Heinrich events of the late Pleistocene; evidence from a sediment core west of Jan Mayen. An analogue to present day ice sheet collapse?

Abstract

A thorough lithological investigation of deep sea sediment core HH13-100GC has been undertaken, in order to investigate the climate and oceanographic fluctuations of the last glacial epoch. The cause of Heinrich events has remained an enigma ever since the discovery of Heinrich layers in the North Atlantic in the 1980s. Through a combination of XRF and X-ray imagery, geotechnical property investigation, ice rafted debris counts, grain size analysis, foraminiferal counts and isotopic analysis; it is possible to investigate the claims put forward so far. Here we build on others work in combination with data from HH13-100GC in order to resolve some of the questions surrounding the process of Heinrich event initiation and evolution. HH13-100GC offers a comprehensive record of climate fluctuations of the past 130, 000 cal. BP. Not only Heinrich events are represented, but also a very clear record of marine isotope stage 5, including the last interglacial, the Eemian.

Six Heinrich events spanning several thousand years were found within the 130,000 cal. BP record of HH13-100GC. Lithological investigation of ice rafted debris grains, suggests that each Heinrich event has its own IRD signature, meaning differing source regions for each event. The defining sequence of features for every Heinrich event investigated was a warm sub-surface prior to the event, indicated by a prevalence of temperate foraminifera, followed by a collapse in foraminiferal fluxes and a reduction in the efficiency of the Atlantic meridional overturning circulation, as indicated by fining of sortable silt. Sub surface warming has been used as a causative argument for present day ice sheet collapse in both Greenland and Antarctica. The author feels that investigation of Heinrich events is vital in the quest to understand the conditions we may expect from anthropogenically induced warming of the oceans, and subsequent ice sheet collapse in the present day.