Simulation of ash clouds after a Laacher See-type eruption

• Main Authors: Niemeier, Ulrike, Riede, Felix, Timmreck, Claudia
• Format: Text
• Language: English
• Published: 2020
• Subjects: Arctic; greenlandic
• Online Access: https://doi.org/10.5194/cp-2020-109; https://cp.copernicus.org/preprints/cp-2020-109/

Dated to ca. 13,000 years ago, the Laacher See (East Eifel Volcanic Zone) eruption was one of the largest mid-latitude Northern Hemisphere volcanic events of the Late Pleistocene. This eruptive event not only impacted local environments and human communities but also NH climate. We have simulated the evolution of the fine ash and sulfur cloud of an LSE-type eruption under present-day meteorological conditions that mirror the empirically known ash transport distribution as derived from geological, palaeo-ecological and archaeological evidence linked directly to the Late Pleistocene eruption of the Laacher See volcano. This evidence has informed our experimental set-up and we simulated corresponding eruptions of different injection altitudes (30, 60 and, 100 hPa) with varying emission strengths of sulfur and fine ash (1.5, 15, 100 Tg SO 2 ) and at different days in spring. The chosen eruption dates were determined by the stratospheric wind fields to reflect the empirically observed ash lobes. While it proved difficult to replicate the meteorological conditions that likely prevailed 13,000 years ago, our novel simulations suggest that the heating of the ash plays a crucial role for the transport of ash and sulfate. Depending on the altitude of the injection, the volcanic cloud begins to rotate one to three days after the eruption. The rotation, as well as the additional radiative heating of the fine ash, adds a southerly component to the transport vectors. This ash cloud-generated southerly migration process may at least partially explain why, as yet, no Laacher See tephra has been found in Greenlandic ice-cores. Sulfate transport, too, is impacted by the heating of the ash, resulting in a stronger transport to low-latitudes, later arrival of the volcanic cloud in the Arctic regions and, a longer lifetime. Our models throw new light on the likely behaviour of the ash cloud that darkened European skies at the end of the Pleistocene, and serve as significant input for scenarios that consider the risks associated with re-awakened volcanism in the Eifel.