Received: 21 Feb 2019 – Discussion started: 30 Apr 2019
Abstract. Arctic sea ice decrease in extent in recent decades has been linked to sea surface temperature (SST) anomalies in the North Pacific Ocean. In this study, we assess the relative contributions of the two leading modes in North Pacific SST anomalies representing external forcing related to global warming and internal forcing related to Pacific Decadal Oscillation (PDO) to the Arctic sea ice loss in boreal summer and autumn. For the 1979–2017 period, the time series of the global warming and PDO modes show significant positive and negative trends, respectively. The global warming mode accounts for 44.9 % and 50.1 % of the Arctic sea ice loss in boreal summer and autumn during this period, compared to the 20.0 % and 22.2 % from the PDO mode. There is also a seasonal difference in the response of atmospheric circulations to the two modes. The PDO mode excites a wavetrain from North Pacific to the Arctic; the wavetrain is not seen in the response of atmospheric circulation to the global warming mode. Both dynamic and thermodynamic forcings work in the relationship of atmospheric circulation and sea ice anomalies.
How to cite. Yu, L., Zhong, S., and Vihma, T.: The contributions of the leading modes of the North Pacific sea surface temperature variability to the Arctic sea ice depletion in recent decades, The Cryosphere Discuss. [preprint], https://doi.org/10.5194/tc-2019-38, 2019.
Arctic sea ice cover has been decreasing in recent decades. The reason for the decrease remains unclear. In this study, we examine the contributions of the North Pacific SST anomalies to the decrease. There are global warming and Pacific Decadal Oscillation (PDO) modesof the North Pacific SST variability in boreal summer and autumn. The global warming mode explains 44.9% and 50.1% of the Arctic sea ice loss in boreal summer and autumn, respectively. There are 22.0% and 22.2% for PDO mode.
Arctic sea ice cover has been decreasing in recent decades. The reason for the decrease remains...