Climatological conditions of enhanced Arctic storm activity in relation to permafrost degradation in eastern Siberia

Abstract:

The last decade (2000–2010) was the warmest on record at high northern latitudes. Surface air temperature anomalies and associated sea level pressure fields in Arctic exhibited different spatial patterns at the beginning of the 21st century than they did throughout the majority of the 20th century.

In eastern Siberia, the abrupt soil warming within upper permafrost layer and deepening active layer thickness has observed in response to increasing in soil moisture under wet hydro-climatic conditions during the warming period of 2000s. According to climatological analyses, the large positive anomalies of both rainfall and snow accumulation in eastern Siberia are caused by strengthened cyclonic pattern in these years which induce more water vapor advection. These anomalies are more enhanced than those before 1990s and continuously appear after 2004.

Long-term simulation of permafrost temperature and active layer thickness using a sophisticated land surface model (CHANGE) was carried out. The correlations between precipitation in late summer and soil temperature showed that the most regions exhibited either negative or not significant correlations between precipitation and soil temperature during the past period (1961–1980), whereas positive correlations were observed during the recent period (1991–2009). A region of significantly positive correlation was observed along the Siberian coast and in eastern Siberia and could have corresponded with areas of increased storm activity. The soil warming is thus due to not only increasing in snow accumulation which is well-known relationship by previous studies but also increasing in rainfall in late summer which furthermore accelerates the warming due to changes in hydro-thermal properties within the active layer.

The precipitation increase in the last decade led to deepening active layer accompanying with remarkable increase in soil moisture. The perennially waterlogged conditions had exacerbated the boreal forest habitat; that is, larch trees had widely withered and died in eastern Siberia detected by field observation and satellite remote sensing analyses. The change in hydro-thermal regime could have important consequences on permafrost degradation with ecosystem and landscape changes in eastern Siberia.