AGU: Geophysical Research Letters

 

Editors' Highlight

Twentieth-century anthropogenic ocean warming is offset by preindustrial volcanic eruptions

Global ocean temperatures are increasing due to anthropogenic greenhouse gas warming, causing mean sea level to rise due in part to thermal expansion of the warming oceans. However, volcanic aerosols can counteract ocean warming and associated thermal expansion; they scatter and absorb sunlight, reducing the total net air-sea heat flux and result in cold surface temperature anomalies that are gradually subducted into deeper layers where they can persist for decades. Using results from recent climate modeling experiments, Gleckler et al. (2006) examined the impact of volcanic eruptions on the ocean. By analyzing different models with and without volcanic forcing, the authors discovered that the 1883 eruption of Krakatoa, which occurred before anthropogenic greenhouse gas emissions began to accelerate, limited thermal expansion of sea level well into the twentieth century. By contrast, the comparable eruptions of El Chichon (1982) and Pinatubo (1991) had much smaller cooling effects because they occurred relative to the background of large, anthropogenically forced ocean warming. The authors noted that these results illustrate the importance of preindustrial volcanic eruptions in developing simulations of twentieth-century sea level change.

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