How shifts in ice in the Arctic can impact East Asian summers

In past years, East Asian summers have been dominantly affected by El Niño and tropical oceans. Recent research suggests this pattern has shifted: in the decades since the late 1990s, the type of ice present in the Arctic appears to play a growing role in shaping the East Asian summer climate.

Much of the regional or global climate is influenced by the temperature of the ocean, surface temperatures, jet streams and or ice presence. The Arctic region has begun to experience a shift from primarily multi-year ice to newly formed ice (NFI), which is an important shift because NFI is more volatile in its heat flux compared to more established bodies of ice. Before the late 1990s, the East Asian summer climate appeared to be more influenced by tropical oceans and oceanic climate phenomena such as El Niño-Southern Oscillation (ENSO), though this relationship appears to have noticeably weakened since the late 1990s. Researchers from Zhejiang University aimed to determine what relationship, if any, the NFI in the Arctic has on the East Asian jet stream and heatwaves in China during the summertime, and how exactly the relationship is possible.

Dr. Lifei Lin and researchers published their results in Ocean-Land-Atmosphere Research in July 2026.

The physical pathway identified in Lin’s research is dubbed the “stratospheric bridge”. This finding relates the Atlantic sector of the Arctic and its NFI in the winter to trigger an early and abrupt breakdown of the stratospheric polar vortex in the spring, effectively acting as a “switch” for the seasons. Winter NFI over the Atlantic sector of the Arctic enhances the upward circulation of planetary waves into the stratosphere, which triggers an earlier stratospheric final warming (the reversal of zonal circulation from westerly to easterly). This results in an anomalous anticyclone over the polar stratosphere through late spring and summer, producing a negative Arctic Oscillation similar to the pattern that shifts the East Asian jet stream southward. Overall, this effect reduces heatwaves over subtropical China.  This cross-seasonal connection between the Arctic and East Asia was not seen prior to the 1990s, which allowed researchers to pose the question of whether the two regions could have a possible climatic link.

“As the influence of preceding ENSO fades, the footprint of the rapidly changing Arctic appears to be becoming an increasingly important driver of East Asian summer climate,” says author of the study, Dr. Lifei Lin of Zhejiang University.

The tropical influence of ENSO is weakening and the ice in the Arctic is shifting towards less stable newer ice formations. A change like this will have its impacts, though those impacts are not necessarily indicative of causality. Additionally, while a temporary reduction in heatwaves is a positive, it’s not likely to be long-lived. With NFI becoming the dominant ice form in the Arctic, the volatility and instability of these ice forms may dissipate in the future, leading to exacerbated heat waves once the ice presence is further reduced.

While this work illuminates the overall impact NFI has on climate, as well as underlining the importance of ice presence (whether newly formed or multi-year) for its cooling properties on global and regional climates, researchers state it should be taken as diagnostic information, not necessarily a causal relationship.

More immediate work to be done includes determining causality by including numerical experiments and evaluation with models to attempt to reproduce the cross-seasonal teleconnection suggested within the study. For long term goals, establishing the true relationship between NFI and the subtropical East Asian heatwaves to improve early warning signs and subsequent preparations for affected populations is necessary, especially as NFI cover fades in a warming climate and heatwaves become more frequent.

Lifei Lin, Chundi Hu and Zeming Wu of the State Key Laboratory of Ocean Sensing & Ocean College at Zhejiang University, with Chundi Hu, Lei Zhou and Dake Chen of the Key Laboratory of Polar Ecosystem and Climate Change at Shanghai Jiao Tong University, with Ke Fan, Dake Chen and Chundi Hu of the Southern Marine Science and Engineering Guangdong Laboratory at Sun Yat-sen University, Quanliang Chen of the School of Atmospheric Sciences at Chengdu University of Information Technology and Dake Chen of the State Key Laboratory of Satellite Ocean Environment Dynamics at Second Institute of Oceanography contributed to this research.

Grants from the National Key Research and Development Program of China, Southern Marine Science and Engineering Guangdong Laboratory, Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory, Shanghai Frontiers Science Center of Polar Science, Zhejiang University, the Ocean College Seed Fund, Excellent Young Teachers Training Project, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Open Foundation of State Key Laboratory of Satellite Ocean Environment Dynamics, and Second Institute of Oceanography helped fund this research.