Holocene precipitation seasonality in northern Svalbard: Influence of sea ice and regional ocean surface conditions

Sofia E Kjellman,Anders Schomacker,Elizabeth K Thomas,Lena Håkansson,Sandrine Duboscq,Allison A Cluett,Wesley R Farnsworth,Lis Allaart,Owen C Cowling,Nicholas P Mckay,Skafti Brynjólfsson,Ólafur Ingólfsson

doi:10.1016/j.quascirev.2020.106388

Abstract

Arctic precipitation is predicted to increase in the coming century, due to a combination of enhanced northward atmospheric moisture transport and local surface evaporation from ice-free seas. However, large model uncertainties, limited long-term observations, and high spatiotemporal variability limit our understanding of these mechanisms, emphasizing the need for paleoclimate records of precipitation changes. Here we use lipid biomarkers in lake sediments to reconstruct precipitation seasonality in northern Spitsbergen, Svalbard. We measured the hydrogen isotopic ratios (δ2H) of n-alkanoic acids (C20–C30) from sedimentary leaf waxes in lake Austre Nevlingen, Spitsbergen. We interpret δ2H values of mid-chain (C22) and long-chain (C28) n-alkanoic acids to represent δ2H of lake and soil water, respectively. Austre Nevlingen lake water δ2H reflects amount-weighted mean annual precipitation δ2H. In contrast, soil water is mostly recharged by summer rainfall, and therefore reflects δ2H values of summer precipitation. Austre Nevlingen leaf wax δ2H values are 2H-depleted in the Early Holocene, suggesting high winter precipitation amounts. This coincides with high summer insolation, strong Atlantic water advection and reduced spring sea-ice cover in surrounding waters. Winter precipitation continued to dominate until c. 6 cal. kyr BP. After 6 cal. kyr BP, the trend in the biomarker record is not as clear. This could be related to colder conditions causing longer duration of seasonal lake-ice cover, thereby influencing the precipitation seasonality registered by the lake water. The Austre Nevlingen record suggests a close relationship between precipitation seasonality and regional ocean surface conditions, consistent with simulations suggesting that Arctic winter sea-ice loss will lead to increased local evaporation.

Highlights

By the end of the 21st century, warming in the Arctic is predicted to exceed the global average by a factor of 2.2e2.4 (Collins et al, 2013)
Radiocarbon ages, calibrated median ages and 2s age intervals for ANS1 and ANP3 are presented in Table 1 and Figs 4 and 5
The uppermost age in ANP3 (LuS 12222) appeared to be an outlier compared to the rest of the age-depth model, which was otherwise fairly linear, despite different terrestrial and aquatic sources of the samples

Summary

Introduction

By the end of the 21st century, warming in the Arctic is predicted to exceed the global average by a factor of 2.2e2.4 (Collins et al, 2013) This amplified warming will affect the amount and seasonality of precipitation, through hydrological intensification (Rawlins et al, 2010; Collins et al, 2013; Bintanja and Selten, 2014). Other studies have described Early Holocene re-advances for glaciers on Svalbard (Lønne, 2005; Henriksen et al, 2014; van der Bilt et al, 2015; Farnsworth et al, 2017, 2018; Larsen et al, 2018). Kyr BP, inferred from increased glacier activity (Svendsen and Mangerud, 1997; Røthe et al, 2015, 2018; Miller et al, 2017; Bartels et al, 2018; Lovell et al, 2018). A later cooling step, associated with the Little Ice Age, started around 0.7 cal. kyr BP (Werner, 1993; van der Bilt et al, 2015; Miller et al, 2017)

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Discussion

Conclusion