The Icelandic Low as a Predictor of the Gulf Stream North Wall Position

Sanchez-Franks, Alejandra; Hameed, Sultan; Wilson, R. E.

doi:10.1175/jpo-d-14-0244.1

Cited by 32 publications

(28 citation statements)

References 17 publications

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“…However, the transport is characterized by a large sub-to interannual variability. The majority of studies into the variability of the Gulf Stream transport have addressed the problem in terms of whether the temporal transport variability can be explained as a response to variability in the atmospheric forcing (e.g., Anderson and Corry 1985;DiNezio et al 2009;Meinen et al 2010;Atkinson et al 2010;Sanchez-Franks et al 2016). However, no approach can explain the full variability seen in the Gulf Stream transport.…”

Section: Introductionmentioning

confidence: 99%

Loop Current Variability as Trigger of Coherent Gulf Stream Transport Anomalies

Hirschi

Frajka‐Williams

Blaker

et al. 2019

Journal of Physical Oceanography

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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 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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Section: Introductionmentioning

confidence: 99%

Loop Current Variability as Trigger of Coherent Gulf Stream Transport Anomalies

Hirschi

Frajka‐Williams

Blaker

et al. 2019

Journal of Physical Oceanography

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“…Using a multiple linear regression model for the predicted GSNW position based on prior values of the GSNW position, sea level pressure and longitude of the Icelandic Low, and the Southern Oscillation Index, Sanchez‐Franks et al . [] obtained a correlation coefficient of 0.60 with the observed GSNW position for the period 1994–2014.…”

Section: Introductionmentioning

confidence: 99%

Variability and wind forcing of ocean temperature and thermal fronts in the Slope Water region of the Northwest Atlantic

et al. 2017

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Subsurface temperatures in the Slope Water region of the Northwest Atlantic from Argo profiling floats and on the adjacent continental shelf from ship‐based measurements are compared with the latitudinal position of the Shelf‐Slope Front (SSF) and the Gulf Stream North Wall (GSNW). The Slope Water and shelf temperature anomalies at 200 m depth are in agreement for the period, 2002–2015. For the period 1978–2015, shelf temperatures are significantly correlated with the SSF position, and to a lesser extent with the GSNW position. Annual SSF position anomalies near the Grand Banks at 50°W–55°W lead anomalies to the west at 65°W–75°W by 1–2 years. Wind stress curl is compared with the annual change in the SSF and GSNW latitudinal positions, rather than with the positions directly. Changes in the mean position of the SSF are related to the wind stress curl pattern in the mid‐Atlantic, with an 8 month lag. It is suggested that a wind pattern favoring a southward shift of the SSF is associated with a southward shift of the zero‐curl line near 40°W, resulting in an expanded subpolar gyre and enhanced flow of Labrador Current Water westward from the Tail of the Grand Banks. However, changes in the GSNW position are related to an NAO‐like wind stress curl pattern in the eastern Atlantic in the winter‐spring period, in agreement with other studies. High sea surface temperatures in the Gulf of Maine and on the Scotian Shelf in recent years can be largely attributed to positive local onshore wind anomalies.

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“…The latter is a buffer zone separating the Gulf Stream from the shelf, in which subpolar and subtropical waters mix [e.g., Rossby, 1999]. Interannual variations of the Gulf Stream north wall latitude (GSNW) [Taylor and Stephens, 1998] are regulated by the large-scale pattern of wind curl over the North Atlantic through interannual changes in the strength and position of the Icelandic low and Azores high atmospheric surface pressure systems [e.g., Taylor and Stephens, 1998;Joyce et al, 2000;Sanchez-Franks et al, 2016]. The GSNW may serve as a proxy for variable slope water properties.…”

Section: Introductionmentioning

confidence: 99%

Interannual surface salinity on Northwest Atlantic shelf

et al. 2017

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Sea surface salinity (SSS) from the Aquarius and SMOS satellite missions displays a steady increase of ∼1 psu over the entire northwestern Atlantic shelf south of Nova Scotia during 2011–2015. Put in the context of longer ocean profile data, the results suggest that mixed layer salinity and temperature north of the Gulf Stream experience positively correlated shelf‐wide interannual oscillations (1 psu/2°C). Salty and warm events occur coincident with anomalous easterly‐southeasterly winds and Ekman transport counteracting the mean southwestward shelf currents. They are coincident with weakening of both branches of the Scotian Shelf Current (SSC), but only moderately correlate with shifts of the Gulf Stream North Wall. This suggests that salt advection by anomalous SSC acting on the mean salinity gradient is the primary driver regulating the transport of fresh/cold water from high latitudes. The advection mechanism imposes a connectedness of the larger‐scale interannual variability in this region and its tie to atmospheric oscillations. In the second part, an analysis of 15 year‐long numerical simulations is presented which show eight interannual salinity oscillations (positive and negative). Six of these are driven by horizontal advection by slow varying currents (>2 months), while two events are driven by horizontal eddy advection (<2 months). In line with observations, salt/warm model events correspond to anomalously weak SSC, correlate with southeasterly wind anomaly, and confirm that interannual horizontal salt advection drives interannual salinity. Indeed, vertical exchanges provide negative feedback, while interannual horizontal diffusion and the net surface salt flux anomalies are small.

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The Icelandic Low as a Predictor of the Gulf Stream North Wall Position

Cited by 32 publications

References 17 publications

Loop Current Variability as Trigger of Coherent Gulf Stream Transport Anomalies

Loop Current Variability as Trigger of Coherent Gulf Stream Transport Anomalies

Variability and wind forcing of ocean temperature and thermal fronts in the Slope Water region of the Northwest Atlantic

Interannual surface salinity on Northwest Atlantic shelf

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