Frost rings as time markers in Northern Hemisphere tree-ring chronologies, with special reference to the 1627 BC and AD 536 events

This paper discusses the findings of frost rings in three supra-long Northern Hemisphere tree-ring chronologies. Comparison between recently published data representing bristlecone pine from western North America, Scots pine from northern Fennoscandia and Siberian larch and Siberian spruce from the Yamal Peninsula shows the rare occurrence of frost rings dated to exactly same calendar years in more than one of these chronologies. The frost ring dates evident in all three datasets are dated to 1627 BC and AD 536. Previously, tree-ring features indicative of adverse growing conditions around 1627 BC have been discussed in the literature. Here, it is emphasised that the frost rings 1627 BC and AD 536 are dated to exactly same calendar year in all available tree-ring records, which demonstrates the value of such an event as a definitive time marker. Other major events of frost rings from multiple sites were dated to 421 BC, 251 BC, AD 627, AD 884, AD 985, AD 1109, AD 1259, AD 1453, AD 1601 and AD 1884. Similar to 1627 BC and AD 536, some of these events have been attributed to volcanic forcing and climate anomalies that led to human consequences and disasters. The case of the 1650 s BC appears different, with possibility of more than one major eruptions, as suggested by frost ring events dated to 1656 BC and 1653 BC in Yamal and western USA, respectively.