Chironomid-inferred Holocene temperature changes in the South Carpathians (Romania)

We present a Holocene summer air temperature reconstruction based on fossil chironomids from Lake Brazi (1740m.a.s.l.), a shallow mountain lake in the South Carpathians. Summer air temperature reconstruction was performed using transfer functions based on the Swiss (Sw-TF) and the merged Norwegian-Swiss calibration data set (NS-TF). Our results suggest that summer air temperatures increased rapidly from the onset of the early Holocene onwards (ca. 11,500-10,200cal. yr BP), reaching close to present July air temperatures (11.2 degrees C). Between ca. 10,200 and 8500cal. yr BP mean reconstructed temperatures increased further by 1.5-2.0 degrees C. Later on, from ca. 8500cal. yr BP, chironomid-based summer temperatures started to decrease, although mean values were still above present-day temperatures. The next time period (ca. 6000-3000cal. yr BP) was cooler and with less variable temperature conditions than earlier. Afterwards (ca. 3000-2000cal. yr BP), a sharp decrease occurred in inferred temperatures with values under present-day conditions by 1.8 degrees C. Finally, in the last 2000years, reconstructed temperatures showed again an increasing trend at Lake Brazi. Short-term temperature declines of 0.6-1.2 degrees C were observed between ca. 10,350-10,190, 9750-9500, 8700-8500, 7600-7300, 7100-6900 and 4400-4000cal. yr BP. These temperature declines are, however, within the estimated error of prediction of the chironomid-based inferences. Generally, our reconstructed temperatures complied with the summer insolation curve at 45 degrees N, with other proxy-records (i.e. pollen and diatoms) from the same sediment and with other records from the Carpathians and from Western Europe.