Estimating Eddy Heat Flux from Float Data in the North Atlantic: The Impact of Temporal Sampling Interval

2007 ◽  
Vol 24 (5) ◽  
pp. 923-934 ◽  
Author(s):  
Brian S. Chinn ◽  
Sarah T. Gille
Keyword(s):  
Heat Flux ◽  
North Atlantic ◽  
Sampling Interval ◽  
Heat Fluxes ◽  
Temporal Sampling ◽  
The North ◽  
Eddy Heat Flux ◽  
Daily Sampling ◽  
The North Atlantic ◽  
The Impact

Abstract Acoustically tracked float data from 16 experiments carried out in the North Atlantic are used to evaluate the feasibility of estimating eddy heat fluxes from floats. Daily float observations were bin averaged in 2° by 2° by 200-db-deep geographic bins, and eddy heat fluxes were estimated for each bin. Results suggest that eddy heat fluxes can be highly variable, with substantial outliers that mean that fluxes do not converge quickly. If 100 statistically independent observations are available in each bin (corresponding to 500–1000 float days of data), then results predict that 80% of bins will have eddy heat fluxes that are statistically different from zero. Pop-up floats, such as Autonomous Lagrangian Circulation Explorer (ALACE) and Argo floats, do not provide daily sampling and therefore underestimate eddy heat flux. The fraction of eddy heat flux resolved using pop-up float sampling patterns decreases linearly with increasing intervals between float mapping and can be modeled analytically. This implies that flux estimates from pop-up floats may be correctable to represent true eddy heat flux.

scholarly journals The Life Cycle of the North Atlantic Storm Track*

2015 ◽  
Vol 72 (2) ◽  
pp. 821-833 ◽  
Author(s):  
Lenka Novak ◽  
Maarten H. P. Ambaum ◽  
Rémi Tailleux
Keyword(s):  
Heat Flux ◽  
Life Cycle ◽  
North Atlantic ◽  
Storm Track ◽  
High Heat ◽  
High Heat Flux ◽  
Dominant Type ◽  
The North ◽  
Eddy Heat Flux ◽  
The North Atlantic

Abstract The North Atlantic eddy-driven jet exhibits latitudinal variability with evidence of three preferred latitudinal locations: south, middle, and north. Here the authors examine the drivers of this variability and the variability of the associated storm track. The authors investigate the changes in the storm-track characteristics for the three jet locations and propose a mechanism by which enhanced storm-track activity, as measured by upstream heat flux, is responsible for cyclical downstream latitudinal shifts in the jet. This mechanism is based on a nonlinear oscillator relationship between the enhanced meridional temperature gradient (and thus baroclinicity) and the meridional high-frequency (periods of shorter than 10 days) eddy heat flux. Such oscillations in baroclinicity and heat flux induce variability in eddy anisotropy, which is associated with the changes in the dominant type of wave breaking and a different latitudinal deflection of the jet. The authors’ results suggest that high heat flux is conducive to a northward deflection of the jet, whereas low heat flux is conducive to a more zonal jet. This jet-deflecting effect was found to operate most prominently downstream of the storm-track maximum, while the storm track and the jet remain anchored at a fixed latitudinal location at the beginning of the storm track. These cyclical changes in storm-track characteristics can be viewed as different stages of the storm track’s spatiotemporal life cycle.

Air–Sea Fluxes over the Gulf Stream Region: Atmospheric Controls and Trends

2010 ◽  
Vol 23 (10) ◽  
pp. 2651-2670 ◽  
Author(s):  
Jeffrey Shaman ◽  
R. M. Samelson ◽  
Eric Skyllingstad
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
North Atlantic ◽  
Gulf Stream ◽  
Heat Fluxes ◽  
High Flux ◽  
Mode Water ◽  
The North ◽  
Storm Frequency ◽  
The North Atlantic

Abstract The intraseasonal variability of turbulent surface heat fluxes over the Gulf Stream extension and subtropical mode water regions of the North Atlantic, and long-term trends in these fluxes, are explored using NCEP–NCAR reanalysis. Wintertime sensible and latent heat fluxes from these surface waters are characterized by episodic high flux events due to cold air outbreaks from North America. Up to 60% of the November–March (NDJFM) total sensible heat flux and 45% of latent heat flux occurs on these high flux days. On average 41% (34%) of the total NDJFM sensible (latent) heat flux takes place during just 17% (20%) of the days. Over the last 60 years, seasonal NDJFM sensible and latent heat fluxes over the Climate Variability and Predictability (CLIVAR) Mode Water Dynamic Experiment (CLIMODE) region have increased owing to an increased number of high flux event days. The increased storm frequency has altered average wintertime temperature conditions in the region, producing colder surface air conditions over the North American eastern seaboard and Labrador Sea and warmer temperatures over the Sargasso Sea. These temperature changes have increased low-level vertical wind shear and baroclinicity along the North Atlantic storm track over the last 60 years and may further favor the trend of increasing storm frequency over the Gulf Stream extension and adjacent region.

scholarly journals Mechanisms Determining the Winter Atmospheric Response to the Atlantic Overturning Circulation

2016 ◽  
Vol 29 (10) ◽  
pp. 3767-3785 ◽  
Author(s):  
G. Gastineau ◽  
B. L’Hévéder ◽  
F. Codron ◽  
C. Frankignoul
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
North Atlantic ◽  
Meridional Overturning Circulation ◽  
Late Winter ◽  
Atmospheric Response ◽  
Overturning Circulation ◽  
The North ◽  
Eddy Heat Flux ◽  
The North Atlantic

Abstract In climate models, an intensification of the Atlantic meridional overturning circulation (AMOC) precedes a warming in the North Atlantic subpolar basin by a few years. In the IPSL-CM5A-LR model, this warming may explain the atmospheric response to the AMOC observed in winter, which resembles a negative phase of the North Atlantic Oscillation (NAO). To firmly establish the causality links between the ocean and the atmosphere and illustrate the underlying mechanisms in this model, ensembles of atmosphere-only simulations are conducted, prescribing the SST and sea ice anomalies that follow an AMOC intensification. In late winter, the North Atlantic SST and sea ice anomalies drive atmospheric circulation anomalies similar to those found in the coupled model. Simulations only driven by the SST anomalies related to the AMOC show that the largest oceanic influence is due to the warm subpolar SST anomaly, which enhances the oceanic heat release and decreases the lower-tropospheric baroclinicity in the region of maximum eddy growth, resulting in a weaker meridional eddy heat flux in the atmosphere. The transient eddy feedback leads to a negative NAO-like response. An AMOC intensification is also followed by less sea ice over the Labrador Sea and more sea ice over the Nordic seas. The simulations with full boundary forcing suggest that such anomalies act to strengthen both the poleward momentum flux and the upward heat flux into the polar stratosphere and lead to a stratospheric warming, which then reinforces the negative NAO signal in late winter.

scholarly journals A Regime Perspective on the North Atlantic Eddy-Driven Jet Response to Sudden Stratospheric Warmings

2020 ◽  
Vol 33 (9) ◽  
pp. 3901-3917 ◽  
Author(s):  
Amanda C. Maycock ◽  
Gibbon I. T. Masukwedza ◽  
Peter Hitchcock ◽  
Isla R. Simpson
Keyword(s):  
North Atlantic ◽  
Middle Atmosphere ◽  
Heat Fluxes ◽  
Intrinsic Variability ◽  
The South ◽  
Reanalysis Dataset ◽  
Atlantic Sector ◽  
The North ◽  
Eddy Heat Flux ◽  
The North Atlantic

AbstractChanges to the preferred states, or regime behavior, of the North Atlantic eddy-driven jet (EDJ) following a major sudden stratospheric warming (SSW) is examined using a large ensemble experiment from the Canadian Middle Atmosphere Model in which the stratosphere is nudged toward an SSW. In the 3 months following the SSW (January–March), the North Atlantic EDJ shifts equatorward by ~3°, on average; this arises from an increased occurrence of the EDJ’s south regime and reductions in its north and central regimes. Qualitatively similar behavior is shown in a reanalysis dataset. We show that under SSW conditions the south regime becomes more persistent and that this can explain the overall increase in the EDJ latitude decorrelation time scale. A cluster analysis reveals that, following the SSW, the south EDJ regime is characterized by weaker low-level baroclinicity and eddy heat fluxes in the North Atlantic Ocean. We hypothesize, therefore, that the increased persistence of the south regime is related to the weaker baroclinicity leading to slower growth rates of the unstable modes and hence a slower buildup of eddy heat flux, which has been shown to precede EDJ transitions. In the North Atlantic sector, the surface response to the SSW projects onto a negative North Atlantic Oscillation (NAO) pattern, with almost no change in the east Atlantic (EA) pattern. This behavior appears to be distinct from the modeled intrinsic variability in the EDJ, where the jet latitude index captures variations in both the NAO and EA patterns. The results offer new insight into the mechanisms for stratosphere–troposphere coupling following SSWs.

Preaching and Sermons

2017 ◽  
Author(s):  
Robert H. Ellison
Keyword(s):  
Eighteenth Century ◽  
North Atlantic ◽  
Religious Revival ◽  
Early Nineteenth Century ◽  
Denominational Identity ◽  
The North ◽  
The North Atlantic ◽  
The One ◽  
The Impact

Prompted by the convulsions of the late eighteenth century and inspired by the expansion of evangelicalism across the North Atlantic world, Protestant Dissenters from the 1790s eagerly subscribed to a millennial vision of a world transformed through missionary activism and religious revival. Voluntary societies proliferated in the early nineteenth century to spread the gospel and transform society at home and overseas. In doing so, they engaged many thousands of converts who felt the call to share their experience of personal conversion with others. Though social respectability and business methods became a notable feature of Victorian Nonconformity, the religious populism of the earlier period did not disappear and religious revival remained a key component of Dissenting experience. The impact of this revitalization was mixed. On the one hand, growth was not sustained in the long term and, to some extent, involvement in interdenominational activity undermined denominational identity; on the other hand, Nonconformists gained a social and political prominence they had not enjoyed since the middle of the seventeenth century and their efforts laid the basis for the twentieth-century explosion of evangelicalism in Africa, Asia, and South America.

REGIONAL SECURITY DYNAMICS IN NORTHERN EUROPE (ON THE EXAMPLE OF NORWAY) IN THE LIGHT OF RECENT CHANGES

2020 ◽  
Vol 73 (1) ◽  
pp. 103-111
Author(s):  
D. Kalibekuly ◽  
◽  
Y.S. Chukubayev ◽  
Keyword(s):  
North Atlantic ◽  
Member Country ◽  
Security Policy ◽  
Security System ◽  
Regional Security ◽  
Northern Europe ◽  
The North ◽  
The North Atlantic ◽  
The Impact

The paper examines the dynamics of regional security in Norway as a part of Northern Europe. Being a political and geographical part of the Euro-Atlantic security system. Northern Europe, in its turn, is experiencing the impact of the confrontation between Russia and NATO. Norway's security policy analyzed from the perspective of a regional leader, as a NATO member country participating in the operations of the North Atlantic Alliance and as NATO's northern wing.

scholarly journals The North Atlantic Eddy Heat Transport and Its Relation with the Vertical Tilting of the Gulf Stream Axis

2017 ◽  
Vol 47 (6) ◽  
pp. 1281-1289 ◽  
Author(s):  
A. M. Treguier ◽  
C. Lique ◽  
J. Deshayes ◽  
J. M. Molines
Keyword(s):  
Numerical Model ◽  
Heat Transport ◽  
North Atlantic ◽  
Gulf Stream ◽  
Mean Flow ◽  
The North ◽  
Spatial Shift ◽  
Eddy Heat Flux ◽  
Eddy Heat Transport ◽  
The North Atlantic

AbstractCorrelations between temperature and velocity fluctuations are a significant contribution to the North Atlantic meridional heat transport, especially at the northern boundary of the subtropical gyre. In satellite observations and in a numerical model at ⅞° resolution, a localized pattern of positive eddy heat flux is found northwest of the Gulf Stream, downstream of its separation at Cape Hatteras. It is confined to the upper 500 m. A simple kinematic model of a meandering jet can explain the surface eddy flux, taking into account a spatial shift between the maximum velocity of the jet and the maximum cross-jet temperature gradient. In the Gulf Stream such a spatial shift results from the nonlinear temperature profile and the vertical tilting of the velocity profile with depth. The numerical model suggests that the meandering of the Gulf Stream could account, at least in part, for the large eddy heat transport (of order 0.3 PW) near 36°N in the North Atlantic and for its compensation by the mean flow.

scholarly journals External forcing mechanisms controlling the North Atlantic coastal upwelling regime during the mid-Holocene

Geology ◽  
2020 ◽  
Author(s):  
Armand Hernández ◽  
Mário Cachão ◽  
Pedro Sousa ◽  
Ricardo M. Trigo ◽  
Jürg Luterbacher ◽  
...  
Keyword(s):  
North Atlantic ◽  
Coastal Upwelling ◽  
Marine Ecosystem ◽  
External Forcing ◽  
The North ◽  
New Findings ◽  
The North Atlantic ◽  
Eastern North Atlantic ◽  
Forcing Mechanisms ◽  
The Impact

Nearshore upwelling along the eastern North Atlantic margin regulates regional marine ecosystem productivity and thus impacts blue economies. While most global circulation models show an increase in the intensity and duration of seasonal upwelling at high latitudes under future human-induced warmer conditions, projections for the North Atlantic are still ambiguous. Due to the low temporal resolution of coastal upwelling records, little is known about the impact of natural forcing mechanisms on upwelling variability. Here, we present a microfossil-based proxy record and modeling simulations for the warmest period of the Holocene (ca. 9–5 ka) to estimate the contribution of the natural variability in North Atlantic upwelling via atmospheric and oceanic dynamics. We found that more frequent high-pressure conditions in the eastern North Atlantic associated with solar activity and orbital parameters triggered upwelling variations at multidecadal and millennial time scales, respectively. Our new findings offer insights into the role of external forcing mechanisms in upwelling changes before the Anthropocene, which must be considered when producing future projections of midlatitude upwelling activity.

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