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Author
Xiaobiao Xu, Eric Chassignet
Title
Subpolar-Subtropical Connectivity of the North Atlantic Circulation
Type
$loc['typeMiscellaneous']
Year
2019
Publication
PHYSICAL OCEANOGRAPHY
Abbreviated Journal
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Issue
Pages
Keywords
Warming, hydrographic, subtropical gyres, sub-basins, passive tracers
Abstract
The ocean, through its large capacity to store heat, plays a critical role in Earth's climate and climate variability. Warming of the world's oceans since 1955 accounts for approximately 93% of the warming of the Earth system. However, this warming is neither spatially uniform nor temporally constant. Superimposed on the global long-term trend is climate variability on inter-annual to inter-decadal time scales and regional to basin scales. Satellite altimeters and hydrographic observations show that the North Atlantic, including the sub-polar region, has rapidly become warmer and saltier since the early 1990s. An emerging picture is that the most recent 20 years or so of warming in the North Atlantic represents, in part, a transition of the Atlantic multi-decadal variability pattern from a cold to a warm phase. These decadal climate transitions involve changes both laterally in the sub-tropical and sub-polar gyres of the North Atlantic and vertically in the Atlantic Meridional Overturning Circulation (AMOC), a key component of the global heat and freshwater circulation system. This study of the North Atlantic circulation concentrates on a transition region around the Grand Banks of Newfoundland, where the effects of boundary currents and jets, recirculations, and mesoscale eddies (length scales typically less than 100 km) are dominant. Strong interactions occur in this transition region, laterally between the subpolar and subtropical gyres and vertically between the cold and warm limbs of the Atlantic Meridional Circulation (AMOC). There is evidence that this relatively compact region plays a key role in altering and even modulating the AMOC over a much larger scale and thus is important for the long-term, decadal variability of the Atlantic Ocean. Yet, despite many observational field programs, the dynamics and impacts of this region are not well understood. The project will contribute to understanding the variability of the AMOC by addressing the connectivity of the sub-polar and the sub-tropical gyres. The results of this model-data synthesis will be of particular significance to coupled climate models, which are central to understanding and predicting global climate change. The educational/outreach components of this project will be focused on cultivating scientific literacy with regards to ocean climate research in K-12 schools, at the university level, and in the local community through a variety of online resources/interactive tools for educators, the Florida State University Young Scholars program for high school students, and the “Scientists in the Schools” program. Finally, the requested funding will support a junior faculty member and a graduate student who will be trained in ocean modeling, data analysis and interpretation. Through ongoing major observation programs in the sub-polar and sub-tropical North Atlantic Ocean, oceanographers are making great strides toward a better understanding of the structure and variability of the AMOC within these sub-basins. The work proposed here complements these observations by focusing on key questions pertaining to what controls the circulation in between and how much the sub-polar to sub-tropical connectivity modulates the larger scale AMOC. This project aims to elucidate the physical dynamics that controls circulation in the transition region, especially the relative importance of the eddies and the deep western boundary current, and document the role and impact of the transition region on the larger scale circulation, especially the variability of the AMOC and water properties in the sub-polar and sub-tropical North Atlantic from inter-annual to decadal and longer time scales. The interaction of eddies and time mean circulations represents one of the greatest challenges to prediction of global climate variability, and it can be studied with the fine-grid resolution model included in this project. These objectives will be met by performing a detailed model-data synthesis study, combining numerical results from a suite of high-resolution Atlantic simulations using the HYbrid Coordinate Ocean Model (HYCOM) and existing observations (satellite altimetry, drifters/floats, hydrography, tracers, and mooring arrays). The three-dimensional Atlantic circulation will be quantified by performing analysis of water mass transport and transformation, passive tracers, and potential vorticity and momentum fluxes. It has been demonstrated that the eddy-resolving HYCOM represents the basic circulation features in the transition region and larger scale North Atlantic Ocean, including both time mean structure and temporal variability.
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Approved
$loc['no']
Call Number
COAPS @ user @
Serial
1018
Permanent link to this record
Author
LaCasce, J.H. ; Escartin, J. ; Chassignet, E.P. ; Xu, X.
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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0022-3670
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$loc['no']
Call Number
COAPS @ user @
Serial
998
Permanent link to this record
Author
Penduff, T. ; Barnier, B. ; Dewar, W.K. ; O'Brien, J.J.
Title
Dynamical Response of the Oceanic Eddy Field to the North Atlantic Oscillation: A Model-Data Comparison
Type
$loc['typeJournal Article']
Year
2004
Publication
Journal of Physical Oceanography
Abbreviated Journal
J. Phys. Oceanogr.
Volume
34
Issue
12
Pages
2615-2629
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0022-3670
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$loc['no']
Call Number
COAPS @ mfield @
Serial
455
Permanent link to this record
Author
Arruda, W. ; Zharkov, V. ; Deremble, B. ; Nof, D. ; Chassignet, E.
Title
A New Model of Current Retroflection Applied to the Westward Protrusion of the Agulhas Current
Type
$loc['typeJournal Article']
Year
2014
Publication
Journal of Physical Oceanography
Abbreviated Journal
J. Phys. Oceanogr.
Volume
44
Issue
12
Pages
3118-3138
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Abstract
Address
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Publisher
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Summary Language
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ISSN
0022-3670
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Approved
$loc['no']
Call Number
COAPS @ mfield @
Serial
122
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Author
Sturges, W. ; Bozec, A.
Title
A Puzzling Disagreement between Observations and Numerical Models in the Central Gulf of Mexico
Type
$loc['typeJournal Article']
Year
2013
Publication
Journal of Physical Oceanography
Abbreviated Journal
J. Phys. Oceanogr.
Volume
43
Issue
12
Pages
2673-2681
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Abstract
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Summary Language
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Series Editor
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Series Volume
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ISSN
0022-3670
ISBN
Medium
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Funding
Deep-C
Approved
$loc['no']
Call Number
COAPS @ mfield @
Serial
227
Permanent link to this record
Author
Bunge, L. ; Clarke, A.J.
Title
On the Warm Water Volume and Its Changing Relationship with ENSO
Type
$loc['typeJournal Article']
Year
2014
Publication
Journal of Physical Oceanography
Abbreviated Journal
J. Phys. Oceanogr.
Volume
44
Issue
5
Pages
1372-1385
Keywords
Physical Meteorology and Climatology ; Climate variability ; ENSO ; Observational techniques and algorithms ; Climate records ; Variability ; Decadal variability ; Interannual variability
Abstract
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Series Editor
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ISSN
0022-3670
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Approved
$loc['no']
Call Number
COAPS @ mfield @
Serial
156
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Author
Yan, Y. ; Chassignet, E.P. ; Qi, Y. ; Dewar, W.K.
Title
Freshening of Subsurface Waters in the Northwest Pacific Subtropical Gyre: Observations and Dynamics
Type
$loc['typeJournal Article']
Year
2013
Publication
Journal of Physical Oceanography
Abbreviated Journal
J. Phys. Oceanogr.
Volume
43
Issue
12
Pages
2733-2751
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Abstract
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0022-3670
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$loc['no']
Call Number
COAPS @ mfield @
Serial
178
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Author
Skiba, A.W. ; Zeng, L. ; Arbic, B.K. ; Müller, M. ; Godwin, W.J.
Title
On the Resonance and Shelf/Open-Ocean Coupling of the Global Diurnal Tides
Type
$loc['typeJournal Article']
Year
2013
Publication
Journal of Physical Oceanography
Abbreviated Journal
J. Phys. Oceanogr.
Volume
43
Issue
7
Pages
1301-1324
Keywords
Tides
Abstract
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Publisher
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Summary Language
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Series Editor
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ISSN
0022-3670
ISBN
Medium
Area
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Approved
$loc['no']
Call Number
COAPS @ mfield @
Serial
196
Permanent link to this record
Author
Nof, D. ; Zharkov, V. ; Arruda, W. ; Pichevin, T. ; Van Gorder, S. ; Paldor, N.
Title
Comments on “On the Steadiness of Separating Meandering Currents”
Type
$loc['typeJournal Article']
Year
2012
Publication
Journal of Physical Oceanography
Abbreviated Journal
J. Phys. Oceanogr.
Volume
42
Issue
8
Pages
1366-1370
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0022-3670
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$loc['no']
Call Number
COAPS @ mfield @
Serial
243
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Author
Nof, D. ; Jia, Y. ; Chassignet, E. ; Bozec, A.
Title
Fast Wind-Induced Migration of Leddies in the South China Sea
Type
$loc['typeJournal Article']
Year
2011
Publication
Journal of Physical Oceanography
Abbreviated Journal
J. Phys. Oceanogr.
Volume
41
Issue
9
Pages
1683-1693
Keywords
Eddies ; Seas ; gulfs ; bays ; Wind stress ; Numerical analysis/modeling ; Monsoons
Abstract
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Corporate Author
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Publisher
Place of Publication
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Summary Language
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Series Editor
Series Title
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ISSN
0022-3670
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Area
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Approved
$loc['no']
Call Number
COAPS @ mfield @
Serial
324
Permanent link to this record