Linear Response Function Reveals the Most Effective Remote Forcing in Causing September Arctic Sea Ice Melting in CESM. Issue 15 (6th August 2021)

• Record Type: Journal Article
• Authors: Wu, Yutian; Lu, Jian; Ding, Qinghua; Liu, Fukai
• Is Part Of: Geophysical research letters. Volume 48:Issue 15(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-06
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL094189
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: We apply the linear response function to investigate the most excitable mode of the September Arctic sea ice in the Community Earth System Model. We find that this sea ice mode preferentially takes place over the Pacific side of the Arctic and its remote forcing corresponds to a dipole pattern of precipitation anomaly in the tropics with an increase of precipitation over the western and central tropical Pacific ocean while a decrease over the Maritime Continent. The tropical precipitation anomaly likely drives a Rossby wave train propagating toward the higher latitudes and leads to a ridge anomaly over the Pacific side of the Arctic, resulting in poleward atmospheric heat transport, enhanced downward longwave radiation and thus melting of the sea ice. In addition, a good agreement is found with the leading tropical‐Arctic teleconnection mode in a pre‐industrial simulation, supporting the usefulness and robustness of the linear response function method. Plain Language Summary: The minimum state of Arctic sea ice in September has experienced a drastic decline in the past two decades and is projected to continue to decline in the future warming climate. It is of both scientific and societal importance to understand both the year‐to‐year variability and anthropogenic change of the Arctic sea ice and their underlying physical mechanisms. This study, via a novel dynamical approach rather than a statistical one, reveals the optimal forcing pattern that excites the largest sea ice response in September. Our results will contribute to an improved understanding of both the natural variability and anthropogenic change of the September Arctic sea ice in climate model simulations. Key Points: Linear response function reveals the most excitable mode of September Arctic sea ice, which is maximized over the Pacific side of the Arctic Precipitation anomaly over the western and central tropical Pacific ocean and its resulting teleconnection is likely the cause Good agreement is found with statistical leading mode of a pre‐industrial run, indicating the robustness of linear response function results