Department Seminar: Anthony Chan

Title: Evolution of Extreme Sea Ice Loss Events Under Anthropogenic Climate Forcings in CMIP6 Models

Abstract: Antarctic sea ice experienced an abrupt decline in 2016, transitioning from a record maximum to a then-record minimum. The drivers of this event remain uncertain, raising questions about whether it marks the onset of a long-term melting trend or an isolated episode of internal climate variability. Using pre-industrial control runs from CMIP6, we identify past extreme events comparable to the 2016 decline and examine their primary atmospheric and oceanic drivers. Our results indicate that while such events can occur without anthropogenic forcing, they are rare. The most consistent association is a negative SAM transition preceding extreme sea ice loss. Additional influences, such as tropical Pacific variability (e.g., Niño 3.4), may also play a role, though these factors alone do not explain all events.

A key finding is that most models simulate a recovery of sea ice following extreme loss events, contrasting with the persistent declines seen in recent observations. This suggests that while internal climate variability can produce large swings in sea ice, anthropogenic forcing may be contributing to ongoing losses in 2023 -2024 .

Building on this approach, we will extend the analysis to historical and future SSP scenarios to assess how extreme Antarctic sea ice loss events evolve under different climate forcings. By comparing past and projected events, we aim to determine whether these extremes are becoming more frequent or severe due to external forcing, improving our understanding of their predictability.