Consistent Simulations of Multiple Proxy Responses to an Abrupt Climate Change Event

Ice cores, speleothems, and ocean sediment cores (proxy) records indicate an abrupt cooling approximately 8kyr ago, possibly confined to the North Atlantic region. The collapse of the Hudson Bay ice dome dam that released fresh glacial Lakes Aggasiz and Ojibway into the Hudson Bay is hypothesized to have created a slowdown in North Atlantic overturning circulation, creating this abrupt cooling. However, a lack of proxy cooling evidence within the North Atlantic has called this mechanism into question. We address the role of a slow down in deep water production in creating this type of climate change scenario by examining the impacts on the proxies themselves. In an ensemble of simulations using GISS modelE, we apply fresh water forcing to the Hudson Bay to simulate the impact of an 8k-like event on multiple proxies. The effect of this event on water isotopes is addressed using the fully coupled version of the model (atmosphere-ocean model with additional land surface and sea ice components), and the impact on cosmogenic isotopes (10Be), methane (wetland emissions), and dust are addressed using the atmosphere-only version of the model forced with the coupled model response. By comparing these modeled impacts on proxies with the proxy record at 8kyr, we find that a relatively short period of significantly diminished overturning provides a good match to the proxy record.