A reconciling vision of the Adriatic-Ionian Bimodal Oscillating System.

The bimodal oscillating system (BiOS) consists in an oscillation of the Ionian Sea surface structure with period of 12-13 years, which reflects in a near-surface circulation inversion. BiOS regimes are deeply interconnected with the circulation patterns of the Eastern Mediterranean, and it is a dominant process governing water masses formation, air-sea fluxes and bio-geochemical properties, which impacts living organisms. The BiOS has been partially explained as a self-sustained oscillation maintained by the interplay between Adriatic dense water formation and changes in the relative volume of waters of Levantine and Atlantic origin entering the Adriatic; however, attempts have also been made to explain the BiOS in terms of atmospheric-related processes.

Generation of westerly wind bursts by forcing outside the tropics.

The westerly wind burst (WWB) is an important triggering mechanism of El Niño and typically occurs in the western Pacific Ocean. The Fourier spectrum of the wind field over the western tropical Pacific is characterised by a large variety of peaks distributed from intra-seasonal to decadal time scales, suggesting that WWBs could be a result of nonlinear interactions on these time scales. Using a combination of observations and simulations with 15 coupled models from the Coupled Model Intercomparison Project Phase 6 (CMIP6), we demonstrate that the main drivers initiating WWBs are quantifiable physical processes rather than atmospheric stochastic signals.