Decadal oscillation provides skillful multiyear predictions of Antarctic sea ice

Abstract

Over the satellite era, Antarctic sea ice exhibited an overall long-term increasing trend, contrary to the Arctic reduction under global warming. However, the drastic decline of Antarctic sea ice in 2014–2018 raises questions about its interannual and decadal-scale variabilities, which are poorly understood and predicted. Here, we identify an Antarctic sea ice decadal oscillation, exhibiting a quasi-period of 8–16 years, that is anticorrelated with the Pacific Quasi-Decadal Oscillation (r = −0.90). By combining observations, Coupled Model Intercomparison Project historical simulations, and pacemaker climate model experiments, we find evidence that the synchrony between the sea ice decadal oscillation and Pacific Quasi-Decadal Oscillation is linked to atmospheric poleward-propagating Rossby wave trains excited by heating in the central tropical Pacific. These waves weaken the Amundsen Sea Low, melting sea ice due to enhanced shortwave radiation and warm advection. A Pacific Quasi-Decadal Oscillation-based regression model shows that this tropical-polar teleconnection carries multi-year predictability.

Ross–Weddell Dipole Critical for Antarctic Sea Ice Predictability in MPI–ESM–HR

“…Our study adds to the host of recent scientific evidence [16][17][18]25,26,59] that especially highlight Antarctic sea ice and the Antarctic dipole as critical aspects of near-term climate variability and predictability, especially in the austral summer season [26,60]. The stark contrast between the large and extensive assimilated sea ice anomalies, clustered by construction around opposite phases of the ADP, and the lack of responses in the corresponding predicted values describes the limited predictability of these components of Antarctic sea ice variability in our model setup.…”

“…Accordingly, Antarctic sea ice has displayed modest historical trends in the early satellite era [9][10][11], as its variability was dominated by the seasonal component [12]. The more pronounced Antarctic sea ice extent anomalies observed since the 2000s, especially in the West Antarctic [13,14], have revitalized interest in interannual and decadal variability and the predictability of this critical component of the Earth system [15][16][17][18][19][20]. Even more so, the record minimum extents observed in 2022 and 2023, in concomitance with Southern Ocean subsurface warming, have been portrayed as the first evidence of a new state of Antarctic sea ice [21].…”

“…Even more so, the record minimum extents observed in 2022 and 2023, in concomitance with Southern Ocean subsurface warming, have been portrayed as the first evidence of a new state of Antarctic sea ice [21]. However, despite potential sources of predictability identified in the Pacific [18], Indian [22] and Atlantic sectors [23,24], decadal prediction of Antarctic sea ice remains a challenge for current coupled climate models [25,26].…”

Weakened western Indian Ocean dominance on Antarctic sea ice variability in a changing climate

“…Further, during the second half of the satellite era, the influence of the WTIO SST has weakened, with correspondingly decreased variability of the WTIO SST. Due to limited observations, we are unable to attribute the cause for the observed post-1999 weakening based on observations alone 43 , but the weakening in WTIO SST variability and the resultant decrease in the impact on austral spring Antarctic sea ice is consistent with what is expected from greenhouse warming, with a strong intermodel agreement on reduced WTIO SST variability. Our result suggests that with a reduced inter-annual influence from the Indian Ocean projected to continue, the melt of Antarctic sea ice could accelerate as the signal of the impact from greenhouse warming becomes stronger relative to decreased inter-annual variability.…”