Abstract
Abstract. The oceanic response to volcanic eruptions over the last 1000 years is investigated with a focus on the North Atlantic Ocean, using a fully coupled AOGCM forced by a realistic time series of volcanic eruptions, total solar irradiance (TSI) and atmospheric greenhouse gases concentration. The model simulates little response to TSI variations but a strong and long-lasting thermal and dynamical oceanic adjustment to volcanic forcing, which is shown to be a function of the time period of the volcanic eruptions. The thermal response consists of a fast tropical cooling due to the radiative forcing by the volcanic eruptions, followed by a penetration of this cooling in the subtropical ocean interior one to five years after the eruption, and propagation of the anomalies toward the high latitudes. The oceanic circulation first adjusts rapidly to low latitude anomalous wind stress induced by the strong cooling. The Atlantic Meridional Overturning Circulation (AMOC) shows a significant intensification 5 to 10 years after the eruptions of the period post-1400 A.D., in response to anomalous atmospheric momentum forcing, and a slight weakening in the following decade. In response to the stronger eruptions occurring between 1100 and 1300, the AMOC shows no intensification and a stronger reduction after 10 years. This study thus stresses the diversity of AMOC response to volcanic eruptions in climate models and discusses possible explanations.
Highlights
In order to maximize the signal to noise ratio, we focused on relatively large eruptions, and selected eruptions corresponding to an increase of stratospheric aerosol optical depth (AOD) by more than 0.15, which is equivalent to a global radiative forcing of at least −2.8 W m−2
We focus on the response of the Atlantic Ocean, as a case study and in order to investigate the behavior of the Atlantic Meridional Overturning Circulation (AMOC)
15 In this study, we have investigated the oceanic response to volcanic eruptions over the last thousand years, with a focus on the North Atlantic Ocean
Summary
Understanding the climate fluctuations at decadal timescales and the climate response to external forcing is of prime importance to anticipate and understand future climate changes. In response to a super-eruption with 5 100 time the Pinatubo amount of sulphuric acid released in the stratosphere, Jones et al (2005) found that the AMOC doubled in intensity after nine years Both Ottera et al (2010) and Ortega et al (2011) found an intensification of the AMOC in a long simulation forced by both reconstructions of volcanic eruptions and variations in TSI. The feedback mechanism depended on other factors since it was only activated in half of the simulations In this context, it is important to highlight that while both Stenchikov et al (2009) and Ottera et al (2010) found a significant intensification of the AMOC following volcanic eruptions, the first study was based on sensitivity experiments following single eruptions of different 25 intensities and the other based on composite analysis over the last 600 years of the millennium, thereby excluding the particular succession of events of the thirteen century.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
