Ólafur Eggertsson

Timber Logging in Central Siberia is the Main Source for Recent Arctic Driftwood

Abstract Recent findings indicated spruce from North America and larch from eastern Siberia to be the dominating tree species of Arctic driftwood throughout the Holocene. However, changes in source region forest and river characteristics, as well as ocean current dynamics and sea ice extent likely influence its spatiotemporal composition. Here, we present 2556 driftwood samples from Greenland, Iceland, Svalbard, and the Faroe Islands. A total of 498 out of 969 Pinus sylvestris ring width series were cross-dated at the catchment level against a network of Eurasian boreal reference chronologies. The central Siberian Yenisei and Angara Rivers account for 91% of all dated pines, with their outermost rings dating between 1804 and 1999. Intensified logging and timber rafting along the Yenisei and Angara in the mid-20th century, together with high discharge rates, explain the vast quantity of material from this region and its temporal peak ca. 1960. Based on the combined application of wood-anatomical and dendrochronological techniques on a well-replicated data set, our results question the assumption that Arctic driftwood mainly consists of millennial-old larch and spruce. Nevertheless, data from other species and regions, together with longer boreal reference chronologies, are needed for generating reliable proxy archives at the interface of marine and terrestrial environments.

Multi-proxy dating of Iceland’s major pre-settlement Katla eruption to 822–823 CE

U. Buntgen received funding from the Ministry of Education, Youth and Sports of CR within the National Sustainability Program I (NPU I; GN LO1415), and additional support was provided by NSF grant 0909541. We are particularly thankful to the NEEM project and its participants.

A multi-scale resolution of snow-avalanche activity based on geomorphological investigations at Fnjóskadalur, northern Iceland

The article describes investigations that highlight snow-avalanche events that have not been reported in historical records. While historical sources are most often the basis for all natural hazard and risk research, alternative methods based on geomorphic investigations are often neglected. Here, we emphasise the use of geomorphic evidence to improve our knowledge of the maximum runout distance reached by snow avalanches as well as the frequency of the events. Investigations were carried out in remote, avalanche-prone areas, where the geomorphic evidence has not been disturbed or removed. Dendrogeomorphic investigations supply annual resolved records of avalanche winters up to the age of the investigated tree stand: over 120 years in northern Iceland. The study of snow-avalanche transported debris may be used to map the extent of the potential snow-avalanche deposition zone, and offer relative dating on a secular scale; stratigraphic profiles do provide results on long timescales, but only provide relative dating. The article discusses the relevance of each method, and concludes that the combination of the three methods can improve the common risk-mitigation approach based on historical records.