A sediment sequence from the eastern Laptev Sea shelf (Siberian Arctic, Russia) has been studied for dinoflagellate cysts to reconstruct sea-surface conditions during the late Holocene. Variability of assemblage composition and derived sea-surface temperature estimates indicate that the neoglacial cooling was not a gradual climate change from 2510 to 900 cal yrs BP. Relatively stable conditions with temperatures that were warmer than today were punctuated by few cooling events in summer on centennial time-scales. During these events temperatures reached modern values. This suggests that modern conditions may have been abruptly established within a short period in the past 1000 years, which is not documented in our record.