Late Miocene Arctic warmth and terrestrial climate recorded by North Greenland speleothems

The sensitivity of terrestrial Arctic climate during the Late Miocene remains poorly understood, despite this interval marking the transition towards a cooler, more variable global climate and the prelude to Northern Hemisphere glaciation. Here we present a Late Miocene terrestrial proxy record, developed through the analysis of speleothems, from eastern North Greenland (Kalaallit Nunaat). Growth periods indicate multiple episodes of permafrost absence between ~10 and 5 Ma, suggesting mean annual air temperatures ~14 °C higher than present coinciding with atmospheric CO₂ concentrations above ~310 ppm and local sea surface temperature anomalies >2 °C higher than present. Such moderate thresholds for permafrost absence highlight the climate sensitivity of North Greenland. Spikes in siliciclastic-derived trace elements ~6.3 and ~5.6 Ma are interpreted as terrestrial indicators for Late Miocene ephemeral glaciers in North Greenland. Climate variability recorded during speleothem growth periods was predominantly forced by obliquity, although, in the earliest Late Miocene, obliquity-scale anti-phasing with Antarctica may have occurred. Regional sea-ice extent was at its greatest following ~5.6 Ma during phases of transient glacial-interglacial cycles. Our findings highlight the sensitivity of the Arctic climate system and permafrost to modest CO₂ levels and provide insights into regional responses to orbital forcing.