Dynamical dependencies at monthly and interannual time scales in the Climate system: Study of the North Pacific and Atlantic regions

Abstract

<p>The directional dependencies of different climate indices are explored using the Liang-Kleeman information flow in order to disentangle the influence of certain regions over the globe on the development of low-frequency variability of others. Seven key indices (the sea-surface temperature in El-Niño 3.4 region, the Atlantic Multidecadal Oscillation, the North Atlantic Oscillation, the North Pacific America pattern, the Arctic Oscillation, the Pacifid Decadal Oscillation, the Tropical North Atlantic index), together with three local time series located in Western Europe (Belgium), are selected. The analysis is performed on time scales from a month to 5 years by using a sliding window as filtering procedure.</p><p>A few key new results on the remote influence emerge: (i) The Arctic Oscillation plays a key role at short time (monthly) scales on the dynamics of the North Pacific and North Atlantic; (ii) the North Atlantic Oscillation is playing a global role at long time scales (several years); (iii) the Pacific Decadal Oscillation is indeed slaved to other influences; (iv) the local observables over Western Europe influence the variability on the ocean basins on long time scales. These results further illustrate the power of the Liang-Kleeman information flow in disentangling the dynamical dependencies.</p>

Assessing causal dependencies in climatic indices

“…As mentioned above the NTA index uses SST anomalies that have been smoothed thus filtering out the response to NAO. An influence of NAO on AMO and NTA was found in Vannitsem and Liang (2022), and a possible reason for the difference with our results is that the NTA index used in Vannitsem and Liang (2022) is different from the one we use here, as our index is smoothed by a 3-month window.…”

“…It was found that changes in Arctic sea ice are mainly driven by air and sea-surface temperatures and ocean heat transport. The rate of information flow was also used in Vannitsem and Liang (2022) to assess directional dependencies of seven climate indices and three local Belgium time series, on time scales from a month to five years. Among other results, the authors found that the Arctic Oscillation plays a key role on the dynamics of the North Pacific (NP) and North Atlantic (NA) on short (monthly) time scale, while NAO plays a role on long time scales (several years).…”