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Loop Current variability as trigger of coherent Gulf Stream transport anomalies

Loop Current variability as trigger of coherent Gulf Stream transport anomalies
Loop Current variability as trigger of coherent Gulf Stream transport anomalies
Satellite 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 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 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 Sv (1Sv = 106m3/s) 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.
0022-3670
Hirschi, Joël J.-m.
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Frajka-williams, Eleanor
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Blaker, Adam T.
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Sinha, Bablu
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Coward, Andrew
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Hyder, Pat
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Biastoch, Arne
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Böning, Claus
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Barnier, Bernard
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Penduff, Thierry
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Garcia, Ixetl
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Fransner, Filippa
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Madec, Gurvan
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Hirschi, Joël J.-m.
c8a45006-a6e3-4319-b5f5-648e8ef98906
Frajka-williams, Eleanor
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Blaker, Adam T.
94efe8b2-c744-4e90-87d7-db19ffa41200
Sinha, Bablu
fbb0cf78-c13b-43e0-b0ae-735ca4d4cded
Coward, Andrew
53b78140-2e65-476a-b287-e8384a65224b
Hyder, Pat
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Biastoch, Arne
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Böning, Claus
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Barnier, Bernard
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Penduff, Thierry
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Garcia, Ixetl
5fe4aed0-b388-4926-814f-372cabd31b21
Fransner, Filippa
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Madec, Gurvan
ffb28deb-4bbd-4a4c-914f-492f813e4864

Hirschi, Joël J.-m., Frajka-williams, Eleanor, Blaker, Adam T., Sinha, Bablu, Coward, Andrew, Hyder, Pat, Biastoch, Arne, Böning, Claus, Barnier, Bernard, Penduff, Thierry, Garcia, Ixetl, Fransner, Filippa and Madec, Gurvan (2019) Loop Current variability as trigger of coherent Gulf Stream transport anomalies. Journal of Physical Oceanography. (doi:10.1175/JPO-D-18-0236.1).

Record type: Article

Abstract

Satellite 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 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 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 Sv (1Sv = 106m3/s) 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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hirschi19jpo - Accepted Manuscript
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Accepted/In Press date: 23 May 2019
e-pub ahead of print date: 23 May 2019

Identifiers

Local EPrints ID: 432142
URI: https://eprints.soton.ac.uk/id/eprint/432142
ISSN: 0022-3670
PURE UUID: 287686e6-759f-43a0-bdf6-25b6d3e2f42b
ORCID for Eleanor Frajka-williams: ORCID iD orcid.org/0000-0001-8773-7838

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Date deposited: 03 Jul 2019 16:30
Last modified: 10 Dec 2019 01:40

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Contributors

Author: Joël J.-m. Hirschi
Author: Eleanor Frajka-williams ORCID iD
Author: Adam T. Blaker
Author: Bablu Sinha
Author: Andrew Coward
Author: Pat Hyder
Author: Arne Biastoch
Author: Claus Böning
Author: Bernard Barnier
Author: Thierry Penduff
Author: Ixetl Garcia
Author: Filippa Fransner
Author: Gurvan Madec

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