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Author Xu, X. ; Rhines, P.B. ; Chassignet, E.P.
Title On Mapping the Diapycnal Water Mass Transformation of the Upper North Atlantic Ocean Type $loc['typeJournal Article']
Year 2018 Publication Journal of Physical Oceanography Abbreviated Journal J. Phys. Oceanogr.
Volume 48
Issue 10
Pages 2233-2258
Keywords Atmosphere-ocean interaction ; Boundary currents ; Diapycnal mixing ; Fronts ; Thermocline circulation
Abstract Diapycnal water mass transformation is the essence behind the Atlantic meridional overturning circulation (AMOC) and the associated heat/freshwater transports. Existing studies have mostly focused on the transformation that is forced by surface buoyancy fluxes, and the role of interior mixing is much less known. This study maps the three-dimensional structure of the diapycnal transformation, both surface forced and mixing induced, using results of a high-resolution numerical model that have been shown to represent the large-scale structure of the AMOC and the North Atlantic subpolar/subtropical gyres well. The analyses show that 1) annual mean transformation takes place seamlessly from the subtropical to the subpolar North Atlantic following the surface buoyancy loss along the northward-flowing upper AMOC limb; 2) mixing, including wintertime convection and warm-season restratification by mesoscale eddies in the mixed layer and submixed layer diapycnal mixing, drives transformations of (i) Subtropical Mode Water in the southern part of the subtropical gyre and (ii) Labrador Sea Water in the Labrador Sea and on its southward path in the western Newfoundland Basin; and 3) patterns of diapycnal transformations toward lighter and denser water do not align zonally�the net three-dimensional transformation is significantly stronger than the zonally integrated, two-dimensional AMOC streamfunction (50% in the southern subtropical North Atlantic and 60% in the western subpolar North Atlantic).
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0022-3670
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Area Expedition Conference
Funding Approved $loc['no']
Call Number COAPS @ user @
Serial 951
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Author Yu, B. ; Seed, A. ; Pu, L. ; Malone, T.
Title Integration of weather radar data into a raster GIS framework for improved flood estimation Type $loc['typeJournal Article']
Year 2019 Publication Atmospheric Science Letters Abbreviated Journal Atmos. Sci. Lett.
Volume 6
Issue 1
Pages
Keywords
Abstract We present in this paper the interannual variability of seasonal temperature and rainfall in the Indian meteorological subdivisions (IMS) for boreal winter and summer seasons that take in to account the varying length of the seasons.Our study reveals that accounting for the variations in the length of the sea-sons produces stronger teleconnections between the seasonal anomalies of surface temperature and rainfall over India with corresponding sea surface temperature anomalies of the tropical Oceans (especially over the northern Indian and the equatorial Pacific Oceans) compared to the same teleconnections from fixed length seasons over the IMS. It should be noted that the IMS show significant spatial heterogeneity in these teleconnections
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1530-261X
ISBN Medium
Area Expedition Conference
Funding Approved $loc['no']
Call Number COAPS @ user @
Serial 1069
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Author Zhang, M. ; Wu, Z. ; Qiao, F.
Title Deep Atlantic Ocean Warming Facilitated by the Deep Western Boundary Current and Equatorial Kelvin Waves Type $loc['typeJournal Article']
Year 2018 Publication Journal of Climate Abbreviated Journal J. Climate
Volume 31
Issue 20
Pages 8541-8555
Keywords Ocean ; Atlantic Ocean ; Heating ; Kelvin waves ; Ocean circulation ; Oceanic variability ; EMPIRICAL MODE DECOMPOSITION ; NONSTATIONARY TIME-SERIES ; NORTH-ATLANTIC ; CLIMATE-CHANGE ; HEAT-CONTENT ; HIATUS ; VARIABILITY ; CIRCULATION ; TEMPERATURE ; PACIFIC
Abstract Increased heat storage in deep oceans has been proposed to account for the slowdown of global surface warming since the end of the twentieth century. How the imbalanced heat at the surface has been redistributed to deep oceans remains to be elucidated. Here, the evolution of deep Atlantic Ocean heat storage since 1950 on multidecadal or longer time scales is revealed. The anomalous heat in the deep Labrador Sea was transported southward by the shallower core of the deep western boundary current (DWBC). Upon reaching the equator around 1980, this heat transport route bifurcated into two, with one continuing southward along the DWBC and the other extending eastward along a narrow strip (about 4 degrees width) centered at the equator. In the 1990s and 2000s, meridional diffusion helped to spread warming in the tropics, making the eastward equatorial warming extension have a narrow head and wider tail. The deep Atlantic Ocean warming since 1950 had overlapping variability of approximately 60 years. The results suggest that the current basinwide Atlantic Ocean warming at depths of 1000-2000 m can be traced back to the subsurface warming in the Labrador Sea in the 1950s. An inference from these results is that the increased heat storage in the twenty-first century in the deep Atlantic Ocean is unlikely to partly account for the atmospheric radiative imbalance during the last two decades and to serve as an explanation for the current warming hiatus.
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Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0894-8755
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Funding Approved $loc['no']
Call Number COAPS @ user @
Serial 950
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Author Zhao, X. ; Zhou, C. ; Xu, X. ; Ye, R. ; Tian, J. ; Zhao, W.
Title Deep Circulation in the South China Sea Simulated in a Regional Model Type $loc['typeJournal Article']
Year 2019 Publication Ocean Sci. Discuss Abbreviated Journal Ocean Sci. Discuss
Volume Issue Pages
Keywords Sea Marine, Oceanography/CIMST, PacificOcean, continuous current-meter, deep circulation, deep western boundary
Abstract The South China Sea (SCS) is the largest marginal sea in the northwest Pacific Ocean. In this study, deep circulation in the SCS is investigated using results from eddy-resolving, regional simulations using the Hybrid Coordinate Ocean Model (HYCOM) verified by continuous current-meter observations. Analysis of these results provides a detailed spatial structure and temporal variability of the deep circulation in the SCS. The major features of the SCS deep circulation are a basin-scale cyclonic gyre and a concentrated deep western boundary current (DWBC). Transport of the DWBC is ∼ 2 Sv at 16.5° N with a width of ∼53 km. Flowing southwestward, the narrow DWBC becomes weaker with a wider range. The model results reveal the existence of 80- to 120-day oscillation in the deep northeastern circulation and the DWBC, which are also the areas with elevated eddy kinetic energy. This intraseasonal oscillation propagates northwestward with a velocity amplitude of ∼ 1.0 to 1.5 cm s-1. The distribution of mixing parameters in the deep SCS plays a role in both spatial structure and volume transport of the deep circulation. Compared with the northern shelf of the SCS with the Luzon Strait, deep circulation in the SCS is more sensitive to the large vertical mixing parameters of the Zhongsha Island Chain area.
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Serial 1013
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Author Zheng, Y. ; Bourassa, M. A. ; Dukhovskoy, D. S.
Title Upper-Ocean Processes Controlling the Sea Surface Temperature in the Western Gulf of Mexico Type $loc['typeAbstract']
Year 2018 Publication American Geophysical Union Abbreviated Journal AGU
Volume Fall Meeting
Issue Pages
Keywords 4299 General or miscellaneous, OCEANOGRAPHY: GENERAL
Abstract This study examines the upper-ocean processes controlling the mixed layer temperature in the western Gulf of Mexico (GOM) through estimating the contributing terms in the heat equation, with an emphasis on eddies' role. The major heat contributing terms for the upper GOM were estimated using two ocean reanalysis datasets: an eddy-resolving HYbrid Coordinate Ocean Model (HYCOM) and a Simple Ocean Data Assimilation (SODA). Analysis of net surface heat fluxes from four datasets reveals that the long-term mean net surface heat flux cools the northern GOM and warms the southern GOM. Two regions are focused for analysis: an eddy-rich region where LCEs are energetic, and the southwestern Gulf where eddy activity is relatively weak and the features of near surface temperature differ from the eddy-rich region. An eddy-rich region in the western GOM is defined based on the eddy kinetic energy derived from satellite sea surface heights. The long-term mean horizontal heat advection causes a weak warming over most of the eddy rich region, partly attributed to the flow-temperature configuration that the long-term and seasonally mean flow is nearly parallel to the corresponding mean isotherms. By contrast, the temporal mean vertical heat advection causes a strong warming in the eddy rich region, partly balancing the cooling caused by net surface heat flux. The temporal mean eddy heat flux convergence in the western GOM, whose positive and negative values are not small at some locations, appears heterogeneous in space, resulting in a small term for the western GOM when area averaged. The persistent warm water in the southwestern Gulf is primarily caused by the net warming from net surface heat flux rather than from eddies and heat advection.
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Funding Approved $loc['no']
Call Number COAPS @ user @
Serial 1007
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Author Zou, M. ; Xiong, X. ; Wu, Z. ; Li, S. ; Zhang, Y. ; Chen, L.
Title Increase of Atmospheric Methane Observed from Space-Borne and Ground-Based Measurements Type $loc['typeJournal Article']
Year 2019 Publication Remote Sensing Abbreviated Journal Remote Sensing
Volume 11
Issue 8
Pages
Keywords Methane increase trend ; Boundary layer ; Mid-upper troposphere ; Satellite ; AIRS
Abstract It has been found that the concentration of atmospheric methane (CH4) has rapidly increased since 2007 after a decade of nearly constant concentration in the atmosphere. As an important greenhouse gas, such an increase could enhance the threat of global warming. To better quantify this increasing trend, a novel statistic method, i.e. the Ensemble Empirical Mode Decomposition (EEMD) method, was used to analyze the CH4 trends from three different measurements: the mid-upper tropospheric CH4 (MUT) from the space-borne measurements by the Atmospheric Infrared Sounder (AIRS), the CH4 in the marine boundary layer (MBL) from NOAA ground-based in-situ measurements, and the column-averaged CH4 in the atmosphere (X-CH4) from the ground-based up-looking Fourier Transform Spectrometers at Total Carbon Column Observing Network (TCCON) and the Network for the Detection of Atmospheric Composition Change (NDACC). Comparison of the CH4 trends in the mid-upper troposphere, lower troposphere, and the column average from these three data sets shows that, overall, these trends agree well in capturing the abrupt CH4 increase in 2007 (the first peak) and an even faster increase after 2013 (the second peak) over the globe. The increased rates of CH4 in the MUT, as observed by AIRS, are overall smaller than CH4 in MBL and the column-average CH4. During 2009-2011, there was a dip in the increase rate for CH4 in MBL, and the MUT-CH4 increase rate was almost negligible in the mid-high latitude regions. The increase of the column-average CH4 also reached the minimum during 2009-2011 accordingly, suggesting that the trends of CH4 are not only impacted by the surface emission, however that they also may be impacted by other processes like transport and chemical reaction loss associated with [OH]. One advantage of the EEMD analysis is to derive the monthly rate and the results show that the frequency of the variability of CH4 increase rates in the mid-high northern latitude regions is larger than those in the tropics and southern hemisphere.
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Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2072-4292
ISBN Medium
Area Expedition Conference
Funding Approved $loc['no']
Call Number COAPS @ user @
Serial 1055
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Author Zou, S. ; Bower, A. ; Furey, H. ; Susan Lozier, M. ; Xu, X.
Title Redrawing the Iceland-Scotland Overflow Water pathways in the North Atlantic Type $loc['typeJournal Article']
Year 2020 Publication Abbreviated Journal Nat Commun
Volume 11
Issue 1
Pages 1890
Keywords
Abstract Iceland-Scotland Overflow Water (ISOW) is a primary deep water mass exported from the Norwegian Sea into the North Atlantic as part of the global Meridional Overturning Circulation. ISOW has historically been depicted as flowing counter-clockwise in a deep boundary current around the subpolar North Atlantic, but this single-boundary-following pathway is being challenged by new Lagrangian observations and model simulations. We show here that ISOW leaves the boundary and spreads into the interior towards the central Labrador and Irminger basins after flowing through the Charlie-Gibbs Fracture Zone. We also describe a newly observed southward pathway of ISOW along the western flank of the Mid-Atlantic Ridge. The partitioning of these pathways is shown to be influenced by deep-reaching eddies and meanders of the North Atlantic Current. Our results, in tandem with previous studies, call for a revision in the historical depiction of ISOW pathways throughout the North Atlantic.
Address Center for Ocean-Atmosphere Prediction Studies, Florida State University, Tallahassee, FL, USA
Corporate Author Thesis
Publisher Place of Publication Editor
Language English
Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2041-1723
ISBN Medium
Area Expedition Conference
Funding strtoupper('3').strtolower('2313002'); strtoupper('P').strtolower('MC7170894')
Approved $loc['no']
Call Number COAPS @ user @
Serial 1105
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Author Zou, S. ; Lozier, M.S. ; Xu, X.
Title Latitudinal Structure of the Meridional Overturning Circulation Variability on Interannual to Decadal Time Scales in the North Atlantic Ocean Type $loc['typeJournal Article']
Year 2020 Publication Journal of Climate Abbreviated Journal J. Climate
Volume 33
Issue 9
Pages 3845-3862
Keywords Deep convection ; Ocean circulation ; Thermocline circulation
Abstract The latitudinal structure of the Atlantic meridional overturning circulation (AMOC) variability in the North Atlantic is investigated using numerical results from three ocean circulation simulations over the past four to five decades. We show that AMOC variability south of the Labrador Sea (53°N) to 25°N can be decomposed into a latitudinally coherent component and a gyre-opposing component. The latitudinally coherent component contains both decadal and interannual variabilities. The coherent decadal AMOC variability originates in the subpolar region and is reflected by the zonal density gradient in that basin. It is further shown to be linked to persistent North Atlantic Oscillation (NAO) conditions in all three models. The interannual AMOC variability contained in the latitudinally coherent component is shown to be driven by westerlies in the transition region between the subpolar and the subtropical gyre (40°–50°N), through significant responses in Ekman transport. Finally, the gyre-opposing component principally varies on interannual time scales and responds to local wind variability related to the annual NAO. The contribution of these components to the total AMOC variability is latitude-dependent: 1) in the subpolar region, all models show that the latitudinally coherent component dominates AMOC variability on interannual to decadal time scales, with little contribution from the gyre-opposing component, and 2) in the subtropical region, the gyre-opposing component explains a majority of the interannual AMOC variability in two models, while in the other model, the contributions from the coherent and the gyre-opposing components are comparable. These results provide a quantitative decomposition of AMOC variability across latitudes and shed light on the linkage between different AMOC variability components and atmospheric forcing mechanisms.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0894-8755
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Call Number COAPS @ user @
Serial 1106
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