Reconstructing the input of volcanic ash to the Pacific Ocean over the Cenozoic era

Volcanic ash is known to influence a range of biogeochemical processes once deposited in the oceans. These processes include the fertilisation of phytoplankton, and the enhancement of organic carbon burial, and the impact typically scales with the volume of ash. It has been shown that during periods of intense volcanic ash deposition, the impact on the ocean carbon cycle can be significant enough to cause global cooling. As a result, knowing the volume of ash entering the world’s oceans through time is vital to understanding the role explosive volcanism plays in setting global climate states. However, records of ash deposition consist of a small number of individual archives of ash input estimated via either layer counting or from multivariate statistical partitioning. Here, we compile the discontinuous and patchy records of volcanic ash deposition in the Pacific Ocean over the past 70 million years and synthesise all available data to produce a coherent record of ash accumulation rates. We show how the development of certain provinces, such as the Izu-Bonin Arc led to considerable upticks in ash input, and discuss how changing levels of ash deposition may have impacted Cenozoic climate change. Using a global biogeochemical model, we demonstrate mechanistically the role changing ash supply has in controlling global climate.