The Sensitivity of Ocean Temperature, Heat Content, Sea-Level Rise, and Atlantic Meridional Overturning Circulation to Periodic and Constant Volcanic Forcing

It is strongly believed that the explosive eruptions of constant or periodic nature produce negative radiative forcing that causes long-term perturbations in the ocean. Hence, studying ocean’s sensitivity, especially the variability of the ocean’s surface and subsurface temperature, ocean heat content (OHC) and sea-level rise (SLR) following constant and periodic volcanism is of great importance. It could help to clarify uncertainties related to ocean relaxation process, heat storage, and redistribution. To better understand ocean’s sensitivity to volcanism, we systematically compared the effect of periodic volcanic forcing with an equivalent time-average volcanic cooling. It is anticipated that a sporadic strong cooling could initiate more vigorous vertical mixing of the upper ocean, and therefore cools the ocean more effectively than a uniform radiative forcing. To better understand this controversy and to better quantify the post-eruption response of ocean temperature and associated changes of OHC and SLR, we conducted two sets of parallel simulations, the first one with a uniform volcanic forcing and the second one with a periodic volcanic forcing of magnitude 1×, 5× and 10× of Pinatubo size eruption using Geophysical Fluid Dynamics Laboratory’s coupled model, CM2.1. Our results reveal that on average, volcanic induced perturbations in OHC, and SLR following uniform and periodic eruptions are almost identical. It further emphasizes that the strength of ocean heat uptake in different ocean depths is mainly driven by the strength of Atlantic Meridional Overturning Circulation (AMOC). These findings could be important for ocean initialization in long-tern climate studies and geoengineering applications.