scholarly journals Aerial Observations of Symmetric Instability at the North Wall of the Gulf Stream

2018 ◽  
Vol 45 (1) ◽  
pp. 236-244 ◽  
Author(s):  
I. Savelyev ◽  
L. N. Thomas ◽  
G. B. Smith ◽  
Q. Wang ◽  
R. K. Shearman ◽  
...  
Keyword(s):  
Gulf Stream ◽  
The North ◽  
North Wall ◽  
Symmetric Instability

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

2016 ◽  
Vol 46 (3) ◽  
pp. 817-826 ◽  
Author(s):  
Alejandra Sanchez-Franks ◽  
Sultan Hameed ◽  
Robert E. Wilson
Keyword(s):  
Gulf Stream ◽  
Southern Oscillation ◽  
Time Lags ◽  
Grand Banks ◽  
The North ◽  
Cape Hatteras ◽  
Pressure Anomaly ◽  
Icelandic Low ◽  
North Wall ◽  
Wall Position

AbstractThe Gulf Stream’s north wall east of Cape Hatteras marks the abrupt change in velocity and water properties between the slope sea to the north and the Gulf Stream itself. An index of the north wall position constructed by Taylor and Stephens, called Gulf Stream north wall (GSNW), is analyzed in terms of interannual changes in the Icelandic low (IL) pressure anomaly and longitudinal displacement. Sea surface temperature (SST) composites suggest that when IL pressure is anomalously low, there are lower temperatures in the Labrador Sea and south of the Grand Banks. Two years later, warm SST anomalies are seen over the Northern Recirculation Gyre and a northward shift in the GSNW occurs. Similar changes in SSTs occur during winters in which the IL is anomalously west, resulting in a northward displacement of the GSNW 3 years later. Although time lags of 2 and 3 years between the IL and the GSNW are used in the calculations, it is shown that lags with respect to each atmospheric variable are statistically significant at the 5% level over a range of years. Utilizing the appropriate time lags between the GSNW index and the IL pressure and longitude, as well as the Southern Oscillation index, a regression prediction scheme is developed for forecasting the GSNW with a lead time of 1 year. This scheme, which uses only prior information, was used to forecast the GSNW from 1994 to 2015. The correlation between the observed and forecasted values for 1994–2014 was 0.60, significant at the 1% level. The predicted value for 2015 indicates a small northward shift of the GSNW from its 2014 position.

scholarly journals Impact of the Atlantic Meridional Mode on Gulf Stream North Wall Position

2018 ◽  
Vol 31 (21) ◽  
pp. 8875-8894 ◽  
Author(s):  
Sultan Hameed ◽  
Christopher L. P. Wolfe ◽  
Lequan Chi
Keyword(s):  
Gulf Stream ◽  
Cold Water ◽  
Meridional Overturning Circulation ◽  
Major Influence ◽  
Tropical Atlantic ◽  
The North ◽  
Meridional Mode ◽  
North Wall ◽  
Atlantic Meridional Mode ◽  
Wall Position

The path of the Gulf Stream as it leaves the continental shelf near Cape Hatteras is marked by a sharp gradient in ocean temperature known as the North Wall. Previous work in the literature has considered processes related to the North Atlantic Oscillation (NAO) in triggering latitudinal displacements of the North Wall position. This paper presents evidence that the Atlantic meridional mode (AMM) also impacts interannual variations of the North Wall position. The AMM signal from the tropics propagates to the Gulf Stream near the 200-m depth, and there are two time scales for this interaction. Anomalous Ekman suction induced by AMM cools the tropical Atlantic. The cold water in the Caribbean Sea is entrained into the currents feeding the Gulf Stream, and this cooling signal reaches the North Wall within a year. A second mechanism involves cold anomalies in the western tropical Atlantic, which initially propagate westward as baroclinic planetary waves, reaching the Gulf Stream and resulting in a southward shift in the North Wall position after a delay of about one year. In an analysis for the period 1961–2015, AMM’s signal dominates North Wall fluctuations in the upper 300 m, while NAO is the major influence below ~500 m; the influence of both the teleconnections is seen between 300 and 500 m. The relationship between the Atlantic meridional overturning circulation (AMOC) and the North Wall is investigated for the 2005–15 period and found to be statistically significant only at the sea surface in one of the three North Wall indices used.

Observations of cross-frontal exchange associated with submesoscale features along the North Wall of the Gulf Stream

2020 ◽  
Vol 163 ◽  
pp. 103342
Author(s):  
Alejandra Sanchez-Rios ◽  
R. Kipp Shearman ◽  
Jody Klymak ◽  
Eric D'Asaro ◽  
Craig Lee
Keyword(s):  
Gulf Stream ◽  
The North ◽  
North Wall

scholarly journals Interaction of Superinertial Waves with Submesoscale Cyclonic Filaments in the North Wall of the Gulf Stream

2018 ◽  
Vol 48 (1) ◽  
pp. 81-99 ◽  
Author(s):  
Daniel B. Whitt ◽  
Leif N. Thomas ◽  
Jody M. Klymak ◽  
Craig M. Lee ◽  
Eric A. D’Asaro
Keyword(s):  
Wave Propagation ◽  
Gulf Stream ◽  
Vertical Shear ◽  
Vertical Vorticity ◽  
Shear Structures ◽  
The North ◽  
Lagrangian Observations ◽  
Critical Layers ◽  
Balanced Flow ◽  
North Wall

AbstractHigh-resolution, nearly Lagrangian observations of velocity and density made in the North Wall of the Gulf Stream reveal banded shear structures characteristic of near-inertial waves (NIWs). Here, the current follows submesoscale dynamics, with Rossby and Richardson numbers near one, and the vertical vorticity is positive. This allows for a unique analysis of the interaction of NIWs with a submesoscale current dominated by cyclonic as opposed to anticyclonic vorticity. Rotary spectra reveal that the vertical shear vector rotates primarily clockwise with depth and with time at frequencies near and above the local Coriolis frequency f. At some depths, more than half of the measured shear variance is explained by clockwise rotary motions with frequencies between f and 1.7f. The dominant superinertial frequencies are consistent with those inferred from a dispersion relation for NIWs in submesoscale currents that depends on the observed aspect ratio of the wave shear as well as the vertical vorticity, baroclinicity, and stratification of the balanced flow. These observations motivate a ray tracing calculation of superinertial wave propagation in the North Wall, where multiple filaments of strong cyclonic vorticity strongly modify wave propagation. The calculation shows that the minimum permissible frequency for inertia–gravity waves is mostly greater than the Coriolis frequency, and superinertial waves can be trapped and amplified at slantwise critical layers between cyclonic vortex filaments, providing a new plausible explanation for why the observed shear variance is dominated by superinertial waves.

Air-Sea Interaction Effects in the Lower Troposphere Across the North Wall of the Gulf Stream

1981 ◽  
Vol 109 (5) ◽  
pp. 1042-1052 ◽  
Author(s):  
Wayne Sweet ◽  
Robert Fett ◽  
Jeffrey Kerling ◽  
Paul La Violette
Keyword(s):  
Gulf Stream ◽  
Lower Troposphere ◽  
Interaction Effects ◽  
The North ◽  
North Wall

Latitudinal Displacements of the Gulf Stream and the Abundance of Plankton in the North-East Atlantic

1992 ◽  
Vol 72 (4) ◽  
pp. 919-921 ◽  
Author(s):  
A. H. Taylor ◽  
J. M. Colebrook ◽  
J. A. Stephens ◽  
N. G. Baker
Keyword(s):  
Time Series ◽  
North Atlantic ◽  
Gulf Stream ◽  
Storm Tracks ◽  
British Isles ◽  
East Atlantic ◽  
North East ◽  
The North ◽  
The North Atlantic ◽  
North Wall

An earlier time-series of the annual mean latitude of the north wall of the Gulf Stream is updated to give a series of values from 1966 to 1990. The trend is similar to those seen in plankton from the Continuous Plankton Recorder Survey around the British Isles. This connection may reflect the displacement of storm tracks across the North Atlantic.

scholarly journals Seven copepod species considered as indicators of water-mass influence and changes: results from a Northumberland coastal station

2004 ◽  
Vol 61 (4) ◽  
pp. 485-491 ◽  
Author(s):  
D Bonnet ◽  
C Frid
Keyword(s):  
North Atlantic ◽  
Gulf Stream ◽  
Water Mass ◽  
Zooplankton Community ◽  
Copepod Species ◽  
Coastal Station ◽  
The North ◽  
North Wall ◽  
The North Atlantic Oscillation

Abstract Zooplankton has been sampled monthly since 1969 at Station Z off the Northumberland coast. Seven copepod species were chosen as potential indicators of specific water masses. Data have been analysed to provide information about seasonal and interannual changes in the zooplankton community with special reference to the indicator taxa and to the possible role of hydrographic and climate drivers, including variations in the position of the Gulf Stream North Wall position and the North Atlantic Oscillation. Results show that, at this Northumberland coastal station, some copepod species are likely to be good indicators of water-mass influence and changes.

scholarly journals On the Drivers of Decadal Variability of the Gulf Stream North Wall

2019 ◽  
Vol 32 (4) ◽  
pp. 1235-1249 ◽  
Author(s):  
Christopher L. P. Wolfe ◽  
Sultan Hameed ◽  
Lequan Chi
Keyword(s):  
Time Scales ◽  
Gulf Stream ◽  
Decadal Variability ◽  
Spatial Scales ◽  
Dominant Mode ◽  
The North ◽  
Wide Range ◽  
Icelandic Low ◽  
Azores High ◽  
North Wall

The Gulf Stream is bounded to the north by a strong temperature front known as the North Wall. The North Wall is subject to variability on a wide range of temporal and spatial scales—on interannual time scales, the dominant mode of variability is a longitudinally coherent north–south migration. North Wall variability since 1970 has been characterized by regular oscillations with a period of approximately nine years. This periodic variability, and its relationship to major modes of Atlantic climate variability, is examined in the frequency domain. The North Atlantic Oscillation (NAO) and the Atlantic meridional mode (AMM) both covary with the North Wall on decadal time scales. The NAO leads the North Wall by about one year, whereas the covariability between the North Wall and the AMM is synchronous (no lag). Covariability between the North Wall and the NAO is further examined in terms of the centers of action comprising the NAO: the Icelandic low and Azores high. It is found that the strength of the Icelandic low and its latitude as well as the strength of the Azores high play a role in decadal North Wall variability.

Comments on “Reconstruction of the Gulf Stream from 1940 to the Present and Correlation with the North Atlantic Oscillation”

2019 ◽  
Vol 49 (10) ◽  
pp. 2731-2734
Author(s):  
Lequan Chi ◽  
Sultan Hameed ◽  
Christopher L. P. Wolfe
Keyword(s):  
Continental Shelf ◽  
Gulf Stream ◽  
Error Function ◽  
Labrador Sea ◽  
Subjective Analysis ◽  
The North ◽  
Shelf Slope ◽  
Cape Hatteras ◽  
North Wall ◽  
The North Atlantic Oscillation

AbstractThe path of the Gulf Stream as it leaves the continental shelf near Cape Hatteras is marked by a sharp gradient in ocean temperature known as the North Wall. The latitude location of the Gulf Stream North Wall (GSNW) has previously been estimated by subjective analysis of daily maps of sea surface temperatures. Recently, Watelet et al. (2017) presented an objective procedure by fitting an error function to the SST profile across the Gulf Stream at 81 longitude positions. The fit smooths over not only the GSNW but also the much colder waters from the Labrador Sea on the continental shelf. Watelet et al.’s procedure is therefore likely to misidentify the shelf-slope front as the Gulf Stream North Wall, leading to a systematic northward bias the in North Wall position.

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