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Author Morey, S.; Wienders, N.; Dukhovskoy, D.; Bourassa, M. url  doi
openurl 
  Title Measurement Characteristics of Near-Surface Currents from Ultra-Thin Drifters, Drogued Drifters, and HF Radar Type $loc['typeJournal Article']
  Year 2018 Publication Remote Sensing Abbreviated Journal Remote Sensing  
  Volume 10 Issue 10 Pages 1633  
  Keywords surface drifters; surface currents; HF Radar; STOKES DRIFT; SEA-SURFACE; WAVES; BREAKING; VALIDATION; TRANSPORT  
  Abstract Concurrent measurements by satellite tracked drifters of different hull and drogue configurations and coastal high-frequency radar reveal substantial differences in estimates of the near-surface velocity. These measurements are important for understanding and predicting material transport on the ocean surface as well as the vertical structure of the near-surface currents. These near-surface current observations were obtained during a field experiment in the northern Gulf of Mexico intended to test a new ultra-thin drifter design. During the experiment, thirty small cylindrical drifters with 5 cm height, twenty-eight similar drifters with 10 cm hull height, and fourteen drifters with 91 cm tall drogues centered at 100 cm depth were deployed within the footprint of coastal High-Frequency (HF) radar. Comparison of collocated velocity measurements reveals systematic differences in surface velocity estimates obtained from the different measurement techniques, as well as provides information on properties of the drifter behavior and near-surface shear. Results show that the HF radar velocity estimates had magnitudes significantly lower than the 5 cm and 10 cm drifter velocity of approximately 45% and 35%, respectively. The HF radar velocity magnitudes were similar to the drogued drifter velocity. Analysis of wave directional spectra measurements reveals that surface Stokes drift accounts for much of the velocity difference between the drogued drifters and the thin surface drifters except during times of wave breaking.  
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  ISSN 2072-4292 ISBN Medium  
  Area Expedition Conference  
  Funding Approved $loc['no']  
  Call Number COAPS @ rl18 @ Serial 985  
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Author Ali, M.; Singh, N.; Kumar, M.; Zheng, Y.; Bourassa, M.; Kishtawal, C.; Rao, C. url  doi
openurl 
  Title Dominant Modes of Upper Ocean Heat Content in the North Indian Ocean Type $loc['typeJournal Article']
  Year 2018 Publication Climate Abbreviated Journal Climate  
  Volume 6 Issue 3 Pages 71  
  Keywords ocean heat content; tropical cyclone heat potential; dominant modes; North Indian Ocean; SUMMER MONSOON; INTENSIFICATION; INTENSITY; PACIFIC  
  Abstract The thermal energy needed for the development of hurricanes and monsoons as well as any prolonged marine weather event comes from layers in the upper oceans, not just from the thin layer represented by sea surface temperature alone. Ocean layers have different modes of thermal energy variability because of the different time scales of ocean-atmosphere interaction. Although many previous studies have focused on the influence of upper ocean heat content (OHC) on tropical cyclones and monsoons, no study thus farparticularly in the North Indian Ocean (NIO)has specifically concluded the types of dominant modes in different layers of the ocean. In this study, we examined the dominant modes of variability of OHC of seven layers in the NIO during 1998-2014. We conclude that the thermal variability in the top 50 m of the ocean had statistically significant semiannual and annual modes of variability, while the deeper layers had the annual mode alone. Time series of OHC for the top four layers were analyzed separately for the NIO, Arabian Sea, and Bay of Bengal. For the surface to 50 m layer, the lowest and the highest values of OHC were present in January and May every year, respectively, which was mainly caused by the solar radiation cycle.  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 2225-1154 ISBN Medium  
  Area Expedition Conference  
  Funding Approved $loc['no']  
  Call Number COAPS @ rl18 @ Serial 986  
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Author Misra, V.; Mishra, A.; Bhardwaj, A.; Viswanthan, K.; Schmutz, D. url  doi
openurl 
  Title The potential role of land cover on secular changes of the hydroclimate of Peninsular Florida Type $loc['typeJournal Article']
  Year 2018 Publication Climate and Atmospheric Science Abbreviated Journal Clim Atmos Sci  
  Volume 1 Issue 1 Pages  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 2397-3722 ISBN Medium  
  Area Expedition Conference  
  Funding Approved $loc['no']  
  Call Number COAPS @ mfield @ Serial 833  
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Author Zhang, M.; Zhang, Y.; Shu, Q.; Zhao, C.; Wang, G.; Wu, Z.; Qiao, F. url  doi
openurl 
  Title Spatiotemporal evolution of the chlorophyll a trend in the North Atlantic Ocean Type $loc['typeJournal Article']
  Year 2018 Publication The Science of the Total Environment Abbreviated Journal Sci Total Environ  
  Volume 612 Issue Pages 1141-1148  
  Keywords Chlorophyll a; Dipole pattern; Multidimensional ensemble empirical mode decomposition; Propagation; Spatiotemporal evolution; The variable trend  
  Abstract Analyses of the chlorophyll a concentration (chla) from satellite ocean color products have suggested the decadal-scale variability of chla linked to the climate change. The decadal-scale variability in chla is both spatially and temporally non-uniform. We need to understand the spatiotemporal evolution of chla in decadal or multi-decadal timescales to better evaluate its linkage to climate variability. Here, the spatiotemporal evolution of the chla trend in the North Atlantic Ocean for the period 1997-2016 is analyzed using the multidimensional ensemble empirical mode decomposition method. We find that this variable trend signal of chla shows a dipole pattern between the subpolar gyre and along the Gulf Stream path, and propagation along the opposite direction of the North Atlantic Current. This propagation signal has an overlapping variability of approximately twenty years. Our findings suggest that the spatiotemporal evolution of chla during the two most recent decades is part of the multidecadal variations and possibly regulated by the changes of Atlantic Meridional Overturning Circulation, whereas the mechanisms of such evolution patterns still need to be explored.  
  Address First Institute of Oceanography, State Oceanic Administration, Qingdao, China; Laboratory for Regional Oceanography and Numerical Modeling, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China; Key Laboratory of Data Analysis and Applications, State Oceanic Administration, Qingdao, China. Electronic address: qiaofl@fio.org.cn  
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  Language English Summary Language Original Title  
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  Series Volume Series Issue Edition  
  ISSN 0048-9697 ISBN Medium  
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  Funding PMID:28892858 Approved $loc['no']  
  Call Number COAPS @ mfield @ Serial 363  
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Author Stukel, M.R.; Décima, M.; Landry, M.R.; Selph, K.E. url  doi
openurl 
  Title Nitrogen and isotope flows through the Costa Rica Dome upwelling ecosystem: The crucial mesozooplankton role in export flux Type $loc['typeJournal Article']
  Year 2018 Publication Global Biogeochemical Cycles Abbreviated Journal Global Biogeochemical Cycles  
  Volume 32 Issue 12 Pages 18151832.  
  Keywords Crustaceans; Diel vertical migration; Nitrogen cycle; Biological carbon pump; Nitrogen isotopes; Linear inverse ecosystem model  
  Abstract The Costa Rica Dome (CRD) is an open-ocean upwelling ecosystem, with high biomasses of picophytoplankton (especially Synechococcus), mesozooplankton, and higher trophic levels. To elucidate the food web pathways supporting the trophic structure and carbon export in this unique ecosystem, we used Markov Chain Monte Carlo techniques to assimilate data from four independent realizations of δ15N and planktonic rate measurements from the CRD into steady state, multicompartment ecosystem box models (linear inverse models). Model results present well-constrained snapshots of ecosystem nitrogen and stable isotope fluxes. New production is supported by upwelled nitrate, not nitrogen fixation. Protistivory (rather than herbivory) was the most important feeding mode for mesozooplankton, which rely heavily on microzooplankton prey. Mesozooplankton play a central role in vertical nitrogen export, primarily through active transport of nitrogen consumed in the surface layer and excreted at depth, which comprised an average 36-46% of total export. Detritus or aggregate feeding is also an important mode of resource acquisition by mesozooplankton and regeneration of nutrients within the euphotic zone. As a consequence, the ratio of passively sinking particle export to phytoplankton production is very low in the CRD. Comparisons to similar models constrained with data from the nearby equatorial Pacific demonstrate that the dominant role of vertical migrators to the biological pump is a unique feature of the CRD. However, both regions show efficient nitrogen transfer from mesozooplankton to higher trophic levels (as expected for regions with large fish, cetacean, and seabird populations) despite the dominance of protists as major grazers of phytoplankton.  
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  Funding Approved $loc['no']  
  Call Number COAPS @ rl18 @ Serial 978  
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Author Xu, X.; Bower, A.; Furey, H.; Chassignet, E.P. url  doi
openurl 
  Title Variability of the Iceland-Scotland Overflow Water Transport Through the Charlie-Gibbs Fracture Zone: Results From an Eddying Simulation and Observations Type $loc['typeJournal Article']
  Year 2018 Publication Journal of Geophysical Research: Oceans Abbreviated Journal J. Geophys. Res. Oceans  
  Volume Issue 8 Pages  
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  Abstract Observations show that the westward transport of the Iceland‐Scotland overflow water (ISOW) through the Charlie‐Gibbs Fracture Zone (CGFZ) is highly variable. This study examines (a) where this variability comes from and (b) how it is related to the variability of ISOW transport at upstream locations in the Iceland Basin and other ISOW flow pathways. The analyses are based on a 35‐year 1/12° eddying Atlantic simulation that represents well the main features of the observed ISOW in the area of interest, in particular, the transport variability through the CGFZ. The results show that (a) the variability of the ISOW transport is closely correlated with that of the barotropic transports in the CGFZ associated with the meridional displacement of the North Atlantic Current front and is possibly induced by fluctuations of large‐scale zonal wind stress in the Western European Basin east of the CGFZ; (b) the variability of the ISOW transport is increased by a factor of 3 from the northern part of the Iceland Basin to the CGFZ region and transport time series at these two locations are not correlated, further suggesting that the variability at the CGFZ does not come from the upstream source; and (c) the variability of the ISOW transport at the CGFZ is strongly anticorrelated to that of the southward ISOW transport along the eastern flank of the Mid‐Atlantic Ridge, suggesting an out‐of‐phase covarying transport between these two ISOW pathways.  
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  Series Volume Series Issue Edition  
  ISSN 2169-9275 ISBN Medium  
  Area Expedition Conference  
  Funding Approved $loc['no']  
  Call Number COAPS @ user @ Serial 1023  
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Author Stukel, M.R.; Biard, T.; Krause, J.W.; Ohman, M.D. url  doi
openurl 
  Title Large Phaeodaria in the twilight zone: Their role in the carbon cycle Type $loc['typeJournal Article']
  Year 2018 Publication Association for the Sciences of Limnology and Oceanography Abbreviated Journal  
  Volume Issue Pages  
  Keywords Carbon cycle; Ocean; Twilight zone, Rhizarian measurements; Aulosphaeridae  
  Abstract Advances in in situ imaging allow enumeration of abundant populations of large Rhizarians that compose a substantial proportion of total mesozooplankton biovolume. Using a quasi-Lagrangian sampling scheme, we quantified the abundance, vertical distributions, and sinking&#8208;related mortality of Aulosphaeridae, an abundant family of Phaeodaria in the California Current Ecosystem. Inter&#8208;cruise variability was high, with average concentrations at the depth of maximum abundance ranging from < 10 to > 300 cells m&#8722;3, with seasonal and interannual variability associated with temperature&#8208;preferences and regional shoaling of the 10°C isotherm. Vertical profiles showed that these organisms were consistently most abundant at 100&#65533;150&#8201;m depth. Average turnover times with respect to sinking were 4.7&#65533;10.9 d, equating to minimum in situ population growth rates of ~ 0.1&#65533;0.2 d&#8722;1. Using simultaneous measurements of sinking organic carbon, we find that these organisms could only meet their carbon demand if their carbon : volume ratio were ~ 1 &#956;g C mm&#8722;3. This value is substantially lower than previously used in global estimates of rhizarian biomass, but is reasonable for organisms that use large siliceous tests to inflate their cross&#8208;sectional area without a concomitant increase in biomass. We found that Aulosphaeridae alone can intercept > 20% of sinking particles produced in the euphotic zone before these particles reach a depth of 300&#8201;m. Our results suggest that the local (and likely global) carbon biomass of Aulosphaeridae, and probably the large Rhizaria overall, needs to be revised downwards, but that these organisms nevertheless play a major role in carbon flux attenuation in the twilight zone.  
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  Funding Approved $loc['yes']  
  Call Number COAPS @ user @ Serial 967  
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Author Xu, X.; Chassignet, E.P., Wang, F. url  doi
openurl 
  Title On the variability of the Atlantic meridional overturning circulation transports in coupled CMIP5 simulations Type $loc['typeJournal Article']
  Year 2018 Publication Climate Dynamics Abbreviated Journal Clim Dyn.  
  Volume 51 Issue 11 Pages 6511-6531  
  Keywords NAO-AMOC; CMIP5; NAO index; AMOC index; meridional pressure gradient; magnitude; structure change of the NAO.  
  Abstract The Atlantic meridional overturning circulation (AMOC) plays a fundamental role in the climate system, and long-term climate simulations are used to understand the AMOC variability and to assess its impact. This study examines the basic characteristics of the AMOC variability in 44 CMIP5 (Phase 5 of the Coupled Model Inter-comparison Project) simulations, using the 18 atmospherically-forced CORE-II (Phase 2 of the Coordinated Ocean-ice Reference Experiment) simulations as a reference. The analysis shows that on interannual and decadal timescales, the AMOC variability in the CMIP5 exhibits a similar magnitude and meridional coherence as in the CORE-II simulations, indicating that the modeled atmospheric variability responsible for AMOC variability in the CMIP5 is in reasonable agreement with the CORE-II forcing. On multidecadal timescales, however, the AMOC variability is weaker by a factor of more than 2 and meridionally less coherent in the CMIP5 than in the CORE-II simulations. The CMIP5 simulations also exhibit a weaker long-term atmospheric variability in the North Atlantic Oscillation (NAO). However, one cannot fully attribute the weaker AMOC variability to the weaker variability in NAO because, unlike the CORE-II simulations, the CMIP5 simulations do not exhibit a robust NAO-AMOC linkage. While the variability of the wintertime heat flux and mixed layer depth in the western subpolar North Atlantic is strongly linked to the AMOC variability, the NAO variability is not.  
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  Call Number COAPS @ rl18 @ Serial 981  
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Author Robinson, W.; Speich, S.; Chassignet, E. url  doi
openurl 
  Title Exploring the Interplay Between Ocean Eddies and the Atmosphere Type $loc['typeJournal Article']
  Year 2018 Publication Eos Abbreviated Journal Eos  
  Volume 99 Issue Pages  
  Keywords Mesoscale; Climate; Variability; Atmospheric  
  Abstract Climate models, for the first time, have sufficient resolution to capture mesoscale ocean eddies and their interactions with the atmosphere.New model results suggest that the atmosphere, at weather scales or larger, responds to cumulative effects of the much smaller ocean eddies. Intriguing new model results presented at the workshop suggested that the atmosphere, at weather scales or larger.  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 2324-9250 ISBN Medium  
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  Funding Approved $loc['no']  
  Call Number COAPS @ rl18 @ Serial 988  
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Author LaCasce, J.H.; Escartin, J.; Chassignet, E.P.; Xu, X. url  doi
openurl 
  Title Jet instability over smooth, corrugated and realistic bathymetry Type $loc['typeJournal Article']
  Year 2018 Publication Journal of Physical Oceanography Abbreviated Journal J. Phys. Oceanogr.  
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  Abstract The stability of a horizontally- and vertically-sheared surface jet is examined, with a focus on the vertical structure of the resultant eddies. Over a flat bottom, the instability is mixed baroclinic/barotropic, producing strong eddies at depth which are characteristically shifted downstream relative to the surface eddies. Baroclinic instability is suppressed over a large slope for retrograde jets (with a flow anti-parallel to topographic wave propagation), and to a lesser extent for prograde jets (with flow parallel to topographic wave propagation), as seen previously. In such cases, barotropic (lateral) instability dominates if the jet is sufficiently narrow. This yields surface eddies whose size is independent of the slope but proportional to the jet width. Deep eddies still form, forced by interfacial motion associated with the surface eddies, but they are weaker than under baroclinic instability and are vertically aligned with the surface eddies. A sinusoidal ridge acts similarly, suppressing baroclinic instability and favoring lateral instability in the upper layer.

A ridge with a 1 km wavelength and an amplitude of roughly 10 m is sufficient to suppress baroclinic instability. Surveys of bottom roughness from bathymetry acquired with shipboard multibeam echosounding reveal that such heights are common, beneath the Kuroshio, the Antarctic Circumpolar Current and, to a lesser extent, the Gulf Stream. Consistent with this, vorticity and velocity cross sections from a 1/50° HYCOM simulation suggest that Gulf Stream eddies are vertically aligned, as in the linear stability calculations with strong topography. Thus lateral instability may be more common than previously thought, due to topography hindering vertical energy transfer.
 
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0022-3670 ISBN Medium  
  Area Expedition Conference  
  Funding Approved $loc['no']  
  Call Number COAPS @ user @ Serial 998  
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