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  • 1
    Online Resource
    Online Resource
    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
    detail.hit.zdb_id: 2029396-3
    detail.hit.zdb_id: 419957-1
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  • 2
    Online Resource
    Online Resource
    Formation of the South Pacific Shallow Salinity Minimum: A Southern Ocean Pathway to the Tropical Pacific
    American Meteorological Society ; 2004
    In:  Journal of Physical Oceanography Vol. 34, No. 11 ( 2004-11-01), p. 2398-2412
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 34, No. 11 ( 2004-11-01), p. 2398-2412
    Abstract: In the eastern South Pacific Ocean, at a depth of about 200 m, a salinity minimum is found. This minimum is associated with a particular water mass, the “Shallow Salinity Minimum Water” (SSMW). SSMW outcrops in a fresh tongue (Smin) centered at about 45°S. The Smin appears to emanate from the eastern boundary, against the mean flow. The watermass transformation that creates SSMW and Smin is investigated here. The Smin and SSMW are transformed from saltier and warmer waters originating from the western South Pacific. The freshening and cooling occur when the water is advected eastward at the poleward side of the subtropical gyre. Sources of freshening and cooling are air–sea exchange and advection of water from south of the subtropical gyre. A freshwater and heat budget for the mixed layer reveals that both sources equally contribute to the watermass transformation in the mixed layer. The freshened and cooled mixed layer water is subducted into the gyre interior along the southern rim of the subtropical gyre. Subduction into the zonal flow restricts the transformation of interior properties to diffusion only. A simple advection/diffusion balance reveals diffusion coefficients of order 2000 m2 s−1. The tongue shape of the Smin is explained from a dynamical viewpoint because no relation to a positive precipitation–evaporation balance was found. Freshest Smin values are found to coincide with slowest eastward mixed layer flow that accumulates the largest amounts of freshwater in the mixed layer and creates the fresh tongue at the sea surface. Although the SSMW is the densest and freshest mode of water subducted along the South American coast, the freshening and cooling in the South Pacific affect a whole range of densities (25.0–26.8 kg m−3). The transformed water turns northward with the gyre circulation and contributes to the hydrographic structure of the gyre farther north. Because the South Pacific provides most of the source waters that upwell along the equatorial Pacific, variability in South Pacific hydrography may influence equatorial Pacific hydrography. Because one-half of the transformation is found to be controlled through Ekman transport, variability in wind forcing at the southern rim of the subtropical gyre may be a source for variability of the equatorial Pacific.
    Type of Medium: Online Resource
    ISSN: 1520-0485 , 0022-3670
    URL: Article
    DOI: 10.1175/JPO2634.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2004
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 3
    Online Resource
    Online Resource
    Formation of Southern Hemisphere Thermocline Waters: Water Mass Conversion and Subduction*
    American Meteorological Society ; 2002
    In:  Journal of Physical Oceanography Vol. 32, No. 11 ( 2002-11), p. 3020-3038
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 32, No. 11 ( 2002-11), p. 3020-3038
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/1520-0485(2002)032〈3020:FOSHTW〉2.0.CO;2
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2002
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 4
    Online Resource
    Online Resource
    Mean Conditions and Seasonality of the West Greenland Boundary Current System near Cape Farewell
    American Meteorological Society ; 2020
    In:  Journal of Physical Oceanography Vol. 50, No. 10 ( 2020-10-01), p. 2849-2871
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 50, No. 10 ( 2020-10-01), p. 2849-2871
    Abstract: The structure, transport, and seasonal variability of the West Greenland boundary current system near Cape Farewell are investigated using a high-resolution mooring array deployed from 2014 to 2018. The boundary current system is comprised of three components: the West Greenland Coastal Current, which advects cold and fresh Upper Polar Water (UPW); the West Greenland Current, which transports warm and salty Irminger Water (IW) along the upper slope and UPW at the surface; and the Deep Western Boundary Current, which advects dense overflow waters. Labrador Sea Water (LSW) is prevalent at the seaward side of the array within an offshore recirculation gyre and at the base of the West Greenland Current. The 4-yr mean transport of the full boundary current system is 31.1 ± 7.4 Sv (1 Sv ≡ 10 6 m 3 s −1 ), with no clear seasonal signal. However, the individual water mass components exhibit seasonal cycles in hydrographic properties and transport. LSW penetrates the boundary current locally, through entrainment/mixing from the adjacent recirculation gyre, and also enters the current upstream in the Irminger Sea. IW is modified through air–sea interaction during winter along the length of its trajectory around the Irminger Sea, which converts some of the water to LSW. This, together with the seasonal increase in LSW entering the current, results in an anticorrelation in transport between these two water masses. The seasonality in UPW transport can be explained by remote wind forcing and subsequent adjustment via coastal trapped waves. Our results provide the first quantitatively robust observational description of the boundary current in the eastern Labrador Sea.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-20-0086.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 5
    Online Resource
    Online Resource
    Observations of Irminger Sea Anticyclonic Eddies
    American Meteorological Society ; 2013
    In:  Journal of Physical Oceanography Vol. 43, No. 4 ( 2013-04-01), p. 805-823
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 43, No. 4 ( 2013-04-01), p. 805-823
    Abstract: Mesoscale anticyclonic eddies in the Irminger Sea are observed using a mooring and a glider. Between 2002 and 2009, the mooring observed 53 anticyclones. Using a kinematic model, objective estimates of eddy length scales and velocity structure are made for 16 eddies. Anticyclones had a mean core diameter of 12 km, and their mean peak observed azimuthal speed was 0.1 m s−1. They had core salinities and potential temperatures of 34.91–34.98 and 4.48°–5.34°C, respectively, making them warm and salty features. These properties represent a typical salinity anomaly of 0.03 and a temperature anomaly of 0.28°C from noneddy values. All eddies had small (≪1) Rossby numbers. In 2006, the glider observed two anticyclones having diameters of about 20 km and peak azimuthal speeds of about 0.3 m s−1. Similar salinity anomalies were detected throughout the Irminger Sea by floats profiling in anticyclones. Two formation regions for the eddies are identified: one to the west of the Reykjanes Ridge and the other off the East Greenland Irminger Current near Cape Farewell close to the mooring. Observations indicate that eddies formed in the former region are larger than eddies observed at the mooring. A clear increase in eddy salinity is observed between 2002 and 2009. The observed breakup of these eddies in winter implies that they are a source of salt for the central gyre. The anticyclones are similar to those found in both the Labrador Sea and Norwegian Sea, making them a ubiquitous feature of the subpolar North Atlantic basins.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-11-0155.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2013
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 6
    Online Resource
    Online Resource
    Generation Mechanisms of Mesoscale Eddies in the Mauritanian Upwelling Region
    American Meteorological Society ; 2022
    In:  Journal of Physical Oceanography Vol. 52, No. 1 ( 2022-01), p. 161-182
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 52, No. 1 ( 2022-01), p. 161-182
    Abstract: The physical processes driving the genesis of surface- and subsurface-intensified cyclonic and anticyclonic eddies originating from the coastal current system of the Mauritanian upwelling region are investigated using a high-resolution (∼1.5 km) configuration of GFDL’s Modular Ocean Model. Estimating an energy budget for the boundary current reveals a baroclinically unstable state during its intensification phase in boreal summer and which is driving eddy generation within the near-coastal region. The mean poleward coastal flow’s interaction with the sloping topography induces enhanced anticyclonic vorticity, with potential vorticity close to zero generated in the bottom boundary layer. Flow separation at sharp topographic bends intensifies the anticyclonic vorticity, and submesoscale structures of low PV coalesce to form anticyclonic vortices. A combination of offshore Ekman transport and horizontal advection determined the amount of South Atlantic Central Water (SACW) in an anticyclonic eddy. A vortex with a relatively dense and low PV core will form an anticyclonic mode water eddy, which will subduct along isopycnals while propagating offshore and hence be shielded from surface buoyancy forcing. Less contribution of dense SACW promotes the generation of surface anticyclonic eddies as the core is composed of a lighter water mass, which causes the eddy to stay closer to the surface and hence be exposed to surface buoyancy forcing. Simulated cyclonic eddies are formed between the rotational flow of an offshore anticyclonic vortex and a poleward flowing boundary current, with eddy potential energy being the dominant source of eddy kinetic energy. All three types of eddies play a key role in the exchange between the Mauritanian coastal currents system and the adjacent eastern boundary shadow zone region.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-21-0092.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2022
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 7
    Online Resource
    Online Resource
    SeaCycler: A Moored Open-Ocean Profiling System for the Upper Ocean in Extended Self-Contained Deployments
    American Meteorological Society ; 2013
    In:  Journal of Atmospheric and Oceanic Technology Vol. 30, No. 7 ( 2013-07-01), p. 1555-1565
    Details
    In: Journal of Atmospheric and Oceanic Technology, American Meteorological Society, Vol. 30, No. 7 ( 2013-07-01), p. 1555-1565
    Abstract: The upper ocean, including the biologically productive euphotic zone and the mixed layer, has great relevance for studies of physical, biogeochemical, and ecosystem processes and their interaction. Observing this layer with a continuous presence, sampling many of the relevant variables, and with sufficient vertical resolution, has remained a challenge. Here a system is presented that can be deployed on the top of deep-ocean moorings, with a drive mechanism at depths of 150–200 m, which mechanically winches a large sensor float and smaller communications float tethered above it to the surface and back down again, typically twice per day for periods up to 1 year. The sensor float can carry several sizeable sensors, and it has enough buoyancy to reach the near surface and for the communications float to pierce the surface even in the presence of strong currents. The system can survive mooring blowover to 1000-m depth. The battery-powered design is made possible by using a balanced energy-conserving principle. Reliability is enhanced with a drive assembly that employs a single rotating part that has no slip rings or rotating seals. The profiling bodies can break the surface to sample the near-surface layer and to establish satellite communication for data relay or reception of new commands. An inductive pass-through mode allows communication with other mooring components throughout the water column beneath the system. A number of successful demonstration deployments have been completed.
    Type of Medium: Online Resource
    ISSN: 0739-0572 , 1520-0426
    URL: Article
    DOI: 10.1175/JTECH-D-11-00168.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2013
    detail.hit.zdb_id: 2021720-1
    detail.hit.zdb_id: 48441-6
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