Remote sources for year‐to‐year changes in the seasonality of the <scp>F</scp>lorida <scp>C</scp>urrent transport

Domingues, Ricardo; Baringer, Molly O.; Goñi, Gustavo

doi:10.1002/2016jc012070

Cited by 29 publications

(43 citation statements)

References 38 publications

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“…The jet core exhibits strong seasonality, with highest core velocities in summer (–1.5 m s −1 ) and minimum in the winter (–1 m s −1 ). The same seasonality is exhibited by other WBCs, to varying degrees (Domingues et al, ; Krug & Tournadre, ). However, superimposed on this annual signal is an energetic mesoscale band at the eddy‐shedding time scale that dominates the velocity power spectrum, and a smaller peak at 20 days.…”

Section: Summary and Concluding Remarksmentioning

confidence: 99%

On the Variability of the East Australian Current: Jet Structure, Meandering, and Influence on Shelf Circulation

et al. 2017

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Given the importance of western boundary currents over a wide range of scales in the ocean, it is crucial that we understand their dynamics to accurately predict future changes. For this, we need detailed knowledge of their structure and variability. Here we investigate the jet structure of the East Australian Current (EAC), using observations from HF radars and moorings deployed at 30°S–31°S. Meandering, core velocity, width, and eddy kinetic energy (EKE) are quantified from 4 years of hourly 1.5 km resolution surface current maps (2012–2016), to obtain the most detailed representation of the surface EAC jet to date. The EAC flows predominantly over the ∼1,500 m isobath 50 km offshore but makes large amplitude displacements eastward every 65–100 days—the time scale associated with mesoscale eddy shedding at the EAC separation. Smaller‐amplitude, higher‐frequency meanders occur every 20–45 days. Using a coordinate frame that follows the jet, we show core velocity and EKE exhibit seasonality in both magnitude and variance, being maximum in summer (1.55 m s−1 mean core velocity), minimum in winter (0.8 m s−1). However, it is the eddy‐shedding time scale that dominates jet variability. As the EAC moves shoreward, shelf temperature and along‐stream velocity vary linearly with jet movement, within ∼35 km of the core. The EAC is within this range 75% of the time, demonstrating its importance to the shelf circulation. Temperature and velocity fluctuations at the 70 m (100 m) isobath are more influenced by wind (EAC encroachment), with the strongest response occurring when wind and EAC act constructively.

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Section: Summary and Concluding Remarksmentioning

confidence: 99%

On the Variability of the East Australian Current: Jet Structure, Meandering, and Influence on Shelf Circulation

et al. 2017

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“…The FC has a volume transport of~30 Sv with a standard deviation (STD) of 3 Sv (1 Sverdrup = 10 6 m 3 s À1 ; Meinen et al, 2010). Remote wind forcing, communicated via first mode baroclinic Rossby waves, has been shown to affect the annual cycle in volume transport (Domingues et al, 2016), but for the data presented here at 25-26°N, the Bahamas island chain blocks most of this direct mid-ocean influence (Archer, Shay, et al, 2017). The FC exhibits largest variability at 2-30 days, due to local and regional wind stress, and lateral meandering with an amplitude of~60 km and STD of 8 km (Archer, Shay, et al, 2017;Johns & Schott, 1987;Schott et al, 1988).…”

Section: Introductionmentioning

confidence: 99%

The Kinematic Similarity of Two Western Boundary Currents Revealed by Sustained High‐Resolution Observations

Archer

Keating

Roughan

et al. 2018

Geophysical Research Letters

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Western boundary currents (WBCs) modulate the global climate and dominate regional ocean dynamics. Despite their importance, few direct comparisons of the kinematic structure of WBCs exist, due to a lack of equivalent sustained observational data sets. Here we compare multiyear, high‐resolution observations (1 km, hourly) of surface currents in two WBCs (Florida Current and East Australian Current) upstream of their separation point. Current variability is dominated by meandering, and the WBCs exhibit contrasting time‐mean velocities in a Eulerian coordinate frame. By transforming to a jet‐following coordinate frame, we show that the time‐mean surface velocity structure of the WBC jets is remarkably similar, considering their distinct local wind, bathymetry, and meandering signals. Both WBCs show steep submesoscale kinetic energy wavenumber spectra with weak seasonal variability, in contrast to recent findings in other ocean regions. Our results suggest that it is the mesoscale flow field that controls mixing and ocean dynamics in these regions.

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“…The interactions between these two mechanisms—either constructive or destructive—lead to amplification or weakening of the annual cycle from year to year. This explains the lack of any annual cycle in the volume transport during 2006, because the SHA pattern during this period acted to reduce the summer wind‐driven peak and increase the winter minimum (see Figure b of Domingues et al, ). That the surface transport at 25.4°N does not exhibit this signal can be attributed to the blocking effect of the Bahamas topography (e.g., Anderson & Corry, ).…”

Section: Discussionmentioning

confidence: 99%

“…For instance, Meinen and Luther () showed a lack of coherence in the vertical structure of the Gulf Stream along its entire path, and in the Florida Straits they found little‐to‐no correlation between the surface and deep flows. The large year‐to‐year changes in the volume transport annual cycle of the Florida Current over the past few decades has been the focus of several recent papers that have sought to understand why it does not match the seasonal wind fields (e.g., Czeschel et al, ; Domingues et al, ; Meinen et al, ). Domingues et al () interpret the volume transport's annual cycle by separating the signal into a deterministic (fixed phase) part driven by winds, and a stochastic part driven by westward propagating sea height anomalies (SHA) from the basin interior, formed in the eastern Atlantic 4–7 years prior (their Figure ).…”

Section: Discussionmentioning

confidence: 99%

“…The large year‐to‐year changes in the volume transport annual cycle of the Florida Current over the past few decades has been the focus of several recent papers that have sought to understand why it does not match the seasonal wind fields (e.g., Czeschel et al, ; Domingues et al, ; Meinen et al, ). Domingues et al () interpret the volume transport's annual cycle by separating the signal into a deterministic (fixed phase) part driven by winds, and a stochastic part driven by westward propagating sea height anomalies (SHA) from the basin interior, formed in the eastern Atlantic 4–7 years prior (their Figure ). The interactions between these two mechanisms—either constructive or destructive—lead to amplification or weakening of the annual cycle from year to year.…”

Section: Discussionmentioning

confidence: 99%

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The Surface Velocity Structure of the Florida Current in a Jet Coordinate Frame

2017

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The structure and variability of the Florida Current between 25° and 26°N are investigated using HF radar ocean current measurements to provide the most detailed view of the surface jet to date. A 2‐D jet coordinate analysis is performed to define lateral displacements of the jet in time (meandering), and associated structural variations over a 2 year period (2005–2006). In the jet coordinate frame, core speed has a median value of ∼160 cm s−1 at the central latitude of the array (25.4°N), with a standard deviation (STD) of 35 cm s−1. The jet meanders at timescales of 3–30 days, with a STD of 8 km, and a downstream phase speed of ∼80 km d−1. Meandering accounts for ∼45% of eddy kinetic energy computed in a fixed (geographical) reference frame. Core speed, width, and shear undergo the same dominant 3–30 day variability, plus an annual cycle that matches seasonality of alongshore wind stress. Jet transport at 25.4°N exhibits a different seasonality to volume transport at 27°N, most likely driven by input from the Northwest Providence Channel. Core speed correlates inversely with Miami sea level fluctuations such that a 40 cm s−1 deceleration is associated with a ∼10 cm elevation in sea level, although there is no correlation of sea level to jet meandering or width. Such accurate quantification of the Florida Current's variability is critical to understand and forecast future changes in the climate system of the North Atlantic, as well as local impacts on coastal circulation and sea level variability along south Florida's coastline.

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Remote sources for year‐to‐year changes in the seasonality of the Florida Current transport

Cited by 29 publications

References 38 publications

On the Variability of the East Australian Current: Jet Structure, Meandering, and Influence on Shelf Circulation

On the Variability of the East Australian Current: Jet Structure, Meandering, and Influence on Shelf Circulation

The Kinematic Similarity of Two Western Boundary Currents Revealed by Sustained High‐Resolution Observations

The Surface Velocity Structure of the Florida Current in a Jet Coordinate Frame

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