Warmer and wetter past interglacials in northeast Greenland recorded in speleothems

The Arctic is particularly sensitive to climate warming and the impacts of this warming are expected to have global consequences. In order to improve understanding of the Arctic’s amplified response, it is valuable to study past interglacial periods. In contrast to existing palaeoclimate records for some areas in the Arctic, Greenland prior to 130 ka remains under-investigated. Northeast Greenland, especially, is one of the regions where the effects of Arctic amplification are particularly pronounced, both within the observational period as well as modelled future scenarios. In this study, we utilise inactive speleothems from caves in northeast Greenland (80°N) to investigate the palaeoenvironment of the region. In today’s environment, speleothem deposition is prevented by an arid climate (ca. 200 mm a^-1) and frozen ground. Accordingly, the presence of extensive speleothem deposits in the region suggests that there was at least one period of wetter and warmer climate in the recent geological past. The most recent significant speleothem deposition occurred during marine isotope stage 11 (MIS11). Prior to this, the extended MIS13-15 interglacial period was a period of exceptionally prolific speleothem deposition in northeast Greenland. During these two growth phases, the δ¹⁸O and δ¹³C variability show large centennial-scale excursions. Preliminary investigations into pollen preserved in MIS11 speleothem samples suggest an environment vastly different to today, where the landscape is mostly barren except for a few small alpine plants and shrubs. For MIS11, the samples indicate the presence of boreal coniferous species such as Picea, Abies and Pinus as well as others such as Corylus, Alnus, Ericaceae, Cyperaceae, and Poaceae. These results are in agreement with a record of MIS11 vegetation in a marine core off the coast of south Greenland, and while still being under investigation, this could imply that the reconstructed forestation of south Greenland during MIS11 reached further north. Preserved floral macrofossils and large amounts of spores in the speleothem samples indicate potential for further investigations of environmental conditions in northeast Greenland during a warmer and wetter past.