Mississippi River and Campeche Bank (Gulf of Mexico) Episodes of Cross-Shelf Export of Coastal Waters Observed with Satellites

The cross-shelf advection of coastal waters into the deep Gulf of Mexico is important for the transport of nutrients or potential pollutants. Twenty years of ocean color satellite imagery document such cross-shelf transport events via three export pathways in the Gulf of Mexico: from the Campeche Bank toward the central Gulf, from the Campeche Bank toward the Florida Straits, and from the Mississippi Delta to the Florida Straits. A catalog of these events was created based on the visual examination of 7280 daily satellite images. Water transport from the Campeche Bank to the central Gulf occurred frequently and with no seasonal pattern. Transport from Campeche Bank to the Florida Straits occurred episodically, when the Loop Current was retracted. Four such episodes were identified, between about December and June, in 2002, 2009, 2016, and 2017, each lasting ~3 months. Movement of Mississippi River water to the Florida Straits was more frequent and showed near seasonal occurrence, when the Loop Current was extended, while the Mississippi River discharge seems to play only a secondary role. Eight such episodes were identified—in 1999, 2000, 2003, 2004, 2006, 2011, 2014, and 2015—each lasting ~3 months during summer. The 2015 episode lasted 5 months.

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Input of Pelagic Tar into the Northwest Atlantic from the Gulf Loop Current: Chemical Characterization and its Relationship to Weathered IXTOC-I Oil

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f83-306 ◽

1983 ◽

Vol 40 (S2) ◽

pp. s12-s22 ◽

Cited By ~ 9

Author(s):

E. S. Van Vleet ◽

W. M. Sackett ◽

F. F. Weber Jr. ◽

S. B. Reinhardt

Keyword(s):

Gulf Of Mexico ◽

Mississippi River ◽

Chemical Characterization ◽

Loop Current ◽

The North ◽

Eastern Gulf Of Mexico ◽

The Caribbean ◽

Florida Straits ◽

One Year ◽

Crude Oil Sludge

Pelagic tar concentrations have been measured for samples collected monthly in the eastern Gulf of Mexico over a one year period. Analyses of the pelagic tar included gravimetric, isotopic (δ13C) and molecular (gas chromatographic) characterization of the total, aliphatic, and aromatic fractions. The concentrations of pelagic tar ranged from 0 to 26.5 mg∙m−2 of toluene extractable material, with an average of 1.60 mg∙m−2 in the offshore neuston tows and 0.05 mg∙m−2 in neuston tows taken on the west Florida continental shelf. Oblique tows to 100 m depth averaged 0.01 mg∙m−2. δ13CPDB values for the total tar in each tow averaged −27.2‰ with the aliphatic fractions averaging −27.5‰ and the aromatic fractions averaging −27.0‰. Approximately 40% of the tar samples showed a bimodal n-alkane distribution characteristic of crude oil sludge. Based upon an average annual Loop Current discharge of 28 × 106 m3∙s−1 through the Florida Straits, it is estimated that approximately 7000 t of pelagic tar are discharged annually from the Gulf of Mexico into the North Atlantic. Approximately half of this may be brought into the Gulf from the Caribbean via the Loop Current, while the remainder appears to originate in the Gulf of Mexico. Possible origins of the floating tar include input from the Caribbean Sea through the Yucatan Strait, production and transportation operations in the Gulf of Mexico, Mississippi River discharge, subsurface oil seeps, and major accidental discharges. Large amounts of oil from the IXTOC-I well blowout do not appear to have impinged on coastal waters of Florida.

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A Lagrangian approach to the Loop Current eddy separation

Nonlinear Processes in Geophysics ◽

10.5194/npg-20-85-2013 ◽

2013 ◽

Vol 20 (1) ◽

pp. 85-96 ◽

Cited By ~ 16

Author(s):

F. Andrade-Canto ◽

J. Sheinbaum ◽

L. Zavala Sansón

Keyword(s):

Numerical Model ◽

Gulf Of Mexico ◽

Caribbean Sea ◽

Separation Process ◽

Sea Surface ◽

Loop Current ◽

Hyperbolic Point ◽

Finite Time Lyapunov Exponents ◽

Florida Straits ◽

Strain Direction

Abstract. Determining when and how a Loop Current eddy (LCE) in the Gulf of Mexico will finally separate is a difficult task, since several detachment re-attachment processes can occur during one of these events. Separation is usually defined based on snapshots of Eulerian fields such as sea surface height (SSH) but here we suggest that a Lagrangian view of the LCE separation process is more appropriate and objective. The basic idea is very simple: separation should be defined whenever water particles from the cyclonic side of the Loop Current move swiftly from the Yucatan Peninsula to the Florida Straits instead of penetrating into the NE Gulf of Mexico. The properties of backward-time finite time Lyapunov exponents (FTLE) computed from a numerical model of the Gulf of Mexico and Caribbean Sea are used to estimate the "skeleton" of flow and the structures involved in LCE detachment events. An Eulerian metric is defined, based on the slope of the strain direction of the instantaneous hyperbolic point of the Loop Current anticyclone that provides useful information to forecast final LCE detachments. We highlight cases in which an LCE separation metric based on SSH contours (Leben, 2005) suggests there is a separated LCE that later reattaches, whereas the slope method and FTLE structure indicate the eddy remains dynamically connected to the Loop Current during the process.

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Loop Current Variability as Trigger of Coherent Gulf Stream Transport Anomalies

Journal of Physical Oceanography ◽

10.1175/jpo-d-18-0236.1 ◽

2019 ◽

Vol 49 (8) ◽

pp. 2115-2132 ◽

Cited By ~ 1

Author(s):

Joël J.-M. Hirschi ◽

Eleanor Frajka-Williams ◽

Adam T. Blaker ◽

Bablu Sinha ◽

Andrew Coward ◽

...

Keyword(s):

Gulf Of Mexico ◽

Gulf Stream ◽

Time Lag ◽

Ocean Model ◽

Surface Velocity ◽

Loop Current ◽

Intrinsic Variability ◽

Cape Hatteras ◽

Florida Straits ◽

Stream Transport

AbstractSatellite observations and output from a high-resolution ocean model are used to investigate how the Loop Current in the Gulf of Mexico affects the Gulf Stream transport through the Florida Straits. We find that the expansion (contraction) of the Loop Current leads to lower (higher) transports through the Straits of Florida. The associated surface velocity anomalies are coherent from the southwestern tip of Florida to Cape Hatteras. A simple continuity-based argument can be used to explain the link between the Loop Current and the downstream Gulf Stream transport: as the Loop Current lengthens (shortens) its path in the Gulf of Mexico, the flow out of the Gulf decreases (increases). Anomalies in the surface velocity field are first seen to the southwest of Florida and within 4 weeks propagate through the Florida Straits up to Cape Hatteras and into the Gulf Stream Extension. In both the observations and the model this propagation can be seen as pulses in the surface velocities. We estimate that the Loop Current variability can be linked to a variability of several Sverdrups (1Sv = 106 m3 s−1) through the Florida Straits. The exact timing of the Loop Current variability is largely unpredictable beyond a few weeks and its variability is therefore likely a major contributor to the chaotic/intrinsic variability of the Gulf Stream. However, the time lag between the Loop Current and the flow downstream of the Gulf of Mexico means that if a lengthening/shortening of the Loop Current is observed this introduces some predictability in the downstream flow for a few weeks.

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Suspended particulate matter dynamics in coastal waters from ocean color: Application to the northern Gulf of Mexico

Geophysical Research Letters ◽

10.1029/2007gl031192 ◽

2007 ◽

Vol 34 (23) ◽

pp. n/a-n/a ◽

Cited By ~ 53

Author(s):

Eurico J. D'Sa ◽

Richard L. Miller ◽

Brent A. McKee

Keyword(s):

Particulate Matter ◽

Gulf Of Mexico ◽

Suspended Particulate Matter ◽

Coastal Waters ◽

Ocean Color ◽

Northern Gulf Of Mexico ◽

Suspended Particulate

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Mississippi River water in the Florida Straits and in the Gulf Stream off Georgia in summer 2004

Geophysical Research Letters ◽

10.1029/2005gl022942 ◽

2005 ◽

Vol 32 (14) ◽

pp. n/a-n/a ◽

Cited By ~ 49

Author(s):

Chuanmin Hu ◽

James R. Nelson ◽

Elizabeth Johns ◽

Zhiqiang Chen ◽

Robert H. Weisberg ◽

...

Keyword(s):

River Water ◽

Mississippi River ◽

Gulf Stream ◽

Mississippi River Water ◽

Florida Straits

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A Trigger Mechanism for Loop Current Ring Separations

Journal of Physical Oceanography ◽

10.1175/2009jpo4245.1 ◽

2010 ◽

Vol 40 (5) ◽

pp. 900-913 ◽

Cited By ~ 20

Author(s):

Wilton Sturges ◽

Nicholas G. Hoffmann ◽

Robert R. Leben

Keyword(s):

Gulf Of Mexico ◽

Sea Level ◽

Satellite Altimetry ◽

Loop Current ◽

Trigger Mechanism ◽

Sea Levels ◽

Delay Times ◽

The Caribbean ◽

Florida Straits ◽

Current Ring

Abstract The Loop Current in the Gulf of Mexico sheds large anticyclonic rings on an irregular basis. The authors attempt to show what actually triggers the ring separations. Pulses of increased transport through the Florida Straits, as observed by the cable data, are observed prior to each ring separation. This finding is consistent over all separation events observed in the satellite altimetry record. The pulses of transport occur approximately two to four weeks before the rings separate. The increase in transport is usually accompanied by a corresponding increase in offshore sea level, suggesting forcing from the open ocean. The delay times between the pulses of increased transport and ring separations can be shown to be significantly correlated with the length of the Loop Current. Mean sea levels over the Caribbean and Gulf also peak before the separations, on average.

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