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  • 1
    Online Resource
    Online Resource
    Monitoring geostrophic currents at the equator
    Elsevier BV ; 1987
    In:  Deep Sea Research Part A. Oceanographic Research Papers Vol. 34, No. 7 ( 1987-7), p. 1149-1161
    Details
    In: Deep Sea Research Part A. Oceanographic Research Papers, Elsevier BV, Vol. 34, No. 7 ( 1987-7), p. 1149-1161
    Type of Medium: Online Resource
    ISSN: 0198-0149
    URL: Article
    DOI: 10.1016/0198-0149(87)90069-0
    Language: English
    Publisher: Elsevier BV
    Publication Date: 1987
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  • 2
    Online Resource
    Online Resource
    Observations of Ekman Currents in the Southern Ocean
    American Meteorological Society ; 2009
    In:  Journal of Physical Oceanography Vol. 39, No. 3 ( 2009-03-01), p. 768-779
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 39, No. 3 ( 2009-03-01), p. 768-779
    Abstract: Largely zonal winds in the Southern Ocean drive an equatorward Ekman transport that constitutes the shallowest limb of the meridional overturning circulation of the Antarctic Circumpolar Current (ACC). Despite its importance, there have been no direct observations of the open ocean Ekman balance in the Southern Ocean until now. Using high-resolution repeat observations of upper-ocean velocity in Drake Passage, a mean Ekman spiral is resolved and Ekman transport is computed. The mean Ekman currents decay in amplitude and rotate anticyclonically with depth, penetrating to ∼100-m depth, above the base of the annual mean mixed layer at 120 m. The rotation depth scale exceeds the e-folding scale of the speed by about a factor of 3, resulting in a current spiral that is compressed relative to predictions from Ekman theory. Transport estimated from the observed currents is mostly equatorward and in good agreement with the Ekman transport computed from four different gridded wind products. The mean temperature of the Ekman layer is not distinguishable from temperature at the surface. Turbulent eddy viscosities inferred from Ekman theory and a direct estimate of the time-averaged stress were O(102–103) cm2 s−1. The latter calculation results in a profile of eddy viscosity that decreases in magnitude with depth and a time-averaged stress that is not parallel to the time-averaged vertical shear. The compression of the Ekman spiral and the nonparallel shear–stress relation are likely due to time averaging over the cycling of the stratification in response to diurnal buoyancy fluxes, although the action of surface waves and the oceanic response to high-frequency wind variability may also contribute.
    Type of Medium: Online Resource
    ISSN: 1520-0485 , 0022-3670
    URL: Article
    DOI: 10.1175/2008JPO3943.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2009
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  • 3
    Online Resource
    Online Resource
    Transport of mass, heat, salt, and nutrients in the southern California Current System: Annual cycle and interannual variability
    American Geophysical Union (AGU) ; 2001
    In:  Journal of Geophysical Research: Oceans Vol. 106, No. C5 ( 2001-05-15), p. 9255-9275
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 106, No. C5 ( 2001-05-15), p. 9255-9275
    Abstract: Net fluxes of mass, heat, salt, nutrients, oxygen, and chlorophyll into a control volume within the southern California Current System (CCS) were computed from data collected on 55 cruises over a 14 year period (1984–1997). This analysis builds on an earlier work [ Roemmich , 1989] by using an additional 39 cruises over 10 years, allowing for reliable estimates of the temporal variability in the fluxes on seasonal and interannual timescales and a reduction in the corresponding error budgets. A close balance was found between geostrophic convergence and Ekman divergence for the 14 year, seasonal, and interannual cruise subsets using three different wind products. Wind data taken concomitantly with the hydrographic sampling provided the best balance and hence the best flux estimates. The southern CCS was found to be a region with higher evaporation over precipitation and net heat gain by the ocean from the atmosphere (86 W m −2 in the 14 year mean) in all seasons. Significant variability in both the Ekman and geostrophic transports and the net property fluxes was found to be related to low‐frequency (interpentadal and El Niño‐Southern Oscillation timescale) changes in the dominant wind and circulation patterns in the CCS. Variability in primary productivity, estimated from the derived nutrient fluxes, accompanied the environmental changes. Application of this model to the ongoing data collection will further reduce the error bars on the fluxes and will allow for continued monitoring of changes in the physical and biological structure of the southern CCS.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/1999JC000165
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2001
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    detail.hit.zdb_id: 2016810-X
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    detail.hit.zdb_id: 2016800-7
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    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 2969341-X
    detail.hit.zdb_id: 161665-1
    detail.hit.zdb_id: 3094268-8
    detail.hit.zdb_id: 710256-2
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 3094181-7
    detail.hit.zdb_id: 3094219-6
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    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
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  • 4
    Online Resource
    Online Resource
    Reversing bottom circulation in the Somali Basin
    American Geophysical Union (AGU) ; 2000
    In:  Geophysical Research Letters Vol. 27, No. 16 ( 2000-08-15), p. 2565-2568
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 27, No. 16 ( 2000-08-15), p. 2565-2568
    Type of Medium: Online Resource
    ISSN: 0094-8276
    URL: Article
    DOI: 10.1029/1999GL011316
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2000
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    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 5
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    Online Resource
    Transition from Balanced to Unbalanced Motion in the Eastern Tropical Pacific
    American Meteorological Society ; 2022
    In:  Journal of Physical Oceanography Vol. 52, No. 8 ( 2022-08), p. 1775-1795
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 52, No. 8 ( 2022-08), p. 1775-1795
    Abstract: Kinetic energy associated with inertia–gravity waves (IGWs) and other ageostrophic phenomena often overwhelms kinetic energy due to geostrophic motions for wavelengths on the order of tens of kilometers. Understanding the dependencies of the wavelength at which balanced (geostrophic) variability ceases to be larger than unbalanced variability is important for interpreting high-resolution altimetric data. This wavelength has been termed the transition scale. This study uses acoustic Doppler current profiler (ADCP) data along with auxiliary observations and a numerical model to investigate the transition scale in the eastern tropical Pacific and the mechanisms responsible for its regional and seasonal variations. One-dimensional kinetic energy wavenumber spectra are separated into rotational and divergent components, and subsequently into vortex and wave components. The divergent motions, most likely predominantly IGWs, account for most of the energy at wavelengths less than 100 km. The observed regional and seasonal patterns in the transition scale are consistent with those from a high-resolution global simulation. Observations, however, show weaker seasonality, with only modest wintertime increases in vortex energy. The ADCP-inferred IGW wavenumber spectra suggest that waves with near-inertial frequency dominate the unbalanced variability, while in model output, internal tides strongly influence the wavenumber spectrum. The ADCP-derived transition scales from the eastern tropical Pacific are typically in the 100–200-km range.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    URL: Article
    DOI: 10.1175/JPO-D-21-0139.1
    DOI: 10.1175/JPO-D-21-0139.s1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2022
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  • 6
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    Online Resource
    Four Current Meter Models Compared in Strong Currents in Drake Passage
    American Meteorological Society ; 2013
    In:  Journal of Atmospheric and Oceanic Technology Vol. 30, No. 10 ( 2013-10-01), p. 2465-2477
    Details
    In: Journal of Atmospheric and Oceanic Technology, American Meteorological Society, Vol. 30, No. 10 ( 2013-10-01), p. 2465-2477
    Abstract: Seven current meters representing four models on a stiffly buoyed mooring were placed for an 11-month deployment to intercompare their velocity measurements: two vector-measuring current meters (VMCMs), two Aanderaa recording current meter (RCM) 11s, two Aanderaa SEAGUARDs, and a Nortek Aquadopp. The current meters were placed 6-m apart from each other at about 4000-m depth in an area of Drake Passage expected to have strong currents, nearly independent of depth near the bottom. Two high-current events occurred in bursts of semidiurnal pulses lasting several days, one with peak speeds up to 67 cm s−1 and the other above 35 cm s−1. The current-speed measurements all agreed within 7% of the median value when vector averaged over simultaneous time intervals. The VMCMs, chosen as the reference measurements, were found to measure the median of the mean-current magnitudes. The RCM11 and SEAGUARD current speeds agreed within 2% of the median at higher speeds (35–67 cm s−1), whereas in lower speed ranges (0–35 cm s−1) the vector-averaged speeds for the RCM11 and SEAGUARD were 4%–5% lower and 3%–5% higher than the median, respectively. The shorter-record Aquadopp current speeds were about 6% higher than the VMCMs over the range (0–40 cm s−1) encountered.
    Type of Medium: Online Resource
    ISSN: 0739-0572 , 1520-0426
    URL: Article
    DOI: 10.1175/JTECH-D-13-00032.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2013
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    detail.hit.zdb_id: 48441-6
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  • 7
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    Online Resource
    The role of air-sea fluxes in Subantarctic Mode Water formation : SAMW FORMATION
    American Geophysical Union (AGU) ; 2012
    In:  Journal of Geophysical Research: Oceans Vol. 117, No. C3 ( 2012-03), p. n/a-n/a
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 117, No. C3 ( 2012-03), p. n/a-n/a
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2011JC007798
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2012
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    detail.hit.zdb_id: 2016813-5
    detail.hit.zdb_id: 2016810-X
    detail.hit.zdb_id: 2403298-0
    detail.hit.zdb_id: 2016800-7
    detail.hit.zdb_id: 161666-3
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 2969341-X
    detail.hit.zdb_id: 161665-1
    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
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    detail.hit.zdb_id: 2220777-6
    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
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  • 8
    Online Resource
    Online Resource
    Formation rates of Subantarctic mode water and Antarctic intermediate water within the South Pacific
    Elsevier BV ; 2011
    In:  Deep Sea Research Part I: Oceanographic Research Papers Vol. 58, No. 5 ( 2011-5), p. 524-534
    Details
    In: Deep Sea Research Part I: Oceanographic Research Papers, Elsevier BV, Vol. 58, No. 5 ( 2011-5), p. 524-534
    Type of Medium: Online Resource
    ISSN: 0967-0637
    URL: Article
    DOI: 10.1016/j.dsr.2011.02.010
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2011
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    SSG: 14
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  • 9
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    Online Resource
    Compensating transport trends in the Drake Passage frontal regions yield no acceleration in net transport
    Springer Science and Business Media LLC ; 2023
    In:  Nature Communications Vol. 14, No. 1 ( 2023-11-28)
    Details
    In: Nature Communications, Springer Science and Business Media LLC, Vol. 14, No. 1 ( 2023-11-28)
    Abstract: Although the westerly winds that drive the Antarctic Circumpolar Current (ACC) have increased over the past several decades, the ACC response remains an open question. Here we use a 15-year time series of concurrent upper-ocean temperature, salinity, and ocean velocity with high spatial resolution across Drake Passage to analyze whether the net Drake Passage transport has accelerated in the last 15 years. We find that, although the net Drake Passage transport relative to 760 m shows insignificant acceleration, the net transport trend comprises compensating trends across the ACC frontal regions. Our results show an increase in the mesoscale eddy activity between the fronts consistent with buoyancy changes in the fronts and with an eddy saturation state. Furthermore, the increased eddy activity may play a role in redistributing momentum across the ACC frontal regions. The increase in eddy activity is expected to intensify the eddy-driven upwelling of deep warm waters around Antarctica, which has significant implications for ice-melting, sea level rise, and global climate.
    Type of Medium: Online Resource
    ISSN: 2041-1723
    URL: Article
    DOI: 10.1038/s41467-023-43499-2
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2023
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  • 10
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    Online Resource
    Near-Surface Eddy Heat and Momentum Fluxes in the Antarctic Circumpolar Current in Drake Passage
    American Meteorological Society ; 2011
    In:  Journal of Physical Oceanography Vol. 41, No. 7 ( 2011-07-01), p. 1385-1407
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 41, No. 7 ( 2011-07-01), p. 1385-1407
    Abstract: The authors present new estimates of the eddy momentum and heat fluxes from repeated high-resolution upper-ocean velocity and temperature observations in Drake Passage and interpret their role in the regional Antarctic Circumpolar Current (ACC) momentum balance. The observations span 7 yr and are compared to eddy fluxes estimated from a 3-yr set of output archived from an eddy-resolving global Parallel Ocean Program (POP) numerical simulation. In both POP and the observations, the stream-averaged cross-stream eddy momentum fluxes correspond to forcing consistent with both a potential vorticity flux into the axis of the Subantarctic Front (SAF) and a sharpening of all three main ACC fronts through Drake Passage. Further, the POP analysis indicates that the mean momentum advection terms reflect the steering of the mean ACC fronts and are not fully balanced by the eddy momentum forcing, which instead impacts the strength and number of ACC fronts. The comparison between POP and observed eddy heat fluxes was less favorable partly because of model bias in the water mass stratification. Observed cross-stream eddy heat fluxes are generally surface intensified and poleward in the ACC fronts, with values up to approximately −290 ± 80 kW m−2 in the Polar and Southern ACC Fronts. Interfacial form stresses FT, derived from observed eddy heat fluxes in the SAF, show little depth dependence below the Ekman layer. Although FT appears to balance the surface wind stress directly, the estimated interfacial form stress divergence is only an order of magnitude greater than the eddy momentum forcing in the SAF. Thus, although the eddy momentum forcing is of secondary importance in the momentum balance, its effect is not entirely negligible.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-10-05017.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2011
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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