

  19. The Continental Margins of the Western North Atlantic.

    ERIC Educational Resources Information Center

    Schlee, John S.; And Others

    1979-01-01

    Presents an interpretation of geological and geophysical data, which provides a summary of the structural and sedimentary history of the United States Atlantic Margin. The importance of an understanding of the development of the outer continental shelf to future hydrocarbon exploration is detailed. (BT)

  20. Hydrological change in Southern Europe responding to increasing North Atlantic overturning during Greenland Stadial 1

    PubMed Central

    Bartolomé, Miguel; Moreno, Ana; Sancho, Carlos; Stoll, Heather M.; Cacho, Isabel; Spötl, Christoph; Belmonte, Ánchel; Edwards, R. Lawrence; Cheng, Hai; Hellstrom, John C.

    2015-01-01

    Greenland Stadial 1 (GS-1) was the last of a long series of severe cooling episodes in the Northern Hemisphere during the last glacial period. Numerous North Atlantic and European records reveal the intense environmental impact of that stadial, whose origin is attributed to an intense weakening of the Atlantic Meridional Overturning Circulation in response to freshening of the North Atlantic. Recent high-resolution studies of European lakes revealed a mid–GS-1 transition in the climatic regimes. The geographical extension of such atmospheric changes and their potential coupling with ocean dynamics still remains unclear. Here we use a subdecadally resolved stalagmite record from the Northern Iberian Peninsula to further investigate the timing and forcing of this transition. A solid interpretation of the environmental changes detected in this new, accurately dated, stalagmite record is based on a parallel cave monitoring exercise. This record reveals a gradual transition from dry to wet conditions starting at 12,500 y before 2000 A.D. in parallel to a progressive warming of the subtropical Atlantic Ocean. The observed atmospheric changes are proposed to be led by a progressive resumption of the North Atlantic convection and highlight the complex regional signature of GS-1, very distinctive from previous stadial events. PMID:25964366

  1. Hydrological change in Southern Europe responding to increasing North Atlantic overturning during Greenland Stadial 1.

    PubMed

    Bartolomé, Miguel; Moreno, Ana; Sancho, Carlos; Stoll, Heather M; Cacho, Isabel; Spötl, Christoph; Belmonte, Ánchel; Edwards, R Lawrence; Cheng, Hai; Hellstrom, John C

    2015-05-26

    Greenland Stadial 1 (GS-1) was the last of a long series of severe cooling episodes in the Northern Hemisphere during the last glacial period. Numerous North Atlantic and European records reveal the intense environmental impact of that stadial, whose origin is attributed to an intense weakening of the Atlantic Meridional Overturning Circulation in response to freshening of the North Atlantic. Recent high-resolution studies of European lakes revealed a mid-GS-1 transition in the climatic regimes. The geographical extension of such atmospheric changes and their potential coupling with ocean dynamics still remains unclear. Here we use a subdecadally resolved stalagmite record from the Northern Iberian Peninsula to further investigate the timing and forcing of this transition. A solid interpretation of the environmental changes detected in this new, accurately dated, stalagmite record is based on a parallel cave monitoring exercise. This record reveals a gradual transition from dry to wet conditions starting at 12,500 y before 2000 A.D. in parallel to a progressive warming of the subtropical Atlantic Ocean. The observed atmospheric changes are proposed to be led by a progressive resumption of the North Atlantic convection and highlight the complex regional signature of GS-1, very distinctive from previous stadial events. PMID:25964366

  2. Black carbon concentrations and sources in the marine boundary layer of the tropical Atlantic Ocean using four methodologies

    EPA Science Inventory

    Combustion-derived aerosols in the marine boundary layer have been poorly studied, especially in remote environments such as the open Atlantic Ocean. The tropical Atlantic has the potential to contain a high concentration of aerosols, such as black carbon, due to the African emis...

  3. The Influence of the North Atlantic Oscillation on Tropospheric Distributions of Ozone and Carbon Monoxide.

    NASA Astrophysics Data System (ADS)

    Knowland, K. E.; Doherty, R. M.; Hodges, K.

    2015-12-01

    The influence of the North Atlantic Oscillation (NAO) on the tropospheric distributions of ozone (O3) and carbon monoxide (CO) has been quantified. The Monitoring Atmospheric Composition and Climate (MACC) Reanalysis, a combined meteorology and composition dataset for the period 2003-2012 (Innes et al., 2013), is used to investigate the composition of the troposphere and lower stratosphere in relation to the location of the storm track as well as other meteorological parameters over the North Atlantic associated with the different NAO phases. Cyclone tracks in the MACC Reanalysis compare well to the cyclone tracks in the widely-used ERA-Interim Reanalysis for the same 10-year period (cyclone tracking performed using the tracking algorithm of Hodges (1995, 1999)), as both are based on the European Centre for Medium-Range Weather Forecasts' (ECMWF) Integrated Forecast System (IFS). A seasonal analysis is performed whereby the MACC reanalysis meteorological fields, O3 and CO mixing ratios are weighted by the monthly NAO index values. The location of the main storm track, which tilts towards high latitudes (toward the Arctic) during positive NAO phases to a more zonal location in the mid-latitudes (toward Europe) during negative NAO phases, impacts the location of both horizontal and vertical transport across the North Atlantic and into the Arctic. During positive NAO seasons, the persistence of cyclones over the North Atlantic coupled with a stronger Azores High promotes strong horizontal transport across the North Atlantic throughout the troposphere. In all seasons, significantly more intense cyclones occur at higher latitudes (north of ~50°C) during the positive phase of the NAO and in the southern mid-latitudes during the negative NAO phase. This impacts the location of stratospheric intrusions within the descending dry airstream behind the associated cold front of the extratropical cyclone and the venting of low-level pollution up into the free troposphere within

  4. A spatially explicit estimate of the prewhaling abundance of the endangered North Atlantic right whale.

    PubMed

    Monsarrat, Sophie; Pennino, M Grazia; Smith, Tim D; Reeves, Randall R; Meynard, Christine N; Kaplan, David M; Rodrigues, Ana S L

    2016-08-01

    The North Atlantic right whale (NARW) (Eubalaena glacialis) is one of the world's most threatened whales. It came close to extinction after nearly a millennium of exploitation and currently persists as a population of only approximately 500 individuals. Setting appropriate conservation targets for this species requires an understanding of its historical population size, as a baseline for measuring levels of depletion and progress toward recovery. This is made difficult by the scarcity of records over this species' long whaling history. We sought to estimate the preexploitation population size of the North Atlantic right whale and understand how this species was distributed across its range. We used a spatially explicit data set on historical catches of North Pacific right whales (NPRWs) (Eubalaena japonica) to model the relationship between right whale relative density and the environment during the summer feeding season. Assuming the 2 right whale species select similar environments, we projected this model to the North Atlantic to predict how the relative abundance of NARWs varied across their range. We calibrated these relative abundances with estimates of the NPRW total prewhaling population size to obtain high and low estimates for the overall NARW population size prior to exploitation. The model predicted 9,075-21,328 right whales in the North Atlantic. The current NARW population is thus <6% of the historical North Atlantic carrying capacity and has enormous potential for recovery. According to the model, in June-September NARWs concentrated in 2 main feeding areas: east of the Grand Banks of Newfoundland and in the Norwegian Sea. These 2 areas may become important in the future as feeding grounds and may already be used more regularly by this endangered species than is thought. PMID:26632250

  5. 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.

  6. 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.

  7. Abrupt climate events 500,000 to 340,000 years ago: Evidence from subpolar North Atlantic sediments

    SciTech Connect

    Oppo, D.W.; McManus, J.F.; Cullen, J.L.

    1998-02-27

    Subpolar North Atlantic proxy records document millennial-scale climate variations 500,000 to 340,000 years ago. The cycles have an approximately constant pacing that is similar to that documented for the last glacial cycle. These findings suggest that such climate variations are inherent to the late Pleistocene, regardless of glacial state. Sea surface temperature during the warm peak of Marine Isotope Stage 11 (MIS 11) varied by 0.5{degree} to 1{degree}C, less than the 4{degree} to 4.5{degree}C estimated during times of ice growth and the 3{degree}C estimated for glacial maxima. Coherent deep ocean circulation changes were associated with glacial oscillations in sea surface temperature. 31 refs., 3 figs.

  8. Global Cosmic Ray Intensity Changes, Solar Activity Variations and Geomagnetic Disturbances as North Atlantic Hurricane Precursors

    NASA Astrophysics Data System (ADS)

    Kavlakov, S. P.

    It was shown that specific changes of the sunspots (SS) number, cosmic ray (CR) intensity and geomagnetic activity indices AP and KP were statistically noticeable in the interval of 30 days before the appearance of a cyclonic rotational system over the North Atlantic, developing gradually in a major hurricane.

  9. 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.

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

    PubMed

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

    2013-05-01

    The North-Atlantic has warmed faster than all other ocean basins and climate change scenarios predict sea surface temperature isotherms to shift up to 600 km northwards by the end of the 21st century. The pole-ward shift has already begun for many temperate seaweed species that are important intertidal foundation species. We asked the question: Where will climate change have the greatest impact on three foundational, macroalgal species that occur along North-Atlantic shores: Fucus serratus, Fucus vesiculosus, and Ascophyllum nodosum? To predict distributional changes of these key species under three IPCC (Intergovernmental Panel on Climate Change) climate change scenarios (A2, A1B, and B1) over the coming two centuries, we generated Ecological Niche Models with the program MAXENT. Model predictions suggest that these three species will shift northwards as an assemblage or "unit" and that phytogeographic changes will be most pronounced in the southern Arctic and the southern temperate provinces. Our models predict that Arctic shores in Canada, Greenland, and Spitsbergen will become suitable for all three species by 2100. Shores south of 45° North will become unsuitable for at least two of the three focal species on both the Northwest- and Northeast-Atlantic coasts by 2200. If these foundational species are unable to adapt to the rising temperatures, they will lose their centers of genetic diversity and their loss will trigger an unpredictable shift in the North-Atlantic intertidal ecosystem. PMID:23762521

  11. 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.

  12. 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

  13. 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.

  14. 77 FR 25892 - Security Zones; North Atlantic Treaty Organization (NATO) Summit, Chicago, IL

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-02

    ... proposed rule (77 FR 13232) that would establish four separate security zones in the Chicago Harbor and Chicago River during the NATO Summit. This statement is incorrect. The Coast Guard received one comment... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA87 Security Zones; North Atlantic Treaty Organization...

  15. 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…

  16. 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.

  17. 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.

  18. Cenozoic unconformities and depositional supersequences of North Atlantic continental margins: testing the Vail model

    USGS Publications Warehouse

    Poag, C. Wylie; Ward, Lauck W.

    1987-01-01

    Integrated outcrop, borehole, and seismic reflection stratigraphy from the U.S. and Irish margins of the North Atlantic basin reveals a framework of Cenozoic depositional supersequences and interregional unconformities that resembles the Vail depositional model. Paleo-bathymetric and paleoceanographic analyses of associated microfossil assemblages indicate a genetic link between the depositional framework and the relative position of sea level.

  19. Cadmium in the North Atlantic: Implication for global cadmium-phosphorus relationship

    NASA Astrophysics Data System (ADS)

    Wu, Jingfeng; Roshan, Saeed

    2015-06-01

    Dissolved cadmium (Cd) distribution was determined in the tropical-subtropical North Atlantic along GEOTRACES GA03 section (US GEOTRACES 2010 and 2011 cruises). A pronounced mid-depth Cd maximum extends from the productive tropical eastern North Atlantic where subsurface waters in the upper themocline are depleted in dissolved oxygen. At this Cd maximum, Cd depletion relative to phosphate (PO4) is observed in the Cd vs. PO4 plot, but the relative Cd depletion is not present in the plot of Cd:PO4 ratio vs depth. The apparent relative Cd depletion at the Cd maximum appears to reflect a depth-dependent variation of Cd:PO4 ratio commonly observed in the world ocean. Such depth dependent variation of Cd:PO4 ratio may result from the regeneration of Cd from Cd-poor particulate organic carbon (POC) in the upper ocean and from Cd-rich POC in the deep ocean. The vertical Cd regeneration may lead to the observed difference in deep water Cd:PO4 ratio between the North Atlantic and North Pacific, if Cd to phosphorus ratio in the POC flux to the deep ocean is higher in the Pacific than in the Atlantic.

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

    USGS Publications Warehouse

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

    2009-01-01

    The Mid-Pliocene is the most recent interval in the Earth's history to have experienced warming of the magnitude predicted for the second half of the twenty-first century and is, therefore, a possible analogue for future climate conditions. With continents basically in their current positions and atmospheric CO2 similar to early twenty-first century values, the cause of Mid-Pliocene warmth remains elusive. Understanding the behaviour of the North Atlantic Ocean during the Mid-Pliocene is integral to evaluating future climate scenarios owing to its role in deep water formation and its sensitivity to climate change. Under the framework of the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) sea surface reconstruction, we synthesize Mid-Pliocene North Atlantic studies by PRISM members and others, describing each region of the North Atlantic in terms of palaeoceanography. We then relate Mid-Pliocene sea surface conditions to expectations of future warming. The results of the data and climate model comparisons suggest that the North Atlantic is more sensitive to climate change than is suggested by climate model simulations, raising the concern that estimates of future climate change are conservative. ?? 2008 The Royal Society.

  1. 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...

  2. Carbon Cycling in the Arctic Archipelago: The Export of Pacific Carbon to the North Atlantic

    NASA Astrophysics Data System (ADS)

    Shadwick, E. H.; Papakyriakou, T.; Prowe, A. E. F.; Leong, D.; Moore, S.; Thomas, H.

    2009-04-01

    The Arctic Ocean is expected to be disproportionately sensitive to climatic changes, and thought to be an area where such changes might be detected. The Arctic hydrological cycle is influenced by: runoff and precipitation, sea ice formation/melting, and the inflow of saline waters from Bering and Fram Straits and the Barents Sea Shelf. Pacific water is recognizable as low salinity water, with high concentrations of dissolved inorganic carbon (DIC), flowing from the Arctic Ocean to the North Atlantic via the Canadian Arctic Archipelago. We present DIC data from an east-west section through the Archipelago, as part of the Canadian International Polar Year initiatives. The fractions of Pacific and Arctic Ocean waters leaving the Archipelago and entering Baffin Bay, and subsequently the North Atlantic, are computed. The eastward transport of carbon from the Pacific, via the Arctic, to the North Atlantic is estimated. Altered mixing ratios of Pacific and freshwater in the Arctic Ocean have been recorded in recent decades. Any climatically driven alterations in the composition of waters leaving the Arctic Archipelago may have implications for anthropogenic CO2 uptake, and hence ocean acidification, in the subpolar and temperate North Atlantic.

  3. Carbon cycling in the Arctic Archipelago: the export of Pacific carbon to the North Atlantic

    NASA Astrophysics Data System (ADS)

    Shadwick, E. H.; Papakyriakou, T.; Prowe, A. E. F.; Leong, D.; Moore, S. A.; Thomas, H.

    2009-01-01

    The Arctic Ocean is expected to be disproportionately sensitive to climatic changes, and is thought to be an area where such changes might be detected. The Arctic hydrological cycle is influenced by: runoff and precipitation, sea ice formation/melting, and the inflow of saline waters from Bering and Fram Straits and the Barents Sea Shelf. Pacific water is recognizable as intermediate salinity water, with high concentrations of dissolved inorganic carbon (DIC), flowing from the Arctic Ocean to the North Atlantic via the Canadian Arctic Archipelago. We present DIC data from an east-west section through the Archipelago, as part of the Canadian International Polar Year initiatives. The fractions of Pacific and Arctic Ocean waters leaving the Archipelago and entering Baffin Bay, and subsequently the North Atlantic, are computed. The eastward transport of carbon from the Pacific, via the Arctic, to the North Atlantic is estimated. Altered mixing ratios of Pacific and freshwater in the Arctic Ocean have been recorded in recent decades. Any climatically driven alterations in the composition of waters leaving the Arctic Archipelago may have implications for anthropogenic CO2 uptake, and hence ocean acidification, in the subpolar and temperate North Atlantic.

  4. 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 b