The regional imprints of Dansgaard-Oeschger events on land and marine environments
Résumé
One of the most important challenges of the IPCC is documenting the regional impact of the present-day global warming. Yet, identifying the regional expression of global changes is the first and necessary step to understand the mechanisms behind them. The best examples of past global warming events, comparable in velocity and magnitude to those expected in the 21st-century, are those associated with the Dansgaard–Oeschger (D–O) cycles that punctuated the last glacial period, ~115,000-27,000 years ago (115-27 ka). Reasonably well-chronologically constrained deep-sea and terrestrial records of D-O cycles provide an excellent opportunity for documenting the nature (shape, amplitude, timing and duration) of the vegetation, fire and oceanic regional responses to past rapid global warming events. Building on the ACER (https://doi.org/10.1594/PANGAEA.870867) and PaleoJump (https://www.tipes.dk/paleojump-a-tipes-database-for-research-on-rapid-climate-transitions/) databases, I will present a new compilation of D-O records from geochemical, sedimentological and micropaleontological data. I will pay particular attention to one of the best dated event, the D-O 8, centered at ~38,000 years ago (38 ka). It followed the Heinrich Stadial 4 cold phase (~40 -38 years ago), and occurred during a period of minima in precession and intermediate ice volume (Marine Isotope Stage 3). Compared to the other D-O events, D-O 8 was marked by strong Greenland warming, ~10°C, and strong increase in atmospheric CH4 and CO2 concentrations, by at around 150 ppb and 20 ppm, respectively, and was associated with a vigorous resumption of the Atlantic Meridional Overturning Circulation. D-O 8 warming has also the advantage to be relatively recent and, therefore, one of the best recorded all around the world.