Rapid sea-level rise and climate change: lessons from the early Holocene

The `8.2 ka climate event' is believed to have been driven by meltwater pulses draining into the North Atlantic, emanating from the Laurentide Ice Sheet. It is important to quantify the precise timing and magnitude of meltwater that was released; this is critical information for climate models that simulate the impact of freshwater forcing on the Atlantic Meridional Overturning Circulation in a well-established interglacial climate state. Relative sea-level (RSL) reconstructions enable quantification of the timing and magnitude of the meltwater pulses and identification of their origin. This research presents RSL reconstructions for a North Atlantic (Ythan Estuary, UK) and a South Atlantic (Swan Inlet, Falkland Islands) site to test three hypotheses related to the meltwater pulses prior to the 8.2 ka climate event. A new inter-tidal foraminifera training set and transfer function for the North Sea basin is presented. Based on this and a high-resolution chronology, a probabilistic RSL reconstruction is produced for the Ythan Estuary 8800--8100 cal yr BP. Two meltwater pulses are quantified that demonstrate that drainage of Lake Agassiz-Ojibway (LAO) was not the major contributor of freshwater, but that the Hudson Bay Ice Saddle (HBIS) collapse was the likely major component. Twenty new sea-level index points are presented for Swan Inlet based on litho-, chrono and bio-stratigraphical analyses from c. 8500 cal yr BP to present. While there is some evidence for rapid sea-level rise coincident with the timing of the meltwater pulses, it was not possible to quantify the magnitude. The results do have important implications for understanding global ice melt history and the processes of isostatic adjustment on continental shelves. The research suggests that the HBIS was the major contributor of freshwater prior to the 8.2 ka climate event and that further work following similar lines of enquiry can help test this hypothesis.