Abstract
Abstract. The causal dependences (in a dynamical sense) between the dynamics of three different coupled ocean–atmosphere basins, the North Atlantic, the North Pacific and the tropical Pacific region (Nino3.4), have been explored using data from three reanalysis datasets, namely ORA-20C, ORAS4 and ERA-20C. The approach is based on convergent cross mapping (CCM) developed by Sugihara et al. (2012) that allows for evaluating the dependences between variables beyond the classical teleconnection patterns based on correlations. The use of CCM on these data mostly reveals that (i) the tropical Pacific (Nino3.4 region) only influences the dynamics of the North Atlantic region through its annual climatological cycle; (ii) the atmosphere over the North Pacific is dynamically forcing the North Atlantic on a monthly basis; (iii) on longer timescales (interannual), the dynamics of the North Pacific and the North Atlantic are influencing each other through the ocean dynamics, suggesting a connection through the thermohaline circulation. These findings shed a new light on the coupling between these three different regions of the globe. In particular, they call for a deep reassessment of the way teleconnections are interpreted and for a more rigorous way to evaluate dynamical dependences between the different components of the climate system.
Highlights
In environmental sciences, statistical quantities are essential tools to characterize the properties of a system, the most familiar of which are the mean, the variance and the correlation in space or time
We address the question of causality dependence between the tropical Pacific, the North Atlantic and the North Pacific coupled ocean–atmosphere dynamics at monthly to interannual timescales, in order to clarify the remote role of these different climate subsystems on the others
The analysis reveals a few very important facts that should help improving our understanding of the remote influence of large-scale dynamical processes and in particular the impact of the tropical Pacific coupled dynamics on the extratropics:
Summary
Statistical quantities are essential tools to characterize the properties of a system, the most familiar of which are the mean, the variance and the correlation in space or time. We address the question of causality dependence (in a dynamical sense) between the tropical Pacific, the North Atlantic and the North Pacific coupled ocean–atmosphere dynamics at monthly to interannual timescales, in order to clarify the remote role of these different climate subsystems on the others This will be done by first constructing low-order systems based on projections on a few Fourier modes that are assumed to dominate the dynamics in each of the basins. These differences should be associated with the different approaches to force the ocean model and reflect important uncertainties in reconstructing the past evolution of the Earth system. It will be shown that the annual cycle is affecting the CCM results and two different ways to disentangle its role in the causality analysis will be proposed
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