Cryptotephra from the Icelandic Veieiv?tn 1477?CE eruption in a Greenland ice core: confirming the dating of volcanic events in the 1450s?CE and assessing the eruption's climatic impact

摘要

Volcanic eruptions are a key source of climatic variability, and reconstructing their past impact can improve our understanding of the operation of the climate system and increase the accuracy of future climate projections. Two annually resolved and independently dated palaeoarchives – tree rings and polar ice cores – can be used in tandem to assess the timing, strength and climatic impact of volcanic eruptions over the past ～ ?2500?years. The quantification of post-volcanic climate responses, however, has at times been hampered by differences between simulated and observed temperature responses that raised questions regarding the robustness of the chronologies of both archives. While many chronological mismatches have been resolved, the precise timing and climatic impact of two major sulfate-emitting volcanic eruptions during the 1450s?CE, including the largest atmospheric sulfate-loading event in the last 700?years, have not been constrained. Here we explore this issue through a combination of tephrochronological evidence and high-resolution ice-core chemistry measurements from a Greenland ice core, the TUNU2013 record. We identify tephra from the historically dated 1477?CE eruption of the Icelandic Veieiv?tn–Bárearbunga volcanic system in direct association with a notable sulfate peak in TUNU2013 attributed to this event, confirming that this peak can be used as a reliable and precise time marker. Using seasonal cycles in several chemical elements and 1477?CE as a fixed chronological point shows that ages of 1453?CE and 1458?CE can be attributed, with high precision, to the start of two other notable sulfate peaks. This confirms the accuracy of a recent Greenland ice-core chronology over the middle to late 15th century and corroborates the findings of recent volcanic reconstructions from Greenland and Antarctica. Overall, this implies that large-scale Northern Hemisphere climatic cooling affecting tree-ring growth in 1453?CE was caused by a Northern Hemisphere volcanic eruption in 1452 or early 1453?CE, and then a Southern Hemisphere eruption, previously assumed to have triggered the cooling, occurred later in 1457 or 1458?CE. The direct attribution of the 1477?CE sulfate peak to the eruption of Veieiv?tn, one of the most explosive from Iceland in the last 1200?years, also provides the opportunity to assess the eruption's climatic impact. A tree-ring-based reconstruction of Northern Hemisphere summer temperatures shows a cooling in the aftermath of the eruption of ? 0.35? ° C relative to a 1961–1990?CE reference period and ? 0.1? ° C relative to the 30-year period around the event, as well as a relatively weak and spatially incoherent climatic response in comparison to the less explosive but longer-lasting Icelandic Eldgjá 939?CE and Laki 1783?CE eruptions. In addition, the Veieiv?tn 1477?CE eruption occurred around the inception of the Little Ice Age and could be used as a chronostratigraphic marker to constrain the phasing and spatial variability of climate changes over this transition if it can be traced in more regional palaeoclimatic archives.