Holocene climate and environmental change in Nuup Kangerlua, southwest Greenland

The Holocene epoch offers insights into past climate variability and associated environmental changes in the Arctic region, with implications for future scenarios. We present a multi-proxy study of Nuup Kangerlua (the fjord by Nuuk), southwest Greenland, covering the past ~10,500 years. Using sediment cores and a one-year sediment trap deployment, we reconstruct environmental changes, focusing on ice-sheet dynamics, oceanography, and productivity. Following the fjord deglaciation (~10-8 ka BP), the fjord was characterised by cold, low-productivity conditions with significant ice-rafted debris, transitioning to warmer, more productive conditions by ~7.5 ka BP. The mid-to-late Holocene (6.5–3 ka BP) experienced an exceptional oceanographic regime with indication of entrainment of Subpolar Mode Water (Atlantic origin) at the time of minimum extent of the Greenland Ice Sheet. At this time, dinoflagellate cyst assemblages reveal shifts from heterotrophic dominance to autotrophic taxa, signaling increased light availability and stratification. Biogeochemical proxies (TOC, δ13C, and biogenic silica) corroborate heightened productivity during this period. Contrasts with modern conditions suggest that sustained warming could alter fjord hydrography, potentially enhancing Atlantic-derived inflows. Our study provides new knowledge on the fjord's sensitivity to climate variability and it offers baselines for understanding the interplay between the Greenland ice sheet, fjord systems, and broader oceanographic processes under changing climatic conditions.