Synchronized proxy-based temperature reconstructions reveal mid- to late Holocene climate oscillations in High Arctic Svalbard

Existing paleoclimate data are exceedingly sparse from southern Spitsbergen, a High Arctic region predicted to experience significant environmental changes because of amplified warming. We analyzed biotic and isotopic paleolimnological proxies to reconstruct past climate from a lacustrine sediment core, with a basal age of similar to 5500aBP, in southern Spitsbergen (77 degrees N). We used fossil Chironomidae assemblages to quantitatively reconstruct past mean July air temperatures and stable oxygen isotope values (delta O-18) of these fossils to estimate changes in mean annual air temperature. These proxy records are strikingly similar and show that the coldest anomaly since the mid-Holocene occurred between 350 and 50calaBP, during the 'Little Ice Age', whereas the warmest period in the summer temperature record occurred between 5500-5000 and similar to 2000calaBP. Our findings indicate that the natural long-term air temperature dynamics in our study area are most likely connected to solar minima and positive feedback mechanisms from sea-surface temperature maxima. The results also highlight that the recent temperature increase is unprecedented in its rate with a similar to 2 degrees C increase in the summer temperatures during the past similar to 50 years. (C) 2017 John Wiley & Sons, Ltd.Peer reviewe