Eastern USA summer temperatures since 1461 CE show connections to volcanic forcing and jet stream dynamics

Abstract

Contextualizing current increases in Northern Hemisphere temperatures is precluded by the short instrumental record of the past ca. 120 years and the dearth of temperature-sensitive proxy records, particularly at lower latitudes south of <50 °N. We develop a network of 29 blue intensity chronologies derived from tree rings of Tsuga canadensis (L.) Carrière and Picea rubens Sarg. trees distributed across the Mid-Atlantic and Northeast USA (MANE)---a region underrepresented by multi-centennial temperature records. We use this network to reconstruct March-September air temperatures back to 1461 CE based on a model that explains 62% of the instrumental temperature variance from 1901-1976 CE. Since 1998 CE, MANE summer temperatures are consistently the warmest within the context of the past 561 years exceeding the 1951-1980 mean +1.3 °C. Temperature variability across MANE is linked with the position and intensity of the Northern Hemisphere polar jet stream (NHJ), which triggers regional warm and cool extremes, respectively. The new network reveals a strong regional temperature response to large volcanic eruptions, with the most severe temperature departure of -1.05 °C following the eruption of Mount Tambora in 1815 CE. Expanding the MANE network to the west and south and combining it with existing temperature-sensitive proxies across North America is an important next step toward producing a gridded temperature reconstruction field for North America.