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  • 1
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    Online Resource
    EUREC〈sup〉4〈/sup〉A
    Copernicus GmbH ; 2021
    In:  Earth System Science Data Vol. 13, No. 8 ( 2021-08-25), p. 4067-4119
    Details
    In: Earth System Science Data, Copernicus GmbH, Vol. 13, No. 8 ( 2021-08-25), p. 4067-4119
    Abstract: Abstract. The science guiding the EUREC4A campaign and its measurements is presented. EUREC4A comprised roughly 5 weeks of measurements in the downstream winter trades of the North Atlantic – eastward and southeastward of Barbados. Through its ability to characterize processes operating across a wide range of scales, EUREC4A marked a turning point in our ability to observationally study factors influencing clouds in the trades, how they will respond to warming, and their link to other components of the earth system, such as upper-ocean processes or the life cycle of particulate matter. This characterization was made possible by thousands (2500) of sondes distributed to measure circulations on meso- (200 km) and larger (500 km) scales, roughly 400 h of flight time by four heavily instrumented research aircraft; four global-class research vessels; an advanced ground-based cloud observatory; scores of autonomous observing platforms operating in the upper ocean (nearly 10 000 profiles), lower atmosphere (continuous profiling), and along the air–sea interface; a network of water stable isotopologue measurements; targeted tasking of satellite remote sensing; and modeling with a new generation of weather and climate models. In addition to providing an outline of the novel measurements and their composition into a unified and coordinated campaign, the six distinct scientific facets that EUREC4A explored – from North Brazil Current rings to turbulence-induced clustering of cloud droplets and its influence on warm-rain formation – are presented along with an overview of EUREC4A's outreach activities, environmental impact, and guidelines for scientific practice. Track data for all platforms are standardized and accessible at https://doi.org/10.25326/165 (Stevens, 2021), and a film documenting the campaign is provided as a video supplement.
    Type of Medium: Online Resource
    ISSN: 1866-3516
    URL: Article
    DOI: 10.5194/essd-13-4067-2021
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
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  • 2
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    Redfield stoichiometry in Arabian Sea subsurface waters
    American Geophysical Union (AGU) ; 2000
    In:  Global Biogeochemical Cycles Vol. 14, No. 1 ( 2000-03), p. 357-372
    Details
    In: Global Biogeochemical Cycles, American Geophysical Union (AGU), Vol. 14, No. 1 ( 2000-03), p. 357-372
    Abstract: A linear inverse mixing model is applied to hydrographic, nutrient, and carbon data collected during Joint Global Ocean Flux Study and World Ocean Circulation Experiment cruises in 1995 to estimate the ΔC org /ΔN/ΔP/ΔSi/‐ΔO 2 remineralization ratios within the Arabian Sea between 550 and 4500 m. The observed concentrations are separated into mixing fractions of source water masses and changes caused by remineralization processes, while the effect of denitrification is considered. In contrast to earlier investigations, diapycnal mixing, which plays an important role in dissolved matter fluxes in the Arabian Sea, is accounted for. The ratios are found to be variable with depth, especially in the upper 2000 m of the water column. We suppose that in general nutrients are released faster than carbon dioxide during remineralization. The ΔC org /ΔC inorg decrease from ∼4 ± 1 at 550 m to 2 ± 0.2 at 2000 m and 1.2 ± 0.3 at 4000 m, suggesting that the dissolution of calcium carbonate above the calcite lysocline is a potentially important process within the Arabian Sea.
    Type of Medium: Online Resource
    ISSN: 0886-6236 , 1944-9224
    URL: Article
    DOI: 10.1029/1999GB900077
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2000
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    SSG: 12
    SSG: 13
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  • 3
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    Middepth circulation of the eastern tropical South Pacific and its link to the oxygen minimum zone
    American Geophysical Union (AGU) ; 2011
    In:  Journal of Geophysical Research Vol. 116, No. C1 ( 2011-01-21)
    Details
    In: Journal of Geophysical Research, American Geophysical Union (AGU), Vol. 116, No. C1 ( 2011-01-21)
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2010JC006565
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2011
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    detail.hit.zdb_id: 3094104-0
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    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 2969341-X
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    detail.hit.zdb_id: 3094268-8
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    detail.hit.zdb_id: 2016804-4
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    detail.hit.zdb_id: 3094219-6
    detail.hit.zdb_id: 3094167-2
    detail.hit.zdb_id: 2220777-6
    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
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  • 4
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    A practical indicator for surface ocean heat and freshwater buoyancy fluxes and its application to the NCEP reanalysis data
    Stockholm University Press ; 2011
    In:  Tellus A: Dynamic Meteorology and Oceanography Vol. 63, No. 2 ( 2011-01-01), p. 338-
    Details
    In: Tellus A: Dynamic Meteorology and Oceanography, Stockholm University Press, Vol. 63, No. 2 ( 2011-01-01), p. 338-
    Type of Medium: Online Resource
    ISSN: 1600-0870
    URL: Article
    DOI: 10.1111/j.1600-0870.2011.00510.x
    Language: Unknown
    Publisher: Stockholm University Press
    Publication Date: 2011
    detail.hit.zdb_id: 2026987-0
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  • 5
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    435 Prospective Randomized Multicenter Trial to Compare Adenoma Detection Rate of HD Colonoscopy With Standard HD Colonoscopy - Intermediate Results
    Elsevier BV ; 2015
    In:  Gastrointestinal Endoscopy Vol. 81, No. 5 ( 2015-05), p. AB145-AB146
    Details
    In: Gastrointestinal Endoscopy, Elsevier BV, Vol. 81, No. 5 ( 2015-05), p. AB145-AB146
    Type of Medium: Online Resource
    ISSN: 0016-5107
    URL: Article
    DOI: 10.1016/j.gie.2015.03.1232
    RVK:
    XA 44545
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2015
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  • 6
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    Overturning in the Subpolar North Atlantic Program: A New International Ocean Observing System
    American Meteorological Society ; 2017
    In:  Bulletin of the American Meteorological Society Vol. 98, No. 4 ( 2017-04-01), p. 737-752
    Details
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 98, No. 4 ( 2017-04-01), p. 737-752
    Abstract: For decades oceanographers have understood the Atlantic meridional overturning circulation (AMOC) to be primarily driven by changes in the production of deep-water formation in the subpolar and subarctic North Atlantic. Indeed, current Intergovernmental Panel on Climate Change (IPCC) projections of an AMOC slowdown in the twenty-first century based on climate models are attributed to the inhibition of deep convection in the North Atlantic. However, observational evidence for this linkage has been elusive: there has been no clear demonstration of AMOC variability in response to changes in deep-water formation. The motivation for understanding this linkage is compelling, since the overturning circulation has been shown to sequester heat and anthropogenic carbon in the deep ocean. Furthermore, AMOC variability is expected to impact this sequestration as well as have consequences for regional and global climates through its effect on the poleward transport of warm water. Motivated by the need for a mechanistic understanding of the AMOC, an international community has assembled an observing system, Overturning in the Subpolar North Atlantic Program (OSNAP), to provide a continuous record of the transbasin fluxes of heat, mass, and freshwater, and to link that record to convective activity and water mass transformation at high latitudes. OSNAP, in conjunction with the Rapid Climate Change–Meridional Overturning Circulation and Heatflux Array (RAPID–MOCHA) at 26°N and other observational elements, will provide a comprehensive measure of the three-dimensional AMOC and an understanding of what drives its variability. The OSNAP observing system was fully deployed in the summer of 2014, and the first OSNAP data products are expected in the fall of 2017.
    Type of Medium: Online Resource
    ISSN: 0003-0007 , 1520-0477
    URL: Article
    DOI: 10.1175/BAMS-D-16-0057.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2017
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  • 7
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    Mean circulation and EKE distribution in the Labrador Sea Water level of the subpolar North Atlantic
    Copernicus GmbH ; 2018
    In:  Ocean Science Vol. 14, No. 5 ( 2018-10-05), p. 1167-1183
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 14, No. 5 ( 2018-10-05), p. 1167-1183
    Abstract: Abstract. A long-term mean flow field for the subpolar North Atlantic region with a horizontal resolution of approximately 25 km is created by gridding Argo-derived velocity vectors using two different topography-following interpolation schemes. The 10-day float displacements in the typical drift depths of 1000 to 1500 m represent the flow in the Labrador Sea Water density range. Both mapping algorithms separate the flow field into potential vorticity (PV) conserving, i.e., topography-following contribution and a deviating part, which we define as the eddy contribution. To verify the significance of the separation, we compare the mean flow and the eddy kinetic energy (EKE), derived from both mapping algorithms, with those obtained from multiyear mooring observations. The PV-conserving mean flow is characterized by stable boundary currents along all major topographic features including shelf breaks and basin-interior topographic ridges such as the Reykjanes Ridge or the Rockall Plateau. Mid-basin northward advection pathways from the northeastern Labrador Sea into the Irminger Sea and from the Mid-Atlantic Ridge region into the Iceland Basin are well-resolved. An eastward flow is present across the southern boundary of the subpolar gyre near 52∘ N, the latitude of the Charlie Gibbs Fracture Zone (CGFZ). The mid-depth EKE field resembles most of the satellite-derived surface EKE field. However, noticeable differences exist along the northward advection pathways in the Irminger Sea and the Iceland Basin, where the deep EKE exceeds the surface EKE field. Further, the ratio between mean flow and the square root of the EKE, the Peclet number, reveals distinct advection-dominated regions as well as basin-interior regimes in which mixing is prevailing.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    DOI: 10.5194/os-14-1167-2018
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
    detail.hit.zdb_id: 2183769-7
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  • 8
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    Oxygen export to the deep ocean following Labrador Sea Water formation
    Copernicus GmbH ; 2022
    In:  Biogeosciences Vol. 19, No. 2 ( 2022-01-28), p. 437-454
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 19, No. 2 ( 2022-01-28), p. 437-454
    Abstract: Abstract. The Labrador Sea in the North Atlantic Ocean is one of the few regions globally where oxygen from the atmosphere can reach the deep ocean directly. This is the result of wintertime deep convection, which homogenizes the water column to a depth of up to 2000 m and brings deep water undersaturated in oxygen into contact with the atmosphere. In this study, we analyze how the intense oxygen uptake during Labrador Sea Water (LSW) formation affects the properties of the outflowing deep western boundary current, which ultimately feeds the upper part of the North Atlantic Deep Water layer in much of the Atlantic Ocean. Seasonal cycles of oxygen concentration, temperature, and salinity from a 2-year time series collected by sensors moored at 600 m nominal depth in the outflowing boundary current at 53∘ N show a cooling, freshening, and increase in oxygen content of the water flowing out of the basin between March and August. Analysis of Argo float data suggests that this is preceded by an increased input of LSW into the boundary current about 1 month earlier. This input is the result of newly ventilated LSW entering from the interior, as well as LSW formed directly within the boundary current. Together, these results imply that the southward export of newly formed LSW primarily occurs in the months following the onset of deep convection, from March to August, and that this direct LSW export route controls the seasonal oxygen increase in the outflow at 600 m depth. During the rest of the year, properties of the boundary current measured at 53∘ N resemble those of Irminger Water, which enters the basin with the boundary current from the Irminger Sea. The input of newly ventilated LSW increases the oxygen concentration from 298 µmol L−1 in January to a maximum of 306 µmol L−1 in April. As a result of this LSW input, an estimated (1.60 ± 0.42) × 1012 mol yr−1 of oxygen are added to the outflowing boundary current, mostly during spring and summer, equivalent to 50 % of the wintertime uptake from the atmosphere in the interior of the basin. The export of oxygen from the subpolar gyre associated with this direct southward pathway of LSW is estimated to supply 42 %–71 % of the oxygen consumed annually in the upper North Atlantic Deep Water layer in the Atlantic Ocean between the Equator and 50∘ N. Our results show that the formation of LSW is important for replenishing oxygen to the deep oceans, meaning that possible changes in its formation rate and ventilation due to climate change could have wide-reaching impacts on marine life.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    DOI: 10.5194/bg-19-437-2022
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
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  • 9
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    Occurrence and characteristics of mesoscale eddies in the tropical northeastern Atlantic Ocean
    Copernicus GmbH ; 2016
    In:  Ocean Science Vol. 12, No. 3 ( 2016-05-13), p. 663-685
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 12, No. 3 ( 2016-05-13), p. 663-685
    Abstract: Abstract. Coherent mesoscale features (referred to here as eddies) in the tropical northeastern Atlantic Ocean (between 12–22° N and 15–26° W) are examined and characterized. The eddies' surface signatures are investigated using 19 years of satellite-derived sea level anomaly (SLA) data. Two automated detection methods are applied, the geometrical method based on closed streamlines around eddy cores, and the Okubo–Weiß method based on the relation between vorticity and strain. Both methods give similar results. Mean eddy surface signatures of SLA, sea surface temperature (SST) and sea surface salinity (SSS) anomalies are obtained from composites of all snapshots around identified eddy cores. Anticyclones/cyclones are identified by an elevation/depression of SLA and enhanced/reduced SST and SSS in their cores. However, about 20 % of all anticyclonically rotating eddies show reduced SST and reduced SSS instead. These kind of eddies are classified as anticyclonic mode-water eddies (ACMEs). About 146 ± 4 eddies per year with a minimum lifetime of 7 days are identified (52 % cyclones, 39 % anticyclones, 9 % ACMEs) with rather similar mean radii of about 56 ± 12 km. Based on concurrent in situ temperature and salinity profiles (from Argo float, shipboard, and mooring data) taken inside of eddies, distinct mean vertical structures of the three eddy types are determined. Most eddies are generated preferentially in boreal summer and along the West African coast at three distinct coastal headland regions and carry South Atlantic Central Water supplied by the northward flow within the Mauretanian coastal current system. Westward eddy propagation (on average about 3.00 ± 2.15 km d−1) is confined to distinct zonal corridors with a small meridional deflection dependent on the eddy type (anticyclones – equatorward, cyclones – poleward, ACMEs – no deflection). Heat and salt fluxes out of the coastal region and across the Cape Verde Frontal Zone, which separates the shadow zone from the ventilated subtropical gyre, are calculated.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    DOI: 10.5194/os-12-663-2016
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2016
    detail.hit.zdb_id: 2183769-7
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  • 10
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    Biogeochemical characteristics of a long-lived anticyclonic eddy in the eastern South Pacific Ocean
    Copernicus GmbH ; 2016
    In:  Biogeosciences Vol. 13, No. 10 ( 2016-05-20), p. 2971-2979
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 13, No. 10 ( 2016-05-20), p. 2971-2979
    Abstract: Abstract. Mesoscale eddies are important, frequent, and persistent features of the circulation in the eastern South Pacific (ESP) Ocean, transporting physical, chemical and biological properties from the productive shelves to the open ocean. Some of these eddies exhibit subsurface hypoxic or suboxic conditions and may serve as important hotspots for nitrogen loss, but little is known about oxygen consumption rates and nitrogen transformation processes associated with these eddies. In the austral fall of 2011, during the Tara Oceans expedition, an intrathermocline, anticyclonic, mesoscale eddy with a suboxic (〈 2 µmol kg−1 of O2), subsurface layer (200–400 m) was detected  ∼  900 km off the Chilean shore (30° S, 81° W). The core of the eddy's suboxic layer had a temperature-salinity signature characteristic of Equatorial Subsurface Water (ESSW) that at this latitude is normally restricted to an area near the coast. Measurements of nitrogen species within the eddy revealed undersaturation (below 44 %) of nitrous oxide (N2O) and nitrite accumulation (〉 0.5 µM), suggesting that active denitrification occurred in this water mass. Using satellite altimetry, we were able to track the eddy back to its region of formation on the coast of central Chile (36.1° S, 74.6° W). Field studies conducted in Chilean shelf waters close to the time of eddy formation provided estimates of initial O2 and N2O concentrations of the ESSW source water in the eddy. By the time of its offshore sighting, concentrations of both O2 and N2O in the subsurface oxygen minimum zone (OMZ) of the eddy were lower than concentrations in surrounding water and “source water” on the shelf, indicating that these chemical species were consumed as the eddy moved offshore. Estimates of apparent oxygen utilization rates at the OMZ of the eddy ranged from 0.29 to 44 nmol L−1 d−1 and the rate of N2O consumption was 3.92 nmol L−1 d−1. These results show that mesoscale eddies affect open-ocean biogeochemistry in the ESP not only by transporting physical and chemical properties from the coast to the ocean interior but also during advection, local biological consumption of oxygen within an eddy further generates conditions favorable to denitrification and loss of fixed nitrogen from the system.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    DOI: 10.5194/bg-13-2971-2016
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2016
    detail.hit.zdb_id: 2158181-2
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