Explosive volcanic eruptions produce very tiny particles of volcanic ash, called "tephra" that are injected into the atmosphere. If the eruption is large enough, the ash, or tephra, cloud can travel around the world, with particles being rained out of the cloud to be deposited in many settings, includingthe  land surface, oceans, and ice sheets. Deposition usually within less than a year following the eruption.  In the context of geological time, the eruption and deposition of tephra particles occur instantaneously.  Particles from a given eruption are geochemically distinctive, and can be thought of as having geochemical "fingerprints" that can be identified using microbeam geochemical techniques.

The South Pole ice core (SPICEcore) is uniquely situated to capture   volcanic particles from all regions of the Antarctic continent, as well as sub-tropical eruptions with significant global climate signatures. Twelve visible tephra layers were identified and characterized in SPICEcore and represent tephra produced by volcanoes from the Sub-Antarctic Islands (6), Marie Byrd Land (5), and one from an unknown sub-tropical eruption, likely from South America. Three of these tephra layers correlate to other ice core tephra layers providing important ?pinning points? to synchronize the climate records preserved in multiple ice cores. Two tephra layers from Marie Byrd Land correlate to WAIS Divide ice core tephra (15.226ka and 44.864ka), and one tephra erupted from the South Sandwich Island can be correlated EPICA Dome C, Vostok, and RICE (3.559ka). An additional eight cryptotephra from non-Antarctic eruptions have been characterized, and one layer geochemically correlates with the 1257 C.E. eruption of Samalas volcano in Indonesia. 

SPICEcore does not have a tephra record dominated by one volcanic region. In addition to tephra from Antarctica, the core contains tephra layers derived from off-continent volcanic sources. The far-travelled tephra layers from non-Antarctic sources improve our understanding of tephra transport to the interior of Antarctica. The location in the middle of the continent along with the longer transport distances from the local volcanoes has allowed for a unique tephra record to be produced that begins to link more of future ice core records together.

An important aspect of this project is to identify tephra from large tropical eruptions, thereby allowing positive identification and robust correlation of sulfate peaks used in ice core chronology. Volcanic-based time series are crucial for parameterization and testing of climate models, but without tephra analysis, the determinations of origins of many volcanic chemical signals remain debatable.

This project also has educational and broader impact goals. These include training a new generation of scientists in a wide array of interdisciplinary research skills including geochemistry, glaciology, paleoclimatology and computer science. This project supported five graduate students  as well as some undergraduate students. A second goal of the broader impacts component of this project was the continued efforts in fostering and promoting international cooperation in the tephra-in-ice community. Scientists Kurbatov and Dunbar have been collaborating with European tephra researchers for a number of years, sharing data and working collaboratively on tephra preparation techniques and correlations. These activities have led to, and will continue to promote, forward progress in integrating the Antarctic tephrochronology record.

Last Modified: 04/28/2022
Modified by: Nelia W Dunbar