Late Holocene Russian Arctic climate variability – spatial and seasonal aspects inferred from glacier and ground ice

Abstract:

The Arctic currently experiences an unprecedented warming. This dynamic response to changes in climate forcing as well as corresponding feedbacks as sea ice retreat make the Arctic a key region to study past and future climate changes. Recent Arctic-wide temperature reconstructions indicate a long-term cooling prior to the ongoing warming. However, they are based mostly on proxies that record summer information and hence are assumed to be seasonally biased towards the summer. Moreover, the Russian Arctic is significantly underrepresented in these Arctic-wide reconstructions.

Here we present glacier and ground ice records from Northern Siberia that provide valuable information for a better spatial and seasonal understanding of Holocene climate variability in the Arctic.

The high-resolution Akademii Nauk δ¹⁸O ice core record (Severnaya Zemlya) proves the Late Holocene cooling and the pronounced warming after 1800. It shows neither a prominent Medieval Climate Anomaly nor a Little Ice Age but gives evidence of several abrupt warming and cooling events during the last centuries, also found in ice-core records from Svalbard and Franz Josef Land. They may be related to the regional internal climate variability, i.e. atmosphere-sea ice feedbacks in the Barents and Kara seas region.

Ice wedges were studied at several study sites in the Lena River Delta and the coastal permafrost lowlands of the Laptev Sea region. They are formed by the repeated filling of wintertime thermal contraction cracks by snow melt water in spring. Radiocarbon dating of organic matter enables the generation of centennial scale δ¹⁸O records that are indicative of temperatures in the cold period of the year (winter and spring).

Our ice wedge records show general increasing δ¹⁸O trends over the Mid and Late Holocene and an unprecedented recent warming. Both may be related to the changes in orbital forcing during the cold season as well as in greenhouse gas concentrations over the last millennia. However, this pattern is in contradiction to most other Arctic temperature records that, in turn, are likely summer-biased. Our ice-wedge records add therefore unique and substantial climate information for understanding the seasonal patterns of Holocene climate in the Arctic and might help to bridging the gap between proxy records and climate models in the Arctic.