Abstract
It is strongly believed that the explosive eruptions produce negative radiative forcing that causes long-term perturbations in the ocean. Moreover, it is anticipated that a sporadic strong cooling should initiate more vigorous vertical mixing of the upper ocean, and therefore cools the ocean more effectively than a uniform radiative forcing. However, the long-term simulations show that on average the ocean heat content responses to periodic and constant forcings are comparable. To better understand this controversy and to better quantify the post-eruption oceanic response, we conducted two sets of parallel simulations, the first with a uniform/constant volcanic forcing and the second one with a periodic volcanic forcing of magnitude 1×, 5×, 10× and 30× of Pinatubo size eruption using Geophysical Fluid Dynamics Laboratory’s coupled model, CM2.1. We systematically compared the effect of periodic volcanic forcing with an equivalent time-average volcanic cooling. Our results reveal that on average, volcanic-induced perturbations in Ocean Heat Content (OHC), and sea-level rise (SLR) following uniform and periodic eruptions are almost identical. It further emphasizes that the strength of ocean heat uptake at different ocean depths is mainly driven by the strength of the Atlantic Meridional Overturning Circulation (AMOC). These findings are important for ocean initialization in long-term climate studies, and geoengineering applications. It would help to unfold uncertainties related to ocean relaxation process, heat storage, and redistribution.
Highlights
The present study investigates the long-term oceanic response to explosive volcanism of constant and periodic nature of varying magnitude
The long-term simulations show that on average the ocean heat content and sea-level rise responses to periodic and constant forcings are almost identical. To better understand this controversy, the oceanic response to periodic and energetically equivalent time-mean uniform volcanic eruptions of 1×, 5× 10× and 30× of Pinatubo size forcing is investigated with a focus on the North Atlantic Ocean, using a fully coupled atmosphere-ocean general circulation model (AOGCM), GFDL-CM2.1
The volcanic effects were evaluated using 3-member ensemble averaging that help to reduce the effect due to random noise
Summary
The present study investigates the long-term oceanic response to explosive volcanism of constant and periodic nature of varying magnitude.
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