Thermal conditions on the coast of Labrador during the late 19th/early 20th century

Abstract. The long-term Moravian missionary meteorological observations, conducted from the late 18th century until the 2nd World War, provide a unique perspective on climate conditions along the Labrador coast. The present paper focuses on the analysis of air temperature in the late 19th and early 20th centuries based on sub-daily observations (three to five times a day) available for six stations: Rama (1882–1890), Hebron (1882–1918), Okak (1883–1889), Nain (1882–1913, 1926–1939), Zoar (1882–1894), and Hopedale (Hoffenthal) (1882–1898). The meteorological observations were carried out by the missionaries on behalf of the Deutsche Seewarte and are preserved in the archives of Deutscher Wetterdienst (Germany). Quality-controlled and corrected mean daily air temperature were used to calculate standard climatic characteristics, including monthly, seasonal, and annual means; climate continentality indices; day-to-day temperature variability; thermal seasons; and other characteristics. In addition to extending the climate analysis, a set of additional useful climatic indices was calculated, including Growing Degree Days (GDD), Air Thawing Index (ATI), Positive Degree Days (PDD), and Air Freezing Index (AFI). Historical temperature data from the coast of Labrador were compared with contemporary thermal conditions from 1990 to 2020. At Nain, the mean annual air temperature during 1882–1892 was 2.3 °C lower than during 1990–2020. The separate Nain record for the Early Twentieth Century Warming (1926–1939) remained 0.8 °C lower than the modern mean. At Hopedale, the mean annual temperature was −3.2 °C during 1882–1898 and −1.5 °C during 1990–2020, giving a historical–modern difference of −1.7 °C. At Nain, warmer temperature classes occurred more frequently during the modern period, particularly in autumn and summer, whereas the differences at Hopedale were most apparent in summer. The historical records also indicate a slightly greater annual temperature range and stronger climate continentality than in the modern period, with the largest temperature changes occurring during the cold season.