The role of eastern Siberian snow and soil moisture anomalies in quasi-biennial persistence of the Arctic and North Atlantic Oscillations

R J Allen,C S Zender

doi:10.1029/2010jd015311

Abstract

Variations in the Arctic Oscillation (AO) and its regional manifestation, the North Atlantic Oscillation (NAO), generate much of the nonseasonal variability in the winter climate over the Northern Hemisphere midlatitudes. Despite being an internal mode of the atmosphere, the Arctic and North Atlantic Oscillations (N/AO) exhibit a slightly red spectrum, varying on quasi-biennial (2-3 years) and quasi-decadal time scales. Such low-frequency variability is likely due to the coupling of the atmosphere to boundary conditions and/or external forcings. Here we show that Eurasian snow cover, particularly over eastern Siberia (ESB), exhibits quasi-biennial persistence similar to the N/AO. Furthermore, the snow-AO mechanism operates on quasi-biennial timescales, with fall ESB snow cover significantly related to vertically propagating Rossby wave activity and the N/AO for the next two to three winters. On the basis of land surface model simulations from the Global Land Data Assimilation System (GLDAS), the interseasonal carryover of ESB snow is related to soil moisture anomalies and an evaporation-convection feedback. These findings suggest quasi-biennial persistence of the N/AO is partly due to land surface forcing in the form of both ESB snow and soil moisture anomalies.

Highlights

[3] both appear to be fundamental, internal modes of the atmosphere with a timescale on the order of a week [e.g., Feldstein, 2000], proxy records [Cook and D’Arrigo, 2002; Jones et al, 2001] and instrumental data [Schneider and Schonwiese, 1989; Saito and Cohen, 2003] show the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) (N/AO) exhibit significant low‐frequency variability, with periods of prolonged positive or negative NAO and AO (N/AO) index values
[4] There is increasing evidence that the low‐frequency N/AO variability comes from coupling with other components of the climate system, such as tropical [Hoerling et al, 2001; Hurrell et al, 2004] and extratropical [Rodwell et al, 1999; Robertson et al, 2000] sea surface temperatures (SSTs), as well as external forcings, such as greenhouse gases (GHGs) [Shindell et al, 1999; Fyfe et al, 1999; Gillett et al, 2003; Osborn, 2004; Miller et al, 2006]
[5] In this paper, we show that quasi‐biennial (2–3 year) N/AO persistence is related to October snow cover anomalies in eastern Siberia (ESB)

Summary

Introduction

[3] both appear to be fundamental, internal modes of the atmosphere with a timescale on the order of a week [e.g., Feldstein, 2000], proxy records [Cook and D’Arrigo, 2002; Jones et al, 2001] and instrumental data [Schneider and Schonwiese, 1989; Saito and Cohen, 2003] show the NAO and AO (N/AO) exhibit significant low‐frequency variability, with periods of prolonged positive or negative N/AO index values. [5] In this paper, we show that quasi‐biennial (2–3 year) N/AO persistence is related to October snow cover anomalies in eastern Siberia (ESB).

Results

Conclusion