Did the Hiawatha impact cause the Younger Dryas Event?

Abstract

Large impact events could cause huge environmental changes and ecological disasters on Earth. Therefore, the possibility of impact events is always considered as a potential cause of sudden climatic, environmental and ecological hazards. Vice versa, a large impact event can also be used to assess its impact on the environmental and ecological systems. In 2018, the Kjær team discovered a new 31 km diameter impact crater under the Greenland ice sheet. On the basis of regional airbone radar sounding studies, the Kjær team identified a circular depression with small peaks in the center underneath the northwest Greenland Ice Sheet. They then carried out ground-based field studies of the deglaciated forland deposits and found shocked quartz and some impact-related grains. These pieces of evidence provided compelling evidence that the depression under the ice was an impact crater (now named Hiawatha). The Hiawatha crater is now the best morphologically preserved large complex crater on Earth and it has been listed as one of the breakthrough discoveries of the year 2018 by Science. It has attracted significant attention because it's located in Greenland and its potential link with the Younger Dryas Event in the last ice age. The Younger Dryas Event is one of the most significant environmental and ecological event in the Quaternary era and the trigger for this event has been debated for a long time. According to the impact hypothesis, one or more extraterrestrial objects hit (or exploded over) the Laurentide Ice Sheet about 12900 years ago and caused extensive wildfires, megafaunal extinctions and changes in the human population. Despite much criticism initially leveled at the impact hypothesis, the controversy continues to this day and new evidence, both in favor and against the hypothesis, continues to be published. The newly discovered Hiawatha impact crater might be one more piece of evidence supporting the impact hypothesis as the trigger of the Younger Dryas Event. However, due to the lack of solid evidence supporting both a temporal correlation and a causality, the available data reported in this study could not prove that there is an unequivical causal relationship between the two events. To prove the cause and effect link between these two events, additional studies should be carried out, including: (1) To determine the time of the Hiawatha impact event; (2) to determine the distribution of Hiawatha impact ejecta and assess its environmental and ecological impacts; (3) to conduct comparative study of geological records related to the Younger Dryas Event in North America and other regions, and assess their causalities; and (4) to simulate the impact process and its climatic and environmental effects, and evaluate the possibility for causing the Younger Dryas Event and its related geologic record. In summary, the discovery of the Hiawatha crater provides an excellent frame of reference for the study of impact craters on extraterrestrial bodies. Given the importance of the impact itself and its potentially very significant effects on climate and ecological environment, the discovery and analysis underline the importance of the search for and identification of impact craters on Earth, and assessment of their potentially global geological, environmental and biological effects throughout Earth history.