A pan-European summer teleconnection mode recorded by a new temperature reconstruction from the northeastern Mediterranean (ad 1768-2008)

The dominant atmospheric circulation pattern that governs European summer climate is a blocking-like pattern over the British Isles that co-occurs with a low over southeastern Europe. The meridionally oriented configuration of this circulation pattern favours the intrusion of warm air over the northeastern Mediterranean during one mode and over northwestern Europe during its opposite mode. We present a summer temperature reconstruction (1768-2008) for the southeastern node of this teleconnection pattern. This reconstruction is based on maximum latewood density (MXD) measurements of 23 Pinus heldreichii trees from a high-elevation stand in the Pirin Mountains in Bulgaria. The temperature signal in trees from high-elevation, summer-dry regions is stronger in MXD measurements compared with tree-ring width data and our reconstruction reflects well interannual- to decadal-scale summer temperature fluctuations in the Balkans as instrumentally recorded over the twentieth century. Fluctuations in our Bulgarian reconstruction correspond to summer temperature variability in the Balkans, Italy, and the southern Carpathians, but opposing temperature variability patterns are manifested over the British Isles and southern Scandinavia. The strong and consistent anti-phase relationship between our reconstruction and a reconstruction of the summer North Atlantic Oscillation (sNAO) suggests that the sNAO pattern is a main driver of the teleconnection between summer temperatures in southeastern versus northwestern Europe. This teleconnection is most pronounced on interannual timescales and has been stable over the last two centuries.