HKUST Researchers Reveal How Tropical Pacific Climate Shifts Amplify Arctic Sea‑Ice Melt

Led by scholars from The Hong Kong University of Science and Technology (HKUST), a research team has discovered that, since the early 2000s, both sea surface temperature changes near the equator and the associated atmospheric adjustments over the Pacific have accelerated markedly—becoming a key driver of the increasingly rapid loss of Arctic sea ice during autumn. The findings highlight that, under ongoing global warming, climate linkages between distant regions are far more dynamic and complex than previously understood.

The study was led by Prof. SU Hui, Chair Professor in the Department of Civil and Environmental Engineering and Global STEM Professor at HKUST. The research team comprised Research Assistant Professor Prof. WANG Cen and Prof. LI Yana, along with PhD students WANG Yanjia and ZHU Kuilin, all from the Department of Civil and Environmental Engineering at HKUST, and was supported by collaborators from the University of Science and Technology of China and Shaanxi University of Technology. Drawing on 45 years of climate data from 1979 to 2023, the team published their findings in Science Advances  under the title “Post‑2000 faster ENSO phase transitions amplify autumn sea ice loss in the Laptev–East Siberian Sea.”

The research focuses on the El Niño–Southern Oscillation (ENSO), a climate phenomenon driven by coupled ocean–atmosphere interactions in the equatorial Pacific. El Niño is characterized by abnormal warming in the central–eastern equatorial Pacific, whereas La Niña features anomalous cooling in the same region. The “Southern Oscillation” refers to changes in atmospheric pressure between the Pacific and the Indonesia–Australia region, forming the atmospheric counterpart of ENSO. Together, these coupled variations shape one of the most influential modes of global climate variability.

The team found that when El Niño intensity in the preceding winter undergoes more rapid transitions, the following year's autumn sea ice melt in the Arctic accelerates correspondingly, with the most pronounced impacts occurring in the Laptev and East Siberian Seas (LESS), key sections of the Northern Sea Route. Prof. Wang Cen, first author of the study explained “Since the 2000s, the warm sea surface anomalies associated with El Niño no longer fade gradually but instead shift rapidly to cold anomalies. It is like switching a pot of hot water with cold water in an instant. This abrupt change exerts a stronger shock on the atmosphere, significantly strengthening the Western North Pacific anticyclone (WNPAC). The enhanced WNPAC then channels heat and moisture from the tropics toward the Arctic along a northeastward‑propagating Rossby wave train, leading to warmer and more humid autumn conditions in the Arctic and causing sea ice to melt more quickly and extensively.”

Prof. Su Hui, the study’s corresponding author noted, “This research deepens our understanding of long‑distance climate teleconnections between the tropics and the polar regions, and further demonstrates the pivotal influence of ENSO evolution on Arctic sea ice melt. Incorporating ENSO phase‑transition characteristics into Arctic sea ice prediction models could improve seasonal and interannual forecasting accuracy. This will enable governments and relevant sectors to better anticipate the risks associated with extreme climate events and to formulate more effective adaptation strategies, benefiting industries such as shipping, agriculture, and many others sensitive to climate variability.”