GFDL - Geophysical Fluid Dynamics Laboratory

Mechanisms for Low Frequency Variability of Summer Arctic Sea Ice Extent

April 7th, 2015

Rong Zhang. PNAS, 2015. DOI: 10.1073/pnas.1422296112

Summary

Satellite observations reveal a substantial decline in September Arctic sea ice extent (SIE) since 1979. The exact mechanisms causing this rapid decline are still unclear. The goals of this research are to provide a fundamental understanding of low frequency variability of summer Arctic sea ice extent, and the implications for the observed decline in summer Arctic sea ice in recent decades. A multiple regression model was developed to quantify the relative contributions of three key predictors on the low frequency variability of summer Arctic sea ice extent: Atlantic heat transport into the Arctic, Pacific heat transport into the Arctic, and Arctic Dipole. A 3,600 year segment of the GFDL’s CM2.1 global climate model control simulation was employed to develop this multiple regression model.

In both modeling results and observations, the September Arctic SIE variations are significantly correlated with March Barents Sea SIE variations, indicating the important role of the Atlantic heat transport into the Arctic. If the AMOC and the associated Atlantic heat transport into the Arctic were to weaken in the near future due to internal variability, there might be a hiatus in the decline of September Arctic sea ice, and a delay in attaining a summer ice-free Arctic. The rapid change in summer Arctic sea ice could have significant large scale climatic, ecological, and economic impacts. Understanding the mechanisms for the recent rapid decline in summer Arctic sea ice will help to predict future changes in summer Arctic sea ice and associated climatic, ecological, and economic impacts.

Mechanisms for low-frequency variability of summer Arctic SIE. (A) Schematic of Atlantic/Pacific inflow (red/orange arrows) and Arctic ocean circulation. White color reflects observed climatological September SIE over 1979–2013. (B) Schematic of key mechanisms. (C) Simulated LF annual mean AMOC index and HTATL anomalies, normalized by their SDs [σ(AMOC) = 0.8 Sverdrup]. BS, Bering Strait.
Mechanisms for low-frequency variability of summer Arctic SIE. (A) Schematic of Atlantic/Pacific inflow (red/orange arrows) and Arctic ocean circulation. White color reflects observed climatological September SIE over 1979–2013. (B) Schematic of key mechanisms. (C) Simulated LF annual mean AMOC index and HTATL anomalies, normalized by their SDs [σ(AMOC) = 0.8 Sverdrup]. BS, Bering Strait.