Changes in late-Neoglacial climate inferred from former equilibrium-line altitudes in the Queen Elizabeth Islands, Arctic Canada

摘要

Regional-scale spatial variation in the change in equilibrium-line altitude (ELA) trend surface in the Queen Elizabeth Islands (QEI), Arctic Canada between the 'Little Ice Age' (LIA) and 1960 corresponds to Empirical Orthogonal Functions (EOFs) representing specific patterns of summer climate variability found in the modem record. Extreme warm (1953-1962) and cold (1965-1974) decades in the modern record were used as modern analogues of climatic conditions during the early twentieth century and the LIA, respectively. Because of the minimal influence of precipitation during both extreme decades, temperature is the variable upon which the fluctuation of the ELA is dependent. Hence, the ELA Ah pattern describes the spatial pattern of change in SAT across the QEI between the LIA and 1960. This pattern is consistent with the primary mode of variability of mean summer surface air temperature (SAT) in the modern record (ie, EOF-1, 1949-2002), the positive (negative) phase of which is strongly in place during the extreme warm (cold) decade. SAT anomalies in the QEI during the warm (cold) decade are positively correlated with a weak (strong) QEI-distal (QEI-proximal) polar vortex, higher (lower) than normal SSTs in the North Atlantic, and one of the lowest (highest) periods of sea-ice extent during the twentieth century. The climatic conditions during the cold decade are believed to describe conditions, which if sustained, would lead to a LIA-type cold episode capable of long-term snowline lowering and perennial snow/ice expansion. The climatic conditions during the warm decade represent possible modern analogues for those that might have occurred during the early twentieth century in the Canadian High Arctic, which led to a substantial reduction in perennial snow/ice.