Potential Predictability of the North Atlantic Heat Transport Based on an Oceanic State Estimate

2012 ◽  
Vol 25 (24) ◽  
pp. 8475-8486 ◽  
Author(s):  
Bente Tiedje ◽  
Armin Köhl ◽  
Johanna Baehr
Keyword(s):  
Heat Transport ◽  
North Atlantic ◽  
Initial Conditions ◽  
Meridional Overturning Circulation ◽  
Lead Times ◽  
Meridional Heat Transport ◽  
Potential Predictability ◽  
Latitude Dependence ◽  
The North ◽  
The North Atlantic

Abstract This paper investigates the potential predictability of the meridional heat transport (MHT) in the North Atlantic on interannual time scales using hindcast ensembles based on an oceanic data assimilation product. The work analyzes the prognostic potential predictability (PPP), using the ocean synthesis of the German partner of the consortium for Estimating the Circulation and Climate of the Ocean (GECCO) as initial conditions and as boundary conditions. The PPP of the MHT varies with latitude: local maxima are apparent within the subpolar and the subtropical gyres, and a minimum is apparent at the boundary between the gyres. This PPP minimum can also be seen in the PPP structure of the Atlantic meridional overturning circulation (AMOC), although it is considerably less pronounced. The decomposition of the MHT shows that within the subpolar gyre, the gyre component of the MHT influences the PPP structure of the MHT. Within the subtropical gyre, the overturning component of the MHT characterizes the PPP structure of the MHT. At the boundary between the subpolar and the subtropical gyres, the dynamics of the Ekman heat transport limit the predictable lead times of the MHT. At most latitudes, variations in the velocity field control the PPP structure of the MHT. The PPP structure of the AMOC can also be classified into gyre and gyre-boundary regimes, but the predictable lead times within the gyres are only similar to those of the overturning component of the MHT. Overall, the analysis provides a reference point for the latitude dependence of the MHT’s PPP structure and relates it to the latitude dependence of the AMOC’s PPP structure.

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 Meridional Heat Transport Variability at 26.5°N in the North Atlantic

1997 ◽  
Vol 27 (1) ◽  
pp. 153-174 ◽  
Author(s):  
Eve R. Fillenbaum ◽  
Thomas N. Lee ◽  
William E. Johns ◽  
Rainer J. Zantopp
Keyword(s):  
Heat Transport ◽  
North Atlantic ◽  
Meridional Heat Transport ◽  
The North ◽  
The North Atlantic

scholarly journals Global contributions of mesoscale dynamics to meridional heat transport

2021 ◽  
Author(s):  
Andrew Delman ◽  
Tong Lee
Keyword(s):  
Heat Transport ◽  
North Atlantic ◽  
Large Scale ◽  
Planetary Wave ◽  
Mesoscale Eddy ◽  
Instability Wave ◽  
Meridional Heat Transport ◽  
The North ◽  
Flux Variability ◽  
The North Atlantic

Abstract. Mesoscale ocean processes are prevalent in many parts of the global oceans, and may contribute substantially to the meridional movement of heat. Yet earlier global surveys of meridional heat transport (MHT) have not formally distinguished between mesoscale and large-scale contributions, or have defined eddy contributions based on temporal rather than spatial characteristics. This work uses spatial filtering methods to separate large-scale (gyre and planetary wave) contributions from mesoscale (eddy, recirculation, and tropical instability wave) contributions to MHT by extending beyond a previous effort for the North Atlantic Ocean. Overall, mesoscale temperature fluxes produce a net poleward MHT at mid-latitudes and equatorward MHT in the tropics, thereby resulting in a net divergence of heat from the subtropics. Mesoscale temperature fluxes are often concentrated near the energetic currents at western boundaries, and the temperature difference between the boundary current and its recirculation determines the direction of the mesoscale temperature flux. The mesoscale contribution to MHT yields substantially different results from temporally-based eddy contributions to MHT, with the latter contributed substantially by gyre and planetary wave motions at low latitudes. Mesoscale temperature fluxes contribute the most to interannual and decadal variability of MHT in the Southern Ocean, the tropical Indo-Pacific, and the North Atlantic. Surface eddy kinetic energy (EKE) is not a good proxy for mesoscale temperature flux variability in regions with the highest time-mean EKE, though it does explain much of the temperature flux variability in regions of modest time-mean EKE. This approach to quantifying mesoscale fluxes can be used to improve parameterizations of mesoscale effects in coarse-resolution models, and assess regional impacts of mesoscale eddies and recirculations on tracer fluxes.

scholarly journals Projected changes in the seasonal cycle of the Atlantic meridional heat transport in MPI-ESM

2016 ◽  
Author(s):  
Matthias Fischer ◽  
Daniela I. V. Domeisen ◽  
Wolfgang A. Müller ◽  
Johanna Baehr
Keyword(s):  
Heat Transport ◽  
North Atlantic ◽  
Seasonal Cycle ◽  
Coupled Model ◽  
Change Scenario ◽  
Max Planck ◽  
Meridional Heat Transport ◽  
The North ◽  
The North Atlantic ◽  
Projected Changes

Abstract. We investigate the effect of a projected reduction in the Atlantic Ocean meridional heat transport (OHT) on changes in its seasonal cycle. We analyze a climate projection experiment with the Max-Planck Institute Earth System Model (MPI-ESM) performed for the Coupled Model Intercomparison Project phase 5 (CMIP5). In the RCP8.5 climate change scenario, the OHT declines in MPI-ESM in the North Atlantic by 30–50 % by the end of the 23rd century. The decline in the OHT is accompanied by a change in the seasonal cycle of the total OHT and its components. We decompose the OHT into overturning and gyre component. For the total OHT seasonal cycle, we find a northward shift of 5 degrees and latitude dependent temporal shifts of 1 to 6 months that are mainly associated with changes in the meridional velocity field. We find that the shift in the OHT seasonal cycle predominantly results from changes in the wind-driven surface circulation which projects onto the overturning component of the OHT in the tropical and subtropical North Atlantic. This leads to latitude dependent shifts of 1 to 6 months in the overturning component. In the subpolar North Atlantic, we find that the reduction of the North Atlantic Deep Water formation in RCP8.5 and changes in the gyre heat transport result in a strongly weakened seasonal cycle with a weakened seasonal amplitude by the end of the 23rd century and thus changes the OHT seasonal cycle in the SPG.

scholarly journals Mid-Pliocene Atlantic Meridional Overturning Circulation simulated in PlioMIP2

2020 ◽  
Author(s):  
Zhongshi Zhang ◽  
Xiangyu Li ◽  
Chuncheng Guo ◽  
Odd Helge Otterå ◽  
Kerim H. Nisancioglu ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Heat Transport ◽  
North Atlantic ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Ocean Heat Transport ◽  
Surface Warming ◽  
The North ◽  
Meridional Overturning ◽  
The North Atlantic

Abstract. In the Pliocene Model Intercomparison Project phase 2 (PlioMIP2), coupled climate models have been used to simulate an interglacial climate during the mid-Piacenzian warm period (mPWP, 3.264 to 3.025 Ma). Here, we compare the Atlantic Meridional Overturning Circulation (AMOC), poleward ocean heat transport and sea surface warming in the Atlantic simulated with these models. In PlioMIP2, all models simulate an intensified mid-Pliocene AMOC. However, there is no consistent response in the simulated Atlantic ocean heat transport, or the depth of the Atlantic overturning cell. The models show a large spread in the simulated AMOC maximum, the Atlantic ocean heat transport, as well as the surface warming in the North Atlantic. Although a few models simulate a surface warming of ~ 8–12 ° in the North Atlantic, similar to the reconstruction from Pliocene Research, Interpretation and Synoptic Mapping (PRISM), most models underestimate this warming. The large model-spread and model-data discrepancies in the PlioMIP2 ensemble does not support the hypothesis that an intensification of the AMOC, together with an increase in northward ocean heat transport, is the dominant forcing for the mid-Pliocene warm climate.

Decadal predictability in the North Atlantic as seen by EC-Earth3.

2021 ◽  
Author(s):  
Bo Christiansen ◽  
Shuting Yang ◽  
Dominic Matte
Keyword(s):  
North Atlantic ◽  
Lead Time ◽  
Initial Conditions ◽  
Statistical Significance ◽  
Lead Times ◽  
The North ◽  
Weak Evidence ◽  
The North Atlantic ◽  
The Impact ◽  
Decadal Predictability

<p>We study the decadal predictability in the North Atlantic region using  ensembles of historical and decadal prediction experiments with EC-Earth3  and other CMIP models. In particular, the focus is on the NAO and the sub-polar gyre region. In general the impact of initialization is weak  for lead-times larger than one to two years and we investigate different ways to isolate and estimate the statistical significance of this impact. For the sub-polar gyre region the prediction skill is found to be mainly due to an abrupt change in the late 90ies and models disagree on whether this skill is due to forcing or initial conditions. Also the predictability of the NAO is weak and varies with lead-time and length of the predicted period. We only see weak evidence of the 'signal-to-noise paradox'. The importance of the ensemble size is also studied.                                                              </p>

scholarly journals Temperature–Salinity Structure of the North Atlantic Circulation and Associated Heat and Freshwater Transports

2016 ◽  
Vol 29 (21) ◽  
pp. 7723-7742 ◽  
Author(s):  
Xiaobiao Xu ◽  
Peter B. Rhines ◽  
Eric P. Chassignet
Keyword(s):  
Heat Transport ◽  
North Atlantic ◽  
Sea Water ◽  
Potential Temperature ◽  
Meridional Overturning Circulation ◽  
Subtropical Gyre ◽  
Western Boundary ◽  
The North ◽  
Freshwater Transport ◽  
The North Atlantic

Abstract This study investigates the circulation structure and relative contribution of circulation components to the time-mean meridional heat and freshwater transports in the North Atlantic, using numerical results of a high-resolution ocean model that are shown to be in excellent agreement with the observations. The North Atlantic circulation can be separated into the large-scale Atlantic meridional overturning circulation (AMOC) that is diapycnal and the subtropical and subpolar gyres that largely flow along isopycnal surfaces but also include prominent gyre-scale diapycnal overturning in the Subtropical Mode Water and Labrador Sea Water. Integrals of the meridional volume transport as a function of potential temperature θ and salinity S yield streamfunctions with respect to θ and to S, and heat functions. These argue for a significant contribution to the heat transport by the southward circulation of North Atlantic Deep Water. At 26.5°N, the isopycnic component of the subtropical gyre is colder and fresher in the northward-flowing western boundary currents than the southward return flows, and it carries heat southward and freshwater northward, opposite of that of the diapycnal component. When combined, the subtropical gyre contributes virtually zero to the heat transport and the AMOC is responsible for all the heat transport across this latitude. The subtropical gyre however significantly contributes to the freshwater transport, reducing the 0.5-Sv (1 Sv ≡ 106 m3 s–1) southward AMOC freshwater transport by 0.13 Sv. In the subpolar North Atlantic near 58°N, the diapycnal component of the circulation, or the transformation of warm saline upper Atlantic water into colder fresher deep waters, is responsible for essentially all of the heat and freshwater transports.

scholarly journals Initializing Decadal Climate Predictions with the GECCO Oceanic Synthesis: Effects on the North Atlantic

2009 ◽  
Vol 22 (14) ◽  
pp. 3926-3938 ◽  
Author(s):  
Holger Pohlmann ◽  
Johann H. Jungclaus ◽  
Armin Köhl ◽  
Detlef Stammer ◽  
Jochem Marotzke
Keyword(s):  
North Atlantic ◽  
Climate Model ◽  
Initial Conditions ◽  
Coupled Model ◽  
Meridional Overturning Circulation ◽  
Coupling Scheme ◽  
Max Planck ◽  
The North ◽  
The North Atlantic ◽  
Decadal Climate

Abstract This study aims at improving the forecast skill of climate predictions through the use of ocean synthesis data for initial conditions of a coupled climate model. For this purpose, the coupled model of the Max Planck Institute (MPI) for Meteorology, which consists of the atmosphere model ECHAM5 and the MPI Ocean Model (MPI-OM), is initialized with oceanic synthesis fields available from the German contribution to Estimating the Circulation and Climate of the Ocean (GECCO) project. The use of an anomaly coupling scheme during the initialization avoids the main problems with drift in the climate predictions. Thus, the coupled model is continuously forced to follow the density anomalies of the GECCO synthesis over the period 1952–2001. Hindcast experiments are initialized from this experiment at constant intervals. The results show predictive skill through the initialization up to the decadal time scale, particularly over the North Atlantic. Viewed over the time scales analyzed here (annual, 5-yr, and 10-yr mean), greater skill for the North Atlantic sea surface temperature (SST) is obtained in the hindcast experiments than in either a damped persistence or trend forecast. The Atlantic meridional overturning circulation hindcast closely follows that of the GECCO oceanic synthesis. Hindcasts of global-mean temperature do not obtain greater skill than either damped persistence or a trend forecast, owing to the SST errors in the GECCO synthesis, outside the North Atlantic. An ensemble of forecast experiments is subsequently performed over the period 2002–11. North Atlantic SST from the forecast experiment agrees well with observations until the year 2007, and it is higher than if simulated without the oceanic initialization (averaged over the forecast period). The results confirm that both the initial and the boundary conditions must be accounted for in decadal climate predictions.

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