Interdecadal variability in an idealized model of the North Atlantic

1994 ◽  
Vol 99 (C6) ◽  
pp. 12423 ◽  
Author(s):  
Andrew J. Weaver ◽  
Stella M. Aura ◽  
Paul G. Myers
Keyword(s):  
North Atlantic ◽  
Interdecadal Variability ◽  
Idealized Model ◽  
The North ◽  
The North Atlantic

scholarly journals Interdecadal Variability of the Warm Arctic and Cold Eurasia Pattern and Its North Atlantic Origin

2018 ◽  
Vol 31 (15) ◽  
pp. 5793-5810 ◽  
Author(s):  
Mi-Kyung Sung ◽  
Seon-Hwa Kim ◽  
Baek-Min Kim ◽  
Yong-Sang Choi
Keyword(s):  
Twentieth Century ◽  
Rossby Wave ◽  
North Atlantic ◽  
Storm Track ◽  
Stationary Wave ◽  
Interdecadal Variability ◽  
Temperature Perturbation ◽  
Mean Flow ◽  
The North ◽  
The North Atlantic

This study investigates the origin of the interdecadal variability in the warm Arctic and cold Eurasia (WACE) pattern, which is defined as the second empirical orthogonal function of surface air temperature (SAT) variability over the Eurasian continent in Northern Hemisphere winter, by analyzing the Twentieth Century Reanalysis dataset. While previous studies highlight recent enhancement of the WACE pattern, ascribing it to anthropogenic warming, the authors found that the WACE pattern has experienced a seemingly periodic interdecadal variation over the twentieth century. This long-term variation in the Eurasian SAT is attributable to the altered coupling between the Siberian high (SH) and intraseasonal Rossby wave emanating from the North Atlantic, as the local wave branch interacts with the SH and consequentially enhances the continental temperature perturbation. It is further identified that these atmospheric circulation changes in Eurasia are largely controlled by the decadal amplitude modulation of the climatological stationary waves over the North Atlantic region. The altered decadal mean condition of stationary wave components brings changes in local baroclinicity and storm track activity over the North Atlantic, which jointly change the intraseasonal Rossby wave generation and propagation characteristics as well. With simple stationary wave model experiments, the authors confirm how the altered mean flow condition in the North Atlantic acts as a source for the growth of the Rossby wave that leads to the change in the downstream WACE pattern.

scholarly journals The Internal Generation of the Atlantic Ocean Interdecadal Variability

2018 ◽  
Vol 31 (16) ◽  
pp. 6411-6432 ◽  
Author(s):  
Olivier Arzel ◽  
Thierry Huck ◽  
Alain Colin de Verdière
Keyword(s):  
Spatial Structure ◽  
North Atlantic ◽  
Meridional Overturning Circulation ◽  
Sea Surface ◽  
Interdecadal Variability ◽  
North Atlantic Current ◽  
Temperature Anomalies ◽  
The North ◽  
The North Atlantic ◽  
Atlantic Current

Abstract Numerical simulations of a realistic ocean general circulation model forced by prescribed surface fluxes are used to study the origin and structure of intrinsic interdecadal variability of the ocean circulation. When eddy-induced turbulent diffusivities are low enough, spontaneous oscillations of the Atlantic meridional overturning circulation (AMOC) with periods O(20) yr and amplitude O(1) Sv (1 Sv ≡ 106 m3 s−1) emerge. The transition from the steady to the oscillatory regime is shown to be consistent with a supercritical Hopf bifurcation of the horizontal Peclet number. Adding atmospheric thermal damping is shown to have a very limited influence on the domain of existence of intrinsic variability. The spatial structure of the mode consists of a dipole of sea surface temperature (SST)/sea surface height (SSH) anomalies centered at about 50°N with stronger variance in the western part of the subpolar gyre, in agreement with the observed Atlantic multidecadal oscillation (AMO) signature in this region. Specific features include a westward propagation of temperature anomalies from the source region located on the western flank of the North Atlantic Current (NAC) and a one-quarter phase lag between surface and subsurface (800 m) temperature anomalies. Local linear stability calculations including viscous and diffusive effects confirm that the North Atlantic Current is baroclinically unstable on scales of O(1000) km with growth rates of O(1) yr−1. Both the spatial structure of the mode and the period agree in magnitude with in situ measurements in the North Atlantic, suggesting that this intrinsic ocean mode participates in the observed Atlantic bidecadal climate variability.

scholarly journals Identification of the Mechanism of Interdecadal Variability in the North Atlantic Ocean

2004 ◽  
Vol 34 (12) ◽  
pp. 2792-2807 ◽  
Author(s):  
Lianke te Raa ◽  
Jeroen Gerrits ◽  
Henk A. Dijkstra
Keyword(s):  
Atlantic Ocean ◽  
Ocean Circulation ◽  
North Atlantic ◽  
Physical Mechanism ◽  
North Atlantic Ocean ◽  
Bottom Topography ◽  
Interdecadal Variability ◽  
Geophysical Fluid Dynamics Laboratory ◽  
The North ◽  
The North Atlantic

Abstract The aim of this paper is to identify the physical mechanism of interdecadal variability in simulations of the North Atlantic Ocean circulation with the Modular Ocean Model of the Geophysical Fluid Dynamics Laboratory. To that end, a hierarchy of increasingly complex model configurations is used. The variability in the simplest case, that of viscous, purely thermally driven flows in a flat-bottom ocean basin with a box-shaped geometry, is shown to be caused by an internal interdecadal mode. The westward propagation of temperature anomalies and the phase difference between the anomalous zonal and meridional overturning that characterize the interdecadal mode are used as “fingerprints” of the physical mechanism of the variability. In this way, the variability can be followed toward a less viscous regime in which the effects of continental geometry and bottom topography are also included. It is shown that, although quantitative aspects of the variability like period and spatial pattern are changing, the physical mechanism of the interdecadal variability in the more complex simulations can be attributed to the same processes as in the simplest model configuration.

Constructing an idealized model of the North Atlantic Ocean using slippery sacks

2009 ◽  
Vol 27 (3-4) ◽  
pp. 143-159 ◽  
Author(s):  
Patrick T. Haertel ◽  
Luke Van Roekel ◽  
Tommy G. Jensen
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Idealized Model ◽  
The North ◽  
The North Atlantic
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