24th Pacific Science Congress (PSC-24)

Sea ice covers approximately 15% of the global oceans but is undergoing unprecedented transformation with profound implications for the Earth’s climate system. Nearly five decades of temporally and spatially consistent satellite observations reveal starkly different trajectories between the polar regions. September Arctic sea ice has declined by approximately 13% per decade since 1979, with projections indicating that ice-free summers may occur even before 2050. The Arctic has warmed four times faster than the global average, driven by powerful feedbacks. Conversely, Antarctic sea ice exhibited modest growth until 2016, followed by consecutive record lows, suggesting a fundamental regime shift.  

These changes trigger cascading effects across multiple systems. Climate feedbacks, particularly albedo changes, have reduced global sea ice radiative effect by 15% in the historical record. Sea-ice loss disrupts ocean circulation through altered water mass formation, threatening the stability of the global overturning circulation. Marine ecosystems face severe disruption, from shifting primary production to habitat loss for ice-dependent species like polar bears and emperor penguins. Human activities are also transforming, with Arctic shipping routes becoming increasingly navigable while facing new hazards from drifting multiyear ice.

However, critical knowledge gaps persist despite technological and scientific advances. Antarctic observations remain sparse, particularly for year-round measurements and under-ice properties. Satellite continuity faces new threats from ageing sensors and lack of funding support. Climate models also struggle to represent key processes, including snow-ice interactions, ice type diversity, and ocean-atmosphere coupling. Addressing these challenges requires sustained international cooperation and enhanced observational networks. Emerging technologies, including autonomous platforms and machine learning approaches, offer promising solutions but require careful validation. This presentation will review the dramatic transformations underway across the polar regions and highlight how advances in prediction and adaptation rely on interdisciplinary approaches that bridge physical sciences, ecosystems, and human dimensions.

Arctic sea ice,Antarctic sea ice,Global Change