In the mid 80ties an environmental impact assessment in relation to deep-sea dumping of medium-to-high level radioactive waste was carried out in the eastern margins of the Mid Atlantic Ridge next to the Bay of Biscaye. In one of the box corers recovered for radionuclide analysis a volcanic rock was found that triggered interest because of an unexpected geochemical feature on its surface. Subsequent investigations on the bordering sediment layer revealed hints on a massive ice rafting event possibly released from rapidly collapsing circum-Atlantic ice shields. The search for more of these events in numerous sediment cores exhibited a total of 11 layers since the end of the Saalian/Illinoian glaciation (OIS 6/5 to 2/1). The six events identified in the period OIS 4 to 2 indicated oceanographic conditions in the Northeast Atlantic Ocean that were different to those that prevailed during most time of this glacial period. Later, several authors proposed mechanisms that could have triggered the collapses, e.g. the Binge-Purge model (MacAyeal, 1993) or, access of relatively warm water to the grounding lines in conjunction with isostatic movements (Bassis, 2017).
One of the consequences of rapid ice shield collapses is sea level rise. Paleo data report rates of up to several meters per century over a period of several centuries. The process described by Bassis et al. resembles to what nowadays can be observed along the ice margins of Greenland and the Antarctic where (man-made) warmed ocean water attacks the grounding lines. If this initiates something like a Heinrich event this is of widespread consequence for coasts, from displacement of populations to marine pollution.
Research on past Heinrich events is important for understanding the future developments of the existing ice shields and climate change.
Date, Time:18/06/2018, 16:00 h – 17:00 h
Location: Kleiner Hörsaal der Geologie (310a), Zülpicher Straße 49, Cologne
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