scholarly journals Determining the Origins of Advective Heat Transport Convergence Variability in the North Atlantic

2015 ◽  
Vol 28 (10) ◽  
pp. 3943-3956 ◽  
Author(s):  
Martha W. Buckley ◽  
Rui M. Ponte ◽  
Gaël Forget ◽  
Patrick Heimbach
Keyword(s):  
Heat Transport ◽  
Time Scales ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Heat Content ◽  
Heat Fluxes ◽  
Ocean Dynamics ◽  
The North ◽  
The North Atlantic ◽  
Advective Heat Transport

Abstract A recent state estimate covering the period 1992–2010 from the Estimating the Circulation and Climate of the Ocean (ECCO) project is utilized to quantify the roles of air–sea heat fluxes and advective heat transport convergences in setting upper-ocean heat content anomalies H in the North Atlantic Ocean on monthly to interannual time scales. Anomalies in (linear) advective heat transport convergences, as well as Ekman and geostrophic contributions, are decomposed into parts that are due to velocity variability, temperature variability, and their covariability. Ekman convergences are generally dominated by variability in Ekman mass transports, which reflect the instantaneous response to local wind forcing, except in the tropics, where variability in the temperature field plays a significant role. In contrast, both budget analyses and simple dynamical arguments demonstrate that geostrophic heat transport convergences that are due to temperature and velocity variability are anticorrelated, and thus their separate treatment is not insightful. In the interior of the subtropical gyre, the sum of air–sea heat fluxes and Ekman heat transport convergences is a reasonable measure of local atmospheric forcing, and such forcing explains the majority of H variability on all time scales resolved by ECCO. In contrast, in the Gulf Stream region and subpolar gyre, ocean dynamics are found to be important in setting H on interannual time scales. Air–sea heat fluxes damp anomalies created by the ocean and thus are not set by local atmospheric variability.

scholarly journals Impact of Anomalous Ocean Heat Transport on the North Atlantic Oscillation

2005 ◽  
Vol 18 (23) ◽  
pp. 4955-4969 ◽  
Author(s):  
Fabio D’Andrea ◽  
Arnaud Czaja ◽  
John Marshall
Keyword(s):  
North Atlantic Oscillation ◽  
Heat Transport ◽  
Time Scales ◽  
North Atlantic ◽  
Ocean Dynamics ◽  
Ocean Heat Transport ◽  
The North ◽  
The North Atlantic ◽  
Wind Driven Circulation ◽  
The North Atlantic Oscillation

Abstract Coupled atmosphere–ocean dynamics in the North Atlantic is studied by means of a simple model, featuring a baroclinic three-dimensional atmosphere coupled to a slab ocean. Anomalous oceanic heat transport due to wind-driven circulation is parameterized in terms of a delayed response to the change in wind stress curl due to the North Atlantic Oscillation (NAO). Climate variability for different strengths of ocean heat transport efficiency is analyzed. Two types of behavior are found depending on time scale. At interdecadal and longer time scales, a negative feedback is found that leads to a reduction in the spectral power of the NAO. By greatly increasing the efficiency of ocean heat transport, the NAO in the model can be made to completely vanish from the principal modes of variability at low frequency. This suggests that the observed NAO variability at these time scales must be due to mechanisms other than the interaction with wind-driven circulation. At decadal time scales, a coupled oscillation is found in which SST and geopotential height fields covary.

Micropaleontological Evidence for Increased Meridional Heat Transport in the North Atlantic Ocean During the Pliocene

Science ◽  
1992 ◽  
Vol 258 (5085) ◽  
pp. 1133-1135 ◽  
Author(s):  
H. J. Dowsett ◽  
T. M. Cronin ◽  
R. Z. Poore ◽  
R. S. Thompson ◽  
R. C. Whatley ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Heat Transport ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Meridional Heat Transport ◽  
The North ◽  
The North Atlantic

scholarly journals The Rapid Warming of the North Atlantic Ocean in the Mid-1990s in an Eddy-Permitting Ocean Reanalysis (1982–2013)

2016 ◽  
Vol 29 (15) ◽  
pp. 5417-5430 ◽  
Author(s):  
Chunxue Yang ◽  
Simona Masina ◽  
Alessio Bellucci ◽  
Andrea Storto
Keyword(s):  
Atlantic Ocean ◽  
Heat Transport ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Ocean Reanalysis ◽  
The North ◽  
Mean Temperature ◽  
The Mean ◽  
The North Atlantic ◽  
Mean State

Abstract The rapid warming in the mid-1990s in the North Atlantic Ocean is investigated by means of an eddy-permitting ocean reanalysis. Both the mean state and variability, including the mid-1990s warming event, are well captured by the reanalysis. An ocean heat budget applied to the subpolar gyre (SPG) region (50°–66°N, 60°–10°W) shows that the 1995–99 rapid warming is primarily dictated by changes in the heat transport convergence term while the surface heat fluxes appear to play a minor role. The mean negative temperature increment suggests a warm bias in the model and data assimilation corrects the mean state of the model, but it is not crucial to reconstruct the time variability of the upper-ocean temperature. The decomposition of the heat transport across the southern edge of the SPG into time-mean and time-varying components shows that the SPG warming is mainly associated with both the anomalous advection of mean temperature and the mean advection of temperature anomalies across the 50°N zonal section. The relative contributions of the Atlantic meridional overturning circulation (AMOC) and gyre circulation to the heat transport are also analyzed. It is shown that both the overturning and gyre components are relevant to the mid-1990s warming. In particular, the fast adjustment of the barotropic circulation response to the NAO drives the anomalous transport of mean temperature at the subtropical/subpolar boundary, while the slowly evolving AMOC feeds the large-scale advection of thermal anomalies across 50°N. The persistently positive phase of the NAO during the years prior to the rapid warming likely favored the cross-gyre heat transfer and the following SPG warming.

scholarly journals Analyzing the Influence of the North Atlantic Ocean Variability on the Atlantic Meridional Mode on Decadal Time Scales

Atmosphere ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 3
Author(s):  
Sandro F. Veiga ◽  
Emanuel Giarolla ◽  
Paulo Nobre ◽  
Carlos A. Nobre
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Decadal Variability ◽  
North Atlantic Ocean ◽  
Heat Content ◽  
Ocean Heat Content ◽  
Causality Analysis ◽  
Ocean Variability ◽  
The North ◽  
The North Atlantic

Important features of the Atlantic meridional mode (AMM) are not fully understood. We still do not know what determines its dominant decadal variability or the complex physical processes that sustain it. Using reanalysis datasets, we investigated the influence of the North Atlantic Ocean variability on the dominant decadal periodicity that characterizes the AMM. Statistical analyses demonstrated that the correlation between the sea surface temperature decadal variability in the Atlantic Ocean and the AMM time series characterizes the Atlantic multidecadal oscillation (AMO). This corroborates previous studies that demonstrated that the AMO precedes the AMM. A causal inference with a newly developed rigorous and quantitative causality analysis indicates that the AMO causes the AMM. To further understand the influence of the subsurface ocean on the AMM, the relationship between the ocean heat content (0–300 m) decadal variability and AMM was analyzed. The results show that although there is a significant zero-lag correlation between the ocean heat content in some regions of the North Atlantic (south of Greenland and in the eastern part of the North Atlantic) and the AMM, their cause-effect relationship on decadal time scales is unlikely. By correlating the AMO with the ocean heat content (0–300 m) decadal variability, the former precedes the latter; however, the causality analysis shows that the ocean heat content variability drives the AMO, corroborating several studies that point out the dominant role of the ocean heat transport convergence on AMO.

Nordic Seas Hydrography in the Context of Arctic and North Atlantic Ocean Dynamics

2021 ◽  
Vol 51 (1) ◽  
pp. 101-114
Author(s):  
J. S. Kenigson ◽  
M.-L. Timmermans
Keyword(s):  
Atlantic Ocean ◽  
Arctic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Ocean Dynamics ◽  
Nordic Seas ◽  
Convective Mixing ◽  
The North ◽  
Unified View ◽  
The North Atlantic

AbstractThe hydrography of the Nordic seas, a critical site for deep convective mixing, is controlled by various processes. On one hand, Arctic Ocean exports are thought to freshen the North Atlantic Ocean and the Nordic seas, as in the Great Salinity Anomalies (GSAs) of the 1970s–1990s. On the other hand, the salinity of the Nordic seas covaries with that of the Atlantic inflow across the Greenland–Scotland Ridge, leaving an uncertain role for Arctic Ocean exports. In this study, multidecadal time series (1950–2018) of the Nordic seas hydrography, Subarctic Front (SAF) in the North Atlantic Ocean [separating the water masses of the relatively cool, fresh Subpolar Gyre (SPG) from the warm, saline Subtropical Gyre (STG)], and atmospheric forcing are examined and suggest a unified view. The Nordic seas freshwater content is shown to covary on decadal time scales with the position of the SAF. When the SPG is strong, the SAF shifts eastward of its mean position, increasing the contribution of subpolar relative to subtropical source water to the Atlantic inflow, and vice versa. This suggests that Arctic Ocean fluxes primarily influence the hydrography of the Nordic seas via indirect means (i.e., by freshening the SPG). Case studies of two years with anomalous NAO conditions illustrate how North Atlantic Ocean dynamics relate to the position of the SAF (as indicated by hydrographic properties and stratification changes in the upper water column), and therefore to the properties of the Atlantic inflow and Nordic seas.

Variations of oceanic and atmospheric heat fluxes in the North Atlantic and their link to the North Atlantic Oscillation Index

2020 ◽  
Author(s):  
Diana Iakovleva ◽  
Igor Bashmachnikov
Keyword(s):  
North Atlantic ◽  
Heat Content ◽  
Heat Fluxes ◽  
Upper Ocean ◽  
Subpolar Gyre ◽  
Heat Advection ◽  
Norwegian Sea ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

<p>Interannual variations in the upper ocean heat and freshwater contents in the subpolar North Atlantic has important climatic effect. It affects the intensity of deep convection, which, in turn, forms the link between upper and deep ocean circulation of the global ocean Conveyor Belt.</p><p>The upper ocean heat content is primarily affected by two main process: by the ocean-atmosphere heat exchange and by oceanic heat advection. The intensity of both fluxes in the subpolar gyre is linked to the character of atmospheric circulation, largely determined by the phase of the North Atlantic Oscillation (NAO).</p><p>To study the interannual variability of the oceanic heat advection (in the upper 500<sup>th</sup> meters layer) we compare the results from four different data-sets: ARMOR-3D (1993-2018), SODA3.4.2 and SODA3.12.2 (1980-2017), and ORAS5 (1958-2017). The ocean-atmosphere heat exchange is accessed as the sum of the latent and the sensible heat fluxes, obtained from OAFlux data-set (1958-2016).</p><p>The oceanic heat advection to the Labrador and to the Irminger seas has high negative correlation (-0.79) with that into the Nordic Seas. During the years with high winter NAO Index (NAOI) the oceanic heat advection into the Subpolar Gyre decreases, while to the Nordic Seas – increases. These variations go in parallel with the intensification of the Norwegian, the West Spitsbergen and the slope East Greenland currents and weakening of the West Greenland and the Irminger Currents. During the years with high NAOI, the ocean heat release (both sensible and latent) over the Labrador and Irminger seas increases, but over the Norwegian Sea it decreases.</p><p>In summary, the results show that, during the positive NAO phase, the observed decrease of the heat content in the upper Labrador and Irminger seas is linked to both, a higher oceanic het release and a lower intensity of advection of warm water from the south. In the Norwegian Sea, the opposite sign of variations of the fluxes above leads to a simultaneous warming of the upper ocean.</p><p>The investigation is supported by the Russian Scientific Foundation (RSF), number of project 17-17-01151.</p><p> </p><p> </p>

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